Fish Cages Research Articles

Persepsi Wisatawan Tentang Daya Tarik Wisata Danau Kerinci

The background of this research is the observation of Lake Kerinci and several negative reviews of tourists about Lake Kerinci found on google reviews, such as fish cages in Lake Kerinci which were established freely and uncontrollably, causing the natural scenery of Lake Kerinci to be disturbed and polluted, accessibility difficulties for tourists who using public transportation, water shortages in public toilets, causing the cleanliness of the toilets to not be maintained, there are still illegal collection activities (Pungli), and the number of trash bins is still small and inadequate, causing a lot of garbage to be scattered along with the absence of cleaners. This research aims to find out what tourists think about the tourist attraction of Lake Kerinci which is reviewed using indicators: attraction, accessibility, amenities and ancillary service. This research is a quantitative descriptive research, The research sample amounted to 82 people from 428 population and used accidental sampling technique. The data was obtained by distributing a structured questionnaire using a Likert Scale. Data analysis used descriptive analysis to categorize respondents' answers. The results of the study stated that the perception of tourists about the tourist attraction of Lake Kerinci is categorized as bad with a percentage of 40%. (1) Based on the attraction indicator, it is categorized as bad with a percentage of 54%. (2) Based on the indicators of accessibility (accessibility) is categorized as sufficient with a percentage of 67%. (3) Based on the indicators of amenities (facilities) are categorized as bad with a percentage of 42%. (4) based on the ancillary service indicator (supporting facilities) it is categorized as bad with a percentage of 34%.

Feasibility study on distributed flow sensing with inertial sensors in aquaculture fish cages

Currents flowing through aquaculture farms are essential to guarantee quality of the produced fish. Water flow through the fish farms transport fresh oxygen in and at the same time, waste out from the cages. Previous studies have shown that the flow speed inside the cages affects the growth rate of the fish and that it is equally important to measure flow conditions outside the farm and inside the cages. We demonstrate the usage of cost effective flow meter, hydromast, as a possible monitoring device for currents inside agriculture fish cages. In this study we validate the hydromast performance in the noisy environment and demonstrate in field experiments, that the device can be used to measure tidal currents online in fish cages with a distributed suspended array.

Оценка влияния выращивания товарной рыбы в садках на экологическое состояние водоема

Growing a large mass of hydrobionts in a limited area (cage fish farming) entails a local increase in the load on the ecosystem from additional organic matter. In connection with the high growth rates of development of cage farms in various open natural water bodies, it is necessary to improve the system for monitoring their impact on aquatic biocenoses. The quality of surface waters and bottom sediments of the Ermakovskiy Bay of the Ust-Kamenogorsk Reservoir has been assessed in the of operation area of the cage farm Shygys, LLP. According to the zooplankton indices, the Pantle-Bukk saprobity index in the modification of Sladechek was used, the oligochaete index was used for macrozoobenthos. The studies were carried out at three stations: 200 m upper the bay (conditionally background station); at the cage line (reflects the local impact of the fish farm on the reservoir); 200 m lower the bay (reflects the overall impact of the enterprise on the reservoir associated with the removal of pollutants). As a result of the research, it was found that before the start 
 of cage fish farm operation the quality of water and bottom sediments at all points of the study corresponded to the “clean” category. A year after the launch of the enterprise a decrease in the taxonomic richness of zooplankton was noted, which indicates a slight deterioration in the quality of surface waters. In the fourth year of cage farm operation the saprobity indices near the cage line grew up to 1.8, and lower the bay - to 1.6, which indicates a local deterioration of the surface waters quality (class III, moderately polluted water). A similar situation is also characteristic of benthic communities of invertebrates. In 2017, at all three research stations, and in subsequent years only at a conditionally background station bottom sediments were characterized as clean. In 2019-2021 the pollution of bottom sediments was on the rise in the cage zone and below the Yermakovskiy Bay. The values of the oligochaete index increased from 14-20 to 58-75%. In 2019, bottom sediments were rated as class IV (contaminated), and in 2021 - as class V (dirty). On the results of the studies there were developed the corrective measures for reducing the anthropogenic load on the open natural reservoir. In the future monitoring the changes in qualitative and quantitative indicators of hydrobionts in the operation area of fish cage farms will allow local monitoring of water quality and timely adjustment of reclamation and fish breeding activities.

