THE EFFECTS OF MARINE PROTECTED AREAS ON THE ECOSYSTEM IN THE EASTERN MEDITERRANEAN

Date

2024-9-4

Author

Eşkinat, Deniz

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Marine Protected Areas (MPAs) are primary tools for restoring degraded marine ecosystems affected by various stressors. Although numerous studies have acknowledged and demonstrated their effectiveness, their effects and efficacy in areas under intense pressure from non-indigenous species (NIS), such as the Eastern Mediterranean, have been debated. Therefore, filling this gap by investigating their effects is important for properly establishing MPAs and implementing effective management plans. Within this scope, the effects of protection measures on the ecosystem in a region that was degraded at the end of the 1980s due to the intense fishing pressure were investigated. The study primarily focuses on a time series from 1983 to 2023, reflecting the status of commercially exploitable adult fish populations before and after the establishment of the protected area. Data on biomass and species numbers collected from demersal trawl surveys both within and outside the partially protected Fisheries Restricted Area (FRA) were analyzed to assess the impact of conservation measures on fish populations and NIS. The second focus was on juvenile and young-of-the-year fishes within the fully protected No-Take Zone (NTZ), spanning two distinct time periods: (i) the initial years of conservation efforts and (ii) 20 years after their implementation. Observations recorded through underwater visual census in vulnerable nursery areas within the shallow infralittoral zone, inside and outside the NTZ, were analyzed to evaluate changes in biodiversity over time and the effects of conservation measures on NIS. It was determined that fishing restrictions within the FRA positively affected the exploitable fish stocks, with biomass values showing a recovery over the years. Additionally, although NIS have increased both within and outside the FRA, their biomass has been found to be lower within the FRA, indicating that protection measures have slowed the spread of NIS. These results highlighted the crucial role of conservation strategies in mitigating the NIS and restoring the ecosystem. On the other hand, the NTZ exhibited different results. High indigenous species (IS) diversity was initially observed within the NTZ in the early years of the implemented protection measures. However, observations conducted 20 years later indicated a shift: a decrease in IS diversity was observed, and an increase in the diversity and success (which was estimated based on species richness and evenness) of NIS was noted. In contrast, IS diversity outside the NTZ maintained its status throughout the two periods, and NIS did not show success as they showed within the NTZ. Their low diversity and success are attributed to small-scale fishing activities, which targeted these NIS, thereby controlling their populations. However, without such control within the NTZ, they benefited from the conservation measures and gained an advantage. Additionally, (i) the disappearance of IS within the NTZ over the years, which shared the infralittoral zone and (ii) the reduction in success and diversity of the IS were attributed to the disruption IS’ habitat dynamics caused by the introduction of NIS to the ecosystem. These contrasting results between the FRA and NTZ indicate that the impact of conservation efforts on the NIS may vary depending on the habitat structure being protected, the structure of fish groups within the protected area, and the level of protection measures implemented. These findings also may suggest that fisheries may be utilized to mitigate the impacts of NIS in the areas facing high NIS pressure. Additionally, when establishing MPAs in NIS-impacted ecosystems such as the Eastern Mediterranean, with the only aim of enhancing biodiversity or rebuilding fish stocks, it is crucial to consider the effects of NIS in the planning process to ensure the effectiveness of these conservation efforts.

Subject Keywords

No-Take Zone (NTZ), Fisheries Restricted Areas (FRAs), Non-Indigenous Species, Demersal Trawl, Visual Census, Biodiversity

URI

https://hdl.handle.net/11511/111319

Collections

Graduate School of Marine Sciences, Thesis