Distribution, environment and biology of batoid fishes off Argentina, Uruguay and Brazil. A review.

Resumen

Available published and unpublished information on the distribution, environment and biology of batoid fishes occurring off Brazil, Uruguay and Argentina is summarized and reviewed for sixty species. Zoogeographic provinces proposed by Lopez (1963, 1964) are considered an adequate framework to define the distribution of these species. The Magellanic fauna, which includes the Pacific Ocean coast off Chile, is a well-defined biological unit. Conversely, the northern fauna changes gradually from the temperate Bonaerensean District off northern Argentina, Uruguay and southern Brazil, to a subtropical and tropical fauna along most of the Brazilian coast. The more drastic change to a truly tropical fauna occurs off French Guiana and Surinam. Within the area studied, rajids are the dominant batoid family, with a large number of rhinobatids and myliobatoids to the north. A more detailed cluster analysis (Jaccard) of batoid distribution patterns, results in nine groups largely corresponding with biological and distributional information: Group I of Magellanic species, Group II of three Magellanic species extending into the Bonaerensean District, a small Group III formed by the deep water skates Bathyraja schroederi, Amblyraja frerichsi and Dasyatis cf. pastinaca, another small Group IV of species with uncommon distributions, Group V of Bonaerensean species, Group VI of relatively rare deep water species, Group VII of northern migrants into the Bonaerensean District, Group VIII of Brazilian species occurring in both the South Brazilian and Brazilian districts, and a completely different Group IX of Northern Brazilian species with their southern distributional limit usually at Rio de Janeiro. A large amount of information is available on many of the species, regarding depth and temperature of occurrence, patterns of distribution, and in many cases reproduction and feeding. Preliminary evaluations of abundance have been obtained for a few species only, but the risk of overfishing is clearly documented for some of them. An odd taxonomic - geographic situation is the status of D. cf. pastinaca, and a peculiar type of cloacal gestation has been described for Benthobatis (similar to that in Squatina). Studies at community ecology level are discussed and full references provided, including many reports only published as meeting summaries.