A Fishing forum. FishingBanter

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Home » FishingBanter forum » uk.rec.fishing newsgroups » UK Coarse Fishing
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

Dangerous Goldfish!



 
 
Thread Tools Display Modes
  #1  
Old December 3rd, 2003, 10:14 AM
I
external usenet poster
 
Posts: n/a
Default Dangerous Goldfish!

Meet the crucian carp - the hard nut of Britain's freshwater fish. The
Carassius carassius, to give it its proper name, is Britain's only native
carp species. It may not grow as quickly or as large as the non-native
common carp, and may not be as prized by specimen-hunting anglers, but it is
much, much tougher. It can survive a vast range of temperatures, from an
almost slow-cooking 38C down to 0C. It has even been known to hibernate in
mud while the water above it has been frozen. It can tolerate highly acidic
water, and it can survive in water where there is virtually no oxygen -
conditions that would be fatal for almost all other freshwater fish in this
country.

But the hardy crucian is under serious threat, and one of the unlikely
villains of the piece is the domestic goldfish. Detective work by genetics
experts has revealed that goldfish released into the wild can breed with
crucian carp to produce hybrid fish, and that these, in turn, can breed
among themselves, or back-cross with pure crucians. Such contamination of
the gene pool could have disastrous consequences for the crucian carp, and
experts are drawing up plans to protect the species.

Philip Bolton, a fisheries officer with the Environment Agency, has been
investigating the threats to the crucian carp. "The first problem is loss of
habitat," he says. "Crucians prefer small ponds - the sort that used to be
found on farms everywhere - but many have silted up or been filled in."

The other main problem is competition from non-native fish species that have
been introduced into waters, usually to improve the fishing. The main
culprit is the common carp, an aggressive, voracious feeder that uproots
plants at the bottom of lakes and ponds, disturbing the silt and making the
water cloudy, which in turn makes it difficult for plants that are part of
the crucian carp's diet, to re-establish themselves.

The crucian is also susceptible to non-native parasites, including a
tapeworm that is thought to have been introduced by another popular
non-native species, the grass carp. "As far as we know, the crucian carp has
no natural tapeworms, so it is ill-equipped to deal with them," says Mr
Bolton. "It impacts on the fish very heavily." Recently, a nematode worm has
also been identified that can infest the crucian, and it is believed to have
come from goldfish.

But perhaps the most insidious threat is from hybridisation - native, pure
crucian carp cross-breeding with non-native species in the wild, creating
aggressive hybrids that might in turn continue to breed and cross-breed and
gradually contaminate the finely tuned set of genes that have made the
crucian carp such a hardy fish.

To discover if this is a genuine threat, scientists need to know for certain
whether crucians can interbreed with other species in the wild - in
particular, with goldfish. It has been suspected for some time that goldfish
do cross-breed with crucians, but not confirmed, and hybrids are difficult
to distinguish purely by visual inspection.

The key fact is that only a relatively small number of goldfish are bright
orange. In a brood of thousands, most will be brown, and will,
superficially, resemble crucian carp. Commercial goldfish breeders often
sell these brown goldfish to fishing clubs to stock their waters. Also,
domestic goldfish are often released into the wild when people no longer
want them as pets.

To discover whether interbreeding does occur, the Environment Agency sought
the help of gene detectives at the Molecular Ecology and Fisheries Genetics
Laboratory at the University of Hull. The scientist who carried out the
investigation was Dr Bernd Hänfling. "The aim of the project was to find a
way to unequivocally differentiate between the three species of carp -
crucian, common and goldfish - and to find out if there has been any
cross-breeding," he says. "We approached this via genetic fingerprinting."

The basis of genetic fingerprinting is to identify a short stretch of
genetic material, DNA, which has a common pattern in each of the species
under investigation, but that differs in its length. These segments of DNA
are termed microsatellite markers. So, for example, a particular marker
might be on average 100 units long in the goldfish; 85 in the common carp;
and 65 in the crucian carp. A pure-bred goldfish would have markers only of
100 units, and a crucian carp only of 65 units. However, if a pure-bred
goldfish successfully crossed with a pure crucian carp, one parent would
contribute a marker 100 units long, and the other a marker of 65 units. In
this case, analysis of the DNA would show both markers present - indicating
a hybrid.

"Isolating these markers is technically extremely challenging," says the
Hull laboratory's Professor Gary Carvalho. "However, Bernd succeeded in
identifying 10 such markers that were common to each of the three species,
and produced a specific signal within each species."

So, when a sample of tissue from a fish was sent to the laboratory, the team
could extract its DNA, identify the markers, and confidently assign a
genetic history to the sample. By using this technique, Dr Hänfling
confirmed that the samples he analysed included hybrids between goldfish and
crucian carp, and hybrids between crucian and common carp. This was clear
evidence that interbreeding does indeed occur, as the fisheries scientists
suspected.

