rete a strascico singola
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La rete a strascico singola viene usata in Scozia per il pesce bianco e per gli scampi.
I pescherecci per lo strascico di fondo sono dotati di arconi o bighi da carico per manovrare i divergenti. I sistemi per salpare la rete variano in funzione delle dimensioni dell’imbarcazione e del tipo di sciabica utilizzata. La maggior parte delle imbarcazioni che praticano lo strascico in Scozia sono da traino poppiero e le loro dimensioni spaziano dal piccolo peschereccio aperto alle più grandi navi da traino con scivoli di poppa.
Le reti a strascico sono progettate per entrare in contatto con il fondale durante le operazioni e, a seconda del tipo di substrato, possono essere corredate di ralinghe e dispositivi di protezione del tipo rock-hopper. Questi ultimi proteggono il lato inferiore della sciabica perché non si danneggi, rimanendo al contempo in contatto con il fondale e facilitando il movimento della rete. Più il substrato è duro e roccioso, più grandi devono essere i dispositivi per garantire la protezione necessaria.
- Click to view environmental impacts of Demersal single trawl
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Potential Impacts (Biological/Environmental) Gear Selectivity Regulation Biological
• Removal of and damage to sedentary marine organisms such as seaweed/corals
• Capture and removal of small sized marine organisms and non-target species
• Capture/discarding of undersized target species
Environmental
• Damage to seabed strata
• Disturbance of bottom sediments
• Mesh size
• Use of square mesh panels
• Trawl door design
• Control of headline height
• Design/construction of footrope materials
• Minimum mesh size
• Minimum fish sizes
• Inclusion of square mesh panels
• Maximum twine thickness
• Net attachments must meet specific regulation conditions to prevent obstruction to net meshes, eg use of bag strengtheners
• Maximum number of meshes in bag circumference
• % of catch mix retained on board
Improvement measures and initiatives taken by Scottish Fishermen
• Progressive increases to mesh size has reduced undersized capture and discards. Cod end mesh size has increased to 120mm for basic towed gear. This has increased the age of capture of most demersal species of fish.
• Introduction through regulation of compulsory square mesh panels (SMPs) has greatly improved selectivity. Further research into different mesh size SMPs and alternative positions in net configuration were carried out in 2006 with Scottish industry and are ongoing.
• Towed gear SMPs have a minimum dimension of 80mm or 90mm depending on trawl type. Many Scots fishermen now operate voluntarily with SMPs of up to 120mm, which increases the escape capacity of the panel.
• Twine materials have improved, allowing net manufacturers to construct trawls from thinner twine, which in turn makes them lighter and gives less drag under tow, hence interaction and damage to the seabed is reduced.
• Many vessels now use footropes equipped with larger diameter discs, which raise the footrope from the seabed. This reduces seabed damage and can acts as a selectivity aid to allow bottom-dwelling fish species to avoid capture.
