Hopefully
spring will be now upon us, with scents of bluebells, catkins on willows and
new leaves unfolding on the trees. You
may take a spring walk along the River Ock, but beware of the alien species
that lies beneath. Anglers will be well
aware of this alien infestation, but for the ordinary people we will only
notice them when looking over a bridge hoping to catch a glimpse offish. What am I talking about? A crustacean: the American Signal
Crayfish. It is bigger than our native
white clawed crayfish, which it out-competes for food and habitat. They carry a disease which kills our smaller
native species and their burrows damage the sides of the river. Apparently they were brought into the country
by the Ministry of Agriculture Fisheries and Food (MAFF) to boost commercial
fisheries and may have escaped or been released.
What can we do?
Not a lot is the answer. The
Environment Agency says: “Signal crayfish
have been present around Oxford for over 25 years. We don’t have clear evidence that local
trapping of signal crayfish is beneficial to stocks of the native species. We issue authorisations for trapping of
signal crayfish in the Thames for commercial and domestic consumption, and in
some cases, intensive trapping, to reduce the nuisance impact on anglers.” You have to be licenced by the E.A. to catch
them and putting them back is forbidden (failure to comply carries a hefty
fine) but they do make for good eating!
Remember the Hairy Bikers came and visited Abingdon Lock in 2013 to
sample the fayre, helped by a local man ‘Crayfish Bob’. Maybe our local restaurants need to take note
and increase crayfish on the menu; it is local, seasonal and fresh …. and
eco-friendly way of saving the Abingdon Environment.
Signal crayfish is a ferocious cannibal that will eat anything that comes its way, fish eggs, ducklings, young moorhens and has all but finished off our indigenous species. Members of the species are typically six-nine cm (2.4-3.5 in) long, although sizes up to 16-18 (6.3-7.1 in) are possible. It gets its name from the white to pale blue-green patch near the claw hinge, like the white flags that signalmen used for directing trains. They are bluish-brown to reddish-brown in colour with robust, large, smooth claws. About 200-400 eggs are laid after mating in the autumn, and are carried under the female’s tail until they are ready to hatch the following spring. The eggs hatch into juveniles, which pass through three moults before leaving their mother.
Signal crayfish is a ferocious cannibal that will eat anything that comes its way, fish eggs, ducklings, young moorhens and has all but finished off our indigenous species. Members of the species are typically six-nine cm (2.4-3.5 in) long, although sizes up to 16-18 (6.3-7.1 in) are possible. It gets its name from the white to pale blue-green patch near the claw hinge, like the white flags that signalmen used for directing trains. They are bluish-brown to reddish-brown in colour with robust, large, smooth claws. About 200-400 eggs are laid after mating in the autumn, and are carried under the female’s tail until they are ready to hatch the following spring. The eggs hatch into juveniles, which pass through three moults before leaving their mother.
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