Whole-gear efficiency of a benthic survey trawl for flatfish

Whole-gear efficiency (the proportion of fish passing between the otter doors of a bottom trawl that are subsequently captured) was estimated from data collected during experiments to measure the herding efficiency of bridles and doors, the capture efficiency of the net, and the length of the bridles sufficiently close to the seafloor to elicit a herding response. The experiments were focused on four species of flatfish: arrowtooth flounder (Atheresthes stomias), flathead sole (Hippoglossoides elassodon), rex sole (Glyptocephalus zachirus), and Dover sole (Microstomus pacificus). Whole-gear efficiency varied with fish length and reached maximum values between 40% and 50% for arrowtooth flounder, flathead sole, and rex sole. For Dover sole, however, whole-gear efficiency declined from a maximum of 33% over the length range sampled. Such efficiency estimates can be used to determine catchability, which, in turn, can be used to improve the accuracy of stock assessment models when the time series of a survey is short.

[1]  O. Godø,et al.  The effect of different sweep lengths on the length composition of bottom-sampling trawl catches , 1989 .

[2]  O. Godø,et al.  Escape of fish under the fishing line of a Norwegian sampling trawl and its influence on survey results , 1989 .

[3]  N. Andrew,et al.  The effects of trawl configuration on the size and composition of catches using benthic prawn trawls off the coast of New South Wales, Australia , 1991 .

[4]  S. Walsh Size-Dependent Selection at the Footgear of a Groundfish Survey Trawl , 1992 .

[5]  W. Dickson Estimation of the capture efficiency of trawl gear. II: Testing a theoretical model , 1993 .

[6]  W. Dickson Estimation of the capture efficiency of trawl gear. I: Development of a theoretical model , 1993 .

[7]  M. Nelson,et al.  Food Habits of the Commercially Important Groundfishes in the Gulf of Alaska in 1990, 1993, and 1996 , 1993 .

[8]  Yongshun Xiao,et al.  Herding in groundfish and effective pathwidth of trawls , 1995 .

[9]  C. Bublitz Quantitative evaluation of flatfish behavior during capture by trawl gear , 1996 .

[10]  Stephen J. Smith,et al.  Incorporating experimentally derived estimates of survey trawl efficiency into the stock assessment process: a discussion , 1999 .

[11]  P. He,et al.  Swimming endurance of American plaice (Hippoglossoides platessoides) and its role in fish capture , 1999 .

[12]  D. Somerton,et al.  The affect of speed through the water on footrope contact of a survey trawl , 2001 .

[13]  D. Somerton,et al.  Maximum likelihood and non-parametric methods for estimating trawl footrope selectivity , 2001 .

[14]  D. Somerton,et al.  Estimating net efficiency of a survey trawl for flatfishes , 2002 .

[15]  D. Somerton Bridle efficiency of a survey trawl for flatfish: measuring the length of the bridles in contact with the bottom , 2003 .