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 supply. 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 correlated 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 following the 1995 brown tide and that resurgent recruitment was driven, initially, by our intensive restoration 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.

Connectivity of the bay scallop (Argopecten irradians) in Buzzards Bay, Massachusetts, U.S.A.

“…Field studies on bay scallop larval settlement in other parts of the eastern U.S.A. suggest that tidally‐induced circulation is the dominant mechanism of larval transport (Peterson et al ., ; Arnold et al ., ; Marko and Barr, ; Tettelbach et al ., ) whereas the wind‐driven circulation is not significant (Peterson et al ., ; Tettelbach et al ., ). This was also an inherent assumption of the Lagrangian particle tracking study on bay scallop larvae conducted by Siddall et al .…”

Hard clam walking: Active horizontal locomotion of adult Mercenaria mercenaria at the sediment surface and behavioral suppression after extensive sampling

“…Fertilization success in many species is dependent on both population density and population size [21,22,24,66] and thus the largest proportional benefit of aggregating to increase fertilization success should theoretically occur at very low population densities. However, Allee effects (see below) may negate such potential benefits.…”

The recruitment of scallops (and beyond) by two different artificial collectors (Gulf of Taranto, Mediterranean Sea)

“…Data from the literature reported as potential drivers of recruitment, the local site conditions, seasonality, hydrodynamics, proximity to wild parental stock and time of collector's immersion (Narvarte ; Orensanz, Parma, Turk & Valero ; Avendaño et al . , ; Tettelbach, Peterson, Carroll, Hughes, Bonal, Weinstock, Europe, Furman & Smith ). There are several possible explanations for the relatively low recruit density recorded in this study, such as the mortality caused by predation and the excessive fouling developed on the collectors due to the extended period of immersion (7 months).…”