MARINE REPORTS (MAREP)

Some observations on the abundance and biomass of Elasmobranch fishes captured over stratified bottom trawl surveys from the special environmental protection area of Datça-Bozburun (Türkiye)

2025-06-16T23:16:51+03:00

This study investigates the abundance and biomass of elasmobranch fishes (sharks and rays) within and outside the Datça-Bozburun Special Environmental Protection Area (SEPA) in Turkey, using data from stratified bottom trawl surveys conducted in 2009-2010. Elasmobranchs, a vital group in marine ecosystems, are increasingly at risk of extinction due to various anthropogenic threats, particularly overfishing. This research addresses the decline of elasmobranch populations in the Turkish Seas, where they have become increasingly scarce. The methodology involved six trawl hauls at depths greater than 100m, covering a total area of 1.20 km2, and the standardized catch per unit trawling area was calculated to estimate abundance and biomass. The Shannon-Wiener diversity index was used to assess species diversity within and outside the SEPA. Key findings reveal differences in elasmobranch communities inside and outside the protected area. Implications of the study emphasize the importance of marine protected areas for elasmobranch conservation in the face of overfishing and habitat degradation. The results of this study can be used in future assessments and fisheries management strategies.

Updated review of the seaweed farming initiatives in the Colombian Caribbean for its sustainable development considering regional and national contexts

2025-03-24T11:23:47+03:00

An updated review of the contexts of seaweed farming in the Great Caribbean and Colombia was analyzed. Fifteen countries made trials with native species getting limited results. Eleven countries introduced the non-native species Kappaphicus alvarezii to get better performance and quality products in the Caribbean and Brazil. 619 native macroalgae species are reported so far in the Colombian Caribbean (CC), and seaweed farming were at experimental trials so far. Most viable hypothesis is that K. alvarezii was possibly introduced in 1991 in Colombia for seaweed farming. Environmental considerations showed several species aggregated with seaweed farming with no significant effects in the environment; aquaculture considerations show challenges with weather conditions, epiphytism, herbivorism, among others, but still easy and inexpensive. Legal considerations are still complicated for the marine aquaculture, but social considerations showed a great potential as an alternative for vulnerable ethnic coastal communities. An analysis of K. alvarezii as an invasive species revealed that the species did not show any invasive behavior in the CC after several years of being introduced, despite several weather events that washed up cultivation trials and may allowed the species to be expanded in the whole area. No technical evidence was confirmed to declare the species as an invasive species in Colombia, despite being declared noninvasive in other Caribbean countries.

Marine spatial planning: a cautionary tale

2025-05-18T22:02:53+03:00

Marine Spatial Planning (MSP) has emerged as a key instrument for governing marine spaces within the evolving paradigms of the blue economy, blue growth, and ecosystem-based management (EBM). This paper critically surveys the conceptual and practical dimensions of MSP by framing it within the context of wicked problems—ill-defined, complex, and socially embedded challenges that resist definitive solutions. Through a synthesis of literature across marine governance, participatory planning, and creative problem solving, the study identifies key barriers to effective MSP, including stakeholder fragmentation, short-termism, and cognitive bias, and explores how tools such as scenario planning and dialogue mapping can help address these barriers. The paper presents a conceptual framework that clarifies the interrelations among the blue economy, blue growth, and MSP, and critiques how current implementations risk reinforcing power asymmetries and marginalising vulnerable stakeholders. By positioning MSP as a creative, adaptive, and participatory response to complexity, the paper offers a cautionary perspective and practical insights for improving marine governance.

Ecological and geopolitical challenges in sustaining global fishmeal supply for aquaculture

2025-05-26T18:40:18+03:00

Aquaculture plays a pivotal role in addressing global food security, particularly as wild-capture fisheries approach ecological saturation and can no longer meet rising nutritional demands. Fishmeal—valued for its high-quality protein profile—has emerged as a critical feed component, yet its continued use raises pressing concerns linked to ecological degradation and growing geopolitical uncertainty. This paper explores the structural vulnerabilities of the global fishmeal supply chain, drawing attention to the overharvesting of forage fish, climate-induced stock instability—reflected in a roughly 40% decline in production between 2013 and 2023—and the compounding effects of trade restrictions, including U.S.–China tariff escalations (2023–2025) and regional import bans. Unsustainable exploitation of pelagic species threatens marine biodiversity and disrupts ecological trophic networks, while global crises such as pandemics and maritime transport bottlenecks further expose fragilities in the system. In synthesizing these dynamics, the review calls for a transition toward ecosystem-based fisheries governance, geographically decentralized feed production, and strategically resilient supply chains. The analysis concludes with policy imperatives that prioritize international cooperation, anticipatory regulatory mechanisms, and adaptive management strategies to mitigate converging risks to aquaculture’s long-term sustainability.

Effects of some common bacterial fish diseases on fish behavior in aquaculture: a Review

2025-04-11T18:12:20+03:00

Aquaculture is of increasing importance and economic value in global food production. Sustainability and productivity of aquaculture are directly related to the health of the fish farmed. Bacterial diseases in fish are common in the aquaculture sector and cause significant economic losses. Therefore, it is of substantial to understand the agents, prevalence and effects of bacterial diseases on fish health. Fish behavior is an important indicator of their health status. Behavioral changes can be an early sign of disease and therefore careful observation is vital for timely diagnosis and control of diseases. This review discusses common bacterial fish diseases, their agents and specific behavioral changes observed in infected fish. In addition, potential mechanisms by which bacterial infections affect fish behavior are examined.