RE: [RML] Little fish fights back

Anne et Christian (lespoussins at coditel.net)
Tue, 9 Aug 2005 15:46:16 +0200

Messages sorted by: [ date ][ thread ][ subject ][ author ]
Next message: Gary Lange: "RE: [RML] Little fish fights back"
Previous message: Scott Davis: "Re: [RML] Little fish fights back"

------=_NextPart_000_0009_01C59CF9.7AB1F580
Content-Type: multipart/alternative;
boundary="----=_NextPart_001_000A_01C59CF9.7AB1F580"

------=_NextPart_001_000A_01C59CF9.7AB1F580
Content-Type: text/plain;
charset="iso-8859-1"
Content-Transfer-Encoding: 8bit

Indeed but it is not only in the name of capitalism. It is also in the name
of personal interests. Mobutu does the same in several places only for the
pleasure of sport fishing. The fact is here to have a reason to bring
weapons in Central Africa.

Anyway, I’m working on a presentation about threatened species. The
introduction of Tilapia in several places in the world (even in Australia
and PNG) is a real problem. Even, in Europe introduction of sun perch
(Lepomis), bull-head catfish, black Bass or freshwater turtles stays a major
ecological damage. It begins to be difficult to find Carassius carassius or
even Gasterosteus aculeatus (who was a very common fish ten years ago).

And the same for our lovely bows. Anyone knows on this forum about the
situation of Glossolepis wanamensis or Chilatherina fasciata in Lake Wanam
(in cause tilapias).

We, as fish lovers, must avoid those damages such only as don’t hold exotic
species in outdoor ponds and try to hold and reproduce those who are
endangered (or even vanished) in our tanks. That’s not a so big
intervention but million drops are necessary to have a see.

Cheers

Christian

-----Message d'origine-----
De : r_m_l at yahoogroups.com [r_m_l at yahoogroups.com]De la part de
Michael Adams
Envoyé : mardi 9 août 2005 14:16
À : 'r_m_l at yahoogroups.com'
Objet : RE: [RML] Little fish fights back

Thanks for posting this...It's sad how much damage is done to people and the
environment in the name of capitalism...

_____

From: finsen at optusnet.com.au [finsen at optusnet.com.au]
Sent: Tuesday, August 09, 2005 6:24 AM
To: r_m_l at yahoogroups.com
Subject: [RML] Little fish fights back

