Stock collapse of Umbrina canosai off Southern Brazil due to the introduction of mid-water trawl

Abstract

In recent years mid-water trawl fishing assisted by sonars and net mouth echo sounders made possible to catch schools of maturing and spawning argentine croacker Umbrina canosai that migrate northward, close to the bottom along the southern Brazilian outer shelf annually between the end of fall until the spring. Yields in 2011 and 2012 were exceptionally high, 11,805 kg/day coming to 20,000 kg/day, almost exclusive of Argentine croacker, four times larger than those of the over 300 pair bottom trawlers and bottom gillnet fishing boats that has the specie as one of their main target. The growing number of mid-water trawlers, plus the intense exploitation of the last 40 years, should serve as an alert to the high risk of collapse of the second species in importance in the demersal fisheries in the region. The collapses of fisheries with the introduction of techniques that increase the fishing power are nothing new in southern Brazil.