Enhancing Lobster Stocks: A Review of Recent European Methods, Results, and Future Prospects

This paper reviews the status of stock-enhancement studies on the clawed lobster, particularly recent experiments on Homarus gammarus in European waters. Previous attempts from the 1850s onwards with both H. gammarus and H. americanus showed little success, but since 1980, lobsters reared in the hatchery to juvenile stage XII have been released in substantial numbers at a range of sites in the United Kingdom, France, Norway, and Ireland. Releases on the order of thousands have yielded recaptures on the order of hundreds. This new success arises because juveniles were microwire tagged, released directly by divers onto known lobster habitat, and subsequently recaptured by dedicated field sampling and monitoring of commercial lobster landings. Hatchery lobsters showed little dispersal, they required 4 to 5 yrs to reach legal size, and some ovigerous females were recaptured. Field sampling tentatively suggests survival to legal size as high as 50%, but the overall recapture rate in the fishery was below 5%. Recaptures seem marginally higher in areas of low lobster density, but the experiments were not designed to answer ecological questions, and they cannot be used to make substantive predictions about how stocking density and the local abundance of natural stock will affect survival and recapture rate. Before the biological and economic benefits of enhancement programs can be assessed, experimental testing is needed of whether hatchery-reared juveniles supplement or replace naturally settled lobsters. At current levels of recruitment, enhancement programs seem unlikely to be worthwhile, particularly compared with the implementation of restrictive management measures, but enhancement programs can be justified where there is some clear evidence of recruitment failure, as in Norway. At present lobster prices, the current recapture rate is well below that required to cover the present cost of constructing and running a moderate-sized hatchery from scratch. This economic appraisal is discouraging from a “put-and-take” ranching perspective, but a program aimed at enhancing breeding stock and independently financed from associated tourism or sea-life-center activity is still potentially viable.