Something of interest?
caio
Graeme
>From http://www.guardian.co.uk/life/feature/story/0,13026,1541613,00.html
The little fish fight back
An award-winning documentary portrays Lake Victoria as the site of an
ecological disaster. But, says Laura Spinney, the story may yet have a happy
ending
Thursday August 4, 2005
The Guardian < http://www.guardian.co.uk>
When film director Hubert Sauper showed the mosaic warts on his feet to a
Parisian doctor, his reaction was, "Woah! Where did you get those?" Sauper
explained that he had just returned from making a documentary in Tanzania,
and he thought he had probably picked them up in the fish-bone yard, where
barefooted women squelched through a seething mass of maggots, inhaling
dense ammonia fumes, to hang skeletal fish carcasses on racks to dry in the
sun.
The fish-bone yard is one of the more memorable images in Sauper's brutal
film, Darwin's Nightmare, which opens in US cinemas this month, having
already won 18 first prizes in international film festivals. It shows the
social and ecological catastrophe that was set in motion when, in the early
1960s, a man tipped a bucket of Nile perch into Lake Victoria and spawned a
fishing industry. It does not have a happy ending. But the sequel, should
there be one, just might. Biologists now believe that the lake is balanced
on a knife edge between total disaster and possible recovery.
Lake Victoria is the largest tropical lake in the world, the source of the
Nile and once upon a time, paradise for evolutionary biologists. Until the
60s, it was home to 500 species of small, colourful cichlid fish, each of
which was behaviourally and morphologically specialised to exploit a niche
in the lake ecosystem. The majority of the species evolved in a
record-setting 15,000 years, making the Lake Victoria cichlid "superflock"
one of the world's most spectacular examples of explosive radiation in
vertebrates.
Then along came the man with the bucket. Nile perch are not native to the
lake. They are beefy, fecund fish that can grow to almost two metres in
length, and they eat cichlids. As it happens, he was only the second man
with a bucket. The lake, which is the size of Ireland, straddles Tanzania,
Kenya and Uganda. The first introduction of species related to Nile perch
took place in 1954 in Uganda, when that country was still a British colony,
but the predator did not take off.
On both occasions it was introduced with nominally good intentions: to
provide local people with a richer source of protein than the bony, bland
cichlids they had hitherto lived off. The more cynical view is that it was
to improve sports fishing for European expats. Either way, the second
introduction was irresponsible, because by then ecologists had warned that
the consequences of introducing a top predator to an as yet poorly
understood ecosystem were entirely unpredictable.
With the benefit of hindsight, Sauper's film shows what those consequences
were - for humans. Within a couple of decades, Nile perch numbers had
exploded. Men flocked from the poverty-stricken hinterland of Tanzania to
make a living on the lake shore, leaving their families behind. Lawless
"fish cities" grew up around the filleting factories, peopled by fishermen,
prostitutes and feral, gluesniffing kids. Factory owners grew relatively
rich on the proceeds of a thriving export industry, while the locals ate the
sundried leftovers. Aids ravaged the fishing settlements and, when the
terminally sick limped home to be comforted by their relatives, the inland
villages as well.
Meanwhile, the lake itself grew sicker and sicker. By the mid-80s, it was
already estimated to have lost two-thirds of its cichlid species in a
massive wave of extinction. By the time Sauper finished filming last year,
commercial trawlers had been banned and the Nile perch, overfished
themselves, were eating each other - presumably because there were not
enough cichlids left to feed them.
The lake is also suffering from creeping eutrophication - an influx of
nutrients due mainly to deforestation of the lake shore, industrialisation
and human pollution. These nutrients feed large algal blooms that die and
sink to the bottom to be consumed by bacteria, which use up oxygen in doing
so. The water grows murkier, which suits the perch, because they can see
better in low light than cichlids. And crucially, female cichlids can no
longer distinguish the markings of males, which is how they select their
mates.
As male colour becomes obsolete as a signal for mate choice, Ole Seehausen
of the University of Bern, Switzerland and colleagues are finding that the
reproductive barriers are breaking down between some cichlid species which
sport different colours, and hybridisation is taking place. Red and blue
males of different species are giving way to males of a dull brown, and
losing their ecological specialisations - the difference in their feeding
habits, for instance - in the process.
Hybridisation can lead to a loss of diversity and is, therefore, generally
seen by biologists as a bad thing. But it could also be a force for
successful adaptation, and eventual recovery of diversity, Seehausen argues.
"By reshuffling the genes of two species, it can generate the genetic raw
material for new species with new specialisations - a novel combination of a
certain feeding behaviour with a particular habitat, say."
