Bay anchovy Anchoa mitchilli in Narragansett Bay, Rhode Island. I. Population structure, growth and mortality

Abstract

Population structure, growth and mortality of Anchoa mitchilli were evaluated in Narragansett Bay (Rhode Island, USA), an estuary near the northern extent of this species' broad latitudinal range. The Narragansett Bay population was dominated by young fish (Age 1 and young-of-the-year, YOY); no fish were found to have survived a third winter. Growth rates were rapid, particularly during the first year of life, and annual mortality rates were estimated at >90 %. A von Bertalanffy growth model fit to length-at-age data yielded parameters of asymptotic length L∞ = 89.97, growth coefficient K = 1.15 and age at zero length t0 = -0.31. Comparison of my results to those of an earlier study from Chesapeake Bay suggests that Narragansett Bay anchovies grow more rapidly during the first year of life, and subsequently attain a greater length-at-age, than their conspecifics at lower latitudes. Latitudinal differences are also indicated by comparison of the weight-length relationships and Fulton's condition factors of Narragansett Bay and Chesapeake Bay data. Narragansett Bay fish seem to be allocating energy preferentially to length versus weight compared to fish in Chesapeake Bay, which may be a reflection of this species' growth strategy at this latitude.