MITIGATION MEASURES AND FISHERIES: SOLUTIONS FITTED TO EACH CUSTOMER
In a round table, the participants to the meeting contributed with their knowledge in both, fishing arts and mitigation measures, in order to assess potential solutions for each fishery. The session was conducted by Luis Mujica, manager of a fishing company in Chile. All known mitigation measures for each fishing art were mentioned and their viability commented. Details of the discussion are presented bellow.
This fishing art is common in Peru and Chile. There is no data on seabird bycatch but opportunistic observations indicates no fatal interactions in this fishery. Peru, through their observers onboard anchovy fishery vessels will undertake preliminary assessment of the interaction between seabirds and the fishing operations. No mitigation measures exist for this fishery.
This fishing art is widely common in the area. Observations carried out by the Seabirds at Sea Team Falkland Islands (Malvinas) had identified three ways of interaction of seabirds with fishing gear, all of them with potential fatal consequences:
i) interaction with the net while it is floating, previous to be hauled onboard;
ii) collisions with the net-sonde cable;
iii) collisions with the warp cables.
Mortality in the first case occurs by birds being entangled with the net while trying to steal some fish. Mesh size seems to be a key factor on seabird entangled rate, with larger sizes presenting large number of net-entangled birds and, therefore, incidental mortality rates. Potential mitigation measures include a better management of the hauling operation, in order to reduce the surface time of the net, and to clean up the net before each setting, in order to reduce attractiveness for seabirds.
Mortality by collision with cables (sonde and wraps) happens because of seabirds being distracted consuming the discards thrown almost constantly to the sea. Consequently, first mitigation measures are to accumulate the offal and discards onboard. Eventually, this material could be use to produce fishmeal (i.e., as happens in New Zealand fisheries) or its expulsion been planned in order to discharge the whole lot at once and not in parallel with the trawling operation. Secondary mitigation measures include the use of bird-scaring devices. There are two of this devices, streamer lines and Brady Baffler. The streamer lines are similar to those used in longline fishing and its aim is to prevent birds to approximate the cables. The Brady Baffler consists of two curtains of ropes and plastic cones, one on each side, that prevent seabirds from gathering in the area adjacent to the warp cable (Southern Seabirds Solutions 2002). Risk of collision with the netsonde cable could be eliminated by use alternative technology that not require this cable. Netsonde cables have been banned in New Zealand and CCAMLR waters since 1994/95.
This fishing technique is used to catch common dolphinfish offshore Brazil. The hooks remain close to the surface all time and thus they represent a potential menace during the whole operation. The only mitigation measures known are the use of streamer line during setting, night setting and, under experimental stage, the use of blue-dye bait. Additionally, avoid offal discharge during setting increase the efficiency of the former mitigation measures.
Middle water longlines
This fishing technique is used to catch tuna, swordfish and sharks. Mitigation measures developed for this fishing art includes use of streamer lines, add lead-weights to the hook or noodles, blue-dye of baits and night setting. Additionally, avoid offal discharge during setting increase the efficiency of the former mitigation measures.
The use of streamer lines, when properly designed and operated, is an effective mitigation measure, particularly when use altogether with night setting. Add lead-weights to the hooks or noodles could be a palliative way to increase the sink rate of this line during setting, because add weights to the main line as in bottom lines is not applicable; however, essays at the moment had not been successful, mainly due to the low weight added. Blue-dye of bait has a very good prospect, particularly if used altogether with streamer lines and night setting.
This fishing technique is used to catch demersal species as hake, ling, hoki, southern blue whiting and Patagonian toothfish. The mitigation techniques used with this fishing art includes streamer lines, add weight to the main line and night setting. The proper use of this whole set of mitigation measures had demonstrated to reduce effectively the seabird incidental mortality.
Although fatal interaction between seabirds and fishing gear happens mainly during setting, non-fatal interactions during hauling could be important in some cases. Mitigation measures, such as offal discharge at the opposite side where the hauling window is placed, and use of streamer lines or a water curtain around the hauling window are altogether efficient measures to avoid interaction between seabirds and the hooks being hauled. More recently, some fishing vessels have a moon-pool inside the ship that allows hauling the line under extreme weather conditions; this configuration also avoid any contact between seabirds and the line being hauled.