Use Of Different Sampling Tools For Comparison Of Fish-aggregating Effects Along Horizontal Transect At Two Artificial Reef Sites In Shengsi

Fishes and macro-invertebrates were sampled at two artificial reef sites(Dongku and Sanheng artificial reefs) in August of 2014 using sampling tools(Combination of multi-mesh trammel nets, cage, the improved trawl) to find out the horizontal boundaries of fish aggregating effects by deployed artificial reefs(AR) as well as sampling efficiency of the applied sampling tools. We analyzed the catch by three kinds of nets respectively in two ARS, include Species composition, dominant species, abundance, biomass, richness index, diversity index, species similarity index and so on. Compare the trends of these indicators in four sampling stations of AR which equally spaced. We explored the applications in the evaluation of the composition with fish and macro-invertebrates in AR by different kinds of nets. In all, we caught eighty-seven kinds of fish and macro-invertebrates, thirty-nine kinds of fish, twenty-eight kinds of arthropods, sixteen kinds of mollusks, four kinds of echinoderm.The species number of catch from S1 to S4 were 40,29,31,20 successively in Sanheng AR. The station of S1 has maximum value roughly with three different nets in the aspects of abundance and biomass. The fishery resources inside of AR is much more than it outside of the AR obviously. The effect of trapping presents trends that in descending order from the inside out of AR in the horizontal boundaries. The dominant species in three different sampling nets as follows: The dominant species of gillnet were Johnius belengerii, Muraenesox cinereus, Sebastiscus marmoratus, Larimichthys polyactis, Cynoglossus lighti; the dominant species of cage were Cynoglossus lighti and Sebastiscus marmoratus; the dominant species of trawl were Arelicus joyneri, Solenocera crassicornis, Parapenaeopsis acultrirostris. There were the highest richness and diversity index in the sampling station of S1 by three kinds of different nets. The richness and diversity index presents trends that in descending order from the inside out of AR in the horizontal boundaries roughly.The species number of catch from S1 to S4 were 39,45,35,24 successively in Dongku AR. There were the highest abundance and biomass in the sampling station of S2 by three kinds of different nets and there were the smallest biomass in the sampling station of S1. The effect of trapping presents trends that the abundance and biomass in the edge of AR is more than it inside of AR than it outside of the AR in the horizontal boundaries. The dominant species in three different sampling nets as follows: The dominant species of gillnet were Johnius belengerii, Larimichthys polyactis, Arelicus joyneri; the dominant species of cage were Parapenaeopsis acultrirostris and Charybdis japonica; the dominant species of trawl were Palaemon gravieri, Portunus trituberculatus, Parapenaeopsis tenella, Sebastiscus marmoratus and Hemicentrotus pulcherrimus. There were the highest richness and diversity index in the sampling station of S1,S2 and S3 by three kinds of different nets. Overall, the richness and diversity index are more than outside of the AR.Fish are the most abundant species for trammel nets catch. It took 51.1% of the total gillnets catch; Trawls was the most efficiency tool for collection of arthropod, followed by fish, accounting 41% and 37.7% respectively of the total catch. Catch of cages did not show any significant difference on species abundance or biomass between different species types along the selected transects. The species similarity index of gillnet and cage is 0.23, the species similarity index of trawl and cage is 0.4, the species similarity index of gillnet and trawl is 0.18. The species similarity index of trawl and cage is larger than others. Trawls acted as a better tool on species diversity investigation than trammel nets and cages, while the combination those three tools can draw a most complete picture on local species composition status. For the abundance, biomass and diversity indices, both trammel nets and trawls had the highest density and diversity at core area of sampling AR sites, decreasing slowly along the selected four transects. Based on that, we extracted a distance of 200 m as the effective radiation range of in Sanheng AR area while 200-300 m in Dongku AR area. It is concluded firstly that different sampling tool has different advantage on fish and macro-invertebrate evaluation, thus the combination of different tools is needed to reveal the most complete and accurate status of AR aggregating effects. Secondly, the effective range of fish aggregating function by deployed AR could be restricted in a very narrow area less than 1000 m and it is 200-300 m for this study.