Aspiring to an altered stable state: rebuilding of bay scallop populations and fisheries following intensive restoration

Abstract

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.

Diurnal Fluctuations in Acidification and Hypoxia Reduce Growth and Survival of Larval and Juvenile Bay Scallops (Argopecten irradians) and Hard Clams (Mercenaria mercenaria)

“…Scallops are epifaunal, live on the sediment surface, and are thus exposed to overlying water column chemistry, whereas hard clams are infaunal, burrowed in coastal sediments that are naturally acidified and are often exposed to porewaters that are undersaturated in calcium carbonate (Green and Aller, 1998;Green et al, 2009). The differential vulnerability of these populations to acidification has important implications for regional restoration efforts (e.g., Tettelbach et al, 2015). Future efforts in regions where both bivalve species exist and diurnal patterns of pH and DO are extreme may seek to focus on the more resilient, M. mercenaria, over A. irradians, which is more susceptible to the imminent intensification of acidification predicted to occur this century (Doney et al, 2009;O'Leary et al submitted).…”

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

“…The process of walking at the sediment surface potentially exposes bivalves to higher predation [15,17]. However, Mercenaria of the sizes we observed are greater than those which might be successfully attacked by the majority of non-human predators in the Peconic Bays [36,59]. While channeled ( Busycotypus canaliculatus ) and knobbed whelks ( Busycon carica ) are both common at the sites where walking was observed [36], feeding rates of these species on Mercenaria are low [60].…”

“…However, Mercenaria of the sizes we observed are greater than those which might be successfully attacked by the majority of non-human predators in the Peconic Bays [36,59]. While channeled ( Busycotypus canaliculatus ) and knobbed whelks ( Busycon carica ) are both common at the sites where walking was observed [36], feeding rates of these species on Mercenaria are low [60]. Aggregation may increase the probability of parasite transmission or intraspecific competition [27,61], but observed parasite loads in sampled clams were very low.…”

The harmful algae, Cochlodinium polykrikoides and Aureococcus anophagefferens, elicit stronger transcriptomic and mortality response in larval bivalves (Argopecten irradians) than climate change stressors

“…Bay scallop populations along the eastern US have encountered numerous challenges in recent decades with overharvest (Barber & Davis, 1997), habitat loss (Orth et al, 2006;Serveiss et al, 2004), and recurring harmful algal blooms (Cosper et al, 1987;Summerson & Peterson, 1990) contributing to a 97% decline in landings since the 1980s (NOAA Fisheries Landings 1980-2016; www.noaa.gov) and population-level declines in areas where bay scallop fisheries were once significant (Tettelbach et al, 2013). While some bay scallop restoration efforts have exhibited success (Tettelbach et al, 2015), findings presented here demonstrate that the presence of multiple stressors may complicate future restoration. As carbon emissions continue to warm and acidify coastal ecosystems, the associated adverse effects on bay scallop populations may intensify.…”

“…Hence, the decline and/or collapse of these fisheries have adverse socioeconomic and ecological implications (Beck et al, 2011;Jackson, 2001;Lotze, 2006). Bay scallops (Argopecten irradians) are a prime example of a collapsing bivalve fishery (Blake & Shumway, 2006;Tettelbach et al, 2015;Tettelbach & Wenczel, 1993). Native to shallow, estuarine habitats along the eastern United States (Blake & Shumway, 2006;Clark, 1965), bay scallop populations have been in decline since the early 1980s, during which US landings have been reduced by ~97% (NOAA Fisheries Landings 1980-2016www.noaa.gov).…”