4. Discussion
The scale of the ghost fishing problem is difficult to assess given
the uncertainties regarding the amount and the circumstances of
gear loss and the effect of environmental conditions on the deterioration of fishing gears in sea beds upon their loss. Rates of
permanent net loss in European waters are typically below 1% of
the nets deployed, which seems to be related to the costs of losing
the gear and to the use of GPS to aid self recovery of nets (Brown
and Macfadyen, 2007). Compared to other regions, the extent of
lost fishing nets in the Southern Portuguese coast is low: less than
1800 nets per year (Santos et al., 2003). In the Portuguese central
coast, the number of nets lost seems to be also low, since fishermen say they have a high rate of success in retrieving their lost
nets. Although trammel net ghost fishing does not seem to be an
important source of resources mortality given this information, the
number of individuals caught in each 100 m of net estimated in
the present study (541 in the nets set in the rocky bottom and
257 in the nets set in the sandy bottom) point to the need to
consider some countermeasures to minimise the effects of such
losses