Nursery habits of marine fish

Some species of sea bream and sea catfish in the ocean also carry eggs in their mouths to nurse them. The male fish usually takes care of the young of the guinea bream, and the eggs are also held by the female fish. The eggs of these fish have filamentous protrusions on the egg membrane and are tightly clustered with each other. Sea catfish has a large mouth with large mouth and protruding sides, which can adapt to holding eggs and hatching. The male fish holds the fertilized eggs in his mouth to hatch them, and the incubation period is about 70 days. Not only can the young fish fully grow up in the mouth of the male parent fish, but they can also separate from the male parent fish after they are capable of self-defense. Generally, young fish do not start living freely until the hard spines of the dorsal and pectoral fins grow into hard spines and the body is 5-10 cm long. Male sea catfish do not eat during the entire reproductive and incubation period. This habit of raising young is very difficult.

Roundfin fish usually spawn in rock crevices above the low tide line in spring, with about 80,000 to 140,000 eggs packed into one large piece. At low tide, the eggs are often exposed on the water and are easily eaten by seabirds and rats. At high tide, they can be eaten by various fish. In this case, the male broodstock can complete the task of protecting the eggs, which is a very difficult job. In fact, during the few weeks of egg hatching, the male fish is devoted wholeheartedly to protecting the eggs, never leaving his post, and often thrust his head into the egg mass so that water can be injected into the central part of the egg mass, and at the same time, Use your mouth to blow the water up, or use your pectoral fins to help splash the water, so that all eggs can receive sufficient oxygen. If there are other animals such as crabs, starfish and shellfish approaching the egg mass, it will remove them one by one. For ferocious enemies, no matter how big or small, it will fight them desperately. During the supervision period, some male fish were attacked by rooks or eagles, and their sharp beaks pierced the abdominal wall, and even had their internal organs eaten. However, as long as they survived, the male fish would not leave their posts. If the male fish leaves the egg mass due to something, the time will be very short. When encountering strong winds and rains, if the egg masses are thrown high on the shore, as soon as the sea calms down, the male fish will try their best to look for them everywhere.

For the golden trout fish, which lives on the coast of shallow seas and is only 25 centimeters long, the male and female parent fish work together to assemble the eggs into spherical egg masses. After that, the female fish uses her long and flat body to surround the egg mass ball with her body and protect it. Sometimes the egg masses are placed in empty oyster shells, or in rock gaps created by perforated shells, with the parent fish nearby guarding them.

In Indo-Pacific hookfish, the male fish has a bony hook-shaped protrusion on its forehead. This protrusion is a special protrusion on the top of the skull. The egg mass is divided into two balls, which are connected by a fibrous substance and hung on hook-like protrusions. When the male fish swims, the two egg masses are like two small balls hanging on both sides of the body.

There is a brood sac on the ventral surface of the tail of Yangzhiyu (sea dragon) and seahorse male fish. During reproduction, the walls of the cyst become thickened and densely packed with blood vessels. When the male and female fish entwine and embrace each other, the female's reproductive process penetrates into a small hole at the front end of the male's brood sac, and the eggs are transferred into the sac. After a series of twists, the male fish moves the eggs to the rear of the brood sac. This action is repeated until the brood sac is filled with eggs. At this time, the male fish appears very tired and needs to take a temporary rest. The male fish supplies nutrients to the egg and embryo through the blood vessels in the brood sac wall until hatching.

Afterwards, the larvae remain in the bag for a normal period of time before being released. Even if you can swim freely in the water, you still have to retreat to your pocket if you encounter danger. The Yangzhi fish uses the downward movement of its tail to open its sac, and the larvae can swim out smoothly one after another. When the larvae want to escape into the sac, the poplar fish bends its body upward into an arc, so that the larvae can quickly escape into the sac, and the parent fish immediately closes the entrance cover. The seahorse's sac opening is relatively small, and it is much more difficult for the young fish to get out of the brood sac than that of the poplar fish. There are only 5 or 6 fish at a time, and it takes several hours for all of them to come out. After the young fish emerge from the pouch, they cannot return to the pouch, so the juvenile seahorses stay in the brood pouch longer than those of the poplar fish.

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