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February 2015
This newsletter describes the results of the BENTHIS project achieved in 2014.
The EU has funded the BENTHIS project to provide knowledge to support an integrated approach to the management of human activities in the marine environment, in particular fishing.
BENTHIS studies the vulnerability of different benthic ecosystems in European waters and analyses the physical impact of the current fishing practices on benthic organisms and geo-chemical processes. In collaboration with the fishing industry, technological innovations and alternative management scenario’s will be studied to mitigate the impacts.
www.benthis.eu
Contact: This email address is being protected from spambots. You need JavaScript enabled to view it. (IMARES)
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High-resolution mapping of European fishing pressure
For the first time, scientists have created high-resolution maps of fishing pressure in the North-east Atlantic, Mediterranean and Turkish waters. These maps provide a common knowledge base to all stakeholders and are needed for an ecosystem approach to fisheries management (EAFM). The level of detail goes beyond that of previous information based solely on fishermen’s logbooks that is not well suited for quantitative estimation of seafloor impact (swept area and impact severity) of the different gears and trips. The BENTHIS team has developed a method to overcome this information deficiency of official statistics.
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Hot spots and hot times: new insights in the impact of bottom trawling
Fishermen keep telling scientists that they don’t fish just anytime or anywhere. They tell us that these impact maps are wrong, only showing averages per year. No, they say, each fisherman will have his own preferred fishing grounds depending on the season. BENTHIS researcher Daniel van Denderen and colleagues dived into the data and modelled the implications for the seafloor ecosystem.
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Trawling impact is habitat dependent
In the Dutch North Sea, BENTHIS scientists found a negative relationship between trawling intensity and species richness. The scientist analysed data on the biomass and species richness of the seafloor community at 80 stations on the Dutch continental shelf for a 6 years period. Data were related to the trawling intensity, sediment grain size and primary productivity.
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Quantifying recovery rates and resilience of seabed habitats impacted by bottom fishing
How fast does the seafloor community recover after bottom fishing? Gwladys Lambert and her colleagues of BENTHIS’ partner Bangor University analysed thousands of pictures of the seabed around the Isle of Man (UK). In this area, bottom fishing shows a patchy distribution in time and space. For each location Lambert knew the history of fishing events, including when fishing had taken place for the last time, usually weeks to months earlier. The team counted all crabs, sea stars, tube worms, shellfish and other species on the photos and analysed the data. In the end, they obtained a database with the species composition of different habitats and locations in different stages of recovery.
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Winners and losers under fishery pressure: a biological traits approach
Usually habitats are classified according to their species composition: burying shrimps in combination with brittle stars in deep muddy waters, shellfish beds in the coastal zone, etc. BENTHIS scientist Andrew Kenny has a different approach: seafloor animals can be described according to their traits, they effectively represent “little packages of traits” which interact with their surroundings in different ways. Some species live a short time, others a long time, some are weak, others strong, some small, others large, some like to scavenge, or filterfeed. By using the traits, he explores the effects that fisheries have on different habitats.
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Impact of fishing gear: how big are the footprints of trawls and dredges?
Otter trawls for flatfish, dredges for oysters, beam trawls for shrimp: the variety of mobile bottom fishing gears in Europe is huge. And they all have different dimensions and impacts, which causes headaches to researchers who want to compare their impacts on the sea bed and the benthic ecosystem. BENTHIS researcher Ole Ritzau Eigaard and his team therefore carried out an industry survey. They wanted to obtain a standardized methodology enabling the prediction of physical impact of individual fishing operations from standard logbook information of vessel size, gear type and catch.
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Sediment remobilisation governed by hydrodynamic drag and not by weight of the gear
Many people think that the bigger the weight of the fishing gear, the bigger the impact on the seafloor. BENTHIS researcher Barry O'Neill has found that this is not always the case: and when looking at the amount of sediment put in to the water column, it’s the hydrodynamic drag of the gear that is the most important factor, not the weight.
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Otter trawling: good or bad for flatfish and Norwegian lobster in the Kattegat?
There is a lot of discussion on the effect of Marine Protected Areas on fish and biodiversity. Fishermen and NGOs usually have very different views on the benefits of MPAs. The Kattegat, between Sweden and Denmark, is a unique area in the sense that both intensively fished areas, as well as a number of MPAs with different levels of (long term) protection are present. BENTHIS researchers wanted to know how these different levels of fishing intensity impact three species of flatfish (dab, plaice, long rough dab) and Norwegian lobster (langoustine) and their food.
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Traps in the Aegean Sea: alternatives for trawling?
In the deep blue waters of the southern Aegean Sea (Greece) fish are traditionally caught using otter trawls, long lines and bottom nets. In the BENTHIS project, we are searching for alternatives to otter trawls, to reduce the impact of fishing on the seafloor habitat and community. BENTHIS fishery scientist Chris Smith, originally from the UK, has been living and working at the Hellenic Centre for Marine Research (HCMR) in Crete for over 25 years. He believes that baited traps could offer a good alternative to the traditional trawling: “From a theoretical perspective, the baited traps look very promising. They are designed to fish highly selectively, and they hardly damage the seafloor in comparison to trawling”.
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SPI on board
In BENTHIS the SPI camera is used alongside a number of other sampling techniques to look at the changes in the sediment prior to and after fishing. The sediment profile imaging (SPI) camera makes use of a prism that is inserted into the seabed to take photos of the profile of the sediment. Based on colour changes in the sediment inferences can be made on the function of the seabed in terms of biogeochemical cycling.
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Testing novel otterboards for the Mediterranean
In the BENTHIS project we also test novel semi-pelagic otterboards: doors that keep the mouth of the net open during fishing. Traditionally, otterboards dig through the seafloor, causing a turbid sediment cloud that scare the fish into the net. The aim is now to develop novel boards, that partly hover over the seabed, to reduce their impact on the seafloor community. In Italy two companies, Grilli and Mori, started the development under the scientific support of CNR.
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Effects of chronic bottom fishing on ecosystem functioning in the Irish Sea
Ever wondered what the impacts of bottom fishing are for those surviving the blow? In July 2014, BENTHIS took to the sea on board the RV Prince Madog, a state-of-the-art research vessel, to quantify the effects of chronic and large scale bottom fishing. The team, led by marine ecologist Marija Sciberras of Bangor University, studied the effects of fishing on the benthic ecosystem functioning in several different habitat types.
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Mitigation of effect of towed fishing gears in the Black Sea
In the Black Sea, in the Samsun Shelf Area, BENTHIS has conducted a series of experimental surveys to reduce the impact of beam trawls and bottom trawls on the ecosystem. The experiments were conducted in July and August 2014, using commercial fishing vessels. The research team used novel and traditional beam trawls for the Rapa whelk fisheries, to determine their effects on the benthic habitat. The novel gear had modified shoes which prevented their penetration into the substratum. The efficiency of these gears were discussed with stakeholders. In comparison with the conventional beam trawl, both bycatch and fuel costs were reduced.
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