CORRELATED VARIATIONS IN ABUNDANCE, SIZE, GROWTH, AND LOSS RATES OF AGE-O BLUEFISH IN A SOUTHERN NEW-ENGLAND ESTUARY

Age-0 bluefish Pomatomus saltatrix were widely distributed and seasona lly abundant in shallow beach habitats of Narragansett Bay, Rhode Isla nd. Based on length-frequency data that were polymodal in some years, these age-0 fish comprised spring- and summer-spawned cohorts. Cohort- specific measures of abundance, growth, total mortality and emigration , and size were determined for 1982-1992. In all years, spring-spawned fish dominated the catch from at least July to September. For this co hort, annual abundance varied by an order of magnitude, growth ranged from 0.9 to 2.1 mm/d, total mortality and emigration rates were betwee n 0.2 and 2.8%/d, and mean length on October 1 ranged from 164 to 248 mm fork length. Spring-spawned fish were about twice as large as summe r-spawned fish by October, Summer-spawned fish also occurred less freq uently and in lower abundance. These findings confirm that Narraganset t Bay is an important nursery for bluefish, and that the trend toward declining annual abundance measured in this bay is concordant with the reported decline of bluefish throughout the western Atlantic. Correla tion analysis with data for only the spring-spawned cohort suggested d ensity-dependent (i.e., compensatory) processes occurred; growth decre ased monotonically but not linearly, relative to abundance, whereas co mbined mortality and emigration rates increased linearly. Measures of abundance were also a function of seine-net size; seines less than 25 m long were particularly ineffective for collecting age-0 bluefish. Th ese relationships suggest that monitoring age-0 fish in estuaries may help predict future population size.