Priming the larval pump: resurgence of bay scallop recruitment following initiation of intensive restoration efforts

Abstract

Bay scallop Argopecten irradians irradians populations and fisheries in the Peconic Bays of eastern Long Island, New York, USA, were decimated by brown tide algal blooms between 1985 and 1995. Despite the absence of brown tide since 1995, populations did not recover on their own over the next 11 yr. We hypothesized that this was due to recruitment limitation and initiated an intensive restoration program to jump-start populations by planting several million hatchery-reared scallops at high densities to ensure high fertilization success and boost larval sup- ply. We observed 11- to 32-fold increases in larval recruitment in different embayments by 2010, compared to the period 2005 to 2006 (before intensive restoration); the most dramatic increase (3239%) occurred in Orient Harbor, the focus of restoration efforts. Recruitment was highly corre- lated with our index of total fertilized egg production in Orient Harbor and Hallock Bay, but not in 2 other embayments—where larval export or population overestimation probably compromised the correlation. Resurgent recruitment following restoration was not correlated to coincidental changes in adult fecundity, water temperature, salinity, rainfall, chlorophyll a, total particulate nitrogen, or local winds; decreased planktonic predation and allochthonous larval infusion were deemed unlikely drivers. We conclude that Peconic bay scallops were recruitment-limited follow- ing the 1995 brown tide and that resurgent recruitment was driven, initially, by our intensive res- toration efforts and later by the rebuilding natural populations. Sustained restoration, conducted with high scallop numbers/densities, may help boost natural populations above threshold levels at which they become self-sustaining.