Industrial double rig trawl fisheries in the southeastern and southern Brazil: characterization of the fleet, nets and trawl simulation

The industrial double rig trawl fisheries are an important extractive activity in the southeastern and southern Brazil where near 300 vessels participate, targeting their catch to the sea-bob shrimp, pink shrimp and demersal fishes, such as flatfishes and monkfish. In order to advance in the fishery management, a general characterization of the trawl fleet operating in the area was done, identifying the patterns of nets used and the hydrodynamic performance of the nets observed by means of dynamic simulation. 194 vessels of Santa Catarina State and 130 vessels from other areas, mainly built in steel and wood, were identified. The largest size, tonnage, and capacity, correspond to those vessels working upon demersal and oceanic fishes. On the other hand, the most abundant vessels were those working upon pink shrimp (230 vessels). Regarding the nets, different patterns were identified according to the catch of target species; the smaller nets were used to catch shrimps (sea-bob and pink shrimp) and the largest were used to catch fishes. Mixed nets were also identified, characterized by similar dimensions of nets to catch fish but with mesh sizes of shrimp nets. From the simulations, different performance functions were adjusted according to each founded pattern; these functions will serve to calculate net's spread, their shape relationship, and the hydrodynamic drag forces.