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Marine Fisheries Research - Bycatch Reduction and Gear Modification Research

The Research team has been involved in several types of bycatch reduction and gear modification studies in the past. We have worked with the shrimp, flatfish, and mid-water Rockfish fisheries. This work is not currently-ongoing.

To read about our work in the ocean shrimp (Pandalus jordani) fishery please visit ODFW’s Pink Shrimp pages.

Shrimp bycatch
Offshore longleader gear consists of (1) a minimum of 30 feet of line between the terminal weight (sinker) and the lowest hooks and (2) a non-compressible float above the top hook. Image Credit: ODFW https://myodfw.com/articles/offshore-longleader-gear

Development of a selective flatfish trawl to reduce bycatch of slope Rockfish

We tested the potential of a selective flatfish trawl to reduce bycatch of slope Rockfish in the upper continental slope bottom-trawl fishery (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 flatfish, except arrowtooth flounder Atheresthes stomias, which was reduced 24%. Catches of most Rockfish and roundfish were significantly reduced in the experimental trawl (50–94% depending on species). However, the catches of darkblotched Rockfish Sebastes crameri and redbanded Rockfish S. babcocki were not reduced significantly in the experimental trawl. Nighttime catches were reduced 30–99% for most Rockfish species, the greatest reductions occurring in the experimental trawl. The large nighttime catch reduction for several Rockfish species for both trawls along with no catch reduction in Dover sole Microstomus pacificus, suggests that fishing only at night may be a viable bycatch-reduction strategy for some Rockfish species. The diel and depth-related variation in catch rates we noted for the selective flatfish trawl indicates that catches by this trawl may be especially sensitive to physical and environmental factors such as time of day, depth, or turbidity.

For more information on this work see: 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, DOI: 10.1577/M04-126.1

Testing longleader gear to avoid long-lived demersal species

Several long-lived, late-maturing Rockfish (Sebastes) species found off the U.S. west coast have been seriously depleted by overfishing and are managed under long-term rebuilding plans that greatly restrict fishery impacts (PFMC 2006). Two of these species, Canary Rockfish and Yelloweye Rockfish, are caught in waters off Oregon and Washington as bycatch in recreational fisheries directed at Black Rockfish (S. melanops), Yellowtail Rockfish (S. flavidus), lingcod (Ophiodon elongatus) and Pacific halibut (Hippoglossus stenolepis).

Recreational fishery impacts on the depleted species are constrained primarily via seasonal restrictions on the maximum depth of fishing, area closures and a ban on retention (PFMC 2006), resulting in restricted access to healthy co-occuring stocks. To address this problem, our team has worked on testing gear-based methods that avoid overfished species (e.g. Yellowtail), while allowing anglers to target healthy co-occuring stocks.

Our team tested the hypothesis that angling gear that keeps baits farther above the bottom (long leader gear) would reduce the relative catch rates of Yelloweye, Canary and several demersal Rockfishes, while maintaining acceptable catch rates for the semipelagic (mid-water) Rockfish species most commonly caught off Oregon.

Studies done in 2006-2008 showed that longleader gear was effective in avoiding demersal species. This reduction in catches of demersal species has allowed offshore and recreational fishers to stay open for longer, allowing angers more access to underfished semipelagic stocks.

For more information on the longleader gear study see: Hannah, R. W., T. V. Buell and M. T. O. Blume. 2008. Reducing bycatch in Oregon’s recreational groundfish fishery (pdf): experimental results with angling gear configured to increase bait height above bottom. Oregon Dept. Fish Wildl., Information Rept. Ser., Fish. No. 2008-03. 26 p.

Bycatch and Gear Modification Publications and Information Reports

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