Posted by Jefferson Murua
22 October 2012
Dr. Jefferson Murua is a scientific marine researcher with Spain’s AZTI-Tecnalia and leads skippers’ workshops for the International Seafood Sustainability Foundation (ISSF).
On September 8, 2012, David Itano and I met with 75 skippers in General Santos to talk about ways to reduce bycatch. The Philippine domestic tuna fishery is conducted exclusively on anchored FADs, also known as payaos. Its fleet is mainly made up of many small to medium sized purse seiners and the catch is primarily small sized tuna and tuna-like species. All tuna are utilized.
The skippers participating in the session noted that they rarely see sharks near their FADs, and that if they do, they will cut the net to let them escape. These skippers use skin divers, they call “boceros”, to estimate the size of the potential catch, rather than echo sounders – they said that the diver’s estimation was about very similar to the actual catch (i.e. 80 percent or closer). In addition, they noted that the depth of a biomass can indicate the kind of fish present – a biomass from 5 to 10 fathoms is usually bait and bycatch, while a biomass of 10 to 15 fathoms is usually skipjack tuna. A biomass located at 60 to 80 fathoms is usually yellowfin or bigeye tuna.
During the session we discussed new ways to move non-targeted species, like sharks, away from the FADs (by using red meat rather than tuna or fish to lure them away), suggested that they use a hand net with a long handle to scoop up any sharks swimming on the surface when sacking up. The use of underwater ropes with biodegradable coco and palm leaves to attract fish when building their anchored FADs is widespread, rather than other entangling materials like nets used in drifting FADs.
We met with about 50 skippers on September 11th in Bitung for our first Indonesian workshop. The Indonesian fleet in Bitung is composed of small sized purse seiners (10- 200GT) fishing exclusively on payaos. They use all the fish they catch (so there’s no “discards” as such) and catches per set are relatively low, about 1-20 tons for a medium size vessel. Nets are lifted by men, not power blocks, which necessarily limits the size of the catches. Companies use small boats or ranger boats to support purse seine operations like maintenance of payaos.
These skippers also noted that the depth of a biomass can indicate the kind of fish that are present, and stated that they rarely encounter sharks. They estimated that they catch an average of 1 to 3 sharks for every 10 sets they make. Turtles are always released, as are dolphins if they are accidentally caught, as they can risk breaking the net. These skippers use an echo sounder before a set to assess the composition of the fish below.
During the session, we learnt about the use of coconut fronds as attractors under the payao. These natural attractors need to be replaced almost weekly, as the leaves degrade rapidly. Some vessels use divers at the surface with goggles to help them pre-estimate biomass and species under the payao. Finally, in an effort to lure bycatch away from the payao, fishers tie a boat with a light source to the payao an hour before they set for the catch. Just prior to the set, the speedboat with the light is drifted slowly away 500 m to 1km keeping the tuna under it, while the FAD pontoon remains in the same place with the bycatch (almost like a double-FAD scenario).
For our final session, we met with 29 skippers in Jakarta on the 13th of September. The Jakarta PS fleet is composed primarily of small sized purse seine vessels, currently having 102 vessels between 51-100 GT and 160 vessels of 101-200 GT. The purse seine vessels unload at port 3 to 4 times a year. Unlike the Bitung fleet, the Jakarta PS do not have ranger vessels. The larger vessels operate in the Indian Ocean west of Sumatera. They catch tuna and tuna-like species, jacks and miscellaneous fin fish. Vessels are equipped with Refrigerated SeaWater holds to chill catch and blast freezers. The catch is sorted to species and frozen in steel pans at -20 to -25C.
As in the previous two workshops, these skippers reported very few sharks found in their sets. Again vessel’s nets are lifted by hand or with a capstan, rather than with a power block.
At this session, we discussed different ways to lure bycatch away from the set. Fishers believe that when the light in the payao is turned off some bycatch species leave the area. These fishers often put a light boat (a small canoe with a 1000 watt light) near the payao an hour prior to the set. The canoe has also coconut leaves hanging under it (10 m depth) to “trick” the tuna into thinking it is a payao. While the lightboat is slowly drifted away, the payao remains anchored to the bottom. Fishers believe the non-tuna species often remain with the payao as the light boat and tuna moves away from the anchored FAD. In addition, these fishers believe that the spectrum of light is important, and that a larger light is more likely to attract larger schools.
These practices reported by Philippine and Indonesian skippers show the potential that the use of light holds as an important stimulus to manipulate tuna and bycatch behavior at FADs in trying to separate target and unwanted fish species at FADs.
Our next round of skipper workshops will be held in the Sukarrieta (Spain). We’re looking forward to sharing information with the local fishers and learning more about the local ecology and FAD designs so that we can continue to add to the growing body of knowledge we have about what works and what doesn’t when promoting a sustainable future for tuna.