Variable population responses by large decapod crustaceans to the establishment of a temperate marine no-take zone

Abstract

In 2003, an area adjacent to Lundy Island was designated as the United Kingdom’s first no-take zone (NTZ) for nature conservation. The only significant fishery at Lundy was for lobster ( Homarus gammarus L.) and various crabs. The Lundy NTZ provided an opportunity to test hypotheses about the recovery of crustacean populations from fishing. Using an experimental potting program, we simultaneously compared changes in the crustacean populations within the NTZ with those in proximal control (Near Control) locations and two distant control (Far Control) locations. Comparisons were replicated over 4 years, and the results analysed using asymmetrical analysis of variance. There was evidence of a rapid, large increase in the abundance and sizes of legal-sized lobsters within the NTZ, and evidence of spillover of sublegal lobsters from the NTZ to adjacent areas. The NTZ also appeared to cause a small, but significant increase in the size of brown crab ( Cancer pagurus L.) and a decrease in the abundance of velvet crabs ( Necora puber L.) (the latter potentially owing to predation and (or) competition from lobsters). Unlike many previous studies, these results are unambiguous, owing to a robust asymmetrical experimental design. We suggest that regulatory and conservation agencies use this approach, which we have demonstrated to be relatively straightforward, whenever the NTZ requiring evaluation cannot be replicated.