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Environmental Issues By Alan J Hartley |
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Invasive Fish And Pond Plants |
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The movement and importation of
the Wels Catfish is banned in this country and it is illegal to release
them into open Waterways such as canals and rivers. They simply grow too
big, have no real natural predators and will eat any wildlife that they
can get into their prodigious mouths. Having said that there used to be
quite a market for some of the slightly smaller species of catfish that
would only grow up to some 5 or 6 feet! When I ran an aquatics
department many years ago I must have sold Grass Carp have also been
banned, in the past, from being imported into this country and being
released into the wild, although when available for sale in the aquatic
trade, they too are popular. They will in theory eat the
“Blanketweed” that plagues many pond keepers, but they are not to be
recommended as in a well planted pond they will strip it bare of all
vegetation in an urge to satiate their massive growth rate and ravenous
hunger. In America grass carp are widely grown as a food fish in the
same way we grow trout. Farmers who rear them actually mow grass from
the fields and scatter the grass cuttings on the water to feed them,
although they will take commercial fish food as well. Because Grass Carp
are prodigious feeders they have been used experimentally in the
Everglades to clear the vegetation that threatens to block the water
ways. In many states of America however they are considered a pest
stripping rivers of all their vegetation and so they have been banned. Other aquatic animals can cause
dramatic problems beside fish. We are all familiar with the wildlife
disaster caused by the importation and subsequent Every year 1000s of them are sold in the aquatic trade to the public and they quickly develop into giant bull frogs. Growing nearly one foot long, they have no real natural predators when mature, because they are simply too big for birds like Herons to eat. Foxes may take a few, but they are the only animal that we have in the UK which is really capable of killing them. As such they are starting to breed without restraint and stripping parts of the countryside bare of smaller wildlife including frogs, newts and even small birds that stray to near to their cavernous mouths. Imported
plants that are released into the wild can also cause severe problems. When people think of imported
plants that have caused ecological troubles they immediately think of
the Giant Hogweed and little else. The Hogweed was imported in Victorian times by
However, there are many other
plants that are now being acknowledged as being a potential threat to
native species and wildlife. Some are very unassuming in their
appearance and on first examination seem completely innocuous. You might
imagine that one category of plants that could not possibly pose a
threat are water plants, because by their very nature they are trapped
in the water source they need to survive. I don’t know that
“Duckweed” or “Fairy Moss” are actually on the banned list, but
most gardening experts now advise against putting them in your garden
pond. You might think that they are restricted to your pond, immobile, and
can’t escape into natural water-courses, but nothing could be further
from the truth. Any type of bird, or indeed any wildlife at all
including frogs, Other pond plants that people are advised not to add to their ponds include some of the rapidly growing “Oxygenating” plants such as Canadian Pond weed. Admittedly, they do not spread as easily, but they can “Escape” and occasionally do so. Some, slow moving natural water courses and many static ones regularly get choked with these plants and have to be routinely “Raked” to clear them. |
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people don’t think that fish are
really animals and can’t cause problems or spread as they are forced to live in
water. Many are released into the wild simply because they have grown too big for
their tank/pond and the owner does not know what to do with them. This
is almost certainly the case with Catfish.
thousands over the years and
I often wonder how many are swimming round our rivers and canals, dumped,
after out growing their tanks
escape/release of the
American Signal Crayfish, but most people do not know of the developing
problems caused by Bull Frog tadpoles in the South of England.
gardeners as a
decorative garden herbaceous plant and conditions were ideal for it with no
natural predators, so it spread rampantly with nothing to restrict its
spread. The Giant Hogweed is spreading along and choking, many waterway
banks throughout the country. What makes this plant even worse is that
its juices are poisonous so great care has to be taken when cutting it
down. The Hogweed spreads by underground shoots that go very deep making
it even more difficult to eradicate or control.
hedgehogs, or even foxes, are quite capable of getting
one or two tiny pieces of the plants on their bodies when they have a
drink from your pond. The specks of plant can survive out of water for
many hours on a cool day until the animal takes another drink elsewhere
in a different pool. It only takes one single speck, a couple of
millimeters across, of this type of plant, to start a new colony of
plants with its rapid division.