When fish are farmed, it is often necessary for measures to be to taken to protect the fish from predators
because mortality can be high (Carss 1993), and they
show strong emergency adrenal responses and also
suppression of feeding when predators are present
(Metcalfe et al. 1987). Many of the predators are species that the general public hold in high regard, for
example seals, otters, herons, kingfishers or gannets.
Hence, it is necessary for there to be anti-predator
measures that minimise poor welfare of the predators
and do not endanger predator populations. The killing
of predators should be a last resort.