Fishing mortality in the Barents Sea

Last updated 6 October 2020

The Barents Sea is an important fishing area. Every year large quantities of primarily cod, haddock, capelin as well as some shrimp, Greenland halibut and deep-sea redfish are caught.

Status and trend

Throughout history, fisheries have had a clear impact on commercial stocks with following impacts on the ecosystems. Fishing mortality is a measure of the proportion of fish stocks that are fished. The extent of fishing mortality is included in the assessments made when determining fishing quotas and harvesting rules. The data is gathered from calculations by the International Council for the Exploration of the Sea (ICES).

Causal factors

The fishing mortality is affected by the amount of fish landed by the fisheries and is thus related to the harvest rate. If the fishing mortality is calculated to be below the precautionary value (Fpa), the stock is harvested sustainably

Consequences

Fish mortality is an important part of the quota agreements. In the case where a fish stock undergo low development rate, the fisheries will receive smaller quotas and it may also lead to extended time- and area restrictions for the fisheries.

The capelin stock is an exception and has greatly declined from 2013 to 2016. The capelin fishing was stopped from 2016 and has still not opened in 2020. 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 greater than from fishing.

About the monitoring

Terms

• B_{lim =} Limit reference point for spawning stock biomass
• B_pa = Precautionary reference point for spawning stock biomass
• F_lim = Limit reference point for fishing mortality
• F_pa = Precautionary reference point for fishing mortality
• F_mp = Fishing mortality reference point as defined in management plans
• F_{MSY =} 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, assumes 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 diminishing 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 what ICES has defined as the action limit for sustainability (Flim), there is a risk that the stock cannot be sustainably harvested. Then there is a greater likelihood that the fishing mortality is at a level which will lead 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 not harvested sustainably.

Further reading