1. Reducing accidental dolphin catch from turbot fishing using nets4”
Eng. Simion Nikolaev PhD, Eng. Volodya Maximov PhD,
Eng. Eugen Anton PhD, Eng. Kristiyan Danilov PhD candidate,
Eng. Catalin Paun

2. Reducing accidental dolphin catch from turbot fishing using nets
In order to achieve a reduction in accidental dolphin catch during turbot fishing using nets woven from synthetic materials of the polyamide type (PA 6.6), we experimented with testing other options using nets from synthetic materials which are lighter, cheaper and made of impermeable thread with a fibre diameter smaller than the one of PA 6.6 nets, so that the thread can be more easily torn when a caught dolphin exercises its strength.
Therefore, the experiments involved in addition to the PA 6.6 nets single-fibre nets (monofilament) woven from synthetic nylon-type materials meeting to a large extent the requirements specified above. As an additional argument in favour of this type of alternative nets one may point the fact that globally the most commonly used type of nets are monofilament nets made of nylon thread as they are lighter, impermeable, cheaper and more efficient in terms of catch selectivity in fishing.
Research activities at sea were conducted on the Flamingo 4 trawler, property of the company S.C Miadmar Fishing SRL, under a Cooperation agreement signed with INCDM (National Institute for Marine Research and Development) Constanta.
A total of 4 sea expeditions were conducted with the aim to ensure selective catch and to provide a comparative analysis of the two types of fishing nets in terms of turbot fishing, as well as to register the number of accidentally caught dolphins.
Translator's note: The Romanian text includes two mentions of the term 'impermeabile' (impermeable) referring to the fishing nets. In the Bulgarian text the term has been translated as 'nets with impermeable thread'.

3. For the purpose of conducting experiments with both net types, the INCDM Institute secured 30 single-fibre nets for turbot fishing made of nylon, respectively 18 turbot nets with PA 6.6 fibres, where both types had a mesh diameter of 400 mm and fibre diameter of 0.35 – 0.5 mm, pursuant to the national legislation and the applicable GFCM Rules of Procedure (General Fisheries Commission for the Mediterranean), as well as all accessories for said nets (polypropylene nets, anchors, signalling lighthouses, different markings).

4. CONCLUSIONS
After the observations conducted at sea by the specialists from the INCDM Institute, it was concluded that single-fibre nets from nylon are more selective than the ones made from PA 6.6.
The experiments have shown that for nylon nets there was not any registered turbot catch below the minimal requirement of 45 cm, whereas in PA 6.6 nets on each occasion there were trapped specimens with dimensions below 45 cm.
Further more, in terms of the total quantity of caught turbot, nylon nets turned out to be 3% more productive than PA 6.6 ones.

5. CONCLUSIONS
From the point of view of the impact on dolphin populations at sea, it is a fact that during the experiment there was not a single case of incidental dolphin catch in single-fibre nets when compared to PA 6.6 nets where 3 porpoise specimens of the Phocoena phocoena species were trapped. It should be noted, however, that in the nylon nets there were torn links which could be due either to accidental friction of the net against the hull of the ship at the time when it was pulled or to a breakthrough of an accidentally caught dolphin which has torn the mesh and disappeared using its own strength .

6. RECOMMENDATIONS
Both from a structural point of view (mesh size, type of material being used, low specific weight, impermeable fibre, elasticity, thin fibre and lower resistance to tear) and from the point of view of its larger turbot fishing capacity and respectively of the advantage that it does not trap accidentally caught dolphins, it can be concluded after the experiments conducted on board the Flamingo 4 ship that single-fibre nylon nets with mesh dimensions of 200 mm and a fibre diameter of 0.35 mm do not trap accidentally caught dolphins, unlike PA 6.6 nets which have also turned out to be less selective and with lower turbot fishing capacity and which respectively trap accidentally caught dolphins (which do not manage to tear the links of the net and remain entangled and die of suffocation).
Nevertheless, in order to obtain more conclusive results, we recommend the experiments with single-fibre nylon nets to be conducted on board fishing boats where working conditions are significantly different from those on board a ship.
I, the undersigned Petar Galabov hereby certify that my translation from Bulgarian into English of this text from a presentation on specialised scientific experiments conducted in the field of turbot fishing distributed into 6 slides is true and correct.
Signature: Galabov