A dynamical study on sea waves interaction with an array of circular elastic floaters of aquaculture fish cages

In this paper, linear oblique wave incident to circular elastic floaters of aquaculture fish cages was studied semi-analytically. This work's unique research objectives include considering the array of elastic floaters where each floater consists of two tori with minor differences in their main radii. Hydrodynamic interaction between the inner and outer of each floater body and hydro-elastic interaction between floaters in the array are the particular features of the problem. Using slender body theory and matched asymptotic expansions, each 3D problem was decomposed into two separate, more straightforward problems named near-field and far-field problems. This approach helps derive fundamental solutions for symmetric and antisymmetric motions. Also, using linear wave theory, the diffracted and radiated waves due to the presence of floaters were expressed in Fourier modes of symmetric and antisymmetric motions. Moreover, Graf's and Gegenbauer's addition theorems for Bessel functions are used to shift between different coordinate systems. This approach is helpful to bridge on calculating related integrals numerically. The developed model verification by BEM-based software demonstrates that the model solves the mathematical formulas with enough accuracy. The effect of various parameters such as floater dimensions, wavenumber, the distances between floaters, and the bending stiffness of floater on the floater's motions was studied. The results demonstrate that as the wavenumber increases, the floater's hydro-elastic interaction becomes essential. Furthermore, the upstream floaters do encounter larger wave loads than a single floater in waves.

Sustainable Livelihood through Fish Cage Culture: Case of Chandil Reservoir in Jharkhand

Sustainable Livelihood through Fish Cage Culture: Case of Chandil Reservoir in Jharkhand

An IMTA in Greece: Co-Culture of Fish, Bivalves, and Holothurians

Integrated multitrophic aquaculture (IMTA) is an innovative mariculture methodology that reduces the environmental footprint and increases the profitability of the farm. It combines the cultivation of species belonging to different trophic levels, simulating a natural food web. In this study, five Mediterranean species were co-cultured in three operating fish farms in the Aegean (E. Mediterranean) Sea with different trophic conditions. The co-cultivated species were sea bream (Sparus aurata), European sea bass (Dicentrarchus labrax), Mediterranean mussel (Mytilus galloprovincialis), rayed pearl oyster (Pinctada imbricata radiata), and sea cucumber (Holothuria polii). Bream, bass, and mussels were cultivated according to the traditional on-growing methods (fish cages and longlines), whereas the pearl oysters and sea cucumbers were cultivated in baskets designed specifically for oyster farms. To estimate the growth of the co-cultivated species, growth indicators were calculated using length and weight measurements. Furthermore, the growth measurements from co-cultivated species were compared to the respective ones from natural populations. All the species showed high survival rates in the integrated multitrophic aquaculture (IMTA) conditions. Pearl oysters and Mediterranean mussels had positive growth in fish farms with high concentrations of nutrients. Mussel condition index (CI) was 42% in Aquaculture 1 (Aq1) and 33% in Aquaculture 2 (Aq2), compared to 35% in a typical Mediterranean mussel farm. Pearl oysters CI in Aq1 was 53%, in Aq2 56%, in Aquaculture 3 (Aq3) 19%, and in natural populations ranging from 30% to 45%. In contrast, holothurians did not gain weight under the fish cage regime despite the high survival rate. Their final total weight was 17.3 g in Ag1, 8.3 g in Aq2, and 18.3 g in Aq3, but in the natural population, the mean weight was 80 g.

