Net Cages Research Articles

Transfer Teknologi Pengayaan Bibit Rumput Laut Yang Dibudidayakan Dengan Keramba Jaring Apung

Inappropriate cultivation methods and a decrease in the quality of seaweed seeds are some of the obstacles in seaweed production. Technology transfer activities through community service programs aim to provide learning to seaweed farmers on how to enrich seaweed seeds with bionic fertilizer and then cultivate them using the floating net cage method. The activity was carried out on August 24-25, 2022 at the Main Base Command Headquarters of the Indonesian Navy VII Kupang. The method used was a participatory empowerment approach involving seaweed farming communities with counseling and dissemination. Seaweed cultivation with the floating net cage method showed higher absolute growth, relative growth and daily growth rate compared to the longline method, which were 11.91 ± 0.69 g day-1, 0.032 ± 0.002 g g-1 day-1 and 3.14 ± 0.17% day -1, respectively. While in the longline method, it was 9.48±1.81 g day-1, 0.027±0.004 g g-1 day-1, and 2.65±0.43% day -1, respectively.

Monitoring system ammonia concentration using fiber optic sensor based surface plasmon resonance

<p class="15">A monitoring system for ammonia concentration in waters has been created using fiber optic sensors based on surface plasmon resonance (SPR). Monitoring is carried out to measure the decline in water quality due to the toxic compound ammonia from floating net cages (KJA) activities used as aquaculture sites. The sensor performance was improved by replacing the cladding using gold nanoparticles to increase the sensitivity of the fiber optic sensor based on the SPR phenomenon. The sensor consists of a laser diode as a light source, optical fiber as a waveguide and OPT101 as a photodetector. The Arduino Nano microcontroller is used as a data processor, LoRa as a transmission system and the MCU node as a data receiver. The results of measuring the ammonia concentration received by the MCU node are displayed on a Google spreadsheet in real time. Testing of measuring instruments is carried out by comparing the measurement results with a UV-Vis spectrophotometer. The test results obtained an accuracy value of 94.09% for optical fibers using the dip coating method and 78% for optical fibers using the thermal evaporation coating method.</p>

Comparison of Nutritional Composition, Mineral and Heavy Metal Content of Rainbow Trout from Different Aquaculture Systems

In this study, proximate compositions, meat yields, mineral matter (Na, Mg, Ca, K), and heavy metal (As, Fe, Zn, Se, Mn, Co, Cu, Pb, Ni) contents of rainbow trout (Oncorhynchus mykiss) obtained from concrete pond systems and dam lake net cage were examined. Mineral and heavy metal contents were measured by ICP-OES instrumental analyser. According to the results of rainbow trout meat yield and nutritional composition analysis varied between; meat yield were 57.43-66.40%, crude protein were 16.99-19.93%, crude fat were 3.07-4.18%, crude ash were 0.98-1.58%, and moisture contents were 75.10-77.65%. Mineral contents of Ca 2.66-30.58 mg.kg-1, Na 19.53-36.04 mg.kg-1, K 252.79-310.05 mg.kg-1, and Mg 120.75-137.44 mg.kg-1 were detected in the presented ranges. Detected heavy metals were As 0.42-0.56 mg.kg-1, Fe 2.16-3.69 mg.kg-1, Zn 2.67-4.69 mg.kg-1, and Se 0.17-0.77 mg.kg-1. On the other hand, Mn, Co, Cu, Pb, and Ni were not detected. As a result of the study, it was found that the proximate composition, meat yield, mineral matter, and heavy metal contents of rainbow trout vary depending on the location and size of the fish (p<0.05). However, the heavy metal levels detected in muscle tissue did not exceed the consumption limits.

