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Water circulation, dissolved oxygen, and ammonia concentrations in fish-net cages Gormican, Stephen Joseph 1989

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Water c i r c u l a t i o n , d i s s o l v e d oxygen, and ammonia c o n c e n t r a t i o n s i n f i s h net-cages By STEPHEN JOSEPH GORMICAN B.Sc,  U n i v e r s i t y o f B r i t i s h Columbia, 1980  A THESIS SUBMITTED IN PARTIAL'FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTERS OF SCIENCE  in THE FACULTY OF GRADUATE STUDIES (Department  o f Zoology)  We accept t h i s t h e s i s as conforming to the r e q u i r e d standard  THE UNIVERSITY OF BRITISH COLUMBIA A p r i l 198 9 ©  Stephen Joseph Gormican, 1 9 8 9  In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may department or by  his or her  be granted by the head of  my  representatives. It is understood that copying or  publication of this thesis for financial gain shall not be allowed without my written permission.  Department The University of British Columbia Vancouver, Canada  DE-6 (2/88) (  ii Abstract  Fish Columbia  farming  in  the  i s relatively  new,  protected  waters  of  but has undergone  British  a phenomenal  growth i n t h e l a s t t e n y e a r s . L i t t l e i n v e s t i g a t i o n has been reported  with  employed  i n growing salmon a t f i s h farms. In p a r t i c u l a r , t h e  role  water  of  examined  in  respect  to  conditions  quality  and  water  relation  to  local  w i t h i n the  exchange  net-cages  has  not  mariculture  been  husbandry  p r a c t i c e s and hydrography. The f i r s t p a r t of t h i s study compared water q u a l i t y  and  water f l o w i n two l o c a t i o n s , one i n J e r v i s I n l e t w i t h a deep entrance  sill  shallow  and the- o t h e r  entrance  occurred  between  sill. the  i n Sechelt  Marked two  Inlet  variations  sites  as  a  in  which  has  a  hydrography  result  of  the  d i f f e r e n c e s i n s i l l depth. An i n t e r n a l wave g e n e r a t e d at t h e Sechelt  Inlet  stratification  sill and  caused  hence water  daily  fluctuations  in  p r o p e r t i e s w i t h i n the net-  cages. No such v a r i a t i o n s were observed at the J e r v i s  Inlet  site. In  the  second p a r t  of t h i s  study,  water f l o w was_ measured i n v a r i o u s raft  of 2 4 net-cages. Generally,  the r a f t ,  water f l o w was  water  quality  and  l o c a t i o n s i n and near a i t was  diminished  found t h a t  i n t h o s e cages  within located  downstream o f t h e predominate f l o w d i r e c t i o n . However, l o c a l topography  was  thought t o have caused  marked v a r i a t i o n  in  water  quality  and water  exchange p a t t e r n s  i n two o f t h e  cages. Ammonia  concentrations  were  not observed  to  exceed  r e p o r t e d s u b l e t h a l c o n c e n t r a t i o n s a t any t i m e , over a 25 h p e r i o d , a t any o f t h e depths sampled, w i t h i n t h e n e t - c a g e s . Dissolved  oxygen  concentrations  d i d , a t some  depths  and  t i m e s , approach v a l u e s a t which some s t r e s s may be f e l t due t o low oxygen. Linear  regressions  between  water  quality  and  water  speed were not found t o be s i g n i f i c a n t i n most c a s e s . The coefficient  o f d e t e r m i n a t i o n s were  low, i n d i c a t i n g  that  c u r r e n t speed accounted f o r l e s s t h a n 27% o f t h e v a r i a t i o n i n water q u a l i t y .  iv  Table o f Contents Abstract Table o f c o n t e n t s L i s t of tables  ..i i iv v  List of figures  vi  Acknowledgements  viii  General I n t r o d u c t i o n  1  Chapter 1  Water q u a l i t y and water exchange a t two f i s h farms l o c a t e d i n J e r v i s and S e c h e l t I n l e t s , B.C  7  Introduction  7  M a t e r i a l s and Methods  10  R e s u l t s and D i s c u s s i o n  18  Conclusions  38  Chapter 2  Net-cage f i s h f a r m i n g i n B r i t i s h Columbia: A case study o f water c i r c u l a t i o n and water q u a l i t y i n a l a r g e r a f t o f cages.....  39  Introduction  39  M a t e r i a l s and Methods  40  Results  42  Discussion,  50  Conclusions  .55  General Discussion  56  Bibliography  59  L i s t of Tables 1. Comparisons o f t o t a l ammonia i n s i d e cages a t t h e JER and SEC s i t e s . Data were p o o l e d f o r each depth and l o c a t i o n u s i n g v a l u e s c o l l e c t e d over t h e 25 h s a m p l i n g programs. Order o f means i s as p r e s e n t e d under t h e Comparison heading. (SD=standard d e v i a t i o n , df=degrees o f freedom.... 23 2. Comparisons o f DO, t o t a l ammonia, and c u r r e n t speed i n s i d e and o u t s i d e net-cages a t t h e JER and SEC s i t e s . Data were p o o l e d f o r each depth and l o c a t i o n u s i n g v a l u e s c o l l e c t e d over t h e 25 h s a m p l i n g program. (SD=standard d e v i a t i o n , df=degrees o f freedom) 26 3. Comparisons o f DO and t o t a l ammonia i n s i d e cages 23 and 15 a t t h e JER s i t e . Data were p o o l e d f o r each depth and l o c a t i o n u s i n g v a l u e s c o l l e c t e d over t h e 25 h s a m p l i n g program. (SD=standard d e v i a t i o n , df=degrees o f freedom)..48  vi  L i s t of Figures L o c a t i o n s o f study s i t e s . The J e r v i s I n l e t s i t e i s d e s i g n a t e d by a (1) and t h e S e c h e l t I n l e t s i t e by a (2) .. >  11  P l a n views o f t h e , A) J e r v i s I n l e t (JER) and B) S e c h e l t I n l e t s i t e s . S t a t i o n s a t which water q u a l i t y samples were c o l l e c t e d and p r o f i l i n g performed, a r e d e s i g n a t e d by (O)• C u r r e n t meters were d e p l o y e d a t l o c a t i o n s i n d i c a t e d by (A) . See t e x t f o r d e t a i l s o f deployments and s a m p l i n g p r o t o c o l 12 P l o t s o f A) temperature and B) Sigma-t ( d e n s i t y - see t e x t f o r explanation) versus time f o r the i n d i c a t e d depths sampled a t t h e J e r v i s I n l e t farm s i t e . Temperature d a t a was c o l l e c t e d h o u r l y u s i n g t h e Hydrolabs instrument at the s t a t i o n outside of cage 23. Sigma-t d a t a was c o l l e c t e d u s i n g I n t e r o c e a n S4 c u r r e n t meters suspended s i m u l t a n e o u s l y o u t s i d e cage 19 ( F i g u r e 2) .19 P l o t s o f A) temperature and B) Sigma-t ( d e n s i t y ) v e r s u s t i m e f o r t h e i n d i c a t e d depths a t t h e S e c h e l t I n l e t farm s i t e . Data was c o l l e c t e d u s i n g t h e H y d r o l a b s i n s t r u m e n t t o p r o f i l e t h e water column i n s i d e cage 6. Each p o i n t i s a s i n g l e sample - see t e x t f o r e r r o r estimation 20 P l o t s o f A) ammonia v e r s u s time and B) c u r r e n t speed f o r t h e i n d i c a t e d s a m p l i n g depths a t t h e J e r v i s I n l e t s i t e . S t i p l e d a r e a i n d i c a t e s time o f f e e d i n g . Each ammonia d a t a p o i n t i s a s i n g l e sample - see t e x t f o r e r r o r e s t i m a t i o n . C u r r e n t speeds a r e h o u r l y averages o f 6 two-minute s a m p l i n g e p i s o d e s 21 P l o t s o f A) ammonia v e r s u s t i m e and B) c u r r e n t speed f o r t h e i n d i c a t e d s a m p l i n g depths a t t h e S e c h e l t I n l e t s i t e . S t i p l e d a r e a i n d i c a t e s t i m e o f f e e d i n g . Each ammonia d a t a p o i n t i s a s i n g l e sample - see t e x t f o r e r r o r e s t i m a t i o n . C u r r e n t speeds a r e h o u r l y averages of 6 s a m p l i n g e p i s o d e s 24 S c a t t e r diagram o f t o t a l ammonia v e r s u s c u r r e n t speed f o r d a t a c o l l e c t e d a t mid-cage depth (6 m) o f cage 23 at t h e J e r v i s I n l e t s i t e . The l i n e i s t h e l e a s t squares regression l i n e with c o e f f i c i e n t of determination (r^) i n d i c a t e d . A t - s t a t i s t i c was used t o t e s t s i g n i f i c a n c e , (p) 28  vii  8.  S c a t t e r d i a g r a m o f t o t a l ammonia v e r s u s c u r r e n t s p e e d f o r d a t a c o l l e c t e d a t t h e m i d - c a g e d e p t h (2 m) i n c a g e 6 a t t h e S e c h e l t I n l e t s i t e . The l i n e i s t h e l e a s t squares r e g r e s s i o n l i n e with c o e f f i c i e n t of d e t e r m i n a t i o n (r^) i n d i c a t e d . A t - s t a t i s t i c was u s e d t o t e s t s i g n i f i c a n c e (p) , 29  9.  P l o t s o f d i s s o l v e d oxygen v e r s u s t i m e f o r t h e i n d i c a t e d sampling depths at the J e r v i s I n l e t s i t e . Each d a t a p o i n t i s a s i n g l e sample - see t e x t f o r e r r o r estimation 31  10.  P l o t s o f d i s s o l v e d oxygen v e r s u s t i m e f o r t h e i n d i c a t e d sampling depths at the S e c h e l t I n l e t s i t e . Each d a t a p o i n t i s a s i n g l e sample - see t e x t f o r e r r o r e s t i m a t i o n (p) . . . . ..33  11.  S c a t t e r d i a g r a m o f d i s s o v e d oxygen v e r s u s c u r r e n t s p e e d f o r d a t a c o l l e c t e d a t m i d - c a g e d e p t h (6 m) o f c a g e 23 a t t h e J e r v i s I n l e t s i t e . The l i n e i s t h e l e a s t s q u a r e s r e g r e s s i o n l i n e w i t h c o e f f i c i e n t o f d e t e r m i n a t i o n (r^) i n d i c a t e d . A t - s t a t i s t i c was u s e d t o t e s t significance 34  12.  S c a t t e r d i a g r a m o f d i s s o l v e d oxygen v e r s u s c u r r e n t s p e e d f o r d a t a c o l l e c t e d a t t h e m i d - c a g e d e p t h (2 m) i n c a g e 6 a t t h e S e c h e l t I n l e t s i t e . The l i n e i s t h e l e a s t squares r e g r e s s i o n l i n e with c o e f f i c i e n t of d e t e r m i n a t i o n (r^) i n d i c a t e d . A t - s t a t i s t i c was u s e d t o test significance 35  13.  P l o t o f c u r r e n t speed v e r s u s depth f o r the p r o f i l e e x p e r i m e n t a t t h e J e r v i s I n l e t s i t e . E r r o r b a r s a r e one standard deviation ...43  14.  V e c t o r diagrams o f d a t a c o l l e c t e d at the i n d i c a t e d l o c a t i o n s i n and a r o u n d t h e r a f t o f n e t - c a g e s a t t h e J e r v i s I n l e t s i t e . D e p t h o f i n s t r u m e n t d e p l o y m e n t was 6 m f o r a d u r a t i o n o f 25 h . D a t a was c o l l e c t e d s i m u l t a n e o u s l y a t e a c h l o c a t i o n . The l e n g t h o f each v e c t o r i s p r o p o r t i o n a l to c u r r e n t speed, (1 d i v i s i o n = l c m / s e c ) , w h i l e t h e o r i e n t a t i o n i n d i c a t e s f l o w d i r e c t i o n . F i g u r e s above d i a g r a m s a r e a v e r a g e s p e e d and ( d i r e c t i o n ) f o r t h e 25 h sampling p e r i o d i l l u s t r a t e d i n each v e c t o r diagram...45  15.  C o m p a r i s o n s o f d i s s o l v e d oxygen c o n c e n t r a t i o n s v e r s u s t i m e f o r t h e i n d i c a t e d d e p t h s i n c a g e 23 (O) and c a g e 15 (•) a t t h e J e r v i s I n l e t s i t e . . . 47  16.  