Landings of European lobster (Homarus gammarus) and edible crab (Cancer pagurus) from 1615 to 2009, Helgoland, North Sea

From 2000 to 2005 about 5400 one-year-old hatchery-reared lobsters (Homarus gammarus) were tagged and released at the rocky island of Helgoland, North Sea. To date, 1-8% of the different release cohorts were recaptured in the field and 8-19% of these lobsters were recaptured from the semi-open area of the outer harbour. The recaptured lobsters indicated good development and growth conditions. The smallest berried females caught were 83 mm carapace length and 4 years old. The proportion of cultured lobsters to all measured lobsters captured around the island was 3-8% in the years 2007-2009. The population size of two cohorts was assessed using the Lincoln-Peterson method and the estimated survival rate averaged 30% and 40%. Minimum landing size of cultured lobsters was reached after 4-7 years. Cultured lobsters showed strong fidelity to their release sites, and thus remained around the island of Helgoland. A basis has been laid to enhance this endangered lobster population by means of a large scale restocking programme.2000年至2005年间，研究人员在北海黑尔戈兰（Helgoland）岩岛海域，对约5400尾人工繁育的1龄欧洲龙虾（Homarus gammarus）进行标记并放流。截至目前，不同放流群的野外回捕率为1%~8%，其中8%~19%的个体在外港半开放区域被捕获。回捕个体的发育与生长状态良好，本次研究捕获的最小抱卵雌虾头胸甲长度为83毫米，年龄为4龄。2007年至2009年间，在该岛周边捕获的所有经测量的龙虾中，人工繁育个体占比为3%~8%。研究采用林肯-彼得森（Lincoln-Peterson）法对两个放流群的种群规模进行评估，估算的平均存活率分别为30%和40%。人工繁育龙虾达到最低可捕规格所需时长为4~7年，其对放流位点具有极强的位点保真度，因此始终栖息于黑尔戈兰岛周边海域。本研究为通过大规模增殖放流计划恢复该濒危龙虾种群奠定了坚实基础。