[Biological characteristics, temporal-spatial distribution of Portunus trituberculatus and relationships between its density and impact factors in Laizhou Bay, Bohai Sea, China.] / èŽ±å·žæ¹¾ä¸‰ç–£æ¢­å­èŸ¹çš„ç”Ÿç‰©å­¦ç‰¹å¾ã€æ—¶ç©ºåˆ†å¸ƒåŠçŽ¯å¢ƒå› å­çš„å½±å“.

Biological characteristics, density and its spatial distribution of Portunus trituberculatus in Laizhou Bay, together with the impact of environmental factors, were analyzed based on the bottom trawl data of 9 surveys from May 2011 to April 2012, in order to provide scientific basis for utilizing and protecting the resource of P. trituberculatus. The monthly variation of biomass density could be described as September > October > July > August > June > November > March > May > April. The average values were highest in August 2011 and lowest in April 2012, for body mass, width and length, respectively. The individual fatness coefficient was highest in August 2011 both for the female (1.030) and the male (1.023), lowest in July both for the female (1.007) and the male (1.007). The difference of fatness coefficient was not significant (P>0.05) between the female and the male. The sex ratio (female/male) was less than 1.0 in most of all months except June, July and August. P. trituberculatus was mainly distributed in the Yellow River estuary and the offshore off Longkou in May-July, in offshore off Weifang and Longkou in August-September, and in deep-water area of the Laizhou Bay mouth from October to next April. Pearson correlation analysis indicated that environmental factors that best matched the density of P. trituberculatus were sea surface temperature (SST), dissolved oxygen (DO) and water depth (Dep), followed by salinity (Sal) and zooplankton density, the last were phytoplankton density and the number of other demersal fisheries species. The body length of P. trituberculatus in 2011 was significantly smaller (P<0.01) compared with that in 1981. To sustainably utilize the resource of P. trituberculatus in Laizhou Bay, we suggested that the fishing effort should be reduced, the catchable size should be raised, the research of enhancement basements should be promoted and more reasonable releasing quantity should be proposed.

[Ecological carrying capacity of Chinese shrimp stock enhancement in Laizhou Bay of East China based on Ecopath model].

Stock enhancement is an important way of fishery resources conservation, which can increase the high quality fishery resources and improve the fish population structure. The study of ecological carrying capacity is the premise for the scientific implementation of stock enhancement. Based on the survey data of the fishery resources and ecological environment in Laizhou Bay from 2009 to 2010, an Ecopath mass-balance model of the Laizhou Bay ecosystem consisted of 26 functional groups was constructed, and applied to analyze the overall characteristics of the ecosystem, the trophic interrelationships, and the keystone species, and to calculate the ecological carrying capacity of Chinese shrimp enhancement. As for the overall characteristics of the ecosystem, the total primary production/total respiration (TPP/TR) was 1. 53, total primary production/total biomass (TPP/B) was 24.54, Finn' s cycling index was lower (0.07), surplus production was higher (434. 41 t km-2 a-1 ), and system connectance index was lower (0. 29), indicating that this ecosystem was at an early development stage. The analysis on the keystone species showed that Chinese shrimp was not a keystone species of this ecosystem. At present, the biomass of Chinese shrimp in the ecosystem was 0. 1143 t km-2, with a greater potential of continued enhancement. It did not exceed the ecological carrying capacity of 2. 9489 t km-2 when the biomass of the Chinese shrimp was increased by 25. 8 times.

[Ecological niche breadth and niche overlap of dominant species of fish assemblage in Yangtze river estuary and its adjacent waters].

Based on the fishery resources data from the bottom trawl surveys conducted on the R/V Beidou in the Yangtze River estuary and its adjacent waters in June, August and October of 2006, the index of relative importance (IRI) was measured to determine the dominant species of fish assemblage, and the niche indicators and their seasonal variations of the dominant species were analyzed. A total of 10 dominant species in the 3 survey cruises were recorded, which were divided into two groups by the Bray-curtis similarity clustering and non-metric multidimensional scaling (MDS) analysis, with a significant seasonal variation of niche breadth and niche overlap. One group included Engraulis japonicus, Champsodon capensis, and Acropoma japonicum, whose niche breadth and niche overlap were larger in summer than in autumn, with a migration from the Yangtze River estuary and its adjacent waters to outer deeper waters, while the other group included Trichiurus haumela, Chaeturichthys stigmatias, Apogon lineatus, Larimichthys polyactis, Psenopsis anomala, Argyrosomus argentatus, and Benthosema pterotum, whose niche breadth and niche overlap were larger in autumn than in summer, with a reverse migration from southern Yellow Sea and northern East China Sea to the Yangtze River estuary and its adjacent waters. The different migration direction of the two groups was related to their ecological habits and environmental factors.

[Effects of macro-jellyfish abundance dynamics on fishery resource structure in the Yangtze River estuary and its adjacent waters].

