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

Published source details Tettelbach S.T., Barnes D., Aldred J., Rivara G., Bonal D., Weinstock A., Fitzsimons-Diaz C., Thiel J., Cammarota M.C., Stark A., Wejnert K., Ames R. & Carroll J. (2011) Utility of high-density plantings in bay scallop, Argopecten irradians irradians, restoration. Aquaculture International, 19, 715-739.
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This study is summarised as evidence for the following.

	Action	Category
	Transplant/release captive-bred or hatchery-reared species - Transplant/release molluscs Action Link

Transplant/release captive-bred or hatchery-reared species - Transplant/release molluscs

A replicated, controlled study in 2005–2006 in one area of muddy sandy seabed with in Northwest Harbor, North Atlantic Ocean, New York, USA (Tettelbach et al. 2011) found that over six months after transplanting hatchery-reared bay scallops Argopecten irradians irradians, abundance (indicating survival) decreased in plots where they were free-planted and in suspended bags, and that scallop growth and formation of shell biofouling varied with transplantation method. In both years, abundance of free-planted scallops decreased over time (2005: from 81–110/m² to 18–37/m²; 2006: from 65–253/m² to <1/m²). Authors report maximum mortalities of 0–1.5%. In both years, abundance of suspended scallops decreased over time (data presented on a logarithm scale), and typically did not vary with stocking densities (7 of 11 sampling dates/year; data not shown). Changes in abundances was not compared between transplanting methods. Transplanted scallops grew in both methods over 6.5 months but grew more in free-planted plots (2005: +20–21 mm; 2006: +30–33 mm) compared to suspended bags (2005: +13–14 mm; 2006: +21–22 mm). Growth rate of scallops in bags did not vary with stocking densities (data not shown). Over the 4.5 months after transplantation, free-planted scallops developed less biofouling than suspended scallops (2005: 0.62 vs 1.98 g/scallop; 2006: 0.91 vs 2.5 g/scallops; data extracted from the text). Two methods of transplantation were tested: free-planting and suspended bags. Free-planted scallops were distributed directly on the seabed in four 25 x 25 m plots at 1.3–3 m depth. Suspended scallops were placed in 36 floating units (2 m below the surface), each consisting of three bags of 50, 100 and 200 scallops/bag. Scallops were deployed in March/April of 2005 and 2006. From May–September/October scallop abundances were monitored monthly and growth was quantified biweekly. Monthly survival was estimated by counting live free-planted scallops in 12–16 quadrats (1 m²)/plot and counting live scallops/bag. Growth (shell height increase) was assessed for 20 scallops/methods/sampling date. In August 2005 and 2006, biofouling organisms growing on 156–159 scallop shells were scrapped and weighed.

(Summarised by: Anaëlle Lemasson & Laura Pettit)