The effects of abiotic and biotic factors in determining larval fish growth rates: A comparison across species and reservoirs

Understanding the processes that underlie larval fish growth are important in predicting recruitment. However, the factors and mechanisms that influen ce early life stages of fishes are complex and not well understood. We eval uated the role of several abiotic and biotic factors in determining larval fish growth rates across 21 Illinois reservoirs. Larval crappies Pomoxis sp p., sunfish Lepomis spp, and gizzard shad Dorosoma cepedianum were collecte d by push nets from May through July in 1995. Lakes were classified based o n morphometric, limnological, and biotic variables using principal componen ts analysis (PCA). In general, the abiotic variables loaded highest in PCA and explained the most variation across reservoirs. The relationships betwe en larval fish growth, using otolith daily rings, were then examined with t he principal components and by multiple regression. Larval fish growth rate s were highly variable across reservoirs. Mean growth was lowest, but the r ange of growth rates were highest for crappie and bluegill; growth rates of larval gizzard shed were higher but less variable across reservoirs. Abiot ic variables such as latitude, lake temperature, and characteristics of lak e size were important in explaining growth for all three species. The relat ionships between larval fish growth rates and biotic variables, such as zoo plankton and larval fish densities, were more species specific. By comparin g across a number of reservoirs with a multivariate approach, we were able to generate an understanding of the complex interactions between abiotic an d biotic variables that influence larval fish growth rates.