Extensive Aquaculture Research Articles

Exploring Spatial Dynamics of Water Quality in a Tropical Lake Affected by Aquaculture

Lake Maninjau, like many surface water bodies worldwide, faces significant water pollution challenges due to extensive aquaculture activities, making it an ideal site to study the impact of fish farming on water quality, which has contributed to eutrophication and declining water quality. This study investigates the physicochemical parameters and pollution levels in the lake, aiming to provide insights into its environmental health. In August 2022, a comprehensive sampling campaign was undertaken at nine stations within the upper layers of open water and littoral zones of Lake Maninjau. In situ measurements, including temperature, dissolved oxygen, and pH, were conducted, accompanied by water sample collection for laboratory analysis of trace elements and heavy metals. Our study revealed notable variability in water parameters across different sites, with surface water layers exhibiting the greatest differences. While certain parameters such as temperature and conductivity remain relatively stable, pH levels show a decreasing trend with increasing water depth. Dissolved oxygen levels vary widely, while oxidation–reduction potential indicates water pollution, particularly in littoral zones. Potassium dominance within cations likely suggests anthropogenic influences, notably from aquaculture activities, that may also contribute to nutrient enrichment and heavy metal pollution. Elevated levels of total nitrogen and ammonia underscore the lake’s moderate pollution levels, with heavy metals such as mercury exceeding permissible limits, posing risks to aquatic life and human health.

Assessing White Spot Syndrome Virus (WSSV) and Acute Hepatopancreatic Necrosis Disease (AHPND) concurrent with Vibrio spp. in various Penaeus monodon aquaculture farms at southwestern region of Bangladesh

This study was conducted to assess the prevalence of White Spot Syndrome Virus (WSSV) and Acute Hepatopancreatic Necrosis Disease (AHPND) in giant tiger shrimp (Penaeus monodon Fabricius, 1798) aquaculture systems (extensive, improved-extensive, and semi-intensive) in the south-western region of Bangladesh. This research employed real-time polymerase chain reaction (RT-PCR) to quantification cycle (Cq) values for identification of WSSV and AHPND in shrimp samples and Vibrio spp. was identified through biochemical tests on water and soil samples (n=72 for each) from different aquaculture systems. The results of the study indicated significant difference (p < 0.05) in nitrate and ammonia levels across the various aquaculture systems, highlighting the critical need for rigorous water quality monitoring and management. Extensive aquaculture exhibited the highest prevalence of WSSV (40%) and AHPND (33%) positive samples, whereas semi-intensive aquaculture had the lowest prevalence, with 22% WSSV-positive and 20% AHPND-positive samples. Biochemical analysis identified three Vibrio spp. such as V. cholerae, V. vulnificus, and V. parahaemolyticus - with significantly higher concentrations in extensive aquaculture compared to semi-intensive. Notably, V. vulnificus was more abundant (0.9×103 cfu/ml) in the soil of extensive aquaculture, while it was less prevalent in water. In conclusion, this study underscores that the risk of WSSV and AHPND was greater in extensive aquaculture due to inadequate management.

Genetic Variability in Mediterranean Coastal Ecosystems: Insights into Ostrea spp. (Bivalvia: Ostreidae).

Oysters are sessile, filter-feeding bivalve molluscs widely distributed in estuarine and coastal habitats worldwide. They constitute a valuable resource for fisheries and extensive aquaculture and provide essential ecological services. Yet, their genetic diversity and distribution remain understudied. The variability in shell morphology complicates species classification, which is influenced by environmental and genetic factors. Although molecular phylogenetics research has refined oyster taxonomy and identified approximately 100 extant species, numerous taxonomic uncertainties persist. In the present study, we aimed to document the occurrence of small flat oysters of the genus Ostrea along the Mediterranean coastal areas of Liguria and Sardinia (Italy). Specifically, 16S rRNA sequence data were used to identify Ostrea species. Our findings offer novel insights into the O. stentina species complex and O. neostentina, a new species in the Mediterranean coastal areas of Italy. The study data further our understanding of Ostrea species diversity, distribution, and evolutionary patterns.

