generated from this type of research can be applied to the 

 development of more selective fishing gear with the objective of 

 reducing incidental catch. 



Catch selectivity is inherent in the design of fishing 

 gear. Selectivity can be size or type specific and is dependent 

 upon a variety of factors. These factors include direct and 

 interactive effects of the gear which initiate or influence the 

 behavioral patterns of target and non-traget species. Factors 

 such as the effects of visual, auditory, chemical, and pressure 

 stimuli as well as swimming characteristics, learning, and 

 species interaction help determine how fish react to these 

 disturbances. 



Research on the capture of fish by gill and trammel nets, 

 set nets, pots, trawls, and longline gear have documented factors 

 which are important in fish capture and retention. Studies such 

 as McCombie and Berst (1969), Hamley (1975) and Marais (1985) 

 have concentrated on the relationship between mesh size and size 

 range of fish captured. These studies also discussed some of the 

 physical characteristics of fish which determine how fish are 

 captured. Rudstam et al . (1984) proposed that the probability of 

 a certain size of fish encountering a gillnet is directly related 

 to a fish's swimming activity. Matuda et al. ( 1984a, b) and 

 Matuda and Sannomiya (1985) examined factors such as rate of 

 entry, mouth width, leader nets, and fish schooling behavior in 

 relation to capture. 



Information generated on the capture of fish by trawl gear 

 has documented some of the effects of various trawl components, 

 sand clouds produced by the gear, towing speed, length of tow, 

 and mesh size and shape on the fish capture process ( Bohl 1980; 

 Brabant et al . , 1980; Rauck 1980; Sakhno and Sadokhin 1980; 

 Shevtsoy 1980; Thorsteinsson 1980; Main and Sangster 1981a, b and 

 1983; Briggs 1983; Robertson 1983; Jessop 1985; and Liu et al . , 

 1985). This information has already been applied to the problem 

 of separatinq species within the catch (Main and Sangster 

 1982a, b; Valdemarsen et al., 1985; and Briggs 1986). 



Vyskrebventsev (1968) classified fish into three main 

 groups based on their reactions to trawl gear. He linked the 

 distance at which detection and reaction took place to the 

 schooling tendency. Included in his classification scheme were 

 bottom non-schooling, in which the behavior exhibited was 

 determined by the near orientation of the gear; pelagic 

 scattered, where fish detected gear at some distance, but no 

 reactions took place until close visual contact was made; and 

 typically schooling when fish assessed danger and took 

 appropriate action before visual contact. 



In addition to fish/gear interaction studies, information 

 on biological and physiological factors such as swimming speed, 



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