Reliability assessment of mooring system for fish cage considering one damaged mooring line

The reliability of the mooring system considering one damaged mooring line should be assessed for evaluating the risk resistance capacity of the mooring system for the offshore aquaculture farm. In this study, both the probability of failure under the accidental limit state (ALS) and the probability of progressive failure of the mooring system for the fish cage are investigated. A series of numerical simulations were carried out to analyze the redistributed tension response of the mooring system after one mooring line fails. And the reliability of the mooring system under ALS is predicted based on the generalized probability density evolution method. In addition, an improved method based on a series of realistic failure scenarios is proposed to estimate the progressive reliability of the mooring system for the fish cage. The results indicate that the failure of one mooring line significantly affects the probability of failure of the remaining mooring lines and the probability of failure of the mooring system is overestimated by the traditional reliability method without considering the progressive failure of the mooring system. Therefore, it is of paramount importance to quantitatively assess the system reliability of the offshore fish farm considering the progressive failure.

Experimental study of flow and mass transport in the near-wake region of a rigid planar metal net panel

Aquaculture cages constructed from rigid material have become increasingly popular in recent years due in part to the continuous expansion of the aquaculture industry offshore, where cages need to withstand much harsher ocean conditions. Most previous studies of hydrodynamic interactions with aquaculture cages have explored the impacts of more traditional flexible cage net panels on wake flow fields and mass transport properties. In the current experimental study, Particle Image Velocimetry and Planar Laser Induced Fluorescence techniques were used to measure flow and concentration fields in the near wake region of a steady current through a rigid metal net panel to analyze both the flow patterns and mass transport processes. The results indicated that, similar to a flexible polyethylene net panel, the time-average velocities and turbulence characteristics in the near wake region were highly inhomogeneous and anisotropic, with the turbulent intensity following a short-range, power-law decay downstream of the panel. In direct comparison with a flexible net panel of similar net solidity, the rigid net panel was found to slightly enhance the lateral spreading of the plume, with cross-sectional profiles of the mean concentration and concentration fluctuation shown to exhibit self-similar Gaussian distributions. The rigid net panel also resulted in a lower flow blockage, as measured by a velocity reduction coefficient, with the corresponding turbulent intensity also reduced compared to the flexible panel due to an overall reduction in the drag force. In addition, the rigid panel tended to create larger wake eddies than the flexible panel, leading to enhanced scalar mixing and, hence, faster rates of concentration decay in the near-wake region. These experimental findings have potential implications for cage-based aquaculture operations, where rigid fish cages are comparatively more likely to generate favorable environments for fish growth, as well as helping to reduce negative impacts on the surrounding aquatic environment.

Sustainable Livelihood for Displaced Rohingyas and Their Resilience at Bhashan Char in Bangladesh

The livelihood sustainability of the Rohingya refugees relocated in Bhashan Char, Bangladesh, has been questioned by various international stakeholders due to the remoteness and perceived vulnerabilities of the island. The Bangladesh government, a few international organizations, and some non-government organizations are working on developing livelihood opportunities in there. But there is scarce study about the livelihood opportunities and challenges of the Rohingyas living there. This study explores the vulnerabilities and livelihood opportunities of Rohingyas in Bhashan Char so as to help increase their resilience. The vulnerabilities include natural, geographical, and climatic shocks and stresses (e.g., cyclone, floods, storm surge, sea-level rise, geographical position). However, there are ample opportunities for their livelihood development, despite some challenges which can be overcome with concerted efforts. The opportunities include intensification and extensification of livelihood activities, such as modern agriculture, fish farming, livestock rearing, small business, handicraft, fishing net mending, crab fattening, biofloc aquaculture, and fish cage culture, but turning these opportunities into reality requires sufficient investment and internationally positive attitude. Better shelter, better disaster preparedness, cultural practices, education, and skill development can increase their capacity to bounce back, absorb shocks, and make them more resilient. National and international humanitarian organizations should plan to enhance the resilience of the Rohingya communities living in Bhashan Char and the island itself so that they can sustain in the long run, even after their anticipated repatriation to Myanmar.

