There is unexplained variance in selectivity data. It is necessary to determine how much of this variance is due to variables which can be controlled and possibly used to improve selectivity by legislation and how much is due to variables outside human control or due to random effects.
Four aspects of whitefish trawl selectivity will be studied during this project. The effect of twine diameter on selectivity will be quantified to provide information to legislate against the use of thick twine if necessary. The effect of gear size and towing speed will be studied to determine the extent to which selectivity can be manipulated by increasing vessel horse power. Catch size may be a significant factor in unexplained variance between hauls and between cruises. Finally fish shape is known to change significantly during the year, eg pre- and post-spawning and this effect will be quantified.
Consistent data sets will be collected on all these topics. The information may be used to improve the effectiveness of technical measures, to define more precisely the selectivity characteristics of EC fishing fleetsand to identify the range of uncertainty in these characteristics for a given fishing situation, thus benefitting the management and control of EC whitefish fisheries and leading to more effective exploitation of the stocks.
Funding SchemeCSC - Cost-sharing contracts