CHARACTERISTICS OF FISHES 11 



record of a dogfish shark (Squalus) tagged off the Washington coast sub- 

 sequently being recovered off Japan^ 



Although geographic migrations of the type noted above are the best 

 documented movements of fishes, a number of species are known to 

 undertake seasonal vertical movements, and in some, large-scale diurnal 

 vertical movements occur. The Dover sole (Microstomus pacificus) may 

 move from relatively deep water along the continental slope (200 400 

 fathoms) in the winter, to the shallower water (60-150 fathoms) of the 

 continental shelf and upper slope during the summer months. 



The patterns of migration of fishes vary considerably between species, 

 and may vary within species, depending upon age. Among bottom fish 

 there is a general ''rule of the thumb" that the larger, older fishes will 

 inhabit deeper waters than the young (Heinckle's Law). There are many 

 causative factors responsible for fish movements. Local movements may 

 be related to changing physical or chemical conditions in the ocean or 

 varying food supplies^ The homing of fish to certain areas for spawning 

 is probably most closely related to the need to provide a requisite spawn- 

 ing media for the developing egg. 



The patterns of migration and behavior of fishes may have considerable 

 influence on fisheries which seek to harvest them. Some of the more pro- 

 nounced migratory patterns such as the movement of adult salmon, shad, 

 and other species to fresh water make them easily accessible to man. 

 Similarly, in ocean fishes the seasonal movement of fishes along coastal 

 areas and the movement of fishes into inshore areas for spawning are 

 patterns which have made these species susceptible to harvest. In addi- 

 tion to migrations, patterns of distribution play an important role in fish 

 harvest. Those species which aggregate into large schools such as herring, 

 cods, tunas, etc., can be taken in large quantities. However, those species 

 which are dispersed through much of their adult life are more difficult to 

 harvest and must generally have a high market value if they are to come 

 under exploitation. 



LITERATURE CITED 



1. Alverson, D. L., Fisheries Research Board Can., 14, 953(1957). 



2. Brett, J. R., and Mackinnon, D., ''Some Observations on Olfactory Perception in 



Migrating Adult Coho and Spring Salmon," Can. Progr. Rep. Pacific Coast Sta. 

 No. 90, pp. 21, Vancouver, B.C., Fisheries Research Board Can., 1952. 



3. Clemens, H. B., "The Migration, Age, and Growth of Pacific Albacore," As/iems 



Bull, No. 115, p. 1, Sacramento, California, Department of Fish and Game, 

 1961, 



4. Clemens, W. A., and Wilby, G. V., 'Tishes of the Pacific Coast of Canada," 



Bull. No. 68, Second Edition, University of British Columbia and Fisheries 

 Research Board Can., 1961. 



