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55% Of Tuna By-catch And Discards In The Indian Ocean On FADs

The study ‘By-Catch and Discards of the European Purse Seine Tuna Fishery in The Indian Ocean-Characteristics and Estimation for the 2003-2007 Periodpresented on the last Indian Ocean Tuna Commission (IOTC) meeting confirms the higher incidence of discards and bycatch when using Fishing Aggregating Devices (FADs) on tuna fishing.

The paper, which has seven authors from France, Spain, Ivory Coast and Seychelles, focused its research on the European Purse Seine tuna fisheries in the Indian Ocean. The data collected came from observers programs started in 2003, which determined the period of the research – 2003 to 2007.

A total of 1.958 observed sets – 1.162 free schools sets, 762 log schools (FADs) sets and 34 sets on ocean floor mounts – resulted in 10.487 tons of bycatch and discards per year estimation.

From that number, 5.783 tons – or 55% - were caused by FAD fishing.

“Tuna discards and by-catch is higher on FAD sets than on free schools sets. This is very clear for finfish by-catch” states the study.

Concerning tuna discards, 57% was associated with free schools tuna fishing (4.352 tons) and 41% with FADs (3.115 tons). “It can be seen that main tuna species like bigeye, yellowfin and skipjacks are generally discarded when length is less than 40-45 cm” the study continues.
 
Young skipjack is the most vulnerable tuna species to FAD fishing. Nearly 53% of discards of the species was caused by this method. 

“Bigger species, such as yellowfin, represented around 10% of tuna discards associated with FADs”

However, the harmful effect of FADs is better seen on the bycatch of other marine life. The device is responsible for 96% of other fish species’ accidental catch, 92% of shark’s bycatch and 70% of billfishes’.

The only species estimated by the study to be harmed by free schools tuna fishing in larger quantities are rays – 64%.

“Tuna discards and by-catch were very low during the first quarter of the year (in this area) and grow sharply during the second quarter mainly due to tuna discards. The third and fourth quarters displays medium levels of total tuna discards and by-catch with high percentage of associated species. This pattern may be explained by the fact that during the first part of the year, the fishery is mainly operating on free schools while in the second part of the year FAD sets are predominating” finalizes the study.