If that combination can fill an ecological niche not yet fully exploited by
other species, the hybrid could establish itself and thrive. There is
evidence that that is happening in Lake Victoria. A handful of the 200 or so
species once thought to be extinct seem to be reviving. But, says Seehausen,
"Many of the reviving populations look like recombinants of pre-existing
species."
Until the early 90s, most was known about the bigger, fish-eating cichlids
that swam in open waters and were the first to become extinct. But then
Seehausen's group discovered more than 100 previously unknown rock-dwelling
cichlids that kept to the shallower, coastal areas, where Nile perch do not
stray. They covered a broad spectrum of cichlid niches - from small
plankton-eaters to large algae-scrapers and fish-eaters. Since then,
cichlids have been found further out in open waters. Some of them could be
hybrids derived from these rock-dwellers.
Seehausen speculates that the lake's coastal bays and gulfs, where the water
is murkiest, act as a "hybridisation belt". Individuals of novel genetic
makeup are engendered here, and those that are well-adapted to life in the
altered lake may then move out into clearer, open waters, where there is a
greater choice of niches to exploit, and the females can see. Both
ecological and sexual selection then act to enforce their genetic isolation
one from the other - creating new species.
The key, then, is to have this balance between hybridisation and
diversifying pressures, between murky and clear. The lake is grossly
over-murky now. But, says Seehausen, "If the water clarity can be improved
again, it may yet be pushed back to levels where more diversity would again
be promoted." That is not such an unrealistic goal. But while there have
been some reforestation projects, and attempts to change farming practises
in the region, these have not yet halted the decline. So cichlid diversity
hangs in the balance. "It is always tricky to predict evolution,
particularly in cichlids," says Walter Salzburger, an evolutionary biologist
at Konstanz University in Germany. But he thinks it likely that new cichlid
species will adapt to the perch's presence. He and his colleagues have found
cichlids hiding in floating islands of papyrus in the lake, which are too
dense for the bulky perch to penetrate, and he thinks they probably have
other refugia - areas where the local conditions are favourable to them, and
where they can hang out until it is safe to leave and radiate again.
Victoria's satellite lakes may also act as refugia, he says. Some of these
are connected to the lake, some are not. Over geological time, connecting
channels may have formed and dissolved due to fluctuating water levels. But
even the fact that two lakes are presently cut off from one another does not
prevent cichlids from hopping between them. One explanation is that they are
carried by birds. Cichlids are mouth brooders, which means that females can
carry up to 30 juveniles in their mouths. Even if the mother dies in a
cormorant's beak, the fry could potentially survive to repopulate a new
lake. That hypothesis has yet to be proven. But, says Salzburger, "Cichlids
have colonised all the lakes - remote lakes, satellite lakes, crater lakes -
and they must have got there somehow."
So if hybridisation does not drive a new radiation, then recolonisation from
refugia could, but over a much longer time course - millennia as opposed to
decades. The two scenarios generate two very different short-term outcomes
for the lake and the people who live off it. But they could also work in
concert, says Salzburger, just as they may have done during the initial Lake
Victoria cichlid radiation.
Tijs Goldschmidt, a Dutch biologist who worked at the lake in the 80s, says
he is now careful about predicting the lake's future, since he warned that
once the cichlids were gone, the Nile perch population would crash, and
their corpses would be seen floating on the surface. That never happened,
and it was only in retrospect that he understood why not: with most of the
cichlids removed, prawns in the lake took their chance and boomed. Small
Nile perch ate prawns, slightly bigger perch ate prawns and a sardine-like
fish native to the lake, and the largest perch became cannabilistic, feeding
off the smaller ones. "That is a very unstable system, but so far it works,"
says Goldschmidt.
Even if the lake does recover its former diversity quickly, it will not be
the same diversity. For one thing, it will never now be rid of Nile perch.
There is also the major threat posed by eutrophication to consider. Human
beings, like cichlids, are distinguished by their adaptability, but if
eutrophication continues at the rate it is, then the lake will one day stop
providing both drinking water and protein. "A lake without oxygen would be a
disaster for about 30 million people," says Goldschmidt.
In that case, the misery portrayed in Sauper's film would only be the tip of
the iceberg, and recovery would be delayed by a major human catastrophe on a
scale that is, perhaps, impossible for us to imagine.
* More at www.darwinsnightmare.com < http://www.darwinsnightmare.com>
* What did you think of this article? Mail your responses to
life at guardian.co.uk < life at guardian.co.uk> and include your name and
address.

