ABSTRACT
Occasional species are often neglected in community ecology studies due to low abundance and frequence. However, they are closely related to biodiversity maintenance and marine conservation. We used index of relative importance (IRI), distribution center of gravity and Mann-Kendall trend test to elucidate the spatial and temporal distributions and changing trends of occasional fishes in Haizhou Bay based on the fishery resources survey data collected from 2013 to 2019. The occasional fishes in Haizhou Bay was identified based on IRI. Nine of the occasional species were selected to analyze the spatial distribution and interannual trends of relative biomass and occurrence frequency. The results showed that a total of 93 fish species were recorded in the multi-year survey in Haizhou Bay. Among which, 61 species had IRI<10, indicating the existence of a large number of occasional fishes in Haizhou Bay. The nine selected occasional species had distinctive spatial distribution characteristics. Erisphex pottii, Azuma emmnion, and Raja porosa were mainly distributed in the eastern part of Haizhou Bay, with a wide habitat range. Sphyraena pinguis, Coilia nasus, and Zebrias zebra were distributed in the western and southern parts, respectively. The rest species were mainly distributed in the southwestern part. In terms of interannual variation, the biomass and occurrence frequency of Coilia mystus, R. porosa, A. emmnion, and S. pinguis showed fluctuating changes, while Odontamblyopus rubicundus and Ctenotrypauchen microcephalus showed an increasing trend. The biomass and occurrence of Z. zebra, C. nasus and E. pottii gradually decreased with no catch in recent years. This study would contribute to the understanding of the spatial and temporal distribution of occasional species, and provide guidance for the conservation of occasional biological resources and species diversity, especially for the establishment of marine protected areas.
Subject(s)
Bays , Perciformes , Animals , Fishes , Ecosystem , ChinaABSTRACT
Based on the data collected from the bottom trawl surveys in the coastal waters of northern Jiangsu Province from 2009 to 2014, multivariate statistical analysis and other integrated indices were used to analyze the variation in the community structure of fish assemblage over time in the waters. The results showed that 68 species had been caught in the coastal waters of northern Jiangsu Province. There were significant fluctuations in the relative density of fish resources. The mean catch mass per site ranged from 0.75 to 1.62 kg·h-1, and the mean catch individuals per site showed significant decrease in the survey period ranging from 370 to 203 ind·h-1. The mean trophic level (MTL) index varied between 3.58 and 3.72 from 2011 to 2014, being relatively low in 2009-2012 and fluctuating around 3.70 in 2011-2014. The mean body mass of fish community increased from 2.93 to 11.18 g between 2009 and 2014, showing a similar tendency with that of MTL index. Cluster analysis and MDS showed that the six survey years could be divided into two subgroups of 2009-2010 and 2011-2014. The main discriminating species were Syngnathus acus,Ctenotrypauchen microcephalus and Ammodytes personatus for the two subgroups. Further study showed that the pelagic and planktivorous fishes had gradually increased in dominance while cold temperate species and indigenous species had decreased over the years. It was suggested that fish communities in the coastal waters of northern Jiangsu Province underwent a remarkable succession. Advices for the fisheries management in the waters were provided according to the succession pattern, which might contribute to the sustainable utilization of fishery resources.
