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|Title:||Growth rates and year-class strength of selected fishes as related to stage and discharge of the Lower Mississippi River|
|Authors:||Louisiana State University (Baton Rouge, La.). School of Forestry, Wildlife, and Fisheries.|
Louisiana Cooperative Fish and Wildlife Research Unit.
Lower Mississippi River Environmental Program.
Rutherford, D. A.
Kelso, William E.
Constant G. C.
Bryan, C. Fred (Charles Fred)
Cobb, Stephen P.
|Publisher:||United States. Mississippi River Commission.|
Engineer Research and Development Center (U.S.)
|Series/Report no.:||Lower Mississippi River Environmental Program report ; 20.|
Abstract: Growth and year-class strength of four commercially important fishes (lctalurus furcatus, I. punctatus, Aplodinotus grunniens, and Dorosoma cepedianum) collected, from dike system pools during September and October 1987-1990 on the Lower Mississippi River (LMR) were examined. The objectives were to examine the relationships between year-class strengths and the growth history of each species and 19 physicochemical characteristics of the LMR. The determination of age-class structure and growth was made using various calcified structures from individual fishes subsampled in 1989 and 1990. Age and length relatiooships were used to assign age-class membership, and from this mean cohort densities were calculated across dike system pools within years. For each cohort, analysis of variance (ANOVA) was used to detect pairwise differences in abundance and differences in mean annual growth increments. ANOVA was also used to examine the relationships between each of the 19 physicochemical variables and both mean annual cohort densities and mean annual growth increments for cohorts. Age-0 abundances of blue catfish in 1989 and 1990 were significantly higher than in 1987 and 1988. A significant proportion of the variation in age-0 blue catfish abundance across years was explained by five physicochemical variables: discharge, number of days over bank, river stage, dissolved oxygen concentration, and total Kjeldahl nitrogen conceattation. The 1987 cohort of freshwater drum was significantly less abundant than that of the 1988 cohort, but neither year was significantly different from the intermediate year classes in 1989 and 1990. The number of clays over 16°C and the concentration of total organic carbon explained a significant proportion of the varialion in age-0 freshwater drum abundance across years. Growth increments from 1,573 individuals to assess differences in growth between years for age-0 and -1 blue catfish; age-0, -1, and -2 freshwater drum; age-0 channel catfish; and age-0, -1, and -2 gizzard shad were examined. There were no significant differences in age-0 growth increments for blue catfish in 1986 and 1988, but growth in these 2 years was significantly higher than in 1987 and 1989. The growth pattern of age-1 blue catfish resembled age-0 fish, with growth in 1988 being significantly higher than age-1 growth in 1987 and 1989. Age-0 incremental growth for channel catfish was similar to blue catfish, with significantly greater growth in 1988 relative to 1987, and growth increments for both catfishes were significantly related to the length of the growing season. In addition, growth of age-1 blue catfish was negatively associated with turbidity and positively associated with total organic carbon levels. Growth of age-0 and -1 freshwater drum was similar over the years examined with the exception of 1988. Growth in 1988 for both age classes was significantly higher than other years. Age-0 and -1 growth was negatively associated with several variables related to the quantity of water in the river: discharge, days over bank, mean river stage, and (age-1 fish only) extent of overbank flooding. Age-2 freshwater drum grew slower in 1986 than in 1988 and 1989, but growth was not significantly related to measured physicochemical variables. Growth of gizzard shad was variable, and. the patterns of growth across years were different for the three age classes. For age-0 shad, growth was significantly lower in 1984 than from 1985-1988 and was positively associated with river temperatures over 12°C. Age-1 gizzard shad exhibited significantly lower growth in 1985 than in 1987, and growth was negatively related to the duration and areal extent of overbank flooding. Growth patterns of age-2 fish resembled those of catfishes and drum, with significantly higher growth in 1988 than in 1986 and1989. However, there were no significant associations between river physicochemistry and growth of age-2 gizzard shad. Growth of age-0 and -1 blue catfish, age-0 channel catfish. and age-0 gizzard shad was positively associated with length of the growing season. Relationships between age-1 blue catfish growth and turbidity (negative) and total organic carbon levels (positive) may reflect growing conditions in the river during higher and lower water years, respectively. The negative relationships between age-0 and -1 drum and age-1 shad growth and river discharge associated variables suggest that these fishes forage most efficiently in low flow conditions. Overall, there appear to be two general responses to growth, one related to length of the growing season and one retated to discharge.
|Appears in Collections:||USACE Collection|