MARINE REPORTS (MAREP)

From biowaste to blue food: insect-driven aquaculture

2025-10-30T16:22:22+03:00

Aquaculture has gained significant momentum in recent years in meeting global protein demand. As one of the principal factors, the latest technological innovations, have also brought about significant challenges. These problems, including high costs, supply constraints and environmental risks arising from continued dependence on traditional feed ingredients such as fish meal and soybean meal have accelerated the search for sustainable and innovative protein sources. Correspondingly, insects, historically part of both human and animal diets, have re-emerged as viable feed resources. Although insect meals are quite rich in terms of high protein, essential amino acids, fatty acids, minerals and bioactive components, which are among the most important advantages of fish feeds in aquatic diets, they also bring about difficulties such as digestibility and variability in micronutrient composition due to their high fat and chitin content. However, technological innovations such as defatting, enzymatic hydrolysis, fermentation and modification of rearing substrates used to combat these difficulties increase the digestibility and productivity of insects and further increase their use in aquaculture feeds. In addition, safety of feeds, better waste-management, regulative changes and public acceptance can be considered as other factors shaping the future of insect feeds in the sector. As a result, increasing insect production capacity and making innovations in processing technologies will significantly improve nutritional content functional properties of insect-based feeds. This process will enable the conversion of low-value biological waste into high-value blue food products, making circular bioeconomy principles practically applicable and will put aquaculture as a resilient and sustainable food production system with a low environmental footprint in the future.

Diversity and spatio-temporal dynamics of Caulerpa J.V.Lamouroux, with two new locality records from Northern Sri Lanka

2025-12-03T18:17:09+03:00

The genus Caulerpa is a key component as a primary producer of tropical and subtropical marine ecosystems, yet its diversity and distribution along the northern coast of Sri Lanka remain poorly documented. This study provides a comprehensive assessment of the diversity and spatio-temporal dynamics of Caulerpa species at four coastal sites, Mandaitivu, Mathagal, Kankesanthurai, and Point Pedro from July 2024 to June 2025. Monthly sampling using the quadrat-transect method revealed six species: Caulerpa lentillifera, Caulerpa racemosa, Caulerpa sertularioides, Caulerpa taxifolia, Caulerpa serrulata, and Caulerpa peltata. Among these, C. lentillifera and C. serrulata are reported as new locality records for the Jaffna region, while the distributions of C. taxifolia and C. peltata are significantly expanded. C. sertularioides was the most widespread and dominant species, occurring at all sites, whereas C. lentillifera and C. taxifolia were rare, each found at only one location. Distinct seasonal patterns were observed, with a complete absence of all species during the northeast monsoon (November–December). Mandaitivu exhibited the highest diversity overall, with peak Simpson diversity (0.375) and evenness (0.946) in March and maximum Shannon diversity (1.121) and species richness (4) in June. Canonical Correspondence Analysis indicated that the growth and distribution of Caulerpa species along the northern coast of Sri Lanka are mainly influenced by salinity, temperature, nutrient availability, dissolved oxygen, turbidity, and seasonal monsoonal variability. This study establishes the first detailed baseline of Caulerpa diversity in northern Sri Lanka, highlighting its ecological significance and providing a foundation for future conservation and bioprospecting efforts.

Evaluation of fish production, gross domestic product and food security in countries bordering the Mediterranean Sea

2025-10-29T18:17:31+03:00

The aquaculture industry contributes significantly to the economic growth of countries, both in terms of food security and sectoral economic gains. This study examines the relationship between marine fish farming and the economic growth and food security of countries bordering the Mediterranean. Data from 10 Mediterranean countries was evaluated between 2012 and 2022. To ensure co-integration in dynamic forecasts, fish export and import values, gross domestic product, and food security index were examined by countries around the Mediterranean Sea, and the correlation between these data was assessed on a country-by-country basis. Findings in the present study addressed a strong correlation between marine fish production and gross domestic product for Türkiye (R= 0.91), Egypt (R= 0.93), and Spain (R= 0.91), with moderate correlation for Morocco (0.61), and Greece (R= 0.60). Also, high correlation was found between export and gross domestic product for Türkiye (R= 0.97) and Morocco (R= 0.78), and moderate correlation for Greece, France, Spain, and Italy (R= 0.63, R= 0.61, R= 0.60, and R= 0.55, respectively). Strong correlation between fish import and average dietary energy requirement was recorded for Morocco, Italy, France, and Spain (R= 0.85, R= 0.83, R= 0.82, and R= 0.74, respectively), whereas moderate correlation was found for Türkiye (R= 0.62), and remarkably lower correlation for Greece and Egypt (R= 0.41, R= 0.25, respectively). Results of this study provide remarkable information that may help policymakers and aquaculture managers in promoting new aquaculture investments by economic strategies for improving fish production and achieving long-term food security the Mediterranean, supplying a significant amount of the global food demand.