Regards
Paul Blake
paul.blake at nrm.qld.gov.au
Block A
80 Meiers Road
Indooroopilly QLD 4068
--------------------------------------
Ignorance more frequently begets confidence than does knowledge: it is those
who know little, and not those who know much, who so positively assert that
this or that problem will never be solved by science. - Charles Darwin
--------------------------------------

************************************************************************
The information in this e-mail together with any attachments is
intended only for the person or entity to which it is addressed
and may contain confidential and/or privileged material.
Any form of review, disclosure, modification, distribution
and/or publication of this e-mail message is prohibited.
If you have received this message in error, you are asked to
inform the sender as quickly as possible and delete this message
and any copies of this message from your computer and/or your
computer system network.
************************************************************************

SPONSORED LINKS
Marine biology
<http://groups.yahoo.com/gads?t=ms&k=Marine+biology&w1=Marine+biology&w2=Bio
logy&w3=Marine&w4=Marine+electronics&w5=Marine+supply&w6=Marine+engines&c=6&
s=108&.sig=NTQLNOZeUEreRveoTug0Fg>
Biology
<http://groups.yahoo.com/gads?t=ms&k=Biology&w1=Marine+biology&w2=Biology&w3
=Marine&w4=Marine+electronics&w5=Marine+supply&w6=Marine+engines&c=6&s=108&.
sig=YFUWTs9saKSRd2_7XjejsA>
Marine
<http://groups.yahoo.com/gads?t=ms&k=Marine&w1=Marine+biology&w2=Biology&w3=
Marine&w4=Marine+electronics&w5=Marine+supply&w6=Marine+engines&c=6&s=108&.s
ig=77_QnnrA3L1w2cxBGVJlAQ>
Marine electronics
<http://groups.yahoo.com/gads?t=ms&k=Marine+electronics&w1=Marine+biology&w2
=Biology&w3=Marine&w4=Marine+electronics&w5=Marine+supply&w6=Marine+engines&
c=6&s=108&.sig=KZr_KPqVIuMe2W1RVtUzxg>
Marine supply
<http://groups.yahoo.com/gads?t=ms&k=Marine+supply&w1=Marine+biology&w2=Biol
ogy&w3=Marine&w4=Marine+electronics&w5=Marine+supply&w6=Marine+engines&c=6&s
=108&.sig=mbuqPkRYLoOq05qPRyzCGA>
Marine engines
<http://groups.yahoo.com/gads?t=ms&k=Marine+engines&w1=Marine+biology&w2=Bio
logy&w3=Marine&w4=Marine+electronics&w5=Marine+supply&w6=Marine+engines&c=6&
s=108&.sig=cJh-S5hNWitR4_Hh2AWdgw>

_____

YAHOO! GROUPS LINKS

* Visit your group " r_m_l <http://groups.yahoo.com/group/r_m_l> "
on the web.

* To unsubscribe from this group, send an email to:
r_m_l-unsubscribe at yahoogroups.com
<r_m_l-unsubscribe at yahoogroups.com?subject=Unsubscribe>

* Your use of Yahoo! Groups is subject to the Yahoo! Terms of
Service <http://docs.yahoo.com/info/terms/> .

_____

------=_NextPart_001_000A_01C59CF9.7AB1F580
Content-Type: text/html; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable

<head>
<meta http-equiv=3DContent-Type content=3D"text/html; charset=3Diso-8859-1"=
>
<meta name=3DProgId content=3DWord.Document>
<meta name=3DGenerator content=3D"Microsoft Word 9">
<meta name=3DOriginator content=3D"Microsoft Word 9">
<link rel=3DFile-List href=3D"cid:filelist.xml at 01C59CF9.79BDD180">
<link rel=3DEdit-Time-Data href=3D"cid:editdata.mso at 01C59CF9.79BDD180">

<title>FW: Little fish fights back</title>

<style>

</style>
<o:SmartTagType namespaceuri=3D"urn:sche=
mas-microsoft-com:office:smarttags" name=3D"country-region"/><o:SmartTagTyp=
e namespaceuri=3D"urn:schemas-microsoft-com:office:smarttags" name=3D"Place=
Name"/><o:SmartTagType namespaceuri=3D"urn:schemas-microsoft-com:office:sma=
rttags" name=3D"PlaceType"/><o:SmartTagType namespaceuri=3D"urn:schemas-mic=
rosoft-com:office:smarttags" name=3D"State" downloadurl=3D"http://www.5iama=
s-microsoft-com:office:smarttags"/><o:SmartTagType namespaceuri=3D"urn:sche=
mas-microsoft-com:office:smarttags" name=3D"City" downloadurl=3D"http://www=
.5iamas-microsoft-com:office:smarttags"/><o:SmartTagType namespaceuri=3D"ur=
n:schemas-microsoft-com:office:smarttags" name=3D"place" downloadurl=3D"htt=
p://www.5iantlavalamp.com/"/>
</head>

Indeed but it is not only=
in
the name of capitalism.  It i=
s also
in the name of personal interests. 
Mobutu does the same in several places only for the pleasure of spor=
t
fishing.  The fact is here to=
have
a reason to bring weapons in Central Africa.<o:p></o:p></span=
>

Anyway, I’m working=
on a
presentation about threatened species.&nb=
sp;
The introduction of Tilapia in several places in the world (even in
Australia and PNG) is a real problem.  Even, in Europe introduction of sun perch (Lepomis),
bull-head catfish, black Bass or freshwater turtles stays a major ecologica=
l
damage.  It begins to be diff=
icult
to find Carassius carassius or even Gasterosteus aculeatus (who was a very
common fish ten years ago).<o:p></o:p>

