Preliminary analyses; evaluation of the effects of the newly employed seabird bycatch regulation for longline fisheries in IOTC conventional area with using current observer data
The new seabird mitigation regulation was enforced in July 2014 in the area south of 25S in IOTC convention area. It demand for fisheries to adopt two of three mitigation measures of tori-line, night setting and blanch line weighting which have high effectiveness for mitigation of seabird bycatch (Melvin et al. 2014, Sato et al. 2014). In this document, Japanese seabird by-catch data in the south Indian Ocean (south of 25S) collected by on-board observers in the period before and after the introduction of the new regulation were reviewed, to explore the possibility to evaluate the effectiveness of the new mitigation measures. It seems that the distribution of the observer data collected form almost main fishing areas of Japanese longliners in the period analysed. The observer data indicated that many Japanese tuna longline vessel (71-94%) had already adopted the combination use of weighting blanch line and Tori line or night setting and Tori line before the introduction of regulation (2012-2013). This would be mostly due to the fact that bait loss by seabirds is one of serious concern of Japanese fishers but also suggest their positive attitude toward seabird conservation. The amount of data seemed insufficient as data after the introduction of the new regulation was only one year, analytical method supposed to be rather preliminary. However, the good efficiency of the regulation with using fisheries data, further collection of data appeared to be necessary for the stochastic evaluation of the effect of new mitigation measure, such as considering the effect of the interaction of each mitigation, target species. Also, the detail situation when the mitigation measures were used would be needed to investigate in the future.