Scientists say catch and release fishing may have significant damaging effects on sharks.

A new study could have implications for anglers who like to pose for photos before releasing big catches.

Footage from underwater drones has shown that sharks captured and exposed to a boat deck for 15 minutes swam for a maximum of 30 seconds after release, before beco An Aussie eucalypt can ‘remember’ past exposure to extreme heat, which makes the tree and its offspring better able to cope with future heatwavesming largely immobile for five minutes.

A possible explanation for the lengthy period of immobility is that deck-exposed sharks use the remaining oxygen contained in their blood to try to escape the stress event, leaving their tissues starved of oxygen or ‘hypoxic’.

The short burst of rapid swimming immediately after release could be an attempt to reverse these hypoxic conditions, an escape reaction to high stress environments or the result of thermal shock when the shark re-enters the water.

University of Newcastle marine ecologist Dr Vincent Raoult says the underwater drones have provided a new window into the behaviour of a shark after release.

“Anglers needed to consider the exposure of sharks. Measuring and weighing sharks or posing for social media photos prolongs their exposure and is detrimental to the animal and potentially fatal in the long run,” Dr Raoult said.

“People should enjoy their sport fishing but should try to limit how long they handle sharks to minimise injury to the animal. Best practice is to release them immediately.”

Dr Raoult said bycatch of sharks formed a substantial component of both commercial and recreational fishing.

“Improved bycatch handling practices would reduce negative effects to sharks and help stop the decline in their numbers.”

Researchers relied on shark ‘tail beats’ to undertake the study.

Like a human heart beat, a shark’s tail beat is easily measured and provides useful health insights.

For instance, a shark’s tail beat frequency is linked to their metabolic rates – the rates at which their bodies use oxygen and chemicals to undertake processes necessary for survival.

“Footage from the deck-exposed sharks showed they had low tail beat frequencies, were in distress and usually had rapid, strained breathing,” Dr Raoult said.

The study showed that sharks that were handled but immediately released displayed rapid recovery.

“This indicates that even sharks previously exposed to high capture stress, such as trawling, can rapidly recover if exposure times are limited,” Dr Raoult said.

The study is accessible here.