Reproduction, population structure, and recruitment limitation in a bay scallop (Argopecten irradians Lamarck) population from New Jersey, USA

A bay scallop, Argopecten irradians irradians (Lamarck 1819), population wa s studied in Little Egg Harbor, New Jersey, USA to investigate the distribu tion, reproduction and genetic structure of the population because virtuall y nothing is known about this species in this region. Argopecten irradians irradians densities varied among eelgrass (Zostera marina Lamarck) beds in 1998 (range 0.12-1.0 individuals per 10m transect), but were virtually abse nt from the region in 1999. The absence of adults in 1999 may have been due to limited spat recruitment and survival in the fall of 1998, which may be attributed to a reduction in above ground biomass of Z. marina habitat. Ge netic analysis (using mtDNA) indicated that this New Jersey population was intermediate between New York and North Carolina populations, Based on thes e data and the historical landings of bay scallops in New Jersey, it is pro bable that a small self-seeding Population exists. Assessment of reproducti ve cycles during 1998 showed two potential peaks in reproductive condition: one occurred during June when a maximum Gonadal-Somatic Index was recorded (24.7%) and the second was during October when a visual gonadal condition index indicated a majority of scallops in post-spawn condition. Few adult b ay scallops were encountered in 1999 (n = 8) to assess reproductive cycles, but two large individuals collected during July showed a post-spawn gonada l condition. However, during both 1998 and 1999 settling juveniles (< 15 mm shell height) were only recorded in October, suggesting that recruitment t o the population during these years resulted from the late summer-early fal l spawn. Given the variability observed over the two years, future studies should concentrate on factors influencing inter-annual variation in abundan ce of this New Jersey population.