engleski

Ghost-net fishing along the Croatian coastline ; occurrence and biological impact on marine biodiversity, a preliminary assesment

Derelict fishing gear (DFG) or “ghost-nets” is any discarded, lost or abandoned, fishing gear in the marine environment. This gear continues to fish and trap animals, entangle and potentially kill marine life, smother habitat and act as a hazard to navigation. DFG, such as nets or traps and pots is one of the main types of debris impacting the marine environment today. Hundreds of marine species have been reported to be affected by DFG entanglement and ingestion that has been identified as a major cause of morbidity and mortality in some populations [1]. To date, there is no informations about the type, amount or sources of DFG in the Croatian waters and their direct impact on the marine biodiversity remains completely unknown. The objectives of this study were to use data collected during two types of activities ; survey dives throughout various scientific research in last decade and the targeted recovery of „ghost-nets“ during DeFishGear project in 2014/2015, all performed in the wider area of the middle Adriatic. In this study, we presented for the first time data on the occurence and the entanglement observed in DFG for Croatian waters. Ghost fishing has been confirmed for gillnets, trammel-nets, trawl-nets, traps and small purse seine nets. More than 50 DFG have been observed during diving activities and about 700 kg collected during the DeFishGear project. Of this number, 40% were documented to have been derelict for at least one year, but many were much older and still pose a threat to marine organisms. Most derelict gillnets found were from the high-relief rocky reefs and boulder habitats relatively small in size (≤100 m2 in area), of relatively recent construction and in good condition, recovered from depths above 30 m. Fisheries that deploy unattended gear like gillnets or trammel-nets were the primary source of DFG. Survey results indicate that majority of DFG was on underwater rocky reefs (74%) while the remained was on sand/boulder seafloor habitat (24%) or stranded on shorelines (2%). Most DFG was the result of inclement weather ; however, poor fishing practices and lack of convenient gear disposal infrastructure contribute to gear abandonment and at-sea discard. Of the marine organisms found entangled predominantly from gillnets, 35 were invertebrates representing at least 7 species, and 17 fish from 9 species, most of which were recovered dead. Marine organisms occurred in 5% of observed gillnets. Mortality from DFG should be recognized as an additional risk for several crustacean and fish species of conservation concern like Palinurus elephas and Scorpaena scrofa, respectively.

Ghost-net fishing; Croatian coast; impact; biodiversity

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