The streamer line, also known as a bird-scaring or tori line is a mitigation measure that reduces seabird bycatch in longline fisheries. It is recommended that they be used in combination with night setting and line weighting. The efficiency of streamer lines has been demonstrated by our team in the Uruguayan pelagic longline fleet over the past couple of years. As part of the project I recently headed out on a trip to continue working on the design and practical use of this mitigation measure.
Beyond the initial on shore work of finding the relevant materials to construct the streamer line there is important actions in port to configure a support system that holds the streamer line in place. In Uruguay we have developed a system that allows the streamer line to be manually manoeuvred from port to starboard, depending on the wind direction, which improves the efficiency of the device. However, this trip had a major challenge for us.
Despite the streamer line being very efficient, it still requires some improvements to reduce entanglements with fishing gear which can lead to the streamer line breaking under tension. Therefore, we have made some modifications, including the use of more resistant materials and reduction in the size of the in-water extent plus some other small changes.
Below: Crew set longline gear as the streamer line flies in the background
Making it possible to change the streamer line from port to starboard has been an important feature. This is because when the wind changes direction or the vessel alter course, the streamer line can be blown over the fishing gear which increases the likelihood of entanglement. These modifications have worked well so far resulting in fewer entanglements whilst keeping seabirds well beyond the area of greatest risk.
This modification is very important for a vessel working hard with a small crew, and is very positive to have a device that can be managed by one person which works rapidly and simply. Without this modification it may be necessary for more than one person to adjust the streamer line during setting operations.
We believe that the results of this trip are positive, that the streamer line has been more durable than previous years, managing to effectively cover the most critical area where seabirds attack baited hooks. This trip complements the other positive results that have been obtained made by the ATF-Uruguay team in 2012. Everything indicates that the advances we have made are working well.
Interestingly, during our work at-sea 22 species of birds were observed around the vessel. This large diversity is common in winter, where amongst the ever-present Black-browed albatross Thalassarche melanophrys and White-chinned petrel Procellaria aequinoctialis there were vulnerable great albatrosses of the Diomedea family and southern species such as the Southern fulmar Fulmarus glacialoides and Antarctic prion Pachyptila desolata. Also present but in lesser numbers, were species that prefer slightly warmer waters like the Spectacled petrel Procellaria conspicillata and Yellow-nosed albatross Thalassarche chlororhynchos.
Below: A Wandering albatross with very strong beak colouration followed the vessel
An interesting visitor on this trip was the Soft-plumaged petrel Pterodroma mollis with up to 39 individuals seen feeding and competing for discards. Although this species is commonly seen around vessels, it is unusual for them to approach so close and in such large numbers (normally only one or two appear).
On one day, perhaps because of the absence of other species, we also had a few Atlantic petrels Pterodroma incerta following the vessel and descending to feed on discards.
I shall be returning to sea shortly to continue our work with industry, working to improve and implement mitigation measures in this fishery.
For this blog I am posting on behalf of my friend and colleague Rodrigo Forselledo: