The orange-spotted grouper (Epinephelus coioides) is a valuable food fish. To support the sustainable management of orange-spotted grouper fisheries, it is important to determine the optimum catchable size. The purpose of this study was to determine an optimal catchable size for the orange-spotted grouper stock in Kwandang Bay, North Gorontalo District, Indonesia. The Catchable size was determined based on the size at first sexual maturity, fecundity, and reproductive potential. The study was conducted from December 2016 to November 2017. The size at first sexual maturity was estimated based on the examination of gonads from 141 specimens, while fecundity was estimated based on a sample of 40 female fish with ripe gonads. The mean total length (TL) at first maturity was 40 cm. Fecundity ranged from 30,526 - 1,395,846 eggs with a mean of 687,025 eggs. The reproductive potential was highest in the size range of 55-64 cm TL. The recommended size for orange-spotted grouper is above 64 cm, to enable females to attain their maximum level of egg production before capture and thus contribute to maintaining the stock.

Abstract. Achmad DS, Gani S, Ardiansyah W, Mokoginta MM, Nurdin MS, Jompa J, Indrianti MA, Achmad N. 2022. Population dynamics of reef fish in the Kwandang Bay, Sulawesi Sea, Indonesia. Biodiversitas 23: 5217-5226. The grouper stocks in Kwandang Bay, Sulawesi Sea, Indonesia, are dominated by orange-spotted grouper (Epinephelus coioides) and coral trout (Plectropomus leopardus). However, the Kwandang Bay grouper fishery is currently experiencing serious challenges due to population decline resulting in a decline in both the average size of fish caught and the production volume. This study was conducted in Kwandang Bay, Sulawesi Sea, from January to December 2021. The population dynamics parameters estimated were growth, recruitment, mortality, exploitation rate and yield per recruit. The results showed that the total length (TL) of E. coioides and P. leopardus ranged from 16.50-101 cm and 17.90-60 cm, respectively, with Von Bertalanffy K-coefficients of 0.38 and 0.69, respectively. Recruitment occurred during most of the year, with respective recruitment value ranges of 0.99-17.11% and 0.08-19.22%. Natural and fishing mortality was 0.69/year-1 and 0.87/year-1 for E. coioides, 1.16/year-1 and 1.47/year-1 for P. leopardus. Beverton and Holt yield per recruit analysis indicated recruitment overfishing of both E. coioides and P. leopardus. Fishing regulations are needed to maintain a sustainable grouper fishery, including a 25% reduction in fishing vessels and gear, to enable the groupers of Kwandang Bay to spawn at least once during their life cycle.

Highlight Research There are 26 species identified to be originated from the bay, which the highest diversity in Indonesia Six species found in Kwandang Bay is showing trends of decreasing populations and two species vulnerable based on IUCN conservation list Growth model and Fulton condition factor determined for 14 species indicates that they live in a good state of well beings in the bay The models and condition factors also reflect the adequate food resources required for grouper growth which makes Kwandang Bay as a good habitat for groupers   Abstract Grouper fishery has been the source of income for 3,700 fishermen in Kwandang Bay. Since 2017, grouper populations in Kwandang have been depleting due to the absence of management. This research aimed to analyze species composition, length-weight relationship, and condition factor of the groupers. Samples were collected from fishers who caught the fish using traps, speargun, and handline. Samples were identified through a method by Heemstra and Randall, while the length-weight relationship was estimated using log-linear regression and t-test. The number of specimens identified during January - December 2021 was 1,571 individuals. Research showed that those samples consisted of 26 species under eight genera. Six species found in Kwandang Bay were showing trends of decreasing populations and two species were vulnerable based on the IUCN conservation list. Length-weight relationship analysis of 14 grouper species resulted in b value ranging from 1.6359 to 3.4417 and R2 ranges from 0.7718 to 0.9858. A significant test at a 95% confident interval showed that 14 species had an isometric growth pattern. Fulton condition factors show that Kwandang Bay is an essential habitat for groupers, and the bay can support the fish growth due to the adequate food availability.

Orange-spotted grouper is one of the coral reef fish has the economic value and exploited by local fisherman. Information about the size structure and sex ratio are urgent to formulate a policy for sustainability. This research aims to analyze the size structure and sex ratio of the orange-spotted grouper in Kwandang Bay. The research was conducted from December 2016 to November 2017. Sampling is carried out twice a month for one year. The total sample of orange-spotted grouper used for the analysis of the sex ratio was 149 individuals. Sample of orange-spotted grouper collected from fish landed and middlemen (grouper traders) at the Kwandang Fishing Port. Data analysis applying chi-square. The results show that males bigger than females. The sex ratio of orange-spotted grouper is 87.25 % female, 7.38 % male, and 5.37 % hermaphrodites. Orange-spotted grouper dominated by females and undergoes a gonad differentiation to male (protogynous hermaphrodite). It is concluded that The size of the male orange-spotted grouper is larger than that of the female grouper. The caught orange-spotted grouper is dominated by the female phase and undergoes a differentiation of the gonad from female to male (protogynous hermaphrodite)

Socio-economic information is needed in the formulation of responsible grouper management. This study aims to determine the socio-economic conditions of grouper fishermen in Bays of Kwandang. This research was conducted from January to July 2018. Primary data was collected through surveys and direct interviews with fishermen and fishermen figures.. The Collecting data using questionnaire assistance on 35 people respondents. Grouper fishermen in Bays of Kwandang were still in the category of traditional fishermen. The income of fishermen is below of Rp. 200,000/trip with the catch per trip less than 25 kg. To improve welfare, fishermen need subsidies from the local government. The subsidies are in form of fishing fleets and capital to develop business diversification in the fisheries sector. Keywords-Grouper fish, socio-economic, and bays of kwandang.

Population growth, the expansion of settlements and the increased activity of fishing activities either directly or indirectly, in the waters of this region get Oluhuta causing ecological pressures. The aimed of this research were to analysed the sustainability of space for metabolism of social ecological fishery utilization. Evaluation of sustainability in the region using the ecological footprint approach to fisheries. The sustainability of space for the metabolism of ecological social fishery system in this area is still at 1.96 km2/capita or undershoot conditions. Sustainable fisheries management should be oriented towards the problem using scientific methods based on the physical, biological, social, economic and cultural communities

Impacts of Implementation Regulation of The Ministry of Marine Affairs and Fisheries No. 1/Permen-Kp/2015 to Lobster Traffic Volume in Gorontalo Province. The implementation of the Permen NO. 1/PERMEN-KP/2015 with the aim to protect, preserve, and utilize crustacean resources.  This study aimed to analize impact of implementation Permen NO. 1/PERMEN-KP/2015 to lobster traffic volume in Gorontalo Province. The research result that highest of lobster traffic volume on 2012 and lowest on 2016. There was a significant difference (p <0.05) between lobster traffic volume before and after implementation of Permen KP NO. 1/PERMEN-KP/2015. Implementation of Permen KP NO. 1/PERMEN-KP/2015 turned positive impact to lobster because provides a lobster opportunity to regenerate.