Description
The brown crab, Caneer pagurus L., is a commercially important shellfish species in Europe, being exploited from Galicia (NW Spain), where captures have suffered an important decrease in landings, to Norway, where the species shows a stable stock and appears to be spreading northwards, and opening new potential fishing grounds. The main objective in fisheries management is to ensure the maximum harvested amount of the resource without compromising its viability. Design a sustainable management plan requires information on the stocks (managed units) of the harvested populations. Genetic techniques, in particular microsatellites, will be employed in this project to understand the population genetic structure of the edible crab throughout its distributional range. This work is important for the management of a shellfish product that is highly significant throughout Europe. The main beneficiary of the project will be the scientific community. This work will be carried out, in collaboration with University of La Coruña, project promoter, and the Institute of Marine Research (IMR) in Norway, donor partner, where they have great experience on this kind of studies for many commercial species. There is an s complementarity of the involved researchers, in terms of previous knowledge and methodology on one hand (ecology and life history from M. Pan, project applicant and population genetic and microsatellites from T. Johansen, donor partner), as well as in the animal material originating from both sites and the consequent geographic comparability.
Summary of project results
Genetic studies are common in fisheries sciences to understand population genetic structure of the exploited populations in order to implement appropriate management measures. Cancer pagurus is one of the commercially most important shellfish species in Europe. This work represents the first attempt to determine spatial genetic population structure of this fishery resource throughout its whole distributional range. A total of 1287 specimens of Cancer pagurus were captured in 14 different locations along the European Atlantic coast . DNA from a maximum number of 96 individuals per location was extracted from muscle tissue, followed by amplification of 12 microsatellite DNA loci by PCR using specific primers for Cancer pagurus. The PCR products were separated using an ABI3100 automated sequencer and the alleles were scored using the software GeneMapper v.5. The software Micro-Checker v.2.2.3 was employed to identify possible null alleles. GENEPOP 4.3 and GeneAlex softwares were employed to determine allele frequencies, Fst estimates, exact test for population differentiation at 95% confidence interval. Population differentiation analysis were performed using R, STRUCTURE, BAPS and Barrier softwares. The results obtained do not show a strong genetic spatial structure on the populations throughout its distributional range, but it appears to be some differences between locations shown by frequency analysis. Even though neither the geographical distance nor the water temperature were able to explain the differences observers, it appeared to be a latitudinal pattern, with the southern locations (mainly Bilbao but also Galicia) differing from the rest. A very interesting result regards Yorkshire samples. This location appears to be apart from the others. The result is consistent with the hypothesis presented by Eaton et al (2003) suggesting that the exploited crab stocks in south west North sea could be self-sustained. When performing the computation of barriers a new group emerged, composed by the three most latitudinal sites from the Norwegian coast: Vesteralen, Htra and Nordjord. Larval dispersal and adult migratory movements can explain some of the patterns and the low differentiation seen, But has also to be considered that the populations might not have sufficient time to diverge from a homogeneous founding populations. A deeper analysis shall be presented in more detail with planned scientific publications.
Summary of bilateral results
The project has been jointly developed. The grantee was hosted at the Norwegian institution and, during that period, she attended several scientific seminars held at the Institute of Marine Research and at the Fisheries Sciences Faculty at Tromso University. She also gave a seminar at the Institute and a talk at A Coruña University once back to her home institution. The present project has been important not only for the results obtained but for the cooperative links created for future initiatives. Both partners agree on the possibility of future collaboration in new projects involving both partners and third ones. The collected data will be a valuable base line for such projects and to investigate deeper the genetic structure of the crabs in a climate changing context and employing samples from different years. The DNA isolated and amplified for each sample has been stored in the facilities of the IMR and will be freely available. During the project development, fruitful contacts with several research institutes in Europe have been made and cooperative links have been established. It is especially important the collaboration started with other Norwegian researchers working on different aspects of Cancer pagurus. This is the case of the cooperation established with the Benthic Resources and Processes Group at the Institute for Marine Research in Bergen, with the Morefosking Institute, and with the National Institute of Nutrition and Seafood Research in Bergen. Besides, cooperation was established also with the School of Ocean Sciences (University of Bangor, United Kingdom), Marine Scotland (United Kingdom), and AZTI-Tecnalia Research Institute (Spain).