Study On Bio-resource Monitoring And Assessing Techniquesand Application In Offshore Island Area With Artificial Reefs

Islands are important in the marine economy development in China. Although island area is always small, it has important radiation effect in the development of inland economy. Some islands carry important value of defense, and strategic significance of safeguard national marine rights. Under the pressure of marine habitats damaged, isolated island ecosystem become more fragile, so protection and restoration of its bio-resources are important. World-wide biological resources repairing work, for example, the construction of artificial reefs, has been developing. But due to restrictions of habitat complexity in island area, conventional method for resources monitoring is difficult to work. In this study, we try to develop and apply the video and acoustic investigate techniques in Qiansan Islands area, choosing the habitat, macroalgae community, sea cucumber Apostichopus japonicus and reef fish as the research object.1. Community structure of maroalgae, its seasonal succession and spatial distribution of Sargassum bed(eg. coverage), were studied using echo sounding combining with dive-sampling methods in Qiansan islands. Nineteen macroalgae species including 14 species belonging Rhodoplayta, 3 species belonging Phaeophyta and 2 species belonging Chlorophyta was identified in four diving surveys in 2013. Obvious spatial difference and seasonal succession of macroalgae community was found. Biomass of macroalgae community in the south of island is larger than that in the north of island(p<0.05). Seasonal variation of species and biomass of macroalgae was different. Sargassum sp. is the dominant species in Qiansan Islands, with much larger biomass than other macroalgae, to formation Sargassum bed. In the echo detection test of Sargassum bed, target strength can be distinguished among Sargassum seabed and seawater. Target strength of Sargassum bed was between-55 db ~-75 db. Through the analysis of acoustic data of Sargassum bed, cover, height and other features can be obtained.2. Evaluation model of sea cucumber Apostichopus japonicus was developed using machine vision technology and support vector machine(SVM). Image acquisition platform was designed to get the different body contour image of sea cucumber in free motion. Then, body length, body width, perimeter, area, and other parameters were extracted through image processing. SVM and power model was used to regress characteristics and wet weight of sea cucumber. R2 of the training and test sets and R2 of power model were all reached 0.9. Based on the image processing and modeling algorithms, guide user interface was built to evaluate the wet weight of sea cucumber A. japonicus.3. Stereo-video technique was used in the study of fish population in vessel reef area, and the population change of black rockfish Sebastes schlegeli was surveyed between two years. Underwater stereo-video system was designed, including the underwater video-captured system, and the guide user interface was developed to measure the length of target object in stereo video, with the error in 3.3±2.6%. Total length of black rockfish in vessel reef area were 34.92 ± 5.98 cm and 38.16 ± 5.75 cm in 2012 and 2013, respectively(p<0.05). Echo sounding survey was conducted in May, 2012 and the target strength of Lateolabrax maculatus was-30~-45db; the school density was 3.18×102 inds. per hectare and mainly distributed near Shen reefs.4. Island seabed habitat mapping was conducted; habitat characteristic and bioresource database was built. Elevation data in island area was obtained using multibeam sonar, to build the digital elevation model(DEM). Seabed topography was get from side scan sonar to classify the different geomorphic type, combing the analysis of underwater video. Seabed habitat in Ping Island area include reef area and sandy clay area, and artificial reefs such as stones, concrete structures, and vessel reefs. Qiansan Islands habitat and bio-resource database was built base on geodatabase, to realize the store, integration and visualization of habitat data(eg. elevation, geomorphic type, water quality, sediment deposition) and bio-resource data(eg. population characteristic of sea cucumber, algae and reef fish). It intensify understanding of the bio-resource characteristic and its relationship with habitat.In this study, we integrated monitoring and evaluation techniques, to develop and apply the habitat and bio-resource evaluation techniques in island and artificial reef area. The optional biological resources monitoring techniques in island area was expanded.