C o m p a r i s o n s o f ammonia c o n c e n t r a t i o n s v e r s u s t i m e c a g e s 23 & 15 a t t h e J e r v i s I n l e t s i t e . D e p t h o f s a m p l i n g was A) 0.5 m and B) 6 m  i  for 49  Acknowledgements I would l i k e t o thank a l l my committee members f o r t h e i r i n v a l u a b l e a d v i c e throughout t h i s p r o j e c t . S p e c i a l thanks goes t o Dr. S. Pond f o r a s s i s t a n c e i n t h e f i e l d under l e s s t h a n i d e a l c o n d i t i o n s . Mr. E. B l a c k a l s o p l a y e d an i n v a l u a b l e r o l e i n o b t a i n i n g equipment and f u n d i n g . My s u p e r v i s o r , Dr. A.G. Lewis p r o v i d e d support throughout t h i s project. F i e l d work would not have been p o s s i b l e w i t h o u t t h e e x t r e m e l y competent Mr. Jay McNee, and so t o him goes a special word of gratitude. Anna Metaxas provided encouragement and words o f wisdom - always. The S k e i f a m i l y , a t S e c h e l t Salmon Farms L t d . , were v e r y k i n d i n p r o v i d i n g accommodation and access t o t h e i r farm. I thank Dora G l o v e r a t t h e Sunshine Coast A q u a c u l t u r e Association f o r everything she d i d t o a i d my research. R o d e r i c k F a r q u a r s o n and h i s f a m i l y h e l p e d t o make t h e 1988 f i e l d season b e a r a b l e . A l l t h e p e o p l e a t Hardy Sea Farms w i t h whom I had c o n t a c t were v e r y h e l p f u l . The N a t i o n a l Research C o u n c i l (NRC) p r o v i d e d me w i t h two I n d u s t r i a l Research A s s i s t a n t s h i p s (IRAP-H's) t o h e l p keep me s h e l t e r e d and f e d over t h e two summers o f my program. The Department o f Zoology provided teaching a s s i s t a n t s h i p s f o r which I am e x t r e m e l y g r a t e f u l , not j u s t f o r t h e f i n a n c i a l b e n e f i t s , but a l s o f o r t h e o p p o r t u n i t y t o g a i n an a p p r e c i a t i o n o f t h e t e a c h i n g s k i l l s n e c e s s a r y f o r any academic p u r s u i t , which a r e so l o s t i n t o d a y ' s p u b l i s h or p e r i s h a t t i t u d e . L a s t but not l e a s t , I thank Maureen Mann, f o r h e r p a t i e n c e and support d u r i n g some v e r y t r y i n g t i m e s .  1 General I n t r o d u c t i o n  Salmon f a r m i n g  i n net-cages  i n the  c o a s t a l waters  B r i t i s h Columbia i s a young i n d u s t r y . Cage f a r m i n g has p r a c t i c e d i n A s i a and  o t h e r p a r t s o f the w o r l d  1984)  however, l o c a l p r o l i f e r a t i o n has  within  the  last  10-15  report  that  eight  1985.  By  salmon  1988,  farms produced  125  tonnes by  1989)  projects  1995  and  107  an  (Black and  and  tonnes  annual  the  occurred  Carswell  f i s h farms produced over  (Anonymous,  Association  Black  been  f o r decades  (Beveridge,  years.  of  of  (1986)  salmon i n  6,500 tonnes o f  B.C.  Salmon  production  of  Farmers  over  C a r s w e l l , 1986). R a p i d  15,000  growth  of  the i n d u s t r y has a l l o w e d l i t t l e time t o assess the e f f e c t of t h i s i n d u s t r y on the environment, nor has t h e r e been time t o research  husbandry  practices  for  local  conditions  and  cultured species. M a r i c u l t u r e i s known t o have a n e g a t i v e waters  in  which  oxygen (DO)  it  is  located  c o n c e n t r a t i o n s and  by  impact on  lowering  the  dissolved  i n c r e a s i n g ambient n u t r i e n t  c o n c e n t r a t i o n s . In Japan, DO c o n c e n t r a t i o n s were observed have been lowered stocked In  Usui  despite  at  by  as much as  0.5  a d e n s i t y o f 22 kg/m^  Bay,  Japan,  tidal  because  DO  limits.  Oxygen  mg/L  by  concentrations  of  3-4  were  concentrations  cage  (Rosenthal et a l . , 1988).  s t o c k i n g d e n s i t i e s had  currents  a single  to  knots falling  were  t o be  reduced  (=154-206 cm/sec) below  reported  critical to  vary  markedly, w i t h lowest v a l u e s r e p o r t e d t o occur d u r i n g s l a c k  tides  and f e e d i n g p e r i o d s .  worse  as waste  feed  and  Over time  the s i t u a t i o n  feces  increased  the  in  net-cages  must  became  biological  oxygen demand. Ammonia  concentrations  also  be  c o n s i d e r e d due t o p o t e n t i a l t o x i c i t y . Ammonia i n t h e marine environment may e x i s t i n two forms, u n - i o n i z e d ammonia ( N H 3 ) or ammonium i o n (NH^ ) . T o t a l ammonia, t h e sum o f t h e s e two 4-  forms  (NH3  +  NH4 ") 4  ,  will  be  referred  to  as  ammonia  throughout t h i s paper. The p r o p o r t i o n o f u n - i o n i z e d ammonia existing  in  temperature,  the  environment  and s a l i n i t y  marine- environment, NH4  , .'^and may  (Emerson  protein  excrete  ammonia  catabolism.  of  In the  percent  of  to  total  as  the  major  R a n d a l l and Wright  end-product  of  (1987) reviewed t h e  and e x c r e t i o n i n f i s h  and  t h a t c a . 80% o f n i t r o g e n e x c r e t i o n i s i n t h e form  ammonia.  excretion,  The  gills  are  however t h e e x a c t  the  major  site  mechanism o f t h i s  of  the  gills  ammonium i o n (NH4 ) +  by  simple  diffusion  ammonia  process i s  u n c l e a r . I t i s b e l i e v e d t h a t u n - i o n i z e d ammonia (NH3) across  pH,  (Bower and B i d w e l l , 1978) .  mechanisms o f ammonia f o r m a t i o n concluded  upon  e t a l . , 1975).  f o r 0.01. t o 15  ammonia' c o n c e n t r a t i o n s p r e s e n t Fish  dependent  N H 3 i s q u i c k l y converted  excreted  account  is  passes  processes,  while  e x c r e t i o n r e l i e s upon some s o r t o f i o n  exchange p r o c e s s . The t o x i c i t y o f u n - i o n i z e d ammonia t o f i s h i s a r e s u l t of a r e v e r s a l of the i n t e r n a l / e x t e r n a l gradient which a l l o w s NH3 t o r e - e n t e r t h e f i s h a c r o s s t h e g i l l s .  3 It  i s a w e l l documented f a c t t h a t ammonia, i f a l l o w e d  t o b u i l d up i n t h e r e a r i n g w a t e r s , may l e a d t o r e d u c t i o n s i n stamina,  growth  rate,  and  resistance  to  disease  (Burrows, 1964, H i l l a b y and R a n d a l l , 1979 and A l a b a s t e r and Lloyd,  1982).  These  authors  also  agree  that  sublethal  e f f e c t s o f ammonia may be i n d u c e d by l o n g - t e r m exposure t o concentrations  >0.025 mg NH3/L ( = 1. 8 (Xmol/L) .  of  The  m a j o r i t y o f t h e s e s t u d i e s have been conducted i n f r e s h w a t e r systems  i n which  water  i s at  least  partially  recycled,  t h e r e b y a l l o w i n g a b u i l d u p o f ammonia. Information fish al.  farms (1985)  cages  report be  Conversely,  from  times  higher  (1986)  identical  active  and  than  at  inactive  marine  1987) . E v r i k e t  ammonia c o n c e n t r a t i o n s  virtually  from  resulting  (Gowen and Bradbury,  that  8-9  levels  B l a c k and C a r s w e l l  were  downstream  ammonia  i s sparse  may  levels  on  around n e t -  normal  report  that  similar fish  levels. ammonia  distances  farms.  Weston  (1986) m o d e l l e d t h e impact t h a t a t h e o r e t i c a l 250 tonne farm,  located  i n t h e Puget  Sound a r e a , would  environment.  He  concentration  o f 0.02 mg/L as w e l l  0.3 mg/L (198 6)  predicted  i n t h e water model  a  rise  in  have  total  to  on t h e ammonia  as a d e c r e a s e i n DO o f  p a s s i n g through the s i t e .  i s applicable  fish  the  waters  and  Weston's culture  t e c h n i q u e s used i n B.C. w a t e r s ; however i t c o u l d be improved with the a d d i t i o n of e m p i r i c a l data c o l l e c t e d S u c c e s s f u l net-cage  fish  farming r e l i e s  locally. upon t h e f l o w  o f water t h r o u g h t h e cage w a l l s t o m a i n t a i n water  quality.  4  (For  t h e purposes  defined flow  of t h i s  study,  water  quality  will  i n terms o f DO and ammonia c o n c e n t r a t i o n s . )  through  factors.  net-cages  Inoue  may  (1972)  be  limited  indicated  downstream, i n a s e r i e s o f t h r e e t h e predominant c u r r e n t  that  by  a  the  be  Water  number o f third  cage  cages o r i e n t e d p a r a l l e l t o  f l o w , may e x p e r i e n c e o n e - t h i r d  water exchange t h a n t h e most upstream cage. F o u l i n g  less  of the  n e t t i n g by mussels and a l g a e may reduce water exchange by as much as 80% reported  (Wee, 1979 and Inoue, 1972) . Wee  that  increased  time  of  (1979)  submergence  also  increases  f o u l i n g , b u t t h a t t h e r a t e v a r i e d w i t h t h e seasons, and l i f e history  of  the  fouling  organisms.  Kennedy e t a l . (1977)  found t h a t f i s h deaths r e s u l t e d when DO c o n c e n t r a t i o n s to  4.0 mg/L  i n a cage h e a v i l y  s e s s i l e marine organisms, p l u s detritus".  After  net  fouled  with  fell  "a m i x t u r e o f  l i v i n g and dead p l a n k t o n  replacement,  DO  levels  rose  and to  8.25 mg/L i n t h e p r e v i o u s l y f o u l e d cage. Water q u a l i t y may v a r y  over a 24 hour p e r i o d .  Ammonia  e x c r e t i o n e x h i b i t s a s t r o n g d i u r n a l p e r i o d i c i t y (McLean and Fraser,  1974 and B r e t t  occurring before  and d u r i n g  night  1975) w i t h  dawn and h i g h e s t v a l u e s  onset o f f e e d i n g . to,  and Z a l a ,  Respiration rates  feeding,  lowest  values  about 4 h a f t e r t h e  are highest  w i t h the lowest r a t e s  just prior  o c c u r r i n g at  ( B r e t t and Z a l a , 1975). L o c a l waters a r e s u b j e c t t o 4  s l a c k t i d e o c c u r r e n c e s i n a 25 h p e r i o d ,  which may  e x a c e r b a t e ammonia b u i l d u p and DO d e p l e t i o n .  further  5 C l e a r l y t h e r e i s a need the  f o r a better understanding of  i n t e r a c t i o n between t h e environment  practiced reared,  in British  husbandry  Columbia.  practices  and m a r i c u l t u r e as  The b i o l o g y  employed,  of the species  and hydrography a r e  unique t o l o c a l w a t e r s . The problems  seen i n Japan may not  a r i s e l o c a l l y a s ' o u r i n l e t s a r e much deeper than t h e I n l a n d Sea o f Japan. C o n v e r s e l y , s h a l l o w e n t r a n c e s i l l s t o many o f our  inlets  ( P i c k a r d , 1975) may r e s t r i c t  water  exchange  or  m i x i n g p r o c e s s e s t o t h e p o i n t where near s u r f a c e w a t e r s a r e rendered u n s u i t a b l e f o r the p r a c t i c e of m a r i c u l t u r e . The experiments d i s c u s s e d i n t h i s t h e s i s were d e s i g n e d to  i n v e s t i g a t e t h e c o n d i t i o n o f water q u a l i t y  cages  located  i n the  waters  of  British  i n f i s h netColumbia.  In  Chapter 1, a comparison i s made o f water q u a l i t y i n two farm sites,  one l o c a t e d  i n Jervis  Inlet  which p o s s e s s e s a deep  sill,  and t h e o t h e r i n S e c h e l t  sill.  I t was h y p o t h e s i z e d t h a t t h e presence o f t h e s h a l l o w e r  entrance  sill  would  result  Inlet  •in  which  has a s h a l l o w  marked  variation  in  temperature and DO p r o f i l e s , r e l a t i v e t o t h e J e r v i s s i t e . As the  flood t i d e progresses across the s i l l ,  is  formed  which  entrains  waters  below  a turbulent j e t the s i l l  depth  ( L a z i e r , 1963). These below s u r f a c e waters may r e a c h a n o x i c c o n c e n t r a t i o n s , and hence c o n d i t i o n s i n t h e r e s u l t i n g waters  may  be  deleterious  reviewed l i t e r a t u r e , 25 h p e r i o d dissolved  to fish  health.  Based  on t h e  i t was a l s o h y p o t h e s i z e d t h a t ,  (one t i d a l c y c l e ) , ammonia c o n c e n t r a t i o n s oxygen  concentrations  would  reach  mixed  over a and/or  sublethal  6 thresholds. current  Also  speed  examined  and  increased current  water  was  the  quality.  relationship It  was  is directly In detail This  2  this  respect  to within  Weston's  of  was  (1986)  stated,  ( [ N H 3 ]  Inlet  site  was  site  water  flow  &  [  O  2  ]  )  examined  in  properties.  o f 24 c a g e s a n d i t was d e s i r e d t o  Inoue's  (1972)  i f they applied t o l o c a l site  that  exchange.  the Jervis  confirmation  determine at  r e l a t e d t o water  farm i s a l a r g e r a f t  gain  Formally  p o s t u l a t e d that water q u a l i t y  Chapter with  believed  s p e e d w o u l d f l u s h t h e n e t - c a g e s o f ammonia  and w o u l d a l s o r e p l e n i s h DO c o n c e n t r a t i o n s . t h i s hypothesis  between  260 t o n n e s ,  hypothetical  observations  and  c o n d i t i o n s . The  which farm  compares  biomass  biomass  closely  of  to  to  250 t o n n e s .  