Niches of dominant fish in the waters surrounding the Taishan Islands, China

An index of relative importance(IRI) was employed to screen for dominant fish in the waters surrounding the Taishan Islands, China, using data from four seasonal trawl surveys undertaken between 2012 and 2013. Niche breadth and niche overlap were measured using the Feinsinger and Morisita-Horn indices, respectively, and the characteristics and seasonal variations in the niches of dominant fish were assessed via non-metric multidimensional scaling(NMDS) and cluster analysis. A total of 80 fish species, including 16 dominant species, were recorded. Only A mblychaeturichthys hexanema was dominant in all seasons. According to niche breadth values and NMDS, the 16 dominant species were grouped into the following three types:(1) wide niche breadth species, including Cynoglossus macrolepidotus, A. hexanema, and Trypauchen vagina, among others;(2) medium niche breadth species, including Setipinna taty and Johnius belangerii; and(3) narrow niche breadth species, including A trobucca nibe and Coilia mystus. Most species with a wider niche breadth were demersal fish with a lower swimming capability and even distribution. The niche breadth of migrating fish was narrower than that of settled fish. At a given spatial scale, fish with stronger swimming capabilities had a narrower niche breadth. Niche overlap, which is associated with niche specialization, ranged from 0.000 to 0.886 and had an annual mean value of 0.314. In summer and autumn, niche overlap was relatively high within species of the Sciaenidae family and within species of the Gobiidae in autumn. Dif ferences in thermophily, feeding habits, food organism abundance/distribution and predator-prey relationships af fected the niche overlap of fish in this area. Cluster analysis revealed that species with the narrowest niche breadth and lowest niche overlap values usually displayed lower aggregation and greater distribution dif ferences compared with other species.

The First Vertebrate Assemblage Dominated by Fishes and Turtles of the Jehol Biota in Jilin Province, NE China

Objective The Early Cretaceous sediments are well-exposed in southern Jilin Province,and yield abundant invertebrate and plant fossils,including the typical EosestheriaEphemeropsis trisetalis-Lycoptera（E-E-L）assemblage of the Jehol Biota（Shao Tiequan et al.,2017）.However,vertebrate fossils,especially tetrapods,are extremely rare and there is no formal documents on these fossils.Recently,a new fossil site dominated by fishes and turtles has been discovered in the middle part of the

Changes in fish diversity and community structure in the central and southern Yellow Sea from 2003 to 2015

The central and southern Yellow Sea is an important overwintering ground for many fish species in the Bohai Sea and Yellow Sea. For better understanding the status of the fish community after years of heavy exploitation, variations in fish community structure and diversity were analyzed using data from bottom trawls during 2003–2015. Five fish assemblage indices all showed fluctuations without clear trends from 2003 to 2015, yet there were strong positive and significant correlations(P < 0.05) among them. The top-five dominant species accounted for a high weight percentage(49.7%–82.1%) in the annual fish catch. Multivariate analysis showed that two year groups could be pooled for the fish community: Group Ⅰ consisted of the years 2006, 2007, 2008 and 2015, while Group Ⅱ consisted of the years 2003, 2004, 2005, 2009, 2010 and 2014; the groups aggregated with 63.71% similarity, indicating a high level of similarity among all years. The multivariate dispersion values were 1.455 and 0.818 for Groups Ⅰ and Ⅱ, respectively, indicating greater variances in fish assemblage structure in Group Ⅰ than that in Group Ⅱ. Similarity of percentage analysis demonstrated that the average similarities for Group Ⅰ and Group Ⅱ were 71.58% and 67.51%, respectively. Size-spectra analysis revealed no consistent trend in the intercept and slope( P > 0.05); there were also no significant differences between the slope of the size-spectra and fishing ef fort. The catch per unit ef fort and mean individual weight analyses of the whole fish assemblage both showed a significantly decreasing trend over time. Overall, the results showed that the fish community structure in the central and southern Yellow Sea was relatively stable from 2003 to 2015 and the study could be used as a reference for supporting ecosystem-based fishery management.