Estimating growth and mortality of juvenile winter flounder, Pseudopleuronectes americanus, with a length-based model

Abstract

This study quantifies the combined effects of density and environmental factors on young-of-the-year (YOY) winter flounder (Pseudopleuronectes americanus) in Narragansett Bay, Rhode Island. We used a length-based model to estimate growth and mortality rates from June to October each year from 1988 to 1998. In this model, mortality and growth rates are decreasing functions of length and there is variability in individual growth. Maximum-likelihood methods were used to fit the model to length-frequency data collected by the Rhode Island Division of Fish and Wildlife beach-seine survey in Narragansett Bay during the study years. The monthly mortality rate was density dependent and was positively related to temperature. Growth rate was negatively related to density. There was a significant decline in YOY winter flounder abundance during the period of study. The most recent year of the study, 1998, had the lowest density, lowest mortality, low summer temperature, and high growth rate. Thus, growth and mortality during the juvenile stage do not appear to be limiting the recovery of this depleted winter flounder population.