Intensive efforts to restore bay scallop Argopecten irradians irradians populations and fisheries in the Peconic Bays of eastern Long Island, New York, USA, were begun in 2006, following a 12 yr period during which commercial fishery landings averaged 1 to 2% of historical levels seen prior to 1985 to 1995 brown tide algal blooms. Compared to 2005 to 2006, natural population densities of 0+ yr scallops in fall increased 16 × by 2007 in Orient Harbor (OH), the focus of our restoration efforts; by 2009, densities in OH and other, unplanted, embayments had increased by 110 × and up to 331 ×, respectively. Spatial and temporal patterns paralleled those documented for larval recruitment; highly significant correlations between commercial harvest levels and both baywide larval settlement and juvenile benthic densities were revealed. Official fishery landings were 13 × those of pre-restoration levels by 2010 and have remained relatively stable through 2013. Following commencement of restoration, dockside revenues and economic benefit to the regional economy have increased by ~US$2 million and $20 million, respectively; our calculations suggest that these figures are 40% of actual numbers. Population resurgence is not correlated to temporal changes in predator populations or submerged aquatic vegetation cover. We conclude that rebuilding of Peconic bay scallop populations and fisheries has been driven by dramatic increases in bay scallop larval supply emanating from our intensive restoration efforts. By definition, we cannot say that Peconic bay scallops have attained an alternate stable state, but it is clear that dramatic increases in populations, fishery landings, and economic value are possible in just a few years.

Locomotion of infaunal bivalve mollusks primarily consists of vertical movements related to burrowing; horizontal movements have only been reported for a few species. Here, we characterize hard clam walking: active horizontal locomotion of adults (up to 118 mm shell length, SL) of the commercially important species, Mercenaria mercenaria, at the sediment surface—a behavior only briefly noted in the literature. We opportunistically observed walking over a 10-yr period, at 9 different sites in the Peconic Bays, New York, USA, and tested several hypotheses for the underlying cause of this behavior through quantitative field sampling and reproductive analyses. Hard clam walking was exhibited by males and females at equal frequency, predominantly during June/July and October, when clams were in peak spawning condition. Extensive walking behavior appears to be cued by a minimum population density; we suggest it may be mediated by unidentified pheromone(s), infaunal pressure waves and/or other unidentified factors. There was no directionality exhibited by walking clams, but individuals in an area of extensive walking were highly aggregated and walking clams were significantly more likely to move toward a member of the opposite sex. Thus, we conclude that hard clam walking serves to aggregate mature individuals prior to spawning, thereby facilitating greater fertilization success. In the process of investigating this behavior, however, we apparently oversampled one population and reduced clam densities below the estimated minimum threshold density and, in so doing, suppressed extensive walking for a period of >3 years running. This not only reinforces the importance of detailed field investigations of species biology and ecology, even for those that are considered to be well studied, but also highlights the need for greater awareness of the potential for research activities to affect focal species behavior.

Quantifying predator–prey interactions and gaining insights into predator behavior are crucial for optimizing restoration strategies. However, such knowledge is often lacking for marine invertebrates. We examined potential impacts of predation by channeled Busycotypus canaliculatus and knobbed whelks Busycon carica on natural and planted populations of bay scallops in the Peconic Bays, New York, through laboratory and field investigations. In lab experiments, mean predation rates exhibited by small channeled whelks were low: 0.06 and 0.005 scallops d−1 for adult and juvenile scallops, respectively. Predation rates of small knobbed whelks on juvenile scallops were 22 × higher. Eighty-six percent (86%) of scallops consumed by channeled whelks had undamaged shells, while 73% eaten by knobbed whelks had notched ventral margins. In field plots where scallop densities were manipulated via removals/plantings, whelks consumed ~ 2% of ~ 19,100 planted juveniles, whereas crabs and presumably finfish consumed > 40% overall. Acoustic telemetry revealed that tagged channeled whelks moved shorter distances and spent more time in plots planted with scallops versus those without scallops. Whelks spent more time in low versus high-density plots, but consumed far more scallops in the latter. In trials without scallops, whelk movement rates were 5 × higher, presumably due to increased exploratory behavior. Overall, whelks were most active during crepuscular hours and during periods of increasing wind speeds. Our results, combined with population abundance data, suggest that whelks (especially B. carica) are drawn to planted bay scallop aggregations, but probably contribute to relatively low overall mortality in the context of restoration efforts.