a fragile ecosystem, facing multiple threats
Despite being protected by national, European, and international legislation, the health of this increasingly fragile ecosystem and the rich biodiversity dependent on it, is cause of concern.
(Threats listed in alphabetical order)
The term ‘Bycatch’ refers to marine life that is unintentionally caught while fishing for a specific target species. In Amvrakikos Gulf, trawling and seining are prohibited with only small-scale fishing vessels operating using set nets like trammel and gill nets, with a few employing demersal longlines.
Sharks and rays are caught either as bycatch or target, but the type of gear used significantly impacts the size and age of these individuals. The presence of a high number of immature individuals of elasmobranchs interacting with fishing activities is attributed to the nursey character of the Amvrakikos Gulf, acting as an enclosed protected area for species. The survival after capture of these magnificent marine animals is influenced by various factors, including the species and the gear used. Key to their well-being is minimizing air exposure and ensuring careful handling during disentanglement and release. Even though, so far results, indicated that the at vessel mortality per species is lower than 20% for specific fishing métiers (trammel nets), trend of improvement of the health condition during post-release of these species, highlight this management strategy as of fundamental importance for conservation. Thus, it is crucial to tailor management actions, focusing on the education of fishers on proper handling and release techniques in order to reduce air-exposure and improve handling.
Predation and damage to their fishing nets by bottlenose dolphins are frequently reported by local fishers working in the Gulf; nevertheless, many of them describe dolphins as ‘special’ animals, defining them as intelligent and beautiful. Accordingly, the occurrence of intentional killing of dolphins by fishermen as a form of retaliation or culling was never reported in recent years. Although there are no strong indications of incidental dolphin bycatch being a strong cause of concern in the Gulf, unfortunately these incidents may occasionally happen.
Incidental capture in fishing gear (i.e. the unintended capture) is one of the threats having the highest impact on sea turtles occupying Amvrakikos. When turtles are accidentally caught in fishing nets, they are unable to reach the surface to breathe causing them to drown. Mortality may reach 80% of such cases. Other lethal incidents can occur by ingestion of hooks and fishing lines. Intentional killing or injuring bycaught sea turtles has been reported in the past but it is rather rare.
Collaboration with local fishers is key to the long-term protection of these vulnerable species inhabiting the Amvrakikos Gulf.
Good practice guides on reducing the incidental catch of vulnerable species. These guides were produced with the aim of reducing incidental catches of vulnerable species (cetaceans, seabirds, sharks and rays, sea turtles).
Climate changes including rising sea levels, altered rain patterns, drought, and ocean acidification threaten to degrade coastal habitats. Rising sea levels will move ocean and shorelines by inundating lowlands, displacing wetlands, and altering the tidal range in rivers and bays.
Climate change and its effects on fresh water availability is expected to negatively affect breeding waterbirds. Increasing demands on fresh water for irrigation and hotter summers are expected to reduce available breeding sites within the reedbeds of Amvrakikos.
Due to the decreased water salinity brought upon by climate change, dolphins can develop patchy and raised skin lesions across their bodies (some dolphins in Amvrakikos have already manifested different kinds of skin conditions). Moreover, the stress caused by changes in their environment can weaken the animals’ immune systems, making them more susceptible to diseases as well as to affectem by reducing their reproductive success. Climate change directly impacts the foraging opportunities of dolphins since it is also likely to lower prey availability.
Ocean warming may also affect different elasmobranch species in various ways. It’s unlikely that elasmobranch species will be able to evolve to adapt to relatively quick changes caused by climate change ands acidification. Therefore, they will have to deal with these stressors through changes in behaviour and distribution. For instance, warmer ocean temperatures can cause a decrease in the mineralization of pectoral fins in skates, which makes them less stiff. With more flexible pectoral fins, skates need to spend more energy to achieve the same speed.
Local fisheries, an important part of the area’s socioeconomics, are no exception and they are also threatened by climate change. Changes in chemical and physical conditions of the ocean, such as changes in sea surface temperature and ocean acidification, can be expected to affect fisheries catches because of changes in food webs, productivity, and the spatial distribution of fish species that respond to these effects.
Hunting, illegal fishing, recreational boating and fishing, un-regulated dolphin watching
Human activities in the Gulf of Ambrakikos over the past decades have largely affected the area. Upstream dams and river canalisations have reduced the availability of sediment and as a result there is significant corrosion in breeding islets, dykes and the coast line that reduce the available habitat for a number of waterbirds including the Dalmatian Pelican. Hunting, both legal and illegal has affected the area for decades. Illegal hunting is notoriously common in the area all times of the year including during the breeding period. Relatively recent legislations have allowed hunting to take place within pockets of the national park, fragmenting the protected area and reducing its quality as a winter refuge for visiting waterbirds.
