Fishing Efficiency Of White-spotted Conger Longline Fishing Gear In Shandong Coastal Sea

After the gear selectivity was proposed by Fulton in1983, it was widely used in all kinds of fishing gear selectivity, which has been brought to the attention of the relevant departments. Our fishery resources has been shown a trend of miniaturization and younger age, and the coastal fishery resources almost being used exhausted, therefore, it is necessary to take strong measures to protect fishery resources. A series of selective research, including trawls, gill nets, trap cage and longline, have been carried out in home and abroad, and these studies benefit for the protection and utilization of fishery resources. Comparing with the abroad, the selective research get a late start, hence it’s less mature research, and the major selective study focused on the trawl and trap cage and so on these large-scale traditional nets, and the study on longline selectivity has not been reported yet.Longline fishery for white-spotted conger(Conger myriaster) is an important fishery in Shandong coastal sea. As an important economic species, it is important to carry out a more detailed study of the conger longline to study its selectivity and establish management. Surrounding to protect the resources of white-spotted conger, this article focused on the biological characteristics and status of fishery resources, the method of analyzing the gear and the research status, size selectivity of conger logline in Shandong coastal sea, the preliminary study of the growth characteristics of the conger and the management of the conger resource, respectively. This paper is consisted of six chapters according to the theories and experiments. The first and second chapters mainly focus on the biology, research method and the research status of white-spotted conger. The third chapter described the selectivity of conger longline experiment in Shandong coastal sea. In the fourth chapter the study of conger growth characters was described. The fifth chapter is about the economic benefit analysis and the management measure. The last chapter draws the conclusion and suggestion.In the third chapter, the author preliminary studied the growth characteristics of the conger, using the latest software which analysis the body length frequency data called FiSAT II to discuss the conger in Rizhao, then estimated the parameters for the Von Bertalanffy growth curve:=713 mm,=-0.18, k=0.38. After calculate, the growth inflexion is3.12, and the conger will be maturity when it’s about3ages at the earliest, but in the experiment the catches almost about1age.so it’s necessary to start the study in order to protect the younger conger meantime to maintain the sustainable development.In the fourth chapter, we denoted two methods to estimate the selectivity. One was the total length selection curve, and the other one was the master curve selectivity. The total length of white-spotted conger caught ranged from247mm to552mm, and mainly distributed in the range of380mm to440mm, which accounted for71%. In the conger longline the commonly used the303had the maximum CPUE among the three hooks in the trial. The optimal lengths are398.07mm,417.81mm and373.89mm. The303type hook has the largest optimal length, and slowest downward trends of selectivity, so the selectivity of hook303is high in the capture of the larger fish in the experiment. But fishes that total length below350mm still make up a large proportion in the catches. So the303is not the best choice in the actual fishing operations, and longline for conger need more research.In the fifth chapter, the author counted the production of the conger longline in Rizhao, which finding that the production drawdown around22.86%from the year2010to2012. The price is very high due to the short supply, and during the3months of longline production each boat can make a profit about20-30thousand yuan. But there was little management about the longline boat, and it is different to manage and a lot of security issue appeared, so we should We should enhance safety consciousness on one hand, on the other hand, strengthen supervision to ensure the safety of fishermen.In the last chapter, the author draws the conclusion of the paper and gives some suggestions to future research.