Foraging behaviour and perceived predation risk of juvenile chinook salmon (Oncorhynchus tshawytscha) in turbid waters
department or school: Science, Faculty of
department or school: Zoology, Department of
data provider: DSpace
degree campus: UBCV
creator: Gregory, Robert S.
issued: 2011-01-29T01:59:49Z
issued: 1991
related degree: Doctor of Philosophy - PhD
degree grantor: University of British Columbia
description: I investigated the effect of turbidity on the foraging behaviour of juvenile Chinook salmon (Oncorhynchus tshawytscha) in the laboratory. Specifically, I examined a behavioural "tradeoff" between visual ability and "perceived" risk. I assessed visual ability by measuring the reaction distance of juvenile Chinook to planktonic Artemia prey. I found Chinook exhibited a log-linear decline in reaction distance with increasing turbidity. To determine the effects of turbidity and microhabitat on foraging rate, I conducted separate experiments for surface (Drosophila), planktonic (Artemia), and benthic (Tubifex) prey across a range of turbidity levels (0, 25, 50, 100, 200, 400, 800 mg•L⁻¹). Foraging rates were reduced at higher turbidity conditions for all three prey. However, for surface and benthic prey, foraging rates were also low in clear water; highest rates were attained at intermediate turbidity levels (50-200 mg•L⁻¹). The degree to which intermediate turbidities were associated with higher foraging rates was size-dependent. Smaller individuals (150-57 mm FL) exhibited relatively higher foraging rates in clear conditions than did larger individuals. However, planktonic foraging rates by juveniles were consistently high in clear water, regardless of fish size. In experiments manipulating light level independent of turbidity, I allowed salmon to forage under conditions which were either turbid, or clear but with light intensity correspondingly reduced. Foraging rates were similar between the two treatments for planktonic prey, but differed for benthic and surface prey. Generally, foraging rates exhibited by juvenile Chinook salmon could not be explained on the basis of visual ability alone. I suggest that young salmon also exhibited foraging behaviour consistent with their perception of risk to predation. In arena experiments, juvenile Chinook distributed themselves randomly in turbid conditions; in clear conditions they associated with the bottom. When bird and fish…
aggregated CHO: https://circle.library.ubc.ca/rest/handle/2429/30976
note: FORAGING BEHAVIOUR AND PERCEIVED PREDATION RISK OF JUVENILE CHINOOK SALMON (ONCORHYNCHUS TSHAWYTSCHA) IN TURBID WATERS. by ROBERT S. GREGORY BSc(Honours Biology) Acadia University 1980 MSc(Biology) Trent University 1984 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE STUDIES (Department of Zoology) We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA February 1991 © Robert S. Gregory 1991 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 be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of Zoology The University of British Columbia Vancouver, Canada Date A p r i l 22, 1991 DE-6 (2/88) ii ABSTRACT I investigated the effect of turbidity on the foraging behaviour of juvenile Chinook salmon (Oncorhynchus tshawytscha) in the laboratory. Specifically, I examined a behavioural " t radeoff " between visual ability and "perceived" risk. I assessed visual ability by measuring the reaction distance of juvenile Chinook to planktonic Artemia prey. I found Chinook exhibited a log-linear decline in reaction distance with increasing turbidity. To determine the effects of turbidity and microhabitat on foraging rate, I conducted separate experiments for surface (Drosophila), planktonic (Artemia), and benthic (Tubifex) prey across a range of turbidity levels (0, 25, 50, 100, 200, 400, 800 mg-L-1). Foraging rates were reduced at higher turbidity conditions for all three prey. However, for surface and benthic prey, foraging rates were also low in clea…
has type: Thesis/Dissertation
is shown at: 10.14288/1.0100583
language: eng
degree discipline: Zoology
provider: Vancouver : University of British Columbia Library
publisher: University of British Columbia
rights: For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
scholar level: Graduate
type: Text
identifier URI: http://hdl.handle.net/2429/30976