Long-term changes in the distribution of the offshore northern shrimp (Pandalus borealis) in Icelandic waters

The aim of this study was to analyse long-term changes in the distribution of the offshore shrimp stock in Icelandic waters from 1988–2013 and to analyse whether recent warming had impacts on or shaped the distribution. The northern shrimp (Pandalus borealis) is distributed throughout the colder parts of the North Atlantic and Pacific Oceans and is found both inshore and offshore in Icelandic waters. The offshore population is in the deep waters north and east of Iceland, at depths of 200 m or more. In recent years, surface temperature on Icelandic fishing grounds has increased by 1 to 2°C and since 1996, temperature north of Iceland has been relatively high. Cod abundance on the shrimp grounds also showed a gradual increase in the study period, and at the same time, shrimp abundance in offshore waters declined, and reached a historically low level in 2004. In this study, the centre of gravity of the shrimp distribution was estimated for each year and its displacement examined in terms of main influencing factors which were the offshore shrimp catch and the cod biomass index from the annual offshore shrimp surveys. In addition, factors influencing the shrimp abundance were examined and the increasing sea surface temperature was found to be the main negative influence. The results therefore indicate that besides ocean temperature, both predation and fishing effort may have influenced the distribution and/or abundance of the northern shrimp off Iceland

Species of flabellifera (Crustacea; Isopoda) and their distribution in Icelandic waters

The Flabellifera (Crustacea; Isopoda) holds over 3000 described species and is the second largest isopod suborder, containing 18 families. Flabelliferans occur both in marine environment as well as in fresh water habitats, at all depths and latitudes of the world ocean. The Iceland-Faeroe Ridge is a part of the Greenland-Scotland Ridge and separates the Nordic Seas and the North Atlantic. The Greenland-Iceland-Faeroe (GIF) Ridge is relatively shallow and separates depths of more than 2000 meters on both sides and is a natural boundary between relatively warm Northeast Atlantic water and cold subarctic water masses. Iceland is located centrally on the GIF Ridge and the regions around Iceland hold a diversity of water masses, ranging in both temperature and saline concentration. The distribution of isopods (Crustacea, order Isopoda; suborder Flabellifera Sars 1882; families Aegidae Leach, 1815 and Cirolanidae Dana, 1852) were examined in Icelandic waters, based on analysis of 427 specimens collected between 1991-2004 on the GIF Ridge at 95 stations. The distributional pattern of the Flabelliferans in Icelandic waters was investigated and species assigned to water masses. Both families were species poor in the area, in total occurring with only 7 species in 4 genera. Species were found at temperatures ranging from 2.70-7.84°C and at depths from 140-2369 meters. Most species were restricted to warmer water

Feasibility of using growth band counts in age determination of four crustacean species in the northern atlantic

The age information of commercially important species is crucial in fisheries management. Age of various fish and molluscan species has routinely been determined by counting annual growth bands deposited within the hard structures. In crustaceans such structures were previously believed to be lost and replaced due to molting. However, a technique was recently developed to use growth bands deposited in hard structure retained through molting as an age indicator. In the present study, the applicability of the novel technique is investigated for four crustacean species collected from Northern Atlantic for the first time: European lobster, Homarus gammarus (Linnaeus, 1758); Norway lobster, Nephrops norvegieus (Linnaeus, 1758); Atlantic rock crab, Cancer irroratus Say, 1817; and northern shrimp, Pandalus borealis (Kroyer, 1838). The gastric mill ossicles in the first three species were processed to show the growth bands while the eyestalk was used in the shrimp species. Four growth bands were visible in European lobster hatched in a Norwegian hatchery and maintained alive for four years before prior processing. Band counts in the other three species were identical to size-at-age interpretation determined from length-frequency analysis. Validation of the periodicity of annual deposition of growth bands is essential before applying the technique on a wider scale

Feasibility of using growth band counts in age determination of four crustacean species in the northern atlantic

The age information of commercially important species is crucial in fisheries management. Age of various fish and molluscan species has routinely been determined by counting annual growth bands deposited within the hard structures. In crustaceans such structures were previously believed to be lost and replaced due to molting. However, a technique was recently developed to use growth bands deposited in hard structure retained through molting as an age indicator. In the present study, the applicability of the novel technique is investigated for four crustacean species collected from Northern Atlantic for the first time: European lobster, Homarus gammarus (Linnaeus, 1758); Norway lobster, Nephrops norvegieus (Linnaeus, 1758); Atlantic rock crab, Cancer irroratus Say, 1817; and northern shrimp, Pandalus borealis (Kroyer, 1838). The gastric mill ossicles in the first three species were processed to show the growth bands while the eyestalk was used in the shrimp species. Four growth bands were visible in European lobster hatched in a Norwegian hatchery and maintained alive for four years before prior processing. Band counts in the other three species were identical to size-at-age interpretation determined from length-frequency analysis. Validation of the periodicity of annual deposition of growth bands is essential before applying the technique on a wider scale