Predation and Angling

[cg74]

Some "facts" about signals
They can spread at a river rate of 1.2 km per year , or faster via damp nets
They carry a parasite that affects native crayfish which affects their muscles making them 30 % slower and therefore less able to compete for food
Their predators in the UK are otters , eels and salmon , though where they cohabit with Salmon par they seem to have a negative effect on the Salmon.

So maybe otters are the answer to our crayfish problem ? If only it were as simple as that , remember rabbits overrunning Australia ?

Its my belief that Apex predators have inbuilt behavior patterns to prevent them overrunning their prey mainly by being territorial whereas prey species usually are subject to other factors and are in balance with the eco systems they have evolved into , not perfectly otherwise we would never get any change , but almost perfectly.

"So maybe otters are the answer to our crayfish problem ?"
This springs to mind:
There Was An Old Lady - YouTube

---------- Post added at 12:46 ---------- Previous post was at 12:41 ----------

By the authors arguments the plains of Africa would be wall to wall lions but then again the author drops the bomb and legs it - tantamount to trolling.

Whilst I agree with your thoughts on the author, it is worth remembering the African plains are a very managed environment.

 

[chub_on_the_block]

My understanding is that signals carry "crayfish plague" a fungal pathogen Aphanomyces. They are not affected themselves but serve as a vector for transmitting it to native populations, where it generally causes total mortality in a short time. When the plague outbreaks first started in the 1980s and early 1990s MAFF scientists would conduct tests on dead specimens and confirm whether the outbreak was caused by this pathogen. There were a few rivers where signals and natives appeared to coexist for a few years, eg the River Thame, but to my knowledge that didnt last beyond the mid 1990s..