Abalone taxonomy puts them in the family Haliotidae, which contains only one genus, Haliotis, which once contained six subgenera. These subgenera have become alternate representations of Haliotis (Gofas, 2014). The number of species recognized worldwide about 130 (Cox, 1962; Geiger and Owen, 2012). There are currently 2 and 2 subspecies of Haliotis and 2 subspecies of Sulculus (Sulculus diversicolor diversicolor, Sulculus diversicolor supertexta, Haliotis madaka, Haliotis gigantea, Haliotis discus discus, Haliotis discus hannai) (Lee et al., 2014; Lee and Min, 2002; Min et al., 2004). Among them, Haliotis discus hannai and Haliotis discus discus has been recognized as a high value-added aquaculture product in Korea, China, and Japan. Production of abalone is increasing continuously. Both species are classified as different species but belong to the same genus. In Korea, 12,343 tons of farmed abalone were produced in 2016, making it the world''s second largest producer (Kim et al., 2006; KMI, 2017). However, the construction of a mass production system using the marine edging method (Park and Kim., 2013) has a disadvantage. The deterioration of the fishery environment progresses due to factors such as exposure to marine environmental conditions, such as a rapid increase in water temperature, and interference with seawater flow due to high density of aquaculture facilities. As a result, problems such as increased mortality and decreased productivity were identified (Kim, 2014).
Haliotis discus hannai has an oval shell, thick and hard, with a dark brown or greenish brown color. The beginning of the shell is raised high, and the back of the shell is swollen. The chimney of the breathing hole is low and most of them are aligned with four. The habitat is between aquatic reefs at a depth of 20 M on the rocky coast. Haliotis discus hannai is a species of cold sea, and it is possible to produce seedlings. Individuals produced for aquaculture on the southern coast, including Jeju Island, have a gentle shell, similar to the shape of Haliotis discus discus. (Lee et al., 2014)
Haliotis discus discus has an oval shell and is thick. The color is dark brown or reddish brown, and the height of the shell is low. There are 4 ~ 5 breathing holes, and the slope of the side of the shell is steep and the area is wide. Haliotis discus discus has a relatively large number of breathing balls compared to the same size Haliotis madaka. The main habitat is about 20 m deep on the rocky coast, similar to the Haliotis discus hannai, but is a species that prefers temperate waters (Min et al., 2015). Bordering the isotherm at a water temperature of 12 m at a depth of 25 m, the Haliotis discus hannai inhabit cold sea water in the north and the Haliotis discus discus inhabiting warm sea water in the south. Morphological similarity between the H. discus hannai, and the H. s discus discus was studied among the four abalones inhabiting the coast of Korea (You, 2000; Won et al., 2014). In the study of molecular biological characteristics and RNA expression of H. s discus discus, changes in thermal stress and copper metal exposure were observed, and the relationship with environmental stress was also studied through changes in Novel omega glutathione S-transferases (Kim. et al., 2007; Wan. et al., 2009). Research using H. s discus discus is less than research using H. discus hannai .
At the farming site, the boundary between obedience and hybrids is unclear because the mothers are separated and crossed with only morphological features without the exact process of discriminating between the Haliotis discus hannai and Haliotis discus discus. Due to this distinction of species, hybrids are being produced in large quantities. Therefore, an accurate method of discriminating abalone species is required and systematic management of abalone is required. Since abalone is fertilized in vitro, cross-fertilization for each breed can be easily carried out compared to other species, and when hybrid strains appear due to fertilization of two different varieties, there is a possibility of obtaining offspring with excellent growth and survival characteristics (Zhang et al., 2004).
The purpose of the present study was the difference according to temperature and ammonia concentration for the hybrid effect in species due to fertilization of Haliotis discus hannai and Haliotis discus hannai X Haliotis discus discus with different biological characteristics. On the basis of these results, progress was made to identify superior trait progeny.