Length, Body Depth, and Gape Relationships and Inference on Piscivory Among Common North American Centrarchids

Species of Centrarchidae are major components of inland fisheries in much of North America. Thus, information gained from the assessment of interspecies interactions and/or quantifying predator-prey relationships is a useful tool for fisheries managers. Using preserved fish specimens (n = 717) from 20 species of centrarchids, we made measurements of total length (TL), standard length (SL), horizontal gape, and body depth for each individual. We fitted mathematical models that included horizontal gape and body depth as functions of TL and SL, and TL as a function of SL. Linear-regression-model fits were generally good (r(2) = 0.764-0.998) for all 20 species. with 61 of 78 possible models having r(2) values exceeding 0.90. Horizontal gape-SL (F-3,F-702 = 77.18, P < 0.001) and body depth-SL (F-3,F-702 = 91.79, P < 0.001) ratios differed significantly along a gradient that reflected the species' likelihood of piscivory. Slopes of TL-SL regressions did not vary by species, which enabled development of a generalized TL-SL model for centrarchids. Supplemental analyses supported that morphometric measurements had not been influenced significantly by preservation. Results of this study are useful to fisheries managers involved with understanding species interactions within centrarchid-dominated food webs, which are of high priority in most fisheries-management plans.