But of more concern was the fact that the genetic analysis showed that a
small number of hybrid individuals had interbred or "back-crossed" with pure
stock. "Of 250 samples I analysed, two were back-crosses," says Dr Hänfling.
"This isn't a lot, but it indicates that it can happen."

The phenomenon of hybrids interbreeding or breeding with pure stock is
called introgression. Professor Carvalho explains why it is an important
issue. "The key is to protect the gene pool of the native species," he says.
"Hybridisation can result in the degradation of the ability of the fish to
survive in its native habitat. Once you start to get introgression, you
start to get contamination of the gene pool, which can be detrimental to the
survival of the species. This has been seen where escaped farmed salmon
breed with wild salmon, resulting in hybridisation and introgression. The
resulting offspring are less fit than their pure-bred cousins to withstand
the rigours of the environment, and have lower resistance to diseases and
have confused migrating behaviour, for example."

For Philip Bolton, the Hull research provides the hard evidence that
scientists need in order to devise appropriate conservation strategies for
the crucian carp. One fear is that the hybrids might become more aggressive
than the pure species, and out-compete them. "I was impressed with the power
of the DNA technology," says Bolton. "This work will give us solid
scientific support for any policies we introduce to protect the native
crucian population, and will help us to produce our updated field guide to
crucian carp, which will in turn help in their identification. The issue of
introgression is interesting - and disturbing. We have anecdotal evidence
that in waters where it is suspected that hybrids exist, there has been a
dwindling of the native population."

Bolton hopes to organise a nationwide audit of pure crucian stocks in the
country so that these populations can be protected from contamination by
goldfish and common carp. "There is no doubt that the crucian-carp
population is under serious threat, and this has been further confirmed by
this study," he says. "As things stand now, it is not likely that the
crucian will be wiped out, but there is an outside potential for that to
happen if we don't act now."

In the meantime, Bolton has advice for anyone who can no longer look after
their pet goldfish. "Releasing fish into the wild is illegal without consent
from the Environment Agency," he says. "Take the goldfish back to the person
who sold it to you, or give it to a neighbour with a pond. If neither of
these are possible, contact your local Environment Agency office for
advice."


  #2  
Old December 3rd, 2003, 11:32 PM
Baal
external usenet poster
 
Posts: n/a
Default Dangerous Goldfish!

Bollox!

--
I smile and go off waving
(Amiably) - for that's my way

Baal

"I" wrote in message
...
Meet the crucian carp - the hard nut of Britain's freshwater fish. The
Carassius carassius, to give it its proper name, is Britain's only native
carp species. It may not grow as quickly or as large as the non-native
common carp, and may not be as prized by specimen-hunting anglers, but it

is
much, much tougher. It can survive a vast range of temperatures, from an
almost slow-cooking 38C down to 0C. It has even been known to hibernate in
mud while the water above it has been frozen. It can tolerate highly

acidic
water, and it can survive in water where there is virtually no oxygen -
conditions that would be fatal for almost all other freshwater fish in

this
country.

But the hardy crucian is under serious threat, and one of the unlikely
villains of the piece is the domestic goldfish. Detective work by genetics
experts has revealed that goldfish released into the wild can breed with
crucian carp to produce hybrid fish, and that these, in turn, can breed
among themselves, or back-cross with pure crucians. Such contamination of
the gene pool could have disastrous consequences for the crucian carp, and
experts are drawing up plans to protect the species.

Philip Bolton, a fisheries officer with the Environment Agency, has been
investigating the threats to the crucian carp. "The first problem is loss

of
habitat," he says. "Crucians prefer small ponds - the sort that used to be
found on farms everywhere - but many have silted up or been filled in."

The other main problem is competition from non-native fish species that

have
been introduced into waters, usually to improve the fishing. The main
culprit is the common carp, an aggressive, voracious feeder that uproots
plants at the bottom of lakes and ponds, disturbing the silt and making

the
water cloudy, which in turn makes it difficult for plants that are part of
the crucian carp's diet, to re-establish themselves.

The crucian is also susceptible to non-native parasites, including a
tapeworm that is thought to have been introduced by another popular
non-native species, the grass carp. "As far as we know, the crucian carp

has
no natural tapeworms, so it is ill-equipped to deal with them," says Mr
Bolton. "It impacts on the fish very heavily." Recently, a nematode worm

has
also been identified that can infest the crucian, and it is believed to

have
come from goldfish.

But perhaps the most insidious threat is from hybridisation - native, pure
crucian carp cross-breeding with non-native species in the wild, creating
aggressive hybrids that might in turn continue to breed and cross-breed

and
gradually contaminate the finely tuned set of genes that have made the
crucian carp such a hardy fish.

