Study on Turtle Excluder and By-catch Reduction Devices in the Philippines

Abstract

Experimental test-fishing of different TED types, namely : modified Thai Turtle Free Device (TTFD), Super Shooter (SS) and Hooped TED were conducted for eight (8) fishing days in March and April 1997 in Manila Bay. Assessment of the TED performance, i.e. its separating efficiency (escapement) and effect to catch (retained) was observed. Likewise, a single cod-end trawl (without TED) was also tested to serve as control. A total catch of 538.3 kgs. were obtained from thirty-two (32) sets of tow or eight (8) tows for each type. Of these, retained catch was 459.62 kgs. (85.38% relative abundance) while escaped accounts a total of 78.7 kgs. or 14.62% of the over-all catch. Lowest escapement was recorded in the modified TTFD with a total of 13.64 kgs or a mean escapement rate of 1.71 kgs. per hour of dragging (11.55% of the over-all catch). The modified TTFD, likewise, has the highest total of shrimps retained with 8.83 kgs or 1.10 kgs/hr (8.45% of the mean total retain) which is slightly higher than the control. Relative escapement rate for shrimps was recorded least in the SS with 0.05 kgs/hr followed closely by modified TTFD with 0.07 kgs/hr/drag. Initial results indicated that the modified TTFD has a better output if the TED performance factor to be considered were least escapement rate and higher shrimp catching efficiency. It is imperative that more test trials be conducted to validate each of the TEDs efficiency. Proof of the actual turtle release is also very crucial to support the use of trawl-fitted with TEDs. Some by-catch reduction devices were also tried. Sorting efficiency of shrimp selective devise with upper and lower panels was tested in shrimp trawl. Shrimps were expected to concentrate at the upper portion because of its behaviour. Preliminary results indicated that greater catching efficiency of the lower bag was observed. Catch difference between shrimps and by-catch at the upper and lower portion of separator grid was significant and sorting efficiency of shrimps from by-catch was low. Studies on square-meshed codends for trawl and Danish seine, and purse seine mesh selectivity are also presented.