Effects of a reduced subsampling protocol on calculation of growth and body condition indices

Abstract

The impact of a reduced subsampling protocol on growth and body condition calculations was examined for bluegill, white, and black crappie. A maximum of 5 fish per 10-mm length group were randomly subsampled from 9 years of survey data collected under a maximum of 10 fish per 10-mm length group subsampling protocol (referred to as P10). The new protocol (referred to as P5) reduced age and growth subsample size by an average of 26, 23, and 21 fish for bluegill, white, and black crappie surveys, respectively. Significant relationships were observed between P5 and P10 results for mean length-at-age (MLA), coefficients of variation associated with MLA (CV), Von Bertlanffy growth constants (K), mean relative weight for stock-length and greater fish (Wr-S), and CV values associated with Wr-S. Estimates of MLA were statistically different between P5 and P10 designs for all species, however, the differences were 3 mm or less in 90% or more of the time. Based on the results of this study, reducing the stratified subsampling protocol from a maximum of 10 fish to a maximum of 5 fish per 10-mm length group would have minimal effect on fishery management decisions based on standard growth and body condition parameters for these three species in Nebraska.