Fecundity and size at maturity of the European lobster Homarus gammarus (Crustacea: Decapoda) was estimated in four coastal regions of Ireland. Egg size increased with carapace length (CL) (egg size=0·9939×ln (CL)−3·0809). The size–fecundity relationship for all coasts combined was (fecundity=0·0044×CL3·1554).  Physiological maturity was assessed using ovary colour, ovary factor, ova size, abdomen width/CL ratio, cement gland activity and moult status as criteria. Size at 50% maturity varied from 92·5 to 96  mm depending on region. The size–maturity relationship for all coasts combined was (Maturity= 1/(1+exp(14·595−0·15598×CL))). Over 60% of lobsters in the commercial landings were under the size at 50% maturity.  Relative reproductive potential (RRP) of different size-classes was calculated from the size–fecundity and size–maturity models and the numbers by length in the landings. The modal RRP size-class was 98–100 mm. The commercial landings were dominated by the 86–92  mm size-classes.

No abstract

Infection of Cancer pagurus by a parasitic dinoflagellate of the genus Hematodinium is described for the first time in Ireland. An industry-based monitoring programme was established to determine seasonality of infection intensity and prevalence in the country's 3 largest brown crab fisheries in the southwest, north and southeast. The parasite was present in all areas for the majority of sampling periods, with highest prevalences recorded in pre-recruit animals of both sexes. Microscopic examination of haemolymph revealed trophont, plasmodial and dinospore stages of the parasite. Overall prevalence in males (16%) was higher than in females (9%). Prevalence of Hematodinium sp. infection ranged from 0 to 51%, but a distinct seasonal trend was not apparent. Infection intensity was seasonal with significantly higher peaks occurring in late autumn/early winter months than in other quarters, corresponding to industry reports of moribund and dead pink-shelled crabs in commercial catches. We postulate that seawater temperature or a temperature-linked process is a key factor in triggering the final stages of infection, as significant autumn peaks were followed by a reduction in infection intensity as temperature decreased in the late winter/early spring months with no increase in intensity again until the following autumn. We propose that infection intensity, rather than prevalence, provides a more appropriate indication of the period when there is greatest potential for biological and economic impacts; the parameter's application as a fisheries management tool is discussed.

Sub-tidal populations of decapod crustaceans from 5 distinct benthc habitats were sampled at the end of the main settlement season. Divers, using SCUBA equipment, estimated substrate characteristics and complexity, removed sediment samples, and collected quantitative samples of the resident communities using suction sampling at each of the sites. Adult and young-of-the-year (YOY) components of the decapod assemblages were identified. Univariate and multivariate statistical techniques were used to detect between-site differences in the community structure and community statistics of each component. Although YOY individuals were detected at each of the sites, community structure and statistics for the YOY component varied significantly among sites. Between-site differences in the adult component of the community were also identified. Between-site differences in the YOY assemblages varied from that of the adult component, indicating that post-settlement processes, such as predation and migration, play an important role in shaping the community. Variation in physical complexity and other habitat characteristics appeared to contribute to the significant differences in the YOY and adult assemblages. Due to the close proximity of the sample sites to one another, it seems unlikely that restrictions or spatial and temporal variations in larval supply resulted in the between-site differences observed. Substrate choice at settlement would appear to vary between species, with most species rejecting more marginal areas that offer little shelter to either post-larvae or individuals at later stages of development.

Robinson, M. 2008. Minimum landing size for Northeast Atlantic stocks of deep-water red crab, Chaceon affinis (Milne Edwards and Bouvier, 1894). – ICES Journal of Marine Science, 65: 148–154. Annual landings of the deep-water red crab (Chaceon affinis) in the NE Atlantic have fluctuated around 1000 t for much of the past decade, but they dropped significantly in 2006. No EU or National Member State legislation governs the harvest of the species, and because of the on-board processing, it is difficult to set a single minimum landing size (MLS) based on carapace width (CW) alone. As the claws are detached during processing and represent the most valuable component of the catch, a supplementary MLS based on claw length (CL) for onshore inspection and enforcement would seem appropriate. Physiological size-at-maturity and morphometric claw data were used to derive primary (CW) and secondary (CL) MLS. All males and females are mature at 110 and 125 mm CW, respectively, and 50% of females are mature at 109 mm CW. Because of a lack of information relating to the biology, distribution, and fishing mortality of the species, and a doubt as to real landing statistics, a conservative MLS of 120 mm CW and 72 mm CL is suggested, representing the first use of commercial fisheries data to suggest MLS for this otherwise unregulated fishery.