Survey of Stocks, Exploitation of European Lobsters in Brittany

16 July 2012, at 1:00am

This article presents the initial results from a program of stock surveys led by professional fishermen and funded via an innovative project of marine renewable energy, writes Laure Robigo, Departmental Fisheries Committee of Ctes dArmor, Brittany, France.

Framework: a project of marine turbines installed within a fishing reserve

A project of experimental marine turbines, conducted by EDF (Electricit de France), was initiated in 2005.

Very early in their project, EDF contacted the professional fishermen throughout the Local Fisheries Committee of Lannion- Paimpol (CLPM). Indeed, the waters coming under the legal competence of the CLPM were potentially useful for the exploitation of tidal currents and EDF wanted to involve all the stakeholders in this venture, especially fishermen. In order to have the minimum impact on fishing activity, the CLPM proposed to install the experimental devices within a fishery reserve area called La Horaine. This area was created in 1966 by the professional fishermen who wanted to protect crustaceans (lobsters, spiny lobsters, brown crab and spider crab); the exploitation of which is historically and economically very important. Thus, since 1966, all gear is prohibited in the reserve of La Horaine, excepted lines and long-lines. Technical studies showed that the request was feasible.

After a study trip in Ireland with EDF and a delegation of professional fishermen in 2007, discussions began between the company and the CLPM in order to decide what kind of partnership they wanted to established. Both of them agreed that funding a collective program on the resources exploited by the majority of the fishermen was better than giving individual financial compensation.

In June 2008, members of the CLPMs council voted by a majority in favour of EDF placing four experimental marine turbines in the Paimpol-Brhat area, placed within the reserve of La Horaine.

Then in 2009, the CLPM started to study the stock and the local European lobster fishery across the entire maritime district of Paimpol. The operational part of this study is funded by EDF; the working time is supported by the Dpartement des Ctes dArmor, the Rgion Bretagne and the European Fisheries Fund. The first experimental marine turbine was expected for autumn 2011, to be followed by three other turbines in 2012

The project area

A study led by the professional fishermen

The first stage of this study took place during the 2009 lobsters fishery, and involved 19 professional fishing boats. It consisted in notching a V mark in the tail of the female lobster, bought from a professional fisherman, and to release V-notched lobsters to the sea. As a professional or leisure fisherman caught a V-notched female lobster, he had to report it to the CLPM with the position of the catch. Of 1, 989 lobsters V-notched and released at sea, about thirty have been recovered. Such a small return did not provide a lot of information, but it helped greatly to advertise the program to the professional and the leisure fishermen.

From that first campaign, the CLPM repeated the notching campaign in 2010, with 1, 885 lobsters from 21 professional fishing boats. But in order to get individual information about displacements and growth, a yellow numbered tag was applied in the abdomen of each lobster, after the lobster had been weighed and measured. Lobsters were then released at sea by the CLPM, in 3 different areas, one of which was within the reserve of La Horaine. At the same time, a series of boardings of two professional fishing boats permitted sampling of all lobsters caught in pots, even lobsters under commercial size, through all season of lobster fishing. Sex, carapace length, number of pots used, area of fishing were noted to calculate indicators of exploitation.

In 2011, the same method of V-notched and numbered tag was applied on 1, 459 males and females lobsters from 13 professional fishing boats. The same kind of sample on board of the same two professional fishing boats was made. Furthermore, the CLPM put in place fishing within the reserve of La Horaine, with the intention of getting a long-term series of data to be compared with indicators of exploitation calculated out of the reserve. In that aim, three lines of pots were put in the reserve by the professional boats with the CLPM sampling the catches. Then all the pots, those put out of and those put in the reserve, could be sampled on the same day and a comparison could be made. Moreover, one line of pots put in the reserve of La Horaine was placed where the 4 experimental marine turbines were to be installed.

Measuring, tagging and releasing lobsters

Lobster movements

From the campaigns in 2010 and 2011, 73 tagged lobsters were recovered, 14 by leisure fishermen. Of those 73 lobsters, 34 are considered to show significant movements, while 35 didnt move from the point of release. The other four tagged lobsters had been bought by restaurants, fishmongers or by customers on markets, and their catch position was not known.

Almost all the lobsters that moved travelled in a westerly direction from the point of release. Some of these lobsters travelled very long distance in a relatively short time. For example, one lobster was caught 55 nautical miles from its point of release only 2 months later.

A few favoured recovery spots were noticed, such as the coasts of Ile de Batz, where 7 lobsters tagged in 2010 and 1 tagged in 2011, from different areas of release, have been found.

On the contrary, lobsters released in the Bay of Lannion, located at the West of the maritime district of Paimpol, seem to stay within the Bay. The circular marine currents and the closeness of a rocky seabed may keep them in that Bay. Further research on the causes of displacement is considered necessary.

Plotting results of lobster movements

An efficient fishing reserve

Sampling on board the professional fishing boats revealed a larger range of sizes within the reserve of La Horaine, compare to outside. In the same way, the mean carapace length seems to be bigger within the reserve, as is the mean weight. Moreover, the catch rate of commercial lobsters (i.e. where the carapace length is above the minimum landing size of 87mm) is higher in lines put in the reserve than in lines put outside. Thus, the catch per unit of effort (CPUE in Kg of lobster per 100 pots) is higher within the reserve compared to outside, whatever the season. To make a complete assessment of the reserve effect and to assure a correct survey of the stock of lobsters exploitation, the sampling has to be continued in the future in a similar way.

Above all the scientific results, this program make different sea users acting together

As said before, this program is partly funded by EDF, realized by a professional organization with the participation and for the interest of the local professional fishermen and supported by leisure fishermen. Actually, the associations of leisure fishery of the maritime district of Lannion-Paimpol are fully implicated in this program: fourteen of them reported re-catches of tagged lobsters in 2010 and 2011, and two of the lobsters that have been tagged were from leisure fishery. Being on board or in the harbours to tag the lobsters allows discussions with everyone working around the fishery industry, even with the general public. Information about the EDFs project or about the lobster fishery can be provided and a certain conception of the fishermen and their implication in improving knowledge about the stocks they are exploiting can arise from that kind of program.

July 2012