Effect of light exposure on circadian rhythm in theront excystment in Cryptocaryon irritans

We examined the effects of light exposure on the theront excystment circadian rhythm in Cryptocaryon irritans using a newly invented apparatus, which enabled us to examine the excystment rhythms of theronts from tomonts with low labor. Using the apparatus, we examined the timings of theront excystment from tomonts exposed directly to light and from tomonts exposed to light-exposed seawater by counting the number of excysted theronts. We found that the theront excystment time changed only when tomonts were directly exposed to light, indicating that light reception is essential for circadian rhythm entrainment. When tomonts were exposed to light only once for 12 h, either on Day 1, Day 2, or Day 3 after leaving host and being encysted, the circadian rhythm was entrained according to the photoperiod given on tomonts. Tomonts exposed to a low light (1 lx) with 12L:12D photoperiod daily showed a circadian rhythm similar to that in tomonts exposed to an intense light (500 lx) under the same photoperiod. When tomonts were incubated at 22 °C, 25 °C, or 28 °C under the same photoperiod, almost the same circadian rhythm was developed, suggesting temperature has little effect on the circadian rhythm entrainment between the range, even though the date of excystment was delayed in lower temperatures. These results suggest the circadian rhythm of theront excystment can be entrained in tomonts on the seabed of inner bays where net–cage aquaculture is conducted, and be involved in the outbreaks of cryptocaryoniasis there.

The Success of Freshwater Aquaculture Program: Nile Tilapia or “Nila” Culture In Indonesia

This paper discusses the current status of tilapia aquaculture production, historical development based on the production growth, technological advances in genetic improvement and culture system, trade and product development, strategies, and policies in maintaining and improving national production. All data and information used in this manuscript were collected from available publications relating to the past and present status of tilapia cultivation in the country. Nowadays, Indonesia is the second-largest tilapia producer in the world with the contribution of about 25.89% to tilapia global production. In Indonesia, tilapia is the largest production among other cultured species. The annual growth production of tilapia is inccread 11.61% from 2011 to 2018. West Java Provinceis the largest tilapia producer followed by West Sumatra, South Sumatra, and Central Java. In the last six years, most of tilapia production comes from pond culture followed by floating cages, net cages, paddy fields, and pen culture. The success of tilapia culture is much influenced by technological improve in grow-out and genetic improvement of the local varieties. A side of that, trading and global market oriented are also established with various acceptable products. Tilapia aquaculture in Indonesia shows the succsess story of freshwater aquaculture program from nothing before 1990 to be something at present time. To maintain and increase the future production of tilapia, it needs strategies and policies in production and trade. The tilapia program maybe used as a role model for another economic imprortant freshwater species in Indonesia.

Hydrodynamic Analysis of a Multi-Pile-Supported Offshore Wind Turbine Integrated with an Aquaculture Cage

The integrated development of offshore wind power and marine aquaculture is becoming increasingly important. However, the impact mechanism of integrating a net cage on the dynamic characteristics of offshore wind turbines remains unclear. This paper presents a design scheme for a multi-pile-supported offshore wind turbine integrated with an aquaculture net cage and conducts a preliminary theoretical analysis of the influence of an additional net cage on the wind turbine. The analysis reveals that the primary effect is an increase in hydrodynamic loads on the wind turbine foundation, while the structural frequency of the wind turbine remains largely unaffected. Furthermore, computational fluid dynamics (CFD) numerical models, whose accuracy is verified by physical experiments, are utilized to compare the hydrodynamic characteristics of the offshore wind turbine foundation with and without the net cage, considering different net solidities. The simulations identify significant changes in the flow field surrounding the foundation due to the presence of the net cage, resulting in a considerable increase in the overall hydrodynamic load on the foundation. Moreover, the mutual interference between the netting and the foundation amplifies their respective hydrodynamic loads and concentrates these loads at the upstream section of the structure. The maximum increase in hydrodynamic load for a single pile reaches 6.32 times its original value, posing significant risks to the structure. Finally, a preliminary feasibility analysis of the scheme was conducted. The results presented in this article can serve as a theoretical basis for the design of such innovative structures.

