Sinop University Fisheries Faculty Fishing Technology Department Head Prof. Dr. Osman Samsun reported that as a result of global warming, the fact that the breeding period for bonito and bluefish in the summer shifts towards autumn due to the fact that the seas are still warm in autumn, causing the fish to form flocks and make their traditional migration movements out of the ordinary.
Regarding the catch efficiency and causes of bonito and bluefish, which are migratory fish with high economic value in Turkey, at the beginning of this fishing season. HIBYASpeaking to Prof. Dr. Samsun, which has been traditionally expressed for years among fishermen, said, “If bonito is caught intensively in a fishing season, bluefish are caught less in the same year. Sometimes, the bonito gives less catch in the year when the bluefish is caught a lot.” He emphasized that the fishermen were worried that although the bluefish fishing was more intense in the fishing season that started at the beginning of September 2021, and the fishermen were happy about it, the relatively less amount of bonito fishing and the lack of catch efficiency in the desired quantities, justifying his opinion.
Samsun reminded that the small bluefish are bluefish, and when they get a little bigger, they are called yellowfin, later the bluefish, which reaches an average of 18-20 centimeters in length.
Pointing out that when the bluefish gets a little bigger, it reaches a weight of 1-5 kilograms and takes the name Kofana, Samsun said:
“It is known that the shellfish, which was seen in large quantities in the fish markets at the beginning of the 1980s, were caught very rarely in 2021, even after 40 years, and even in some years the fishermen could not catch any large size bluefish, namely the shellfish, and there are many factors that cause this result. Every year, more pollution of the seas, increase in nitrogen and phosphate amounts, illegal and illegal hunting activities, overfishing, invasive species and finally climate changes that are being talked about more and more by the world public and international measures are being taken, in other words, global warming. is the warming factor. It is a pleasing development that the regulations on the minimum catchable length limit introduced in our country in recent years and the awareness-raising programs in the public have caused us to see that this fish has started to catch more fish in our country's territorial waters.”
prof. Dr. Osman Samsun pointed out that in years when the bluefish, which feeds on carnivores and has a dominant effect in the waters it is in, are found a little less and that the fishing of bonito is a situation that has been observed for years.
Stating that for years, the bonito fish, like the bluefish, has been traveling from the Aegean Sea to the Marmara Sea and then to the Black Sea for breeding migration, and that it has migrated to the east of the Black Sea, to the Rize-Hopa coasts by forming dense flocks due to the decrease in water temperature. Samsun said, “Fishermen call it 'exit'. Afterwards, it completes its migration movement in the opposite direction to the Sea of Marmara again, and from there to the Aegean Sea in larger sizes. This migration movement is also called 'landing' among fishermen. In this period, which we are at the beginning of October, bonito fishes have not been caught in large quantities as in the past years, as the sea water temperature did not fall to the desired degrees, because they did not cool down, they did not form a flock, and did not come together in large masses. Professional fishermen remain hopeful that the seawater will cool down and that they will then be able to fish large quantities of bonito again.” he said.
Expressing that the bonito, which is caught with capers in August and weighs between 150-200 grams on average, is also known as "gypsy acorns", Samsun said, "Small size and weight individuals are the most nutritious elements that reach the sea from streams and streams in the Black Sea after every rainfall. It has also been demonstrated in many studies that they provide an intense increase in plankton in the sea and that the smaller sized acorns fed with these planktons reach an increase in length and weight in a short time.” said.
Providing information about a research they did and published on bonito fish a couple of years ago, Prof. Dr. Samsun said:
It was determined that the height and weight of acorn individuals ranged from 15,4 centimeters to 47,6 centimeters (mean: 34,6±0,38 centimeters) and from 72 grams to 1288,8 grams (mean: 506,7±19 grams). Meat yield rate varies from 42,2 percent to 79,7 percent (average 69 percent). However, the minimum landing length of acorns, which is 25 centimeters in current laws and regulations, has been determined to be 37 centimeters for males and 42,5 centimeters for females in studies. Although the idea of applying a minimum landing length of at least 40 centimeters for sustainable bonito fisheries, based on the initial spawning length, has been brought to the agenda in the academic community, in practice, professional fishermen want and insist that this limit be kept as 25 centimeters.”
prof. Dr. Osman Samsun stated that many factors affect the current situation encountered in the 2021 bluefish and bonito fishing season, and it is necessary to remember the mucilage problem.
Expressing that the intense mucilage formation seen in the Marmara Sea in February, March and April this year coincides with the beginning of the migration time of migratory fish, there is also a negative factor for fish moving out of the open, Samsun concluded his words as follows:
“As a result of global warming, the fact that the breeding period for bonito and bluefish in the summer shifts towards autumn due to the fact that our seas are still warm in autumn, causing the fish to form flocks and make their traditional migration movements unusual. In order to be able to carry and preserve sustainable fisheries fishery and this important protein source to the next generations in a healthy way, especially professional fishermen in this sector, research institutions, academicians, public institutions that issue and implement laws and communiqués and all other stakeholders of the sector come together with a common mind. By constantly monitoring the ecosystem, taking appropriate and necessary decisions, making effective audits and implementing them becomes more important every day.”
Source: Hibya News Agency