An individual based model (IBM) of the female brown crab Cancer pagurus population exploited off South Devon, UK is described. Size dependent movement rules are ascribed to individuals based on previous observations of predominantly westward migration down the English Channel. Two additional versions of the movement rules explored whether the empirically derived rule was necessary to model the temporal and spatial distribution of crabs. Local crab movement was dependent on substrate type and water depth. Females prefer a soft substrate in which they can bury when temperatures are low or they have eggs to incubate. Crabs have size dependent depth preferences with larger crabs preferring greater depths. Two recruitment functions are used which relate the number of incoming crabs to the sea surface temperature five years earlier. Model outputs were tested against 10 years of logbook data from three crab fishers and against data from a year-long sampling programme on eight of the vessels exploiting the area. The model reproduces the long-term pattern which is mostly temperature driven. Spatial variation in catch is captured effectively by the model with more crabs being caught in the east of the area than the west and more caught offshore than inshore. The significance of the results is discussed in relation to the crab life cycle, management of the fishery and the potential effects of increasing temperatures.

Brown crab contributes to small-scale fisheries in the Isle of Man and landings (495 t) were worth in excess of £0.5 million in 2012. The present study sought to fill evidence gaps needed to improve the scientific understanding of this fishery. Observer data were collected to examine the spatial and temporal variations in the size distribution and sex ratio of crabs around the Isle of Man. This study also aimed to evaluate the catch characteristics of brown crab using logbook data (2007–2012), observer data (2012–2013) and questionnaire survey data (2013). The sex ratio is highly variable in different areas across seasons and was perhaps indicative of migration patterns in relation to mating. This change was most notable with a strong increase in the proportion of females to the south and west of the Isle of Man in the autumn months. The depth and pot volume were important factors that influenced the catch per unit effort (CPUE). Future survey designs would need to ensure adequate spatial coverage of the east and west coast of the Isle of Man together with a seasonal sampling regime that captures the spatial change in the distribution and abundance of male and female crabs.

The behavioural responses of scavenging animals to mackerel (Scomber scombrus) baits were studied by short-term video photography in shallow water (16–18 m depth) at Lough Hyne, Ireland. Earliest arrivals (after seconds/minutes) at baits were small fish or swimming crabs (Liocarcinus depurator), followed by crawling portunid crabs. After tens of minutes, juvenile whelks 2–4 mm shell length (Nassarius reticulatus and/or Nassarius incrassatus) sometimes arrived to feed. They moved at a mean speed of 1.24 (SD 0.392) mm s−1. After tens of minutes or hours, single large scavengers arrived, consuming most of the bait; the most common of these were Cancer pagurus that fed in a wasteful fashion, generating large quantities of mackerel scraps. Cancer pagurus moved into view at a mean speed of 48.7 (SD 16.9) mm s−1(39 times the whelk speed). A single individual of C. pagurus (197 mm carapace width) arrived at a bait carrying 24 juvenile whelks on the dorsal surface of its carapace. No whelks were present on walking legs or chelipeds. The crab fed for 6.8 min and 3 whelks fell off before it departed. The nature of this crab/whelk association is discussed; on balance it appears that it is a previously unreported example of phoresy/phoresis. No whelks were observed being carried by other edible crabs or upon large numbers of scavenging portunid crabs.

The management of fisheries in European Union (EU) waters has generally been regulated through government institutions and agreed quota allocations. This top-down management approach may have contributed to the continued decline of targeted fish stocks by forcing fishers to compete for limited resources without engendering a sense of resource stewardship. In attempting to reverse this decline, scientists and managers should examine management systems that do not solely depend on top-down approaches, and the Inshore Potting Agreement (IPA) is an example. The IPA is a voluntary fishery management system designed and operated by inshore fishers of south Devon, England. The IPA was conceived to reduce conflict between static-gear (pot and net) and towed-gear (trawl and dredge) fishers, and is regarded as a successful fisheries management regime by fishers and managers because it has effectively allowed fishers from both sectors to operate profitably on traditional fishing grounds. Another study determined that the IPA has incidentally protected benthic habitat complexity. Fishers from the static-gear and towed-gear sectors were interviewed to determine the evolution and function of the IPA, and to establish the factors that ensure the high level of regulatory compliance amongst fishers from both sectors. Towed-gear fishers gave significantly different responses to the same questions asked of static-gear fishers, and were generally less satisfied with the existence of the IPA. Multivariate analyses of the interview data suggested that fishers who thought the IPA was a good system also thought the system provided pot protection, but had experienced inter-sector conflict. Fishers who thought the IPA provided no personal benefit also thought that static-gear fishers should be more restricted, and that towed-gear corridors or more seasonal-use areas should be established within the existing IPA area. However, fishers from both sectors agreed that the IPA has maintained traditional practices of the local fishing industry, and that the system has conserved target finfish and scallop species. A number of factors were identified as critical to the success of the IPA. These included the voluntary nature of the agreement, the limited number of organizations representing fishers and very high level of membership of those organizations, and the simplicity of the system. Regulatory compliance is enhanced through the ability of fishers' organizations to respond rapidly to inter-sector conflict issues.