By definition, though,this phenomenon is hard to evaluate accurately: since the fish arenot landed it cannot be known with certainty what volumes areactually thrown back into the sea.
Is deacair an feiniméanseo a mheas go grinn, áfach, mar gheall ar an gcaoi a ndéantar é:ó tharla nach gcoinnítear na héisc ar bord ní féidir bheith cinntefaoin gcainníocht a chaitear ar ais san fharraige, le fírinne.