Migratory river fish populations down by 76% in the last 50 years: Report

Conservation groups have stated that the population of migratory river fish has decreased by 76 per cent on average over the last 50 years. According to reports by several conservation groups, this decline in migratory river fish could in the future prove to be ‘catastrophic’ for people as well as ecosystems around the world.

'Catastrophic' decline

As per the reports by conservation groups that include the likes of the International Union for the Conservation of Nature, WWF, World Fish Migration Foundation and the Zoological Society of London, the main reason for the decline of migratory river fish over the years has been overfishing by humans as well as a loss of habitat.

According to the report, at least one-third of all freshwater river species face the threat of extinction, with migratory river species ‘disproportionately threatened’. The study took into account 247 species of migratory river fish over the period of 1970-2016. The study found that on average each species saw a reduction in the population of about 3 per cent every year. The study concluded that Europe saw the sharpest decline in fish population at 93 per cent, followed closely by Latin America and the Caribbean which both saw a decrease in fish population by 84 per cent.

Researchers in their report stated that dams and other obstacles pose a great challenge to migratory fish species as they need access to rivers in order to complete their life cycle. The study found that North America saw the lowest reduction in the fish population, a decline of 28 per cent showing the effectiveness of fishery management.

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As per the reports, large fish like beluga, a sturgeon, or the giant Mekong catfish are especially vulnerable to dams and other river obstacles. They are the main reason for the drastic fish population in Europe, but the European Union has stated hat it aims to restore 25,000 kilometres of free-flowing rivers by the year 2030.

Light absorbing deep-sea fish

Scientists have recently discovered as many as 16 new species of deep-sea fish that have a special feature that allows then to absorb 99.5 per cent of all the light that strikes their skin.   Similar to the ultra-black Vantablack material, these fish absorb light very efficiently, so much so that even under bright light they appear a mere silhouette with no features being discernable by the human eye. According to reports, the new research shows that the special near-total light absorption feature of the fish comes from an abundance of melanin in their skin.

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