Thus, v e r i f i c a t i o n o f h i s h y p o t h e s e s r e g a r d i n g t h e i m p a c t o f salmon  farming  hypothesized  on  that  the environment water  located  downstream  relative  t o t h o s e cages  hypothesized predominant depth across that  any  of  flow the  would  be  t o be l o w e r i n c a g e s  Water  Water exchange  w o u l d be e q u a l  of current  made.  flow  I t was  i n cages direction  quality  was  also  l o c a t e d downstream o f t h e  one n e t - c a g e was e x a m i n e d .  reductions  be  diminished  predominant  upstream.  flow d i r e c t i o n .  could  speed  as a f u n c t i o n o f  I t was inside  oyer t h e depth o f t h e cage.  hypothesized the net-cage  7  Chapter  1:  Water quality and water exchange at two f i s h farms located in Jervis and Sechelt I n l e t s , B.C. Introduction  The primary source of DO to a net-cage i s through water exchange with the surrounding environment (atmospheric input is  too  slow  and  the  necessary  contained within a net-cage  phytoplankton  i n s u f f i c i e n t ) . Any  biomass  decrease in  water exchange i s . o f utmost concern to the f i s h farmer. K i l s (1979) estimated that oxygen input through the surface wind  and  wave  action)  and  phytoplankton  (by  photosynthetic  a c t i v i t y , can supply only 0.5% of t o t a l oxygen demand. K i l s (1979) however, assumed stocking densities  of 20-25  kg/m^  and, although not e x p l i c i t l y stated, based oxygen production values on a much lower phytoplankton standing stock than i s t y p i c a l l y observed for l o c a l P a c i f i c waters. Assuming spring concentrations of n i t r a t e i n l o c a l waters to be 20 (imol/L, a nitrogen  to  quotient  of  carbon 1.5  ratio  of  10,  (Williams, 1979),  and  a photosynthetic  yields  a  potential  increase of 4.2 mg O2/L under, ideal conditions. If even onequarter  of  phytoplankton  this would  theoretical contribute  standing a  stock  significant  existed, amount  of  oxygen to the waters. Conversely, such a bloom, upon death of the phytoplankton and subsequent  bacterial  respiration,  would cause a much greater lowering of oxygen concentration due to the rapid growth kinetics of b a c t e r i a . Doubling times  8 f o r b a c t e r i a are i n t h e o r d e r o f hours whereas p h y t o p l a n k t o n typically so,  double  oxygen  once p e r  day  i n c r e a s e s would  d e c r e a s e s . Consequently,  (Parsons e t a l . , 1984a)  occur  fish  much  kills  less  may  rapidly  result  from  and than  anoxia  caused by b a c t e r i a l r e s p i r a t i o n o f a f t e r a bloom. Davis f o r marine  (1975) r e v i e w e d t h e l i t e r a t u r e on DO salmonids and c o n c l u d e d t h a t >9.0  requirements  mg O2/L  assures  a h i g h l e v e l o f s a f e t y f o r most o f t h e f i s h p o p u l a t i o n w i t h few members e x h i b i t i n g symptoms o f low oxygen. At t h e mg O2/L,  lower c r i t e r i o n o f 6.43 the  average  member  of  a  symptoms o f oxygen d i s t r e s s if  exposure  to t h i s  more than a  Davis  fish  population  concentrations  exhibit  i s involved  i s allowed to continue f o r  phytoplankton to  the  blooms point  (Holeton, 1979). However, Weitkamp d i s e a s e (GBD)  occurrences GBD  will  few.hours.  Occasional  gas bubble  (1975). suggests t h a t  and t h a t some r i s k  l e v e l of DO  next  o f GBD  due  may  raise  oxygen  of  supersaturation  and Katz  (1980) r e v i e w e d  i n f i s h , and found t h a t no t o oxygen a l o n e had  natural  been r e p o r t e d .  u s u a l l y r e s u l t s from an i n c r e a s e i n t o t a l d i s s o l v e d  pressure  (TGP)  most o f t e n caused by s u p e r s a t u r a t i o n o f water  w i t h n i t r o g e n . While c o n c u r r e n t h i g h oxygen l e v e l s may t o m i t i g a t e t h e e f f e c t s o f GBD, supersaturated  dissipation.  exchange  Ammonia  to  i t s rapid  (Parsons et a l . ,  i s the  serve  o c e a n i c waters r a r e l y become  i n n i t r o g e n due  i n t o the n i t r o g e n c y c l e Water  gas  only  uptake  bulk by  incorporation  1984a). method  of  ammonia  phytoplankton  and  9 transformation accounts  by  bacteria  f o r only  a  to n i t r i t e  small  portion  and then due  to  nitrate,  the  large  d i f f e r e n c e s i n biomass w i t h i n a n e t - c a g e . This levels  study  inside  was  and o u t s i d e  measuring c u r r e n t cage  sampling  fish  health.  This  performed  while  and ammonia simultaneously  a 25 h p e r i o d . as  a  (The o u t s i d e -  control) .  Secondly,  would  i t was  This  was t o  correlate provide  an in  t o see i f t h e s e  linearly  t o water  indication  hydrographic  conditions  relationships  i n two l o c a t i o n s - J e r v i s  sill  DO  i f DO.and ammonia l e v e l s became d e l e t e r i o u s  q u a l i t y ' parameters rate.  t o monitor  net-cages  speed over  was  determine f i r s t , to  designed  exchange  of the role  determining  and S e c h e l t I n l e t w i t h a s h a l l o w  water  water  Inlet  sill.  with  of  quality a deep  10 M a t e r i a l s and Methods The Figure  locations  o f t h e study  1. The J e r v i s  l o c a t e d near  Inlet  a deep s i l l  sites  site  are. i l l u s t r a t e d i n  (referred  t o as JER) i s  (385 m) . The S e c h e l t  inlet  site  ( d e s i g n a t e d as SEC) i s l o c a t e d a p p r o x i m a t e l y 8 km s o u t h o f a shallow s i l l . h i g h water the  sites  between  The SEC e n t r a n c e s i l l  (Pickard, and cages  the s i t e s ,  has a depth o f 14 m a t  1975). F i g u r e 2 shows a p l a n view o f used  i n this  t h e JER  s t u d y . Cage s i z e  location  employed  varied  cages  of  15X15X15 m ( l e n g t h X w i d t h X d e p t h ) , whereas 12X12X5 m n e t cages were used  a t t h e SEC s i t e .  Walkways a t b o t h  surrounded each net-cage, w i t h t h e c e n t r a l walkway on  the long  remaining under did  axis  of the raft)  t h r e e walkways,  conditions  sites,  (oriented  c a . 2 m i n w i d t h , and t h e  c a . 1 m wide.  of high current  flow,  T h e r e f o r e , except a d j a c e n t net-cages  not make c o n t a c t . E s t i m a t e d t o t a l biomass a t t h e JER s i t e was 260,000 kg  of  primarily  contained was  0.  i n 24 cages.  4.3 kg/m  biomass kisutch  Oncorhynchus  at  3  tshawytscha  Stocking density  (chinook  i n t h e study  (9843 c h i n o o k , average weight  t h e SEC  farm  was  (coho salmon) and  0.  salmon)  1.4 k g ) . T o t a l  c a . 156,000 kg, tshawytscha  cage  primarily  contained i n  28 cages. The net-cage used i n t h i s study was s t o c k e d w i t h 4737, 1.1 kg coho a t a d e n s i t y o f 7.2 kg/m . 3  F i g u r e 1. L o c a t i o n s o f study s i t e s . The J e r v i s I n l e t s i t e i s d e s i g n a t e d by a (1) and the S e c h e l t I n l e t s i t e by a ( 2 ) .  I24°00'  .123° 4 0  12  Figure 2. Plan views of the, A) Jervis Inlet (JER) and B) Sechelt Inlet s i t e s . Stations at which water quality samples were c o l l e c t e d and.profiling performed, are designated by ( Q ) . Current meters were deployed at- locations indicated by ( ) . See text for d e t a i l s of depths of deployments and sampling p r o t o c o l .  13  JER  30 m  cage 2 3 ^ Q  A  OUT  N  A  A  y cage 6  A 0  15  A  L  cage 2  ycage  o  UT S  cage 10  14 Sampling was c a r r i e d out i n J u l y - A u g u s t i n 1987 (SEC) and  1988  (JER). D u r i n g  these  months  temperatures  reached  t h e i r annual peak and t h e f i s h were e x p e c t e d t o r e a c h t h e i r highest metabolic rate. A Hydrolabs® the  water  dissolved  Surveyor® I I probe  column oxygen.  was used  f o r temperature,  to profile  salinity,  pH,  Hydrolabs® c l a i m s a c a l i b r a t e d  and  accuracy  o f ±0.05°C, 0.2 p p t , and 0.2 mg/L f o r T, S, and DO, respectively. after  each  remained  Calibration field  use  within  conductivity  ±2%  within  of the instrument  indicted of  ±3%.  that  their  temperature  initial  However,  b e f o r e and and pH  values,  the dissolved  sensor d r i f t e d by a maximum o f -10%. In situ  and  oxygen  DO measurements  were always performed w i t h i n a 25 h p e r i o d and t h e r e f o r e t h e instrument d r i f t error  would presumably  account  d u r i n g the sampling i n t e r v a l .  f o r l e s s t h a n 1%  Moreover,  differences,  not a b s o l u t e v a l u e s were i m p o r t a n t i n t h i s study, and so, DO r e a d i n g s were c o n s i d e r e d a c c e p t a b l e . Samples situ  u s i n g e i t h e r a diaphragm  Collected or  f o r ammonia d e t e r m i n a t i o n were  samples  filtered  collected  pump o r a 2 L N i s k i n  were e i t h e r p r o c e s s e d on s i t e  t h r o u g h precombusted  f i l t e r s and f r o z e n f o r subsequent  in  bottle.  (1987-SEC)  Whatman GF/F g l a s s laboratory analysis  fiber (1988-  JER). Ammonia d e t e r m i n a t i o n s i n e i t h e r case f o l l o w e d methods outlined ammonia  i n Parsons to  et a l .  t h e ammonium  e x p r e s s e d as t o t a l  (1984b)  i o n . Values  which  converts a l l  reported  will  ammonia measured - t h e sum o f NH4  +  be and  15 NH3.  Tables  i n Bower and B i d w e l l  (1978) were c o n s u l t e d t o  determine  t h e p r o p o r t i o n o f u n - i o n i z e d ammonia p r e s e n t i n  the water  column g i v e n  than 5% o f t o t a l (NH3)  t h e in situ  ammonia e x i s t e d i n t h e u n - i o n i z e d ammonia  form i n any p a r t o f t h i s  study.  I n t e r o c e a n S4® c u r r e n t meters JER  site  whereas Aanderaa  used a t t h e SEC s i t e . Both recording  T, S, and pH. No more  (7) were employed a t t h e  RCM-4® c u r r e n t meters  instruments are i n t e r n a l l y  f o r T, S, p r e s s u r e and c u r r e n t  instrument  self-  speed/direction,  w i t h programmable sampling d u r a t i o n and frequency. a true vector-averaging  (4) were  The S4 i s  w i t h an a c c u r a c y  o f ±2%  o f the r e a d i n g f o r c u r r e n t speed and ±2.0 degrees d i r e c t i o n . Without and  c o r r e c t i o n s accuracy  ±0.2 °C  sigma-t. water  f o r temperature,  (Sigma-t  density  i s ±0.5-0.6 p p t f o r s a l i n i t y fora total  i s a shorthand  and i s d e f i n e d  notation  as d e n s i t y  1000.00, i t i s u s u a l t o omit t h e u n i t s 1986)).  e r r o r o f ±0.6 i n f o r expressing [kg/m ] 3  minus  (Pond and P i c k a r d ,  C o r r e c t i o n s were n o t made as a b s o l u t e v a l u e s  were  not r e q u i r e d and d i f f e r e n c e s between depths were much l a r g e r than is  the error. ±1 cm/sec  (temperature),  Claimed (speed),  accuracy ±5  fo.r t h e RCM-4  degrees  and ±0.025 mS/cm  instruments  (direction),  (conductivity).  ±0.05°C The  S4  c u r r e n t meters were programmed t o sample f o r 2 min every 10 min.  The RCM-4 i n s t r u m e n t s , were s e t t o sample once every 10  minutes. C u r r e n t meters were suspended s i m u l t a n e o u s l y i n s i d e and outside  net-cages  v i a a series  o f aluminum  poles,  Viny®  16 floats,  and p o l y p r o p y l e n e  instruments  rope.  I n a l l deployments, t h e  were p o s i t i o n e d 3-3.6 m from  adjacent  nets t o  ensure t h a t they d i d not become e n t a n g l e d i n t h e n e t s d u r i n g periods  o f h i g h c u r r e n t f l o w . Depths  w i t h each experiment concerned  a t t h e JER s i t e .  varied  Experiments  with d e t e c t i n g flow patterns across the s i t e  instruments function  conducted  o f deployment  deployed  o f depth  a t 6 m.  