Icelandic fishermen report unprecedented mixing of herring stocks as increasing numbers of Icelandic summer-spawning herring move eastwards into offshore waters.

Iceland’s summer-spawning herring are moving farther east into the Atlantic, mixing with Norwegian spring-spawning herring in unprecedented numbers and raising concerns about the stock’s shifting distribution.

According to Icelandic broadcaster RÚV, fishermen have never encountered such high proportions of Icelandic herring while targeting the Norwegian spring-spawning stock east of Iceland.

Growing concerns over eastward migration

Ásgeir Gunnarsson, fishing operations director at Skinney Þinganes, says the mixing has become increasingly noticeable.

Norwegian and Faroese vessels have also caught growing quantities of Icelandic summer-spawning herring over the past four to five years.

Although the eastward movement shortens fishing distances for some Icelandic operators, Ásgeir fears the fish could continue moving further offshore.

He stresses that the entire Icelandic stock is not necessarily migrating and that scientists are better placed to assess the implications.

Icelandic herring makes up half of some catches

Samples taken after each trawl determine the proportion of each stock, with Icelandic herring sometimes accounting for up to 50% of catches.

The distinction matters because the stocks have separate quotas. Iceland’s quota for Norwegian spring-spawning herring is just under 89,000 tonnes, compared with about 76,000 tonnes for Icelandic summer-spawning herring.

Fishing fleet switches between stocks

Icelandic vessels are now completing their Norwegian spring-spawning herring season and turning towards domestic summer-spawning herring.

Ásgrímur Halldórsson SF has already headed towards Faxadýpi to begin fishing.

The two populations spawn at different times: Icelandic herring in midsummer and Norwegian spring-spawning herring off Norway in spring.

According to Ásgeir, Iceland’s main herring export markets include Poland and Ukraine, while France has also emerged as a buyer.