Time–Frequency Analysis of Nonlinear Dynamics of an Aquaculture Cage Array in Waves

The nonlinear dynamic response of an aquaculture cage array caused by wave-frequency and low-frequency excitations coupled with the nonlinearity of the mooring and the netting system is a complicated problem. So far, this problem still has not been completely understood. To address this issue, we consider the nonlinear interaction of an extreme wave with an aquaculture cage array containing 16 net cages in a 2 × 8 configuration. This paper aims to provide insight into understanding the nonlinear dynamics of an aquaculture cage array via time–frequency analysis. Time-domain analysis shows that the cage array exhibits weak nonlinearity in the surge and heave motions. On the contrary, there is strong nonlinearity in the sway motion under 45° and 90° wave attacks. Aside from this, the frequency-domain analysis indicates that nonlinearities exist in all three of these different responses (surge/sway/heave). Particularly, the low-frequency component has a predominant effect on the nonlinearity of the sway motion under 45° and 90° wave attacks. With this understanding, future aquaculture fish farms that contain multiple cages (i.e., cage array) can be potentially designed to withstand severe conditions in the open ocean.

Viral Nervous Necrosis and Vibriosis in Grouper Fish: A Case Study

Viral Nervous Necrosis (VNN) and Vibriosis are contagious diseases that can affect grouper fish from the larval to adult stages and cause significant economic losses for farmers. The owner brought the sunuk grouper to BKIPM Mataram to determine the fish's health. Since the grouper arrived at the floating net cage, the owner reports it has sustained bodily injuries. The grouper is separated from the healthy fish and placed in the area where the sick fish are. During maintenance, the fish exhibits a decrease in appetite, wounds on the mouth, operculum, and body from the head to the tail, low mobility, and swimming upside-down. The physical examination revealed that the fish was swimming limply in an inverted position and had lesions on various body parts. According to virological and bacteriological laboratory tests, the sunuk grouper infected with Vibriosis and VNN can be affected by the condition of fish that have been sick since they first arrived. Also, stress, contact with infected fish, and a decreased appetite result in sunuk grouper contracting the disease. Due to a disease, a fish's immune system does not function optimally. This condition makes sunuk susceptible to several infectious diseases.

Dietary supplementation with a PPARγ agonist promotes adipocyte hyperplasia and improves high-fat diet tolerance and utilization in grass carp (Ctenopharyngodon idellus)

Due to the wide usage of high-fat diets in aquaculture, improving the ability of fish to utilize high-fat diets is one of the important issues in the field of aquaculture nutrition. Studies in mammals have proven that increasing the number of adipocytes improves high-fat diet-induced metabolic disease, suggesting that promoting adipocyte hyperplasia has potential as a novel nutritional strategy to reverse the negative effects of high-fat diets in farmed fish. To verify this hypothesis, a total of 270 juvenile grass carp (Ctenopharyngodon idellus) (34.57 ± 0.29 g) were randomly divided into 15 net cages, and a PPARγ agonist (rosiglitazone) was added to the high-fat diet to promote PPARγ-mediated adipocyte hyperplasia. The results showed that PPARγ was activated in adipose tissue instead of the liver and muscle, resulting in adipogenesis and healthy adipose tissue remodeling, including an increased ability to store and metabolize fat and decreased lipid accumulation, immune cell penetration and fibrosis, as well as inflammation. In addition, promoting PPARγ-mediated adipocyte hyperplasia significantly reduced the levels of inflammation in serum, liver and muscle (P < 0.05) and significantly reduced the serum contents of total triglycerides, total cholesterol, aspartate aminotransferase and alanine aminotransferase (P < 0.05), indicating that the tolerance of grass carp to high-fat diets was increased. Subsequently, the growth performance and feed efficiency were significantly improved. Meanwhile, hepatic steatosis decreased as a result of reduced lipid absorption and synthesis, and the synthesis of protein in muscle was significantly increased by promoting the ability of muscle to utilize fat. Taken together, activating PPARγ-mediated adipocyte hyperplasia not only increases the tolerance of grass carp to high-fat diets but also promotes the utilization of high-fat diets and increases the protein-sparing effect of fat in grass carp. Our study indicates that targeting PPARγ-mediated adipocyte hyperplasia to change the pattern of adipose tissue expansion is a nutritional strategy to develop feed additives, which are used to reverse the negative effects of high-fat diets and promote the utilization of high-fat diets in farmed fish.

