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SURVIVAL
Survival: An assessment of mortality in fish escaping from trawl cod-ends and its use in fisheries management

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 recently been shown to be fundamentally flawed in methodology so there are currently no reliable estimates of escape mortality. This project will develop methods for accurate assessment of escape mortality. The work will start with the development of the techniques to sample fish escaping from a trawl cod-end, without introducing biases into the mortality estimates. These techniques will then be 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. Methods will be developed to include escape mortality data in stock assessment models and they will be implemented.

Objectives
The objectives of the project are:
1) to develop sampling techniques that overcome current biases in escape mortality estimation
2) to test these techniques directly against previous protocols in order to establish the validity of the new methods
3) 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
4) to estimate the number of repeated encounters with trawls on intensively fished grounds
5) to study the effect of repeated gear encounters on escape mortality
6) to determine if gadoid escape mortality varies throughout the year and identify its cause
7) to develop models for including escape mortality data in stock assessments and predictive modelling
8) to determine the sensitivity of these stock assessment and predictive modelling techniques to escape mortality data and the impact on the fisheries management process
9) to report the project work and results to the fishing industry, the public and the European commission.

Progress to Date
A review of available literature and unpublished research in this field has been done to make an in-depth evaluation of the techniques used in the estimation of escape mortality in towed fishing gears. The most suitable sites for field work have been identified, protocols are in progress, the vessel charter specifications have been identified and a suitable vessel chosen. The site logistics have been completed.

Classified in FISHERIES AND AQUACULTURE

Scientist responsible for the project

Head of Division AUD SOLDAL
C. Sundtsgt. 64 Box 1870 Nordnes
5817 BERGEN CEDEX N
Norway - NO

Phone: +47 55238500
Fax: +47 55238687
E-mail: aud.soldal@imr.no

References

Project ID QLRT-2001-01603
Organisation INSTITUTE OF MARINE RESEARCH
Area 5.1.2
Start date 01 October 2002
Duration (months) 36
Total cost 3 470 296 €
Total EC contribution   1 380 000 €
Status Ongoing

The partners

  • THE SCOTTISH MINISTERS ACTING THROUGH FISHERIES RESEARCHSERVICES, MARINE LABORATORY, United Kingdom (The) - GB
    r.stagg@marlab.ac.uk
  • DANISH INSTITUTE FOR FISHERIES RESEARCH, Denmark - DK
    nm@dfu.min.dk
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