Based on the bottom trawl survey data in May 2007 and May and June 2008, this paper analyzed the effects of the abundance dynamics of macro-jellyfish on the species composition, distribution, and abundance of fishery resource in the Yangtze River estuary and its adjacent waters. From May 2007 to June 2008, the average catch per haul and the top catch per haul of macro-jellyfish increased, up to 222.2 kg x h(-1) and 1800 kg x h(-1) in June 2008, respectively. The macro-jellyfish were mainly distributed in the areas around 50 m isobath, and not beyond 100 m isobath where was the joint front of the coastal waters of East China Sea, Yangtze River runoff, and Taiwan Warm Current. The main distribution area of macro-jellyfish in June migrated northward, as compared with that in May, and the highest catches of macro-jellyfish in May 2007 and May 2008 were found in the same sampling station (122.5 degrees E, 28.5 degrees N). In the sampling stations with higher abundance of macro-jellyfish, the fishery abundance was low, and the fishery species also changed greatly, mainly composed by small-sized species (Trachurus japonicus, Harpadon nehereus, and Acropoma japonicum) and pelagic species (Psenopsis anomala, Octopus variabilis) and Trichiurus japonicus, and P. anomala accounted for 23.7% of the total catch in June 2008. Larimichthys polyactis also occupied higher proportion of the total catch in sampling stations with higher macro-jellyfish abundance, but the demersal species Lophius litulon was not found, and a few crustaceans were collected. This study showed that macro-jellyfish had definite negative effects on the fishery community structure and abundance in the Yangtze River estuary fishery ecosystem, and further, changed the energy flow patterns of the ecosystem through cascading trophic interactions. Therefore, macro-jellyfish was strongly suggested to be an independent ecological group when the corresponding fishery management measures were considered.

[Feeding habits of Trichiurus lepturus in Beibu Gulf of South China Sea].

From August 2008 to September 2009, the feeding habits of Trichurus lepturus L. in Beibu Gulf of South China Sea were studied by monthly sampling and stomach content analysis. In study area, T. lepturus was euryphagous, which fed on fish, cephalopoda, benthic crustacean, and zooplankton, etc., among which, Bregmaceros rarisquamosu, Decapterus maruadsi, and Acetes chinensis were the main prey components, accounting for 37.99%, 16.42%, and 10.03%, respectively. D. maruadsi and Anchoviella heteroloba appeared throughout the Beibu Gulf all year round, and could be served as the index species for the migration and fishing ground distribution of T. lepturus. The indices feeding intensity and stomach fullness differed significantly among seasons (P < 0.001); while the index prey diversity had no significant seasonal difference (P > 0.05), which peaked in autumn and had an annual average value of 1.97. Cluster analysis revealed that when the preanal length of T. lepturus was 190 mm, i. e., at 50% of maturity length, a clear diet shift happened, from small zooplankton, pelagic fishes, and crustacean for the juveniles to predominantly larger fish and cephalopoda for the adults.

[Functional groups of high trophic level communities in adjacent waters of Changjiang estuary].

Based on the three bottom trawl surveys in adjacent waters of Changjiang estuary in June, August and October 2006, the composition and variation of the functional groups of high trophic level communities in the waters were studied. According to diet analysis, the high trophic level communities in the waters included six functional groups, i.e., piscivore, shrimp predator, crab predator, benthivore, planktivore, and generalist predator. Due to the variation of marine environment and fish migration behavior, the composition and trophic level of the high trophic level communities had greater monthly change. In June, fishes, acetes, and crabs dominated the communities, and planktivore was the major functional group, with its trophic level being the lowest (3.06); in August, fishes were dominant, and shrimp predator was the major functional group, with its trophic level being the highest (3.78); and in October, fishes also dominated the communities, the proportion of shrimp and crab increased, and planktivore and benthivore were the major functional groups, with a trophic level of 3.58.

Late Pleistocene divergence and subsequent population expansion of two closely related fish species, Japanese anchovy (Engraulis japonicus) and Australian anchovy (Engraulis australis).

Climatic oscillations during the Pleistocene ice ages produced great changes in species' geographical distribution and abundance, which could be expected to have genetic consequences. Living in the temperate upwelling zones of the northwestern Pacific, Japanese anchovy (Engraulis japonicus) might have been affected by these severe climatic oscillations. To investigate the effects of Pleistocene climatic changes on the evolution in Japanese anchovy, fragments of 522 bp at the 5' end of mitochondrial DNA control region were sequenced for 241 individuals from 13 localities and 37 individuals of Australian anchovy. Japanese anchovy and Australian anchovy are reciprocally monophyletic and a late Pleistocene transequatorial divergence between the two species was indicated. High levels of haplotype diversity (>0.99) were found for all samples, indicating a high level of genetic diversity. Analyses of molecular variance and the conventional population statistic F(ST) revealed no significant genetic structure throughout the range of Japanese anchovy. Both mismatch distribution analyses and neutrality tests suggested a late Pleistocene population expansion for both Japanese anchovy (79,000-317,000 years ago) and Australian anchovy (45,000-178,000 years ago).