PRELIMINARY OBSERVATIONS ON THE CAPTURE 

 OF FLATFISH BY TRAWLS 



C. G. Bublitz 



School of Fisheries and Ocean Sciences 



University of Alaska 



ABSTRACT 



The remote operated submersible Manta was used to conduct 

 behavioral studies on the capture of flatfish by commercial trawl 

 gear. Two types of behavior patterns were exhibited during the 

 capture process. The majority, 80%, of flatfish entered the 

 trawl by flipping backwards over the footrope then righting 

 themselves to a normal swimming position inside the net. Twenty 

 percent of the flatfish captured entered the trawl by rising 

 above the substrate, turning through 180° in the horizontal 

 plane, and swimming into the net. These behavior patterns appear 

 to be mediated by the visual field, in particular the field of 

 binocular vision. 



INTRODUCTION 



The impact of incidental catch by the expanding North 

 Pacific domestic trawl fishery has generated considerable 

 concern among other domestic user groups. Traditional user 

 groups are questioning the economic and ecological impact of 

 these fisheries on their sector of the industry. For example, 

 during 1985 incidental catch was estimated to have removed 

 between $20 and $40 million dollars of traditional, fully 

 utilized fish species in the Gulf of Alaska and Bering Sea. The 

 resultant conflicts have made incidental catch an allocation 

 issue in the North Pacific. 



Incidental catch is currently being managed by the use of 

 catch ceilings and restricted fishing. This approach has 

 resulted in the closure of large areas of productive fishing 

 grounds in the Bering Sea and Gulf of Alaska. In addition, once 

 incidental catch mortality ceilings have been reached, all 

 trawling must cease regardless of whether or not the allowable 

 biological catch of the target species has been taken. These 

 restrictions have impeded the development of productive near- 

 shore whitefish grounds and slowed the development of full scale 

 domestic shore-based whitefish processing. 



The increased effort being placed on North Pacific 

 fisheries resources requires the development of new methods to 

 control the incidental catch problem. Quantitative analysis of 

 fish behavior during capture by trawl gear may provide needed 

 information for the management of this problem. Information 



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