-----Message
d'origine----- 
De : r_m_l at yahoogroups.=
com
[r_m_l at yahoogroups.com]De la par=
t de
Michael Adams 
Envoy=E9 : mardi 9 ao=
=FBt 2005
14:16 
=C0 : 'r_m_l at yahoogroup=
s.com' 
Objet : RE: [RML] Lit=
tle
fish fights back

<![if !supportEmp=
tyParas]> <![endif]><o:p></o:p>

Thanks for posting this...It's sad how =
much
damage is done to people and the environment in the name of capitalism...<o=
:p></o:p>

</spa=
n><o:p></o:p>

</div>

From:</=
b> finsen at optusnet.co=
m.au
[finsen at optusnet.com.au] 
Sent: Tuesday, August 09, 20=
05
6:24 AM 
To: r_m_l at yahoogroups.com<br=
>
Subject: [RML] Little fish
fights back<o:p></o:p>=

<o:p></o:p>

Something of interest?<f=
ont
color=3Dblack><o:p></o:p>

caio=
<o:p></o:p>

Graeme<o:p></o:p>

From <a
href=3D"http://www.guardian.co.uk/life/feature/story/0,13026,1541613,00.htm=
l"
target=3D"_blank">http://www.guardian.co.uk/life/feature/story/0,13026,1541=
613,00.html</a> 
The little fish fight back </fo=
nt><o:p></o:p>

An
award-winning documentary portrays <st1:place w:st=3D"on">Lake Victoria</st=
1:place>
as the site of an ecological disaster. But, says Laura Spinney, the story m=
ay
yet have a happy ending <o:p=
></o:p>

Thursday
August 4, 2005 
The Guardian <<a
href=3D"http://www.guardian.co.uk" target=3D"_blank">http://www.guardian.co=
.uk</a>>
<o:p></o:p>

When
film director Hubert Sauper showed the mosaic warts on his feet to a Parisi=
an
doctor, his reaction was, "Woah! Where did you get those?" Sauper
explained that he had just returned from making a documentary in <st1:count=
ry-region w:st=3D"on"><st1:place w:st=3D"on">Tanzania</st1:place></st1:coun=
try-region>,
and he thought he had probably picked them up in the fish-bone yard, where
barefooted women squelched through a seething mass of maggots, inhaling den=
se
ammonia fumes, to hang skeletal fish carcasses on racks to dry in the sun. =
<o:p></o:p>

The
fish-bone yard is one of the more memorable images in Sauper's brutal film,=
<st1:City w:st=3D"on"><st1:place w:st=3D"on">Darwin</st1:place></st1:City>=
's
Nightmare, which opens in US cinemas this month, having already won 18 firs=
t
prizes in international film festivals. It shows the social and ecological
catastrophe that was set in motion when, in the early 1960s, a man tipped a
bucket of Nile perch into <st1:place w:st=3D"on">Lake Victoria</st1:place> =
and
spawned a fishing industry. It does not have a happy ending. But the sequel=
,
should there be one, just might. Biologists now believe that the lake is
balanced on a knife edge between total disaster and possible recovery. </sp=
an><o:p></o:p>

Lake
Victoria is the largest tropical lake in the world, the source of the <st1:=
place w:st=3D"on">Nile</st1:place>
and once upon a time, paradise for evolutionary biologists. Until the 60s, =
it
was home to 500 species of small, colourful cichlid fish, each of which was
behaviourally and morphologically specialised to exploit a niche in the lak=
e
ecosystem. The majority of the species evolved in a record-setting 15,000
years, making the Lake Victoria cichlid "superflock" one of the
world's most spectacular examples of explosive radiation in vertebrates. </=
span><o:p></o:p>