Complexities and opportunities: A review of the trajectory of fish farming in Zimbabwe

AbstractZimbabwe is currently rated as one of the top 10 fish producers in Sub‐Saharan Africa. Fish farming in Zimbabwe is dominated by the culture of Nile tilapia (Oreochromis niloticus) followed by rainbow trout (Oncorhynchus mykiss). Over 90% of the cultured fish is O. niloticus, which comes from Lake Kariba. Since the first decade of the 21st century, there has been a significant increase in fish production from two tons to eight tons annually. The increase in fish production has been attributed to the government and donor‐funded fishery programs. In this review, current practices, opportunities, and challenges for aquaculture in Zimbabwe are highlighted. The current practices include intensive, semi‐intensive, and extensive aquaculture systems. Consistent high market demand for fish and numerous water bodies with potential for cage culture are some of the drivers for aquaculture. Despite the industry's significant growth, there are still a number of management and production issues that need to be resolved. Weaknesses in structural issues and operational frameworks in Non‐Governmental Organizations, lack of credit facilities, subsidies, limited technology, obfuscated governance, weak fish disease surveillance mechanisms and legal frameworks, and constrained human resources capacity are some of the challenges plaguing fish culture in Zimbabwe. Cogent aquaculture policies, sustainable subsidies, intensive training of human resources and fisheries experts, strengthened disease surveillance, cheaper alternative fish feeds, reliable viable fingerling production, concerted value chain efforts, and exploration of lucrative export markets is a panacea for the fledgling aquaculture industry in Zimbabwe.

Climate Change Impacts on Aquaculture Systems in Key Producing Nations: Assessing Vulnerability and Proposing a Novel Adaptation Measure

Climate change poses a significant threat to the aquaculture industry, impacting both the productivity and sustainability of this vital sector. This study focuses on the vulnerability of the top aquaculture producing nations to climate change and explores potential novel adaptation strategy. The vulnerability assessment considered various factors, including the exposure of aquaculture systems to climate change, Productivity of the industry, climate change initiators and the GDP of each nation surveyed. The study identifies the United Kingdom (UK) aquaculture as the most vulnerable and at risk of climate change impacts followed by the United States of America (USA) and Nigeria’s aquaculture. In terms of continents, Europe, Oceania, and Africa are identified as the most vulnerable regions, while America and Asia are considered the least vulnerable. The UK, with its extensive aquaculture operations and geographical exposure to climate change risks, faces significant challenges in adapting to changing conditions especially with the exit from European Union (Brexit). The USA, another major aquaculture producer, also faces vulnerability due to its diverse range of climatic conditions and coastal aquaculture operations. Nigeria, a prominent aquaculture producer in Africa, is highly vulnerable to climate change due to its dependence on freshwater aquaculture systems leading to low water usage in aquaculture despite vast marine water resource. Strict measures including novel adaptation measure such as the NanoSolar technique must be put in place in these countries in other to ensure that aquaculture production doesn’t decline and also to ensure that global food security is not put under pressure with the growing world population size.

The Matupiri amazon fish Tetragonopterus chalceus as a bioindicator of pollution

Oxidative stress is a biological condition in which imbalance occurs between the production of reactive oxygen species. The present study aimed to evaluate the hemoglobin (Hb), methaemoglobin (mHb) and Glutathione (GSH) contents as indicators of oxidative stress in Matupiri Tetragonopterus chalceus. Fish were collected in the port area of ​​Santana, AP and others in extensive aquaculture area in Amapá, AP, Brazil. Blood samples were collected, the samples were diluted in phosphate buffer and analyzed in a spectrophotometer. When evaluating Hb, mHb and GSH, significant increases of these components were observed in fish blood (P &lt;0.05). This suggests that the analyzed port site presents an environmental imbalance due to the exposure of the organisms to high concentrations of ores, provoking possible oxidative stress which may compromise the site for fishing and aquaculture purposes.

