Marine Cage Research Articles

Carbon footprint of fresh sea cucumbers in China: Comparison of three aquaculture technologies

Facing China's strict greenhouse gas (GHG) emission reduction policy including the Carbon Peaking and Carbon Neutrality Goals, the GHG emissions from sea cucumber aquaculture have been attracting increasing attention. In order to promote the low-carbon development of marine aquaculture, this study provides a comparative evaluation of the carbon footprint of 1 t fresh sea cucumber production from cradle-to-gate based on three different aquaculture technologies: marine bottom-sowing aquaculture, marine cage aquaculture, and pond bottom-sowing aquaculture. The hotspots of GHG emissions at key stages of sea cucumber aquaculture are also analyzed. The results showed that the carbon footprint of 1 t of fresh sea cucumber production varies based on different aquaculture technologies, with marine bottom-sowing aquaculture technology having the highest carbon footprint at 6936.5 kg CO2eq, followed by marine cage aquaculture technology at 5148.7 kg CO2eq and pond bottom-sowing aquaculture technology at 2914.1 kg CO2eq. When comparing the GHG emissions of different stages, the growing seedling stage is the hotspot of marine bottom-sowing aquaculture technology, with the main sources of GHG emissions being electricity used for maintaining suitable water temperature and bait preparation. The hotspots of marine cage aquaculture technology and pond bottom-sowing aquaculture technology are both centered around the adult sea cucumber feeding stage, where bait consumption becomes the primary source of GHG emissions. Sensitivity analysis indicates that increasing seedling survival rates, reducing electricity consumption, and implementing renewable energy sources such as solar and wind power can effectively mitigate the GHG emissions associated with sea cucumber aquaculture.

A Case Study on Economic Analysis of Sea Cage Farms in the Black Sea, Türkiye

The main aim of this research is to understand the value chains of enterprises engaged in aquaculture in sea cages in the Black Sea region of Türkiye, to determine production costs and to make a general analysis of the aquaculture sector. Random sampling method was used to ensure that farmers were equally represented in the survey. Data for the survey were randomly selected from 16 separate farms spread throughout 4 different marine cage locations. Furthermore, fish traders and sector stakeholders were interviewed. The businesses examined within the scope of the study are divided into 3 groups: small (250 -500 tons/year), medium (501-999 tons/year) and large (>1000 tons/year), according to their capacities. The most important expense items of enterprises consist of variable costs. Among the variable costs, the purchase of fry fish, feed purchase, and labor costs constitute the most important expenditure items. Among the fixed costs, the most important expense is depreciation costs. The unit cost of one kg of fish varies between 2.7 and 3.0 euros. Considering that the trout (Oncorhynchus mykiss) and seabass (Dicentrarchus labrax) in the Black Sea are at the level of 3.5 Euro, the profit rate of the enterprises is between these levels. Recently, since trout from the Black Sea has been exported to the Far East Country (particularly Japan), its price has also increased. In 2018, the average retail price (including VAT) and medium selling price of seabass and trout were at a level of 5.24 and 5.34 Euros respectively. Despite all these positive developments, climate change continues to pose a threat in terms of disease outbreak and marketing problems.

Adsorption of metals on aged microplastics in intensive mariculture areas: Aggravating the potential ecological risks to marine organisms

