Changes in sea conditions in Sargasso affect eel fishing

Eel species in the United States are disappearing very quickly from the restaurant menus because supplies are declining dramatically in the North Atlantic. While the reason for the eel slump remains mysteriously similar to the migration of this animal, recent research has been done by a NOAA scientist and colleagues in Japan and the United Kingdom. Marine climatic conditions may be a major factor in the decline in reproduction and eel survival rates.

'Despite many aspects of the egg-laying process and the developmental history of animals that have not been thoroughly explored, they are clearly adapted to development in southern Bermuda Sargasso Sea,' biologist NOAA. Kevin Friedland said. 'They exist as larvae within a year or more and tend to live in the upper 100 meters of water (about 330 feet), so any changes on the surface of the sea will be very influential. big to the essential stages of their development. '

Friedland and colleagues found a significant correlation between the oscillation of the North Atlantic, decade-long circulation of the marine climate, and long-term variation in the pre-mature period, often referred to is glass eel. Considered a precious dish, catching glass eels has always been a controversial topic because of concerns about reserves that some people think are nearly exhausted. Since the 70s, the number of eels coming to Europe is believed to have decreased by more than 90%.

The eel industry in the United States and Europe is declining.(Photo: US fishing and wildlife life services)

In a study published recently in the journal ICES on marine research, scientists reviewed data on catching eel eels since 1938 in Den Oever Netherlands. Excluding the war years no data was collected, time series correlated with a wide-scale measurement of weather changes, such as NAO with specific changes such as temperature Sea surface, wind direction and mixture of natural ingredients in the upper layers of the ocean control the reproduction process. Changes in these factors match the changes in reproduction.

Eels in the Atlantic and Pacific are low-level migratory animals, meaning that most of their life they live in rivers, lakes and estuaries but migrate to the sea to spawn. Eels in Europe and the United States spawn in the Sargasso Sea , located between the Bahamas and Bermuda, the temperature difference is expressed in winter and spring forming the northern boundary of the spawning area. It is believed that eels use this to find their partners and ensure the survival of the born babies.

After hatching, their leafy transparent larvae, called leptocephali , lie on the surface of the sea for about a year and then drift towards the Gulf of warm water (from Meehico Bay through the Atlantic Ocean to Europe). Europe), bringing home eel species to European coastal waters. Along with the Gulf, the Antilles and other western flows in the North Atlantic Ocean, the US eel returns to the East Coast of the United States, where they inhabit estuaries like Chesapeake Bay. .

Once back in the coastal waters, the larvae from 2 to 3 inches long turn into eel shapes throughout their adulthood, or glass eels, names are placed in their shape. They gather in estuaries and wait for the river to warm up before swimming upstream to freshwater, where they change color by absorbing green and brown pigments to become the usual yellow color. They can live up to 20 years in the river and reach a common length of about 30 inches before returning to the sea. But before returning to the Sargasso Sea, they underwent another body change, they received more silver pigment to become silver eels .

"Changing Sargasso's marine climate conditions caused by NAO could affect the eel breeding and survival rate of Europeans ," Friedland explained. 'The results we found provide evidence of a link between the decline in reproduction and the specific environmental changes in the spawning and larval development areas of the Sargasso Sea. Japanese eel numbers in the North Pacific also have similar climate pressures stemming from the El Nino phenomenon. '

This decline is due in part to natural changes in the North Atlantic, but there are also other challenges facing eel species such as: changing habitats, abusive fishing and parasitic flora and fauna. , river barriers such as hydropower plants or dams, and environmental pollution.

Friedland and colleagues said that the study showed that changes in marine climatic conditions contribute to reducing the growth of European eel species and may also reduce the number of US eel species, but they also emphasize that Human factors in these continental stages of life should also be taken into account when calculating management and future research plans.