APPENDIX II Using Sea Turtle Carcasses to Assess the Conservation Potential of a Turtle

—Fisheries observers have documented interactions between sea turtles in the family Cheloniidae and the Atlantic sea scallop Placopecten magellanicus fishery. Sea turtle injuries resulting from interactions with scallop dredges are being mitigated through shifts in fishing effort and modifications to fishing gear. The standard New Bedford dredge can trap objects and crush them as they pass between the dredge frame and sea floor, so a modified turtle excluder dredge has been designed to reduce the likelihood of a turtle’s passing under the frame when the dredge fishes on the seafloor. The key elements of the modified design are a forward cutting bar (which results in a sloping rather than a vertical face), a reduced number of bale support bars (just the center and outer bales), extension of the outer bale bars before tapering to the gooseneck (hauling point), and a reduction in the sources of entrapment between the depressor plate and the cutting bar via reduced spacing of struts. We evaluated the ability of the modified dredge to cause live sea turtles to pass over it by using loggerhead sea turtle Caretta caretta carcasses as a proxy. The carcasses were placed on the seafloor in the path of a towed dredge equipped with video cameras. Nine interactions between carcasses and the modified dredge were documented on video recordings. In each of the interactions, the carcass hit the dredge and passed over the dredge frame with little or no physical damage to the recovered carcasses. These carcass studies suggest that the turtle excluder dredge reduces sea turtle injuries associated with interactions between sea turtles and scallop dredges fishing on the seafloor. The bycatch of sea turtles (family Cheloniidae) in commercial fisheries is an important conservation issue (Moore et al. 2009) and continues to garner the attention of the environmental community and others as many consider sea turtles a charismatic species. The commercial fishery for the Atlantic sea scallop Placopecten magellanicus is an important U.S. fishery, harvesting 26,545 metric tons of meats in 2007 with a value of US$385 million (NMFS 2008). Ninety-five percent of the commercial sea scallop landings are harvested with a standard New Bedford dredge (NEFMC 2010) that consists of a steel bale, rectangular frame, sweep chain, and ring bag (Figure 1). Observers with NOAA–Fisheries have documented interactions between sea turtles and dredge gear used to fish Atlantic sea scallops, with estimates of an annual loggerhead sea turtle Caretta caretta bycatch from 0 to 749 sea turtles per year (Murray 2004a, 2004b, 2005, 2007). Sea turtle injuries resulting from interactions with scallop dredging are being mitigated through seasonal shifts in the fishing effort for Atlantic sea scallops and modifications to the fishing gear. An unknown number of unobserved interactions between sea turtles and dredges occur while the dredge is fishing for scallops on the sea floor or at the end of the haul when the dredge is pulled up through the water column. During deployment, dredges drop straight to the sea floor with the bag closed; thus, interactions with turtles are highly unlikely. It is not known what part of the haul catches sea turtles or when injuries occur, although most of the observed interactions that have resulted in turtle injuries occurred when the turtle was caught in the ring bag (DuPaul et al. 2004; Smolowitz et al. 2005; Haas et al. 2008). * Corresponding author: [email protected] Received March 22, 2010; accepted June 3, 2010 Published online August 25, 2010 993 North American Journal of Fisheries Management 30:993–1000, 2010 Copyright by the American Fisheries Society 2010 DOI: 10.1577/M10-061.1 [Article]