| 英文摘要 |
The FAD by-catch problem in purse seining fishery impacted bigeye resources seriously. It is important that how to reduce by-catch of them is therefore a serious crisis being faced by purse seine fishery. However, WCPF will forbid using FAD in order to reduce the dead rate of juvenile bigeye which caused by by-catch. Therefore, FAD is the serious problem in the purse seining fishery. We analyzed the logbook data from observers during 2002 to 2005 and the result shows that the discard percentages of FAD and unassociated schools are 2% and 5%. The logbook data from purse seining boat also shows that the utility rate of FAD reduces year by year. Therefore, the impact of the ban on fishing FAD would not be a major problem of Taiwan purse seining fishery. Except forbidding using FAD dierectly, this study also plan to identify the condition of fish aggregated by FAD prior to fishing action. With the acoustic theory, measurement in cage (optional) and in-situ experiments, this study aim to analyse the features of echograms/signals collected by echo sounders to differentiate characteristics of schools aggregated by FAD. Then, brought up the possible way to reduce the bycatch of the juvenile yellowfin and bigeye. Besides, about the experiments of identification of juvenile yellowfin and bigeye by acoustic method, we were not successful because the buoy was stolen while it worked on the sea. However, the data from water pool experiments and VGA recorder images indicates that it is possible to explain echo characteristics of yellowfin and bigeye, although we still need more data and time to analyze. Now we cooperate with the Coastal and Offshore Resource Research Center in Fisheries Research Institute, COA. We will continue to work on acoustic surveys in moored FAD near the East-southern Coastal Taiwan water, collect fish echo information from schools aggregated by moored FAD, and find the technology of identifying juvenile yellowfin and bigeye. |