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Kitaplar » AQUACULTURE » Mediterranean Yellowtail Fish Breeding



 MEDITERRANEAN YELLOWTAIL FISH BREEDING

 

As in many branches of fish farming, the country that pioneers yellowtail production is Japan. The first studies on the breeding of this fish started in 1928, but important developments took place after 1960. Yellowtail is very important as an edible for the people of Japan and is valuable for the production of raw fish meat called sashimi. Sashimi dish is a dish in which fish meat is eaten raw with various sauces, especially soy. In addition, yellowtail meat is used in the production of a dish called Sushi (sushi) made with rice and raw fish. Yellowtail is also consumed boiled or fried. Salted and dried yellowtail meat is a favorite food in Japan. As a result of the population growth and the development of the economy in Japan, the people's orientation to good fish meat consumption caused this fish to become expensive over time. Occasional reduction in hunting has encouraged breeding. The cooking value of many small fish, which were formerly considered human food, has decreased as a result of the increase in wealth. The possibility of using these fish as fish feed inexpensively has also affected yellowtail breeding.

It has been recorded that they reach a maximum length of 96 cm and a weight of 13 kg in nature. Its normal measurements are 60 cm height and 3-5 kg weight. In culture cultivation, 40 cm height and 0.800-1 kg weight are the smallest marketing measures. The back of their body is blackish blue and the abdomen is silvery white. They have a yellow-green color and a prominent lateral line. There are 6 metallic yellow-brown and 11 red brown bands vertically in the juveniles, which are 30-80 mm long. With these colors, they look a little different from their mothers. The body of the fish is in the form of a missile and slightly flattened to the side. There are 5 rays on the dorsal fin. There are 6 rays in small fish up to 30 cm in length. These have approximately 29 to 36 small rays. On the anal fin, there is one main ray, between 17 and 22 thin rays. There are between 210 and 220 scales on the lateral line.

Yellowtail fish are generally warm water fish. They spread along the warm Kuroshio current from Taiwan to Hokkaido Island in the north. It is observed that fish migrate northwards in the spring months and reverse migration in the autumn months. It is recorded that the Seriola sp species exist in the Mediterranean in our country. It is thought that similar breeding studies can be carried out on this fish. However, as in Japan, plenty of catching opportunities should be explored and studies should be conducted on this subject. Because, as will be mentioned later, the supply of offspring in yellowtail breeding is provided by catching. In recent years, it has been observed that positive results have been obtained from studies on larvae production.

Yellowtail eggs are pelagic. It has a diameter of 1.15 to 1.44 mm. There is an oil droplet with a diameter of 24-0.37 mm in the egg. Hatching from eggs takes approximately 51 hours at temperatures of 18-24 degrees. The length of the newly hatched larvae is around 3.5 mm. The regions where the temperature is 19-21 degrees and the salinity is 19.1-19.3% are the places where the juvenile shelter is at the maximum level. With these values, the areas where juvenile can be caught can be determined by following the water conditions. Billions of larvae that emerge from the eggs are caught in the currents and move towards the north. They live in places where algae are abundant and zooplankton, which has an important place in the feeding of the offspring, are abundant. Under these algae clusters, larvae feed on Copepodsızs, especially from zooplankton, and reach a length of 1.5 to 15 cm. Fish of these sizes are called mojako in Japan. Mo part of this word means algae and jako part means juvenile fish. Fish exceeding 15 cm, separate from algae masses and begin to swim freely and move to open seas. From 4 cm in length, other fish juveniles start to take a significant place in the food of fish. The main food of large fish are other small pelagic fish such as anchovy, sardines and horse mackerel and their fry. It has been determined that the life span of yellowtail fish is around 7 years.

 

THE STATUS OF YELLOW TAIL BREEDING IN JAPAN

 

The first breeding studies of yellowtail fishes were carried out in Kagawa Region in 1928. With successful results in these regions, it has been observed that the cultivation has spread rapidly to other regions. The production, which was 300 tons in 1938, reached 30,000 tons in 1968 and then 150,000 tons.

This development in yellowtail farming is really interesting. An increase from 300 tons to 150,000 tons in a short time is promising in terms of fish farming. Today, yellowtail farms are widespread south from central Japan. Especially in the southern regions where water and air temperatures are higher, important growing centers have emerged. Enime Region is leading in Japan in terms of yellowtail cultivation. Due to the increase in breeding farms, it is seen that yellowtail is shipped to the market in Japan in all seasons of the year. The result of this is that a fixed price guarantee has emerged and a safe breeding environment has emerged that will encourage breeding. However, the increase in the amount provided by hunting towards the end of the year creates an abundance in these periods. Although there is a slight decrease in the price, the increase in consumption during these months provides a balance in the prices.