Field determination of the metal adsorption capacity of microplastics (MPs) by using a passive sampler had been done in typical subtropical mariculture area in China. The adsorption of eight metals (Fe, Mn, Cu, Zn, As, Pb, Cr and Cd) by five types of MPs (low-density polyethylene, polypropylene, polystyrene, poly(ethylene terephthalate) and poly(vinyl chloride) (PVC) was compared, including metal types, mariculture types (cage and longline culture), metal residue content in ambient environment, polymer types and particle sizes of MPs. The results showed that Cu, Zn, As, Cd, Pb and Cr in the mariculture environment were contaminated compared with the quality criteria. The concentrations of these six metals adsorbed on five MPs increased linearly with those in seawater. More enriched Cu and As in MPs in marine cage culture than in longline culture, due to the obvious endogenous pollution emissions for the artificial diets, fish medicine and disinfectants. Aged PVC with more cracks and pores showed higher metal adsorption capacity than any other polymers. MPs with a smaller size range of 50–74 μm tended to accumulate higher amounts of metals than those with a larger size range of 74–178 μm, consisting with the surface characteristics of MPs. The significant positive relationship between the concentrations of nutrients in seawater and the adsorption amounts of Cu, Zn and As on MPs implies that the eutrophication would promote their pollution. Based on the ecological risk assessment, the occurrence of MPs could aggravate the potential risk of metals to marine organisms in intensive mariculture areas. This is the first time to reveal the impacts of the adsorption of metals on aged MPs on the potential ecological risks of metals to organisms under the realistic environmental condition.

Improvement of Immune Defense and Survival of Grouper Fish (Ephinepelus sp.) Using the Immuno-Probiosirkulasi System (SI-PBR) Method in Semi-Intensive Ponds in Brondong, Lamongan

Grouper (Epinephelus sp.) is a marine fishery commodity that is widely cultivated in marine cages and ponds. The export market demand for grouper fish continues to increase every year by 30.75% every year, so there is a need for improvement, through various technological applications. The main obstacle in cultivating grouper fish in ponds is the decline in water quality and disease attacks, which can cause up to 100% crop failure, just 3 – 5 days after infection. One effort that can be implemented is the cultivation method with the Immuno-Probiocirculation System (SIPBR). Brondong sub-district is one of the areas in Lamongan which has large fisheries potential, especially for breakwater water pools, which are the top among other districts. There have been many cases of grouper deaths in ponds to date, which are caused by disease attacks and water quality. The aim of this community service activity is to apply the Immuno-Probioculation System fish aquaculture technology in traditional plus pattern ponds (SI-PBR), increasing grouper fish production in Lamongan Regency, East Java. Observational method which includes socialization / counseling, planning and guidance for implementing SI-PBR technology in one period (three months). These results show positive indications. There is an increase in farmer knowledge, the SI-PBR method can reduce ectoparasite infestation and increase grouper yields from 272.43 kg / ha to 87.66 kg / ha, meaning an increase of 334%. The conclusion from this activity is that the SI-PBR model can increase fish production and can be applied in wider areas in the Lamongan region.

Morphological characterization and transcriptome analysis of opercular deformity in golden pompano (Trachinotus ovatus)

Skeletal deformity is one of the major threats to aquaculture because of its negative effects in important economic losses. Recently, a high rate of opercular deformities was observed in farmed golden pompano (Trachinotus ovatus), which is a key species for marine cage culture in the South China Sea. In the present study, a structural, histological, and biochemical analysis of the deformed opercular complex in T. ovatus was carried out using micro-CT, Inductively Coupled Plasma Mass Spectrometry (ICP-MS), paraffin section, and staining. A 3D reconstruction of the deformed and normal opercular complex has revealed an inward folding of both opercle and subopercle, and frequently affected branchiostegal rays being coated by the deformed opercle and subopercle. In addition, an increased Ca, P, and Mg content was identified in the deformed opercle. The Hematoxylin-eosin (HE) and tartrate resistant acid phosphatase (TRAP) staining of the deformed opercle have shown a higher osteoclast activity and increased bone resorption area. Further analyses on the difference of gene expression between the deformed and normal opercle have been performed using Illumina sequencing platform. As a result, a total of 1220 DEGs (including 508 up-regulated and 712 down-regulated genes) were identified. DEGs related to osteoblast and osteoclast differentiation revealed an important role of bone metabolism in opercular deformity. Moreover, GO and KEGG analysis of these DEGs showed that they were significantly enriched in functions and pathways related to muscle form, development and contraction. Additionally affected pathways including ion homeostasis suggested that functions of gills such as breathing and osmoregulation might be affected by the deformed opercle.

