The FISH stock in the Adriatic Sea is decreasing at an alarming rate, this is influenced by overfishing, climate change and the immigration of new species of fish that threaten the existing fish population, that's why experts warn that "the Adriatic we knew is disappearing". "Fishing and our fish resources have great difficulties, climate change is a big problem, the Adriatic as we knew it is disappearing," said Alen Soldo, a professor at the Department of Marine Studies at the University of Split, in an interview with Hina.

Completely ban fishing where the fish have not yet spawned

In most Mediterranean countries, including Croatia, bluefish is the main part of the total catch, the fishing industry fears that fishing will be stopped due to overcatch, and administrative measures are either drastic or delayed. "I have been warning for a long time that the state of blue fish in the Adriatic, sardines and anchovies, will reach a low point. When that happened, the EU demanded a drastic reduction in catches, and even a stop. Then the measures that no longer work began," says Soldo . He proposes to introduce a complete ban on fishing in an area for a certain period of time if too young fish, which have not yet spawned, are caught.

"Invasive species change the environment"

Merely reducing the amount of catch without enabling reproduction (spawning) no longer works today. We deal with firefighting measures instead of being preventive, according to Soldo. He advocates that the Croatian economic zone be completely prohibited for fishing, because that area is one of the main spawning grounds in the Adriatic. Most of our fishing fleet does not go to that area, considering that more than 94 percent of our fleet consists of boats smaller than 12 meters, which are prohibited from going that far from the coast, so such a decision would not affect our industry. Soldo also warns that invasive (immigrant) fish species are changing the natural environment of the Adriatic Sea. "One of the most invasive species, the lionfish, was recorded for the first time on our part of the coast last year, and several times this year. It is known that this fish has changed the natural environment in many places in the Mediterranean," warns Soldo.

The invasive species is spreading because of the lack of sharks

Jakov Dulčić, a scientific advisor at the Institute of Oceanography and Fisheries in Split, points out that over the past three decades, the arrival of 46 new species of fish has been recorded in the Adriatic Sea, where more than 460 species of fish live. He says that one of the worst invasive species in the Mediterranean Sea, the firefish, was spotted near Vis at a depth of 15 meters in August 2021 and in August this year near Račišće on the island of Korčula. The spread of fireflies, native to the Indo-Pacific, eases the shortage of native predators, namely overfished sharks. "The firefly looks beautiful, but you should take care that its sting can even be deadly. However, it can be prepared for food without any fear," explains Dulčić. Experts are concerned that aggressive invaders threaten native fish species, and some of them pose a threat to human health.

107 exotic edge species came to the Mediterranean

"One example is the stonefish in the eastern Mediterranean, whose sting can be fatal. One of the deadliest is the blue-spotted trumpeter, which is also called the 'lessepsia sprinter' because of its rapid conquest of the Mediterranean," says Dulčić. Since he participated in the creation of the second edition of the 2021 Atlas of Exotic Fishes in the Mediterranean Sea, he says that in the 20 years since the first edition of the Atlas in 2002, 107 exotic fish species have entered the Mediterranean, more than in the entire previous century. Invasive fish species change the demographic structure of the fish population, in the eastern Mediterranean some new species have established their own populations. "It is significant for the Adriatic that the presence and number of settlers mainly refers to the areas of the middle and southern part because there is a temperature barrier in relation to the northern part," explains Dulčić.

Declining fish biomass in tropical regions

If there are significant changes in sea temperature, we can very soon expect a bad scenario with the state of biological resources in the Adriatic Sea. The latest research warns of serious threats posed by climate change in developing countries, where a significant decline in fish biomass is expected by the year 2100. the main source of food and income," warns Dulčić. Raising awareness is a necessity, otherwise we could be permanently late in preserving fish resources in our sea, experts point out.

Source: Index.hr web - September 3, 2023.

https://www.index.hr/vijesti/clanak/u-jadran-stiglo-46-novih-vrsta-riba-nestaje-more-koje-smo-znali/2492352.asp