- One of the concepts put into use is the ecological - connectivity. - The objectives of the thesis. - Provide data on fishery resource exploitation status and their characteristics, and ecological – connectivity of important fishery resource, this is the basis for proposing fishery management solutions in the coastal of Quang Nam - Da Nang.. - The contents of the thesis. - 3 - Ecological – connectivity of the orange-spotted spinefoot (Siganus guttatus) in coastal habitats.. - The significance of the thesis. - To provide data on fish resources, propose solutions to improve the management effectition and utilization of fish resources in the coastal ecosystems of Quang Nam-Da nang.. - NEW FINDINGS OF THE THESIS. - Specifically, this is the first study to discover and examine the ecological connectivity of the orange-spotted spinefoot (Siganus guttatus) in different ecosystems through outlining the life cycle of the fish from juvenile to adult. - Accordingly, the seed stock in the Thu Bon estuary and the adult species in the coral reefs of Da Nang and Cu Lao Cham belong to the same population.This is the scientific basis for proposing ecosystem- based solutions for fisheries management.. - It is the first study to propose ecosystem-based solutions for fisheries management in the coastal areas of Quang Nam-Da Nang.. - Fisheries studies in the world. - Fisheries studies in the world mainly focus on the current status of fishing, including the following main directions: (1) Quantification of fish yield ( 2) Main resource species groups, (3) Fish biology (4) Fisheries management.. - One of the key sources of data for this approach is the understanding of the life cycle linkages of fisheries resource in the ecosystems.. - An integrated assessment of the resources, the situation of fishing in different marine areas and the list of fish species in Vietnam's.. - of the areas, there are no studies on resource characteristics and ecological – connectivity.. - Time of the stydy. - Synthesized from the study of the authors.. - Buiding the fish species list from two material sources: from secondary sources and from the results of additional research on the fish species of the thesis.. - "Survey coastal resources with the participation of the community". - Fish seed collection in the Danang Bay, Thu Bon estuary are of the species Serranidae, Lutjanidae and Siganidae.. - The ecological characteristics of the Danang coastal zone are soft bays, the presence of coral reef and seagrass habitats making the bay highly ecologically diverse.. - The results of size survey showed that fish fingerlings exploited in the coastal reefs of Da Nang have different length depending on the species ranging from 44-148 mm. - Cu Lao Cham. - Da Nang . - Cu Lao Cham . - It can be said that the Cu Lao Cham sea area is directly affected by the sea with coral reefs being the most important habitat creating the ecological characteristics of the whole sea, which determines the biology community in this area.. - Combining the fish species of the additional surveys and species lists of the published authors noted the composition of the Cu Lao Cham fish species including 452 species of 178 genera, 66 families and 15 orders.. - Estimated yield and revenue of the six main fish resource groups in Cu Lao Cham are shown in Table 3.6.. - Sample 96 individual of fish species related to coral reefs from fish catching sites to assess the size of the harvest (Figure 3.2).. - Length of grouper species are generally concentrated in the small group of species, some of the larger species are also of medium size undifferentiated species such as Epinephelus awoara, E. - Rabitfish are medium in size over 175mm, relatively smaller than the average common size of the species (200mm). - Thu Bon estuary. - Mangrove are the speciality habitats of the Thu Bon estuary, with the dominant mangroves tree being Nippa fructicans of the Palmae palm family.. - The total area currently distributed in the Thu Bon estuary is over 80 ha.. - The seagrass of the Thu Bon estuary are distributed mainly in Cam Thanh commune and there are only two species: Halophila beccarii and Zostera japonica. - Zostera japonica is the most important, occupying most of the dunes. - Mangroves are the most important habitat in the Thu Bon estuary. - The presence of seagrass adds to the richness of the estuarine ecosystem. - Characteristics of seagrass in the Thu Bon estuary is characterized by very