The Baltic herring is a staple food for many people in northern Europe, but its future is uncertain due to the combined effects of climate change and pollution.
A new study by Finnish researchers revealed that the herring population has declined by more than half since the 1970s, and faces further threats from rising temperatures, falling salinity, and harmful algae blooms.
The researchers warned that the herring could disappear from the Baltic Sea if no action is taken to protect its habitat and reduce fishing pressure.
The Baltic Sea: a unique and vulnerable ecosystem
The Baltic Sea is one of the largest brackish water bodies in the world, meaning that it has a mixture of fresh and salt water.
It is surrounded by nine countries and is home to more than 100 million people. The sea is also a rich source of biodiversity, hosting more than 1,500 species of plants and animals, many of which are endemic or rare.
However, the Baltic Sea is also one of the most heavily polluted marine ecosystems on the planet, due to the high population density and industrial activity in the region.
The sea receives large amounts of nutrients, such as nitrogen and phosphorus, from agricultural runoff, sewage, and atmospheric deposition.
These nutrients cause excessive growth of algae and plants, which consume oxygen and create dead zones where no life can survive.
The sea also suffers from chemical contamination, such as heavy metals, pesticides, and pharmaceuticals, which can accumulate in the food chain and affect the health of wildlife and humans.
The Baltic Sea is also highly sensitive to climate change, as it is shallow and has limited exchange with the Atlantic Ocean.
The sea is influenced by both marine and continental climates and experiences large variations in temperature, salinity, and ice cover.
Climate change is expected to increase the frequency and intensity of extreme weather events, such as storms, floods, and droughts, which can affect the hydrological cycle and the water balance of the sea.
It is also projected to increase the average temperature and precipitation in the region, which can alter the salinity and stratification of the water, and affect the circulation and mixing of the sea.
Also Read: Longest Heatwaves in Northern Baltic Sea: Marine Ecosystem To Suffer From Damages
The Baltic herring: a key species under threat
The Baltic herring is a small, silvery fish that belongs to the same family as the Atlantic herring. It is one of the most abundant and commercially important fish species in the Baltic Sea, accounting for about 80% of the total catch in Finland.
The herring is also a vital link in the food web, as it feeds on plankton and is preyed upon by larger fish, birds, and mammals.
The Baltic herring has adapted to the brackish conditions of the sea and can tolerate a wide range of salinity and temperature.
However, the herring is also vulnerable to the changes and stresses that are affecting the Baltic Sea. The herring population has declined by more than 50% since the 1970s, according to a recent study by the Natural Resources Institute Finland.
The study found that the main drivers of the decline were overfishing, eutrophication, and climate change.
Overfishing has reduced the size and age structure of the herring stock, making it less resilient to environmental fluctuations.
Eutrophication has reduced the quality and quantity of the herring's food, as well as the oxygen levels and the light penetration in the water.
Climate change has increased the temperature and reduced the salinity of the sea, which can affect the growth, reproduction, and distribution of the herring.
It can also increase the occurrence and severity of harmful algae blooms, which can produce toxins that can kill or impair the herring.
The researchers warned that the herring could face local extinctions or even disappear from the Baltic Sea if the current trends continue.
They called for urgent actions to reduce the nutrient inputs and the fishing pressure on the herring, and to implement adaptive management strategies that take into account the effects of climate change.
They also suggested that more research is needed to understand the complex interactions between the herring and its environment and to identify the best practices to conserve and restore the herring population.
Related article: Climate Change Could be Keeping the Baltic Sea Starved for Oxygen