Then
along came the man with the bucket. <st1:place w:st=3D"on">Nile</st1:place>=
perch
are not native to the lake. They are beefy, fecund fish that can grow to al=
most
two metres in length, and they eat cichlids. As it happens, he was only the
second man with a bucket. The lake, which is the size of <st1:country-regio=
n w:st=3D"on">Ireland</st1:country-region>,
straddles <st1:country-region w:st=3D"on">Tanzania</st1:country-region>, <s=
t1:country-region w:st=3D"on">Kenya</st1:country-region>
and <st1:country-region w:st=3D"on"><st1:place w:st=3D"on">Uganda</st1:plac=
e></st1:country-region>.
The first introduction of species related to Nile perch took place in 1954 =
in <st1:country-region w:st=3D"on"><st1:place w:st=3D"on">Uganda</st1:place=
></st1:country-region>,
when that country was still a British colony, but the predator did not take
off. <o:p></o:p>=

On both
occasions it was introduced with nominally good intentions: to provide loca=
l
people with a richer source of protein than the bony, bland cichlids they h=
ad
hitherto lived off. The more cynical view is that it was to improve sports
fishing for European expats. Either way, the second introduction was
irresponsible, because by then ecologists had warned that the consequences =
of
introducing a top predator to an as yet poorly understood ecosystem were
entirely unpredictable. <o:p=
></o:p>

With
the benefit of hindsight, Sauper's film shows what those consequences were =
-
for humans. Within a couple of decades, <st1:place w:st=3D"on">Nile</st1:pl=
ace>
perch numbers had exploded. Men flocked from the poverty-stricken hinterlan=
d of
<st1:country-region w:st=3D"on"><st1:place w:st=3D"on">Tanzania</st1:place>=
</st1:country-region>
to make a living on the lake shore, leaving their families behind. Lawless
"fish cities" grew up around the filleting factories, peopled by
fishermen, prostitutes and feral, gluesniffing kids. Factory owners grew
relatively rich on the proceeds of a thriving export industry, while the lo=
cals
ate the sundried leftovers. Aids ravaged the fishing settlements and, when =
the
terminally sick limped home to be comforted by their relatives, the inland
villages as well. <o:p=
></o:p>

Meanwhile,
the lake itself grew sicker and sicker. By the mid-80s, it was already esti=
mated
to have lost two-thirds of its cichlid species in a massive wave of extinct=
ion.
By the time Sauper finished filming last year, commercial trawlers had been
banned and the <st1:place w:st=3D"on">Nile</st1:place> perch, overfished
themselves, were eating each other - presumably because there were not enou=
gh
cichlids left to feed them. <o:p=
></o:p>

The
lake is also suffering from creeping eutrophication - an influx of nutrient=
s
due mainly to deforestation of the lake shore, industrialisation and human
pollution. These nutrients feed large algal blooms that die and sink to the
bottom to be consumed by bacteria, which use up oxygen in doing so. The wat=
er
grows murkier, which suits the perch, because they can see better in low li=
ght
than cichlids. And crucially, female cichlids can no longer distinguish the
markings of males, which is how they select their mates. <fon=
t
color=3Dblack><o:p></o:p>

As male
colour becomes obsolete as a signal for mate choice, Ole Seehausen of the
University of Bern, Switzerland and colleagues are finding that the
reproductive barriers are breaking down between some cichlid species which
sport different colours, and hybridisation is taking place. Red and blue ma=
les
of different species are giving way to males of a dull brown, and losing th=
eir
ecological specialisations - the difference in their feeding habits, for
instance - in the process. <o:p=
></o:p>

Hybridisation
can lead to a loss of diversity and is, therefore, generally seen by biolog=
ists
as a bad thing. But it could also be a force for successful adaptation, and=
eventual
recovery of diversity, Seehausen argues. "By reshuffling the genes of =
two
species, it can generate the genetic raw material for new species with new
specialisations - a novel combination of a certain feeding behaviour with a
particular habitat, say." <o:p></o:p>

If that
combination can fill an ecological niche not yet fully exploited by other
species, the hybrid could establish itself and thrive. There is evidence th=
at
that is happening in <st1:place w:st=3D"on">Lake Victoria</st1:place>. A ha=
ndful
of the 200 or so species once thought to be extinct seem to be reviving. Bu=
t,
says Seehausen, "Many of the reviving populations look like recombinan=
ts
of pre-existing species." <o:p></o:p>

