Using Hard-part Increment Data to Estimate Age and Environmental Effects

Fish grow in response to the extrinsic effects of their biotic and abiotic environment and in accordance with the intrinsic effects of size or age already attained. In this paper, a family of linear models are proposed that assume that growth, as reflected in increments in scales or other bony structures, can be divided into intrinsic age or size effects and external environmental effects. The models presented are of varying complexity. Some of the models use data from annular rings on bony parts, some use length or size attained, and some use both. Generalization to nonlinear or generalized linear models is indicated. Methodology for comparing subsamples of fish, based on sex, condition, trapping method, or any other identifiable characteristic, is discussed. The models are applied to several samples of smallmouth bass (Micropterus dolomieu) collected during 1988–90.