Shellfish Resources and Fishing Techniques for Non-Destructive Impact of Stock and First Record of Ruditapes philippinarum in the Danube Delta Biosphere Reserve, Romania

The aim of the study is to evaluate the possible introduction of alternative fishing tools for the Danube Delta Biosphere Reserve (DDBR) and their comparison with other used systems, thus aiming to reduce the pressure on fishery resources in the Danube Delta as well as to exploit alternative resource in coastal waters of DDBR. Fish stocks are generally decreasing because of overexploitation in many regions (including Romania) as well as due to the increasing market demand for shellfish. E.g., Rapana venosa catch increased from 1.7 t/year to 7330 t/year in 2018 in Romanian coastal waters. Other mollusc species can be used as alternative fishing resource: Anadara kagoshimensis, Cerastoderma glaucum, C. edule, Mya arenaria, Chamelea gallina, Mytilus galloprovincialis, Donax trunculus and Ruditapes philippinarum. Six fishing tools were tested for fishing molluscs: Rapana cages, rake with attached basket, mussel rake, manual scraper with harness, hydraulic scraper and boat-operated hydrorasket (hydraulic dredge). All they had an impact on bottom. However, compared with the traditional commercial hydraulic scraper and the beam trawl, this impact is lower and reduced to almost natural storm impact in this part of the Black Sea, which is characterised by strong hydrodynamics making bottom organisms already preadapted to this kind of perturbations. Currently, a rich resource consisting of Anadara kagoshimensis and Rapana venosa exist in the studied area. In addition, Chamelea gallina has a significant abundance and can be exploited in a way harmonising with maintaining the coastal environment. Using chemical parameters, the analysed area was assessed in the Class A (good condition). Both heavy metals and microbiological parameters from mollusc tissues are in the frames of the permissible limits as identified by the Romanian legislation.