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The distribution and production of Gammarus pseudolimnaeus (Crustacea: Amphipoda) along a reach of the Credit River, Ontario
Author(s) -
MARCHANT R.,
HYNES H. B. N.
Publication year - 1981
Publication title -
freshwater biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.297
H-Index - 156
eISSN - 1365-2427
pISSN - 0046-5070
DOI - 10.1111/j.1365-2427.1981.tb01251.x
Subject(s) - amphipoda , gammarus , crustacean , population density , voltinism , zoology , population , biology , ecology , environmental science , fishery , larva , demography , sociology
SUMMARY. The population density of the univoltine amphipod Gammarus pseudolimnaeus was estimated monthly from April 1977 to June 1978 along a 600‐m reach using a form of removal sampling at 0.5, 1.5 and 2.5 m from the bank. The probability of catching an amphipod with three sweeps over an area of 0.15 m 2 was 0.95. Drift and upstream migration were measured for 24 h, also monthly. Population density varied from 1600 m −2 (newly‐hatched young in July) to 26 m −2 (adults) within 3 m of the bank with 95% confidence limits of 40–60% of the mean; density was highest < 1 m from the bank and beyond 3 m it declined to insignificant levels. No significant difference could be shown between the total catches in the drift and upstream nets over a year and there appeared to be no net migration of amphipods. Mean drift was 2 amphipods day −1 . Growth was estimated from the length composition of monthly samples. Annual production ( P ) was 29.4 kg ha −1 for one generation of the amphipod with a P/B ratio of 4.65. Egg production accounted for only 2% of this estimate. Recruitment was calculated from regressions relating female length to clutch size and egg development time to temperature in the laboratory; mean temperature was measured in the field. Mortality was greatest in July at the beginning of the generation. It was high again in September and during winter; at these later times it was suggested that starvation occurred in addition to predation. Annual consumption ( C ) of organic matter for the generation calculated from published data on feeding rate was 1547 kg ha −1 which results in a P/C ratio of 1.9%.