Determination  r e q u i r e d instruments  2, 5, and 8 m i n s i d e t h e net-cage  of flow  used as a  t o be deployed  at  and a t 2, 5, 8, and 11 m  o u t s i d e t h e cage. C u r r e n t meters were deployed a t 2 and 4 m only  a t t h e SEC  site.  The  locations  o f deployments i s  i l l u s t r a t e d i n F i g u r e 2. Sampling period  o f t h e water  column was performed  i n order t o include the f u l l  profiles  inside  tidal  and o u t s i d e t h e net-cages  over a 25 h  cycle.  Vertical  were t a k e n  once  every hour, w h i l e d i s c r e t e samples f o r ammonia d e t e r m i n a t i o n were c o l l e c t e d every 1.5 h a t t h e JER s i t e at  t h e SEC s i t e . A t b o t h  locations,  and every  samples were  1.0 h  collected  over a c o n t i n u o u s 25 h s a m p l i n g program. Ten  replicate  ammonia  a n a l y z e d t o determine Near  surface  ammonia freezing  showed  samples  the error with  a standard  process,  samples  a  were  collected  o f t h e sampling mean  of  and  protocol.  0.35u.mol/L . t o t a l  d e v i a t i o n o f 0.19. D u r i n g t h e  ammonium  concentrations  of  2, 4  and  8 umol/L were a l t e r e d by 2% o f t h e i r o r i g i n a l v a l u e s whereas s t a n d a r d s o f 1 |imol/L v a r i e d by 65%. The h i g h v a r i a b i l i t y a t low  concentrations, resulting  from  the freezing  process,  17 perhaps  accounts  f o r the  substantial  variation  of the  r e p l i c a t e samples. Data f o r each depth and l o c a t i o n were p o o l e d f o r each 25 h  sampling  period  i n order  ammonia l e v e l s , DO and c u r r e n t the  to  allow  (Perlman,  analysis determine  was  1986) d a t a  also  analysis  performed  i f a relationship  (using existed  parameters and water f l o w r a t e s .  of  speed i n s i d e and o u t s i d e o f  net-cages. A Student's t s t a t i s t i c  I STAT  comparisons  was computed  programs. |STAT  Regression  software)  between water  Differences  using  and  to  quality  regression  r e l a t i o n s h i p s were judged t o be s i g n i f i c a n t a t t h e 95% l e v e l (p<0.05).  18  R e s u l t s and  Discussion  The water column at the JER s i t e i s s t r o n g l y s t r a t i f i e d as  i n d i c a t e d by  b o t h the t e m p e r a t u r e and  ( F i g u r e 3) . At the SEC 25 h  sampling  stratification shallow the  sill,  density  divergences waves are  site,  period  passing  s t r a t i f i c a t i o n v a r i e s over  (Figure 4).  i s due  to  density structure  internal  The  periodicity  waves g e n e r a t e d  t h r o u g h the net-cages,  structure  by  causing  and  in  at  the  modifying  convergences  i n the upper l a y e r s o f water. As these generated t i d a l l y ,  the  a semi-diurnal  and  internal  periodicity  is  e v i d e n t i n the d e n s i t y and temperature p r o f i l e s . The  e x p e c t e d d a i l y p a t t e r n o f ammonia p r o d u c t i o n  peak l a t e i n the a f t e r n o o n by McLean and  Fraser  at 6 m at the JER ebb  at dawn.  in  ammonia was  during  periods  particular  an ebb  near dawn as  ( F i g u r e 5) w i t h peaks at 17:30  There was  no  clear pattern  ammonia c o n c e n t r a t i o n s ,  not of  morning,  reported  (1974) . T h i s p a t t e r n i s apparent  site  c u r r e n t speed and  and  is a  always preceded by, slower  water  speed  the  automatic  were  On  occur this  empty  and  t h u s , w h i l e f e e d i n g u s u a l l y commenced at 05:30 ( s u n r i s e ) , f e e d was  supplied u n t i l  s t a f f . The  f i s h may  an  increase  found t o  (Figure 5).  feeders  and  observed between i . e . an  or  only  08:00, upon the a r r i v a l of the  no  farm  have been c o n d i t i o n e d t o r e c e i v e f e e d at  05:30, and so, were induced  i n t o ammonia p r o d u c t i o n  by  19 F i g u r e .3. P l o t s o f A) t e m p e r a t u r e and B) S i g m a - t ( d e n s i t y see t e x t f o r e x p l a n a t i o n ) v e r s u s t i m e f o r t h e i n d i c a t e d depths sampled at the J e r v i s I n l e t farm s i t e . Temperature d a t a was c o l l e c t e d h o u r l y u s i n g t h e H y d r o l a b s instrument at t h e s t a t i o n o u t s i d e o f c a g e 2 3 . S i g m a - t d a t a was collected u s i n g I n t e r o c e a n S4 c u r r e n t meters suspended s i m u l t a n e o u s l y o u t s i d e c a g e 19 ( F i g u r e 2 ) . -  A • • 1 meter O——-O 6 m e t e r s A A 1 1 meters  24 22 O  20  o <D  LT  -•-i=k ' n  "18  D  i_  CD  16  CL  E  14 12  o- - o ^ o - o - •o- - o — o - o — o — o — o — o -A—A—A— —A—A—A—A— --AA  B  1.0 16:00  22:00  A  04:00  C)  -A—A—A-  10:00  16:00  30  25-  8 meters 5 meters 2 meters  D  £  20  in 15 +  10 16:00  +  22:00  .04:00  Time of day  10:00  +  1 6:00  20  Figure 4 . Plots of A) temperature and B) Sigma-t (density) versus time for the indicated depths at the Sechelt Inlet farm s i t e . Data c o l l e c t e d using the Hydrolabs instrument to p r o f i l e the water column inside cage 6 . Each point i s a single sample - see text for error estimation.  A  21  15-1  18:00  1 23:00  1 04:00  1 09:00  Time of day  :  1 14:00  1  19:00  21 F i g u r e 5. P l o t s o f A) ammonia v e r s u s time and B) c u r r e n t speed f o r t h e i n d i c a t e d sampling depths at the J e r v i s I n l e t s i t e . S t i p l e d area i n d i c a t e s time o f f e e d i n g . Each ammonia data p o i n t i s a s i n g l e sample - see. t e x t f o r e r r o r e s t i m a t i o n . Current speeds are h o u r l y averages o f 6 twominute sampling e p i s o d e s .  A  16:00  B  22:00  5-r  04:00  10:00  —  O o  ''  16:00 —  O 6 m  4--  CD  co \  E o  3-  TD CD CO CL CO  -•—>  c CD i_ k_  o  1 --  0 16:00  1 22:00  — • • — l  h-  04:00 Time of day  c  10:00  1 6:0.0  22 sunrise, sharp  o r by t h e n o i s e  drop  made by t h e empty  a t 10:00 then,  may  have  been  feeders.  The  the result  of  ammonia e x c r e t i o n r a t e f a l l i n g because o f i n s u f f i c i e n t  time  t o p r o c e s s t h e f e e d o f f e r e d a t 08:00. At  t h e JER s i t e ,  ammonia c o n c e n t r a t i o n s  not f o l l o w t h e e x p e c t e d p a t t e r n were s i g n i f i c a n t l y  ( F i g u r e 5 ) . Moreover,  surface  values  lower t h a n t h o s e a t 6 m (Table 1 ) . I t i s  suggested t h a t t h e uptake o f N H near  a t 0.5 m d i d  portion  by algae  + 4  o f t h e JER net-cage  l o w e r i n g o f ammonia c o n c e n t r a t i o n s  attached may  to the  cause t h e  r e l a t i v e t o t h o s e a t 6 m.  Furthermore, i t may be t h a t t h e s e 15 m deep cages, combined with  a lower  stocking  density,  allow  warmer t e m p e r a t u r e s near t h e s u r f a c e ,  the f i s h  t o escape  which would have t h e  e f f e c t o f c o n c e n t r a t i n g ammonia l e v e l s a t depth. E x p e c t e d ammonia c o n c e n t r a t i o n p a t t e r n s a t t h e SEC s i t e are  not apparent a t any o f t h e depths sampled  The  observed t r e n d i s o f i n c r e a s e d  25 h s a m p l i n g p e r i o d , decreased  (Figure  relationship  while  ammonia l e v e l s  current  6) . I t w i l l  (Figure  over t h e  speed appears t o have  be shown however, t h a t  i s not s t a t i s t i c a l l y  6) .  significant.  this  The o v e r a l l  t r e n d o f i n c r e a s i n g ammonia over t h e 25 h p e r i o d may be due to the sampling procedure Fraser  (1974)  noticeably  reported  i n rearing  removal o f some. f i s h .  disturbing  that ponds  the f i s h .  ammonia after  McLean and  concentrations  a disturbance  such  rose as  Table 1. Comparisons of t o t a l ammonia inside cages at the JER and SEC s i t e s . Data were pooled for each depth and location using values c o l l e c t e d over the 25 h sampling programs. Order of means i s as presented under the Comparison heading. (SD=standard deviation, df=degrees of freedom) Location  Comparison  JER  total ammonia (|imol/L)  SEC-  total ammonia (u.mol/L)  1st mean (SD)  2nd mean (SD)  t  t-test c a l c (df)  P  0.5 vs 6m  0.9 (1. 0)  3.5 (3. 0) 3.508 (34)  0 .001  0.5 vs 2m 0.5 vs 4m 2m vs 4m  3.5 (1.9) 3.5 (1. 9) .3.4 (2. 1)  3.4 (2. 1) 0.107 (32) 3.2 (1. 7) 0.580 (32) 3.2 (1. 7) 0.435 (32)  0 .915 0 .566 0 .666  24 Figure 6. Plots of A) ammonia versus time and B) current speed f o r the indicated sampling depths at the Sechelt Inlet s i t e . S t i p l e d area indicates time of feeding. Each ammonia data point i s a single sample - see text f o r error estimation. Current speeds are hourly averages of 6 sampling episodes.  A  10  CH  18:00  1 23:00  1  1  04:00 09:00 Time of day  1  1  14:00 1 9 : 0 0  25 There  were  no  significant  differences  found  among  ammonia samples c o l l e c t e d a t 0.5, 2, o r 4 m (Table 1) a t t h e SEC s i t e . employed  The h i g h e r s t o c k i n g d e n s i t y ,  and s h a l l o w e r cages  a t t h i s s i t e a r e thought t o c o n t r i b u t e t o t h e e q u a l  d i s t r i b u t i o n o f ammonia w i t h i n t h e n e t - c a g e . The only  JER s i t e  ones  to  6 m ammonia c o n c e n t r a t i o n s were a l s o t h e  show  significant  variation  between  samples  from i n s i d e and o u t s i d e o f t h e n e t cage  Current  meter  data  indicate  f l o w impinged on t h e cage  pooled  (Table 2 ) .  that  t h e predominant  current  sampled  a t t h e JER s i t e  (Figure  14, which i s d i s c u s s e d i n Chapter 2) from t h e o u t s i d e d u r i n g a large portion of the t i d a l  c y c l e , w h i l e t h e sampled  cage  at t h e SEC s i t e r e c e i v e d much o f i t s water t h r o u g h a d j a c e n t cages. The l o c a t i o n o f t h e SEC s i t e w i t h i n a s e m i - e n c l o s e d bay  ( F i g u r e 2) caused t h e f o r m a t i o n o f g y r e s w i t h i n t h e farm  which  changed  i n speed  Thus, because  and l o c a t i o n  the outside  over t h e t i d a l  sampling s t a t i o n  cycle.  was s u b j e c t t o  waters t h a t had passed t h r o u g h an u n c e r t a i n number o f o t h e r net-cages  i t was  considered  meaningless  as  a  control.  S u r f a c e ammonia samples c o l l e c t e d p e r i o d i c a l l y from near t h e shore averaged 0.3  to  0.8|lmol/L  2.9|imol/L.  These  (S.D.=0.7, n=13) and ranged samples  enrichment was not c o n f i n e d  indicated  t o the f i s h  that  cages.  from  ammonia  Background  ammonia c o n c e n t r a t i o n s a r e c o n s i d e r e d t o be <1.0 umol/L f o r l o c a l waters  (Dr. P . J . H a r r i s o n , DOUBC, p e r s . comm.).  Table 2. Comparisons o f DO, t o t a l ammonia, and c u r r e n t speed i n s i d e and o u t s i d e net-cages a t t h e JER and SEC s i t e s . Data were p o o l e d f o r each depth and l o c a t i o n u s i n g v a l u e s c o l l e c t e d over 25 h s a m p l i n g program. (SD=standard d e v i a t i o n , df=degrees o f freedom) Location  JER 21 J u l y , 1988  Depth (m) 1 6 11 . 0.5 6 6  0.5 SEC 6 August, 1 1987 • 2 3 4 0.5 2 4 2 4  Parameter  INSIDE mean (SD)  OUTSIDE mean (SD)  t  t-test c a l c (df)  p  9.5 (0. 8) 7.9 (0. 5) 6.5 (0. 2)  9.4 (0. 6) 0.2 94 (34) 8.3 (0. 5) 2.501 (34) 6.5 (0. 2) 0.381 (34)  0 . 771 0 . 017 0 .706  0.9 (1. 1) 4.4 (2. 6)  0.5 (0. 5) 1.272 (34) 1.7 (1. 6) 3.187 (26)  0 .212 0 .004  current 2.0 (1. 3) speed (cm/sec)  2.9 (2. 5) 3.838 (300)  <0 .001  DO (mg/L)  9.0 8.9 8.8 8.6 8.4  0 .167 0 .782 0 .570 •'0.887 0 .815  DO (mg/L). total ammonia (|imol/L)  9.1 9.0 8.8 8.6 8.3  total ammonia ((imol/L) current speed (cm/sec)  '  (0. 3) (0. 3) (0. 4) (0. 6) (0. 7)  (0. 3) (0. 2) (0. 4) (0. 5) (0. 6)  1.403 0.278 0 .572 0.143 0.236  (50) (50) (50) (50) (50)  3.7 (1. 8) 3.5 (2. 0) 3.1 (1. 8)  2.9 C l . 2) 1.486 (31) 3.7 (1. 8) 0.302 (32) 3.4 (1. 5) 0.436 (32)  0 . 147 0 .765 0 .666  8.3 (5. 4) 6.6 (3. 6)  7.2 (4. 4) 0.776 (48) 5.6 (3. 1) 1.042 (48)  0 .441 0 .303  CTl  Un-ionized  (NH3)  ammonia  (=0 . 