Farmed and Wild Sea Scallop Energy Allocation to Reproduction and Growth in Penobscot Bay, Maine, USA

Abstract

The Atlantic sea scallop (Placopecten magellanicus, hereafter “scallop”) fishery ranks among the most economically valuable marine fisheries in North America. Recent declines in wild catch and increased demand for sea scallops are supporting an emerging scallop aquaculture industry in Maine; however, the impacts of aquaculture practices on scallop biology remain largely unexplored. We compared various morphometrics of paired farmed and wild scallops at three locations in Penobscot Bay, Maine, to understand the biological differences between the populations. In 2020-2022, we collected farmed scallops from lantern nets at three scallop farms in Penobscot Bay, Maine, and collected wild scallops via SCUBA from adjacent beds. We measured shell heights and shell, adductor, gonad, and total viscera masses individually. Using gonadosomatic indices (GSI), we determined the timing of peak GSI of farmed and wild scallops to be similar over a three-year period. We also found that farmed scallops had up to 28% larger adductor muscle (meat), 35% larger gonad, and 33% larger viscera masses compared to wild scallops, whereas wild scallops had up to 38% larger shell masses than farmed scallop. Larger meat yields from farmed scallops reduce time to market size for scallop growers. Larger gonads suggest an increased potential for reproductive output, a potential benefit to both industries. These results indicate differences in energy allocation of wild and farmed populations of scallops, highlighting the potential for farmed populations to provide larval output to wild populations and the economic benefits of cultivating a larger product in a shorter period.

Keywords: aquaculture impacts, GSI, Placopecten magellanicus, comparative population dynamics, shellfish