Water Quality and Trophic Status of Koto Panjang Reservoir, Indonesia

Koto Panjang Reservoir is one of the hydroelectric power plants in Indonesia, located in Kampar Regency, Riau Province. This paper aims to determine the water quality and tropic status of the Koto Panjang Reservoir. The research was carried out along the Koto Panjang Reservoir, covering the floating net cages area, inlet, outlet, and the center of the reservoir. Water samples were collected twice a year, February and September 2017. The results showed that the water quality of Koto Panjang reservoir is still within the tolerance range for the aquatic organisms' life, including fish. Based on the TSI analysis, the Koto Panjang Reservoir throphic status was categorized as eutrophic to heavy eutrophic. This study recommends that relocating floating net cages is necessary so that the nutrient load will not only be concentrated in one location. The efficiency of using the feed for floating net cages could minimize the waste.

A Semi-Analytical Model for Studying Hydroelastic Behaviour of a Cylindrical Net Cage under Wave Action

In the present study, a semi-analytical model based on the small-amplitude wave theory is developed to describe the wave fields around a single gravity-type cylindrical open fish net cage. The cage may be submerged to different depths below the free-water surface. The fish cage net is modelled as a flexible porous membrane, and the deflection of the net chamber is expressed by the transverse vibration equation of strings. The velocity potential is expanded in the form of the Fourier–Bessel series and the unknown coefficients in these series are determined from matching the boundary conditions and the least squares method. The number of terms for the series solution to be used is determined from convergence studies. The model results exhibit significant hydroelastic characteristics of the net cages, including the distribution properties of wave surface, pressure drop at the net interface, structural deflection, and wave loading along the cage height. In addition, the relationships between wave forces on the net cage with hydrodynamic and structural parameters are also revealed. The findings presented herein should be useful to engineers who are designing fish cage systems.

The use of fish silage to increase feed efficiency and growth of grouper (Epinephelus coioides) in floating net cages

This study aimed to investigate the efficiency of fish silage mixed in compounded diets on growth and survival rate of grouper (Epinephelus coioides). Grouper (2,34±0,24 cm, and 4,17±1,82 g) were divided into four groups and cultivated in 1x1x1,5 m floating net cages. Each group fed with compounded diets containing 0, 1, 3 and 5 g/kg fish silage diet twice daily. Fish were sampled for growth performances and feed efficiency at 14 days interval for 10 weeks. Results indicated that compounded diets at 1 and 3 g/kg silage affected the growth rate. Total length, specific growth rate and weight gain significantly increased in fish received 1 and 3 g/kg silage diets. The feed intake seen to be highest in groups administered 3 g/kg silage, whereas the best feed conversion ratio was found in fish fed 1 g/kg silage. Thus, this study indicated that using fish silage in compounded diets may affect feed efficiency and growth performances of grouper juveniles.Keywords:Artificial dietFeedingFish silageGrouperNet cages

The application of integrated multi-trophic aquaculture (IMTA) using floating net cages on Tilapia fish with native fish (Peres, Lemeduk, and Depik)

Environmental problems due to aquaculture occur along with the increase in aquaculture production. IMTA is one system used as a solution in dealing with environmental problems. The objective of this study was to analyze the growth performance, survival rate, and production of the main commodity (tilapia) and the supporting commodities (Peres, Lemeduk, and Depik) which are applied through the application of integrated multi-trophic aquaculture (IMTA) using floating net cages. This research was conducted at the Lukup Badak Fish Seed Center, Central Aceh from July to August 2020. The experimental design used was a completely randomized design (CRD) with 4 treatments and 3 replications, namely: A (tilapia), B (tilapia and peres), C (tilapia and lemeduk), and D (tilapia and depik). ANOVA test results showed that the IMTA system had a significant effect on absolute length growth, absolute weight growth, specific growth rate (SGR), survival rate, and biomass production of tilapia (P0.05). The results showed that maintenance for 42 days produced the highest value in treatment B with the increase in absolute length growth (4.26cm±0.24); absolute weight growth (5.47g±0.45), specific daily growth rate (2.28%/day±0.13) and the highest tilapia biomass production (480g/0.5m2±19.25). The highest survival rate was found in treatment C (82.42%±2.28). It was concluded that the treatment using the IMTA system was better than without the IMTA system.Keywords:IMTAWater qualityGrowth performanceTrophic interactionBiomass production

Impact of the Covid-19 Pandemic on Activities Socio-Economic Floating Net Cages (FNC) Business in the Koto Panjang Hydropower Reservoir, Riau Province