008 mg N H 3 / L )  0.6|imol/l  levels  (1982)  exposure  t o be  basis.  toxic  Lethal  not are  regressions  significant  predicted  significantly  different  salmonids  levels  value  on  a  are reported  long-term  t o begin  at  ( A l a b a s t e r and L l o y d , 1982).  o f ammonia and c u r r e n t  at e i t h e r s i t e  i n the  ca.  r e p o r t e d by A l a b a s t e r and  to  c o n c e n t r a t i o n s o f 0.2 mg N H 3 / L Linear  at  at both l o c a t i o n s . This  i s w e l l below t h e 0.025 mg N H 3 / L Lloyd  peaked  speed were  ( F i g u r e s 7 & 8) . The  direction,  however  from  The i n t e r a c t i o n  zero.  they  slopes  are not of the  t i d a l c y c l e ( f o u r c u r r e n t r e v e r s a l s i n 25 h) and t h e d i u r n a l p e r i o d i c i t y o f ammonia p r o d u c t i o n a very too  complex r e l a t i o n s h i p ,  simplistic.  At  and u t i l i z a t i o n make t h i s  and perhaps a l i n e a r model i s  t h e SEC  site,  the influence  of the  i n t e r n a l t i d e , may have added c o n s i d e r a b l e n o i s e t o t h e d a t a by  alternately  increasing  and  decreasing  ammonia  c o n c e n t r a t i o n s by c a u s i n g convergences and d i v e r g e n c e s . D i f f e r e n c e s i n DO between t h e i n s i d e and o u t s i d e o f t h e net-cages were s i g n i f i c a n t o n l y a t t h e JER s i t e , and o n l y a t 6 m depth  (Table  2) .  This  finding  perhaps  gives  further  weight t o t h e argument t h a t t h e b u l k o f t h e f i s h a r e l o c a t e d i n t h e mid-depths o f t h e cage, hence t h e g r e a t e r  depletion  of DO a t t h i s depth. A g a i n , t h e l o c a t i o n o f t h e sampled cage at  the  SEC  meaningless.  location  makes  inside/outside  comparisons  F i g u r e 7. S c a t t e r diagram o f t o t a l ammonia v e r s u s c u r r e n t speed f o r d a t a c o l l e c t e d a t mid-cage depth (6 nv) o f cage. 23 a t t h e J e r v i s I n l e t s i t e . The l i n e i s t h e l e a s t squares r e g r e s s i o n l i n e w i t h c o e f f i c i e n t of determination (r^) i n d i c a t e d . A t - s t a t i s t i c was used t o t e s t s i g n i f i c a n c e ( p ) .  29 F i g u r e 8 . S c a t t e r d i a g r a m o f t o t a l ammonia v e r s u s c u r r e n t s p e e d f o r d a t a c o l l e c t e d a t t h e m i d - c a g e d e p t h (2 m) i n cage 6 a t t h e S e c h e l t I n l e t s i t e . The l i n e i s t h e l e a s t squares r e g r e s s i o n l i n e with c o e f f i c i e n t of determination ( r ) i n d i c a t e d . A t - s t a t i s t i c was u s e d t o t e s t s i g n i f i c a n c e (p) . 2  12 R e g r e s s i o n line: 10--  o E  r  O  E E D  £  =0.08  p=0.26  8 A  'c  2  .  A  6 -  A  •  A  4 -  A A  2 +  A  A ~  A  • A  A  A  A  i  0 0  i  4  i  6  J ....- —  i  8  10  1  1  1  1  12  14  16  18  . Current Speed ( c m / s e c )  20  Diurnal  periodicity  of  DO  at  the  JER  location  ( F i g u r e 9) i s t y p i c a l o f a p h y t o p l a n k t o n - d r i v e n DO regime a t 1 m.  Near  surface  waters  (1 m)  exhibited  p r o d u c t i o n o f DO d u r i n g t h e d a y l i g h t occurring  during  phytoplankton, dominated.  dark  hours  The l a r g e s t  hours, w i t h  when  and o t h e r organisms  photosynthetic  respiration  a DO sag by  i n t h e water  fish, column  sag however, o c c u r r e d a t 10:00 and  i t was thought t h a t t h e metabolism o f f e e d i n g f i s h may have had some i n f l u e n c e as they moved up i n t o  t h e near  surface  waters t o f e e d . DO v a l u e s a t t h i s s i t e d i d ' o c c a s i o n a l l y r e a c h l e v e l s a t which oxygen (Davis,  some  fish  stress,  would  begin  particularly  to exhibit at  11 m.  symptoms o f .low  Protection  level B  1975) i s s e t a t 6.43-9.00 mg O2/L, and exposure t o  t h e m i n i m a l v a l u e i s c o n s i d e r e d t o pose some degree o f r i s k if  extended  f o r more t h a n a few h o u r s . Caveat: i n s t r u m e n t  e r r o r may have been as much -10% i n DO r e a d i n g s . A r e c o r d e d o f 6.5 mg O2/L  concentration  been as h i g h as 7.2 mg O2/L  may  therefore  actually  have  (but was s t i l l w i t h i n l e v e l B ) .  To a v o i d p r o l o n g e d exposure t o low DO, t h e f i s h c o u l d have moved t o near s u r f a c e w a t e r s . P h i l l i p s farmed Salmo gairdneri their  position  within  (1985) i n d i c a t e s t h a t  R i c h a r d s o n (rainbow t r o u t ) may a  net-cage  to  avoid  alter  temperature  extremes. He argues f u r t h e r t h a t a g g r e g a t i o n o f f i s h i n one portion  of  the  cage  should  not  be  considered  under-  u t i l i z a t i o n o f t h e a l l o c a t e d space, b u t r a t h e r , a p r o v i s i o n  Figure 9. Plots of dissolved oxygen versus time for the indicated sampling depths at the Jervis Inlet s i t e . Each data point i s a single sample - see text for error estimation.  15 • O A  13-  D i m 06m A 1 1m  E c 1 -|E3 CD cn  X  O "D CD _>  O- o - c r  CO  5  \ A  9  O  -[]  /O  7  A -  16:00  A  -  A  '  A  ^ A —A "  22:00  o A  ^- A^ A  o *o-o  A  ^A— —A-A—A-A,  04:00 Time of day  V  o-  A  10:00  - A - A  16:00  32 o f a -refuge from u n f a v o u r a b l e  c o n d i t i o n s . Thus, i t i s c l e a r ,  t h a t any e v a l u a t i o n o f water q u a l i t y w i t h i n a net-cage must i n c l u d e s a m p l i n g over t h e complete depth o f the cage as the fish  may  behaviourally  s e l e c t any  portion  o f the  cage  in  which t o r e s i d e . DO the  concentrations  25 h  at t h e SEC  sampling p e r i o d  s i t e v a r i e d g r e a t l y over  ( F i g u r e 10) . The  effect  of  the  i n t e r n a l wave p a s s i n g t h r o u g h t h e s i t e i s apparent i n t h e data  ( F i g u r e 10). F o r example, DO  r i s e from <7 mg/L to  03:00. The  t o near 9 mg/L  l e v e l s at 4 m a r e seen t o  t h e d u r i n g t h e p e r i o d 22:00  only p l a u s i b l e explanation  for this  increase  of DO d u r i n g t h e night,- i s convergence o f t h e water  column,  caused presumably by t h e passage o f an i n t e r n a l wave t h r o u g h the net-cage. Linear  regressions  o f DO  s i g n i f i c a n t at t h e JER s i t e  and  current  speed  were  not  ( F i g u r e 11) but were s i g n i f i c a n t  at the SEC l o c a t i o n ( F i g u r e 12). In b o t h cases, t h e s l o p e i s i n t h e p r e d i c t e d o r i e n t a t i o n , t h a t i s , as speed  increased,  DO c o n c e n t r a t i o n s i n c r e a s e d . However, at t h e SEC s i t e , an r ^ v a l u e o f 0.16 can  be  i n d i c a t e s t h a t o n l y 16% o f t h e v a r i a n c e i n DO  attributed to  ammonia and  current  (photosynthesis  and  current speed,  the  speed.  As  i n the  interaction  respiration)  and  of  physical  case  for  biological processes  cannot be d e s c r i b e d by a s i m p l e l i n e a r f u n c t i o n . A n a l y s i s of more d a t a ,  c o l l e c t e d over t h e f u l l  may h e l p t o c l a r i f y t h i s  monthly  relationship.  range  of t i d e s ,  33  F i g u r e 10. P l o t s o f d i s s o l v e d oxygen v e r s u s t i m e f o r t h e i n d i c a t e d s a m p l i n g depths a t t h e S e c h e l t I n l e t s i t e . Each d a t a p o i n t i s a s i n g l e sample - see t e x t f o r e r r o r estimation.  1  8  :  0  0  .  2  3  :  0  0  0  4  :  0  0  .  0  9  Time of day  :  0  0  1  4  :  0  0  1 9 : 0 0 '  F i g u r e 11. S c a t t e r diagram o f d i s s o v e d oxygen v e r s u s c u r r e n t speed f o r d a t a c o l l e c t e d a t mid-cage depth (6m) o f cage 23 a t t h e J e r v i s I n l e t s i t e . The l i n e i s t h e l e a s t squares regression l i n e with c o e f f i c i e n t of determination ( r ) i n d i c a t e d . A t - s t a t i s t i c was used t o t e s t s i g n i f i c a n c e ( p ) . 2  Current Speed ( c m / s e c )  35  F i g u r e 12. S c a t t e r diagram o f d i s s o l v e d oxygen v e r s u s c u r r e n t speed for. d a t a c o l l e c t e d a t t h e mid-cage depth (2 m) i n cage 6 a t t h e S e c h e l t I n l e t s i t e . The l i n e i s t h e l e a s t squares r e g r e s s i o n l i n e w i t h c o e f f i c i e n t o f d e t e r m i n a t i o n ( r ) i n d i c a t e d . A t - s t a t i s t i c was used t o t e s t s i g n i f i c a n c e (P) • 2  11 R e g r e s s i o n line: r  2  = 0 . 1 6 ' p = 0.04  10 E A  c cu X  O  9~ "  A  AA*  --_ A _ _ _ ^ — —  1  A  a>  j> o  CO CO  8-  A  A  Q  7  1  0  1  1  1  6  8  —1  10  —_ i _  12  1  1  1  14  16  18  Current Speed ( c m / s e c )  20  36  Current  speeds  were  l o c a t i o n than t h e JER in JER  generally  location  higher  at  the  SEC  be  due,  (Table 2) . T h i s may  p a r t , t o the presence o f mussels f o u l i n g t h e n e t s at t h e s i t e t o a depth of c a . 4 m.  The  SEC  s i t e had  recently  replaced, clean nets. The r e s t r i c t i o n o f t h e t i d a l waters t h r o u g h Skookumchuk Narrows,  over  the  entrance  sill  to  the  Sechelt  Inlet,  r e s u l t s i n a " t u r b u l e n t j e t " ( L a z i e r , 1963) . T h i s " t u r b u l e n t jet"  s e r v e s t o a c c e l e r a t e t h e near s u r f a c e waters and  c u r r e n t speeds are h i g h e r near t h e s i l l the  inlet.  No  such event  t h a n at t h e head of  o c c u r s over t h e deep s i l l  e n t r a n c e t o J e r v i s I n l e t - where t h e JER s i t e was It shallow  at the  located.  i s suggested t h a t p r o x i m i t y o f t h e S e c h e l t s i t e t o a sill  has  waves g e n e r a t e d period  thus  waves  convergences  put by  i t under  tidal  propagate and  the  action along  influence  at t h e  density  divergences  i n the  sill.  of  internal  These  interfaces, near  long-  causing  surface  waters  ( P i c k a r d , 1954). The t i d a l component o f t h e s e waves can be observed i n t h e t w i c e d a i l y the  DO,  Sigma-t,  and  stratification  temperature  plots.  changes seen i n Implications  of  t h e s e events t o f i s h farmers a r e many. As t h e time o f d a i l y t i d a l e v e n t s p r o g r e s s e s about of  occurrence  of  these  one hour e v e r y day,  events  also  progresses.  The  t e m p e r a t u r e s throughout  the cages  h a r m f u l t o the f i s h i f ,  f o r i n s t a n c e , a convergence o c c u r r e d  during  an  temperatures  exceptionally reached  warm  dangerous  may  t h e time  o c c a s i o n a l l y become  period  levels  when  (greater  surface  than  21 °C  37 for  chinook;  Caine e t a l . , 1987).  t e m p e r a t u r e may is  to  rapid  increase  in  s t r e s s t h e f i s h , p a r t i c u l a r l y i f the change  >5 °C w i t h i n a 12 h p e r i o d  increase  A  i n temperature may  o c c u r which may  (Caine e t a l . , 1987) . A a l s o cause  lead to f i s h k i l l s  gas  rapid  supersaturation  (Weitkamp and K a t z ,  1980) . Water  mass  convergences  p h y t o p l a n k t o n i n the water which may in  the  Early  also  column  mean may  that  any  harmful  become c o n c e n t r a t e d ,  r e s u l t i n f i s h k i l l s at c o n c e n t r a t i o n s t h a t would,  absence warning  of  an  internal  networks  of  wave,  have  been  phytoplankton  harmless.  watches  must  t h e r e f o r e add a s a f e t y f a c t o r i n t o t h e i r abundance e s t i m a t e s if  i n t e r n a l waves are p r e s e n t i n t h e i r  harmful  effects  imposed  by  n e a r - s u r f a c e c o n d i t i o n s , may net-cages, internal  which  wave. By  farmers may  internal  tides,  of  or u n f a v o r a b l e  be brought about by u s i n g deep  e x t e n d below employing  area. M i t i g a t i o n  the  depth  affected  lower s t o c k i n g  by  densities  the fish  a l l o w t h e f i s h t o b e h a v i o u r a l l y s e l e c t t h e most  f a v o u r a b l e p o r t i o n o f t h e water  column.  