Topic: North Sea herring

Herring is a key species in the North Sea; important as a predator on crayfish and as prey for other fish stocks, seabirds and marine mammals. The North Sea herring begins to reach sexual maturity when it is 2–3 years old, but the proportion mature at age will vary from year to year, depending on food supply and growth. Herring spawn on the bottom, and depend on a special bottom substrate for spawning. Each female produces between 10,000 and 60,000 eggs, depending on the length of the fish. The eggs are spawned and fertilized just above the bottom, sink and stick to sand, gravel, rock, seaweed and kelp.

The larvae hatch after 15–20 days. The newly hatched larvae rise in the upper water layers where they drift with the current to breeding areas in the southeastern North Sea and Skagerrak – Kattegat. Here they stay until they reach sexual maturity and migrate towards the spawning areas west of the North Sea.