‘Finprint’ technopolitics and the corporatisation of global food governance

AbstractOur concern in this paper is the environmental ‘footprinting’ of food and its role as a source of technopolitical power in global food governance. Our case is the highly industrialised farmed salmon sector which currently generates metrics and carefully curated visualisations to promote this fish as a more sustainable and ‘climate friendly’ protein relative to animal protein produced on land. We show how these metrics and visualisations depend on an industrial production and measurement infrastructure. Significantly, this infrastructure and the metrics that it generates is being promoted as a ‘climate smart’ solution to small‐scale and extensive aquaculture in the Global South. Salmon aquaculture industry proposals for the transfer of technology from salmon farming to global aquaculture are explicitly articulated in global food governance and other institutional spaces. While there may be frictions in the transfer of salmon aquaculture's infrastructure of measurement to aquaculture in the Global South, our analysis suggests that environmental footprinting of food—and its associated measurement infrastructure—may be an emerging source of technopolitical power in increasingly corporatised global food governance systems.

Exploring the Integration of Rice and Aquatic Species: Insights from Global and National Experiences

The objective of this article is to review the historical development of rice–aquatic species (RASp) integration and analyze the factors that affect its performance. Compared to rice monoculture, the integration of the rice–aquatic species system has a more significant impact on farm production, income, land (L), water use efficiency (WUE), net revenue, and labor use efficiency (LBUE) reduction. Although concurrent and alternate cultivations of rice–aquatic species increase unit water efficiency, concurrent cultivation requires 26% more water than monoculture. Furthermore, RASp farming promotes environmentally-friendly rice cultivation by reducing the use of pesticides (insecticides and herbicides), decreasing CH4 emissions by approximately 14.8–22.1%, and enhancing water quality. These findings suggest that fish integration in rice fields could be integrated into extensive aquaculture. Finally, global cooperation is necessary to transfer knowledge about this technology, particularly from China, and more research is needed to evaluate the effects of rice–aquatic species integration in the context of climate change and practical water use efficiency. Additionally, a robust development program at the national and global levels, with regulatory and non-administrative bodies’ guidance and strategy, is needed to embrace the expansion of the rice–aquatic species practice.

Determinants influencing fishermen’s willingness-to-participate and willingness-to-pay for conservation of small indigenous fishes: a model-based insight from Indian Sundarbans

Small indigenous fishes (SIF) play a crucial role in supporting the livelihoods and nutritional security of the rural population in Southern Asia. However, their abundance and diversity are under threat due to overexploitation and profitable extensive aquaculture, resulting in a sharp decline, particularly in India. Unfortunately, conservation strategies for SIF have received little attention from researchers, making it imperative to understand stakeholders’ decision-making processes to develop effective conservation strategies. This article aims to quantitatively identify the factors that influence fishermen’s intention to participate in and pay for SIF conservation efforts. The study utilizes questionnaire-based survey data from 100 households engaged in local fisheries in the rural Indian Sundarbans. To gain critical insight into fishermen’s decision processes, a bivariate logistic Generalized Additive Model is employed, focusing on willingness-to-participate and willingness-to-pay for SIF conservation. The study’s results indicate that several factors significantly influence fishermen’s willingness-to-participate in conservation efforts. These include Literacy, Conservation awareness, and Occupation. On the other hand, Conservation awareness and Household income are identified as significant determinants of fishermen’s willingness-to-pay for SIF conservation initiatives. One intriguing finding of the research is the identification of a nonlinear response-age curve for both willingness-to-participate and willingness-to-pay, as well as their interaction. Notably, the 45-50 years old age group emerged as the most likely implementers of small indigenous fish conservation strategies, suggesting that targeting this age group in conservation programs could yield positive outcomes. The study underscores the importance of various conservation strategies to bolster SIF preservation in the region. Recommendations include increasing and extending conservation awareness programs, specifically targeting suitable age-group individuals with appropriate education, household income, and occupation. These strategies are vital for formulating effective conservation guidelines that align with the specific needs and characteristics of the region. In conclusion, this research sheds light on the factors influencing fishermen’s participation and willingness to financially support the conservation of small indigenous fish in the rural Indian Sundarbans. The findings contribute valuable insights for policymakers, conservationists, and stakeholders, emphasizing the urgency of sustainable measures to safeguard SIF populations and ensure the continued livelihoods and nutritional security of the local communities.

