The Current Situation And Conservation Of Scomberomorus Niphonius In Yellow Sea And Bohai Bay

Scomberomorus niphonius is a perennial warm-temperate upper-layer fish which has the characters of wide distribution, long life-cycle,rapid growth and high economic value. Because of the great depression of other economic fishery resources in Bohai Sea and Yellow Sea, S. niphonius is now the only big economic fishery resource that annual fishery catch is higher than 10×104t. Fishery production is mainly capture of juvenile fish that very year during autumn. The rise of fishery catch from 10×104t to 30×104t in the area around Bohai Sea and Yellow Sea shows that it is the key resource for the sustainable development of fishery in this area. By investigation of 2006~2008 and analysis of historical data, we did some research on the S. niphonius resource character, habitat condition, resource undulation and the reasons, and suggest some effective measures for the conservation of this idioplasm resource.S. niphonius in Bohai Sea and Yellow Sea belong to the same population. The egg-laying crowd is mainly 1 or 2 years old fish, with average age of 2.78, average length and average weight of 1535g. Those fish grow rapidly; the average fork length and weight of 1 year old fish are 419mm and 520g. Joining the spawning crowd, the relationship between fork length and weight can be expressed as W=2.30×10-5L2.8159. The growth equation is Lt=746[1- e-0.4606(t+0.733)] and Wt=3157[1-e-0.4606(t+0.733)]3. The spinodal of growth appears at age of 1.65. The relationship between fork length and weight of juvenile fish of that very year can be expressed asW=8.1399×10-6L3.0038, and the growth equation is Lt=422.84[1-e-0.1388(t-2.18)] and Wt=629.66[1- e-0.1888(t-2.18)]3. The spinodal of weight appears on 11 September. The gonad matures once a year, and the breed circle is 1 year. The ratio between the female and male is 50.2:49.8, and the first sex mature age is 1 year. The smallest fork length is 380mm, the lightest weight is 420g, the average amount of egg is 68×104 and the time for spawning is from April to October. S. niphonius is a kind of fierce carnival fish with relatively simple diet, mainly small-size fishes and small amount of cephalopods and crustacean. The natural death coefficient of adult fish older than 1 year is 0.4112 and for the juvenile fish of that very year is 0.4602. The recruitment population of S. niphonius is mainly the juvenile fish of that every year which occupies 97.27% of the total. Usually the generation recruitments undulate between 1.35×108 and 5.65×108.S. niphonius is a kind of warm-temperate upper-layer fish with long distance of immigrations, wide-distributed in East Sea, Yellow Sea and Bohai Sea. The fishes did long-distance of immigrations during spawning season and winter. The overwinter places are mainly east-north of Yellow Sea, north of East Sea and south of North Sea. In these places the water temperature is normally 14～23℃and salinity is 34～35. The spawning sites in Bohai Sea and Yellow Sea are mainly Haizhou Bay, near-sea of Qingdao and Shidao, Hiayang Island, Laizhou Bay, Bohai Bay, Liaodong Bay and Luanhekou. The spawning temperature is 10～20℃. The parent fish and juvenile fish both feed in the area near the spawning sites and thus wide distributed.After 1998, the fishery catch of S. niphonius undulate between 21.40×104 and 29.72×104t, and in 2005 reached the highest level in the history.Because of the increasing of ocean engineering,costal construction,pollution of ecological environment, shortage of feed and overexploitation, the idioplasm resource of S. niphonius is in continuous great danger .. Because of the importance of S. niphonius in the fishery of Bohai Sea and Yellow Sea, and in order to avoid different threatens and satisfy the social demands, the conservation of S. niphonius idioplasm resources is quite necessary. We suggest construction of S. niphonius idioplasm resource conservation and especially protect the spawning sites, bait-sites and the immigration channels. Around Bohai Sea and Yellow Sea, we should set 8 core-zones for conservation including Liaodong Bay, Luanhekou, west area of Bohai Sea, near-sea of Tantai and Weihai, Haiyang Island, remote sea of Shidao, near sea of Rushan and Haizhou Bay. In addition, we also suggest construction of 2 test-zones including near sea of Bohai Sea and Yellow Sea, and special conservation phase should be decided according of different conditions of every place.