Monitoring of fisheries and dolphin-fisheries interaction

Interactions between cetaceans and fisheries in the Mediterranean Sea are probably as old as the first human attempts to catch fish with a net. In most cases this “operational competitive interaction” with set nets results in net damage, reduction in the value of the catch due to mutilation or removal of fish from nets, and decreased total amount of fish caught. It is unclear why this issue appears to be increasingly perceived by Mediterranean fishermen to be causing economic hardship, particularly as far as small-scale, coastal fisheries are concerned. One of the reasons may be that small-scale fisheries in many parts of the Mediterranean have become economically marginal, whether due to the depletion of fish stocks (overfishing), over-capitalisation, market changes or socio-cultural factors.

Research conducted by Tethys in the Ionian Sea over the past decade has focused on dolphin-fisheries interactions  and in the evaluation of the fisheries’ impact on the dolphin populations and on the ecosystem. The methodologies used included dolphin surveys at sea, interviews to small-scale fishermen (Gulf of Taranto, Italy, and Inner Ionian Sea and Gulf of Ambracia, Greece) and direct monitoring of fisheries through censuses of the active fishing fleet and a quantitative and qualitative observation of their captures (Inner Ionian Sea) (Bearzi et al. 2006).

Fisheries monitoring in the Inner Ionian Sea Archipelago (Greece) over a 12 month period in 2007 suggested that ecological interactions between dolphins and fisheries in this coastal area have minor effects on fisheries. Conversely, prey depletion resulting from overfishing can have a significantly negative effect on dolphins as indicated by the sharp decline on the local population of common dolphins observed.

A study in the Porto Cesareo MPA (Gulf of Taranto, Italy) in 2008, showed that information from interviews and boat surveys was contradictory, suggesting that reports of acute depredation do not imply a constant presence of dolphins within the MPA. Interviews made during this study could have been perceived by some fishermen as an opportunity to influence future decision-making regarding monetary compensation for the impact of depredation. Evidence from interviews also indicated that species and factors other than dolphins were responsible for part of the damage.

Interviews of small-scale professional fishermen in Greece in 2011 showed the lack of confidence of younger generations in the future of fisheries, and that the traditionally-oriented fishing community is rapidly changing. Fish captures have reportedly decreased dramatically during the last 20 years. Net damage as a consequence of dolphin predation was almost unanimously reported; however, dolphins were not the only animals held responsible for net damage, nor those reportedly causing the largest economic loss to small-scale fisheries, which was attributed to either sea turtles or the critically endangered monk seal, depending on the area. The fishermen of the Gulf of Ambracia advocated the introduction of measures to curtail habitat degradation as the top priority, while their colleagues of the Inner Ionian Sea Archipelago identified fisheries management measures and effective law enforcement as the most urgently needed actions (Gonzalvo et al. 2014).

In addition to the above-mentioned studies Tethys personnel has also conducted similar interviews to small-scale fishermen in Libya (Bearzi 2006), Syria  (Gonzalvo 2008) and Lebanon (Gonzalvo 2009) in 2006, 2008 and 2009, respectively, in the context of the development of National Action Plans for the Conservation of Cetaceans in these countries in collaboration with UNEP’s Agreement on the Conservation of Cetaceans in the Black Sea, Mediterranean Sea and contiguous Atlantic area (ACCOBAMS) and Regional Activity Centre for Specially Protected Areas (RAC/SPA).