Hooded seal (Cystophora cristata)

A hooded seal laying on snow-covered ice.
Photo: Kit M. Kovacs & Christian Lydersen / Norwegian Polar Institute

The stock of hooded seal has declined steadily after the last war, even after harvesting regulations were imposed in the 1960s. The West Ice stock has now been protected, there is a moratorium on harvesting, and the stock size has stabilized at a low level. The hooded seal is one of two pelagic seal species harvested in Norwegian waters.

What is being monitored?

Population size in the West Ice

Loading chart ...

Far too many hooded seals were harvested in the West Ice in the first two decades after the Second World War. The stock therefore declined up to the end of the 1960s, when hunting regulations were introduced. Despite these, the decline continued until around 1980. After that, it seems to have stabilized at a low level (approximately 87 000 seals), which is probably less than 10% of the level 70 years ago. The population was therefore protected in 2007. The blue line shows the modelled total stock, the red line the modelled pup production and green dots show the estimated pup production based on aerial censuses.

 

Status and trend

Consideration of all the models suggests that the hooded seal stock in the West Ice declined significantly between the end of the 1940s and around 1980, most probably due to high hunting pressure. It seems to have stabilized at a low level since then, at probably no more than 10–15 % of the level around 60 years ago.

Management of the species is based on estimates of pup production, derived from aerial surveys carried out in 1997, 2005, 2007 and 2012. Fertility data used in the model runs are from 1990–1994 and 2008–2010. After the aerial survey in 2012 the stock size was estimated to be 84,000 (95% CI: 68,000–100,000).

There are no comparable data on stock size and food availability that could enable an assessment of population dynamics in relation to food availability.

Causal factors

Since the hooded seal used to be hunted, the monitoring was originally largely aimed at providing a basis for setting hunting quotas.

Consequences

In its long-term management strategy based on the precautionary principle, ICES has defined a lower limit for the population level that is 30% of the maximum known figure for the stock. It recommends that no form of hunting should be permitted when a stock is at or below that level.

Since the hooded seal stock in the West Ice is still below this level today, ICES advises that no hunting should take place.

Following the ICES recommendation, hunting was halted in 2007 except for a limited catch for research purposes.

About the monitoring

It is interesting to monitor the hooded seal because it is dependent upon ice and may be affected by climate change.

The management is based on estimates of the pup production made on the basis of aerial counts. This method has been chosen because it is simpler to count pups than adults in the quite short breeding season. Pups stay on the ice floes during surveys, while adults may disappear into the water. The methods to estimate the total stock size are thus indirect (model runs) and are also based on knowledge about the reproductive status of females derived from other types of survey.

Places and areas

Relations to other monitoring

Monitoring programme
International environmental agreements
Voluntary international cooperation
Related monitoring