Farming Sparus aurata (Teleostei: Sparidae) in marsh ponds: trophic characterization and trace metal accumulation

Considering the overexploitation of fishing on most of the world coasts, the ingestion of fish and shellfish will depend mostly on aquaculture production. Since intensive mariculture usually involves environmental impact, developing sustainable cultures is a priority. In this sense, salt marshes can provide ecosystem services and incorporate both conservation and extensive aquaculture activities. In the present study we compared gilthead seabream Sparus aurata Linnaeus, 1758 cultured in extensive and semi-intensive marsh ponds with wild conspecifics from surrounding coastal areas, using trophic characterization (diet analysis and stable isotopes) and trace metal accumulation. Stomach content analysis revealed different feeding habits among gilthead seabream from different origin. Although wild specimens had the most diverse diet, results of stable isotopes showed that extensive diet had the wider isotopic niche and revealed the highest similarities between wild and extensively cultured gilthead seabream. A similar trace element signature was also measured in wild and extensive culture, whereas the semi-intensive culture showed different concentrations for several elements. Cr, Fe and Mn showed the highest concentrations in semi-intensive cultured fish, while As and Zn showed the lowest values in this group. In any case, average values measured in both extensive and semi-intensive culture were, in general terms, below the hazardous limits provided by the standards recommended for trace metals by national and international regulations. Therefore, marsh ponds provide a suitable environment where the cultured fish, especially extensive, should be promoted.

Seabed morphodynamics of a coastal lagoon of the Gulf of California

A two-dimensional, vertically integrated, non-linear numerical model was applied to investigate the Urias coastal lagoon’s (URCOL) tide-driven currents, bed load sediment transport, and seabed morphodynamics. The coastal body of water, located on the eastern side of the Gulf of California, includes the Mazatlán harbour, the most important port on the Pacific Mexican coast due to the relevant activities like the heavy vessel traffic. URCOL also includes an extensive aquaculture infrastructure at the lagoon head. The tidal hydrodynamic modelling revealed the mixed character of tides predominantly semidiurnal in the lagoon. The numerical computation at the harbour entrance showed an ebb-dominant tidal distortion. The distribution patterns of the erosion and accretion rates are consistent with the convergent and divergent character of the vectors of sediment transport rates. The sediment accretion has been predicted mainly in the middle part of the channel, right where the channel starts curving, changing the alignment of the lagoon. The tidal hydrodynamics, sharp topographic gradient, and geometric features of the lagoon seem to determine the location of accretion and erosion areas.

Does experimental seaweed cultivation affect benthic communities and shorebirds? Applications for extensive aquaculture.

Extensive seaweed aquaculture is a growing industry expected to expand globally due to its relatively low impact and benefits in the form of ecosystem services. However, seaweeds are ecosystem engineers that may alter coastal environments by creating complex habitats on previously bare mudflats. These changes may scale up to top-consumers, particularly migratory shorebirds, species of conservation concern that regulate trophic webs at these habitats. Understanding how habitats are transformed and how this affects different species is critical to direct ecological applications for commercial seaweed management. We experimentally assessed through a Before-After Control-Impact design the potential changes exerted by Gracilaria chilensis farming on bare mudflats on the abundance, biomass, and assemblage structure of benthic macroinvertebrates, and their scaled-up effects on shorebirds' habitat use and prey consumption. As predicted, experimental cultivation of G. chilensis significantly affects different components of biodiversity that scale-up from lower to upper trophic levels. The total biomass of benthic macroinvertebrates increased with seaweed cultivation and remained high for at least 2 months after harvest, boosted by an increase in the median size of polychaetes, particularly Nereids. Tactile-foraging shorebirds tracked these changes at the patch level increasing their abundance and spending more time foraging at seaweed cultivated plots. These results suggest that seaweed farming has the potential to impact shorebird populations by favoring tactile-foraging species which could lead to a competitive disadvantage to species that rely on visual cues. Therefore, the establishment of new seaweed farms in bare mudflats at key sites for shorebirds must be planned warranting habitat heterogeneity (i.e., cultivated and non-cultivated areas) at the landscape level and based on a previous experimental approach to account for local characteristics. Fostering properly designed extensive seaweed farming over other aquaculture industries with greater negative environmental impacts would provide benefits for human well-being and for ecosystem functions.