Development of a Technological System of Floating Cages in the Sea for the Farming of Marine Fish Within the Coastline of ILO

The objective of the research work is to develop a technological system of floating cages in the sea for the culture of marine fish within the coast of Ilo. The research method is experimental, applied approach, the process is constituted by a marine cage system which includes the analysis of climatic conditions, oceanographic conditions, legislation, adequate environment and conditions suitable for the development of the project; to then design the prototype to operate the floating sea cage. The preliminary results through the study "Development of technical capacities for the cultivation of Corvina "Cilus gilberti" in the province of Ilo, Moquegua Region" through which the culture cages were installed approximately 1.2 km from the coast in front of the beach "Piedras Negras" north of Ilo in which juvenile corvina were planted. The design and construction of the marine cage for fish culture was appropriate because the materials used are in the optimal quality range, after submitting them in the simulations; you have fish in preliminary growth in the marine cages designed and built for fish culture; and finally, the maintenance of the cages was technically manageable, because it allows periodically its evaluation and maintenance.

Cage aquaculture of Indian pompano for livelihood diversification of artisanal fishers: Insights from Andhra Pradesh, India

Artisanal fishers fishing in nearshore coastal waters off Visakhapatnam using motorisedcrafts and in estuaries of Krishna using non-motorised crafts were selected for the study.Their annual net operating income varied between US$ 469.63 (₹39,040) and US$ 2698.42(₹2,24,320), respectively. Inspired by the potential of cage farming from the frontlinedemonstrations in marine and estuarine waters and after acquiring appropriate skills,15 individuals from the Traditional Fishermen’s Co-operative Society, Visakhapatnamand 76 individuals from Yanadri Girijana Matsya Sakhara Sangam, Krishna embarked oncage aquaculture of Indian pompano in 15 and 70 cages, respectively. Marine cages werecircular (6 m diameter) and estuarine cages were square (5 m X 5 m), and were stockedwith hatchery-produced Indian pompano (Trachinotus mookalee) fingerlings of 22.6 gweight @ 2500 and 1500 numbers respectively, and were fed with floating pellets at 8-3% ofbiomass. Average body weight, survival and biomass production from marine and estuarinecages after eight months of culture were 843 and 666 g, 96.28 and 91.47% and 2029.0 and913.85 kg respectively. Deducting all capital and operational expenses, annual net operatingincome per unit ranged from US$ 1247.44 (₹1,03,700) to US$ 2632.02 (₹2,18,800); whichrepresented a substantial increase from that of capture fishery. Cluster-cage farming, asadopted, did not adversely impact the water and sediment quality. The current researchoffers novel insights into the bio-growth and economic factors pertinent to commercial cagefarming of Indian pompano. Cage farming in marine and estuarine conditions holds a greatpromise as an alternative source of livelihood for artisanal fishers, thereby bolstering theireconomic sustainability. Keywords:Cage farming, Gross revenue, Indian Pompano, Netoperating income, Small scale fishers

Swimming behavior as a potential metric to detect satiation levels of European seabass in marine cages

Aquaculture is anticipated to contribute to two-thirds of the world’s fish consumption by 2030, emphasizing the need for innovative methods to optimize practices for economic viability, social responsibility, and environmental sustainability. Feeding practices play a pivotal role in aquaculture success and the feeding requirements are dynamic, influenced by factors like fish size, environmental conditions, and health status necessitating ongoing improvements in feeding practices. This study addresses a critical gap in feeding control systems in sea cages. It introduces a continuous, real-time monitoring system for analyzing the feeding behavior of European seabass, employing advanced AI models (YOLO and DEEPSORT) and computer vision techniques. The investigation focuses on key parameters, including speed and the newly defined feeding behavior index (FBI), to evaluate swimming responses under varying feeding scenarios exploring meal frequency, feeding time, and feeding quantity. The findings reveal a sensitivity of fish speed and the feeding behavior index (FBI) to different feeding scenarios, elucidating distinct behavioral patterns in response to varying frequencies, times, and quantities of feeding, such as increased activity in the morning relative to later times and the emergence of asymmetric activity patterns when fish are underfed or overfed. Notably, this study is one of the few in the field, presenting the development of a continuous, real-time monitoring system for feeding control in sea cages. Simultaneously, it explores reference curves and threshold values to enhance the overall efficacy of feeding control measures.

