McEACHRAN and MUSICK: DISTRIBUTION AND RELATIVE ABUNDANCE OF SKATES 



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Figure 17. — Index of abundance (geometric mean) of Raja senta captured in each subarea during summer 1969 within 

 temperature intervals of 1°C. See Figure 3 for explanation of fractions and whole numbers. 



small part of the variance could be assigned to 

 the correlation, and the slopes were not significant 

 at the 5% probability level. 



Raja erinacea and/?, ocellata are predominantly 

 found at depths less than 111 m in areas w^hich, 

 according to Uchupi (1963) are covered v^fith 

 sand or gravel. They have similar responses to 

 seasonal temperature changes. In the southern 

 periphery of their ranges they move southward 

 during the colder months of the year and off- 

 shore and northward during the warmer months 

 of the year. Within their centers of abundance, 

 neither species undergoes a seasonal migration, 

 each being able to tolerate the seasonal tempera- 

 ture extreme. Raja ocellata appears to have a 



slightly lower temperature preference as sug- 

 gested by the difference in latitudinal distribu- 

 tion of the species. The apparent rareness of the 

 species pair in the Gulf of Maine may be due 

 to insufficient sampling. The shallowest depth 

 zone (27-55 m) was not sampled during the 

 Albatross IV cruises. Although the species have 

 similar habitat requirements their positive corre- 

 lation by numbers suggests that they are not 

 competing for the same resources. Also a study 

 of the food habits of the two species indicates 

 that R. erinacea feeds largely on epifaunal 

 organisms, and/?, ocellata predominately selects 

 infaunal organisms (McEachran 1973). 

 Raja laeuis is found in the same areas as the 



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