Research to understand the impact of discards in sea trammel fisheries and evaluate the effectiveness of possible solutions.

MINOUW partner & Lead scientist:

CSIC (Agencia Estatal Consejo Superior de Investigaciones Científicas) , Montserrat Demestre

Fishing method and species:

Trammel nets with 40-mm square mesh inner panel. Trammel nets are made of 30 pieces of net 50 m long and 1.2 m tall. The species targeted are Cuttlefish, sole, caramote prawn, purple-dye murex, and Golden seabream.

What is the discards problem?

Trammel nets have a good selection patterns for most species. However, unwanted by-catch is produced when nets are set for long fishing operations (8-10 hours) and crabs or other invertebrates prey on the entangled catch, rendering it valueless.

What activities did the MINOUW project carry out?
  • Monitoring fish discarding practices.
  • Estimating handling and sorting costs.
  • Modifying the trammel net design to include a 20-30 cm lower net of coarser material (“selvedge”) to reduce unwanted catches.
  • Estimating the effectiveness of discards-reduction measures based on light technologies.
What outcomes were expected?
  • To understand what factors lead to discarding practices, and how new technologies (for example modifications to nets, use of lights) can mitigate the problem of discards in trammel net fisheries.
  • To foster fishers involvement in the process of finding solutions to mitigate the impact of the Landings Obligation in their activity.
  • To encourage fishing practices and technologies that minimize the impact of fishing on marine ecosystems.


The use of artificial lights on the floatrope of trammelnets did not change significantly the amount of discards for the majority of species while inducing an increase in the catches of the target species (cuttlefish).

For a full summary of results download the PDF here: (610kb)


The guarding net on the footrope of trammel nets is easy to adopt and can be wholly recommended for small scale trammel net fisheries. Its production and fitting is simple.

For a full summary of results download the PDF here: (630kb)