ICES report finds herring stock boundaries biologically inaccurate

A scientific review by the International Council for the Exploration of the Sea (ICES) has concluded that current management boundaries for western herring stocks do not align with actual biological populations. The report indicates that stock mixing is far more extensive than previously assumed, with genetic sampling confirming that fish caught in the Irish Sea are a mix of Irish Sea autumn spawners and fish originating from the Celtic Sea across all age classes.

The review also challenges the validity of the 4° West boundary, which separates assessments west of Scotland from those in the North Sea. Findings suggest this line was established as a convenient statistical reporting boundary rather than a biological division. Researchers noted there is “no historical or contemporary evidence” to support the separation of the west of Scotland autumn-spawning stock from North Sea autumn-spawning herring, as they appear to be the same biological population.

These findings reopen long-standing debates between scientists and the fishing industry regarding the accuracy of catch advice and total allowable catches (TAC) for various stocks in the Celtic Seas, including those in the Irish Sea, the northwest and west of Ireland, and the western English Channel.