Sustainable Aquatic Research

Aquaculture chemotherapy in the Philippines: A review

Jonald Bornales — 2025-04-30

Aquaculture plays a crucial role in global food security, yet it faces mounting challenges in promoting sustainable and responsible practices. In the Philippines, while the aquaculture industry significantly contributes to the economy, its reliance on chemicals—particularly antibiotics—poses serious risks to public health and the environment. The industry's sustainable development is hindered by a lack of transparent regulatory oversight and limited access to eco-friendly alternatives. This review assesses the current state of chemical use in Philippine aquaculture, focusing on key species and related challenges. It also examines the effectiveness of the regulatory framework governing chemical use, explores emerging drug alternatives, and suggests strategies to improve regulatory oversight and encourage the adoption of environmentally sustainable practices. The Philippine aquaculture industry, dominated by seaweeds, milkfish, and tilapia, is rapidly expanding. However, this growth is often accompanied by increased chemical usage, including antibiotics, antiparasitic agents, antifungal agents, disinfectants, vaccines, inorganic fertilizers, and more. Despite existing regulations, enforcement and public transparency remain problematic. The excessive use of chemicals in Philippine aquaculture poses significant threats to both public health and environmental sustainability. Urgent action is required to enhance regulatory oversight, encourage the use of eco-friendly alternatives, and ensure the industry's long-term viability. To address these challenges, it is recommended that the government enforce stricter regulations and monitoring mechanisms for chemical use in aquaculture, invest in research and development of sustainable alternatives, raise public awareness about the risks of chemical use, and collaborate with international organizations to share best practices and develop harmonized standards.

A Review of fish value-added products in Kenya: Current status, challenges and areas for improvement

Domitila Kyule — 2025-04-29

Fish products are essential to Kenya’s economy and nutrition, yet their high perishability limits their accessibility and export potential. Developing fish value-added products—such as fish samosas, sausages, fillets, and powders—presents a promising solution, potentially enhancing resource utilization, reducing waste, and expanding markets. Despite the value addition’s significance for economic sustainability, comprehensive documentation on Kenya’s fish value-added products is lacking, hindering optimal sectoral growth. This review examines Kenya's current landscape for fish value-added products, the challenges, and potential improvements. Key products discussed include samosas, fillets, sausages, fish balls, smoked fish, fish oils, burgers, and soups, alongside primary processing techniques like improved smoking kilns, Mama Karanga boxes, chilling, and freezing. Several issues impede growth, notably poor regulatory and quality controls, limited access to technology and capital, infrastructure deficiencies, insufficient research, weak policies, and inadequate market information. Recommendations to bolster the sector include establishing stringent quality standards, enhancing regulatory enforcement, expanding financial accessibility, upgrading infrastructure, and promoting research and development. Increasing consumer and producer awareness through training, improved market information systems, and accessible financing options could further stimulate growth. This paper’s insights underscore the need for strategic interventions to unlock the potential of Kenya’s fish value-added sector, fostering livelihood enhancement and food security. Implementation of targeted programs and policies can transform the fisheries and aquaculture sector into a robust contributor to the country’s economic resilience and community well-being.

How much water is in prison in our world?

Erkan Can — 2025-04-29

The hydrological cycle describes the continuous movement of water above and below the Earth's surface. This cycle includes the journey of water from the oceans and seas to the atmosphere, from the atmosphere to the Earth's surface, and back to the seas and oceans. This term reflects the fact that Earth's water resources neither increase nor decrease over time. Is the hydrological cycle sustainable today? Could it be delayed due to unnatural processes?

We want to emphasize in this article concerns “liquids in bottles that are discarded”, this is a concern for every individual and whose use has increased relatively in the last 100 years and continues to do so. Changing this practice is the responsibility of every individual.

When we were about to throw away the last quarter liter of drinks, we realized that there was liquid in them (like fresh water and cola in plastic bottles). What should we do? We poured the fresh water into the flowers and the cola into the sink. We could estimate how long that water would remain trapped in plastic bottles. About 200 years. We have always paid attention to this since then, if it becomes more widespread, it will affect all foods containing liquid. Ice left in cold drinks, water wasted with meals... We got very interesting answers when we asked our students. What do you do with the liquids left in plastic bottles? Some give them to aquariums, some to flowers.The total number of people who have lived (and continue to live) in the last 100 years is ~100-110 billion individuals (8.2 billion of them are still alive). How many of these individuals discard plastic bottles containing potable water? Moreover, plastic, which has entered human society in recent years, has another negative effect on natüre, i.e. the lack of decomposition These plastic bottles trap potable water. The question to be answered concerns how much water a person may waste by entrapment in plastic bottles throughout their lifespan? The answer is likely to be a staggering amount!Isn't throwing water in the trash a temporary interruption to the water cycle? Which is more important - freeing water or recycling plastic bottles.

