| dc.description.abstract | The waters of Inner Ambon Bay (IAB) are influenced by tidal currents that distribute food, physical dan chemical environmental parameters, waste, sediment, and larvae of fish. One of the fish resources associated with seagrass habitats in TAD waters is White-sptotted rabbitfish (Siganus canaliculatus). Seagrass habitat is widely distributed in IAB which form single and mixed vegetation seagrass beds, with different vegetation densities and their presence is influenced by environmental parameters, substrate type/sediment and anthropogenic activity. The differences in the physical characteristics of the seagrass habitat in IAB are thought to affect the character biometric, genetic, and population biological of S. canaliculatus in IAB. This study aims to compare 1) biometric character, 2) genetic character, 3) spatial distribution, 4) variation of growth and reproduction in different seagrass habitats, and 5) to analyze population dynamics of S. canaliculatus in IAB waters. Research in IAB waters was conducted in August 2018 - July 2019, the sampling stations namely Station 1. (Tanjung Tiram) and 2 (Halong) represent mixed vegetation seagrass habitat, Station 3 (Poka) and 4 (Nania) represents a single vegetation seagrass habitat. Fish samples were collected once a month using beach seine, along with the measurement of enivonmental parameters, including depth, turbidity, temperature, salinity, pH, dissolved oxygen, phosphate, nitrate, and chlorophyll-a. The density and diversity of seagrass vegetation were estimated based on a systematic sampling method. Observations of biometric characters, gonad maturity levels, and fecundity were carried out at the Oceanographic Biology Laboratory, Center for Deep Sea Research - LIPI Ambon. Genetic testing was carried out at the Molecular Biology Laboratory of the Department of Aquatic Resources Management, Faculty of Fisheries and Marine Sciences, IPB University. The collected fish samples were classified into 3 stages, namely: juvenile, pre-adult, and adult. A total of 50 fish samples were measured 21 characters truss morphometric, and 14 fish samples were genetically tested using the mitochondrial cytochrome oxidase I (COI) molecular marker amplified by the Polymerase Chain Reaction (PCR) technique using universal primers for aquatic biota. All good quality PCR products are shipped to 1st Base in Malaysia. Fish samples were also measured for length, weighed, and dissected for determination of the gonad maturity levels morphologically and fecundity observations. Biometric analysis using Minitab ver. 16 for Principal component analysis (PCA) and similarity dendrogram, while discriminant canonical analysis using SPSS ver. 16. Sequencing data were corrected and aligned using MEGA (Molecular Evolutionary Genetics Analysis) software version 7.0. DNA Sequence Polymorphism (DnaSP ver 5) was used to analyze genetic diversity including haplotype diversity (Hd) and nucleotide diversity (π). Phylogeny tree construction based on the Neighbor-Joining method and genetic distance using MEGA ver. 7. Genetic differentiation intra and inter population using Analysis of Molecular Variance (AMOVA) and Fixation Index (Fst) using Arlequin software. Analysis of growth patterns, condition factors, sex ratios, size of gonad maturity, and fecundity using Excel 2010 software. processed using Past ver.3.14 software. Analysis of fish population dynamics using ELEFAN (Electronic Frequency Analysis) I FiSAT model (FAO-ICLARM Stock Assessment Tools) includes growth, mortality, and recruitment. The results showed that the biometric character of White-spotted Rabbitfish (S. canaliculatus) in IAB waters varied between seagrass habitats, with two morphometric truss characters to differentiate between populations, namely; 1) The tip of the upper mouth - The end of the head bone (A1) and 2) The end of the head bone - to the beginning of the dorsal fin (B2), by forming three population groups based on biometric characters. Variations in the biometric characters of S. canaliculatus populations between seagrass habitats were supported by genetic variations with the discovery of interpopulation specific nucleotide sites. Three populations groups were formed based on the genetic distance between different seagrass habitats, with high interpopulation genetic differentiation compared to intrapopulation (78.81%> 21.19%). There were 8 specific haplotypes and 2 general haplotypes in the S. canaliculatus population in IAB waters. A total of 1,050 individuals of S. canaliculatus were collected during the study consisting of 598 males and 452 females. The result of principal component analysis in the form of a biplot graph shows that S. canaliculatus tends to have different seagrass habitat preferences based on its life stage. The juvenile size is widely distributed in all types of seagrass habitat. The pre-adult size tends to be distributed in the mixed vegetation type of seagrass habitat, while the adult size is in the single-vegetation type of seagrass habitat. The body length of S. canaliculatus differs between seagrass habitats, with isometric growth patterns in all types of seagrass habitat for male and female populations, with a good condition factor and increases with increasing body length. The sex ratios of male and female fish populations differed between seagrass habitats, and the first size of maturity of male and female populations was greater than that of females (23.2 cm> 22.6 cm). Based on the average value of the gonad maturity index in each month of observation, it is predicted that the peak of the spawning season will be in February. The fecundity of S. canaliculatus is relatively high and differs between seagrass habitats, with an average value of 478,351 eggs, and there is a positive relationship between fecundity and body length and weight, meaning that the longer the length and body weight, the greater the resulting fecundity. The S. canaliculatus population in IAB has a high coefficient of growth and total mortality, respectively 1.51 per year and 4.54 per year, inversely proportional to the maximum age which can reach 3 years, and an asymptotic length of 30.55 cm. relatively short. Fishing mortality is lower than natural mortality (2.18 <2.37), with the current exploitation rate (Ecurr) already higher than the optimal exploitation rate (E50) ((0.48> 0.32 per year), and maximum economic yield (E10) ((0.48> 0.47 per year), but still below the maximum sustainable yield (Emax) ((0.48 <0.56 per year). Based on information on biometric characters, genetics, spatial distribution, growth and reproduction as well as population dynamics, it is time for the management of White-spotted Rabbitfish (S. canaliculatus) to realize its sustainable use in the waters of IAB. Management can be carried out through two aspects, namely: 1) Population aspects with a biotechnical approach through: a) limiting fishing effort, and fishing gear selectivity by determining the size of S. canaliculatus that is allowed to be caught must be > 23 cm in order to support optimal growth and reproduction, and b) rehabilitation of S. canalicuatus stocks through domestification by selecting parent sources based on the consideration of seagrass habitats that have high intra-population genetic diversity for the development of restoking in seagrass habitats with populations that have low genetic diversity, so as to support gene flow through cross-breeding between S. canaliculatus populations in different seagrass habitats in IAB waters, and 2) Habitat aspects to support the ecological function of seagrass beds as grazing areas, nursery areas and rearing, through; a) priority in-situ conservation area development in mixed vegetation seagrass habitats that have high intra-population genetic diversity of S. canaliculatus, and b) priority improvement and restoration of single vegetation seagrass habitat and control of watersheds to reduce sedimentation rates and reduce anthropogenic pollution loads in seagrass habitat in IAB waters. Keywords: Siganus canaliculatus, biometric and genetic characteristics, spatial distribution, growth, reproduction, population dynamics, Inner Ambon Bay. | id |
