Loggerhead sea turtles

Long-Term Data Reveals Rising Ghost Gear Threat to Mediterranean Loggerheads

Loggerhead sea turtles ( *Caretta caretta*) in the Western Mediterranean Sea face escalating threats from abandoned, lost, or discarded fishing gear (ALDFG).

September 10, 20265 min readFrontiers in Marine Science | New and Recent Articles

Long-Term Data Reveals Rising Ghost Gear Threat to Mediterranean Loggerheads

Our take

The escalating crisis of marine debris, particularly abandoned, lost, or discarded fishing gear (ALDFG), continues to pose a significant threat to vulnerable marine species worldwide. Recent research, highlighted by a compelling new study focusing on loggerhead sea turtles in the Western Mediterranean Sea, provides crucial data quantifying this threat and, importantly, beginning to trace its origins. This study builds upon previous investigations into marine ecosystem impacts, such as the exploration of hypoxia survival in Bull sharks [How long can a Bull shark survive without any blood in the brain aka hypoxia?] and the ongoing efforts to improve sustainability within commercial salmon farming through optimized feed composition [Higher dietary EPA & DHA levels improve commercial salmon farming productivity, predictability and sustainability]. The convergence of these research areas underscores a broader imperative: understanding and mitigating human impact on marine ecosystems requires a multifaceted approach, integrating physiological studies with ecological assessments and operational analyses of resource management.

The 28-year dataset examined in this new study, encompassing over 1,000 loggerhead turtle stranding records, reveals a concerning trend of increasing entanglement events, particularly since 2018. While short-term mortality rates from entanglement appear relatively low (19.1%), the severity of injuries – including debilitating limb loss – highlights the long-term ecological consequences for these endangered turtles. The identification of fish aggregating devices (FADs) as a primary source of entanglement debris (35.8% of identified cases) is particularly significant, as FADs are often deployed across vast areas and can persist in the ocean for extended periods. The innovative use of Lagrangian backtracking simulations to trace the origin of ghost FADs, suggesting a transboundary nature of the problem with gear originating from multiple countries, represents a substantial advancement in our understanding of ALDFG movement and impact. This approach offers a powerful tool for identifying and targeting sources of pollution, moving beyond simple observation to a more proactive management strategy. It’s a welcome shift from reactive responses, aligning with the broader need for preventative measures, as evidenced by the ongoing research into whale mortality patterns in San Francisco Bay [Correction: Gray whales (Eschrichtius robustus) in San Francisco Bay experience high mortality and have limited affiliation to known foraging groups].

The study’s findings underscore the critical need for a coordinated, international approach to managing fishing gear and reducing ALDFG inputs. The Mediterranean Sea, a densely populated and heavily fished region, is particularly vulnerable to this problem. The transboundary nature of the ghost gear identified necessitates collaboration among nations to implement effective mitigation measures, such as improved gear marking and retrieval programs, stricter regulations on FAD deployment, and promotion of sustainable fishing practices. Furthermore, the integration of real-time data and predictive modeling, as demonstrated by the Lagrangian simulations, can enable more targeted interventions and adaptive management strategies. This approach aligns with the principles of ocean intelligence, emphasizing the use of integrated data ecosystems to inform decision-making and promote ocean stewardship. The validated, empirical data provided by this study strengthens the case for policy changes aimed at reducing the environmental impact of fishing activities and safeguarding vulnerable marine megafauna.

Looking ahead, the development of standardized methodologies for tracking and tracing fishing gear across international waters will be crucial for effective management. The success of Lagrangian backtracking simulations hinges on robust data collection and sharing, requiring commitment from multiple stakeholders. Further research should focus on quantifying the economic costs associated with ALDFG, including damage to fishing gear, reduced tourism revenue, and the expenses related to turtle rescue and rehabilitation. Ultimately, the long-term ecological health of the Mediterranean Sea, and countless other marine environments, depends on a collective willingness to address the root causes of ALDFG and implement sustainable practices that prioritize ocean health alongside economic interests. What mechanisms can be developed to incentivize responsible gear disposal and retrieval, moving beyond regulatory mandates to create a system where stewardship is inherently rewarded?

Loggerhead sea turtles (Caretta caretta) face multiple anthropogenic threats, including entanglement in abandoned, lost, or discarded fishing gear (ALDFG). Using a unique 28-year dataset (1993-2020) of sea turtle stranding records from the Balearic Sea (Western Mediterranean, n = 1,057), we aim to (i) evaluate long-term trends in strandings and entanglement events, (ii) identify the debris responsible for entanglement, and (iii) investigate the potential origin of ghost fishing gear through the integration of stranding records and Lagrangian backtracking simulations. Overall strandings increased over time, with seasonal peaks in summer and autumn. Entanglement-related cases escalated from 2018 onwards, peaking at 47 in 2020. Although entanglement presented low short-term mortality (19.1%) in comparison to other casualties, it caused severe injuries, including partial or complete loss of flippers in 16.8% of cases. In-depth analyses of entangling debris from 2014–2020 revealed that fishing-related items, particularly from fish aggregating devices (FADs), accounted for most identified cases (35.8%). Lagrangian backtracking simulations provide indications of the origin of ghost FADs. Basin-scale simulations suggest that ghost fishing gear observed across the Western Mediterranean Sea may derive from multiple countries, highlighting its transboundary nature. By applying Lagrangian backtracking simulations to ghost fishing gear observations and entanglement records, this study provides new insights into the potential origin and connectivity of ghost FADs in the Western Mediterranean Sea. These findings identify ghost FADs as a regionally significant threat to loggerhead turtles, with both immediate and long-term ecological consequences. Our study underscores the need for coordinated international management, targeted mitigation measures, and sustainable fishing practices to reduce ALDFG inputs and protect vulnerable marine megafauna in the Mediterranean Sea.

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