Assessing Adverse Impacts of Aquaculture Activities on Groundwater Quality in Ponneri Taluk of Tiruvallur District, Tamilnadu using Drinking Water Quality Index

Tamilnadu is a State that is deprived of perennial water sources like major rivers and streams. Agricultural activities in Tamilnadu are mainly dependent on seasonal rainfall and ground water. The shortages of water resources drive many coastal farmers to convert their fertile agricultural lands to aquaculture. Groundwater suitability for human consumption is determined by its physical, chemical and bacteriological properties. Irrational conversion of agricultural lands to aquaculture is found to be unsustainable leading to wastage of sparse natural resource fertile land and groundwater. The aquaculture practices started very extensively since year 2012 where fertile agriculture land, land with scrub and wasteland area have been converted for the aquaculture ponds. The use of temporal remote sensing helps in understanding the patterns of land use conversion from agricultural practice to aquaculture. In addition, indiscriminate use of fertilizers and chemicals in aquaculture farming has led to soil salinization and ground water pollution in many parts of study area. Use of salinity indices was tried in identification of salinity levels in lands in and around the current and abandoned aquaculture ponds. The study indicates that the use of Remote Sensing and GIS has helped in identification of landuse conversion and its adverse effects on characteristics of land due to extensive aquaculture activities in Ponneri Taluk of Tamilnadu. Using satellite data of Landsat OLI 8 (2015), IRS LISS IV, Sentinel II 2017, the changes have been estimated. The water quality parameters include pH, TDS, cations such as Ca, Mg, Na and K, anions such as Cl, SO4, HCO3, NO3 and PO4. Surface and groundwater quality results are cross-checked at the field areas which clearly indicate that almost entire Ponneri Taluk groundwater is unsuitable for drinking purposes. The classification for drinking water is obtained by DWQI. The piper plot has been studied by the geochemistry methods.

Metagenomic analysis of gut microbiota and antibiotic-resistant genes in Anser erythropus wintering at Shengjin and Caizi Lakes in China.

Migratory birds are the primary source and reservoir of antibiotic-resistant genes (ARGs) related to their gut microbes. In this study, we performed metagenomics analysis to study the gut microbial communities and ARGs of Anser erythropus wintering at Shengjin (SJ) and Caizi (CZ) Lakes. The results showed that bacteria, fungi, viruses, and archaea were the dominant gut microbes. Principal component analysis (PCA) indicated that the microbiota compositions significantly differed between the two populations. Diet may be the most crucial driver of the gut microbial communities for A. erythropus. This species fed exclusively on Poaceae spp. at Shengjin Lake and primarily on Carex spp. at Caizi Lake. Tetracycline, macrolide, fluoroquinolone, phenicol, and peptide antibiotics were the dominant resistant types. ARGs had a significantly higher abundance of operational taxonomic units (OTUs) in the Shengjin Lake samples than in Caizi Lake samples. PCA indicated that most Shengjin Lake samples significantly differed in gut microbiota composition from those obtained at Caizi Lake. This difference in gut microbiota composition between the two lakes' samples is attributed to more extensive aquaculture operations and poultry farms surrounding Shengjin Lake than Caizi Lake. ARGs-microbes associations indicated that 24 bacterial species, commonly used as indicators of antibiotic resistance in surveillance efforts, were abundant in wintering A. erythropus. The results revealed the composition and structural characteristics of the gut microbiota and ARGs of A. erythropus, pointing to their high sensitivities to diet habits at both lakes. This study also provides primary data for risk prevention and control of potential harmful pathogens that could endanger public health and therefore are of major significance to epidemiological and public health.