The stages in yellowtail fish farming can be summarized as follows: catching offspring, rearing farms, fattening period in net cages, marketing

It can be said that yellowtail fish farming in Japan is generally practiced in three ways. These are the breeding grounds gained by the encircling of the coves on the seashore, the areas surrounded by the sea with nets and the net cages. Especially in net cages, aquaculture has increased more than other methods in recent years. Because in the production of net cages, it is possible for sea water to enter from all sides of the net and the controls can be done much easier and more successfully than other methods. As a result, it is observed that there is a significant increase in the spread of net cages.

Inspired by this breeding method, significant success has been achieved in our country in the studies of sea bream and sea bass in net cages.

It has been reported that seafood cultivation for 2000 in Japan is 1.220.000 tons. 260.000 tons of this is marine fish. The rest are algae and shellfish. In this production, yellow tail production takes the first place with 150 000 tons. It is recorded that the desired weight for yellowtail fish is 4 kg and that the fish reach this weight in 18 months. 80,000 tons of the remaining fish are coral. Others are flatfish, balloon and tuna. Most of the juveniles used in yellowtail breeding are obtained from nature. An important line of business has developed in catching juvenile fish in Japan. Adult egg yellowtail fish are found around Okinawa Island in the south in March. They start to migrate north in the spring. It is seen that fish reaching the shores of Kyushu Island in the south of Japan in April and May lay their eggs during this period. The fry, which are abundant on these coasts and shelter under the moss masses moving with the currents, are caught by the hunters specialized on the subject. The offspring caught here are sold to breeders.

The catch of yellowtail juveniles is done by certain people. These persons are given special permission by the state and the number of offspring that can be caught is also stated.

Separating the caught juveniles according to size is considered as an important study. If the classification is not made according to the lengths, it is possible to encounter up to 50% loss.

After the juveniles are classified according to their size, they are taken into very small porous nylon mesh cages. Net cages where juveniles are stocked can be between 2 and 50 m2 surface width and 1-3 m depth. Different applications of various businesses can be seen in these subjects. The widespread use of net cages has an important role in the increase of successful practices in yellowtail fish farming. After successful results with net cages in yellowtail fish farming, fish farming in net cages started to be applied in other fish species. Frequent presence of fish in a small cage and reduced movement of fish results in less energy loss. As a result, fish have to use their food for meat production. In addition, it is easier to care and control the offspring in the net cage.

It is compulsory to obtain permission from the relevant government institutions in determining the places where the net cages will be placed for both small and large fish. It is noted that 1 person is sufficient for the maintenance of 10-15 mesh cages in Japan.

When the babies placed in net cages start to take feed, they are fed little by little and carefully. The first feeds are divided according to the size of the fish. In this diet, fish meat with white meat is preferred. In addition, live meats such as small shrimp, which are called goats in our coastal regions, are also a popular food. Especially in Japan, these small shrimps, which are collected from the oceans by bottom trawls and called krill, are hunted abundantly and used as feed in aquaculture. Yellowtail fry are not given large amounts of anchovy meat as in other fish species. Because the unsaturated fatty acids found in anchovy meats can be harmful for juvenile fish. In fact, up to 100% mortality can be seen as a result of continuous feeding with anchovies. But there is no harm in giving it intermittently. Any deficiencies that may occur when anchovy meat is given occasionally can be easily covered with different feeds given at other meals. Some breeders put lights on the net cages where the offspring are located. By eating plankton that comes to light, the puppies are provided with good quality food.

It is preferred that the offspring to be used in stocking are large up to 50 gr. Because the mortality rate is less in fish at this age and there is not much feeding problem. The puppies reach this weight in cages generally in 4-6 weeks. As a result of this demand, businesses that only breed and sell offspring were born. These businesses have mastered raising offspring. The offspring raised in such establishments can be transported in private boats even to the enterprises 100-200 km away.

Breeding Big Fish

In recent years, it has been observed that net cages have been used in the breeding of yellow tail fish. The size of the cages used and the materials used depend entirely on the size of the fish and the weather conditions in the area where the net cage will be installed. In the years when the disease is seen, the vitality may decrease by 30-40%. In the second year, the vitality becomes 80-90% under normal conditions. The amount of fish that can be raised in a cage is related to many factors such as the depth of the net cage, water current and contamination. The temperatures that yellowtail fish can live are between 7 and 280 degrees. Optimal temperatures for development are 24-26 degrees. The feeding of yellowtail fish according to the temperature condition is as follows. At values below 110 degrees, fish do not take food. At 11-13 degrees, fish take less feed and do not develop. They take feed at 14-17 degrees and there is little development. Fish at 18-27 degrees; eagerly feed and develop rapidly. Fish with values above 280 degrees have no appetite and show many behavioral disorders.

