Migration patterns of Greenland halibut in the North Atlantic revealed by a compiled mark-recapture dataset

Marine fisheries are often allocated to stocks that reflect pragmatic considerations and may not represent the species’ spatial population structure, increasing the risk of mismanagement and unsustainable harvesting. Here we compile mark–recapture data collected across the North Atlantic to gain insight into the spatial population structure of Greenland halibut (Reinhardtius hippoglossoides), an issue that has been unresolved for decades. The dataset contains 168130 fish tagged from 1952 to 2021, with 5466 (3.3%) recaptured individuals. Our results indicate that fish tagged at <50 cm body length migrate at higher rates, suggesting that mark–recapture studies on adult individuals underestimate population-level migration rates. We find evidence for migrations across management units in the North Atlantic indicating two regional offshore populations: one in the Northeast Atlantic, where the West Nordic and Northeast Arctic stocks, currently managed separately, likely belong to a single population that spans from the Kara Sea to Southeast Greenland; and one in the Northwest Atlantic where migration was observed between the Newfoundland and Labrador stock and the Northwest Arctic stock in Davis Strait and Baffin Bay. Our findings indicate complex population structure with implications for international and domestic fisheries management of this long-lived species.publishedVersio

Anglerfish Lophius piscatorius L. in Faroese waters. Life history, ecological importance and stock status

Anglerfish Lophius piscatorius has during the last two decades become a highly exploited resource and is now one of the five most economically important demersal fish species in the Faroese fishery. Despite this, there is at present little information available on the population status of anglerfish in Faroese waters. The main aim of this study is to increase the biological knowledge of anglerfish and to perform an assessment of the stock in order to evaluate the sustainability of the anglerfish fishery and to investigate trophic interactions between anglerfish and other commercially important demersal fish species. Anglerfish illicia, the first fin ray, were used for age reading. The age determinations were validated and concluded to be useful in an age-based assessment because the growth rates were consistent with length frequency and mark-recapture analyses. Anglerfish have a very high growth rate during their first year of life, compared with the older ages. Males mature at a lower length and younger age than females. The L50 for males and females was 58 cm and 84 cm, respectively, corresponding to an age of around four years for males and seven years for females. Observations of spawning males and females, egg-ribbons and pelagic anglerfish larvae revealed that anglerfish have a prolonged spawning season, which peaks from February to April. In addition, observations showed that there are at least two local spawning areas, one southwest of the Faroe Plateau and one in the Faroe Bank area. Large anglerfish tagged with data storage tags and conventional tags showed a seasonal offshore-onshore migration. They migrated to shallow depths in summer to feed and to deeper waters in winter, presumably to spawn. Anglerfish performed vertical movements up into the water column, and were most active in these vertical movements during the winter time and during the nights, and light intensity seemed to trigger the migrations. Anglerfish distribution was temperature dependent, since anglerfish generally preferred temperatures warmer than 4ºC, usually between 6.5–11ºC. This may explain why anglerfish were distributed deeper west of the Faroe Bank area compared to the Faroe Plateau, which is surrounded by cold water deeper than approximately 500 m. Anglerfish in Faroese waters preyed on a variety of food items. They were generally eating fish and the most important prey species in terms of numbers were Norway pout and blue whiting, whereas cod and haddock contributed most in weight. Annual consumption by anglerfish on commercially important demersal species, such as cod, haddock and saithe, was estimated to correspond to 33, 19 and 2% of the landings and to 75, 20 and 2% of biomass losses due to natural mortality, respectively. Even with this high cod consumption by anglerfish, cod cannibalism and fishing mortality still have greater impact on the cod stock dynamics than predation by anglerfish. The annual biomass loss of anglerfish due to cannibalism was estimated to nearly 15% of the annual loss due to natural mortality. Anglerfish in Faroese waters may be regarded as a separate stock because all life stages are found in the area, local spawning area, seasonal offshore-onshore migration on the Faroe Plateau, together with insignificant emigration/immigration (< 5%). An age-based stock assessment of anglerfish in Faroese waters for the period 1999–2011 showed that the stock biomass ranged between 9000 and 19000 t with a peak in 2004–2005 and the fishing mortality for age 3–8 varied between 0.2 and 0.5 year-1. The yield per recruit curve indicated that the stock was slightly growth overfished. Decreasing the fishing mortality could potentially increase the yield per recruit by around 10% leading to a 50% higher equilibrium biomass of anglerfish. No clear stock-recruitment relationship was found. On the other hand, anglerfish year-class strength was correlated with environmental variables, such as sandeel abundance. Hence, the rather short time series of anglerfish year-class strength provides little or no evidence of recruitment overfishing. It is recommended that stock assessments should be performed on an annual basis, allowing managers to react timely when there are signs of overfishing or recruitment failure due to natural or fishery causes