Histopathological Investigation of Prawn Penaeus monodon in the Improved Extensive Culture Ponds of Nellore Region, Andhra Pradesh, India

Present work was aimed to see the quality of the prawn Penaeus monodon under improved extensive aquaculture system collected from Muthukur area of Andhra Pradesh located Pradesh located at 14.29 19 latitude and 80.10383 longitude. To assess the quality of the prawn, prawns were surveyed in the improved extensive pond and collected for histopathological investigation by adopting double staining methods (hematoxylin and eosin). Results showed that WSSV (White Spot Syndrome Virus) was characterised by prominent eosinophilic to pale basophilic intra nuclear inclusion bodies in hypertrophied nuclei of most commonly in the epithelial cells and connective tissue cells of the above target tissues. Monodon baculovirus (MBV) was characterised by intensive stained or multiple spherical or rounded hypertrophied intra nuclear inclusion bodies ranging from 0.1 m to 18 m in the epithelial cells of hepatopancreas. This kind of necrotic behaviour was also found along with acidophilic intra nuclear inclusion in hypertrophic nuclei with marginated chromatin. MBV infected shrimps showed generalised signs of disease such as lethargy, anorexia, poor feeding, dark colouration and reduced growth rate. Intensive stained basophilic hypertrophic rounded intranuclear inclusions symptoms were also found due to those disease both in eye and gill tissues. It is predicted that the prawn collected from the pond showed the symptoms of both viral and bacterial infection.

Aquaponics Production of Wheatgrass (Triticum aestivum L.) in Different Horticultural Substrates with African Catfish (Clarias gariepinus) in Northern Germany

In the present study, wheatgrass (Triticum aestivum L.) was chosen since fish effluents could be adequate to support its optimal growth. Wheatgrass was irrigated by water from African catfish (Clarias gariepinus) production under two stocking densities, namely extensive aquaculture unit (EAU) and intensive aquaculture unit (IAU), and tap water mixed with fertilizer (Control) in combination with three horticultural substrates: 100% coconut fibers (C), 70% coconut fibers + 30% perlite (CP), and 50% perlite + 50% vermiculite (PV) in an ebb-and-flow system. Different plant growth parameters, including nutrient contents, were evaluated and discussed. The results showed that regarding irrigation water, shoot dry mass was significantly higher in fish water groups. The root–shoot ratio was significantly higher in Control. The highest SPAD index was discovered in IAU. Regarding substrates, the root–shoot ratio was significantly low in C. Vitamin and mineral production reached mainly the highest concentrations in the combination of fish water with different substrates. In conclusion, irrigation water from IAU and coconut fibers were sufficient for optimal wheatgrass growth; meanwhile, IAU effluents showed a positive influence on vitamin production. Our study demonstrates the potential of aquaponics as a more sustainable way of producing superfoods.

Use of data on zoobenthos reserves of fishless reservoirs to assess potential production of bentophage fish similar small reservoirs of north-west Kazakhstan

The potential fish productivity of four fishless reservoirs of Western Kazakhstan is estimated for subsequent use in fish farming calculations on similar fishery reservoirs of the region. Potential fish production was determined by the biomass of feed zoobenthos. In parallel the productivity of carp as main object of extensive aquaculture was evaluated in the lake-commercial fish farms. The obtained values of potential fish production in the reservoirs deprived of ichthyofauna equaled to 72 kg per ha for the reservoirs of West Kazakhstan and 37 kg per ha for the Aktobe region. The productivity of carp grown in extensive aquaculture in the West Kazakhstan region in the first year of cultivation amounted to 75 kg per ha.