Coinfection of Cage-Cultured Spotted Sea Bass (Lateolabrax maculatus) with Vibrio harveyi and Photobacterium damselae subsp. piscicida Associated with Skin Ulcer.

Spotted sea bass (Lateolabrax maculatus) is a high-economic-value aquacultural fish widely distributed in the coastal and estuarine areas of East Asia. In August 2020, a sudden outbreak of disease accompanied by significant mortality was documented in L. maculatus reared in marine cage cultures located in Nanhuang island, Yantai, China. Two coinfected bacterial strains, namely, NH-LM1 and NH-LM2, were isolated from the diseased L. maculatus for the first time. Through phylogenetic tree analysis, biochemical characterization, and genomic investigation, the isolated bacterial strains were identified as Vibrio harveyi and Photobacterium damselae subsp. piscicida, respectively. The genomic analysis revealed that V. harveyi possesses two circular chromosomes and six plasmids, while P. damselae subsp. piscicida possesses two circular chromosomes and two plasmids. Furthermore, pathogenic genes analysis identified 587 and 484 genes in V. harveyi and P. damselae subsp. piscicida, respectively. Additionally, drug-sensitivity testing demonstrated both V. harveyi and P. damselae subsp. piscicida exhibited sensitivity to chloramphenicol, ciprofloxacin, ofloxacin, orfloxacin, minocycline, doxycycline, tetracycline, and ceftriaxone. Moreover, antibiotic resistance genes were detected in the plasmids of both strains. Extracellular product (ECP) analysis demonstrated that both V. harveyi and P. damselae subsp. piscicida can produce hemolysin and amylase, while V. harveyi additionally can produce caseinase and esterase. Furthermore, infected fish displayed severe histopathological alterations, including infiltration of lymphocytes, cellular degeneration and necrosis, and loose aggregation of cells. Artificial infection assays determined that the LD50 of P. damselae subsp. piscicida was 3 × 105 CFU/g, while the LD50 of V. harveyi was too low to be accurately evaluated. Furthermore, the dual infection of V. harveyi and P. damselae subsp. piscicida elicits a more rapid and pronounced mortality rate compared to single challenge, thereby potentially exacerbating the severity of the disease through synergistic effects. Ultimately, our findings offer compelling evidence for the occurrence of coinfections involving V. harveyi and P. damselae subsp. piscicida in L. maculatus, thereby contributing to the advancement of diagnostic and preventative measures for the associated disease.

Impact of Dead Fish Degradation on the Monitoring of Fish Losses in the Pregrowing and Growing Phase of Caged European Sea Bass (Dicentrarchus labrax)

