Seasonal variations in the diversity and benthic community structure of subtidal artificial oyster reefs adjacent to the Luanhe River Estuary, Bohai Sea.

Artificial oyster reefs provide important spawning and nursery grounds for a variety of fishes and large mobile crustaceans. Between July 2016 and May 2017, seasonal surveys of species composition and community structure were performed in the artificial oyster reef area and control area adjacent to the Luanhe River Estuary in China. During the survey year, 56 species belonging to 50 genera, 45 families, and 19 orders were recorded. The dominant economically important fish and mobile crustaceans were Hexagrammos otakii, Pholis fangi, Sebastes schlegelii, Charybdis japonica, and Oratosquilla oratoria. Resident fishes belonged to the Cynoglossidae, Paralichthyidae, Pleuronectidae, and Gobiidae families. Seasonally important fish species included Lateolabrax japonicus, Konosirus punctatus, Thryssa kammalensis, Hexagrammos agrammus, and Acanthopagrus schlegelii. The ranges of H' values among stations were 1.18-2.16, 0.65-1.75, 1.18-2.06, and 0.62-1.92 in spring, summer, autumn, and winter, respectively. The benthic organisms present in the community of artificial oyster reef areas can be classified into groups according to month and season. The abundance biomass curves showed that the oyster reef area in spring, autumn, and winter experienced low disturbance, whereas the community structure in summer was subject to large variations from external disturbance. We also found that as the age of the oyster reefs increased, the percentage of oysters in the low shell height group (< 40 mm) decreased. The oyster density was 324 ind/m2 for the reef created in 2016, 724 ind/m2 for the reef created in 2015, and 364 ind/m2 for the reef created in 2013. These findings can be used to develop suitable management strategies for the sustainable maintenance of artificial oyster reef ecosystems.

[Resource differences in the populations of Protosalanx chinensis between Dalong Lake and Amuta Lake in Daqing, Northeast China]. / 大庆市大龙湖与阿木塔湖大银鱼种群资源差异.

The population structure of Protosalanx chinensis is affected by a variety of factors, including water environment, intraspecific differentiation, interspecific competition and commercial fishing. To investigate the growth performance and the current status of resource utilization of P. chinensis in two important fish farming grounds (Dalong Lake and Amuta Lake) in Daqing, Northeast China, we collected 1513 P. chinensis samples from April to December 2018 for measurement and recording the basic biological characteristics. We estimated the parameters including population growth, mortality and exploitation using Von Bertalanffy growth formula, Beverton-Holt model, Pauly's empirical formula and length-based Bayesian biomass estimation method. The results showed that the asymptotic body lengths of Dalong Lake (n=660) and Amuta Lake (n=853) populations were 183.75 and 169.10 mm, respectively. The growth performance indices were both 4.85, and the body mass growth equations were Wt=29.29×(1-e-2.1(t+0.07))3.2977 and Wt=28.72×(1-e-2.5(t+0.07))3.4168, respectively. The ages at inflection were 0.49 a and 0.43 a, and the condition factors were 5.30×10-4±1.38×10-4 and 4.00×10-4±1.61×10-4. The exploitation rates were 0.60 and 0.61, and the relative catch per unit of supplementation were 0.069 and 0.075, respectively. The current differences in population resources between Dalong Lake and Amuta Lake in Daqing were mainly manifested in the parameters related to growth characteristics. The main reason for such differences was changes in the survival conditions of P. chinensis populations after the period of dietary transition induced by the density differences.