Monteiro, P. Study of the environmental impact of demersal gill nets and trammel nets lost at sea (ghost fishing).

When a fishing device is lost or abandoned at sea, it can become a non controllable capture instrument leading to the resources' mortality, impoverishing them at an ecological and economical level. The objective of this work was to study the impact of lost stationary nets (gill nets and trammel nets) through simulated experiments in two fishing areas of rocky bottom, off the Algarve coast, near Faro, between 17 and 20 meters deep. Three trials were carried out with both a gillnet and a trammel net. The net physical evolution and catch data were followed by scuba diving.

The analysis of the results confirms the general idea that lost or abandoned gillnets are still capturing in decreasing levels, following a logarithmic pattern. We can also conclude that under these conditions, i.e., in natural reefs with the trial location characteristics, a "ghost net" has a fishing lifetime inferior to a year. Nevertheless, the nets capture in the first twenty weeks (four to five months) more than 95% of the total capture.