Nippon Suisan Gakkaishi 65 (2), 278-287 (1999)

Species- and Size-selectivity of SURF-BRD Trawl

Yoritake Kajikawa,*1 Akio Fujiishi,*2 Kimiaki Nagamatsu,*2
Tadashi Tokai,*1 and Ko Matuda*1

This study describes species- and size-selectivity of SURF (System of Unwants Ramp-way Filter)-BRD, which was developed to avoid by-catch of juvenile fishes smaller than marketable size and small crabs of no-commercial value in a shrimp beam trawl. The SURF-BRD comprised of two square-mesh panels (FP, front panel and RP, rear one of 40 mm mesh bar) and two escape-vents, and was installed on the bottom part of the net-mouth. Eleven tows with escape-vent cover-nets for catching escapees from the vent were conducted under three panel conditions: 5 tows with the FP and RP; at 4 tows, rear cover (RC) of the same mesh size as the codend was attached over the RP to avoid animals passing through the RP; 2 tows without the FP to examine the role of FP on selectivity of the device. The results of proportions caught in the codend to the total by species and by animal size indicated three routes of the animals to the codend: 1) swimming above the BRD without encountering the FP; 2) encountering the FP once and retained by it; and 3) passing through the FP and also through the RP. The RP needs to have enough small mesh like the RC, to lead animals out of the net through the escape-vent after passing through the FP. The SURF-BRD allowed some juvenile fishes and small crabs to escape from the net, while catching small shrimp of the main target species at night.


  [BACK]  [TOP]