The nephropidae family comprises of three species of lobster belonging to the genus Homarus: Homarus capensis, Homarus americanus, and Homarus gammarus. The latter is of significant commercial importance, historically and presently, throughout Europe; fished extensively throughout its range (see Fig1.) by pots and traps. Notable H. gammarus fishery collapses combined with the economic value of this species has been an incentive for extensive research into its biology and ecology. This has led to the establishment of sustainable initiatives, such as hatcheries, seeking to ensure the future of this lucrative fishery. However, there still remains a great deal to learn for its successful management (Phillips, 2006).
H. gammarus is characterised by the first periopods of adults being modified into a pair of distinctive large anterior claws (Fig2.): a large crusher claw, for cracking and breaking open prey shell or carapace, and a smaller cutter claw, to slice and grab. This formidable feature has aided in its survival throughout the coastal regions of much of Europe and into Northern Africa.
Within its range, landing sizes fluctuate considerably from region to region due to a variety of factors- known and unknown. This includes behaviour, for example lobsters seek crevices for habitat, suggesting that the benthic composition is a possible limit to population size (Burton, 2001). A key environmental factor that causes regional population fluctuations is temperature. It is well known temperature has a critical role in growth rate, therefore causing regional differences in recruitment rates that are difficult to quantify. Variations in lobster population densities coupled with anthropogenic stresses, such as fishery pressure, have resulted in population collapses throughout their range.
A notable example is a major collapse in the H. gammarus populations in Norway. Prior to the 1960s annual catches were recorded in a range of 600 to 1000 tons (Prodöhl et al., 2006), however during the subsequent decades the fishery collapsed. To this day the population has yet to fully recover, evidenced by annual catches in the last decade not exceeding 62 tons (FAO, 2012). Major efforts are underway in Norway to repopulate fishery-depleted stocks, with various local successes (Agnalt et al., 1999; Van Der Meeren, 2005).
Currently the principle landings of H. gammarus occur in the United Kingdom with landings reported in 2010 at 2739 tons (FAO, 2012). The marine management stated that lobsters exacted the highest average price of all species caught by a UK fleet in 2010 at £9.78 per kilogram (MMO, 2011), giving the UK landings a value of just under £26.8 million for 2010. As one of the most valuable crustaceans in the UK, the lobster fishery is of major economic importance to coastal communities through provision of livelihoods, as well as to the UK export market.
Although the current UK lobster fishing industry is not in a state of crisis, with landings increasing over the last five years (FAO, 2012), localised drops in stocks occurred widely around the British Isles in the 1980s. These reduced landings, despite increased fishing efforts, combined with the collapse of lobster fisheries within the Mediterranean and Scandinavian seas denote the fragility of lobster fisheries. Thus, encouraging the UK fisheries agencies to implement various strategies and comprehensive management of the lobster stocks in British waters to maintain, and preserve, the fishery into the future. This includes regulations restricting landings in certain areas (Marine protected areas), of berried (egg carrying) females, in size (current EU legislation of 87mm carapace length) (DEFRA, 2013), and also to implement stock enhancement programmes and V-notch schemes (Burton, 2001).
Stock enhancement programmes involve rearing lobsters using aquaculture. The use of aquaculture to cultivate lobsters has been used since the 1850s (Bannister and Addison, 1998). This has occurred in three forms: complete lobster rearing, from birth to a size to sell; stock enhancement, raising the lobster to a juvenile size then released; and product enhancement, wild caught lobsters are maintained to increase quality and size. The former has not been economically viable due to the high production cost arising from space requirements, feed, and maintenance (Prodöhl et. al, 2006). Therefore lobster aquaculture has been focused on stock enhancement projects, known as hatcheries, which have been gaining considerable momentum, through intensive research, over the last fifteen years as a way to sustain lobster populations (Prodöhl, et al., 2006).