Efficiency of Nile tilapia cultivation business using biofloc technology as an alternative to the use of floating net cages in the waters of Lake Batur, Bali

Efficiency of Nile tilapia cultivation business using biofloc technology as an alternative to the use of floating net cages in the waters of Lake Batur, Bali

Physiological stress responses of European seabass Dicentrarchus labrax related to changing operations of floating net cages in intensive farming conditions at the Moroccan M'diq bay.

The present study purposed to quantify and compare in-situ the primary and secondary physiological stress responses, related to the operation of floating net-cages changing, in both sub-adults (523 days post hatching) and adults (916 dph) European sea bass Dicentrarchus labrax, under intensive farming conditions in the Moroccan M'diq Bay. Levels of cortisol, glucose, total cholesterol, total protein and lactate, as well as the percentage of hematocrit were measured before and after stress. The results showed significantly elevated levels of cortisol and blood glucose in both age groups, while total cholesterol and protein levels were unaffected. In fact, blood lactate was significantly reduced in sub-adults, while in adults this parameter was not affected by the operation. However, the hematocrit percentages measured after the operation were significantly higher than those found before the operation in both groups of fish, which is linked to the increased rate of oxygen renewal by the new net cages and the lower water temperature inside the cages. With regard to the age-specific response during this essential operation - before and after the operation - plasma cortisol, blood glucose and lactate concentrations, as well as plasma total protein levels, were significantly higher in sub-adults than in adults. It is concluded that aquaculture practices such as changing the aquaculture net-cage could have repercussions in terms of the classic physiological responses to stress in D. labrax. This article is protected by copyright. All rights reserved.

Modeling particulate waste assimilation by blue mussels within the spatial constraints of a commercial fish farm: implications for multitrophic aquaculture

Commercial salmonid farming is typically performed in open-water net cages where interactions between the environment and production unit might be widespread and not easily predicted or controlled. Integrated multi-trophic aquaculture (IMTA) has been suggested to mitigate some of the environmental impacts. Based on empirical data, the assimilation of particulate waste from a commercial fish farm was modeled by two approaches to salmon/blue mussel IMTA: a system with mussels at the surface next to the fish farm and an alternative setup with mussels submerged under the farm. According to the model, 15% of the feed was defecated and assumed available to the mussels and the submerged mussel farm could assimilate 14.6% of the feces. Sensitivity analysis showed that the current speed, the mussel filtration rate, and the proportion of the material that settles slowly had an impact on this assimilation estimate, which could be significantly higher. However, the model did not include assimilation limitations due to particle size, which may contribute significantly to the submerged farm. The mussel farm at the surface mainly received small slow settling particles, and according to the model, only 0.4% of the fish farm waste was assimilated. The maximum obtainable assimilation was 5.5%. The fraction of slowly settling waste had the most pronounced influence on waste assimilation in the mussel farm at the surface. This is also among the most uncertain parameters, since the relative portion of different settling velocities of fish feces is highly variable, and more information on the size distribution of waste is needed.

Characterization and finding the origin of off-flavor compounds in Nile tilapia cultured in net cages in hydroelectric reservoirs, São Paulo State, Brazil

