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Size‐Dependent Mechanisms Influencing First‐Year Growth and Winter Survival of Stocked Striped Bass in a Virginia Mainstream Reservoir
Author(s) -
Sutton Trent M.,
Ney John J.
Publication year - 2001
Publication title -
transactions of the american fisheries society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.696
H-Index - 86
eISSN - 1548-8659
pISSN - 0002-8487
DOI - 10.1577/1548-8659(2001)130<0001:sdmify>2.0.co;2
Subject(s) - biology , bass (fish) , predation , stocking , piscivore , fishery , alewife , serranidae , zoology , ecology , fish <actinopterygii> , predator
To explain the limited stocking success of fingerling striped bass Morone saxatilis in Smith Mountain Lake, Virginia, we examined the relationship between size‐selective winter survival and length‐dependent patterns in growth, food habits, prey fish availability, and lipid energy reserves during the first year of life in two successive years from 1994 to 1996. Length distributions of striped bass were unimodal at the time of stocking, and growth remained positive for all fish during both growing seasons. By the fall of both years, a bimodal length distribution had developed within the age‐0 cohort, which then consisted of small‐mode (<150 mm) and large‐mode (>180 mm) fish. The differential growth was attributed to size‐dependent differences in prey consumption and diet quality. Small‐mode striped bass maintained a mixed diet of invertebrates and small cyprinids, whereas fish in the larger mode were strictly piscivorous, consuming only age‐0 alewives Alosa pseudoharengus. The disparity in food habits, which was probably influenced by the limited availability of alewife prey to smaller striped bass, resulted in size‐dependent differences in physiological condition, as larger juveniles amassed twice the lipid index levels as smaller fish by winter. By spring of both years, the bimodal length distribution had become unimodal and comprised almost entirely large‐mode striped bass. In addition, large‐mode fish had retained approximately 80% of their fall lipid stores, whereas surviving small‐mode individuals had retained only 40% of fall lipids. These results suggest that depletion of lipid energy, possibly coupled with other size‐dependent stressors, may explain the greater winter mortality of small fish. Stocking fingerling striped bass in Smith Mountain Lake at a larger size and earlier in the growing season should result in a greater proportion of stocked fish successfully switching to age‐0 alewife prey, thereby improving first‐year growth, winter survival, and recruitment to age 1.