high seasonal fluctuations. - Combining the fish species of the additional surveys and the species list of the published authors recorded the composition of the fish species in the Thu Bon estuary including 182 species of 110 genera, 55 families and 15 orders ( The thesis has added 70 species belonging to 57 genera, 37 families and 12 orders).. - Estimated yield and revenue of the six main fish resource groups in Thu Bon estuary are shown in Table 3.8.. - Five species belong to four families in the Perciformes family have been identified as the main source of fish seed harvested in Thu Bon estuary (Table 3.9). - Composed of fish species in the above three ecosystems, including 747 species of 318 genera, 106 families, 20 orders. - Compared to the total number of fish species in the three area, Cu Lao Cham has the most diverse species, with 452 species (60.5% of total species). - The Bray-Curtis similarity index of species composition in the three areas shows that the Da Nang and Cu Lao Cham have the highest similarity of 44.2%, followed by Thu Bon and Da Nang by 36.2%, Thu Bon and Cu Lao Cham are lowest at only 15.8%. - Group analysis shows that the species composition of the three areas formed into two groups: Cu Lao Cham and Da Nang, Thu Bon formed a separate group.. - Analysis of the Sorensen homology index (1948) also showed that the level of closeness in species composition in Da Nang and Cu Lao Cham was the highest at 44.2%. - The habitat adaptability in the three areas is also markedly different among fish groups, the composition of the fish species in Cu Lao Cham, Da Nang and Thu Bon shows the habitat adaptability. - It can be said that habitat adaptation is seen in the group of fish that are closely associated with the dominant reef in Cu Lao Cham, Da Nang, and bottom fish and coastal fish dominate the Thu Bon estuary.. - A list of main resource groups in the three coastal areas of Quang Nam- Da Nang was compiled (Table 3.10).. - The main resource groups in the three study areas. - Pos Cu Lao Cham Thu Bon Da Nang. - There is a similarity in the main resource composition between the two areas of Da Nang and Cu Lao Cham: two areas have four in six 6 groups of fish is the same, they are: Trichiurus lepturus, Muraenesox bagio, Siganidae and Scombridae. - It can be said that species diversity is related to the diversity of habitats, but the nature of the resources depends on ecosystem characteristics.. - Thu Bon. - The distribution of seed sources in the Thu Bon estuary is determined through consultation and field surveys (Figure 3.1).. - Distribution of S.guttatus in the Go Hi seagrass.. - Size of some fisheries resources related to coastal livelihoods A preliminary assessment of the size of groupers and juveniles was clearly visible in terms of fish size across the three seas. - In the sea areas of Danang and Cu Lao Cham, the smallest size of groupers and juveniles is 60 mm, while in the Thu Bon estuary is 20-30 mm. - essential habitats in the life span of the this fish, thus finding out the ecological – connectivity of this fish species in the coastal inhabitants of Quang Nam-Da Nang are nessecsary. - In the present context, when studying the migration of S.guttatus in the world is very difficult, the study of size and genetic linkage is a useful tool for understanding the ecological linkage of the most important resource of this sea.. - 3.3 ECOLOGICAL – CONNECTIVITY OF THE ORANGE- SPOTTED SPINEFOOT (Siganus guttatus) IN COASTAL HABITATS 3.3.1. - Considering the proportions of the size groups of orange-spotted spinefoot populations over time, from the first month of appearance of the Thu Bon River estuary (July 2014) to June 2015 in all three regions: Thu Bon estuaries, Cu Lao Cham and Da Nang can see the growth trend and movement of size groups (Figure 3.3).. - Figure 3.3 shows that July is the smallest fish size in the Thu Bon estuary (21-40 mm), which predominates over 70% of the breeding stock, continuing to August size 41-60 mm and less than 20 mm but small ratio.. - Groups of sizes 41-60 mm represent the highest rate, signaling the end of the period, but there are still late spawning in the group of 21-40 mm in size, less than 20% in fish stocks. - this is the smallest fish size in the two seas. - In march, april, may and june of the following year, almost no more fishing activities in Thu Bon. - This can be explained as follows: Thu Bon breeders reach the size of 61 mm, they begin to