Fish response to threats is of two kinds and not much unlike the ways humans handle a scary situation, a Swedish professor says: they fight or hide or flee, or they just lie down and hope the unpleasantness will go away.
Professor Svante Winberg, a professor of fish physiology at Uppsala University, explained in a Swedish Radio interview that fish under stress experience raised blood sugar levels and increased heart rate, sometimes on a level that may be dangerous for them.
Stress is a major problem in fish farming today and Winberg sees many good reasons to focus on a better understanding of the stress responses in fish.
He added that these findings also show how important it is for anglers to throw their catch back into the water as quickly as possible, if they intend to do so. They also demonstrate the basic futility of discarding live fish in professional fisheries.
In the radio interview, professor Winberg went on to emphasise to aquarium owners the need to pick the right species and the right number of fish – not too few and not too many.
“We often study aggression and social dominance hierarchies and see that the subordinate fish gets a lot of beating: it has nowhere to flee, its growth is impaired and it gets sick a lot. In that sense, this is an ethical problem”, he said.
It may be added that a special government agency responsible for ethical animal care in Sweden was dissolved in 2007, after a line of much-publicized declarations, including one that baiting hooks with live roach was to fall under the cruelty to animals paragraphs in the criminal law.