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Factors Affecting Abundance, Growth, and Survival of Age‐0 Gizzard Shad
Author(s) -
Michaletz Paul H.
Publication year - 1997
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(1997)126<0084:faagas>2.3.co;2
Subject(s) - gizzard shad , dorosoma , abundance (ecology) , biology , larva , fecundity , otolith , ecology , zoology , fishery , population , demography , fish <actinopterygii> , predation , sociology
Factors affecting abundance, growth, and survival of age‐0 gizzard shad Dorosoma cepedianum were examined in Pomme de Terre and Stockton lakes, Missouri, during 1987–1991. Otolith ages were used to assign larvae (≤25 mm total length, TL) and juveniles (>25 mm TL) to weekly cohorts so that cohort‐specific estimates of abundance, growth, and survival could be made. The distribution of initial abundances of larvae among weekly cohorts was influenced by water temperature and reservoir water level but not by characteristics of adult females (abundance, size, condition, fecundity). Intense periods of spawning activity during rising water levels resulted in high peaks in larval abundance and relatively few large weekly cohorts (e.g., 1990). In the absence of water level rises, peaks in larval abundance were much lower and abundances of larvae were more evenly distributed among several cohorts (e.g., 1988). Spring warming also affected spawning; early cohorts in warm springs (1987 and 1991) were relatively more abundant than those during cool springs (1989 and 1990). The initial distribution of larvae among weekly cohorts influenced subsequent interactions between the larvae and their environment. Growth of larvae was positively affected by water temperature and, to a lesser degree, food abundance. Early cohorts grew slower because of lower water temperatures, and they suffered higher mortality than did late cohorts. Survival was also density dependent; weekly cohorts with high initial densities experienced lower survival than cohorts with small initial densities. High survival of larvae occurred in 1988 when densities of larvae were low and evenly distributed among weekly cohorts and food abundance was high. Growth and instantaneous mortality of juveniles were not closely tied to any single variable. Growth was positively related to food abundance and negatively related to gizzard shad density. Mortality was not significantly related to any measured variable. Overall, findings indicate that cohort dynamics of age‐0 gizzard shad are initially driven by climatic factors and later by a combination of climatic and biotic factors.