From invasive rabbitfish to recovering predators, Dr Isobel Ollard shows how evidence from Gökova Bay to Cape Gelidonya is shaping marine restoration in Türkiye and beyond.
Along Türkiye’s Mediterranean coast, a stretch of sea where the Central Aegean meets the North East Levantine basin, ecosystems are under growing pressure. These waters, home to species such as sandbar sharks, monk seals and loggerhead turtles, also support the livelihoods of thousands of coastal fishers. But rising sea temperatures, habitat damage from tourism, and the spread of invasive species migrating from the Red Sea are altering marine food webs and pushing traditional fishing practices to the margins.
The Gökova Bay to Cape Gelidonya marine restoration project, led by AKD and Flora & Fauna, has been monitoring key indicators for the past six years to shed light on the effects and effectiveness of restoration efforts. These indicators track changes at multiple timescales, from immediate responses to project actions to the slower shifts that mark ecosystem recovery. You can explore the full set of indicators on the Measuring Impact Hub. By tracking ecological and socio-economic indicators side by side, the project is beginning to show how different changes link together to shape recovery across the seascape.
Invasive species reshaping the seascape
One of the key challenges facing marine ecosystems in Gökova Bay area is the arrival and rapid spread of invasive species from the Red Sea. Since the opening of the Suez Canal, these ‘Lessepsian migrants’ (named after Ferdinand de Lesseps, who oversaw the canal’s construction) have been able to move into the Eastern Mediterranean. Many outcompete native species, disrupting ecological balance. Herbivorous invasives such as rabbitfish (Siganus spp.) graze on seagrass and macroalgae habitats, removing food and shelter for native species and leading to biodiversity loss. This has economic consequences too, as invasive fish, often with little market demand, make up an increasing share of fishers’ catches.
Recognising this, the project has combined ecological and market-based interventions to tackle the issue.
No-fishing zones: protecting and rebuilding the food web
One major measure has been working with government to establish and enforce No-Fishing Zones (NFZs), the most stringent form of Marine Protected Area. In these areas, commercial fishing, and sometimes recreational fishing, is banned, giving fish populations a chance to recover. Over time, No-Fishing Zones can produce “spillover effects”, with fish moving beyond protected boundaries, benefiting surrounding fisheries.
Crucially, recovering native predators can help control invasive herbivores, restoring balance to the food web. Monitoring showed a 41% increase in the area protected either as No-Fishing Zones or the less stringent Fisheries Restricted Areas. Enforcement is essential, so AKD tracked patrol coverage, patrol frequency, and the number of actively enforced zones. Despite some fluctuation due to social and logistical factors, all three indicators improved over the monitoring period.
In the two No-Fishing Zones with consistent enforcement, Gökova and Göcek, recorded illegal fishing incidents decreased significantly. Apex species such as sandbar sharks (Carcharhinus plumbeus), of global conservation concern, are also being monitored, with improved video systems expected to provide better long-term data.
To understand whether recovering predator populations were helping to control invasive herbivores, AKD monitored the proportion of total fish biomass composed of rabbitfish, both inside and outside No-Fishing Zones. In the two protected areas with consistent enforcement, Gökova and Göcek, the proportion of rabbitfish biomass was significantly lower inside protected areas than outside. In Gökova in particular, rabbitfish biomass increased outside the protected zone over the monitoring period but did not increase inside, where predator biomass was also higher. This pattern suggests that the recovery of native predatory fish in protected areas is contributing to top-down control of invasive rabbitfish.
Turning invasive fish into an economic opportunity
Alongside designating and enforcing protected areas, the project has also developed a complementary programme to create demand and economic value for invasive species, enabling fishers to sell catches that previously had little or no market worth. The aim is twofold: to reduce invasive fish numbers in the ecosystem and to support the livelihoods of small-scale fishers by opening a new source of income.
To achieve this, AKD collaborated with restaurants and chefs and organised publicity initiatives such as food festivals and tasting events to present invasive fish as high-quality, desirable products. The programme focused mainly on lionfish but also promoted other invasive species including rabbitfish. Success was measured by monitoring the number of restaurants serving lionfish. In Göcek and Kaş, there was a small and statistically non-significant change in restaurants serving lionfish. However, across the wider region, the number of restaurants ordering lionfish directly from AKD increased from four in 2020 to 27 in 2023. This indicates a growing acceptance of invasive fish cuisine and reflects the programme’s success in changing perceptions.
The market price of invasive fish species was also monitored to track the how their value changed as the project progressed. While there was no consistent trend in prices over time, at least five invasive species which had no recorded market value at the start of the project had a market price by 2023, indicating the increasing valorisation of invasives. This rise in price and demand led to an increase in both the number and value of lionfish sales over the period, reflecting progress towards the project’s socioeconomic goals. The impact of this campaign on invasive species abundance in the seascape remains uncertain, but continued monitoring may reveal clearer outcomes in the future.
Long-term recovery: macroalgae and seagrass
The long-term goal is to reduce invasive herbivores enough to allow macroalgae canopies and seagrass meadows, also threatened by boat anchoring, to recover. These habitats are monitored annually for coverage and density both inside and outside No-Fishing Zones. So far, recovery has not been detected, and year-to-year variability remains high. For example, unusually high water temperatures in 2023 coincided with a drop in seagrass shoot density. Because these habitats are slow to regenerate and depend on broader ecological shifts, longer monitoring periods are needed before trends can be identified.
Building evidence for the future
The Gökova Bay project shows how ecological and socio-economic indicators can be linked to track restoration progress in complex marine systems. The interplay between No-Fishing Zone enforcement, predator recovery, invasive species control, and fisher livelihoods highlights the value of combining protection with market incentives.
While some indicators show encouraging trends, others will require longer timeframes to detect change. Continued monitoring will be essential, not only to understand how ecosystems in Gökova Bay respond but also to provide insights for marine restoration more widely. Evidence gathered here can strengthen the case for effective enforcement, inform the design of market-based approaches, and contribute to the global evidence base on how to manage invasive species and support sustainable fisheries.
By building a clear picture of both ecological and socioeconomic outcomes, the project is helping to guide restoration in this region and offering lessons that can be applied across the Mediterranean and beyond.
