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New Bedford, MA, United States

Skomal G.B.,213 Purchase St. | Hoyos-Padilla E.M.,Pelagios Kakunja A.C. Sinaloa 1540 | Kukulya A.,Woods Hole Oceanographic Institution | Stokey R.,Woods Hole Oceanographic Institution
Journal of Fish Biology | Year: 2015

In this study, an autonomous underwater vehicle (AUV) was used to test this technology as a viable tool for directly observing the behaviour of marine animals and to investigate the behaviour, habitat use and feeding ecology of white sharks Carcharodon carcharias near Guadalupe Island off the coast of Mexico. During the period 31 October to 7 November 2013, six AUV missions were conducted to track one male and three female C. carcharias, ranging in estimated total length (LT) from 3·9 to 5·7 m, off the north-east coast of Guadalupe Island. In doing so, the AUV generated over 13 h of behavioural data for C. carcharias at depths down to 90 m. The sharks remained in the area for the duration of each mission and moved through broad depth and temperature ranges from the surface to 163·8 m depth (mean ± s.d. = 112·5 ± 40·3 m) and 7·9-27·1° C (mean ± s.d. = 12·7 ± 2·9° C), respectively. Video footage and AUV sensor data revealed that two of the C. carcharias being tracked and eight other C. carcharias in the area approached (n = 17), bumped (n = 4) and bit (n = 9) the AUV during these tracks. This study demonstrated that an AUV can be used to effectively track and observe the behaviour of a large pelagic animal, C. carcharias. In doing so, the first observations of subsurface predatory behaviour were generated for this species. At its current state of development, this technology clearly offers a new and innovative tool for tracking the fine-scale behaviour of marine animals. © 2015 The Fisheries Society of the British Isles. Source

Marshall H.,University of Massachusetts Dartmouth | Marshall H.,Mote Marine Laboratory | Skomal G.,213 Purchase St. | Ross P.G.,Virginia Institute of Marine Science | Bernal D.,University of Massachusetts Dartmouth
Fisheries Research | Year: 2015

Since the mid 1990's, stock assessments of shark populations in the northwest Atlantic by the National Marine Fisheries Service (NMFS) have indicated that sandbar (. Carcharhinus plumbeus) and dusky (. C. obscurus) populations are overfished. In response to these assessments, the dusky shark bottom longline fishery was closed in 2000, followed by the sandbar fishery in 2005. A common management strategy is to mandate the release of prohibited species if caught as bycatch. However, a major assumption is that most released sharks survive, which may not be the case. Longline operations were conducted during 2011 and 2012 to capture and tag sandbar and dusky sharks, in order to assess (1) at-vessel mortality, (2) post-release mortality, and (3) investigate the effects of soak-time on each of these variables for each species. Our findings show that dusky sharks experience high at-vessel and post-release mortality, with mortality occurring more frequently after 3-5. h on the line. While time-on-the-line (TOL) increased dusky shark at-vessel (16% when less than 3 h TOL; 27.5% when more than 3 h TOL) and post-release mortality (11% when less than 3 h TOL; 42% when more than 3 h TOL), sandbar shark at-vessel mortality was low (0% when less than 3 h TOL). Nonetheless, the apparently hardier sandbar sharks did exhibit 29% post-release mortality after 3 h TOL. The total mortality (at-vessel. +. post-release, including moribund individuals) for dusky sharks was 97% after being captured on a demersal longline when TOL surpassed 3. h. These data clearly elucidate an interspecific difference in vulnerability to longline gear between these species. © 2015 Elsevier B.V. Source

Chosid D.M.,213 Purchase St. | Pol M.,213 Purchase St. | Szymanski M.,213 Purchase St. | Mirarchi F.,Fishing Vessel Barbara L. Peters | Mirarchi A.,Fishing Vessel Barbara L. Peters
Fisheries Research | Year: 2012

A spiny dogfish Squalus acanthias excluder grate (grid) within the extension of a silver hake (whiting) Merluccius bilinearis trawl net was designed and tested in Massachusetts Bay, USA between October 2008 and August 2009 using a live-fed underwater video camera. Grates with 50. mm spacing were investigated for effects from color (white or black), angle, and direction (leading to a top or bottom escape vent). Spiny dogfish numbers were greatly reduced for all gear configurations based on video observations and data collected from the codend, while target species were caught in commercial quantities. Four tows (of various gear configurations) resulted in spiny dogfish blockages in front of the grate. The reduction of spiny dogfish led to increases in the quality of marketable catches, likely reductions in non-target species mortality, and decreases in the codend catch handling times. © 2011. Source

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