Improving Satellite Retrieval of Coastal Aquaculture Pond by Adding Water Quality Parameters

Coastal aquaculture is an important supply of animal proteins for human consumption, which is expanding globally. Meanwhile, extensive aquaculture may increase nutrient loadings and environmental concerns along the coast. Accurate information on aquaculture pond location is essential for coastal management. Traditional methods use morphological parameters to characterize the geometry of surface waters to differentiate artificially constructed conventional aquaculture ponds from other water bodies. However, there are other water bodies with similar morphology (e.g., saltworks, rice fields, and small reservoirs) that are difficult to distinguish from aquaculture ponds, causing a lot of omission/commissioning errors in areas with complex land-use types. Here, we develop an extraction method with shape and water quality parameters to map aquaculture ponds, including three steps: (1) Sharpen normalized difference water index to detect and binarize water pixels by the Otsu method; (2) Connect independent water pixels into water objects through the four-neighbor connectivity algorithm; and (3) Calculate the shape features and water quality features of water objects and input them into the classifier for supervised classification. We selected eight sites along the coast of China to evaluate the accuracy and generalization of our method in an environment with heterogeneous pond morphology and landscape. The results showed that six transfer characteristics including water quality characteristics improved the accuracy of distinguishing aquaculture ponds from salt pans, rice fields, and wetland parks, which typically had F1 scores &gt; 85%. Our method significantly improved extraction efficiency on average, especially when aquaculture ponds are mixed with other morphological similar water bodies. Our identified area was in agreement with statistics data of 12 coastal provinces in China. In addition, our approach can effectively improve water objects when high-resolution remote sensing images are unavailable. This work was applied to open-source remote sensing imagery and has the potential to extract long-term series and large-scale aquaculture ponds globally.

An evaluation of the engineering suitability of extensive brackishwater ponds in Barru, South Sulawesi Province, Indonesia

In brackishwater aquaculture, pond engineering is essential to meet the cultured species' bio-physical requirements and potentially minimizing social and environmental impacts. This study evaluated the suitability of pond engineering designs and pond, dyke, and canal construction at family-run, extensive brackishwater aquaculture farms in Barru regency of South Sulawesi, Indonesia. Soil properties, topography, hydrological data, field surveys, and high resolution (0.6 m) Quickbird imagery were used to assess the suitability of local pond engineering designs and the efficiency of canals. The study shows that in 752 of the evaluated pond units (430 ha), about 70% of pond beds were not constructed at the optimal pond elevation. Basic engineering requirements for pond layout and dyke and canal designs were not addressed in more than 70% of the pond units. Cease-to-flow conditions commonly occur due to the sedimentation of canals. Flows are also attenuated due to collapsed dykes. Farmers disregarded soil limitations and the impacts of tidal conditions and wave regimes. It is unlikely that shrimp and fish production in the region can increase without significant improvements in pond engineering. The problems identified by the study are not unique to Barru; they also occur in other extensive aquaculture areas in Indonesia and the region. Increased awareness of the need for improved pond engineering techniques is urgently needed to safeguard the economic and environmental sustainability of Indonesia's valuable aquaculture industry.

Diet of Great Cormorants Phalacrocorax carbo in Relation to Fish Resources in the Upper Adriatic Sea

The necessity of balancing conservation issues with the protection of aquaculture activities drives research to quantify the impact of the Great Cormorant Phalacrocorax carbo and to identify the best mitigation strategies. This study aims to characterise the diet in relation to the possible impact of the Great Cormorant on the extensive aquaculture farms in Friuli Venezia Giulia region in the upper Adriatic Sea. The diet of the species was investigated by analysing 459 pellets, collected monthly during the winter 2006/2007 in the three most important roosts of the Friuli Venezia Giulia coastline. Cormorants proved to feed mainly on typical fish species of lagoon and coastal waters. By frequency, Sand Smelts Atherina boyeri (54%) and Flounders Platichthys flesus (26%) were the main prey. Flounders played an important role also in terms of biomass (35%), together with mullets (Mugilidae, 28%). Commercially-important aquaculture species (European Seabass Dicentrarchus labrax and Gilthead Bream Sparus aurata) represented only 2% and 14% by frequency and biomass. The diet analysis supports our previous studies, carried out by behavioural observations on Cormorants foraging at different depths, on interactions with the main prey and strategies of exploitation of the fish farms. Our data imply that the Great Cormorant does not have a large effect on aquaculture yield in the north Adriatic Sea.