Resource And Biological Characteristics Of Large Yellow Croaker(Larimichthys Crocea) In Guanjing Yang

The results showed that overfishing due to great capture capacity and intensionled to the stock decline since1970s. There has no fishing season of large yellowcroaker in the main fishing ground because of the excess capture to the mid-1980s.Though many measures carried by fishery department to protect the stock, the largeyellow croakers are still listed in the species whose stock declined seriously.At thesame time, the large yellow croaker were in a typical state of over-fishing withphenomenon of miniaturization, low age and sexual maturity in advance appear incatches.In the background of urgent need to restore the resources of large yellow croaker,The research on the resources of large yellow croaker groups, spawning grounds, andbiological characteristics provide the basis for the resource management andconservation measures of the large yellow croaker. Based on the data from designatedfishery resource survey in Sansha bay from June2010to May2011, routinemonitoring survey and history.The fishery resources in Sansha combined with the utilization and existingsituation of the large yellow croaker were studied, the results show that163specieswere identified, of which were7Undetermined species （identified to the genus）,Belonging to13orders,58families113genera, warm water fish are the dominant fish.The large yellow croaker is the main dominant species of the fishery resources inSansha bay. The large yellow croaker store was low from March to April, asubstantially increased with it into the spawning period, and reach the maximumamount in June. The stock declined since then, and has a small upward trend inOctober. The large yellow croaker store in Sansha bay had an roughly estimated100ton, which far less than200ton in2001.The result showed that the flow of water and the local topography served as themain factors, while the pollution, nutrient salt composition and the abundance of baitare the secondary factors. Two reproductive peaks of large yellow croaker were foundat Guanjingyang, the main one is in spring and summer （May to June） and the other in autumn. The core spawning ground of large yellow croaker ranged fromJigongMountain to the north area of QingshanIsland but not the place the high densityarea of large yellow croaker eggs appeared. The reason for such a phenomenon couldbe attributed to the tide. Meantime, due to the different time effected by the tide, thedistribution of large yellow croaker eggs and larvae showed significant difference. Torecuperate the large yellow croaker’s spawning ground, the protection of large yellowcroaker resource and the spawning environment is suggested.The results indicate that the average body length is132.6mm，with the group ofpredominant body length110-150mm, accounting for55.96%; the average bodyweight is45.1g，with the group of dominant weight10-50g, representing61.77%.The juvenile large yellow croaker and recruit population have been the main catchtargets. The relationship between length and weight was expressed as:W=2.001×10^-5L.^3.006. The growth parameters of von Bertalanffy formula estimated byELEFAN were L_∞=385.4mm, k=0.43and t₀=-0.32a, respectively, and flexion age is2.2years. Compared with the data obtained about large yellow croaker in Fujian，value of L_∞has declined from555.4to the current385.4，flexion age from2.97to2.2，all these trends show that the group has been in serious status characterized withminiaturization and lower age. In addition, the growth coefficient shows an apparentincrease from0.36to0.43，which indicates a speed-up growth in large yellow croaker.Total death coefficient （Z）, natural death coefficient （M） and the coefficient of fishingdeath （F） are3.12,0.45and2.67respectively; the exploit rate in recent years was0.856. The increasing trend of M value may be related to the deterioration of marineenvironment in coastal areas of Fujian; and, due to the high-strength catch of largeyellow croaker, fishing death of such species is increasing sharply, from0.84to2.67,which indicates that the stock of Large yellow croaker has been over exploited.Under the current resource status in Guanjingyang sea, great effort should begiven to reduce fishing mortality and protect its environment so as to protect largeyellow croaker. And due to the miniaturization and low age of large yellow croakerresource, controlling the catchable age （t₀） is suggested to be the main management.