The interplay between environmental, biological, and physical factors often leads to the deterioration of dead fish in marine cages prior to their removal. Depending on the weight of the dead fish and the frequency of their removal, deterioration can progress to a stage where visual identification by divers becomes challenging, thereby disrupting accurate counting of dead fish. This study presents a practical precision tool for monitoring the number of dead fish during the pregrowth and growth phases of caged European sea bass (Dicentrarchus labrax). To improve the assessment of collected mortality, experiments were conducted in farming cages with various fish weights. Identifiable fish rates (I, %) were calculated every 24 hr and classified into four weight classes: WC1 (4–15 g), WC2 (15–30 g), WC3 (30–80 g), and WC4 (>80 g). The corrected number of dead fish (M) was calculated by dividing the collected number (C) by a correction factor (McR), which was determined based on the adopted removal frequency. The possible mortality removal frequencies per week (Fn) included operations such as F7 (daily), F3 (3 times), F2 (2 times), and F1 (once). The smallest correction denominator was 22% for WC1 at a frequency of once per week, whereas the maximum was 100% for WC3 and WC4 daily. The results revealed a high negative significant correlation between Fn and uncollected degraded fish rate (UR) (r = –0.841, p < 0.05). Applying corrections to mortality collected in three finished batches (B2, B3, and B7) led to an increase in the mortality rate by 3.9% ± 1.5%, 5.5% ± 0.7%, and 5.0% ± 0.5%, respectively. This explained 16.8% ± 4.7%, 65.5% ± 26.7%, and 30.3% ± 3.7% of fish disappearances in B2, B3, and B7, respectively. The significance of this study lies in its practical applicability to fish farms as a precise tool for monitoring fish raised in marine cages.

Mapping of potential sea-cage farming sites throughspatial modelling: Preliminary operative suggestionsto aid sustainable mariculture expansion in India

Sea cage farming in marine open waters is considered as the most viable technique in Indianmariculture to enhance production. Owing to the support of the government in researchand development, and policy initiatives, marine cage farming is progressing steadily in thecountry. Technological guidance from research institutions and financing under the ambitious“Pradhan Mantri Matsya Sampada Yojana (PMMSY)” and blue growth mission objectives haveinspired stakeholders and fisheries administrators in maritime states to explore open seacage culture. Site selection is a key parameter affecting the success of cage culture systemsand, technically analysed geo-referenced demarcation of spatial information is necessaryfor minimising the risks. Thus, in the light of rising demand for spatial allocation of coastalareas, the present study identifies and aggregates locations within 3 km of the coastline,that have the potential for sea cage farming operations in the country. The site suitabilitywas examined based on optimal standards required for the prospective candidate speciesselected for mariculture in India. The locations were vectorised in a GIS platform, and thepotential areas available for sea cage installations were demarcated. An optimised sitesuitability schema was developed for the spatial demarcation of potential site selection.The preliminary results identified 134 sites covering a total area of 46,823.2 ha suitablefor marine cage culture along Indian territorial waters. Among the coastal states, the topthree states holding the maximum area suitable for sea cage farming are Andhra Pradesh(11,792 ha), Gujarat (11,572.2 ha) and Tamil Nadu (7,673 ha). It is envisaged that spatialsuitability demarcation even on this pilot scale will accelerate the expansion of sea cagefarming in the country. Keywords:GIS Mapping, Mariculture, PMMSY, Sea cage farming, Site suitability, Spatial planning

Spatial and temporal variation of microbial populations and microbial metabolic potential in a tropical marine cage-culture sediment system

The ecological roles of benthic microbes and the effect of anthropogenic mariculture activities on sediment microbial communities remain largely unexplored. Here, sediment bacterial abundances and diversity and their response to the disturbance induced by marine cage-culture farming were investigated at the station of Maniao Bay, Hainan province, China, with a history of cage culture for approximately 20 years. We characterized the sediment-associated microbial populations taken at marine cage culture zones and non-mariculture zones across one year. However, no significant differences between the marine cage culture and the non-mariculture zone occurred in microbial community structure and diversity. Minor differences among microbial communities during the year were observed in the sampling sites, which may be driven by the content of organic matter and sulfide in the sediment. This fact indicated that the diverse sediment microbiome was resilient to the stress caused by a modest environmental change. On the other hand, the ecological roles of the benthic microbes were explored by metagenomics, and their response to the marine cage-culture farm biodeposition was investigated across three years. The biochemical function carried out by the sediment microbes showed no significant difference between the marine cage culture zone and the non-mariculture zone. A stable microbial community was revealed in the Maniao Bay mariculture area and its adjacent sea area, which might be promoted by the hydrodynamic characteristics of the aquaculture area and its adjacent sea area, aquaculture scale, and culture mode.