38  Conclusions:  D e f i n i n g water q u a l i t y  as t h e c o n c e n t r a t i o n o f DO  and  ammonia p r e s e n t , a l l o w s t h e f o l l o w i n g c o n c l u s i o n s t o be made based on d a t a c o l l e c t e d at two farm s i t e s d u r i n g t h e c o u r s e of t h i s s t u d y . D i s s o l v e d oxygen levels the  low enough t o have caused s t r e s s t o some members o f  fish  Inlet  c o n c e n t r a t i o n s were observed t o r e a c h  p o p u l a t i o n , at depths o f 6 and  site  and at a l l depths  sampled  11 m at t h e  Jervis  at t h e S e c h e l t  Inlet  site. U n - i o n i z e d ammonia l e v e l s d i d not exceed t h e a c c e p t e d criterion  NH3/L) at e i t h e r 25  effects  (0.025 mg  depth sampled,  over the  s e t f o r avoidance o f s u b l e t h a l location,  at any  h sampling periods. The presence o f a s h a l l o w s i l l  near t h e S e c h e l t  s i t e , v e r s u s a deep s i l l near t h e J e r v i s I n l e t s i t e , marked d i f f e r e n c e s i n hydrography between the two  Inlet  created  locations.  The s h a l l o w s i l l , g e n e r a t e d i n t e r n a l waves which, upon t h e i r passage  through  structure.  the  Subsequent  farm  site,  changes  modified  were  also  the  density  observed  in  temperature and DO p r o f i l e s over the depth of t h e cages, and i t was proposed t h a t measures,  such as i n c r e a s i n g cage depth  and l o w e r i n g s t o c k i n g d e n s i t i e s , must be t a k e n by the farmer to  m i t i g a t e t h e p o t e n t i a l impact o f t h e s e changes upon  stocks.  fish  39 Chapter  Net-cage  2:  fish  f a r m i n g i n B r i t i s h Columbia:  a case study o f  water c i r c u l a t i o n and water q u a l i t y i n a l a r g e r a f t o f cages  Introduction  T h i s p o r t i o n o f t h e study was undertaken t o observe t h e effects  of  the  combined  periodicity  of  biological  and  p h y s i c a l phenomena over a 25 h p e r i o d , i n v a r i o u s p o s i t i o n s and depths w i t h i n a 260,000 kg f i s h farm. Sampling  involved  t h r e e p a r t s or e x p e r i m e n t s . P a r t A, was t o measure t h e water f l o w as a f u n c t i o n o f depth i n a s t o c k e d net-cage which had been submerged f o r c a . 30 days. T h i s experiment would indicate  whether  or  present,  which would  not  a  horizontal  dictate  velocity  t h e placement  shear  of the  (DO  and  Lastly,  ammonia) a c r o s s t h e  s a m p l i n g 'program  which  to  was  overlapped  measurements as much as was designed  site  i n P a r t C, water  was  current  meters f o r the second phase. P a r t B examined t h e water patterns w i t h i n the s i t e .  also  flow  quality  m o n i t o r e d i n a 25 h  concurrent  water  flow  l o g i s t i c a l l y possible. This l a s t  program  was  test  quality  would be p o o r e r i n t h o s e cages  downstream i n t h e predominant  the  hypothesis that which were  flow d i r e c t i o n .  water located  40 M a t e r i a l s and Methods The this  JER  study  s i t e p a r t i c u l a r s and are  described  s e c t i o n of Chapter 1. As p e r i o d of m i n i m a l t i d a l  in  equipment/methods used i n  the  i t was  Materials  and  Methods  d e s i r e d t o sample d u r i n g a  f l o w , sampling  was  scheduled  neap t i d e s (moon i n ' 1st q u a r t e r on J u l y 21,  during  1988). Sampling  p r o t o c o l i s o u t l i n e d below:  Part  A  Three c u r r e n t meters were d e p l o y e d at 2, 5, depth  inside  simultaneously cage 19,  net-cage 6,  while  deployed  2, 5, 8, and  at  on the n o r t h s i d e of the  4  current 11 m  raft  8 m  meters  were  outside  net-  ( F i g u r e 2) . C u r r e n t  meters were programmed t o sample f o r 2 min p e r i o d , and remained i n p o s i t i o n f o r 25  Part  and  i n every  h.  the  f i n d i n g s of P a r t A,  current  meters were  d e p l o y e d at 6 m i n the l o c a t i o n s shown i n F i g u r e 2. was  as  simultaneous to  min  B  Based on  rate  10  21:00  sampling  per  Part  records  21/07/88,  A.  to  logistics,  f o r each i n s t r u m e n t which  program of P a r t  procession  Due  of t i d e s was  overlapped  was the  the  for this  period  of  20:00 20/07/88 water  C f o r a p e r i o d of 4 h. 1 h  Sampling  location,  quality The  and  daily hence,  v a l i d comparisons of water q u a l i t y and water f l o w were made by s h i f t i n g the time s c a l e a p p r o p r i a t e l y .  41 Part C  Water q u a l i t y s a m p l i n g was done i n s i d e and o u t s i d e cage 23 as w e l l as i n s i d e cage 15 every 1.5 h f o r a 25 h beginning  at  16:00  21/07/88  Samples  f o r ammonia a n a l y s i s  depth,  while  the  and  ending  17:00  period,  22/07/88.  were c o l l e c t e d a t 0.5 and 6 m  Surveyor®  II  was  used  to  t e m p e r a t u r e , pH, s a l i n i t y , and DO a t 1, 6, and 11 m.  measure  42 Results Weather remained these  conditions  cloudless with v i r t u a l l y  nearly  remained  throughout  ideal  these  experiments  no wind. As  meteorological  calm which meant t h a t no  a result  conditions,  the  of  seas  adjustments t o t h e d a t a  were n e c e s s a r y t o account f o r wind d r i v e n c u r r e n t s .  Part A  F i g u r e 13 experiment.  Each  summarizes b a r on  the  findings  t h e graph  of  the  profile  i s the average  speed over 25 h which c o n s i s t e d of 150-two minute  current recording  e p i s o d e s . The l a c k of any s t r o n g v e r t i c a l v e l o c i t y shear i s i n d i c a t e d by the s i m i l a r i t y  of c u r r e n t  speed at a l l depths  o u t s i d e t h e n e t - c a g e s . C u r r e n t speed at 2m, is  i n s i d e cage 6,  reduced by 65% r e l a t i v e t o t h a t at t h e n o r t h e r n c u r r e n t  meter l o c a t i o n .  At depths  greater than  5 m,  current  speed  i n s i d e and o u t s i d e t h e net-cages i s n e a r l y i d e n t i c a l , w i t h a slightly  h i g h e r speed  inside  at 5 m  and  a slightly  lower  speed i n s i d e at 8 m depth. SCUBA d i v e r s r e p o r t e d t h a t  heavy  f o u l i n g o f t h e n e t s by mussels o c c u r r e d t o a depth o f about 4 m.  F i g u r e 13. P l o t o f c u r r e n t speed v e r s u s depth f o r t h e p r o f i l e experiment a t t h e J e r v i s I n l e t s i t e . E r r o r b a r s a r e one s t a n d a r d d e v i a t i o n .  44 Part B  Current period  speed  f o r each  of the current  F i g u r e 14. Each compass, which  and d i r e c t i o n  current ensures  meter that  over meters  t o the p e r i o d i c swinging  lines,  orientation  horizontal  axis  sampling  i s illustrated in  contains  i t s own  magnetic  the h o r i z o n t a l axis  f o r each  v e c t o r diagram has t h e same east-west due  t h e 25 h  orientation.  of the r a f t  However,  upon i t s mooring  of the r a f t ' s long axis r e l a t i v e t o the of  the  vector  diagrams  is  variable.  N e v e r t h e l e s s , v i s u a l o b s e r v a t i o n s o f r e f e r e n c e p o i n t s on t h e neighbouring  i s l a n d i n d i c a t e d t h a t t h e r a f t r o t a t e d no more  than 10 degrees over a t i d a l c y c l e . The records raft  twice  daily  provided  r e v e r s a l of the t i d e  by t h e i n s t r u m e n t  i s seen  i n the  north  of the  deployed  ( F i g u r e 1 4 ) . Average d i m i n u t i o n o f c u r r e n t speed a c r o s s  the s i t e from n o r t h t o south i s a p p r o x i m a t e l y the  southern  side of the r a f t  e x h i b i t slower Directional relative The  changes  i n flow  t o the northern directional  signal  i s masked  Current  change by  same  cage south,  pattern  of  adjacent  are evident  outside  speed i s t h e h i g h e s t  w i t h t h e next the  c u r r e n t speeds than  greatest  tidal  ( i . e . cages  a  reference  30%. Cages on 2, 6, and, 10)  northern  cages.  i n a l l cages current  meter.  i s i n cage 15, where t h e p e r s i s t e n t westward  flow.  (ave. 5.3 cm/sec) i n cage 15,  cage 10, a l s o e x h i b i t i n g some o f  deviation  away  i n f l u e n c e b o t h i n speed and d i r e c t i o n .  from  typical  tidal  45 Figure 14. Vector diag rams of data collected at the indicated locations i n and around the r a f t of net-cages at the Jervis Inlet s i t e . Depth of instrument deployment was 6 m for a duration of 25 h. Data was c o l l e c t e d simultaneously at each l o c a t i o n . The length of each vector i s proportional to cur rent speed (1 d i v i s i o n = 1 cm/sec),' while the orientation indicates flow d i r e c t i o n . Figures above diagrams are ave rage speed and (direction) for the 25 h sampling period i l l u s t r a t e d i n each vector diagram.  46-  Part C  Plots  of  i n s i d e cages  dissolved  oxygen  concentrations  23 and 15 f o r t h e 25 h d a t a c o l l e c t i o n  are shown i n F i g u r e 15. D i u r n a l p e r i o d i c i t y 1 m plots  measured period  i s seen  i n the  i n s i d e b o t h cages. The l o w e s t DO v a l u e s o c c u r r e d  between 01:00 and 06:00 except  f o r one sample a t 20:30 i n  cage 15. (Sunset o c c u r r e d a t 20:50 and s u n r i s e a t 05:30).  DO  v a l u e s f o r b o t h cages were h i g h e r near t h e s u r f a c e t h a n a t 6 or 11 m  (Table 3 ) . The o n l y s i g n i f i c a n t d i f f e r e n c e  observed  between t h e two cages was a t 6 m depth, where cage 23 showed g r e a t e r v a l u e s t h a n cage  15.  The p a t t e r n o f ammonia c o n c e n t r a t i o n changes over 25 h in  both  cages  was  similar  ( F i g u r e 1 6 ) . Peak v a l u e s  f o r the surface sampling  o c c u r r e d a t 10:00 and 05:30 f o r  cages 23 and 15 r e s p e c t i v e l y . ammonia v a l u e s  depth  No  clear  pattern  was  apparent.  f o r s u r f a c e waters  o f minimum The  daily  time c o u r s e o f ammonia c o n c e n t r a t i o n was even more i r r e g u l a r at  6 m depth. V a l u e s  waters.  There  concentrations, (Table 3) .  are higher at 6 m than  were .no s i g n i f i c a n t at e i t h e r  depth,  near  differences between  cages  surface  i n ammonia 23 and 15  F i g u r e 15. Comparisons o f d i s s o l v e d oxygen c o n c e n t r a t i o n s v e r s u s t i m e f o r t h e i n d i c a t e d depths i n cage 2 3 ( O ) and cage 15 ( • ) a t t h e J e r v i s I n l e t s i t e .  CP  c  CD  1 0  -  6 meters  9  V  CD >s X O  8  TJ  7  CD >  O  -o--o  .•--§.  >  -O  6  CO CO  Q  11  T  1 o 4-  11 meters  8 + 7 6  5  16:00  22:00  04:00  T i m e of d a y  10:00  16:00  Table 3. Comparisons o f DO and t o t a l ammonia i n s i d e cages 23 and.15 a t t h e JER s i t e . Data were p o o l e d f o r each depth and l o c a t i o n u s i n g v a l u e s c o l l e c t e d over t h e 25 h s a m p l i n g program. (SD=standard d e v i a t i o n , df=degrees o f freedom) Location  JER 21 J u l y , 1988  Depth (m) 1 6 11 0.5 6  Parameter  DO (mg/L) total ammonia (|imol/L)  Cage 23 mean (SD)  Cage 15 mean (SD)  ^calc  t-test (df)  9.5 (0.8) 7.9 (0.5) 6.5 (0.2)  9. 3 (0 .8) 0 . 682 (34) 7. 1 (0 .6) 4 .358 (34) 6. 4 (0 .3) 1 .382 (34)  0.9 (1.1) 4.4 (2.6)  0. 9 (0 .8) 0 .059 6. 1 (2 .5) 1 .791  (34) (27)  p 0 .500 <0 .001 0 . 176 0 . 953 0 .085  49 F i g u r e 16. Comparisons o f ammonia c o n c e n t r a t i o n s v e r s u s time f o r cages 23 & 15 at t h e J e r v i s I n l e t s i t e . Depth o f sampling was A) 0.5 m and B) 6 m.  