TAXONOMIC IMPLICATIONS OF THE RESOURCE “BATOIDS” IN COMMERCIAL LANDINGS OF BOTTOM TRAWL FISHERIES IN SOUTHERN BRAZIL

Implicações taxonômicas do recurso “raia” nos desembarques da pesca comercial de arrasto de fundo no Sul do Brasil

Abstract

A survey conducted to study batoid species landed by the bottom trawl fishing fleet of Rio Grande, RS, Brazil, was carried out from 2001 to 2015. The objective of the study was to assess the diversity of batoids on the southern shelf of Brazil, a crucial area for the reproduction of this group. Understanding the taxonomic composition of this group is essential for conservation efforts. A total of 2,360 specimens were recorded, with 15 taxa identiϐied to species: Rioraja agassizii (n = 617; 26.1%), Sympterygia bonapartii (20.4%), Atlantoraja castelnaui (14.8%), Atlantoraja cyclophora (12.7%), Zapteryx brevirostris (11.8%), Sympterygia acuta (4.4%), Atlantoraja platana (1.9%), Dasyatis hypostigma (1.4%), Pseudobatos horkelii (0.6%), Myliobatis goodei (0.5%), Gymnura altavela (0.3%), Psammobatis extenta (0.2%), Psammobatis rutrum (0.2%), Psammobatis lentiginosa (0.1%), and Myliobatis freminvillei (0.04%). Among the batoids (‘raia’), there are several categories locally used by fishermen when separating the fish for processing in the industries. Skates (Rajiformes) are locally known as part of a generalized category called ‘emplastro’ by fishermen for commercialization. This category includes A. cyclophora, A. platana, R. agassizii, and juvenile A. castelnaui. However, it was observed that, within this fishing category, Myliobatiformes, especially smaller species, are often grouped together within ‘emplastro.’ Fishermen also classify ‘emplastro’ into ‘emplastro amarelo’ (yellow ‘emplastro’), corresponding to S. acuta and Myliobatiform pectoral fins, and ‘emplastro bicudo’ (long-beaked ‘emplastro’), which refers to S. acuta. The carcasses of A. castelnaui are processed separately and grouped as ‘emplastro pintado’, ‘raia pintada’, ‘raia marcela’, or ‘raia chita’. Rhinopristiformes are classified as ‘raia viola’ (Brazilian guitarfish), corresponding to P. horkelii, and ‘raia banjo’ (shortnose guitarfish), corresponding to Z. brevirostris. Females predominated (1,258; 53.3%) over males (n = 666, 28.2%), and a considerable number of immature individuals were recorded (n = 545; 23.1%). Pair trawling was the most commonly used method (82%) and was more likely to capture medium to large-sized species.

Keywords: Biodiversity, By-catch, Species conservation, Elasmobranch, Overfishing.