Evaluation of marine aquaculture sustainable in the Ekas Coastal Zone during the pandemic of Covid-19

The Covid-19 pandemic has generally impacted coastal activities, including mariculture development. A decrease or increase in aquaculture production will influence the aquatic environment and socio-economic of coastal communities. The aims of this study were (1) to analyze mariculture production in Ekas Bay during the Covid-19 pandemic and (2) to evaluate the coastal management based on the coastal community perspective. The study analysis uses both of analysis of comparative and analysis of descriptive. The results showed that the number of floating marine cages and fishery production had increased by more than 500% during the pandemic compared to before the pandemic. From the results of the dept-interview with coastal communities and fisheries extension officers, one of the drivers for increasing the amount of marine production, especially lobster commodity, is the implementation of government policies related to lobster management. Coastal management implementation has a good category with 65,03% of response assessment. The study also evaluated household waste management, resulting in a poor category with 56.65% of respondents’ assessment. Household waste needs managed properly to minimize the risk of environmental degradation and decrease marine resources in Ekas Bay.

Potential Use of Image Analysis in Breeding Programs for Growth and Yield Traits in Meagre (Argyrosomus regius)

In the present work, we studied ten new productive traits in meagre (Argyrosomus regius), comprising three related to the carcass (cNiT) and seven related to morphometric (mNiT) characteristics. We harnessed non-invasive technology (NiT) by means of the IMAFISH_ML software. This tool’s potential was leveraged on an industrial scale, encompassing the evaluation of 612 fish from two distinct rearing systems (marine cages and indoor tanks) at the time of harvest. Each fish underwent digital photography for morphometric measurements, manual weighing, and was manually eviscerated and filleted to calculate the carcass and fillet yield. Subsequently, the principal genetic parameters were estimated. The heritabilities for the growth traits were moderate (0.34 and 0.39 for TL and BW), whilst those for the cNiT traits ranged from medium to low (0.32–0.27). For the mNiT, they demonstrated a medium to low range (0.15–0.37), whereas the carcass and fillet yield heritabilities were considered to be medium to high (0.32 and 0.31). Most of the genetic correlations between the growth, NiT, and yield traits were not estimated accurately due to the limited data. As was expected, we observed predominantly high and positive correlations between the growth and mNiT. A genetic correlation to highlight was the fillet yield with the fish maximum height (0.87 ± 0.23) and with the head height (0.87 ± 0.24). This suggests that indirect selection using NiT could improve the growth and yield traits. Employing a multi-trait selection approach enables us to capture a broader spectrum of genetic variability and to potentially identify individuals with superior genetic potential. The use of image analysis software ensures objective and precise measurements, thereby reducing the potential for human error or bias during the selection process. Further studies should be carried out to improve the accuracy of the estimates, especially those of the genetic correlations.

Hydrodynamics of nearshore coastal waters: Implications for marine cage farming in Kenya

Hydrodynamic characteristics are important considerations in the design of cages used for fish farming in nearshore marine environments. The hydrodynamics of sites in mangrove creeks and comparatively open water channels in Kilifi and Kwale Counties in Kenya were sampled across tidal cycles and seasons using an Acoustic Wave and Current Profiler (AWAC). Water temperature ranged between 25.9 °C and 33.0 °C, and was lower in deeper areas with larger tidal heights than in shallower areas with smaller tidal heights. The water column height ranged between 9.68 - 14.69 m at Kijiweni, 1.16 - 6.7 m at Kibokoni and Tsunza, and 0.72 - 2.57 m at Dabaso. Maximum current speeds were 0.83 - 0.87 m/s at Kijiweni, 1.1 m/s at Kibokoni, 0.89m/s Tsunza, and 0.34 m/s at Dabaso. Wave height reached 0.35 and 0.36 m at Kijiweni, 2.7 m at Kibokoni, 1.3 m at Tsunza, and 1.6 m at Dabaso. The considerable difference in hydrodynamic characteristics between the sampling sites indicate that cages for marine fish farming should be designed specifically for local conditions in mangrove creeks and Cages for fish farming therefore require specific design and structural features depending on the local hydrodynamic conditions.

