DOLPHIN deaths from fishing nets appear to have halved in the past few years, but researchers believe some kills are literally slipping through the net.
A study by Murdoch University researchers found the number of dolphins killed as by-catch in WA had dropped from 100 to 20 a year.
But the university's cetacean researcher Simon Allen said the figures could be wrong because by-catch reduction devices fitted to nets may be allowing dolphin carcasses to fall back into the water.
“Current BRDs have bottom-opening escape hatches only and, in some cases, dead dolphins fell through them before the nets were hauled up and were therefore not recorded,” Mr Allen said.
Only those dolphins landed on deck were recorded, meaning dolphin by-catch figures could be far higher.
"Our research showed that air breathing animals, like dolphins, swim upwards when under stress. Trials of nets with top-opening escape hatches for air-breathing animals are vital."