Come on, let's recycle plastic bottles from now on, and free the water inside them to nature.

Nutritional Profile of Economically Valuable Fish Species in the Lake Victoria Basin: Implications for Food and Nutrition Security Among Local Communities

Jonathan Munguti — 2025-04-29

Fish has the potential to help address human nutrient deficiencies but is often underrepresented in nutrition policies and strategies, partly due to a lack of supporting evidence. This study reviews the nutritional profile of economically valuable fish species in the Lake Victoria Basin. It focuses on five key species: Nile tilapia (Oreochromis niloticus), Nile perch (Lates niloticus), Silver cyprinid (Rastrineobola argentea), African catfish (Clarias gariepinus), and lungfish (Protopterus aethiopicus) by assessing their moisture, ash, lipid, protein content, and fatty acid profiles. The study finds that Nile tilapia has a moisture content of 69.36% to 80.03%, protein content of 16.40% to 23.47%, and lipid content of 0.08% to 3.77%, with significant proportions of polyunsaturated fatty acids (PUFAs), particularly omega-3 (18.9% to 33.0%). Nile perch shows similar moisture content (67.30% to 79.6%) and protein levels (15.93% to 22.51%), with lipid content ranging from 0.59% to 4.16%, and PUFAs, especially omega-3 (12.47% to 33.0%). Silver cyprinid displays a wide range in protein (15.44% to 79.44%) and lipid (0.09% to 22.38%) content, and a substantial portion of PUFAs (21.68% to 35.78%). African catfish has consistent moisture (69.16% to 73.54%) and protein (19.93% to 23.06%) levels, with PUFAs making up 29.7% to 36.9%, and a strong omega-3 presence (27.9% to 36.9%). Lastly, lungfish is notable for its high fatty acid content, with 27.7% to 32.5% saturated fats, 20.8% to 26.4% monounsaturated fats, and 35.2% to 49.2% polyunsaturated fats. PUFA N-3 ranges from 13.0% to 27.9%, and PUFA N-6 ranges from 11.7% to 30.0%. While nutrient profiles vary due to environmental, dietary, and biological factors, these five species are consistently nutrient-dense. Thus, promoting the sustainable harvesting and consumption of these fish can contribute substantially to improving dietary quality and nutrition security in communities reliant on Lake Victoria’s fisheries.

Marine Fish Drying in Major Drying Yards: An Explorative Study in the Bay of Bengal of Bangladesh

Amir Hamja — 2025-04-30

The study investigated detailed drying yard infrastructures, processing conditions, raw materials quality, spot quality defect point, packaging, storage, marketing, profit margin and production of commercially important marine fish species in major drying hubs of Cox's Bazar district. In Moheshkhali, Thakurtala (0.81 ha), Ghotibhanga (47.5 ha), and Sonadia yards (250 ha) identified 19±4, 71±3, and 250±11 active processors respectively. Shaporirdip (28.25±6.13 ha) and Shamlapur yards (21±5 ha) had 38±2 and 45±2 active processors respectively from Teknaf, and Chowfalldandi drying yards covered 97.5±13.23 ha, with 143±10 active processors from Cox`s Bazar sadar area. The Nazirertek area included two drying yards: Nazirertek, the largest at 2259.26 ha with 1328±75 active processors, and Nunierchara, a smaller yard (0.340±09 ha) with 3±0 active processors used for processing of dry fish. For 1 kg of finished dried products, the average quantity of raw fish required were 3.25±0.3 kg for pomfret, 3.7±0.25 kg for jewfish/croaker, 2.8±0.02 kg for mackerel, 4.5±0.2 kg for sardine, 4.01±0.2 kg for anchovy, 5.5±0.3 kg for Bombay duck, 3.9±0.2 kg for shrimp, 4.04±0.3 kg for skipjack tuna, 3.7±0.3 kg for sea catfish, 3.7±0.3 kg for shark, and 3.6±0.1 kg for other small pelagic species. The percentage of salt used ranged from 3% to 16%, and the average freshness quality defect point of raw material fish ranged between 1.38 to 3.3 depending on species. Dried fish processors used mostly traditional methods for raw material handling, processing, packaging, storage, and marketing of dried fish products. A total of 42,566 metric tons (MT) of marine dried fish production was recorded in the surveyed Cox’s Bazar region. The average profit margins (%) of major sun-dried fish species were as follows: for pomfret 26 ±3, jewfish/croaker 25±1, mackerel 26±2, sardine 24±2, anchovy 25±5, bombay duck 28±3, ribbon fish 33±13, shrimp 14±0.3, shark 12±4 and for other species 11±6. The government and policymakers may find the results useful in planning and implementing the subsequent phases required for development and for the stakeholders in improving the quality, processing, storage, marketing and export of dried fish. Furthermore, this research may contribute to understanding the dynamics of Bangladesh's fish drying industry and its potential for sustainable development.

