Variability in daily ration estimates of age-0 striped bass in the Chesapeake Bay

Previous studies have developed and applied bioenergetics models to estimat e trophic demand for prey by striped bass Morone saxatilis in Chesapeake Ba y. Although these models were validated with laboratory studies, no field e stimates of daily ration of striped bass were available in Chesapeake Bay f or comparison with bioenergetics model estimates. This study estimated grow th and daily ration of age-0 striped bass in the upper Chesapeake Bay for t wo dates (6 acid 19 October 1993) using the Eggers model. Experiments on th e gastric evacuation rate of captive striped bass at 17 degreesC found that stomach contents were evacuated at a rare of e(-0.12)h, where h is time in hours since feeding. Daily ration estimates only 14 d apart varied by 66% (0.0326 g . g(-1) (.) d(-1) on 6 October and 0.0542 g . g(-1) d(-1) on 19 O ctober). Bioenergetics model estimates of consumption over this period aver aged 0.0559 g (.) g(-1) d(-1). Based on the variability in Eggers estimates , it would require more than two estimates (2.4) of daily ration over this period to estimate consumption to within 25% of the parameter with 95% conf idence. However, the bioenergetics model estimate of consumption was within 25% of the average of the Eggers estimates and required significantly less effort to obtain. This study suggests that if bioenergetics models are rea sonably corroborated in the field or laboratory, they can provide reasonabl e estimates of consumption by fish from data commonly collected during fish eries surveys (weight at age, diet), with little additional information (en ergy content, temperature) and much less effort than daily ration estimates of consumption.