Effects of Bait Type and Conspecific Attraction in Diamondback Terrapin (Malaclemys terrapin) Bycatch

Publication date: January 2020 INTRODUCTION Malaclemys terrapin (Diamondback terrapin; hereafter referred to as terrapins) are a uniquely estuarine turtle on the Atlantic and Gulf coasts of the United States threatened by activities associated with coastal development, such as commercial and recreational crabbing, habitat loss, and vehicle mortality (Ernst and Lovich, 2009). Diamondback terrapins are an important component in estuarine food webs because of their contribution to biomass production and partial maintenance of marsh grass populations through consumption of grazing periwinkle snails (Silliman and Bertness, 2002). The current range-wide declines in terrapin populations could contribute to collapses in coastal salt marsh ecosystems through the loss of biodiversity and marsh stability (Gibbons et al., 2001; Dorcas et al., 2007; CITES, 2013; IUCN, 2019). Bycatch and subsequent drowning in both commercial and recreational crab pots appears to be a major factor in population decline (Bishop, 1983; Roosenburg et al., 1997; Wood, 1997; Roosenburg and Green, 2000; Tucker et al., 2001; Grosse et al., 2009; 2011; Rook et al., 2010; Bury, 2011; Hart and Crowder, 2011; Harden and Williard, 2012). Due to pronounced sexual dimorphism which results in significantly larger females, the mortality rates of males and juveniles in pots are high, creating biased populations of older female terrapins (Lovich and Gibbons, 1990; Dorcas et al., 2007). Terrapin population stability is highly dependent on the survival of breeding adults and juvenile recruitment, or entry into the breeding population. Therefore, mortality resulting from crab pots can devastate populations by altering age and sex ratios (Dorcas et al., 2007; Grosse et al., 2009; Crawford et al., 2014a). Reduced recruitment of males and young females into the breeding population will likely have detrimental effects on the stability of Diamondback terrapin populations, as has been documented in closely-related species (Congdon et al., 1993; Heppell, 1998; Gibbons et al., 2001; Dorcas et al., 2007; Crawford et al., 2014b).