Marmara Lake (Manisa-Türkiye)’s Final Waters: Assessment of Water Quality Parameters and Trophic Status Before Near-Total Drying

Saniye Türk Çulha — 2025-04-29

This study was carried out at 3 different stations in Marmara Lake, in Western Anatolia in Türkiye, and focused on variations in water quality parameters based on months. Water samples collected from the surface of the lake were analyzed monthly in terms of total suspended solids (TSS), volatile suspended solids (VSS), fixed suspended solids (FSS), ammonium nitrogen (NH₄⁺-N), nitrite nitrogen (NO₂^--N), nitrate nitrogen (NO₃^--N), phosphate phosphorus (PO₄^-3-P), silica (SiO₂) and chlorophyll-a (Chl-a) parameters. As a result of this study, according to Inland Water Quality Standards defined in Surface Water Quality Management Regulations (SWQMR), Marmara Lake can be considered the Class-I quality by the measured ammonium nitrogen and nitrate nitrogen and the Class-II by the measured nitrite nitrogen and phosphate phosphorus. Moreover, it was evaluated that the lake is in a eutrophic status according to its Carlson’s trophic state index (TSI) scores based on the phosphate phosphorus values, and in a hypereutrophic status based on the chlorophyll-a values. This study presented the latest scientific research evaluating the surface water quality parameters and trophic levels of Marmara Lake before its complete drying. In this respect, the study has historical importance in documenting the lake's final ecological state and will be able to create a critical reference point for potential restoration efforts.

Antibiofilm Activity and Chemical Profiling of Biomolecule Extracts from Marine Sediment Bacteria

Ayse Kazan — 2025-04-29

Some of the secondary metabolites in the marine ecosystem control the adhesion of microfouling microorganisms to surfaces, thereby exhibiting antibiofilm properties. The main objective of this research was to understand the antibiofilm and antibacterial activity of biomolecule extracts of bacteria from marine sediments. Each complex and pure biomolecule was evaluated for inhibition effects against two marine biofilm bacteria using the antibiofilm activity assay. The maximum activity of the biomolecules in preventing bacterial adhesion was determined to range between 68.59 percent and 91.84 percent for Pseudoalteromonas agarivorans and between 15 percent and 65.68 percent for Exiguobacterium homiense. Additionally, the antibacterial activity of biomolecule extracts against four marine biofilm bacteria was tested by the minimum inhibitory concentration method. The strongest minimum inhibitory activity of pure extract (0.78 mg/mL) from Bacillus simplex was recorded against Alteromonas genoviensis. Research has also focused on the determination of compounds such as alkaloids, phenolics and flavonoids in the structure of biomolecular extracts using spectrophotometric analysis. It was concluded that the pure biomolecules isolated from sediment bacteria are predominantly composed of alkaloids. These novel microbial biomolecule extracts could be used as sources to produce antibiofilm and antifouling products.

Effects of Agricultural Carbon Sources On Water Quality and Phytoplankton Community Composition in Flocponic System

Kenneth Rono — 2025-04-29

Carbon products promote aggregate floc-rich plankton, with diverse roles in flocponic production. Availability, low-cost, and chemical composition of agricultural by-products make them ideal substrates for phytoplankton production. Phytoplankton maintains water quality by reducing toxic substances, but it is problematic under some conditions. Therefore, the study evaluates how agricultural carbon sources affect flocponic phytoplankton community composition and water quality. Five treatments (wheat-bran, Rhodes-hay, maize-cob, maize-stables, and lucerne-hay) and a control (no by-product) were employed in a complete randomized design, each in triplicate for nine weeks. Each treatment and control had Nile tilapia (0.155 ± 0.01 g) and rice (seeds) densities of 98 m^-3 and 250 m^-2, respectively. Temperature, pH, dissolved oxygen, and salinity levels did not differ significantly between treatments and control. However, TDS, soluble reactive phosphorus (SRP), ammonia, nitrite, and nitrate showed significant differences (p<0.05) between treatments and control. Lucerne-hay exhibited the highest nitrate levels (0.9 ± 0.06 mg L^-1), SRP (0.6 ± 0.05 mg L^-1), and the lowest ammonia and nitrite levels compared to other treatments and control. Lucerne-hay had the highest phytoplankton diversity (2.48), while the control (1.37) had the least. Further, there were significant differences in phytoplankton abundance, with lucerne-hay having the highest Charophyta (1.45 ± 0.02 indsL^-1), Chlorophyta (1.60 ± 0.02 indsL^-1), and Ochrophyta (1.64 ± 0.03 indsL^-1) abundance, while the control had the least. The result of the study revealed that carbon sources influence flocponic water quality and phytoplankton. The composition and solubility of lucerne-hay and wheat-bran may have improved water quality and phytoplankton. The study suggests that lucerne-hay and wheat-bran are the best flocponic carbon sources for phytoplankton and water quality.