EXPERIMENTAL TESTS OF FACTORS AFFECTING RECRUITMENT OF BAY SCALLOPS (ARGOPECTEN-IRRADIANS) TO SPAT COLLECTORS

Spat collectors, mesh bags enclosing plastic screen as settlement substratum, were suspended at nine sites in North Carolina to test effects of different mesh materials and proximity of collectors to spawning adults on the collection of bay scallop, Argopecten irradians, spat. Collectors were deployed inside and at two different depths in the water column outside seagrass beds to determine the optimal location for collecting scallops. Recruitment (settlement and subsequent survival) was greater onto 3-mm transparent polypropylene mesh screen than onto 4-mm black mesh, probably because the 3-mm mesh had more than twice the surface area available for settlement. Tripling the amount of 4-mm mesh (and therefore total surface area) also increased numbers of recruits collected, further suggesting that surface area of the settlement substratum is an important determinant of scallop recruitment. Recruitment was greatest to spat collectors located near the bottom and outside of seagrass beds. Patterns of recruitment to different meshes were identical to those of settlement and recruitment to the same substrata in a concurrent laboratory study, indicating that, for the range of scallop densities studied, recruitment to spat collectors is a good reflection of settlement pattern and may be used as a reliable index of relative settlement intensity. While recruitment was high at a few locations with low abundances of adult spawners, collectors at sites with high adult abundances always received high numbers of recruits.