We propose to empirically characterize hydrology/fish-production relationships for different ecological groups of fishes living in the Red River and associated reservoir habitats by: 1. Correlating historic hydrologic data with catch curve residuals, and 2. Annual growth rate estimates of fish collected from the Red River and associated reservoirs. The catch curve residual approach for indexing year class strength has been validated and successfully used to quantify the relationship between reservoir hydrology and YOY recruitment for white crappie and largemouth. The essence of the approach is as follows. Catch curves (a correlation between the natural log of fish abundance and age) are used to measure total instantaneous mortality (i.e., the slope from the catch curve). Deviations from the catch curve regression line can be attributed to weaker (negative residuals) or stronger (positive residuals) year classes. As such, catch curve residuals are a standardized and implicit measure of recruitment variation (whether caused by a different number of spawning individuals or a difference in first-year survival). Therefore, this approach can be used to obtain information about recruitment variability for numerous year classes simultaneously. These residuals, or estimates of year class strength, can then be correlated with environmental conditions during the cohorts birth year, provided there is historic data concerning environmental conditions dating back to the birth year of the oldest fish sampled.
