Utility of high-density plantings in bay scallop, Argopecten irradians irradians, restoration

Abstract

Two different methods of establishing high-density spawner sanctuaries for bay scallop (Argopecten irradians irradians) restoration were evaluated over 2 years at a site in Northwest Harbor, East Hampton, New York, USA. Hatchery-reared scallops, which had been overwintered at nearby sites, were free-planted directly to the bottom in late March/ early April at an initial target density of 94-128 scallops/m 2 . In addition, scallops were stocked in off-bottom culture units consisting of three vertically stacked 15-mm mesh ADPI Ò bags at densities of 50, 100, or 200 scallops/bag (=117, 234, or 468 scallops/m 2 ), respectively. Survival of scallops differed significantly by year, planting method, and scallop source. Survival of free-planted scallops was generally lower than caged scallops. Better survival of free-planted scallops in 2005 versus 2006 likely reflected the presence of luxuriant eelgrass beds in 2005, which were absent in 2006. Survival of scallops in ADPI bags was not appreciably related to stocking density. Shell growth was highest for freeplanted scallops; in cages, growth was somewhat better at 50 versus 200 scallops/bag. Wet weights of epibionts were significantly higher in caged versus free-planted scallops. Reproductive condition of scallops stocked at 50/bag was usually higher than at 200/bag. Both free-planting and off-bottom systems yielded high densities of adult bay scallops at the time of spawning, which ensures a higher probability of successful fertilization of spawned eggs and thus a greater potential for success of restoration efforts.

Natural and Anthropogenic Forces Shape the Population Genetics and Recent Evolutionary History of Eastern United States Bay Scallops (Argopecten irradians)

“…However, within the past few decades, loss of critical seagrass habitat (Thayer & Stuart 1974, Pohle et al 1991 has also contributed to declines in numbers of bay scallops in all areas where they have been traditionally harvested (Tettelbach et al 1990, Peterson & Summerson 1992, Bologna et al 2001, and recovery of populations to harvestable densities now can take years (Peterson & Summerson 1992) or decades (Bologna et al 2001, Tettelbach 2009) because local recruitment is limited when bay scallop density is low (Peterson & Summerson 1992, Arnold et al 1998, and reliable recruitment from elsewhere is unlikely (this study). Therefore, fisheries managers have turned to various types of stock enhancement to bolster or regenerate Atlantic bay scallop aggregations (Peterson & Summerson 1992, Arnold et al 1998, Goldberg et al 2000, Tettelbach et al 2010; see also Blake and Graves (1995) and Marko and Barr (2007)). …”

“…Intensive, multiyear efforts seem to be the most successful (Tettelbach et al 2010). The high value of bay scallops as a seafood item ensures that efforts to rebuild stocks to harvest-able levels will continue, principally through hatchery-based stock enhancement.…”

“…Its high fishery value has resulted in considerable attention toward increasing the numbers of individuals and geographic expanses of existing aggregations and regenerating lost aggregations, principally through some form of hatchery-based stock enhancement (seeding de-pleted wild populations or suitable unpopulated areas with aquacultured young individuals or placing aquacultured mature individuals in cages in the ocean and allowing them to spawn) (Tettelbach & Wenczel 1993, Peterson et al 1996, Tettelbach 2009, Tettelbach et al 2010. The potential genetic impacts of both the depletions and the restorations are numerous, varied, and potentially threatening to the species' ability to survive over evolutionary time (Bert et al 2007).…”

The Impact of the Second Seasonal Spawn on the Nantucket Population of the Northern Bay Scallop

“…Values in the literature for the bay scallop range from 2 £ 10 6 (Belding 1910) to 23.7 £ 10 6 eggs (Bricelj et al 1987) per spawning. We chose the more conservative rate of 2 £ 10 6 (Belding 1910) for year-1 classics because it is still considered a valid indicator of egg production in the wild (Tettelbach et al 2011). There was no difference in fecundity during the first and second spawning periods of year-1 classics during 2010, the only year tested (ANOVA: P D 0.64, F D 0.2167, n D 40) (Hall 2014), so we used the same value for both.…”

“…Values for F 2 following the lognormal distribution ranged from a minimum of 0.777 to a maximum of 2,150 eggs/individual per spawn. These values were determined by multiplying together the lowest figures for fecundity, fertilization rate, larval survival, and settlement rate obtained from the literature (Belding 1910;Brousseau 1978b;Soria et al 2010;Tettelbach et al 2011) and then doing the same with the highest figures (Thorson 1966;Bricelj et al 1987;LePennec et al 1998;Tettelbach et al 2011).…”