An increasing demand for fish products has led to an intensive aquaculture production in Brazil, and cultivation of fish constituted 860 × 103 tons in 2022, contributing to the 87% of total fish consumption. Nile tilapia constitutes almost half of the aquaculture production, and most tilapia farms use floating net cages. One of the major constraints of intensive fish production is production of off-flavors. Release of nutrients by the fish leads to deterioration of the water quality and stimulates growth of microorganisms, also including off-flavor producing species. The objective of this study was to determine levels of taste and odor compounds (geosmin, 2-MIB and a selection of volatile compounds) and their impact on the flavor quality of Nile tilapia produced in net cages in reservoirs in São Paulo State, Brazil. GC-MS analysis of fish and water from six different farms showed concentrations of geosmin in the water from 1 to 8 ng/L, while geosmin in fish flesh ranged from 40 to 750 ng/kg. The level of 2-MIB in water was 2 to 25 ng/L, and 0 to 800 ng/kg fish. The GC-MS analysis also revealed presence of more than 100 volatile organic compounds in the fish flesh, consisting of aldehydes, alcohols, benzene derivatives, hydrocarbons, ketones and few other compounds. Geosmin and 2-MIB related flavor notes were detected in all fish by a sensory panel, and a high correlation between the chemical and sensory analyses was found. The potential impact of the volatile organic compounds on the fish flavor is discussed. Analysis of the water quality in the reservoirs indicated that levels of geosmin and 2-MIB levels were highly influenced by the nutrient levels in the water.

Implementation of Fisherman Empowerment through Floating Net Cage in Terihindo Jaya Lestari Fisherman Group in Kampung Terih

Indonesia is the largest maritime and archipelagic country in the world. The biggest problem in Indonesia, which covers 75% of the ocean area, is the gap between this enormous potential and optimal utilization capacity. In exploiting this potential, it can be done by increasing the aquaculture sector. One solution to this problem is to carry out a community empowerment program that targets fishermen. This study aims to describe the implementation process of empowering fishermen in the Tangguh Kelong program by utilizing floating net cages (KJA) fostered by PT Pertamina Patra Niaga DPPU Hang Nadim and other stakeholders so that it can be developed and sustainable. This research is research with the descriptive qualitative method by describing problem-solving based on the results of interviews, observations, and literature studies. The results of this study indicate that the implementation of the Kelong Tangguh program in the Trihindo Jaya Lestari Group has had an impact on increasing economic welfare, increasing employment, increasing capacity and social interaction, as well as activities aimed at improving the underprivileged community in Terih Village. In implementing the Tangguh Kelong program, PT Pertamina Patra Niaga DPPU Hang Nadim provided various facilities such as capacity building and infrastructure development. Apart from that, the Kelong Tangguh program also uses social innovations in the implementation of the program, namely the construction of floating guard houses, the use of solar panels, floating restaurants, and frozen food management. The existence of the Kelong Tangguh program is expected to help increase the economy, especially for members of the Trihindo Jaya group and the surrounding environment, and in the future, the Kelong Tangguh program can be implemented in other areas in carrying out fishermen group empowerment programs.

First Report of Aeromonas veronii as an Emerging Bacterial Pathogen of Farmed Nile Tilapia (Oreochromis niloticus) in Brazil.

Brazil is one of the world's leading producers of Nile tilapia, Oreochromis niloticus. However, the industry faces a major challenge in terms of infectious diseases, as at least five new pathogens have been formally described in the last five years. Aeromonas species are Gram-negative anaerobic bacteria that are often described as fish pathogens causing Motile Aeromonas Septicemia (MAS). In late December 2022, an epidemic outbreak was reported in farmed Nile tilapia in the state of São Paulo, Brazil, characterized by clinical signs and gross pathology suggestive of MAS. The objective of this study was to isolate, identify, and characterize in vitro and in vivo the causative agent of this epidemic outbreak. The bacterial isolates were identified as Aeromonas veronii based on the homology of 16S rRNA (99.9%), gyrB (98.9%), and the rpoB gene (99.1%). A. veronii showed susceptibility only to florfenicol, while it was resistant to the other three antimicrobials tested, oxytetracycline, enrofloxacin, and amoxicillin. The lowest florfenicol concentration capable of inhibiting bacterial growth was ≤0.5 µg/mL. The phenotypic resistance of the A. veronii isolate observed for quinolones and tetracycline was genetically confirmed by the presence of the qnrS2 (colE plasmid) and tetA antibiotic-resistant genes, respectively. A. veronii isolate was highly pathogenic in juvenile Nile tilapia tested in vivo, showing a mortality rate ranging from 3 to 100% in the lowest (1.2 × 104) and highest (1.2 × 108) bacterial dose groups, respectively. To our knowledge, this study would constitute the first report of highly pathogenic and multidrug-resistant A. veronii associated with outbreaks and high mortality rates in tilapia farmed in commercial net cages in Brazil.

