An assessment of discarded catches from the bottom pair trawling fishery in southern Brazil

Abstract

Onboard discards of a fraction of the catch can be considered one of the main issues related to bottom trawling fisheries. The magnitude and composition of the discards still need to be better understood. We assessed the industrial bottom pair trawling fishery’s discards from southern Brazil by monitoring 159 fishing hauls during four fishing trips. From the 318.9 mt captured, 77.7 t were discarded (24%). The discards per haul were highly variable, on average 488.9 kg (95% CI: 433.6-544.2 kg) and 31% (95% CI 28-34%) of the total. The rejected catch comprised 64 species, 37 teleosts (78.4% in weight) and 13 elasmobranchs (21.3% in weight), besides crustaceans, mollusks, cnidarians, and echinoderms. The three most commercially important species in the region (Umbrina canosai, Cynoscion guatucupa, and Micropogonias furnieri) accounted for 13% of the discarded biomass, and most of them were individuals under 20-25 cm. The discard rates and species composition did not change over the last 40 years; however, the discarded biomass for both teleost fishes and elasmobranchs decreased sharply, reflecting the abundance decrease of these groups in the region. This work highlights the need for management measures to reduce the bottom pair trawling fishery discards in southern Brazil.