This article was downloaded by: [Oregon State University] On: 07 September 2011, At: 16:29 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK North American Journal of Fisheries Management Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/ujfm20 Evaluation of a Selective Flatfish Trawl and Diel Variation in Rockfish Catchability as Bycatch Reduction Tools in the Deepwater Complex Fishery off the U.S. West Coast Robert W. Hannah a , Steven J. Parker a & Troy V. Buell a a Oregon Department of Fish and Wildlife, Marine Resources Program, 2040 Southeast Marine Science Drive, Newport, Oregon, 97365, USA Available online: 08 Jan 2011 To cite this article: Robert W. Hannah, Steven J. Parker & Troy V. Buell (2005): Evaluation of a Selective Flatfish Trawl and Diel Variation in Rockfish Catchability as Bycatch Reduction Tools in the Deepwater Complex Fishery off the U.S. West Coast, North American Journal of Fisheries Management, 25:2, 581-593 To link to this article: http://dx.doi.org/10.1577/M04-126.1 PLEASE SCROLL DOWN FOR ARTICLE Full terms and conditions of use: http://www.tandfonline.com/page/terms-and-conditions This article may be used for research, teaching and private study purposes. Any substantial or systematic reproduction, re-distribution, re-selling, loan, sub-licensing, systematic supply or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material. North American Journal of Fisheries Management 25:581±593, 2005 q Copyright by the American Fisheries Society 2005 [Article] DOI: 10.1577/M04-126.1 Evaluation of a Selective Flat®sh Trawl and Diel Variation in Rock®sh Catchability as Bycatch Reduction Tools in the Deepwater Complex Fishery off the U.S. West Coast ROBERT W. H ANNAH,* STEVEN J. PARKER, AND TROY V. B UELL Oregon Department of Fish and Wildlife, Marine Resources Program, 2040 Southeast Marine Science Drive, Newport, Oregon 97365, USA Abstract.ÐWe tested the potential of a selective ¯at®sh trawl to reduce bycatch of slope rock®sh in the upper continental slope bottom-trawl ®shery (250±500 m) on the U.S. West Coast. The trawl we tested differed from typical slope trawls in that it was a low-rise, two-seam trawl with a severely cut back headrope. We used an alternate haul, randomized block design to compare catches of the experimental trawl with those of a typical four-seam, high-rise trawl and to examine diel changes in catch rates for both trawls. The experimental trawl produced catches similar to the control trawl for all commercially valuable ¯at®sh, except arrowtooth ¯ounder Atheresthes stomias, which was reduced 24%. Catches of most rock®sh and round®sh were signi®cantly reduced in the experimental trawl (50±94% depending on species). However, the catches of darkblotched rock®sh Sebastes crameri and redbanded rock®sh S. babcocki were not reduced signi®cantly in the experimental trawl. Nighttime catches were reduced 30±99% for most rock®sh species, the greatest reductions occurring in the experimental trawl. The large nighttime catch reduction for several rock®sh species for both trawls along with no catch reduction in Dover sole Microstomus paci®cus, suggests that ®shing only at night may be a viable bycatch-reduction strategy for some rock®sh species. The diel and depth-related variation in catch rates we noted for the selective ¯at®sh trawl indicates that catches by this trawl may be especially sensitive to physical and environmental factors such as time of day, depth, or turbidity. The U.S. West Coast bottom-trawl ®shery on (PFMC 2002). Given the low productivity of rock- the upper continental slope targets sable®sh An- ®shes (Clark 2002; Ralston 2002), a better solution oplopoma ®mbria, Dover sole Microstomus paci- for the deepwater-complex ®shery might be to de- ®cus, and shortspine thornyhead Sebastolobus velop gears that do not ef®ciently capture slope alascanus and, at greater depths, longspine thor- rock®sh species. nyhead Sebastolobus altivelis. This group of spe- Comparative ®shing experiments on the U.S. cies is also known as the ``deepwater complex.'' West Coast continental shelf have shown that the In recent years, this ®shery has been allowed to bycatch of some over®shed rock®sh species, no- operate only in areas deeper than about 275±366 tably canary rock®sh Sebastes pinniger, can be re- m because of concerns about bycatch of two over- duced with the use of a selective ¯at®sh trawl ®shed rock®sh species, darkblotched rock®sh Se- (King et al. 2004). The trawl tested by King et al. bastes