Effects of water temperature and light/dark cycles on in vitro egg laying and hatching of the monogenean Microcotyle sebastis on Korean rockfish (Sebastes schlegelii)

Aquaculture faces increasing challenges from parasitic infections, notably impacting the marine cage farming of Korean rockfish (Sebastes schlegelii). A primary contributor to these challenges is the monogenean parasite Microcotyle sebastis, which incurs significant economic losses. To formulate effective management strategies, it is essential to understand how environmental variables influence the reproductive behavior and survival of M. sebastis. In this study, we conducted controlled in vitro experiments to assess the fecundity, hatching success, and viability of M. sebastis across a temperature range from 25 °C to 4 °C, as well as under varying light/dark conditions. We found that the parasite's fecundity was optimal at 15 °C and minimal at 4 °C. Survival rates exhibited an inverse correlation with increasing temperatures. The hatching process was most rapid at 25 °C, with no hatching observed at 4 °C. Upon hatching, the maturation and lifespan of oncomiracidia varied depending on temperature: cilia degenerated within 36 h at temperatures ranging from 25 °C to 15 °C, whereas at 10 °C, cilia began to degenerate on the fourth day post-hatching, surviving for up to nine days. Interestingly, conditions of perpetual darkness led to increased egg production and survival rates compared to light exposure. Our findings provide critical insights into the adaptive responses of parasites to environmental changes and suggest that current deworming strategies may not adequately address the rapid hatching and increased egg production of M. sebastis. We emphasize the need for ongoing research to adapt aquaculture management strategies to the evolving challenges posed by parasites and recommend that future research focus on field studies examining the impact of environmental variables and multiple parasite species.

Emerging challenges in maintaining marine food-fish availability and food safety.

The marine finfish and crustaceans contribute immensely to human nutrition. Harvesting marine food-fish to meet the global demand has become a challenge due to reduction of the fishery areas and food safety hazards associated with increased pre-harvest and post-harvest contaminations. The causes of low fish availability and contaminations were reviewed following the published literature from 2000 to 2023. The marine fish yields are stressed due to spread of contaminants triggered by rising sea temperatures, transport of microorganisms by marine vessels across the oceans, anthropogenic activities leading to increase in the toxic microorganisms, and the entry of toxic chemicals and antibiotic residues into the seawater through rivers or directly. Processing adds pyrogenic chemicals to foods. The hazardous materials may accumulate in the food-fish, beyond tolerance limits permitted for human foods. While the research and control measures focus on minimizing the hazards due to pathogenic microorganisms and chemicals in market fish, there is less discussion on the unhealthy changes occurring in the oceans affecting the quantity and quality of food-fish, and the origins of microbial and chemical contaminations. This review examines the factors affecting availability of wild food-fish and increased contaminations. It aims to bridge the knowledge gaps between the spread of hazardous agents in the marine environment, and their effects on the food-fish. Meeting the future human food security and safety through marine fish and fish products may need marine cage farming, introduction of genetically modified high yielding food-fish, and cultured contaminant free finless fish muscles as options.

Mediterranean Aquaculture and Genetic Pollution: A Review Combined with Data from a Fish Farm Evaluating the Ecological Risks of Finfish Escapes