To discover if this is a genuine threat, scientists need to know for

certain
whether crucians can interbreed with other species in the wild - in
particular, with goldfish. It has been suspected for some time that

goldfish
do cross-breed with crucians, but not confirmed, and hybrids are difficult
to distinguish purely by visual inspection.

The key fact is that only a relatively small number of goldfish are bright
orange. In a brood of thousands, most will be brown, and will,
superficially, resemble crucian carp. Commercial goldfish breeders often
sell these brown goldfish to fishing clubs to stock their waters. Also,
domestic goldfish are often released into the wild when people no longer
want them as pets.

To discover whether interbreeding does occur, the Environment Agency

sought
the help of gene detectives at the Molecular Ecology and Fisheries

Genetics
Laboratory at the University of Hull. The scientist who carried out the
investigation was Dr Bernd Hänfling. "The aim of the project was to find a


way to unequivocally differentiate between the three species of carp -
crucian, common and goldfish - and to find out if there has been any
cross-breeding," he says. "We approached this via genetic fingerprinting."

The basis of genetic fingerprinting is to identify a short stretch of
genetic material, DNA, which has a common pattern in each of the species
under investigation, but that differs in its length. These segments of DNA
are termed microsatellite markers. So, for example, a particular marker
might be on average 100 units long in the goldfish; 85 in the common carp;
and 65 in the crucian carp. A pure-bred goldfish would have markers only

of
100 units, and a crucian carp only of 65 units. However, if a pure-bred
goldfish successfully crossed with a pure crucian carp, one parent would
contribute a marker 100 units long, and the other a marker of 65 units. In
this case, analysis of the DNA would show both markers present -

indicating
a hybrid.

"Isolating these markers is technically extremely challenging," says the
Hull laboratory's Professor Gary Carvalho. "However, Bernd succeeded in
identifying 10 such markers that were common to each of the three species,
and produced a specific signal within each species."

So, when a sample of tissue from a fish was sent to the laboratory, the

team
could extract its DNA, identify the markers, and confidently assign a
genetic history to the sample. By using this technique, Dr Hänfling
confirmed that the samples he analysed included hybrids between goldfish

and
crucian carp, and hybrids between crucian and common carp. This was clear
evidence that interbreeding does indeed occur, as the fisheries scientists
suspected.

But of more concern was the fact that the genetic analysis showed that a
small number of hybrid individuals had interbred or "back-crossed" with

pure
stock. "Of 250 samples I analysed, two were back-crosses," says Dr

Hänfling.
"This isn't a lot, but it indicates that it can happen."

The phenomenon of hybrids interbreeding or breeding with pure stock is
called introgression. Professor Carvalho explains why it is an important
issue. "The key is to protect the gene pool of the native species," he

says.
"Hybridisation can result in the degradation of the ability of the fish to
survive in its native habitat. Once you start to get introgression, you
start to get contamination of the gene pool, which can be detrimental to

the
survival of the species. This has been seen where escaped farmed salmon
breed with wild salmon, resulting in hybridisation and introgression. The
resulting offspring are less fit than their pure-bred cousins to withstand
the rigours of the environment, and have lower resistance to diseases and
have confused migrating behaviour, for example."

For Philip Bolton, the Hull research provides the hard evidence that
scientists need in order to devise appropriate conservation strategies for
the crucian carp. One fear is that the hybrids might become more

aggressive
than the pure species, and out-compete them. "I was impressed with the

power
of the DNA technology," says Bolton. "This work will give us solid
scientific support for any policies we introduce to protect the native
crucian population, and will help us to produce our updated field guide to
crucian carp, which will in turn help in their identification. The issue

of
introgression is interesting - and disturbing. We have anecdotal evidence
that in waters where it is suspected that hybrids exist, there has been a
dwindling of the native population."

Bolton hopes to organise a nationwide audit of pure crucian stocks in the
country so that these populations can be protected from contamination by
goldfish and common carp. "There is no doubt that the crucian-carp
population is under serious threat, and this has been further confirmed by
this study," he says. "As things stand now, it is not likely that the
crucian will be wiped out, but there is an outside potential for that to
happen if we don't act now."

In the meantime, Bolton has advice for anyone who can no longer look after
their pet goldfish. "Releasing fish into the wild is illegal without

consent
from the Environment Agency," he says. "Take the goldfish back to the

person
who sold it to you, or give it to a neighbour with a pond. If neither of
these are possible, contact your local Environment Agency office for
advice."




 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is Off
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Goldfish crankbaits? SHRED© Bass Fishing 12 December 3rd, 2003 05:51 PM
Fish much smarter than we imagined John General Discussion 14 October 8th, 2003 10:39 PM
Fish much smarter than we imagined John UK Coarse Fishing 8 October 8th, 2003 10:39 PM
Fish much smarter than we imagined John UK Sea Fishing 10 October 8th, 2003 10:39 PM


All times are GMT +1. The time now is 06:00 AM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 FishingBanter.
The comments are property of their posters.