Feasibility Analysis of Tilapia Fish Farming in Floating Net Cages (KJA) in Lake Ranau

Lake Ranau is located on the border of West Lampung Regency, Lampung Province and South Ogan Komering Ulu Regency, South Sumatra Province. Lake Ranau has functions including ecological and socio-economic cultural functions. Some important technical aspects in a tilapia aquaculture business in KJA include KJA components, maintenance/production processes ranging from seed stocking, feeding to harvesting and constraints faced by farmers during the production process. The criteria observed in determining the feasibility of tilapia KJA cultivation include: investment costs, profits, profitability, BEP (Break Event Point) and R / C Ratio (Revenue Cost Ratio). Economically, tilapia aquaculture in KJA in the waters of Lake Ranau is profitable and feasible for both category I and category II. The profitability value of this KJA farming business is 115% for category I and 119% for category II. The R/C ratio value in one production cycle is 2.15 for category I and 2.19 for category II which means the business is feasible to establish.

Distribution of artisanal fishing gears with impacts on sedimentation and benthic macroinvertebrate assemblages in Songkhla Lake, the largest lagoon in Thailand

The present study investigated the distribution and diversity of stationary fishing gears in Songkhla Lake and assessed the effects of the most abundant gear in the lake, the standing trap, on sedimentation and the abundance of benthic macroinvertebrates. Our survey revealed that six types of fishing gear were used: standing traps, fyke nets, fish aggregating devices, seabass net cages, small traps and stationary lift nets. The type of fishing gear used depended on the depth of water. The density of installed standing traps reached a maximum of 357 traps/km2, which was the highest density of any fishing gear installed on the lake. They were mainly set in the middle part of the lake, where the water was less than 2 m deep. Sedimentation was examined inside and outside the areas influenced by standing traps. Sediment samples were collected with sediment traps in the northeast and southwest monsoon seasons. Sedimentation rates inside and outside the areas influenced by standing traps differed at some sites but the pattern was not consistent across seasons. Sedimentation rates were higher in the northeast monsoon season with the average rate 1132.32 ± 43.73 (mean ± SE) g m−2day−1 when precipitation and run-off were higher and 323.98 ± 10.68 g m−2day−1 in the southwest monsoon or dry season. Moreover, the proportion of finer clay particles was greater in the sediment from the areas influenced by traps. Benthic macroinvertebrate communities between the two areas were different. A bivalve, Potamocorbula sp., which dominated benthic macroinvertebrate assemblages, had a higher abundance in areas influenced by traps. The effects of stationary fishing gears on sedimentation and benthic macroinvertebrates highlighted in this study suggest that the long-term deployment of these gears may affect food chain dynamics in this lagoon system. Ultimately, a proper regulation of the use of these gears may be needed.

Determination of Trophic Status and Floating Net Cages Carrying Capacity in Jatigede Reservoir

Aquaculture activities with floating net cages are essential to increase fishery production. The existence of the fish cages in the Jatigede Reservoir is illegal because it is against local government regulations. However, the people affected by the dam's construction still maintain it for their economic reasons. Therefore, it is necessary to do a research to overcome these problems by determining the carrying capacity of aquaculture and evaluating the trophic status of the waters. However, the people affected by the dam construction still maintain it for their economic reasons. Determination of the carrying capacity of fish farming in the Jatigede Reservoir was conducted using the Beveridge method by calculating the remaining phosphorus still available in the Jatigede Reservoir and evaluating the trophic state index based on three indicators: transparency, total phosphorus, and chlorophyll-a. The sampling was carried out by purposive sampling method. The calculation results show that the condition of the Jatigede Reservoir is eutrophic to hiperthropic with a trophic state index (TSI) value of 66-71. The carrying capacity of the reservoir is 7,140.25 tons of fish/year. The development of cage aquaculture that exceeds the aquaculture carrying capacity in Jatigede Reservoir. Reducing cage aquaculture fish production following its carrying capacity is important to preserve the environment and control eutrophication.