Overhead electricity transmission wires are a significant mortality threat for waterbirds especially Dalmatian Pelicans, a number of which is found dead on an annual basis due to collision.
Recreational boating, likely to increase in the early future as a consequence of local marinas being upgraded and new facilities being developed for the nautical sector, poses a potential threat to bottlenose dolphins in the Gulf of Ambracia as a consequence of boat traffic and disturbance. Moreover, the development of dolphin-watching activities in the Gulf in recent years, by operators who have not been applying consistently any guidelines to conduct respectful their whale-watching operations, is cause of strong concern.
The local small-scale fishery, which comprise roughly 280 professional boats, may suffer from ongoing illegal small-scale trawl-like fishery. This activity has an impact not only on the ecosystem, but also in the local economy. Direct impact of this illegal activities on sharks and rays population inhabiting Amvrakikos water has not been assessed, since no surveys aboard of these fishing vessels are possible. Despite this, being all the species benthic (i.e., living in the seabed), and being this illegal fishing gear towed on the bottom, a direct impact and mortality on sharks and rays cannot be ruled out.
The particularly high number of recreational fishers, especially during summer, who directly compete with professionals, is also alarming. Last but not least, the aging of both the vessels and the fishers (as a consequence of new generations not seeing professional fishing as a feasible option for making a living) is concerning for the future of the fisheries sector.
Amvrakikos Gulf is a semi-enclosed embayment consisting of two basins (western and eastern) and belongs to the growing list of “dead zones” around the world. The Gulf is connected to the Ionian Sea by a narrow, shallow sill and is characterized by a fjord-like oceanographic regime, in terms of water circulation pattern. At the entrance of the Gulf over the sill, there is a brackish water outflow in the surface and a saline water inflow close to the seafloor. In the Gulf, the water column shows a well-stratified two-layer structure that appears to control the vertical distribution of the dissolved oxygen in the water column.
This two-layer structure consists of an oxygenated surface layer and a seasonal hypoxic/anoxic bottom layer that are separated by a strong pycnocline. While in the summer the same anoxia/hypoxia pattern occurs in both basins, in the winter the eastern basin appears to remain hypoxic/anoxic. The dysoxic/anoxic interface was found at water depth ranging from 25 to 35 m. Underneath the anoxic waters, a black silt layer and a white mat cover the seafloor. These dysoxic/anoxic conditions appear to have been developed the last 20 to 30 years and are linked to the excessive use of fertilizers, intensive fish farming and domestic effluents. It is estimated that an area of 217.5 km2 (50%) of the total 411.4km2 of the seafloor of the Gulf is under hypoxia and 2.9 ×109m3 (28.5%) of the total 7.4×109 m3 of the water mass are seasonal hypoxic.
In the Gulf of Amvrakikos fisheries are in intense competition with other activities for the use of available space, which is continuously shrinking and being under significant pressure both from the degradation of the marine environment and from interventions and activities on the land. Anoxic/hypoxic conditions spreading in a large area of the Gulf, cause fishers to concentrate heavily on some of the last remaining available fishing grounds, which leads to an increase of competition and pressure on local fish stocks. This is especially the case in the area around the channels connecting the Gulf with the open Ionian Sea.
Unfortunately, the water quality of the Amvrakikos Gulf is declining rapidly. As the final receptor of freshwater and nutrient loads from surrounding areas through runoff and the contribution from rivers Louros and Arachthos, the Gulf’s water is affected by aquiculture, agriculture, livestock and discharges of domestic sewage from coastal towns and villages.
With respect to toxicological status, the organochlorine levels found in bottlenose dolphins were similar to those reported for the same species in the neighbouring waters of the Ionian Sea as far as HCB and PCBs were concerned; however, DDTs levels were four times higher in the Gulf than in neighbouring waters, indicating the existence of a real toxicological problem. Preliminary analysis showed high copper values, which may be driven by the use of copper-based fertilizers. Further analysis increasing the number of dolphin samples and conducting analysis both in soil and water may shed light on this matter.
Trace elements might pose significant risks, particularly to sharks and rays, which as meso- and apex predators, are vulnerable to biomagnification. While heavy metal accumulation, such as mercury and copper, is still lower compared to the legal boundaries issued by the European legislation and other areas in Greece, ongoing monitoring is necessary.
