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-ofthe-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 t 0 = -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 weightlength 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.

The Effects of Spatial and Temporal Resolution in Simulating Fish Movement in Individual‐Based Models

“…The maximum growth rate was 5 £ 10 ¡4 mm/min, which was five times the average growth rate of 0.07 mm/d reported for Bay Anchovy (Lapolla 2001). The realized growth rates in model simulations were much lower than the maximum and were comparable to the observed averages because few cells in the model environment allowed for maximum growth (i.e., most values of G c,r were < 1.0).…”

“…The maximum mortality rate was 4.2 £ 10 ¡5 per minute, which was five times the average annual mortality rate of 2.17 reported for Bay Anchovy (Lapolla 2001). As with growth, the realized mortality rates in simulations were comparable to observed averages because model individuals rarely experienced maximum mortality.…”

“…Length (mm) was converted to weight in grams (W i [t]) according to the following allometric relationship: W D (2 £ 10 ¡6 )¢L 3.38 . The initial size and the length-weight relationship were roughly based on values for Bay Anchovy (Lapolla 2001;Bassista and Hartman 2005).…”

Geographic variability of sardine growth across the northeastern Atlantic and the Mediterranean Sea

“…However, differences in sardine length-at-age between recruitment areas such as south Biscay, north Portugal and the Gulf of Cadiz-north Morocco cannot be explained by migration. Instead, these differences suggest a latitudinal gradient in growth across the northeastern Atlantic, as observed for several temperate fish species, including clupeoids (Conover and Present, 1990;Lapolla, 2001). Latitudinal growth trends may have a genetic basis (countergradient growth variation; Conover and Present, 1990) as a consequence of selection pressures related to temperature seasonality and winter survival (Conover, 1992); increased juvenile growth enables populations to sustain longer, colder and often resource-poorer winters at higher latitudes and large body size increases the ability to store energy to reproduce in the beginning of the next growing season.…”

Sex ratio and sexual dimorphism of the anchovy Anchoa januaria (Actinopterygii, Engraulidae) in a tropical bay in south‐eastern Brazil

“…Newberger & Houde (1995) reported that sex ratios for this species are not well understood. Unbalanced sex ratios (female or male favoured) have been found in other engraulids, although there is no clear explanation for this phenomenon (Lapolla, 2001). The regional fluctuation of sex ratio in engraulids may relate to their physiological state: either the spawning period on one side and the inactivity period of the sexual cycle on the other (Sinovcic, 2000).…”