An Ecomorphological Description of Malacoraja (Rajidae) in Waters of Eastern Canada

We examine the population structure, habitat associations, spatial ecology, morphometrics, meristics and reproductive attributes of two species in the genus Malacoraja of Canada. M. senta, the only shelf-dwelling species of the genus, is also atypical of Rajidae, and marine fish in general, in forming disjunct populations. This unusual spatial structure appears to be the result of a fragmented thermal habitat. At the northern, coldest extent of their range, M. senta occur only within the troughs where temperatures are >3 °C, comparable to the thermal habitat further south. M. spinacidermis, consistent with its other congeners, is slope-dwelling, reaching the highest density at >900 m, concentrating in 3.1–4.0 °C. The two species are of a similar size and body proportions but less spiny for M. spinacidermis. Body and tail size and spine counts underwent allometric changes with growth. L50 could not be determined for all populations, but Laurentian population L50 was 45 cm for females, 51 cm for males; Funk males, 45 cm. Size at first maturity was similar between species. This pattern of maturity is reflected in the secondary sexual characteristics. There was partial separation of maturity stages by depth for M. senta, with immature fish distributing in greater depths.