제주 해양생물자원의 특성과 가치

Features and Values of Marine Bioresources of Jeju: Reproductive features and use of damselfish, wrasses, groupers, and olive founder

This study examines the application of data on the ecological features of the reproduction of damselfish (Chromis notata), wrasses, groupers including red spotted grouper (Epinephelus akaara), Dageumari (Niphon spinosus Cuvier (i.e. longtooth grouper (E. bruneus)), Gumunjaengi (i.e. seven-band grouper (E. septemfasciatus)), and cultured olive founder (Paralichthys olivaeus), all of which inhabit coastal areas of Jeju (the island off the southern tip of the Korean Peninsula). Damselfish caught in the seas off the coast of Jeju are classified as a summer-spawning species that begin to develop their gonads in May (with lengthening daytime hours and rising water temperatures) and mostly spawn in July. After the male creates the spawning ground, the female lay eggs in rocky or pebbled areas in order for the eggs to remain stationary. The male then releases its sperm over the immobile eggs for fertilization. The reproductive ecology of damselfish is remarkable in that the male guards the spawning ground until the fry finally hatch. Wrasses such as Pteragogus flagellifer, Halichoeres poecilopterus, and Halichoeres tenuispinis feature reproduction that takes place in the summer months much like that of damselfish. Another wrasse called Pseudolabrus sieboldin is an autumn-spawning species that breeds from October to November. Wrasses are known for their sexual characteristic of being protogynous hermaphrodites, which grows as females until their genital organs change into that of a male. Notably, the Pseudolabrus sieboldi has two different types of male: the initial phase male (originally born as male) and the terminal phase male (born as female and later changing into a male). Groupers are found in many areas across the globe, and feature 159 species in total. Of them, 12 species inhabit the Jeju Seas, including the longtooth grouper (E. bruneus), seven-band grouper (E. septemfasciatus), red spotted grouper (E. akaara), and blacktip grouper (E. fasciatus). Like wrasses, groupers are also protogynous hermaphrodites and spawn in the summer. In terms of maturation, after hatching they can become adults in three years at the earliest or in five to seven years at the latest. Naturally, mostly males experience sex reversal from being females. The adaptive features of maturation apply to the aquaculture of red spotted grouper, resulting in the all-year-round production of fertilized eggs and healthier fry that are exported to other countries. Cultured olive flounder (Paralichthys olivaeus) is one of the Jeju’s agri-fishery products that boasts world-class quality, taking up 50% of the national total yield. Jeju has seen a steady growth in the export of cultured olive flounder to Japan, the US, and many Southeast Asian countries. The recent production trend represents the preference of large-sized olive flounder weighing 2㎏. During production, however, most fish undergo the breeding period when they brood (or incubate) matured roe. Fish with decreased immunity and weight loss after brooding result in such problems as an increased mortality rate or diminished commercial value. Since olive founder’s ecological feature is such that they can easily adapt to new aquaculture conditions, this offers a solution to the afore-mentioned problems. A photoperiodic adjustment is adopted to create a time of diapause of developing gonads, which leads to no roe incubation and helps culture healthier fish.