Mediterranean finfish aquaculture is mainly represented by the production of the gilthead sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) growing in marine cage farms. Despite the numerous benefits of fish farming, the ecological risk potentially caused by fish escapes to the wild populations is occasionally high. In the current study, an integrated review of fish escapes is presented regarding S. aurata and D. labrax escapes and their potential effect on the genetic composition of wild populations. The collected data from the literature are combined and discussed along with recorded escapes in a fish farm located in the Aegean Sea, Greece. According to these records, fish escapes present a generally stable rate, ranging between 0 and 2% in each escape event, which occur 5–8 times per year. Although for other farmed fish species worldwide, the ecological risk may be higher, this risk is probably lower in Mediterranean finfish populations, which are characterized by generally low levels of genetic differentiation. Nevertheless, the risk of genetic introgression still exists. Particularly in sea bream and sea bass farming, genetic structure and differentiation in wild populations seem to be unaffected for now. Nevertheless, suitable management measurements would be a useful strategy to avoid future negative effects of fish escapes. These strategies should be focused on further efforts towards recapture program development, reduced escapees’ survival, and proper legislation. Furthermore, more data on escapees’ survival percentage, their migration pathways, and the way these pathways relate to mortality, the type of escape event, and the season of release would be also valuable.

Kuluçkahane Kökenli F5 ve F6 Nesil Karadeniz Somonu Anaçlarının (Salmo labrax PALLAS, 1811) Üreme Performansları

In this study, reproductive performances of F5 and F6 generation hatchery-originated female Black Sea salmon (Salmo labrax) were evaluated to determine the effects of the ongoing selective breeding program. The study was conducted in freshwater pools and marine cage systems between 2018 and 2021. For the study, 53 specimens from F5 generation females with an average length of 52.71±7.08 cm and weight of 1561.29±639.76 gr, and also 56 broodstıcks specimens from F6 generation females with an average length of 51.92±5.35 cm and weight of 1506.12±417.28 gr were used. Gonad maturity controls and spawning studies were carried out in the 2018-2019, 2019-2020 and 2020-2021 breeding periods along the entire season, lasting from November to January. The number of ovulating females, their fecundity, egg diameters and fertilisation rates of eggs were recorded. In all seasons, 36.17% of F5 females ovulated in November, and the remaining females (63.83%) ovulated in December. Ovulation time in F6 females also showed a similar pattern of 1/3 of females (37.40%) ovulating in November and the remaining majority (62.60%) ovulating in December. According to the results, total egg yields as 4439.31±1675.69 and 4112.08±1041.16 egg/broodstock, relative egg yields as 2313.44±278.48 and 2345.76±516.30 egg/kg, egg diameters as 5.08±0.19 and 5.21±0.17 mm, and fertilisation rates as 96.78±3.24% and 96.63±3.73% were determined for F5 and F6 generations, respectively. In both generations, as the size of the broodstock increases, the total egg production increases (F5: r=0.9169, F6: r=0.74254), while the relative egg production (F5: r=-0.2526, F6: r=-0.3486) decreases. When the total egg yields and fertilisation rates were compared, the difference between the F5 and F6 groups was insignificant (p≤0.05). The condition factors of the two generations were found to be statistically similar (p≤0.05).

Salinity and temperature alter the efficacy of salmon louse prevention

Several promising preventive tools and strategies have been developed to combat infestation of salmon in marine cages by parasitic salmon lice. While most of the prevention strategies tested have significantly reduced louse infestations in some trials, they have also had negligible impact in others. To better understand the observed performance variability a meta-analysis was conducted to examine the efficacy of physical barriers and behavior modification, the louse prevention tools with the strongest evidence base, in relation to local salinity and temperature conditions. Integrated prevention strategies which combine behavior modification with skirt barriers gave the most consistent protection, halving louse infestations through all measured environmental conditions with no negative impacts on growth or gill condition. Snorkel barriers provide the greatest potential protection from lice, with reductions of over 80% in ideal conditions when salinity is uniform throughout the water column, but are sensitive to environmental variation and accompanied by reduced growth and increased amoebic gill disease severity. Behavior modification alone did not significantly impact louse infestation, growth or gill health in any conditions. The results herein show that understanding the interrelationships between preventive tools and environmental conditions is central to optimizing tool choice and deployment strategy. Parasite prevention does not operate in a vacuum, and clear understanding of the risks and limitations of such tools is critical for them to have practical applicability.