The Soft-Shell Clam Mya arenaria: Biology, Fisheries, and Mariculture

Chapter 6: Ecology of the Soft-Shell Clam Mya arenaria

Rochelle D. Seitz and Anson H. Hines

doi: https://doi.org/10.47886/9781934874745.ch6

The ecology of the soft-shell clam Mya arenaria is complex and varied and includes many aspects that are covered in some detail in other chapters of this book. In this chapter, we focus on overarching concepts (e.g., life history, habitat preferences and distribution, temporal patterns, conservation and restoration), outline ecological interactions, and define how these relate to details presented in other chapters. This chapter is intended as a go-to for interested readers to get up to speed on the ecology of M. arenaria by synthesizing available information.

The soft-shell clam is an ecologically as well as commercially important species in many benthic ecosystems (Pfitzenmeyer and Drobeck 1963; Beukema 1974; Virnstein 1977; Holland et al. 1980), with a complex and somewhat uncertain history underlying its current distribution on both sides of the North Atlantic and in the eastern North Pacific (Carlton 2023; Hoffman and Vendrami 2023, both this volume). It comprised ~12% of the profit for domestic commercial clam landings in the USA in 2019 (NMFS 2021), and provided a total landings value of US$25.8 million in 2019 (NMFS 2021). The most lucrative fishery for the clam within the USA occurs in Maine (Figure 1), where the fishery landed 1.6 million pounds of meats (NMFS 2021) and was worth $18.2 million in 2019 (Maine Department of Marine Resources 2020).

In Europe, the soft-shell clam grows to a maximum of 17 cm (6.5 in), but is usually no larger than 10 cm (3.9 in) (Jensen 2010). In addition to directed fisheries (commercial and recreational) and aquaculture in the USA, this species is taken incidentally in Europe, for instance with the comon cockle Cerastoderma edule fishery in the Wadden Sea (Piersma et al. 2001). Ecologically, it is a common bivalve species accounting for a large proportion of the infaunal biomass in many soft-bottom habitats (Dekker and De Bruin 2001; Beukema and Dekker 2020). It has interesting ecological and behavioral features that include deep burial and secondary dispersal (see details below). The species has a wide range of physiological tolerances (Gray 2023, this volume) that allows its distribution to span multiple oceans in coastal areas of many countries. It has complex interactions with other species, both as prey and as competitors (Beal 2023a, this volume).

It has been fished in Chesapeake Bay since the early 1950s (Kennedy 2023b, this volume) and was abundant through the early 1970s (Figure 1) until populations declined precipitously (Glaspie et al. 2018). Similarly, in the northeast USA, landings declined by 66% from 1980 to 2010 (MacKenzie and Tarnowski 2018), which was thought to be associated with increased temperatures that resulted in increased consumption rates by both endemic and invasive predators, but disease has also been implicated (Dungan et al. 2002). The declines in many areas of the species’ distribution have led to recent efforts and discussions regarding conservation and restoration. All of these topics will be covered in the following pages of this chapter.