Groundfish Assessment Program
Trawl Gear Research
|The standard sampling gear used in the eastern Bering Sea trawl survey is
the 83-112 eastern otter trawl, which has a 25.3-m headrope and 34.1 m footrope. Mesh sizes are 10.2 cm in
the wings and 8.9 cm in the intermediate and codend. The codend has a liner of 3.2 cm. (Click on image to
Gear research has included examinations of physical and environmental effects on both trawl performance and
fish availability to research trawls. Maintaining a time series as a representative measure of relative abundance
for groundfish requires consistency in terms of both survey trawl performance and
fish availability to the survey trawl gear.
|Slope survey catch (Click on image to enlarge).
Trawl performance studies have included examinations of door and net spread, net height, and bottom contact and
their influence on catch efficiency.
Research on fish availability has included an examination of the effects of
light on the vertical distribution of walleye pollock, and an examination of the vertical distribution of Pacific
cod in relation to the survey trawl gear.
|Trawl Gear Research Publications
- Kotwicki, S. and Weinberg, K.L. 2005. Estimating capture probability of a survey bottom trawl for Bering Sea skates (Bathyraja spp.) and other fish. Alaska Fish. Res. Bull. 11:135-145. Online
- Kotwicki, S., De Robertis, A., Von Szalay, and P.G., Towler, R. 2009. The effect of light intensity on the availability of walleye pollock (Theragra chalcogramma) to bottom trawl and echo-integration trawl surveys in the Eastern Bering Sea. Can. J. Fish. Aquat. Sci. 66:983-994.
- Kotwicki, S., Weinberg, K.L. and Somerton, D.A. 2006. The effect of autotrawl systems on the performance of a survey trawl. Fish. Bull., 104:35-45. Online
- Lauth, R.R., Ianelli, J., and Wakefield, W.W. 2004. Estimating the size selectivity and catching efficiency of a survey bottom trawl for thornyheads, Sebastolobus spp. Using a towed camera sled. Fish. Res., 70:27-37.
- Lauth, R.R., S.E. Syrjala, and S. W. McEntire. 1998. Effects of gear modifications on the performance and catching efficiency of the west coast upper continental slope groundfish trawl. Mar. Fish. Rev. 60(1):1-26. Online
- Lauth, R.R., Wakefield, W.W. and Smith, K. 2004. Estimating the density of thornyheads, Sebastolobus spp., using a towed video camera sled. Fish. Res. 70:39-48.
- Munro, P.T. and Somerton, D.A. 2002. Estimating net efficiency of a survey trawl for flatfishes. Fish. Res. 55:267-279.
- Nichol, D.G. Honkalehto, T., and Thompson, G.G. 2007. Proximity of Pacific cod to the sea floor: Using archival tags to estimate fish availability to research bottom trawls. Fish. Res. 86:129-135.
- Rose, C.S. and Walters, G.E. Trawl width variation during bottom-trawl surveys: Causes and consequences. Publ. R.I. Sea Grant Coll. Program, pp.34-41.
- Somerton, D.A. 2004. Do Pacific cod (Gadus macrocephalus) and walleye pollock (Theragra chalcogramma) lack a herding response to the doors, bridles, and mud clouds of survey trawls? ICES J. Mar. Sci. 61, 1186-1189.
- Somerton, D.A. and Weinberg, K.L. 2001. The affect of speed through the water on footrope contact of a survey trawl. Fish Res. 53:17-24.
- Somerton, D.A., Munro, P.T., and Weinberg, K.A. 2007. Whole-gear efficiency of a benthic survey trawl for flatfish. Fish. Bull. 105:278-291.
- Von Szalay, P.G. and Somerton, D.A. 2005. The effect of net spread on the capture efficiency of a demersal survey trawl used in the eastern Bering Sea. Fish. Res. 74, 86-95.
- Von Szalay, P.G., Somerton, D.A., and Kotwicki, S. 2007. Correlating trawl and acoustic data in the eastern Bering Sea: A first step toward improving biomass estimates of walleye pollock (Theragra chalcogramma) and Pacific cod (Gadus macrocephalus) Fish. Res. 86:77-83.
- Weinberg, K.L. and Somerton, D.A. 2006. Variation in trawl geometry due to unequal warp length. Fish. Bull., U.S., 104:21-34.
- Weinberg, K.L. 2003. Change in the performance of a Bering Sea survey trawl due to varied trawl speed. Alaska Fish Res. Bull. 10: 42-49.
- Weinberg, K.L., and Munro, P.T. 1999. The effect of artificial light on escapement beneath a survey trawl. ICES J. Mar. Sci. 56:266-274.
- Weinberg, K.L., and S. Kotwicki. 2008. Factors influencing net width and sea floor contact of a survey bottom trawl. Fish. Res. 93:265-279.
- Weinberg, K.L., Otto, R.S. and Somerton, D.A. 2004. Capture probability of a survey trawl for red king crab (Paralithodes camtschaticus). Fish. Bull. 102:740-749.
- Weinberg, K.L., Somerton, D.A., and Munro, P.T. 2002. The effect of trawl speed on the footrope capture efficiency of a survey trawl. Fish. Res. 58, 303-313.
- Zimmermann, M., Wilkins, M.E., Weinberg, K.L., Lauth, R.R., and Shaw, F.R. 2003. Influence of improved performance monitoring on the consistency of a bottom trawl survey. ICES J. Mar. Sci. 60:818-826.
See the publications and
poster databases for