On some fish farms, instead of catching the fish in
the water in the most rapid and least disturbing way,
people are allowed to come to the farm and catch the
fish with a hook and line. Hooking and handling fish
for release increases scale damage, making the fish
more vulnerable to infection (Broadhurst & Barker
2000). Injury and mortality following the hooking of
fish is common, especially where the hook penetrates
deep into the tissues (Muonehke & Childress 1994),
and the mortality increase is clear in live-release tournaments (Suski et al. 2005). The actual process of capture on a hook leads to increased heart rate, cortisol
production, and subsequent avoidance of the situation
(Verheijen & Buwalda 1988, Pottinger 1998, Cooke &
Philipp 2004). Later effects of capture and a period in
air before being returned to water include suppression
of immune system function, suppression of oestradiol levels, reduced reproductive ability, and severe meta-
bolic effects (Pickering & Pottinger 1989, Melotti et al.
1992, Ferguson et al. 1993, Pankhurst & Dedual 1994).
A period in a keep net also leads to adrenal responses:
sometimes prolonged, but sometimes rather brief (Pot-
tinger 1998).