Modelling torus behaviour in a fish farming cage

AbstractSince it is not usually possible to observe all of the fish in a school, it is difficult to monitor farmed fish in a crowded cage with the aim of scrutinising their condition. One possible solution to this problem is the use of simulations. The aim of this study is to simulate fish movement in a cage to be able to propose an optimal monitoring method based on limited observations made by instruments. In this study, we observed a Yellowtail (Seriola quinqueradiata) school in a fish cage at a fish farm and attempted to simulate their movement. The Yellowtail, while milling in a cage, forms a stable truncated cone‐shaped school. We successfully reproduced this shape of school by including the effects of negative phototropism and the hypothetical forces that fish experience from the cage wall, in addition to the forces of attraction, repulsion and orientation that have been postulated in previous studies. We also included the effect of intraspecific interaction. We hypothesise that longer fish exert a greater repulsive force on smaller fish. The results of our simulation suggest that the position of any fish in a school is thus a function of its length.

Plankton Diversity In The Labuhanbatu Bilar River

The purpose of this study was to determine the plankton diversity index in the Labuhanbatu Bilah River. The research was carried out from January to March 2023 using the Purposive Random Sampling method which consisted of 3 observation stations, namely station 1. There were many community activities such as Domestic Waste, Sand Mining, Agriculture, Station 2. There was Domestic Waste, Cage Fish Farming and Agriculture. and Station 3. There are community activities such as bathing, domestic and agricultural waste. The results of the study found that the plankton composition in the Bilah Labuhanbatu River consisted of 3 classes of phytoplankton, namely Bacillariophyceae, Chlorophyceae and Cyanophyceae while the class of zooplankton consisted of 4 classes, namely Mastigophora, Monogononta, Crustacea and Ciliophora. The highest diversity index of phytoplankton was obtained at station 1 of the sand mining area with a value of 1.76 indicating that the level of diversity was included in the medium category. In zooplankton the highest diversity index was found at station 3 with a value of 0.42 which indicated that the level of diversity was included in the low category. Meanwhile, the highest dominance index for phytolactones was found at station 3 in a densely populated area with a value of 0.51, while for zooplankton it was found at station 1 in a sand mining area with a value of 0.00487, both values ​​indicating that no plankton genus dominates in the area. In zooplankton the highest diversity index was found at station 3 with a value of 0.42 which indicated that the level of diversity was included in the low category. Meanwhile, the highest dominance index for phytolactones was found at station 3 in a densely populated area with a value of 0.51, while for zooplankton it was found at station 1 in a sand mining area with a value of 0.00487, both values ​​indicating that no plankton genus dominates in the area. In zooplankton the highest diversity index was found at station 3 with a value of 0.42 which indicated that the level of diversity was included in the low category. Meanwhile, the highest dominance index for phytolactones was found at station 3 in a densely populated area with a value of 0.51, while for zooplankton it was found at station 1 in a sand mining area with a value of 0.00487, both values ​​indicating that no plankton genus dominates in the area.

Identifying pollution sources of sediment in Lake Jangseong, Republic of Korea, through an extensive survey: Internal disturbances of past aquaculture sedimentation

Lake sediments are important sinks of various pollutants and preserve historical pollution records caused by anthropogenic activities. Recently, the sediments of Lake Jangseong, South Korea were first detected with high concentrations of organic matter (ignition loss [IL]; total organic carbon [TOC]), nutrients (total nitrogen [TN]; total phosphorus [TP]), and some heavy metals (Zn, Cu, Cd, and Hg). Here, we identified the origins of these concentrations accumulated in the sediments using extensive surveys and various assessments. Sediment pollution assessed by sediment quality guidelines, pollution load index, and potential ecological risk index was found to be of serious concern for IL, TN, TP, and Cd. Thus, we assessed pollution sources through spatial, grid, and vertical distributions and found that the high pollutant concentrations detected in 2020 were confirmed only at a certain location in the lake. Additionally, similar results were detected in the sedimentary layer below a sediment core at a depth of 15.0 cm. The high pollutant concentrations locally occurred around a “hotspot” site that was previously frequently used for aquaculture activities, indicating that the pollutants were accumulated in sediments owing to past cage fish farming rather than from influx of externally sourced pollution. Furthermore, chemical fractionation of phosphorus and heavy metals and assessment of stable isotopes (13C and 15N) of organic matter suggested that the pollutants in the sediments at the “hotspot” sites had different origins than those found at other sites. Accordingly, the by-products discharged after cage fish farming, such as residual feed, fish meal, and waste, accumulated in the sediments and were then exposed to natural internal disturbances caused by the effects of climate change-induced drought. This local distribution and the phosphorus and heavy metal chemical fraction results with low elution potential indicated that the pollutants in the sediments of Lake Jangseong had negligible impact on water quality.

