The use of fish from intensive fish farms links angling to the widescale slaughter of fish eating predators such as herons, otters, seals and cormorants, done to 'protect' fish stocks. Additionally, as anglers will rarely keep returning to waters where they don't catch fish, owners often overstock their fisheries to ensure high catch rates. Overstocking means that fish are reliant on high quantities of food being introduced by anglers and can have catastrophic consequences in very hot weather or where low level pollution occurs, causing oxygen levels in the water to fall to critical levels. Unfortunately, it is all too easy for more fish to be bought from a hatchery. Huge foreign fish are increasingly being imported to satisfy the specialists.
Fatalities are common.
It is not just fish populations that are manipulated. For many years, fish hatcheries have used special diets and conditions to grow big fish, but things are becoming more advanced. A fish farmer from Hampshire keeps his genetically altered sterile fish in constant summer temperatures, with an inch-long 'hatpin' inserted between the cerebral lobes in their brains to allow their temperature to be monitored by computer. Meanwhile, scientists are involved in research to genetically alter fish by lifting controls on growth hormones thus delaying breeding seasons, allowing them to get fatter earlier. Genetic manipulation of other species such as pigs and cows has produced painful side effects including rheumatism and even less is known about the molecular make-up of fish.