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The life history and distribution of lampreys in the Salmon and certain other rivers in British Columbia, Canada Pletcher, Ferdinand Tony

Abstract

The analysis of the life history was carried out from collections that were predominantly Lampetra planeri from the Salmon River and Entosphenus tridentatus from the Nicola and Thompson Rivers and from Vancouver Island streams. The taxonomy of British Columbian lampreys is reviewed and characteristics determined for separating large ammocoetes. The duration of adult life, distribution within streams, length, sex ratio, and fecundity was determined for both species. The spawning behaviour of both species is described from field and laboratory observations. Temperature affected length of spawning period, spawning behaviour, sex ratio, and relative abundance of L. planeri. Hatching of lamprey eggs was dependent on temperature and differed between the two species. Newly hatched ammocoetes emerged from the gravel nests during darkness, were carried downstream by the current and were deposited in mud beds of quiet pools where they buried. The bottom preference of small ammocoetes was mud> gravel> sand and was reflected in field distributions where greatest concentrations of ammocoetes were found in mud bottoms. The greatest concentration of ammocoetes of mixed age classes was in the deep pool ammocoete beds with sand, leaf, and silt bottoms. Ammocoetes kept in aquaria moved their burrows frequently. Ammocoete intestines contained predominantly diatoms whose abundance corresponded to the season of most rapid ammocoete growth. Adult and ammocoetes were not eaten by salmonid and other fishes of the SalmonRiver possibly because of a protective substance in their skin. Transformation to adults for both species occurred in the fall after at least five years of ammocoete life. Probability paper was used to analyse length-frequency distribution and to construct growth curves. The growth curves of both species was very similar and nearly linear. The average length of life cycle for L. planeri was six years or more and that of E. tridentatus was seven years or more. Adult E. tridentatus parasitized trout in Elsie and Cowichan Lake to the greatest degree during the early spring and attacked salmon and other fish in the sea during the summer months.

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