Assessment of social acceptance of caged fish culture for improvement and sustainability: A study on Volta Lake, Ghana

Acceptance of cage fish farming within Volta Lake in Ghana, was assessed in the lake’s riparian sub-communities by estimating opinion case of community members generally and specifically on issues including Interference of fish culture with fishing; Cage culture interference with local boat transportation activities; Integration level of cage fish culture into other lake activities; Awareness of lake’s community of the lake as a multipurpose resource; Primary occupation of community members; Co-existence level of fish farm operators and communities and cumulative acceptance of fish culture compared to other lake uses and users currently and in the future when the lake is zoned. Methods used were Formal survey and Focus Group Discussions (FGD) in two conceptualized zones (Afram Plains and Asuogyaman) of the lake and data was analyzed by SPSS. A study was undertaken to enhance integration and acceptance of cage fish culture into activities on the Volta Lake and by extension on potential other water bodies where cage fish culture might be practiced. Results indicated that several mutually beneficial situations existed between cage fish farming operators and lake communities. However, there were also conflict flashpoints between cage fish farming practices and livelihood activities of communities at some places as well as fish culture-related outcomes, such as effluents of the culture on lake water quality for communities. The benefits of cage fish farming to communities observed in the results confirm some previous reports. Suggestions of communities to the resolution of conflict flashpoints of operations with operators of cage fish farming provide avenues for enhanced integration thus acceptance and sustainability of cage culture in riparian communities of the lake and other water bodies that could be found suitable for cage fish culture.

Effect of smoking and chargrilling on toxic metal(loid) levels in tilapia from the Afram Arm of the Volta Lake

ABSTRACT This study assessed the effect of smoking and chargrilling on arsenic (As), cadmium (Cd), mercury (Hg), and lead (Pb) levels in tilapia from cage farm and wild of the Afram Arm of Lake Volta in Ghana. Method of assessment was an Inductively Coupled Plasma - Mass Spectrometer. Culinary methods did not affect Cd levels in anyway, likewise Pb in cage fish. Wild fish Pb levels decreased significantly (p < 0.05) from raw (0.013 ± 0.004 mg/kg) after smoking (0.0077 ± 0.0007 mg/kg), and chargrilling (0.006 ± 0.0004 mg/kg). Raw As levels (wild: 0.0325 ± 0.0007 mg/kg, cage: 0.0478 ± 0.0009) increased significantly by smoking (wild: 0.064 ± 0.002; cage: 0.0104 ± 0.006). Smoking introduced Hg (0.005mg/kg) in wild samples. Chargrilling significantly increased As levels in cage fish (0.072 ± 0.004). These contaminants were always below the maximum permissible consumption levels. The CR of As was below the threshold (10-4) likewise THQ and HI below (1), hence consuming tilapia from study site either smoked or chargrilled is safe.

Status of fish health management and biosecurity measures in fish farms, cages and hatcheries in Western Kenya

