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“Smarter fishing” to conserve the seafloor: dream or future?
Technical fishing gear innovations appear to be the solution toward sustainable fisheries. But what can be done from a management perspective? Marine protected areas often evoke a lot of resistance. In the BENTHIS project, marine ecologist Gerjan Piet and his team are now developing a decision support tool that appears to have high potential. Piet explains: “We wondered if it would be possible to reduce the impact to the seafloor without extra costs, by influencing the fishermen’s behaviour. The idea is that they are provided with accurate maps of vulnerable habitats, so they can avoid sensitive areas.”
As a first step in the development of this tool, the researchers reconstructed the distribution of the fishermen over the North Sea, to back-calculate their impact on the bottom fauna. They used data of approximately 300 fishing vessels, covering the period 2010-2012 and about 14.000 trips (30.000.000 kWdays). For each vessel, the fishing locations were known, based on VMS satellite data.
Next they divided the North Sea into grid cells, and estimated habitat quality per grid cell which determines the vulnerability to fisheries. A habitat which has been trawled in the previous year will have a lower quality and is less vulnerable. This vulnerability then determines the impact of any new fishing activities. This impact is determined by the type of gear and the sensitivity of the habitat. For example, a grid cell with predominantly hard substrate covered by e.g. soft corals will suffer a bigger impact than one with a sandy seafloor. Fishing impact is expressed as the amount of time it would take to recover to the state prior to impact.
By combining the fished routes with the vulnerability data, Piet and co-workers observed a huge difference between fishing trips depending on the strategy of the fishermen: some fishermen are more conservative and go to the same patches every year, others display more exploratory behaviour and go to new areas that have never been fished and thus suffer from a bigger impact. The most striking result, however, was that the CPUE (catch per swept area) of the conservative fishermen was higher, even more so if the amount of catch was compared to the actual damage caused to the seafloor.
It appears that smarter fishing using spatial information on the vulnerability of the seafloor can reduce the impact on the seafloor by a factor 5-10 without compromising the catch opportunities. Piet: “This proves smarter fishing has the potential to conserve the seafloor and should therefore be considered as part of ecosystem based fisheries management.” The next step will be taken later this year, when Piet and others will discuss these results with a group of fishermen as part of the ICES WGMARS, to discuss these results and the possibilities for application as part of their regular fishing practices.