Evaluation of the efficacy of a bivalent inactivated whole-cell vaccine against Edwardsiella tarda and Vibrio anguillarum in Tilapia (Oreochromis niloticus)

2025-12-18T19:44:58+03:00

Bacterial co-infections constrain tilapia aquaculture. We evaluated the efficacy of an adjuvant-free, formalin-inactivated bivalent whole-cell vaccine combining Edwardsiella tarda and Vibrio anguillarum in Nile tilapia. Fish received the bivalent formulation, matched monovalent vaccines, or phosphate-buffered saline. Systemic and skin-mucus immunoglobulin M levels were quantified by indirect enzyme-linked immunosorbent assay, and serum and mucus bactericidal activity were assessed at 1, 7, 14, and 21-days post-vaccination. At 21 days post-vaccination, fish were challenged intraperitoneally with E. tarda or V. anguillarum, or both. By 14–21 days post-vaccination, the bivalent vaccine induced strong systemic and mucosal immunoglobulin M responses and increased bactericidal activity; across readouts, responses were significantly greater than (p < 0.05) or equal to (p > 0.05) the corresponding monovalent vaccine. After challenge with E. tarda, 21-day post-challenge survival was higher in the bivalent (54.17%, Relative Percent Survival = 38.9%) than in the monovalent (29.17%) or control (25.00%) group (both p < 0.05). After V. anguillarum challenge, survival was similar in the bivalent (87.50%, Relative Percent Survival = 78.6%) and monovalent (75.00%) groups (p > 0.05), both of which showed greater survival than the control (41.67%) (p < 0.05). After mixed E. tarda + V. anguillarum challenge, survival was significantly higher (50.00%, Relative Percent Survival = 47.8%) in the bivalent group than in the control group (4.17%) (p < 0.05). No acute adverse reactions or behavioral abnormalities were observed. These findings indicate that an adjuvant-free bivalent vaccine elicits robust mid- to late-phase humoral responses and provides broad protection without evidence of antigenic interference, supporting a practical polyvalent strategy where E. tarda and V. anguillarum co-circulate.

Competitive trends of Atlantic bluefin tuna farming among major Mediterranean producers, with special emphasis on human capacity by population growth

2025-10-20T17:53:03+03:00

This study aims to investigate the economic dynamics among five major tuna producing countries in the Mediterranean: Malta, Spain, Türkiye, Croatia and Tunisia which provide significant amounts of tuna for the growing demand in the market network. Major drivers of the tuna farming were identified based on annual production yields provided by FAO statistics. The growth trends and economic development of the tuna production industries in the three key producers of tuna have been evaluated and superimposed with the increasing trends in population densities between 2006 and 2023. Tuna harvests from farms in Malta increased around 3-fold from 6,069 to 18,623.7 tons between in 2006-2023, while in Spain approximately 4-fold increase was noted in the last 18 years, from 2,572 to 10,652.8 tons. Among the five major producers in the Mediterranean, Türkiye increased its harvest by 9.4-fold between the same years, reaching 3,674 tons in 2023 from the relatively low level of 390 tons in 2006. Tunisian production increased by 3.2-fold from 450 to 1,439 tons between 2006-2023, whereas Croatian tuna farming declined by 0.49-fold from 6,700 to 3,242 tons over the past 18 years. In terms of economic gain, tuna producers of Malta achieved around 9% higher economic gain than Spain, and around 72, 83, and 94% higher economic efficiency than Croatia, Türkiye, and Tunisia, respectively. Considering the importance of skilled labor in production, the relationship between harvest volumes and population growth by country was examined through correlation. Strong correlation between production and population growth was observed in both Malta and Türkiye over the 18-year period (R=0.91, Malta; R=0.90, Turkey), whereas no such strong correlation was found in Spain (R=0.68), followed by Tunisia (R=0.49) and Croatia (R=0.14) for the same years of investigation. The results of this study highlight the importance of manpower in the production and operational processes of the aquaculture industry, in addition to other factors. Furthermore, considering the need for more comprehensive studies on human capacity in aquaculture, findings of the present study shed light and encourage future research.