patible with the distribution and behavior of 

 Puget Sound ratfish. 



While no quantitative measurements were 

 made of light intensity or wavelength, to the 

 human eye, the water in Puget Sound is quite dark 

 at 25 m during the day, especially in winter. Con- 

 sidering that the fish is most abundant at about 

 75 m during the day and generally moves near 

 shore only at night, McFarland's (1970) as- 

 sessment that its retinal pigment might be appro- 

 priate for its depth distribution seems to be cor- 

 rect. Other aspects of its visual system, such as the 

 apparently all-rod retina and nearly nonocclusible 

 tapetum seem generally appropriate to its ob- 

 served depth distribution. However, only more ex- 

 tensive studies of the feeding ecology, predators, 

 and possible competitors of ratfish can explain 

 why it moves onshore, why in some areas, such as 

 Port Townsend Bay, it is found in shallow water 

 during the day, and why in general it is found 

 closer to shore in Puget Sound than in other areas 

 in its range. 



In summary, the data indicate that in Puget 

 Sound, large ratfish predominate in shallow 

 water, and smaller ones in deeper water. The 

 species is most abundant in about 75 m of water, 

 and tends to be in slightly shallower water in the 

 spring and deeper water in the fall. Ratfish has a 

 pronounced nocturnal onshore movement, which 

 is composed primarily of smaller ratfish from 

 deeper water. 



Literature Cited 



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1970. Reflection of ratfish skin (Hydrolagus colliei). Can. 

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Beatty, d. d. 



1969. Visual pigments of three species of cartilaginous 



fishes. Nature (Lend.) 222:285. 

 CRESCITELLI, F. 



1969. The visual pigment of a chimaeroid fish. Vision 



Res. 9:1407-1414. 



Dean, B. 



1906. Chimaeroid fishes and their development. Car- 

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Denton E. J., and J. A. C. Nicol. 



1964. The chorioidal tapeta of some cartilaginous fishes 

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Hart, J. L. 



1973. Pacific fishes of Canada. Fish. Res. Board Can., 

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Johnson, a. G., and H. F Horton. 



1972. Length-weight relationship, food habits, parasites 

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JONES, B. C, AND G. H. GEEN. 



1977. Food and feeding of spiny dogfish (Squalus acan- 

 thias) in British Columbia waters. J. Fish. Res. Board 

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JOPSON,H.G. M. 



1958. A concentration of the ratfish, Hydrolagus colliei. 

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Lythgoe.J. N. 



1972. List of vertebrate visual pigments. In H. J. A. 

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 Maddock, R. G., and J. A. C. NiCOL. 



1978. Studies on the eyes of Hydrolagus (Pisces: 

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Matthews, C. P 



] 975. Note on the ecology of the ratfish, Hydrolagus colliei, 

 in the Gulf of California. Calif. Fish Game 61:47-53. 

 MCF.ARLAND, W. N. 



1970. Visual pigment of Callorhinchus callorhynchus, a 

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MOULTON, L. L. 



1977. An ecological analysis of fishes inhabiting the rocky 

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MUNZ, F W. 



1971. Vision: Visual pigments. In W. S. Hoar and D. J. 

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Thomas P Quinn 

 bruce s. miller 



College of Fisheries 

 University of Washington 

 Seattle, WA 98195 



R. CRAIG WINGERT 



College of Fisheries, University of Washington 

 Seattle, Wash. 



Present address: Marine Biological Consultants, Inc. 

 Costa Mesa, CA 92627 



DETECTION OF PETROLEUM HYDROCARBONS 



BY THE DUNGENESS CRAB, 



CANCER MAG I ST ER 



Behavioral responses that mitigate the effects of 

 natural environmental perturbations may also be 

 effective for contaminants from human activities, 

 but the occurrence of any behavioral response, 

 e.g., avoidance, first requires detection of the 

 contaminant (011a et al. 1980). To predict whether 

 a behavioral response to a chemical pollutant will 

 occur, one must ask whether the organism can 

 detect the pollutant at concentrations likely to 

 be encountered in field situations. Here we re- 



FISHERY BULLETIN: VOL. 78. NO. 3. 1980. 



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