Population Structure of Greenland Halibut (Reinhardtius hippoglossoides) in the Northeast Arctic, 1992-2000

Abstract

The variation in population structure of Greenland halibut (Reinhardtius hippoglossoides Walbaum) in the Northeast Arctic is analysed using data from three different surveys using trawl, longline and gillnet gears, in the slope area of the western Barents Sea in the period 19922000. The design of the longline and gillnet survey had limitations in that they were set to simulate the commercial fisheries, but the vessels were forced to cover the most important part of the slope area. Greenland halibut was the dominant species both in numbers and weight and was usually caught in the range of 515 years old, but the catch was dominated by ages 612. The data showed differences in sex composition and age composition both by area and by depth, and catches from trawl showed the most evident pattern. Greenland halibut caught by gillnet were larger and older than fish caught by trawl and the results from longline were in between. In most of the age groups, males were significantly smaller than females and this general trend was shown for all gears. Males also dominated the younger age groups in all gears and Greenland halibut older than 10 years were virtually all females. Fish from the earliest cohorts in the years investigated were generally smaller than fish from later ones.

Modelling the advection and diffusion of eggs and larvae of Greenland halibut (Reinhardtius hippoglossoides) in the north‐east Arctic

“…A new survey has been developed to cover the waters north and east of Spitzbergen targeting 1–3‐yr‐old Greenland halibut. Together with Russian survey observations, this survey has revealed nursery grounds in the area (Høines and Smirnov, 2002), corresponding to the model results.…”

“…Recent field observations (A. Stene, unpublished data) indicate that spawning is most likely to occur in the northern area, as defined in the model. The modelled drift pattern from a northern spawning location corresponds to recent field observations of juvenile Greenland halibut (age 1–3) to the north and east of Spitzbergen (Høines and Smirnov, 2002).…”

“…This distribution shift corresponded to temperature changes and may have resulted in the survey indices of these year classes being severely underestimated due to a higher proportion being distributed outside the surveyed area. A new survey series from 1996 onwards, covering areas not previously surveyed by regular surveys, has revealed nursery grounds of 1–4‐yr‐old Greenland halibut in the waters north and east of Spitzbergen (Høines and Smirnov, 2002) and previous Russian investigations have found juveniles in the waters around Franz Josef Land (Borkin, 1983). Albert and Høines (2003) showed that the displacement of juveniles, described above, persisted up to age 7, and that this was an extraordinary situation, co‐occurring with extreme levels of the 137 yr long time series of the Index of the North Atlantic Oscillation (NAO).…”

Growth analysis and age validation of a deepwater Arctic fish, the Greenland halibut (Reinhardtius hippoglossoides)

“…Given that previous studies of Greenland halibut have been based on ageing methods that are now known to underestimate true age and growth rate in the Arctic population (Bowering and Nedreaas 2001;Høines and Korsbrekke 2003;Morgan et al 2003), there may be serious implications for stock assessments of the species. Ageing error propagates through estimates of age at maturity, lifespan, natural mortality rate, population size, and other vital rates and thus has a pervasive effect on the understanding of the population dynamics (Lai and Gunderson 1987;Tyler et al 1989;Bradford 1991).…”

Different maturity scales affect estimations of fecundity, TEP and spawning stock size of Greenland halibut,Reinhardtius hippoglossoides(Walbaum, 1792)

“…At the spawning grounds on the continental slope, the NEA stock inhabits depths that are between approximately 400 and 1500 m with water temperatures between -1 and 4°C (Bowering & Nedreaas 2000;Albert et al 2001b). Yearly landings have increased from 3000 t to 80,000 t with the introduction of international trawlers in the mid-1960s (Høines & Korsbrekke 2003), but decreased again to a level of 20,000 t during the early 1980s. Strong regulations, due to a decrease in the spawning stock biomass, were introduced in the 1990s, including a fishing ban from 1992 to 2009 north of 71°30ʹN, with the exception of research quotas and Norwegian artisanal fishery (Gundersen et al 2000;ICES 2013).…”