Cruise Results – Part B

Results of an Exempted Fishery Conducted with the Groundfish Forum and Trident Seafoods

In early April 2001, part B of the 2000 EFP was conducted in the southeast Bering Sea aboard the F/V Northwest Explorer.  This part of the EFP was a cooperative research effort between The Groundfish Forum, Trident Seafoods and scientists from the RACE Division of the NMFS’s Alaska Fisheries Science Center.

In contrast to previous studies, a recapture net was not used and tows with matched nets were alternated with the excluder (experimental tows) and without the excluder (control tows), which allowed testing under actual commercial fishing conditions.  Other differences included:  codend meshes (176 mm stretch square mesh) used by the fishery, larger meshes in the intermediate section containing the ring excluder (195 mm diamond), size composition of halibut (Figure 1), and due to the construction of the trawls, the excluders had to be moved aft so that the skate excluder was in an untapered section and the slot section connected directly to the codend.

While the original excluder included skate, ring and slot sections, the ring section was removed after 3 excluder tows because:

  • Very few halibut < 60 cm were encountered, most being in the 30-40 cm range;
  • Apparent significant loss of all sizes of cod was occurring, and the large meshes in the ring  section were considered a likely site of such escapes; and
  • Minor damage was occurring to the fiberglass rods in the ring section.

Seven excluder tows were completed using the skate and slot excluders (Figure 2), as well as seven control tows.

Figure 2

Comparisons of the catch per hour from those tows showed that the average cod catch with the excluders was 11% lower than the control tows, while decreases of halibut, pollock and rock sole were 86%, 97% and 99%, respectively (Figure 3).  Only the cod difference was not statistically significant.  Analysis of the length data indicates that cod escapes were mostly fish smaller than 55 cm.  The vessel captain felt that the cod loss may have been significantly higher, based on echo sounder information during the tow and catch reports from nearby vessels.  There was agreement that excluder performance would likely be improved by moving the device forward, further away from the codend.

Presence of the excluders did not significantly increase handling time of the net, and the excluders were not damaged by normal fishing operations.