the footrope indicate the fish may be swimming near the 

 limits of visual contact, determined by contrast 

 discrimination, with the footrope. 



CONCLUSION 



Initial orientation to trawl gear is probably a 

 reaction to audio rather than visual stimuli. Responses to 

 these stimuli would probably result in fish orienting 

 themselves in the most advantageous position to react to 

 visual stimuli produced by the gear. Herding appears to be 

 mainly in response to the visual stimuli produced by the 

 footrope. As with roundfish, herding times and entry into 

 the net appear to be determined by the fish's swimming 

 ability. 



The two types of entry behavior exhibited appear to be 

 positional rather than either size dependent or related to 

 the relative swimming ability of the fish. The visual field, 

 in particular the binocular field of vision, appears to play 

 an important role in determining the relative position of 

 reactions to the footrope. This factor probably determines 

 the position at which fish exhibiting entry sequence A right 

 themselves to their normal swimming position. It may also be 

 important in determining the position at which flatfish 

 initiate entry into the net. 



LITERATURE CITED 



Anthony, P. D. 1981. Visual contrast thresholds in cod 



Gadus morhua L. J^ Fish. Biol. , Vol. 19, pp. 87-103. 



Anthony, P. D. and A. D. Hawkins. 1983. Spectral 



sensitivity of the cod, Gadus morhua L. Mar. Behav. 

 Physiol. , Vol. 10, pp. 145-166. 



Arnold, G. P. 1969. The reactions of the plaice 



( Pleuronectes platessa L. ) in water currents. J_^ Expl . 

 Biol. , Vol. 51, pp. 681-697. 



Arnold, G. P. 1974. Rheotropism in fishes. Biol . Rev. , 

 Vol. 49, pp. 515-576. 



Batty, R. S. and C. S. Wardle. 1979. Restoration of 



glycogen from lactic acid in the anaerobic swimming 

 muscle of plaice, Pleuronectes platessa L. J^ Fish. 

 Biol. , Vol. 15, pp. 509-519. 



Blaxter, J. H. S. and R. S. Batty. 1985. Herring behaviour 

 in the dark: responses to stationary and continuously 

 vibrating obstacles. J^ Mar. Biol . Ass. U.K. , Vol. 65, 

 pp. 1031-1049. 



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