Catch-at-age analysis for yellow perch in Oneida Lake

Population abundance of yellow perch in Oneida Lake was previously estimated using standard gillnet catches or mark-recapture population experiments.  However, due to a decline in the yellow perch population beginning in the 1990’s and an alteration of the lake ecosystem, these methods are no longer possible (mark-recapture) or as reliable due to low capture numbers in recent decades.  Here we present a catch-at-age model which combines all sources of information for yellow perch available from 1969-2007.  Three data sets (gillnet, bottom trawl, mark-recapture) from standardized sampling were combined and densities by age and year, catchability, and mortality by age were estimated for yellow perch using AD Model Builder.  The model produced similar adult density results as previous methods; however the trawl catchability estimate was larger than expected.  Mortality estimates were different among age classes (1-6+).  The choice of data sets, and their subsequent weighting in the model, affected the estimated parameters and should be carefully considered when selecting information to use within catch-at-age models.   Combining all reliable data provides a way to gain information on all age classes and relate parameter shifts to changes in the system.