The purpose of the study was to analyse the impact of social activities related to cultivation and outside the cultivation business as well as economic activities before and after covid-19. The method used in this research is a survey method. Data collection was carried out on 20 farmers, three fish seller, and two fish feed sellers. Data analysis was carried out quantitatively and qualitatively. The results showed that before the pandemic, 80% of FNC cultivators’ social activities were done face-to-face and after the pandemic, only 40% were face-to-face and the rest were through mobile phones. Social activities outside the FNC such as worship, marriage and other attendance frequency is reduced by 5% - 25% after the pandemic. The economic activity of aquaculture has decreased after the Covid-19 outbreak by 50% in 2020 and 37.5% in 2021. In 2021 cultivators have made a profit but it is lower than the profit before the covid-19 pandemic. The economic activity of aquaculture has decreased after the Covid-19 outbreak by 50% in 2020 and 37.5% in 2021. In 2021 cultivators have made a profit but it is lower than the profit before the covid-19 pandemic. The economic activity of aquaculture has decreased after the Covid-19 outbreak by 50% in 2020 and 37.5% in 2021. In 2021 cultivators have made a profit but it is lower than the profit before the covid-19 pandemic.

Phosphorus load base carrying capacity estimation for fish culture in Lake Ranau in Indonesia

Carrying capacity is the ability of waters to accommodate pollutant load inputs without reducing the water quality. For aquaculture in floating net cages (FNC), the carrying capacity is a criterion to achieve the maximum fish production based on the level of total phosphorus (TP) released from the activity, which is still acceptable according to utilisation purposes. Lake Ranau in Sumatra is essential in supporting the socio-economic needs of the people in the surrounding areas, including FNC activities. The development of FNC as an aquaculture model in open waters will have a positive value as long as it is within the limits of water carrying capacity. Thus, the carrying capacity of Lake Ranau waters needs to be estimated to provide optimal direction for FNC development in line with other activities such as tourism. The carrying capacity was estimated using the Beveridge (1987) formulation that has also been adopted into the Ministry Regulation of Environment number 28/2009. As a limiting factor for tourism purposes, the status trophic of waters should be oligotrophic or oligo-mesotrophic. Therefore, the fish production that can be achieved is between 0 tons/year (oligotrophic scale) to 1,662 tons/year (oligo-mesotrophic scale).

Inhibition test of mangosteen peel extract (Garcinia mangostana L.) against bacterial diseases of tiger grouper (Epinephellus fuscoguttatus)

Cultivation of tiger grouper (Epinephelus fuscoguttatus) in Floating Net Cages in several locations in Bireuen Regency has developed. The potential disease issue can be caused by bacteria, viruses, fungi, or parasites. The purpose of this study was to determine the effectiveness of mangosteen peel extract capsules (Garcinia mangostana L) against bacterial disease in tiger grouper. This research was carried out in April 2019 at the MIPA Laboratory of Al Muslim University and the laboratory of PT. Centra Proteina Prima, Bireuen Regency. The design used was a completely randomized design with four treatments (0%, 10%, 20%, and 30% mangosteen peel extract capsules) with three replications. The parameters studied in this study including the diameter of the inhibition and the observation of MBC (Minimum Bacterial Concentration). The result showed that the administration of mangosteen peel extract capsules with doses of 10%, 20%, and 30% has no significant effect on reducing disease-causing bacteria in grouper grown on TSA media. Positive results were obtained on positive (+) MBC observations, presumably due to the small dose of mangosteen peel extract capsules given so that it could not kill bacteria grown in dishes with an inhibition range of 0 mm.Introduction

The Growth Rate of Seabass in Floating Net Cages, Inner Ambon Bay using 1D Ecosystem Model

Inner Ambon Bay is used for fishery research by the government. One of the species that has been cultivated is seabass because it has high economic value. Seabass cultivation in floating net cages has been developed by Ambon Marine Aquaculture Institute (BPBL-Ambon). The characteristics of seawater in Inner Ambon Bay (IAB) based on the observation data in the project “Ocean Current System of Indonesia Waters and Its Effect on Marine Fisheries Production” in May 2017 show that the temperature is in the range 29.8 – 30.9 °C. Meanwhile the salinity is about 26.1–31.4 PSU and the chlorophyll concentrations as much as 0.88 – 3.61 mg/m3. The 1D ecosystem model simulation is performed to know how is the growth rate of seabass is with two-way interaction between nutrient, phytoplankton, zooplankton, and detritus (NPZD) towards zooplanktontivor (fishes which consume zooplankton). The verification of model result (fish mass) with the observation data of fish mass which conduct by BPBL Ambon show the RMSE value is 0.001 kg and the correlation is 0.99. The nutrient concentration since 2016 – 2018 in the range of 3.08 – 3.78 mmolC/m3. While the phytoplankton, zooplankton, and detritus concentration during 3 years each one is 4.67 – 5.84, 11.53 – 15.77, and 16.88 – 20.67 mmolC/m3. The fastest growth rate of Seabass with the first scenario is 1.52 grams/day with the duration of 257 days and when the juvenile of seabass spread in January. The fastest growth rate of Seabass with addition feed is 2,23 grams/day during 175 days.