different from 1:1 ratio only in the spring, when 

 60*^^ of the ratfish caught were females. 



Discussion 



In Puget Sound, the ratfish was most abundant 

 from 55 to 99 m. While it should be noted that only 

 three sites were sampled below 100 m, and none 

 below 150 m, most of Puget Sound proper is shal- 

 lower than 150 m. Still, the depth distribution of 

 ratfish in central Puget Sound differs from that in 

 the Gulf of California (Matthews 1975). 



These southern ratfish were most abundant 

 from 257 to 400 m. After noting a peak of abun- 

 dance in February, Matthews ( 1975) speculated 

 that the ratfish move into very deep water during 

 the summer and fall, and return to shallower 

 water in the winter and spring. This would be 

 generally similar to the seasonal pattern of abun- 

 dance observed at the Puget Sound sampling sites, 

 where maximum abundance was in the spring 

 (April- June); later in the year, the fish were in 

 slightly deeper water. 



While the differences in overall depth distribu- 

 tion of the Puget Sound and Gulf of California 

 populations may be temperature related, and the 

 seasonal movements may be related to reproduc- 

 tion, these factors do not seem to explain the diel 

 movements of the Puget Sound population. One 

 possible explanation for the nocturnal onshore 

 movements of Puget Sound ratfish is that there is 

 some food resource which is being exploited in 

 shallow water. A study of ratfish food habits off the 

 Oregon coast (Johnson and Horton 1972) found 

 that 75% of the food items consumed were Am- 

 phissa sp., a gastropod mollusc. A study of ratfish 

 food habits from Puget Sound indicates a much 

 less specialized diet. Stomachs from 71 West Point 

 ratfish contained a wide variety of items ( Wingert 

 et al.'*). In general, smaller ratfish (<200 mm) fed 

 principally on polychaetes, but stomachs of larger 

 ratfish contained primarily bivalves, fish, and 

 decapods. While some food items such as limpets 

 and barnacles indicated shallow-water feeding, 

 the sample size was not sufficient to establish the 

 main feeding times or depths. Miller et al.^ and 



^Wingert, R.C., C.B.Terry, and B.S.Miller. 1979. Food and 

 feeding habits of ecologically important nearshore and demersal 

 fishes in central Puget Sound. Unpubl. manuscr, 83 p. Univ. 

 Wash., Fish. Res. Inst. FRI-UW-7903. 



^Miller, B. S., C. A. Simenstad, L. L. Moulton, K. L Fresh, F C. 

 Funk, W. A. Karp, and S. F Borton. 1977. Puget Sound 

 baseline program; Nearshore fish survey. Unpubl. manuscr., 

 220 p. Univ Wash., Fish Res. Inst. FRI-UW-7710. 



Fresh et al. also found wide prey spectra, with fish 

 and polychaetes being the most important items. 

 Ratfish seems to feed opportunistically on the 

 most abundant, available items and will eat a wide 

 range of crustaceans, molluscs, annelids, fish, 

 echinoderms, and algae. 



Whether or not the onshore movements are 

 food-oriented, we still must explain why most of 

 the small ratfish are found in deep water, and why 

 they apparently approach shore primarily at 

 night. One possible explanation is predator avoid- 

 ance. The large, poisonous dorsal spine and large 

 size probably make adults relatively safe from 

 predation, but perhaps not juveniles. During the 

 day, juveniles may tend to stay in deep water 

 where their blue-shifted retinal pigment may give 

 them an advantage over potential predators such 

 as spiny dogfish, Squalus acanthias (Jones and 

 Geen 1977). 



The Puget Sound ratfish population is exploit- 

 ing a nearshore niche. Its retinal pigment 

 (chrysopsin) and eye morphology are similar to 

 deep-sea chimaeroids, such as H. affinis, yet its 

 depth distribution is comparable to many fish with 

 retinal pigments located near 500 mm. By con- 

 trast, C. callorhynchus seems to be a more well- 

 established coastal chimaeroid, having a typical 

 coastal rhodopsin with peak absorbance at 499 

 mm (McFarland 1970). Hov^^ever, H. colliei has 

 some adaptations to an environment with moder- 

 ate light levels. Arnott and Nicol ( 1970) described 

 the histological basis of the reflective skin of the 

 species and explained this sheen as a camouflage 

 device by which the reflected light would match 

 the background illumination. The authors point 

 out that this reflective sheen is typical of 

 chimaeroids from moderate depths, such as 

 Chimaera monstrosa, C. cubana, C. phantasma, 

 and Callorhinchus callorhynchus, but that deep- 

 sea members of the group, such as H. affinis, have 

 dull-colored skin. Thus, C callorhynchus seems to 

 be well adapted to its nearshore habitat, H. affinis 

 is adapted to its deep-sea habitat, and H. colliei is 

 partly adapted to deep water and partly to shallow 

 water. 



While the visual system of//, colliei is clearly 

 suited to the deep distribution exemplified by the 

 Gulf of California population, it also seems com- 



^Fresh, K. L., D. Rabin, C. A. Simenstad, E. O. Salo, K. Garri- 

 son, and L. Matheson. 1978. Fish ecology studies in the Nis- 

 qually Reach area of southern Puget Sound, Washing- 

 ton. Unpubl. manuscr., 151 p. Univ. Wash., Fish. Res. Inst. 

 FRI-UW-7812. 



820 



