flip-up rope study plaice

A study on the use of the flip-up rope in beam trawling for plaice shows that it has no effect in reducing immediate or delayed mortalities of the fish

A new paper has been published examining if injuries and mortalities among discarded European plaice are reduced by European Union legislation for owners of > 221-kW double-rigged beam trawlers to use a ‘flip-up’ rope that limits large stones (>25 cm in diameter) and unwanted debris from entering trawls.

The study entitled “Effects of catch composition on the fate of European plaice (Pleuronectes platessa) discarded from Belgian beam trawlers” was carried out by Sven Sebastian Uhlmann, Bart Ampe, Joanna Marie Goley, Esther Savina and Matt K Broadhurst.

Scientific monitoring of beam-trawled plaice demonstrated that longer stress-exposure times during trawling increased the likelihood fish suffered injuries—rather than the abundance and/or type of sediment (i.e. sand, stones or both) inside the catch, this lead researchers to desire a more detailed analyses of catch compositions are required to establish whether the type and properties of items could exacerbate negative impacts among plaice in codends.

Research into the issue was carried out over eight commercial fishing trips comprising of 197 beam-trawl deployments onboard five Belgian vessels during 2019 and 2020, two scientific observers assessed the reflex responsiveness, injuries and immediate mortalities of 3191 European plaice from 244 sampled codends. 268 specimens were tagged, transferred and monitored for at least 21 days in captivity in order to study delayed mortalities.

The scientists found immediate on-board mortality was positively associated with physical injury, the total weights of catches and stones, and the proportion of injury-inducing elements among the unwanted catch. Delayed mortality was positively associated with injuries and impaired reflexes and elevated seawater temperature.

A detailed, simultaneous catch comparison was done in December 2020 with one of the double-rigged beam trawls equipped with a flip-up rope and the other without. The odds of immediate and delayed mortalities were similar with or without the flip-up rope the two trips assessing immediate mortality.

The study found that reducing catch weights and eliminating stones should reduce the injury and mortality of discarded plaice, but the performance of the legislated flip-up rope needs to be improved.

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