Catch statistics and life history of shrimp, Pandalus borealis, in the Jan Mayen area

The Norwegian shrimp (Pandalus borealis) fisheries in the Jan Mayen area in the North East Atlantic started in 1974. The catches reached 2000 tons in 1985. Since 1986 the catches decreased, but lately they have increased again to 500 tons in 1994 and 1400 tons in 1995. Larger vessels ( > 2000 HP) were introduced in 1984. They caught more than 50% of the landings in the period from 1993 to 1995. The annual catch depends on stock biomass, availability according to ice coverage and circumstances in the shrimp fisheries off Greenland. The results of Norwegian shrimp surveys conducted in 1980, 1981, 1994 and 1995 are presented and discussed in relation to earlier studies, especially data from 1976 and 1979. The squared study area is defined by the coordinates 70°20' N, 7°30' W and 71 °15' N, 9°40' W. It covers the Jan Mayen Bank, south of the Jan Mayen island, and the Marøy Bank in the Northwest corner. Shrimp biomass is calculated for each 100 m depth interval for the six years, and show without exception the highest densities at the depth 200-299 m. The biomass index for the six years varies between 3000 and 6600 tons. The size of the shrimp increase with depth, thereby females dominate at depths greater than 300 m. The Jan Mayen shrimp is large compared to Barents Sea shrimp and can reach a carapace length of 38 mm. The large size at sex transformation (> 23 mm) and analysis of length frequency distributions indicate that the shrimp may be five to eight years when changing sex. The fish community composition is described and discussed for the years studied. Fish community composition is described for the years studied. Polar cod and capelin are the most abundant fish species in the study area. A high number of blue whiting was registered in 1979 but the number declined in 1980 and 1981. During the surveys in 1994 and 1995 no blue whiting was registered. The number of Greenland halibut has declined from the beginning of the 80-ties to the mid 90-ties

Horizontal and Vertical Migration of Anglerfish Lophius piscatorius in Relation to Hydrography in Faroese Waters

Adult anglerfish conduct annual migrations between spawning areas and feeding areas; for Faroese waters this migration has so far not been described. Therefore, anglerfish migration and distribution in Faroese waters was investigated by mark-recapture studies, including data storage tags, as well as data from scientific trawl surveys, commercial trawlers and gillnetters. The fish distribution was compared to hydrographical conditions such as sea surface- and bottom temperature. A clear seasonal offshore-onshore migration was observed. Anglerfish occupied shallower waters (<200 m) during summer and deeper waters, especially on the western side of the Faroe shelf, during winter. This seasonal movement was most evident for sexually mature fish longer than 70 cm indicating spawning in deep waters during winter. Further, during winter anglerfish experienced cold water, which indicated that they were distributed close to the main interface of cold water masses surrounding the shelf. The fish were mostly located in warm water (6.5–11°C) and seldom occurred in colder waters than 4°C. Anglerfish appeared generally inactive, only around 5% of the total data storage tag recordings showed more than 5 m vertical movement between two subsequent hourly recordings. This vertical activity varied seasonally by being higher during winter than summer and diurnally by being higher during night time than day time, indicating that sunrise and day length played an important role in vertical movements

Anglerfish (Lophius spp.) in nordic and european waters: status of current knowledge and ongoing research

Med norsk sammendrag

Anglerfish (Lophius spp) in Nordic waters

The demand for anglerfish for human consumption has increased in the last couple of decades because of the delicate consistency of its meat. Accordingly, the fishing pressure has increased considerably in all Nordic fishing regions. Relatively little has, however, hitherto been known about anglerfish biology and ecology. Assessment and management of Nordic anglerfish stocks is difficult to conduct due to the paucity of fisheries and biological data. Answers to questions regarding the spawning behaviour, migratory behaviour and juvenile drift, as well as more knowledge about growth, sexual maturation, diet and natural mortality, would thus form crucial contributions to present and future management of Nordic anglerfish stocks. This report presents a review of the status of current knowledge and research on the biology, ecology, fisheries and stock management of anglerfish in Nordic and European countries, including results and publications from a three-year Nordic cooperative anglerfish research project (2002-2004). Preliminary attempts were made at estimating current levels of fishing mortality in the Nordic regions, and the yield and spawning stock per anglerfish recruit. Recommendations on future research are also given