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- And the fish will eat: Korean perch threatens shrimps and mutton in the Black Sea
And the fish will eat: Korean perch threatens shrimps and mutton in the Black Sea
Russian scientists have studied the properties of Korean perch, which actively breeds in the Black Sea. Previously, he lived only in the Pacific Ocean, but he found himself in an unusual region due to human activity. The results of scientific work show that fish develop even faster off the Crimean coast than in their homeland. Therefore, the alien has a good chance of becoming a mass species. But it can create problems for local shrimps, crabs and the famous mutton, as well as deprive other Black Sea predators of their food supply.
Korean perch in the Black Sea
Specialists from the A.O. Kovalevsky Sevastopol Institute of Biology of the South Seas of the Russian Academy of Sciences conducted a study of the Korean or dark perch population off the Crimean coast. Previously, this species, which lives in the Pacific Ocean, was not found either in the Black Sea or in the neighboring Mediterranean Sea. However, having first entered the coastal waters of Western Crimea, most likely due to human activity, it began to actively reproduce and increasingly become the prey of fishermen along the coast. An article with the results of the work was published in the scientific journal Scientific Reports.
The data collected by scientists show that in new conditions, the perch develops even faster than in its natural Pacific range. This gives him a great chance to eventually become a mass inhabitant of the Black Sea waters. But it can also pose a threat to both those local species that the perch feeds on, for example, for shrimp and mutton, and for those local predators, including scorpions and dark humpback, which consume similar food items.
— At an early age, the Korean perch feeds on shrimps, sometimes crabs, and then gradually switches to fish. He becomes an active and voracious predator. Like any invasive species, perch will somehow affect a new ecosystem for itself. For example, it can compete with the indigenous inhabitants for a food supply. In general, the prospects for the settlement and growth of the Korean perch population in the Black Sea can be considered favorable, which can cause significant changes in coastal ecosystems," said Igor Tamoikin, a junior researcher at the Department of Ichthyology at the INBYUM Research Center.
For the first time, Korean perch was discovered in the Black Sea in 2013 in the Balaklava area. At that time, experts could not correctly identify the type of fish, as they did not even imagine the possibility of meeting an inhabitant of the Pacific Ocean here. Its natural habitat is off the coast of Korea, Japan, the Russian Far East, Southern and Northern China. In Asia, fish meat is considered a delicacy and it is actively bred artificially.
According to Crimean scientists, the perch could have entered the Black Sea region either with the ballast waters of ships, or with oyster fry, which were brought for breeding from the Far East. Over the years, this species has become more common off the coast of Crimea. In total, the scientists studied 18 individuals caught after 2019.
The weight of the largest specimen was 1610 g. It was a three-year-old female, full of eggs. Like other caught perches, it developed perfectly, it had a high fat content and there were no parasites. The stomachs of the fish were filled with food. The scientists compared the characteristics of the available specimens with the data obtained in the natural range of the species. Most of the Black Sea individuals were superior to their Pacific relatives. This made it possible to assume with high probability that the growth rate of the new inhabitants is much higher. That is, the perch feels in a favorable environment.
The new species has some advantages that can help it to explore these territories faster. Firstly, unlike most Black Sea coastal fish species, which are Mediterranean and thermophilic in origin, it does not hibernate, so it can actively feed in winter, expanding its range. Secondly, it is a viviparous species. The female releases live fry on Wednesday, rather than eggs, which the male has yet to fertilize. This also increases the perch's chance of successful survival.
The species has already been discovered off the coast of the Caucasus, Bulgaria and Turkey. However, according to scientists, its distribution was off the western coast of Crimea, because it is caught here more often and most often, and individuals are larger than in other areas. According to experts, perch is actively expanding due to new generations of fry born in the Black Sea, which are carried by currents. The Pacific inhabitant has already been recorded in the Marmara Sea, which means that it can be expected to appear in the Mediterranean soon.
Korean perch prefers to settle in coastal rock formations, grottos and caves, which are plentiful off the coast of Crimea. There are many species of small fish that can become its food base. If the perch continues to actively breed here, then due to the high taste characteristics of its meat, it may well become a popular object of coastal commercial fishing in the future.
What are the dangers of aliens from distant seas?
Alien species cause significant damage to the ecosystem and economy only if they take root in a new region. Korean perch can become such a naturalized species, ecologist Artyom Akshintsev explained to Izvestia.
— Right now, there is an active study and discussion of the ecological impact of this new species on the ecosystem of the region. After all, it is a predatory fish that knocks out both fry of local species and invertebrates, consumes a lot of caviar, larvae, and competes with local predators. All this is likely to weaken the population of commercial fish that are already being harvested in the Black Sea," he said.
In addition to perch, sea walnuts, for example, have spread in this sea in a similar way. According to the expert, the damage from its introduction into the ecosystem is estimated at $240 million annually. The other is rapana shellfish, which costs $500 million in annual damage. Although their industrial processing partially reduces losses. In total, more than 200 invasive species have been registered in the Black Sea, he added.
Korean perch is likely to become a valuable fishing object, and subsequently the species will get from the Black Sea to the Sea of Azov, expanding its habitat, says the head of the Innovation and Technology Center for Aquaculture at Kuban State Agrarian University, an expert at FoodNet NTI Ekaterina Maxim. Therefore, comprehensive studies will be needed in order to regulate its numbers and establish the main allowable catch.
— We are on the threshold of a very rapidly changing, dynamic structure of the Azov and Black Seas. It is necessary to use government programs in order to conduct scientific research as soon as possible and to appoint measures to control the species within the framework of the state. Perch will compete and displace other species, and occupy its niche is a natural biological process," the expert believes.
Scientists, business and government need to work together so that, for example, entrepreneurs are ready to catch and process new products, the expert noted.
— The Korean perch is a predator, it can grow up to 3-4 kg, forming a population. In this case, it will acquire commercial importance and will have an impact on the local fauna, collide with aquatic representatives who have a similar food base. This will lead to a change in the relationships within the communities into which it is embedded," said Sergey Kosogor, head of the Smart Supply Chain segment of the FoodNet NTI working group.
According to Alexander Vasenev, chairman of the Opora Russia mentoring commission and an expert at the NTI Thinking Club, the perch could easily have migrated to the Black Sea via the Indian Ocean on its own. Since it is a natural, non-genetically bred species, it does not pose a danger to the region, he believes.
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