Concerns surrounded whether the hatchery reared juveniles survived in the wild in order to impact fishery stocks. In 1982 the use of micro tagging allowed for quantitative evaluation of released lobsters. Various studies conclusively determined that released lobsters survive to be recaptured by commercial fisheries at a marketable size, usually around five to ten years after release (Bannister and Addison, 1998; Burton, 2001). They were also adding to the natural recruitment as egg-bearing females were recaptured. (Van Der Meeren, 2005). More recently genetic tagging has enabled monitoring of recaptured cultivated lobsters (Prodöhl et al. 2006).
Hatcheries are showing increases in lobster populations, however there are concerns about the fitness of cultivated lobsters compared to their wild counterparts. An immediate deviation of cultured lobsters in the nineties was claw morphology. About 70% of lobsters cultivated had two scissor claws (Van Der Meeren, 2000) due to the lack of substratum, which is vital for the growth of the crusher claw. By incorporating substratum, such as shells, into their boxes, Van Der Meeren’s (2000) results showed only 30% failed to develop a crusher claw. An essential feature for competing in the wild over habitats and partners. It is important cultivated lobsters are as similar to wild lobsters to ensure they have the best chance of survival. Research continues into their differences and possible disruptions to the ecosystem that may result from releasing cultivated lobsters.
In conclusion, the loss of the economic commodity of lobster populations, such as in Norway, has been a critical incentive for developing sustainable strategies. Hatcheries are proving effective at enhancing lobster populations, but no one method is a panacea for ensuring lobster stocks, particularly with so many unknown ecological and biological factors. In my view, it is through collaborative efforts between government, fisheries, consumer demand for sustainable seafood, and continuous research, into the biology and ecology of Homarus gammarus, that will ensure the future of this historical and important fishery.
Agnalt, A.L., van der Meeren, G.I., Jørstad, K.E., Næss, H., Farestveit, E., Nøstvold, E., Svåsand, T. Korsøen, E. & Ydstebø, L. (1999) Stock enhancement of European lobster (Homarus gammarus); A large scale experiment off south-western Norway (Kvitsøy). In Stock Enhancement and Sea Ranching (Howell, B., Moksness, E., & Svåsand, T. eds.) pp. 401-419. Fishing News Books, Blackwell Science Oxford, UK.
Bannister, R. C. A., Addison, J. T. (1998) Enhancing Lobster Stocks: A Review of Recent European Methods, Results, and Future Prospects. Bulletin of Marine Science, 62, (2), 369-387.
Burton, C.A. (2001) The role of lobster (Homuras s.p.p) hatcheries in ranching, restoration and remediation programmes. Hydrobiologia, 465, (1-3), 45-48.
DEFRA (Department for Environment, Food and Rural Affairs) (2013) Minimum fish landing sizes. Available at: https://www.gov.uk/government/publications/minimum-fish-landing-sizes (accessed on 17/10/13)
FAO (Food and agriculture Organisation) (2012) FAO Yearbook (2010). Available at: ftp://ftp.fao.org/FI/CDrom/CD_yearbook_2010/navigation/index_intro_e.htm (accessed on 17/10/13)
MMO (Marine Management Organisation) (2011) The UK Fishing Industry in 2010. National Statistics Publication: London. Available at: http://www.marinemanagement.org.uk/fisheries/statistics/documents/ukseafish/2010/landings.pdf (accessed on 16/10/13)
Phillips, B.F. (2006) Lobsters: biology management, aquaculture and fisheries. Blackwell publishers, Australia
Prodöhl, P.A., Jørstad, K.E., Triantafyllidis, A., Katsares, V., Triantaphyllidis, C. (2006) European lobster – Homarus gammarus. GenImpact report. Available at: http://www.imr.no (accessed on 18/10/13)
Van Der Meeren, G.I. (2005) Potential of ecological studies to improve survival of cultivated and released European lobsters, Homarus gammarus. New Zealand Journal of Marine and Freshwater Research, 39, (2), 399-424.
Van Der Meeren, G.I. (2000) A comparison of claw morphology and dominance between wild and cultivated male European lobster. Aquaculture International, 8, (1), 77-94.
Fig1. http://www.imr.no/temasider/skalldyr/hummer/europeisk_hummer/en (accessed on 19/10/12)
Fig2. www.marlin.ac.uk (accessed on 19/10/12)