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Direct age determination of crustaceans has remained a long-standing challenge because all calcified structures are shed with each molt. Cuticle bands in the ossicles of the gastric mill have shown promise as age indicators. We validated the one-to-one relationship between known age and number of cuticle bands for 15 hatchery-raised juvenile American lobsters (Homarus americanus). Additionally, we applied this method to 308 lobsters from three contrasting thermal regimes in New England, USA. Band counts matched our expectations of differences in age-at-size across this thermal gradient; lobsters at harvestable size in southern New England were estimated to be 5.5 ([+ or -]1.5) years old compared with 7.5 ([+ or -] 1.6) years in the Gulf of Maine. We found 81% of our band count estimates of age fell within 2 years of independent, regionally specified growth model estimates of age-at-size for lobster. Notwithstanding remaining uncertainties regarding the mechanism of band formation, our findings indicate the method may provide an independent and direct means to determine the age of individual American lobsters, which will improve estimates of essential life history parameters. La determination directe de l'age de crustaces est un defi de longue date etant donne que toutes les structures calcifiees sont perdues a chaque mue. Des bandes cuticulaires dans les ossicules du moulin gastrique se sont averees prometteuses comme indicateurs de l'age. Nous avons valide la relation directe entre l'age connu et le nombre de bandes cuticulaires pour 15 homards (Homarus americanus) juveniles eleves en ecloseries. Nous avons de plus applique cette methode a 308 homards provenant de trois regimes thermiques distincts en Nouvelle-Angleterre (Etats-Unis). Le nombre de bandes concorde avec nos attentes quant aux differences d'age selon la taille le long de ce gradient thermique; l'age estime des homards ayant atteint la taille reglementaire dans le sud de la Nouvelle-Angleterre etait de 5,5 ans ([+ or -]1,5), comparativement a 7,5 ans ([+ or -]1,6) dans le golfe du Maine. Nous avons constate que 81% de nos estimations de l'age basees sur le nombre de bandes tombaient dans une fourchette de 2 ans autour des ages selon la taille estimes par des modeles de croissance en fonction de la region pour les homards. Bien que des incertitudes persistent concernant le mecanisme de formation des bandes, nos constatations indiquent que cette methode pourrait constituer un moyen independant et direct de determination de l'age de homards individuels, ce qui ameliorera les estimations de parametres cles de leur cycle biologique., Introduction Age determination is an essential tool in studies of the ecology and management of fish and invertebrate populations. The calcified skeletons of bony fishes, mollusks, and corals accumulate annual [...]

The study examined the response of Arctic benthic communities to changes in food supplies in the Arctic region. Results revealed that the communities are versatile and capable of changing methods to meet their food requirements.

Many marine species are known to change their distribution in response to changing climatic conditions. One such example is the blue mussel Mytilus spp., spreading northward coincident with an increase in ocean temperatures. On Svalbard, the first living specimens of Mytilus spp. were discovered in 2004. Here we present an analysis of the current distribution of Mytilus spp. on Svalbard, with a focus on the west coast of Spitsbergen where strong Atlantification has been documented over the last few decades. We conducted diver-based surveys to develop a distributional map and to compare the current distribution with that of the Holocene. Furthermore, we investigate the recent history of recruitment of mussels on Svalbard to help identify invasion pathways. Our results show that blue mussels have been present on the archipelago at least since 2000 and are widespread along the west coast today. We also present evidence of local reproduction in one of the sites explored. [ABSTRACT FROM AUTHOR]

Zooarchaeological faunal remains are commonly examined to investigate harvesting behavior. We determined limpet (Patella vulgata) shell size and shape, and estimated shell age from several middens at the Late Norse Sandwick South Site, Unst, Shetland, UK, whose strata represent distinct occupational phases (Phase 1: AD 1100-1200, Phase 2: AD 1200-1250, Phase 3: AD 1250-1350). Our goal was to determine if the many limpets found there could provide insight into Norse harvesting behavior. Shell length, conicity, and modeled age all declined between Phases 1 and 2, suggesting intensive, size-selective harvesting of limpets and a shift to harvesting lower in the intertidal zone between phases. Length and conicity varied in Phases 2 and 3 and no major changes seem to have occurred over these periods, indicating that harvesting maintained the limpet population at an impacted level throughout the later phases. The conicity decline between Phases 1 and 2 may also have been caused by increased storminess that accompanied the onset of the Little Ice Age. The mean length of modern limpet populations near the Norse site did not differ from the archaeological phases, but did vary among collection years. Limpets were 26% larger in 2015 than in 2012 and 2013, indicating that large interannual variations in population structure can occur over short time periods. Potentially the result of extreme storms removing small limpets, this result raises the possibility that size and conicity changes during the Sandwick South Site occupation, as well as in other early populations, could also be the result of environmental factors rather than human harvesting alone. We feel, however, that the most parsimonious explanation for the patterns we document is human harvesting. [ABSTRACT FROM AUTHOR]