Preliminary Analysis Of Fishery Resource Structure And Health Assessment Of Fishery Ecosystem In The Laizhou Bay And Yellow River Estuary

In recent years, with increasing effects of human activities (overfishing) andenvironmentalchanges(pollution, habitat degradation) on marine ecosystem, combined withclimate change, the fishery resource structure has beenchanged dramatically, characterized byunsustainability. In order to better understand the succession of the fishery resources structure incoastal waters, based on the seasonal survey of the Laizhou Bay and Yellow River estuary during2011-2012and historical data from1959to2008, the seasonal diversity of fish species andinterannual changes of the fishery resource structure in the Laizhou Bay and Yellow River estuarywere analyzed,as well as the preliminary assessment of the fishery ecosystem health. The mainresultswere as follows:Seasonal variations in fish community structure in the Laizhou Bay and Yellow Riverestuary：A total62fish species were caught during2011-2012, belonging to11orders and34families, which mainly comprised warm water and warm temperate species. The Perciformes werethe most abundant (37species), followed by the Scorpaeniformes (7species) andPleuronectiformes (6species). In terms of the total catch per haul (kg) and the number per haul,warm temperate species were the most abundant, followed by warm water species and coldtemperate species. The warm temperate species catches were highest in spring in coastal region,whereas warm water and warm temperate species catches were higher in summer and autumn,which were mostly distributed in the northeast Laizhou Bay deep-water area. Warm temperatespecies were widely distributed in summer and warm water species were mostly distributed incoastal region of southern Laizhou Bay. The dominant species in spring were mainly composed ofnon-commercial demersal fish, Chaeturichthys stigmatias, Callionymus beniteguri, Synechogobiushasta, and Enedrias fangi, accounted for66.4%of the total catch. The dominant species insummer also mainly comprised by non-commercial demersal fish species,C. stigmatias and C.beniteguri, accounted for44.6%of the total catch. While in autumn, the dominant species weremainly composed of pelagic fish, Engraulis japonicus, Sardinella zunasi, and Konosirus punctatus,accounted for40.8%of the total catch. According to the dominance curve, the dominant specieswere most prominent in summer, autumn, and spring in that order. The catch per haul exhibitedsignificant seasonal variation, being highest in autumn (22.63kg/h), followed by summer(16.75kg/h) and spring (1.29kg/h). The average catch per haul of the dominant species in spring(May) was0.69kg/h, which is only0.3%,0.3%,1.7%, and541.2%of the surveys in the spring (May) of1959,2003,2006and2008, respectively. Despite the small increase in fish resources, theoverall trend shows a substantial decrease. Species composition exhibited higher similarities inadjacent months, i.e. each month of the same season and the months of summer and autumn. Thenumber of fish species and abundance and diversity indices were all highest in summer, followedby autumn and spring. However, the evenness index calculated by number was highest in summerand lowest in spring, this trend was inversed when the index was calculated by weight. Thespecies abundance and diversity indices were significantly correlated with sea surface temperature(P<0.01). The species abundance index and evenness index were significantly correlated with seasurface salinity (P<0.01).Interannual variations in fishery resourcestructure in the Laizhou Bay and Yellow Riverestuary：During1959-2011, the number of fishery and fish species both reached the highest valuesin1998, were63and52, respectively. The number of fishery and fish species reduced with theaverage rates of1.15and1.22species per year during1982-2008, reduced to32and19in2008,respectively, and increased to52and29in2011, respectively. The fish community was dominatedby the large-sized, high valued, higher trophic levels and demersal species in1959; and thencharacterized by pelagic fish and bottom fish with lower trophic level from1982to2008;somelarge sized, commercial species were the dominant species in2008,and then replaced by bottomfish with low commerical value in2011, such as Chaeturichthys stigmatias,Synechogobius hastaand Callionymus beniteguri. The fishery invertebrate were mainly composed of Oratosquillaoratoria and Fenneropenaeus chinensis in1959, andLoligo beka Sasaki, Portunus trituberculatusand Portunus trituberculatus in1982and1993, in addition, the resources of crangon affinis andPalaemon gravieri greatly increased since2008. The catch per haul of fishery resources inLaizhou Bay and the Yellow River estuary declined from423.6kg/h in1959to4.7kg/hin1998inspring, and were1.9-7.2kg/h during2003-2011, reached to the lowest value in2008(0.5kg/h).The catch of demersal fish accounted for99.4%of total catch in1959, and25.2%in1982, and6.0%-20.2%from1993to2011. The proportion of pelagic fish catch in the total catch increasedfrom70.6%in1982to82.3%in1993, and40.1%-63.2%during1998-2006. The jellyfishdominated in the total catch in2008, the catch of crustaceans, demersal fish, cephalopods andpelagic fish accounted for74.9%,20.2%,2.6%and2.3%in the total catch in2011, respectively.The diversity indices calculated by weight increased from0.84in1959to1.90in1982,decreasedto1.71in1993, changed around2during1998-2011. The evenness index showed an increasingtrend during1959-2008, and decreased to0.56in2011.The health assessment of fishery ecosystem in the Laizhou Bay and Yellow Riverestuary:The fishery ecosystem health decreased significantly in the Laizhou Bay and YellowRiver estuary from1993to2004, the health assessment value of the fishery ecosystem was only0.19in2004, just50.1%of that in1993, and showed a slightly fluctuating increase from2004to2011, e.g. the health assessment value increased from2004to2006, and decreased to0.18in 2008, then increased to0.26in2011, reached to77.9%of that in1998. According to thepreliminary analysis of the health assessment of the fishery ecosystem, the health of the fisheryecosystem slightly improved in the Laizhou Bay and Yellow River estuary since2004.