Evaluation of sampling gear for demersal resource surveys

摘要

The three demersal trawls evaluated were 38 m HSDT-II, indigenously developedudby CIFT for deep sea fishing in Indian EEZ; and two imported designs, viz.,ud45.6 m Expo model demersal trawl and 50 m fish trawl operated from vessels of FSIudand IFP, respectively. Vertical opening at trawl mouth was heighest for 50 m fishudtrawl (3.2 m), followed by Expo model demersal trawl (2.5 m) and 38 m HSDT-IIud(2.2 m), due to differences in overall dimensions and design features. Estimate ofudhorizontal opening between otter boards was highest for 38 m HSDT-II probably dueudto low drag of the gear, followed by 45.6 m and 50 m trawls. Lowest catch per unitudeffort obtained by 38 m HSDT-II is presumably due to smaller dimensions of the gear,udlarger codend mesh size and difference in ground rig, in addition to chance factors.udHowever, 38 m HSDT-II scores on several features desirable in demersal samplingudgear such as simplicity in design and construction, ease of operation; lower twineudsurface area and drag; and ground rig suitable for wider range of bottom conditions.udModifications to make it more effective while sampling for crustaceans and small sizedudfinfish components are described.