Last month I returned from sea after two back-to-back trips where I tested the efficiency of mitigation measures in reducing seabird mortality on longline hooks. Similarly Martin was at-sea at the same time performing the same experimental work on a different vessel.
As well as participating in the capsule experiment (see ATF diary entry), our main aim was to finish the collection of at-sea data that we started this time last year. The experiment was set up to identify whether tori lines reduce seabird mortality in pelagic longline fisheries. We have had the full support from Pelagic Resources Department of the National Department of Aquatic Resources to complete our studies and on completing the studies the results look very promising.
From the data we collected in 2009 we felt sure that we were going to be able to show confidently that our mitigation measure was effective, but we knew we would need more data to make firm conclusions. During 2009-10 we completed eight fishing trips on commercially-rigged vessels. During days when longline gear was set without using a tori line, a total of 25 birds were caught. However, on lines set under the protection of a tori line not a single bird was killed.
The tori line did become entangled with fishing gear on a high proportion of the days it was used. In these cases the weak-link we have included close to the end of the tori line breaks and the rest of the tori line is left flying and still prevents seabirds gaining access to the baited hooks.
We are very pleased with the results as they show that the tori line is efficient at reducing seabird mortality in Uruguay, and as such we have a mitigation measure that we can apply to prevent seabird bycatch.
Obviously we still have a lot to do, including testing ways to increase the sink rate of fishing gear, and improving the use of night setting as a standard practice as these measures are complimentary and work best when used in combination.
For the tori line, we need to reduce the entanglements to make sure it is a measure that the fleet will use voluntarily and achieving this is a big challenge for 2011.
Written by, Sebastian Jimenez, ATF Uruguay