crameri and Paci®c ocean perch Sebastes (2004) incorporated very low total rise and a se- alutus (PFMC 2002; the ®shing area boundaries Downloaded by [Oregon State University] at 16:29 07 September 2011 verely cut back headrope, similar to a trawl de- vary seasonally). Given the depth distributions of veloped in the Faroe Islands by Thomsen (1993). these two rock®shes, the depth restriction should The bycatch for some larger species of rock®sh be very effective at limiting bycatch. Longer term and round®sh in this trawl was 70±90% less than however, the concentration of deepwater-complex in traditional trawls (i.e., less or greater percent- ®shing effort in deeper areas could lead to serious ages in this paper 5 the tested value minus the bycatch problems with other species. For example, concentrating the ®shery deeper than 366 m will comparison base value/the comparison base val- probably increase impacts on aurora rock®sh Se- ue). The experimental results of King et al. (2004) bastes aurora and rougheye rock®sh Sebastes aleu- were also veri®ed under actual commercial ®shing tianus, species for which stock status is unknown conditions through a large-scale exempted ®shing permit ®shery, demonstrating similar levels of by- catch reduction (Parker et al. 2004). As a result * Corresponding author: [email protected] beginning in 2005, selective ¯at®sh trawls are re- Received July 27, 2004; accepted September 21, 2004 quired for all trawling shallower than 183 m off Published online May 13, 2005 Oregon and Washington. The potential for selec- 581 582 HANNAH ET AL. tive trawls to reduce bycatch of bocaccio Sebastes sual stimuli that could cause ®sh to dive into the paucispinis is also being tested in waters off Cal- trawl. Our trawl differed from that tested by King ifornia. et al. (2004) only in that it employed a rock-hopper West Coast tests of selective ¯at®sh trawls have style footrope that better matched the footropes been primarily conducted in waters shallower than used in the deepwater ®shery. The con®guration 200 m. Several important slope rock®sh species consisted of a 31.2-m chain footrope covered with are primarily found deeper than 200 m. Therefore, rubber disks 17.8 cm in diameter, which were in- the available data do not provide information on terspaced with single rubber disks (35.6 cm in di- species such as Paci®c ocean perch, yellowmouth ameter) at 58.4-cm intervals along the length of rock®sh Sebastes reedi, aurora, or rougheye and the footrope. Another chain, called the rockhopper darkblotched rock®shes. The primary objective of chain, ran through the outer edge of the large disks this research was to test a selective ¯at®sh trawl and was covered by rubber disks 12.7-cm in di- at the depths ®shed by the deepwater-complex ®sh- ameter. A chain ®shing line was attached to the ery to determine if it could be effective at reducing rock-hopper chain with shackles spaced at 51 cm. slope rock®sh bycatch. The netting of the trawl was attached to a rope A secondary objective of this project was to bolsh line, which was lashed to the chain ®shing estimate the reduction in catch of shortspine thor- line. The sweeps (mud gear) between the trawl nyheads using the experimental trawl in the slope doors and the trawl bridles consisted of 110 m of ®shery. The shortspine thornyhead is not a highly 1.5-cm cable covered with 7.5-cm rubber disks. productive species, based on life history charac- The trawl doors were 1.5 3 2.1 m AMCO V-type teristics and recent population trends (PFMC 2002; steel doors and were used for both trawls. Ralston 2002). King et al. (2004) found the catch The control trawl chosen for this experiment of large ($26 cm) shortspine thornyheads on the was a typical four-seam Aberdeen trawl designed continental shelf to be 34% less with a selective for a much higher overall rise than the experi- ¯at®sh trawl than the traditional trawl. However, mental trawl (Figure 2). This trawl had a footrope as for slope rock®sh, the study did not sample at length of 32 m and a headrope length of 27 m, the optimal depths for shortspine thornyheads. creating the typical square or overhanging hood. Any noted reduction in shortspine thornyhead The control trawl had no netting in the forward catch in the deepwater-complex ®shery should be part of the lower wing, creating an open space evaluated because it could provide a useful man- above the footrope ends, also known as a ¯ying agement tool if the shortspine thornyhead stock wing.