The desired salinity ratio is around 0.25%. A salinity drop of 0.5% or less due to heavy rain causes adverse effects on fish. Deaths occur in unhealthy fish. Healthy fish lose their appetite. The gradual decrease in salinity is less effective in fish and the fish can get used to this slow salinity decrease.

Under normal conditions, one-hour oxygen requirement of yellowtail fish per kg of weight is 500 ml. Normal sea water contains more than 5-6 mg / lt oxygen. If the amount of water that will pass through the net cages in a certain time is known, the total amount of oxygen the fish can receive can be estimated. Thus, the number of fish that can be placed in the net cage is determined. It is possible that this method we have explained can be considered for all fish production. In fish production in net cages, the oxygen content is required to be higher than 5 mg / lt. If the oxygen level drops to 3-4 mg / lt, the fish lose their appetite.

There should be no contamination in the areas where the net cage will be installed. It would be good to choose coves that are clean and closed to winds. Conditions should be suitable in terms of buildings and roads to be established on the shore.

 

Feeding

 

In yellowtail farming, feeding the fish once a day is preferred in many enterprises. Some businesses feed twice a day. In order to prevent overfeeding and to ensure that every feed given is taken, it is taken as a basic principle to keep the fish hungry. Many businesses do not feed the fish for a day or two, especially on weekends. This practice does not have a negative effect on the health of the fish and provides significant benefits in terms of workforce. The amount of feed that should be given daily decreases as the fish grows and the water temperature decreases.

Feed given to fish must be fresh and must be stored in cold storage. Feeding bad food can cause big losses. Fodders are generally stored at -20 degrees. Feeds kept in cold weather should be thawed before feeding. Large fish are slaughtered or passed through a machine and given to fish. Like anchovy, fish meats called Chiaminase, which form B vitamins and contain enzymes are not often given. It is known that yellowtail fish are not very keen on pellet feed and feed. In recent years, production and use of artificial feed for commercial purposes has increased. It has been noted that the juveniles can be fed by mixing 70% fish meal with 20% fresh fish and 5-10% gluten in the diet of juvenile fish. It is also beneficial to add some vitamins and minerals to this mixture.

The development of fish is very fast. Fish reach 1-1,5 kg in weight and 30-50 cm in one year. Those left to the second year reach 40-60 cm in length and 2-3 kg in weight. It is also possible to reach 4-5 kg of fish at the end of the second year with regular and continuous feeds in some farms.

Since the shores of Japan are open to the ocean, it is seen that the waves reach great dimensions even in the bays. Especially between the end of summer and the beginning of winter, the sea becomes quite choppy. In this period, the breeders take measures to keep the net cages 1,5 m below the sea surface and protect the cages from wind and storm by covering the cage well. In some regions, special wave breakers are made from simple buoys to protect the business from winds.

 

 

 

Problems in Yellowtail Aquaculture

Yellowtail breeding in Japan is a constantly developing sector. It is expected to develop further as brood procurement opportunities increase and feed problems are resolved. It is normal for many problems to arise with this development.

        The first of the most important issues in breeding is the supply of offspring. However, with a good organization, various measures are taken to minimize this problem. It is also mostly successful. Many researches are carried out on the production and supply of puppies under human hands. Since the offspring catching studies are carried out continuously and in a controlled, no adverse effect is mentioned for now. In the future, it is imperative to ensure the absolute production of the offspring, for a complete and reliable breeding. For the production of 1 kg yellowtail fish, around 8-10 kg of fresh fish meat is used. However, the use of artificial feed has also increased in recent years. While there is hunger in many countries of the world, the accuracy of producing 1 kg of fish meat by consuming 10 kg of small fish meat is an open question. For this reason, it is said that it will be beneficial if breeding depends on artificial feeds as much as possible. Extensive studies are also carried out on these issues.

        Breeders tend to overfeed to ensure that the fish develop quickly. As a result of this trend, unconsumed feed passes the net cage and collapses to the bottom of the production area and as a result, it can pollute the environment by odor. Contamination is an important problem, especially in gulfs with large numbers of net cages. In addition, throwing the minced fish meat into net cages every day causes the fats in the meat to mix with the water and cause the accumulation of fat in the upper parts of the water. It is also possible to encounter red-tide phenomenon in small bays as a result of excessive pollution. In order to prevent these damages, it will be beneficial in terms of preventing the economic losses of the fisheries. In some cases, undesirable situations can occur when the chemicals used for the treatment of fish are overdosed and the wastes are mixed with water.

        In recent years, successful breeding studies have been started on another yellowtail species Seriola lalandi in New Zealand.
        This fish species, known as king yellowtail, is a species that is valuable for food. It is a fish that can grow up to 1,7 m in natural environment. They can reach up to 50-60 kg. Marketing at a high price, good development rate and reaching a weight of 3 kg in 12-15 months make the breeding of this species attractive.