BackgroundAquaculture is one of the critical sectors contributing to food and nutrition security, income and employment opportunities to millions of people, and is currently the fastest growing food-producing sector globally. With the global increase in aquaculture production, focus on biosecurity and fish health management is becoming increasingly important to address the risks and impacts of aquatic diseases. Within the framework of adaptive research, this study aimed at assessing the levels of awareness and preparedness of fish farmers in Western Kenya to meet fish health management and biosecurity requirements as important parameters determining the success of their farming activities.MethodsA total of 504 fish farmers were interviewed using a pre-tested questionnaire generated by a computer-aided personal interview (CAPI). The data collected was summarized using descriptive statistics using SPSS version 25. The homogeneity of frequency data of all the parameters between the three counties was tested using a non-parametric Pearson Chi-Square test at α = 0.05.ResultsThe key findings were that 76.1% of the fish farmers reported mortalities in their farms, with 2.3% reporting mortalities above 50% of the stocked fish, but with a majority (85.5%) reporting loss of up to 10%. In extrapolation, the total loss from the farms correlates with stagnation in aquaculture production in Kenya.ConclusionsThis study concludes that there is a paucity of knowledge on fish health management systems and biosecurity measures which presents a serious threat to aquaculture production in the studied counties and poses a great risk to trans-boundary live fish trade between Kenya and her neighbouring countries. Although fish farming is a promising area, it has had so many challenges among them high mortality rates. In China and other Asian countries, which are the world leaders in aquaculture production, they are making headway in fish health management and biosecurity. This study recommends the development of a coordinated awareness campaigns on fish health management and biosecurity measures to fish farmers in Kenya.

Lipid composition of oocytes and tissues of sturgeons depending on conditions of detention

Shortage of sturgeon spawners has led to the need for reservation and long-term detention of spawners, creation of their own brood stocks. The issues of assessing the functional state of producers and the reproductive products and offspring become topical. The wintering conditions of fish in cages at the natural course of temperatures negatively affect their physiological state. During this period, the fish actively move in the cages, but do not feed. The detention of sturgeon spawners in the pools with regulating the parameters of the aquatic environment makes it possible to stabilize the cycle of maturation of the gonads and increase the number of fish-producing females. The lipid composition of caviar affects its fish-breeding quality. The main components of sturgeon caviar fats are triglycerides and lipoid substances, which are represented by phospholipids that are actively involved in generative metabolism during the maturation of gonads. The main fraction of oocyte lipids is represented by triglycerides, whose level in the oocytes of fish from recirculating water installation (RWI) is higher in comparison with cage fish. It was found that sterlet oocyte lipids are mainly represented by triglycerides. Their concentration in the oocytes of fish kept in RWI is higher in comparison with fish kept in cages. Against the higher amount of triglycerides in fish roe from RWI, a decrease in the level of phospholipids and cholesterol was noted. The aging conditions of producers affect the composition of the main lipid fractions. As a result of the research, a relationship was established between the content of polyunsaturated fatty acids in the tissues of aquatic organ-isms and environmental conditions. The amount of saturated and monounsaturated fatty acids in the muscles of fish kept in RWI was higher than in the tissues of fish kept in cages. Increasing proportion of polyunsaturated fatty acids in the eggs of fish kept in cages indicates a fairly high utilization of monounsaturated fatty acids.

Interpretative Structural Modeling Dalam Analisis Kelembagaan Pengendalian Kualitas Air Waduk Sutami

The Sutami Reservoir, located in Malang Regency, East Java, has moderate to severe levels of pollution. This pollution problem can reduce the water quality of the Sutami Reservoir, so it requires coordination from the agencies concerned to formulate water pollution control policies. The management agency for the Sutami Reservoir is the ‘Perum Jasa Tirta 1’ (PJT 1). The institutional analysis applied is the Interpretative Structural Modeling (ISM) method, to find out which agencies are key elements/factors. There are eleven agencies analyzed. Agencies that are included in the ‘Dependent’ sector are the Water Resources Public Works Office, the Tourism and Culture Office, the Livestock and Animal Health Office, the Population Control and Family Planning Office, and the rice farmer groups. Institutions in the ‘Linkage’ sector are the Food Crops, Horticulture, and Plantations Office and the Industry and Trade Office. Institutions in the ‘Independent’ sector that play a key role are the Environment Office, the Fisheries Office, Balai Besar Wilayah Sungai Brantas, and the floating net cage fish farmer group. These four agencies are the key elements that have a big driving power so that more in-depth coordination needs to be carried out for the formulation of policies and regulations for water quality control.

