AGA Group - Fisheries Management - Biosecurity

AGA Group - Fisheries Management - Biosecurity - Otter Predation

Protection against Otter predation.

Mammalian predation is an increasing problem on recreational fisheries, especially as the otter becomes more widely dispersed following the reintroduction of captive bred specimens and the fact that the species has been afforded stringent protection. The non-native mink is now established throughout England and Wales. Mammalian predation has not been widely perceived as a serious threat until more recent times. This is partly because these predators remain largely elusive, and, as they are largely nocturnal it is extremely unlikely that one actually witnesses mammals taking fish.

The conflict between fishery managers and predators such as mammals has increased over recent as the otter has recovered from years of decline benefiting from reduced pollution and habitat improvements and provision. In the late 1950’s -1960’s the otter population underwent a dramatic national decline, due mainly to the toxic effect of chemicals associated with agriculture and industry, along with widespread habitat destruction. Otters disappeared from most rivers in Central and Southern England. However since being afforded protection and with few predators in the wild there is now significant evidence of their natural widespread recovery. Figures published by the Environment Agency from 2000-2002 showed that 36% of the rivers which they surveyed showed signs of otter presence, an increase of 527% from 1977-1979.

Otters are elusive, generally nocturnal and seldom seen. They have dark brown dense fur, with a paler belly and a cream patch under the chin. Male otters average 1.2 metres in length from nose to tail and can weigh up to 10 kg whilst female otters tend to be slightly smaller. Otters favour all forms of wetland habitat; from rivers, lakes, streams, ditches and dykes to marshes, reed-beds, estuaries and coastland. Individuals have large home ranges, which may contain up to 30 lying-up places, or holts, in the form of natural hollows in tree roots or amongst dense vegetation.
There is, however, a growing concern amongst anglers and fishery managers that otters are taking fish, particularly large carp from still-water fisheries, where they are stocked at high densities. When some of these fish are worth several thousand pounds apiece, it is not surprising that managers may become hostile to the presence of otters.

Otters, being predators, will take advantage of easy prey, particularly when fish are torpid during the colder months, if they are left unprotected. Otters that predate a stillwater fishery may often kill and injure more fish than they actual require for nutrition, they also in these situations have tendancies to eat a very small amount of a number of fish.

Work has been done to look at ways of protecting fisheries, using fencing and decoy pools for instance. Fencing appears at the moment to be the most effective solution against otter predation, but this is not cheap and can run into thousands of pounds.

Otter Fencing.

Given the limited actions that can be taken to protect a recreational stillwater fishery against otters and the relatively high associated costs; it is important that fences are designed and erected to be fully effective and reliable. Fences can of corse have a number of associated benefits such as keeping out poachers, a variety of other animals and therefore form a bio-security barrier.

A.G.A Group are willing to advise and install such biosecurity measures to help protect your fishery from predation.

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Last Updated on Thursday, 09 September 2010 10:36