[snapper35]

Having got interested in trapping some signals locally I rang the EA today to enquire about the licences etc for my area. Due to there being a population in one part of the river of white claws there is no trapping allowed at present (though there are at least 3 weirs and 20+ miles difference between the two places). Besides, 10 traps is small scale - they would look at using hundreds to do the job with no guarantees of success. Anyway, that's fair enough.

While on the phone I enquired about the reason that small scale trapping could have a negative effect (as alluded to on another thread) and received an answer which is very understandable and so I share it here. Being predatory (and cannibalistic) signals eat each other as well as other river life. Thus trapping, though seeing a reduction in large signals, can have a detrimental effect as the large ones are no longer there to prey on the small, thus the numbers of crays increase, and obviously need to widen there search for food. This is the same effect that removal of pike has on a water - take out the big ones and there is an explosion of jacks until such time as nature evens the balance again by establishing a dominance of large ones.

Regarding biological control, well with myxamatosis it is seen that this can have effects that last far longer and are less controllable than at first thought. There is no way of telling if the virus could, for example, mutate and attack crays or water life which are initially immune, possibly with the signals becoming immune to it.

(These are a mixture of my thoughts and what we chatted about, so don't take them as 'the party line', but as a general conversation). Hope it is of interest and helps.