A  o E  3 o 'c o E E D  ~o •*->  O  16:00  22:00  04:00  10:00  16:00  10:00  16:00  B 10 +  o E D  'c  O  E E D "5 -t-> o  16:00  22:00  04:00 T i m e of day  50 Discussion •The (1972)  profile and  experiment  Wee's  (1979)  (Part  A)  findings  c o n s t r u c t i o n o f net-cages may  confirmed  that  Inoue's  nets  used  in  r e s t r i c t water f l o w up t o 80%,  depending upon t h e degree t o which t h e y were f o u l e d . I t was found  that  current  speeds  were d i m i n i s h e d  by  65%  at  the  depths where the net was  f o u l e d by mussels and macro-algae,  however  below  the  and  outside  a t depths  w i t h i n ±11%  inside  c u r r e n t speed was  fouling,  current  speeds  o f the net-cage.  In  were fact,  c a . 11% g r e a t e r i n s i d e t h e net-cage t h a n  o u t s i d e a t 5 m, perhaps due t o t h e swimming b e h a v i o u r o f t h e fish.  Inoue  (hamachi) the  may  ambient  have  (1972)  also  found  that  cause a r o t a t i n g current  been  speed  reported  falls  Seriola  current  quinqueradiata  o f 1-3 cm/sec when  below  to maintain a  4 cm/sec.  Salmonids  circular  swimming  p a t t e r n i n n e t - c a g e s , t h e d i r e c t i o n of which was m a i n t a i n e d regardless et a l . ,  of t i d e ,  1979).  season, o r age  Inoue  (1972)  of the f i s h  indicated  that  this  (Sutterlin behaviour  would r e s u l t i n water exchange b e i n g m a i n t a i n e d t h r o u g h the net^-cage even d u r i n g p e r i o d s of l i t t l e or no t i d a l Overall patterns are  i n general  raft  relative  Weston's  o f f l o w diminishment a c r o s s t h e  agreement  (1986) . Flow was  flow.  with  the  predictions  of  Weston  reduced c a . 30% on t h e s o u t h s i d e o f t h e  to  the  north,  which  compares  well  (1986) p r e d i c t i o n o f 50% b l o c k a g e . Because  the  influence  of b i o f o u l i n g  be  accurately  with  neither  was t h e d i r e c t i o n o f c u r r e n t p e r p e n d i c u l a r t o t h e r a f t , could  site  nor  measured,  51 these The  f i g u r e s are considered  t o be i n r e a s o n a b l e  s u r p r i s i n g finding i n t h i s part  apparent  directional  shift  and  o f t h e study,  overall  enhances reason  that  water  the  swimming  velocity  for this  of t h e r a f t  i n an area  islets  put  may  topographic Either  cages,  t h e most  i s that  o f many bottom  i t partially  the  local  fish likely  bottom  f l o w p a t t e r n s . The l o c a t i o n i r r e g u l a r i t i e s and  under  s t e e r i n g o r an eddy  of these  from t h e d o u b t f u l of  anomaly  topography i n f l u e n c e d t h e t i d a l  current  behaviour  i n these  apparent  was t h e  greater  speeds o b s e r v e d i n cages 15 and 10. A s i d e speculation  agreement.  the  influence  of  (Pond and P i c k a r d , 1986) .  phenomena would a l s o produce t h e o b s e r v e d  anomalies i n c u r r e n t speed and d i r e c t i o n a c r o s s t h e r a f t by subjecting various  portions of the r a f t  to different  flow  streams. The time  dynamics  o f d i s s o l v e d oxygen over b o t h depth and  are t y p i c a l  values 6.1  f o r the J e r v i s  Inlet  area.  Historical  (DOUBC, 1985 and 1986) i n d i c a t e t h a t DO ranges  t o 7.9  mg/L  f o r t h e summer  months  at  10 m,  from which  compares w e l l w i t h measured v a l u e s o f 6.5 mg/L a t 11 m. The near  surface  diurnal  varied  periodicity  explained those  DO  diurnally,  presumably  of photosynthesis  and r e s p i r a t i o n  i n Chapter 1. Cage 15 DO v a l u e s  o f cage 23 i n s p i t e o f t h e g r e a t e r  were lower current  the  former. S t o c k i n g d e n s i t i e s were s i m i l a r  but  the f a s t e r current  greater  swimming  speed  with  the as than  speed . i n  i n both  cages,  speed i n cage 15 may n e c e s s i t a t e a and hence,  metabolic  rate  by t h e  52 f i s h . An i n c r e a s e i n m e t a b o l i c r a t e would i n c r e a s e t h e r a t e of  oxygen  as  well  ammonia p r o d u c t i o n (McLean  and  changes  consumption  i n water q u a l i t y  as  increase  Fraser,  were seen  the  1974).  i n cage 15  rate  Both  of  these  relative  to  cage 23, which e x p e r i e n c e d s l o w e r water speeds. T h i s f i n d i n g was  surprising,  s i n c e i t found i n Chapter 1 t h a t  in  water  would  flow  concentrations. correlation case,  is  increase  Perhaps  the  between water due  to  metabolic rate.  a  DO  As c u r r e n t  decrease  inability  quality  balance  and  to  and water  between  increases  detect  speed  flushing  speed i n c r e a s e d ,  ammonia a  in this rate  flushing  and rates  i n c r e a s e d but m e t a b o l i c r a t e s would have a l s o i n c r e a s e d t h u s , l i t t l e change i n water q u a l i t y was The  location  of  these  two  and  observed.  cages  within  the  raft,  c o u p l e d w i t h t h e observed f l o w d i r e c t i o n s i n d i c a t e s another tenable  explanation.  Cage 15  e a s t e r n end o f t h e r a f t , t h e two  i s the  third  cage  from  the  and appears t o r e c e i v e water  from  eastern-most a d j a c e n t cages t h r o u g h o u t most of t h e  t i d a l c y c l e . T h i s f l o w regime a d v e c t s DO-depleted,  ammonia-  loaded, waters from t h e e a s t e r n cages, i n t o cage 15. At t h e western end  o f the r a f t ,  from the o u t s i d e  o f cage  t h e predominant  current  flow  23, t h e r e b y a d v e c t i n g water  was that  has not a l r e a d y been t h r o u g h s u r r o u n d i n g net-cages and  was  c o n s e q u e n t l y o f h i g h e r water q u a l i t y . In column  order to observed  reference  to  compare in this  background  ammonia enrichment study  with  levels  of t h e  predicted  was  needed.  water  values,  a  Sampling  53 performed o u t s i d e cage 23 c o u l d be c o n s i d e r e d t o be upstream of the r a f t average  f o r at least part of the t i d a l  ammonia  concentrations  i n s i d e t h e cages depths. total  were  cycle.  lower  In f a c t ,  outside  (by 0.4 and 2.7|imol/L a t s u r f a c e and 6 m  r e s p e c t i v e l y ) . Weston ammonia c o n c e n t r a t i o n  (1986) p r e d i c t e d  o f 0.02 mg/L  a rise i n  (=1.4 (xmol/L) i n  waters p a s s i n g t h r o u g h a farm o f s i m i l a r biomass. much  greater  than  than  predicted  within  the net-cages.  effect  by t h e whole  were  However,  periodically  Weston  250,000 kg farm,  because o f m i x i n g by t i d a l  action,  Values observed  was p r e d i c t i n g t h e and i t i s d o u b t f u l ,  and t h e r a p i d uptake o f  ammonium by p h y t o p l a n k t o n ( G l i b e r t and Goldman, 1981), these  predicted  values  would  be  observed  that  a t any g r e a t  d i s t a n c e from t h e farm i t s e l f . The outside  only of  significant  t h e cages  (Table 2) . A t t h i s  difference  was  depth  observed  i n DO at  6m  t h e 25 h average  inside  and  i n Cage 23  difference  0.4 mg O2/L, which compares f a v o u r a b l y w i t h Weston's  was  (1986)  p r e d i c t i o n o f a 0.3 mg O2/L d e c r e a s e . It ammonia  i s suggested t h a t enrichment o f t h e environment i n i s occurring .within  this  farm  site.  (Dr. P . J . H a r r i s o n , u n p u b l i s h e d data) c o l l e c t e d 1987  near  indicate  Active that  Pass,  i n the S t r a i t  ammonium v a l u e s never  12 m depth. Moreover,  Cruise  on 28 J u l y ,  of Georgia,  exceed  data  B.C.,  0.47(imol/L a t  a s t a t i o n over t h e Iona I s l a n d sewage  o u t f a l l , y i e l d e d v a l u e s up t o 9.42(imol/L ammonium. C l e a r l y , hypernutrification  o f t h e water  column i s o c c u r r i n g  within  54 the  farm  never  site,  but even  as h i g h  outside  as i n s i d e ,  s u r r o u n d i n g waters  o f cage 23, v a l u e s  indicating  that d i l u t i o n  were  i n the  i s r a p i d . B l a c k and C a r s w e l l (1986)  found  t h a t ammonia v a l u e s downstream o f a f i s h farm which was not in  use, but f o u l e d w i t h  mussels,  were  similar  to  values  measured a t t h e same d i s t a n c e downstream from a p r o d u c t i v e farm. the  This  true  f i n d i n g would make i t v e r y  impact  of f i s h  farming  f o u l i n g organisms c o u l d be found  difficult  t o assess  a site  deplete of  unless  (e.g. immediately  a f t e r net  cleaning). I n c r e a s e s i n biomass, l e n g t h and c h l o r o p h y l l a c o n t e n t o f t h e green a l g a Cladophora  glomerata  to  fish  i n c r e a s e d n u t r i e n t s near  have been a t t r i b u t e d  farms  i n the B a l t i c  ( R u o k o l a h t i , 1988). I n t h e c o a s t a l waters depletion  is  phytoplankton input the  often  the  blooms  limiting  o f B.C., n u t r i e n t  factor  (Harrison et a l . ,  and  magnitude  i n regulating  1983)  and  serve  to increase  o f ammonia t o t h e environment may frequency  o f blooms.  No  t o salmon f a r m i n g ,  however, i n t e n s i v e f i s h  the I n l a n d Sea o f Japan has been suggested dissolved  organic  occurrence  of  Gymnodinium (Nishimura,  matter,  toxic type-'65  1982).  red  responsible tide and  so any  evidence  i n c r e a s i n g bloom frequency has been r e p o r t e d f o r B.C. due  Sea  of  waters  culture i n  t o be a source o f  f o r i n c r e a s i n g the  causing Chattonella  phytoplankton, antiqua  55  Conclusions:  Water f l o w and net-cages,  although  differences  they  flow  was  and  due  to  observed  the  Observed  mussels on the upper 4 m of the n e t - c a g e . Good agreement published  were  unrelated.  of  between  water  appeared t o be  presence  found  in  water q u a l i t y v a r i e d w i t h depth i n s i d e  values  for  current  d i m i n u t i o n r e s u l t i n g from f o u l i n g . Observed d i f f e r e n c e s over depth, i n DO  and  ammonia c o n c e n t r a t i o n s , were s p e c u l a t e d  be a r e s u l t of f i s h b e h a v i o u r  to  and metabolism i n c o n j u n c t i o n  w i t h water f l o w p a t t e r n s . It  was  found  outside  of  the  patterns local  was  that raft  the to  use  of  predict within  sometimes m i s l e a d i n g .  topography  current  raft  I t was  influenced within  site  flow  patterns  water  flow  speculated  that  flow  patterns  such a degree t h a t i n some downstream cages, h i g h e r speeds were e x p e r i e n c e d For  water  Comparisons  made  exchange using  the  in  the  data  downstream s i d e of the r a f t r e l a t i v e  ammonia  variations  concentrations  p r e d i c t i o n s of Weston  in were  (1986).  raft,  the  raft  predicted  current  the  two  on  the  speeds  t o upstream.  dissolved in  did  fashion.  c o l l e c t e d from  s t a t i o n s , i n d i c a t e d slower  Observed  current  upstream.  c e r t a i n l o c a t i o n s w i t h i n the  influence  outside  t h a n those  to  oxygen  agreement  and with  total the  56 General D i s c u s s i o n  While  some  of  this  study  c o n d i t i o n s w i t h i n net-cages Europe,  the  conditions  lack  of  involved  i n B.C.  previous  comparison  of  t o t h o s e i n Japan  and  data  and p r a c t i c e s made t h i s  for  local  farming  a necessary f i r s t  step.  R e s u l t s were found t o be comparable t o t h e p r e v i o u s s t u d i e s w i t h r e l a t i o n t o diminishment o f c u r r e n t speed, o f DO,  and b u i l d - u p o f ammonia w i t h i n a f i s h farm net-cage.  From the p e r s p e c t i v e may  utilization  of the f i s h  a i d i n determination of  farmer, t h i s  raft  information  configuration,  net-cage  depth, s t o c k i n g d e n s i t y , and g e o g r a p h i c l o c a t i o n . The  influence  of  hydrography  considered i n s e l e c t i n g a s i t e  should  always  ( L a n d l e s s and Edwards, 1976).  Moreover, t h e presence o f e d d i e s , t o p o g r a p h i c s t e e r i n g , internal  waves  account.  