Ecotoxicological Assessment of Water and Sediment in Areas of Taal Lake with Heavy Aquaculture Practices Using Allium cepa and Daphnia magna Assay

Aquaculture is one of the main livelihoods of people living near Taal Lake. However, the quality of the lake is deteriorating due to the increasing number of fish cages and fish pens. In this study, ecotoxicological assessment of water and sediment in three areas (Gonzales, Bañaga, and Balakilong) of Taal Lake were conducted using Allium cepa and Daphnia magna assay. The result of A. cepa assay showed that areas with heavy aquaculture practices have a higher percentage of chromosomal aberrations (CAs) such as anaphase bridge, precocious chromosome, sticky chromosome, C-mitosis, and micronucleus (MN). This indicates the presence of cytotoxic and genotoxic compounds in the lake water. On the other hand, assessment of sediment samples using D. magna assay showed that the population exposed to samples from areas with heavy aquaculture practice showed a significantly lower number of offsprings compared to the control area. The result of our study shows the effectiveness of the two bioassays on the evaluation of ecotoxicity of water and sediment samples.

Is Holothuria tubulosa the golden goose of ecological aquaculture in the Mediterranean Sea?

The use of detritivores under sea farms is a promising avenue to mitigate the benthic impacts of marine fish farms. Sea cucumbers are interesting candidates for integrated multi-trophic aquaculture (IMTA) due to their prevalence in the marine environment, their diversified diet and their economic value. Yet limited information is available regarding their capacities to be stocked and reared underneath aquaculture cages and the associated effects on their survival, growth rate and body composition. This study focused on Holothuria tubulosa, a Mediterranean sea cucumber species candidate for rearing in the vicinity to marine fish cages. We investigated its potential for co-culture on the seabed more or less influenced by marine fish cages. The farm's waste footprint was predicted using a dispersion model (NewDEPOMOD) to estimate the farm's influence along a transect where we also sampled sediment at four distances from the cages (0 m, 25 m, 100 m from the cages, plus a reference site at 150 m). Organic composition of the sediment was analysed (TOC, TON, TOP, OM, stable isotope signature) and linked to the results from the dispersion model. Based on the model simulation, the maximum flux of matter reached almost 17 kg solids.m−2.year−1 below the cages, and gradually decreased with distance from the cages. An isotopic gradient was also found in the sediments according to the distance from the farm, with an enrichment in δN15 and a depletion in δC13 with increasing proximity to the farm. In parallel we investigated the response of adult sea cucumbers placed at varying distances from the fish cages for a period of one month, measuring their proximate composition, isotopic concentration, and fatty acid and protein composition. We found that despite good survival, growth was null over the experiment. While the isotope signature of the sea cucumbers was significantly affected by distance from the cage, this did not follow the pattern found in sediment. There was a clear difference in fatty acid composition between sites, with sea cucumbers closer to the cages having lower levels of short-chain fatty acids. The protein content was also lower in sea cucumbers reared right below the cages. These results suggest that while adult H. tubulosa can survive the environmental conditions below marine aquaculture cages, they do not nutritionally benefit from fish waste over short periods in the stocking conditions we tested. Their use in IMTA requires further investigation to find optimal stocking conditions.

Sustainability Assessment of Marine Aquaculture considering Nutrients Inflow from the Land in Kyushu Area

The nutrient load generated by excessive aquaculture farms leads to self-pollution around water, which destroys aqua-environment, and further leads to a decline in aquaculture production. The purpose of this study is to propose an index to assess the sustainability of inshore aquaculture in Kyushu area, considering nutrient loads from land and farms. The number and size of fish cages identified from Google satellite imagery are used to calculate annual fish production, which is then converted into annual loads of total nitrogen and total phosphorus. The pollutant load factor method is applied to calculate the land nutrient inflow. An index, including nutrient load from land and farms, bay area, water depth and distance from farms to bay, is proposed. The results show that for most of the cultured bays in Kyushu, the nutrient load from the farm is more than that from the land inflow. The bay with higher index value has a higher possibility of red tide occurrence and lower sustainability for aquaculture. Among which, location of fish farms, total nitrogen and total phosphorus loading are key factors impacting water quality within the bays.