Fishing mortality in the Barents Sea

Fishing Vessel outside Tromsø, Norway
Photo: Stein Ø. Nilsen / tromsofoto.net

The Barents Sea is an important area for the fisheries and large quantities of important fish like northeast arctic cod, northeast arctic haddock, deep-sea redfish, Greenland halibut and shrimps are caught. Capelin is fished when conditions allow for sustainable quota. Today, the Barents Sea stocks are sustainably managed.

What is being monitored?

Fishing mortality

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The figure shows the fishing mortality for cod, haddock and deep sea readfish in the Barents Sea. The situation is good for all stocks, as they for many years have been harvested sustainably.

Status and trend

Fishing mortality is a measure of the proportion of fish stocks that are fished. If fishing mortality is estimated to be less than the precautionary level (Fpa), we say that the stock is harvested sustainably. If it is higher than the precautionary level, but lower than the International Council (ICES) has defined as critical fish mortality level (Flim), there is a risk that the stock is not harvested sustainably. Then there is an increased chance that the spawning stock could drop below the precautionary level.

The figure below shows fishing mortality for cod, haddock and rosefish in the Barents Sea. The situation is good for all these stocks, as harvesting has been sustainable for many years.

Causal factors

The size of the fishing mortality is included in the assessments made when fishing quotas and harvest rules are determined. If a fish stock has poor development, smaller quotas are set. In some cases extended time and area limited bans are set on fishing.

Consequences

The state and development is satisfactory for most commercial fish stocks in the Barents Sea. The capelin stock is an exception, and has declined sharply from 2013 to 2016.The capelin fishing was stopped from 2016. Despite for an improvement in the contitions, it is still discouraged to harvest capelin, also in 2019.The capelin stock is still below the level where capelin fisheries are not expected to have an effect as reduced food availability for cod and other fish.

The capelin's short life span and the fact that it is a one-time-spawner makes the calculation method for fish mortality not suitable for this species. The stocks of cod and capelin are managed in context, taking account of the cod grazing on capelin and the capelin's importance as food for cod. Capelin fishing has also been stopped several times previously (1987-1990, 1994-1998, 2003-2007). Impact on capelin stocks from cod, herring and other species are believed to be bigger than from fishing.

An evaluation of alternative harvesting rules for cod, haddock and capelin was commissioned by the Norwegian-Russian Fisheries Commission in 2015, and was presented by the International Council for Exploration of the Sea (ICES) in March 2016. The Norwegian-Russian Fisheries Commission chose to continue with the existing harvesting rules for haddock and capelin. For cod, the rule was changed so that the fishing mortality now increases when the spawning stock is high, and maximum change in quota from year to year has increased from 10 percent to 20 percent.

About the monitoring

Terms

Blim  = Limit reference point for spawning stock biomass
Bpa   = Precautionary reference point for spawning stock biomass
Flim   = Limit reference point for fishing mortality
Fpa    = Precautionary reference point for fishing mortality
Fmp   = Fishing mortality reference point as defined in management plans
FMSY = Fishing mortality consistent with achieving maximum sustainable yield
F      = Instantaneous rate of fishing mortality
Z     = Total mortality
M     = Natural mortality

Evaluation

A spawning stock which is calculated to be at a level that most likely will give good recruitment has good reproductive ability (the spawning stock is above Bpa). Good recruitment presupposes that environmental factors which influence fry survival are favourable.

When the level of the spawning stock is calculated to be such that there is increasing likelihood of it giving reduced recruitment, the stock is at risk of having reduced reproductive ability (the spawning stock is below Bpa, but above Blim). This, in turn, presupposes that environmental factors are favourable for recruitment. Should the spawning stock be calculated to be at a level which in all probability will result in poor recruitment irrespective of environmental conditions, the stock is said to have an unsound reproductive ability (the spawning stock is below Blim).

Fishing mortality is connected with the degree of harvesting. If the fishing mortality is calculated to be below the precautionary level (Fpa), the stock is said to be harvested sustainably. If the fishing mortality is calculated to be above the precautionary level (Fpa), but below that which ICES has defined as the action limit for sustainability (Flim), there is a risk that the stock cannot be sustainably harvested. There is then a greater likelihood that the fishing mortality is at a level which will take the stock biomass below the precautionary level (Bpa). If the fishing mortality is calculated to be above the action limit for sustainability (Flim), the stock is said to be not harvested sustainably.

Places and areas

Relations to other monitoring

Monitoring programme
International environmental agreements
Voluntary international cooperation
Related monitoring