If  through  discovery  be  a  site  of  any  must of  also these  be  taken  and into  topographically  d e r i v e d problems o c c u r s a f t e r t h e farm s i t e i s e s t a b l i s h e d , m i t i g a t i o n may  be  lower  density,  stocking  as s i m p l e as employing deeper to  allow  the  fish  nets with  to inhabit  the  l e a s t p h y s i o l o g i c a l l y s t r e s s f u l p o r t i o n of t h e water column ( P i c k e r i n g , 1981). In the case o f d i f f e r i n g w i t h i n the r a f t ,  reorientation  ambient c u r r e n t p a t t e r n s may In varied  net-cages markedly  at  with  the  speeds  o f the r a f t w i t h r e s p e c t t o  a l s o i n c r e a s e w a t e r exchange.  Jervis  depth,  current  with  Inlet  farm,  t h e near  r e m a i n i n g t o o warm f o r o p t i m a l growth  temperatures  surface  waters  (Caine e t a l . ,  1987).  However, t h e use o f 15 m deep nets,' a l l o w s a r e f u g e f o r the  57 fish  below the t h e r m o c l i n e , thereby d e c r e a s i n g s t r e s s ,  and  hence, i n c r e a s i n g growth r a t e . The  concept  of  a  refuge  within  the  net-cage  also  a p p l i e s to avoidance of harmful phytoplankton s p e c i e s , as the diatom Chaetoceros Heterosigma B.C.  which  akashiwo,  (Pennell,  1988).  and the  convolutus  have • k i l l e d  Current  dinoflagellate  farmed  husbandry  such  salmon  practices  during  blooms of these s p e c i e s , i n c l u d e s c e s s a t i o n of f e e d i n g lowering  of the nets  deeper  i n the water,  in  and  i n the hopes of  keeping the f i s h out of the near s u r f a c e waters, where these blooms g e n e r a l l y occur  (Harrison et , a l . , 1983) .  No p r e v i o u s s t u d i e s on the d i u r n a l p e r i o d i c i t y of water quality  parameters  i n marine  l i t e r a t u r e . This study f i l l s events  and,  research. law in  as  Water  well, quality  study  i n terms  were  found  a  future  the  direction  m o n i t o r i n g programs, benefit  of  in  a gap i n the knowledge of these  indicates  (Anonymous, 1988), may this  net-cages  from  selecting  mandatory  information  the  of by  gained  most a p p r o p r i a t e  time and l o c a t i o n w i t h i n a s i t e f o r sampling. By sampling i n the middle depths least  4 h  of a net-cage, d u r i n g s l a c k water, and at  after  feeding,  ammonia should be  found. DO  the  highest  concentration  of  readings should be taken d u r i n g  s l a c k water, and a l s o over the e n t i r e depth o f the net-cage, preferably  just  before  sunrise,  to  ensure  that  the  most  c r i t i c a l v a l u e s are monitored. Sampling  i n t h i s manner w i l l  provide  the  the  most  m o n i t o r i n g agency.  useful  data  to  both  farmer  and  the  Future water  work  should  include  q u a l i t y i n and around A  conditions. identification components  a fish  time-series of  the  (e.g.  photosynthesis)  analysis  provide  would  of  exchange,  thus  the  considerably  in  investigation  of  daily  the  these  this  husbandry factors  allow  individual  respiration, data  m o d e l l i n g t h e e n v i r o n m e n t a l impact o f f i s h Two s i t e s were v i s i t e d d u r i n g  analysis of  farm under c o n t r o l l e d  periodicity  tidal  and  a time-series  and  needed f o r  farming. study  which v a r i e d  practices.  (e.g. f e e d i n g  Further schedule,  s t o c k i n g d e n s i t y , and f e e d type) i s needed t o determine t h e r o l e t h e y may have i n i n f l u e n c i n g water q u a l i t y . Sampling was performed  i n t h e summer months w i t h t h e  expectation that high seasonal time  o f year  t h e most  increasing metabolic  t e m p e r a t u r e s would make t h i s  deleterious  to fish  r a t e and hence ammonia p r o d u c t i o n .  converse argument i s t h a t lower p h o t o s y n t h e t i c winter  may  allow  concentrations.  dissolved  Future  oxygen t o f a l l  studies should  farms.  The  rates i n the  below  critical  t h e r e f o r e be d e s i g n e d  t o determine whether o r not t h e r e i s a s e a s o n a l water q u a l i t y i n f i s h  i n terms o f  component t o  59 Bibliography  A l a b a s t e r , J.S. and R. L l o y d . 1982. Ammonia. In Water quality criteria for freshwater fish, J.S. A l a b a s t e r , and R. L l o y d [ed.] B u t t e r w o r t h s f o r FAO, London 27 9 pp. Anonymous. 1988. E n v i r o n m e n t a l m o n i t o r i n g program. Manual f o r marine f i s h farms. M i n . E n v i r . P a r k s , Prov. B.C., 40 pp. Anonymous. 1989. 'A good y e a r ' f o r salmon i n B.C. Canadian Aquaculture, 5(2):31. B e v e r i d g e , M. 1984. Cage and f i s h pen f i s h f a r m i n g . F i s h e r i e s T e c h n i c a l paper 255. 131 pp. Black,  FAO  E.A. and B.L. C a r s w e l l . 1986. The impact o f salmon f a r m i n g on t h e marine water q u a l i t y . F i s h . Dev. Pap. 11, 83 pp.  Bower, C.E. and J.P. B i d w e l l . 1978. I o n i z a t i o n o f ammonia i n seawater: e f f e c t s o f t e m p e r a t u r e , pH, and s a l i n i t y . J . F i s h . Res. Bd. Canada, 35:1012-1016. B r e t t , J.R. and C A . Z a l a . 1975. D a i l y p a t t e r n o f n i t r o g e n e x c r e t i o n and oxygen consumption o f sockeye salmon (Oncorhynchus nerka) under c o n t r o l l e d conditions. J . F i s h . Res. Bd. Canada, 32:2479-2486. Caine,  G., J . T r u s c o t t , S. R e i d and K. R i c k e r . 1987. B i o p h y s i c a l c r i t e r i a f o r s i t i n g salmon farms i n B r i t i s h Columbia. A q u a c u l t . Comm. F i s h . Branch, M i n . Agr. F i s h . , P r o v . B.C., 53 pp.  Davis,  J.C. 1975. M i n i m a l d i s s o l v e d oxygen r e q u i r e m e n t s o f a q u a t i c l i f e w i t h emphasis on Canadian s p e c i e s : a r e v i e w . J . F i s h . Res. Bd. Canada, 32 (12) :2295-2332.  DOUBC. 1985. Department o f Oceanography, U n i v . B.C. B r i t i s h Columbia I n l e t s C r u i s e s . Data Rep. 54, 45 pp. DOUBC. 1986. Department o f Oceanography, Univ. B.C. B r i t i s h Columbia I n l e t s C r u i s e s . Data Rep. 55, 53 pp. Emerson, K., R.C. Russo, R.E. Lund and R.V. T h u r s t o n . 1975. Aqueous ammonia e q u i l i b r i u m c a l c u l a t i o n s : e f f e c t o f pH and temperature. J . F i s h . Res. Bd. Canada, 32:2379-2383. E v r i k , A.., P. Johannessen and J . Aure. 1985. E n v i r o n m e n t a l e f f e c t s o f Norwegian marine f i s h farms. ICES C M . 1985/f:37. 13 pp.  60 G l i b e r . t , P.M. and J.C. Goldman. 1981. R a p i d ammonium uptake by marine p h y t o p l a n k t o n . Mar. B i o l . L e t t . 2:25-31. Gowen, R.J. and N.B. Bradbury. 1987. The e c o l o g i c a l impact of s a l m o n i d f a r m i n g i n c o a s t a l w a t e r s : a Review. Oceanogra. Mar. B i o l . Ann. Rev. 25:563-575. Harrison, P.J., J.D. Fulton, F.J.R. T a y l o r , and T.R. P a r s o n s . 1983. Review of the biological oceanography o f the S t r a i t of Georgia: pelagic environment. Can. J . F i s h . Aquat. S c i . 40:1064-1094. H i l l a b y , B.A. and D.J. R a n d a l l . 1979. Acute ammonia t o x i c i t y and ammonia e x c r e t i o n i n rainbow trout (Salmo gairdneri). J . F i s h . Res. Bd. Canada, 36:621-629. H o l e t o n , G.F. 1979. Oxygen as an e n v i r o n m e n t a l f a c t o r of fishes. p. 7-32. In M. A l i (ed.) Environmental p h y s i o l o g y o f f i s h e s . Plenum P r e s s , New York. Inoue, H. 1972. On water exchange i n a net cage s t o c k e d w i t h the fish, hamachi. Bull. Jap. Soc. Scientific F i s h e r i e s . 38 (2) :167-176. ( T r a n s l a t e d from Japanese by Madelon and L o u i s M o t t e t ) . Kennedy, W.A., W. G r i f f i o e n and A. Solmie. 1977. The 1976 crop o f salmon r e a r e d on t h e P a c i f i c B i o l o g i c a l S t a t i o n e x p e r i m e n t a l f i s h farm. F i s h . Mar. Serv. Tech. Rep. 72 6:21 pp. K i l s , U. 1979. Oxygen-regime and a r t i f i c i a l a e r a t i o n o f n e t cages i n m a r i c u l t u r e . M e e r e s f o r s c h 27:236-243. L a n d l e s s , P.J. and A. Edwards. 1976. Economical ways o f a s s e s s i n g hydrography f o r f i s h farms. A q u a c u l t u r e 8:29-43. Lazier,  J.N. 1963. Some a s p e c t s of t h e oceanographic s t r u c t u r e i n the J e r v i s I n l e t system. M.Sc. thesis, department of P h y s i c s . U n i v . British Columbia, Vancouver, B.C., 54 pp.  McLean,  W.E. and F . J . F r a s e r . 1974. Ammonia and urea p r o d u c t i o n of coho salmon under h a t c h e r y c o n d i t i o n s . Dept. Envr., Env. P r o t e c t i o n S e r v i c e and F i s h e r i e s S e r v i c e , Rep. No. EPS 5-PR-74-5, 61 pp.  N i s h i m u r a , A. 1982. E f f e c t s o f o r g a n i c m a t t e r s produced i n fish farms on the growth of red . t i d e algae Gymnodinium type-'65 and Chattonella antiqua. Bull. P l a n k t . Soc. Japan. 29(1):1-7. (In Japanese w i t h E n g l i s h a b s t r a c t and f i g u r e s . )  61 Parsons, T.R., M. T a k a h a s h i , and B. Hargrave. 1984a. Biological Oceanographic Processes 3rd. ed. Pergamon P r e s s , New York. 330 pp. P a r s o n s , T.R., Y. M a i t a , and C M . L a l l i . 1984b. A manual of chemical and biological methods for seawater a n a l y s i s . Pergamon P r e s s , pp.101-104. P e n n e l l , W. 1988. More r e s e a r c h needed on p h y t o p l a n k t o n . Canadian A q u a c u l t u r e , 4 (5) :69-70&78. Perlman, G. 1986. The T h i r d I STAT handbook. Wang I n s t i t u t e of graduate S t u d i e s , Tynosboro, MA 01879 U.S.A. P h i l l i p s , M.J. 1985. B e h a v i o u r o f rainbow t r o u t , Salmo Gairdneri R i c h a r d s o n , i n marine cages. A q u a c u l t . F i s h . Management., 1:223-232. P i c k a r d , G.L. 1954. Oceanography o f B r i t i s h Columbia m a i n l a n d i n l e t s . I I I . I n t e r n a l waves. F i s h . Res. Bd. Can. P a c i f i c P r o g . Rep. No.98, 13-16. P i c k a r d , G.L. 1975. Annual and l o n g e r term v a r i a t i o n s o f deepwater properties i n the c o a s t a l waters of s o u t h e r n B r i t i s h Columbia. J . F i s h . Res. Bd. Canada, 32 :1561-1587. P i c k e r i n g , A.D. 1981. S t r e s s London and New York.  and  Fish.  Academic  Press.  Pond, S. and G.L. P i c k a r d . 1986. I n t r o d u c t o r y Dynamical Oceanography - 2nd. ed. Pergamon P r e s s . Toronto, Canada. 32 9 pp. R a n d a l l , D.J. and P.A. W r i g h t . 1987. Ammonia d i s t r i b u t i o n and e x c r e t i o n i n f i s h . F i s h P h y s i o l . Biochem. 3 (3) : 107-120. R o s e n t h a l , H., D. Weston, R. Gowen and E. B l a c k . 1988. E n v i r o n m e n t a l impact o f m a r i c u l t u r e . ICES C o o p e r a t i v e Research Report 154. 31 pp. R u o k o l a h t i , C. 1988. E f f e c t s of f i s h ' f a r m i n g on growth and c h l o r o p h y l l a c o n t e n t o f Cladophora. Mar. P o l l . B u l l . 19(4):166-169. S u t t e r l i n , A.M., K . J . J o k o l a , and B. H o l t e . 1979. Swimming b e h a v i o u r o f s a l m o n i d f i s h i n ocean pens. J . F i s h . Res. Bd. Canada, 36:948-954. Wee,  W.K._ 1979. V e n t i l a t i o n o f f l o a t i n g cages. M.Sc. t h e s i s . Univ. S t i r l i n g , U.K. 38 p p . ( e x c l u d . t a b l e s and figs.)  62  Weitkamp, D.E. and M. K a t z . 1980. A r e v i e w o f d i s s o l v e d gas s u p e r s a t u r a t i o n l i t e r a t u r e . Trans. Amer. F i s h . Soc. 109:659-702. Weston, D.P. 1986. The e n v i r o n m e n t a l e f f e c t s o f f l o a t i n g m a r i c u l t u r e i n Puget Sound. Wash. Dept. F i s h , and Wash. Dept. E c o l . 148 pp. W i l l i a m s , P . J . LeB., R.C.T. Raine and J.R. Bryan. 1979. Agreement between t h e C and oxygen methods o f measuring p h y t o p l a n k t o n p r o d u c t i o n : reassessment o f the p h o t o s y n t h e t i c q u o t i e n t . Oceanologica Acta 2 (4) :411-416. 1 4  

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