migrate from the Thu Bon to the next inhabitants of the life cycle. - The natural features of the river mouth this time facilitate the migration of fish. - By January 2015, at the end of the rainy season, the remaining remnants of fish were collected in fishing nets. - In February, almost no longer exploited fish in the Thu Bon estuary.. - The structure of the size groups according to the month of Siganus guttatus exploitation in three areas.. - In the sea of Da Nang and Cu Lao Cham areas in the rainy season (oct, nov,dec), there are many orange-spotted spinefoot with the size of 61-140 mm similar to that of the fish caught during this period in Thu Bon estuary.. - Genetic relationships of fish populations between the ecosystems A total of 35 individual fish in the above 3 areas above were collected for DNA analysis to investigate the genetic linkage of the S.guttatus.. - From the results of the analysis of community consultation information, analysis of the size and genetic linkage of the population combined with the data on the biological characteristics of S. - guttatus in the coastal habitats of Quang Nam-Da Nang are as follows: S. - feeding in the mangroves, at the Thu Bon estuary fishes appear dense, young fish move up to Cam Nam bridgehead. - Fishes in the Thu Bon estuary follow facing higher salinity waters and the subsequent colonization of coral reefs. - Cu Lao Cham and Da Nang where ecological conditions are appropriate with the food sources are algae and organic humus in the reef to continue to grow and develop. - In order to improve the picture of the life cycle of the orange-spotted spinefoot in Quang Nam and Da Nang sea, it is necessary to collect parental supplement samples to study the gonadotropic stage and the spawning grounds. - However, the funding is limited, so the thesis is only in the adult fish. - Thus, it is possible to say that the Thu Bon estuary is a nursery source for orange-spotted spinefoot supply to the Cu Lao Cham and Da Nang seas, contributing to the regeneration of fishpond resources in the coastal areas of Quang Nam- Da Nang and other neighboring areas. - In contrast, Cu Lao Cham and Da Nang marine areas provide broodstock for re-breeding of the Thu Bon estuary. - Therefore, the fish resources in the three sea areas are closely related, and the overexploitation of these area affects the two remaining areas. - Seaweed and mangroves in the Thu Bon River estuary are essential habitats in the sensitive period of fish life cycle, which is the scientific basis for proposing management solutions based on ecosystem.. - The decline in yield is most apparent in the Cu Lao Cham area. - In the Thu Bon estuary within the five years from 2010, mining yield also declined by 3.61%.. - The results of consultations with fishermen in Da Nang and Cu Lao Cham show that the reef fish production has declined sharply in recent years, especially in the high economic value group such as snapper, grouper and orange-spotted spinefoot fish. - Presently, the orange-spotted spinefoot fish and groupers have declined by 60-80% in the last 5-10 years. - Fisheries refugia of fish species in the Thu Bon estuary.. - The presence of coral reefs and seagrasses increases the diversity of habitat and species diversity in the sea. - The ecological characteristics of the estuary of the Thu Bon River are brackish with estuarine habitats, most important habitat are mangroves and seagrass.. - The difference between the resource characteristics of Danang and Cu Lao Cham is in the role of the rabbitfish. - Characteristics species of the Thu Bon estuary are Gobiidae, Mugilidae, Sparidae and Sparidae and seed of some fish involve with coral reef such as grouper, red-snapper and brown fish.. - The ecological-connectivity of the S.guttatus in the three areas represents the use of seagrass and coral reefs at different stages in the life cycle in which seagrass beds in the Thu Bon estuary play a role as nursing of seed supply to the Cu Lao Cham and Da Nang sea areas.. - At the same time, the establishment of a conservation area for orange-spotted spinefoot fish in the Go Hi seagrass, it is nesscesery establish appropriate harmonization between the benefit of the people and conservation.. - THE NEW CONTRIBUTION OF THE DISSERTATION 1. - The Proceedings of the South China Sea Conference. - Initial study on fish fauna in the Thu Bon estuary of Quang Nam province
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