An assessment of mortality in fish escaping from trawl cod ends and its use in fisheries management (SURVIVAL) (4305)

  • Madsen, Niels (Project Manager)

Project Details


The survival of fish escaping from towed fishing gears is essential if selective devices are to be used as a practical conservation tool. Several studies have attempted to test this principle and assess the mortality of escaping fish. Unfortunately, these early endeavours have been shown to be fundamentally flawed in methodology so there are currently no reliable estimates of escape mortality. This project developed methods for accurate assessment of escape mortality. The work covered development of techniques to sample fish escaping from a trawl cod end, without introducing biases into the mortality estimates. These techniques were then applied in the field to estimate mortality in cod and haddock under various circumstances including escape at depth and surface, in high intensity fisheries and at different times of the year.

The objectives of the project were:
- to develop sampling techniques that overcome current biases in escape mortality estimation
- to test these techniques directly against previous protocols in order to establish the validity of the new methods.
- to develop a methodology to compare the cod end selectivity, and survival, of gadoid fish escaping at the surface in a side-trawler fishery with that of fish escaping at depth.
- to estimate the number of repeated encounters with trawls on intensively fished grounds.
- to study the effect of repeated gear encounters on escape mortality.
- to determine if gadoid escape mortality varies throughout the year and identify its cause.
- to report the project work and results to the fishing industry, the public and the European Commission.

The contribution of DTU Aqua centered around:
- testing the validation of the new cover design against previous designs.
- investigating the seasonal variation in escape mortality of gadoids trough surface selectivity.
- investigating the seasonal variation in total escape mortality.

The project was coordinated by Institute of Marine Research, Norway.

Research area: Fisheries Technology
Effective start/end date01/01/200231/12/2006


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