671 



Abstract-In May 2001, the National 

 Marine Fisheries Service (NMFS) 

 opened two areas in the northwest- 

 ern Atlantic Ocean that had been 

 previously closed to the U.S. sea 

 scallop I Placopecten magellanicus) 

 dredge fishery. Upon reopening these 

 areas, termed the "Hudson Canyon 

 Controlled Access Area" and the "Vir- 

 ginia Beach Controlled Access Area." 

 NMFS observers found that marine 

 turtles were being caught inciden- 

 tally in scallop dredges. This study 

 uses the generalized linear model and 

 the generalized additive model fitting 

 techniques to identify environmen- 

 tal factors and gear characteristics 

 that influence bycatch rates, and to 

 predict total bycatch in these two 

 areas during May-December 2001 and 

 2002 by incorporating environmental 

 factors into the models. Significant 

 factors affecting sea turtle bycatch 

 were season, time-of-day, sea sur- 

 face temperature, and depth zone. In 

 estimating total bycatch, rates were 

 stratified according to a combination 

 of all these factors except time-of- 

 day which was not available in fish- 

 ing logbooks. Highest bycatch rates 

 occurred during the summer season, 

 in temperatures greater than 19°C, 

 and in water depths from 49 to 57 m. 

 Total estimated bycatch of sea turtles 

 during May-December in 2001 and 

 2002 in both areas combined was 169 

 animals ( CV= 55.3 ), of which 164 ( 97% ) 

 animals were caught in the Hudson 

 Canyon area. From these findings, it 

 may be possible to predict hot spots 

 for sea turtle bycatch in future years 

 in the controlled access areas. 



Magnitude and distribution of sea turtle bycatch 

 in the sea scallop (Placopecten magellanicus) 

 dredge fishery in two areas of the 

 northwestern Atlantic Ocean, 2001-2002 



Kimberly T. Murray 



Northeast Fisheries Science Center 

 National Marine Fisheries Service 

 166 Water Street 



Woods Hole, Massachusetts 02543 

 E-mail address. Kimberly Murray<S'noaa gov 



Manuscript submitted 1 December 2003 

 to the Scientific Editor's Office. 



Manuscript approved for publication 

 27 May 2004 by the Scientific Editor. 



Fish. Bull. 102:671-681 12004). 



Five species of sea turtles in the 

 northwestern Atlantic Ocean are 

 protected under the U.S. Endangered 

 Species Act of 1973. The loggerhead 

 turtle (Caretta caretta) is listed as a 

 threatened species, and the leather- 

 back (Dermochelys coriacea), hawks- 

 bill (Eretmochelys imbricata), Kemp's 

 ridley iLepidochelys kempii), and 

 certain populations of the green sea 

 turtle (Chelonia mydas) are listed as 

 endangered. Populations of each of 

 these species have declined principally 

 as a result of human activities (NRC, 

 1990). 



The incidental capture, or bycatch, 

 of sea turtles in commercial fisheries 

 is a major source of mortality (NRC, 

 1990; Turtle Expert Working Group, 

 2000). These turtles are captured in- 

 cidentally in pelagic longlines (Lewi- 

 son et al., 2004), trawls (Epperly, 

 2003), gill nets (Julian and Beeson. 

 1998), pound nets, weirs, pots, and 

 traps (NMFS and USFWS, 1991; Al- 

 len, 2000). Such threats occur at vari- 

 ous life stages of a population and at 

 different intensities, and consequent- 

 ly have implications for management 

 policy (Heppell et al., 2003). 



The U.S. National Marine Fisher- 

 ies Service (NMFS) has implemented 

 management measures in both the 

 Atlantic and the Pacific in the form 

 of gear modifications or time and area 

 closures to reduce sea turtle bycatch. 

 For example, since the early 1990s, 

 turtle excluder devices (TEDs) have 

 been required in all inshore and off- 

 shore shrimp trawl nets in southeast- 

 ern U.S. waters (Epperly, 2003) to re- 

 duce sea turtle mortality (Henwood 



and Stuntz, 1987). Bycatches of sea 

 turtles in the U.S. pelagic longline 

 fisheries for swordfish and tuna (Wit- 

 zell, 1999) led to a year-round clo- 

 sure of a 2.6 million nmi 2 area in the 

 northwestern Atlantic Ocean to these 

 fisheries beginning in 2002. 



In recent years, documented inter- 

 actions have occurred between sea 

 turtles and sea scallop dredges, a pre- 

 viously unidentified threat in recovery 

 planning efforts (NMFS, 1991). Dur- 

 ing 2001 and 2002, fisheries observers 

 aboard commercial sea scallop vessels 

 documented the bycatch of sea turtles 

 in two small regions of the Mid-Atlan- 

 tic Bight (MAB). These areas, termed 

 the "Hudson Canyon Controlled Ac- 

 cess Area" (approximately 3150 km 2 i 

 and the "Virginia Beach Controlled 

 Access Area" (approximately 900 km 2 ) 

 were closed to scallop fishing in April 

 1998 but reopened in May 2001 on a 

 conditional basis (Fig. 1). This study 

 uses the generalized linear and gen- 

 eralized additive models to identify 

 environmental factors and gear char- 

 acteristics affecting the bycatch rate 

 of sea turtles in these two areas and 

 to predict total bycatch by sea scallop 

 dredge vessels in these two areas in 

 2001 and 2002. 



Methods 



The fishery 



In 2001 and 2002. 137 and 93 com- 

 mercial vessels, respectively, partici- 

 pated in the Controlled Area Access 

 Program sea scallop fishery. Although 



