Stock of deep-sea redfish in the Barents Sea (Sebastes mentella)
The stock of deep-sea redfish is on the upswing. While recruitment to the stock was weak from 1996 to 2004, it has since picked up.
What is being monitored?
Cite these dataInstitute of Marine Research (2020). Stock of deep-sea redfish in the Barents Sea. Environmental monitoring of Svalbard and Jan Mayen (MOSJ). URL: http://www.mosj.no/en/fauna/marine/deep-sea-redfish.html
|Mature stock||106 kg||Institute of Marine Research||227||286||362||418||346||426||484||547||637||602||674||745||753||807||796||933||892||914||869||856||854||811||810||799||796||797|
|Total stock||106 kg||Institute of Marine Research||523||566||621||683||745||808||865||911||951||985||999||1017||1030||1037||1039||1018||1011||1018||1034||1056||1085||1130||1182||1230||1261||1279|
|Recruits, 2-year olds||106||Institute of Marine Research||413||276||212||190||155||121||63||48||38||29||36||39||50||97||221||371||380||356||513||468||431||200||130||181||174||166|
The method for estimating population size for beaked redfish is based on two procedures: first a qualitative (non-analytical) assessment is made of trends in biomass/age range based on expedition and harvesting data. This uses expedition data from winter and summer expeditions in the Barents Sea and along Eggakanten. The second method is an analytical calculation that uses the GADGET model, which structures age and size. This model uses the same data sets but estimates biomass for given ages and fish mortality by modelling biological processes (weight, development) that are adapted to actual observations.
An improved model for estimating population size has begun to be formally used for the first time after being approved by the ICES in 2012. A lack of coverage of the beaked redfish’s geographical spread and weaknesses in the expedition programme somewhat reduce the quality of the data used in the model.
Two major issues for monitoring the stock size deep-sea redfish are:
- The large geographical extent of the population
- The mixed demersal-pelagic behaviour
The Institute of Marine Research observes that adults can travel out into the Atlantic waters of the Norwegian Sea in summer, but this area is not routinely monitored, which leaves some of the stock unobserved. This part might be quite substantial (half a million tonnes or more). In the Barents Sea, survey abundance estimates derive from demersal trawling, but hydro-acoustic observations suggest that the demersal layer that is sampled only contains 20% of the biomass. Thus, the abundance of redfish is underestimated, but it is not known by how much.
Reference level and action level
The reference level has not been determined, but the Institute of Marine Research recommends taking a cautionary approach to the spawning population.
Status and trend
According to the International Council for the Exploration of the Sea (ICES), the beaked redfish population has recovered to a sustainable reproductive level. Recruitment was weak from 1996 until 2004, but has been clearly stronger since then.
In early 2007, the North East Atlantic Fisheries Commission (NEAFC) determined an annual quota for the fishery in international waters. The quota set for 2007 was 15,500 tonnes. The quota was then gradually reduced until 2014, when it was set at 24,000 tonnes.
In the re-establishment phase for the beaked redfish population, which lasted until 2014, it was only permitted to catch beaked redfish as an unavoidable bycatch in Norwegian sea areas. With effect from 2014 it has once again been possible to deliberately fish for this species within defined areas. In 2014 the ICES decided that the commercial fishery could take 30,000 tonnes in 2015, 2016 and 2017, and 32,658 tonnes in 2018 (including bycatch and discard), but that the existing measures to protect fry and young fish should be continued.
In 2014, catches outside the Norwegian economic zone amounted to 4,000 tonnes, while catches within the zone were approximately 14,700 tonnes. In 2015 about 4,700 tonnes were fished outside the Norwegian economic zone and about 21,000 tonnes within it. Corresponding figures for 2016 show a marked increase, with catches of 7,000 tonnes outside the Norwegian economic zone and around 28,000 tonnes within it. In 2017 the catches outside the Norwegian economic was around 6,000 tonnes, and within the Norewian economic zone barely 25,000 tonnes. The total catch was higher than it was in 2015, but slightly less than in 2016. The total catch outside and inside the Norwegian economic zone was therefore 31,000 tonnes, which is above the recommended total permitted catch of 30,000 tonnes.
The beaked redfish population is affected by both natural conditions, such as sea temperature and the occurrence of fish that eat beaked redfish, and human activity, such as fishing.
Cod and halibut eat small beaked redfish. Larvae and small beaked redfish fry are also found in the stomachs of herring.
The present spawning population consists almost entirely of age groups that hatched in the late 1980s. This is due to both the weak recruitment between 1996 and 2004 and the fact that the beaked redfish only becomes sexually mature at 12 years. The greater numbers of fish that hatched after 2004 have now (in 2017) begun to be included in the spawning population.
The beaked redfish population is developing well, with an increase in both recruitment and the sexually mature population. Even so, the spawning population is expected to decrease for some years. This is due to both the weak recruitment between 1996 and 2004 and the fact that the beaked redfish often does not become sexually mature until 12 years.
An unknown quantity of beaked redfish is also being taken as a bycatch in other fisheries, such as silversmelt and prawn. The prawn fishery is therefore being monitored and areas with too high a proportion of redfish fry (maximum 3 fry per 10 kg of prawns) are closed for prawn fishing.
About the monitoring
The deep-sea redfish is red-listed as "Vulnerable" and has suffered from severe overfishing. It has a long life-span and sexually matures late. Monitoring the development of the stock size is essential to ensuring reliable, sound knowledge that enables sustainable management of its fisheries.
Places and areas
Relations to other monitoring
- Monitoring programme
- International environmental agreements
- Voluntary international cooperation
- Related monitoring