FISHERY BULLETIN: VOL. 73, NO. 1 



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TEMPERATURE 



Figure 18. — Index of abundance (geometric mean) of Raja senta captured in each subarea during autumn 1969 within 

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



above species pair but has wider substratum and 

 depth tolerance. Its low abundance may in part 

 be explained by its considerably larger maximum 

 size (Bigelow and Schroeder 1953) which makes 

 it less available to the sampling gear. 



The distribution of the R. senta-R. radiata 

 species pair complements that of the/?, erinacea- 

 R. ocellata species pair. The former is found 

 predominately in areas which, according to 

 Uchupi (1963), were covered with sandy silt to 

 silt and clay. They are taken over a narrower 

 and lower temperature range than R. erinacea- 

 R. ocellata and generally occur below 110 m. In 

 the southern periphery of their ranges they are 



limited to a narrow band on the continental 

 slope where the waters are thermally stable 

 (Bigelow, 1933). Neither species appears to make 

 seasonal movements. Raja radiata appears to 

 have a wider temperature range and a lower 

 temperature preference, and it is the more abun- 

 dant of the two. The low abundance of/?, senta 

 may explain the lack of a positive or negative 

 correlation by numbers between the species. 



SUMMARY 



Below the geographical, temperature and depth 

 distribution of each species, based on literature 



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