Trawler. (Photo: IEO)

Innovative technology and management measures improve ecological trawling efficiency

SPAIN
Saturday, August 19, 2017, 02:30 (GMT + 9)

Scientists from the Balearic Oceanographic Centre of the Spanish Institute of Oceanography (IEO), in collaboration with fishermen from the Balearic Islands and Cataluña, have evaluated different measures to reduce the direct and indirect impact of trawling in ecosystems.

The results of their studies, recently published in the journal Marine Policy, show that the new technological improvements and innovative management measures analyzed make it possible to reduce the impact of trawling gear on the seabed, improve its selectivity and reduce fuel consumption In this fishery.

As a measure of innovative management, a change was made in the work routine in the trawling fishery that is carried out in the Gulf of León, which consisted of moving from a daily activity, between 12 and 16 hours during the five working days of the week to a continuous activity for 48 hours per week.

On the other hand, the technological improvements, which were carried out in trawlers from Mallorca and Menorca, consisted of the use of smaller hydrodynamic doors or doors that do not contact the seabed, shorter warps and wider-mesh nets in its previous part, to increase its filtration capacity.

In addition, the codend mesh shape was also changed, from a diamond one of 40 millimetres to a square one of 40 millimeter, the mesh in force since 2010.
The three experiments were carried out under commercial conditions to demonstrate the applicability of the results.

Changing the codend mesh shape improves the selectivity of trawling gear, reducing discards, while the use of doors that do not touch the seabed makes it possible to reduce their direct impact on the seafloor.

In both cases, there has been no change in the composition of landed catches or a reduction in commercial yields. In addition, the change in the work routine allows to decrease sailing and even the effective fishing time. This leads to a lower fuel consumption, which is also achieved with the boards that do not contact the seabed and the lighter gear having mesh that is larger in size, which also results in a reduction in operating costs and, therefore, contributes to maintain the yields.

By eliminating the contact of the boards with the seabed and decreasing the discards and the fuel consumption, and therefore the emissions of greenhouse gases, it is possible to reduce the direct and indirect impact of the trawling fishery on the ecosystems.

"The implementation of these measures would not only improve the ecological but also the economic efficiency of this fishery," says Beatriz Guijarro, the first author of the study.

The article also recognizes that if these new technologies and the innovative management measure are implemented, it will be necessary to establish additional regulations that avoid their potential negative effects. Among them, the increase of the trawling speed and/or of the net sizes and greater accessibility to zones that are really far from the ports, where little or no fishing takes place.

The measures to be implemented will depend on the characteristics that are typical of each zone, which should be evaluated to ensure benefits and reduce risks. Only in this way will it be possible to improve the ecological trawling efficiency, an essential aspect for the sustainability of this fishery.

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