There could be a little more in the future off the Russian Pacific island of Sakhalin salmon sharks (Lamna ditropis) turn up. The reason would not be a suddenly growing shark population, but more available prey: the stocks of Sakhalin-Hokkaido herring have increased significantly in recent years.
The assessment comes from loud a report from Sakhalin from the Sakhalin branch of the VNIRO. The experts formulate it cautiously: The richer food supply could lead more salmon sharks into the coastal waters, but an abrupt or large increase is expressly not expected. So far, an increase in herring has been observed – not a counted increase in sharks.
Herring catches reach their highest level in decades
Official data from the Russian Fisheries Research Institute VNIRO confirm the biological background. In 2025, 29,050 tons of herring were caught in the East Sakhalin subzone – the highest in 70 years. In spring 2026, the catch rate was once again higher than in previous years. The recommended catch for the region was later increased to almost 75,000 tonnes.
However, catch quantities are not a direct measure of the size of a fish population. They also depend on quotas, effort, weather and the accessibility of the swarms. In this case, long-term VNIRO observations support the statement that the Sakhalin-Hokkaido population has increased; the record catches are an additional signal.
salmon sharks follow their prey seasonally
salmon sharks live in the north Pacific and belong to the family Mackerel sharks. They can travel long distances and use cold, food-rich waters seasonally. Before Sakhalin they follow, among other things, schools of humpback and ketal salmon. If this prey decreases, larger herring supplies may provide an alternative food source.
Such a shift would initially be a change in seasonal distribution, not automatically an increase in the entire population. More sightings in one location can occur because existing animals are intently pursuing prey. For a population trend, comparable recordings, tagging data or standardized catches would be necessary over the years.
Why a shark boom remains unlikely
The Russian experts point out that large sharks appear irregularly in the cold northern coastal waters. Warmer currents and higher water temperatures may favor their migration, but the breeding and core areas are further south. More herring alone does not override these biological limits.