Effects of different shelters on feeding, molting, survival, and growth of Scylla paramamosain

Providing shelters is considered an effective method to prevent self-harm and improve the survival rate of Scylla paramamosain. In this study, four shelter groups—the shelters of which included fine sand, arched tiles, PVC pipes, and trapezoidal net cages—and one group without shelters were established to investigate the effects of shelters on S. paramamosain by calculating their feeding rate, molting rate, survival rate, and growth index. The results showed that the feeding rates of the fine sand and PVC pipe groups were greater than 12% and that the feeding rates of the arched tile and trapezoidal net cage groups were greater than 9%, while the feeding rate of the group without shelters was only 6.7%. The food conversion rates of both the fine sand and PVC pipe groups exceeded 21%. In contrast, the food conversion rate of the non-shelter group was the lowest at 14%. The molting rates of the fine sand and PVC pipe groups were the highest, reaching 29% in the later stages of the experiment, while the molting rate of the non-shelter group was only 19%. There was no significant difference in survival rates among the groups during the first 20 days of the experiment. However, on the 60th day, the survival rate of the fine sand group was 92%, while the non-shelter group had a survival rate of 79%. The experimental results showed that the incidence of cheliped injuries in the fine sand group was 16%, while it was 25% in the non-shelter group. During the daytime, the occupancy rate of burrows by the four shelter groups was 60–70%, while during the night, the occupancy rate of each shelter decreased to 40–50%, and there was no significant difference in occupancy rates among the shelter groups during the night. The weight and full carapace width of S. paramamosain in the fine sand and PVC pipe groups were significantly higher than those in the other groups (P&amp;lt; 0.05), and the weight gain rate and specific growth rate of the fine sand and PVC pipe groups were significantly higher than those of the other groups (P&amp;lt; 0.05). Research has shown that fine sand and PVC pipes, as shelters for S. paramamosain, can effectively prevent cannibalism, increase feeding rates and survival rates, and promote growth and molting. This study provides scientific guidance for the proper selection of shelters in the farming process of S. paramamosain.

Community structure of periphyton at floating net cages and non-floating net cages in Laut Tawar Lake, Aceh Tengah

Many activities are carried out around the Laut Tawar lake, one of which is the cultivation of floating net cages that can contribute nutrients to the waters. One of the organisms that can take advantage of the abundance of nutrients in the waters is periphyton. This study aims to examine the community structure of periphyton as natural food in Laut Tawar Lake. This research was conducted in January-April 2022. The results showed that there are 9 classes of periphyton at the KJA station, namely Bacillariophyceae, Chlorophyceae, Cyanophyceae, Rhizopoda, Dinophyceae, Euglenophyceae, Trebouxiophyceae, Klebsormidiophyceae and Coscinodiscophyceae. While, at non-KJA stations there are 7 classes where the Klebsormidiophyceae class and the dinophyceae class are not found at non-KJA stations. The highest abundance at the KJA station was on the 7th day with a value of 108,655 cells/cm2 and non-KJA was 24,552 cells/cm2. The lowest abundance occurred on day 14 at both stations. Periphyton diversity index at KJA and non-KJA stations ranged from 1.88-2.76, which was moderate. The evenness index of periphyton species ranging from 0.61-0.75 was classified as high, while the dominance index ranging from 0.09-0.24 was classified as low. Based on the values obtained, the community structure of periphyton on artificial substrates in the KJA and non-KJA areas in Laut Tawar Lake experienced moderate ecological stress with the community in a stable condition. The t-test results obtained that the abundance values at KJA stations and non-KJA stations had the difference that the abundance of periphyton at KJA stations was greater than at non-KJA stations.