Until
the early 90s, most was known about the bigger, fish-eating cichlids that s=
wam
in open waters and were the first to become extinct. But then Seehausen's g=
roup
discovered more than 100 previously unknown rock-dwelling cichlids that kep=
t to
the shallower, coastal areas, where <st1:place w:st=3D"on">Nile</st1:place>=
perch
do not stray. They covered a broad spectrum of cichlid niches - from small
plankton-eaters to large algae-scrapers and fish-eaters. Since then, cichli=
ds
have been found further out in open waters. Some of them could be hybrids
derived from these rock-dwellers. <o:p></o:p>

Seehausen
speculates that the lake's coastal bays and gulfs, where the water is murki=
est,
act as a "hybridisation belt". Individuals of novel genetic makeu=
p
are engendered here, and those that are well-adapted to life in the altered
lake may then move out into clearer, open waters, where there is a greater
choice of niches to exploit, and the females can see. Both ecological and
sexual selection then act to enforce their genetic isolation one from the o=
ther
- creating new species. <o:p=
></o:p>

The
key, then, is to have this balance between hybridisation and diversifying
pressures, between murky and clear. The lake is grossly over-murky now. But=
,
says Seehausen, "If the water clarity can be improved again, it may ye=
t be
pushed back to levels where more diversity would again be promoted." T=
hat
is not such an unrealistic goal. But while there have been some reforestati=
on
projects, and attempts to change farming practises in the region, these hav=
e
not yet halted the decline. So cichlid diversity hangs in the balance. &quo=
t;It
is always tricky to predict evolution, particularly in cichlids," says=
Walter
Salzburger, an evolutionary biologist at <st1:PlaceName w:st=3D"on">Konstan=
z</st1:PlaceName>
<st1:PlaceType w:st=3D"on">University</st1:PlaceType> in <st1:country-regio=
n w:st=3D"on"><st1:place w:st=3D"on">Germany</st1:place></st1:country-regio=
n>.
But he thinks it likely that new cichlid species will adapt to the perch's
presence. He and his colleagues have found cichlids hiding in floating isla=
nds
of papyrus in the lake, which are too dense for the bulky perch to penetrat=
e,
and he thinks they probably have other refugia - areas where the local
conditions are favourable to them, and where they can hang out until it is =
safe
to leave and radiate again. <o:p=
></o:p>

<st1:State w:st=3D"on"><st1:place w:st=3D"o=
n">Victoria</st1:place></st1:State=
>'s
satellite lakes may also act as refugia, he says. Some of these are connect=
ed
to the lake, some are not. Over geological time, connecting channels may ha=
ve
formed and dissolved due to fluctuating water levels. But even the fact tha=
t
two lakes are presently cut off from one another does not prevent cichlids =
from
hopping between them. One explanation is that they are carried by birds.
Cichlids are mouth brooders, which means that females can carry up to 30
juveniles in their mouths. Even if the mother dies in a cormorant's beak, t=
he
fry could potentially survive to repopulate a new lake. That hypothesis has=
yet
to be proven. But, says Salzburger, "Cichlids have colonised all the l=
akes
- remote lakes, satellite lakes, crater lakes - and they must have got ther=
e
somehow." <o:p=
></o:p>

So if
hybridisation does not drive a new radiation, then recolonisation from refu=
gia
could, but over a much longer time course - millennia as opposed to decades=
.
The two scenarios generate two very different short-term outcomes for the l=
ake
and the people who live off it. But they could also work in concert, says
Salzburger, just as they may have done during the initial <st1:place w:st=
=3D"on">Lake
Victoria</st1:place> cichlid radiation. <=
span
lang=3DEN-US style=3D'color:black;mso-color-alt:windowtext;mso-ansi-languag=
e:EN-US'><o:p></o:p>

Tijs
Goldschmidt, a Dutch biologist who worked at the lake in the 80s, says he i=
s now
careful about predicting the lake's future, since he warned that once the
cichlids were gone, the <st1:place w:st=3D"on">Nile</st1:place> perch popul=
ation
would crash, and their corpses would be seen floating on the surface. That
never happened, and it was only in retrospect that he understood why not: w=
ith
most of the cichlids removed, prawns in the lake took their chance and boom=
ed.
Small <st1:place w:st=3D"on">Nile</st1:place> perch ate prawns, slightly bi=
gger
perch ate prawns and a sardine-like fish native to the lake, and the larges=
t
perch became cannabilistic, feeding off the smaller ones. "That is a v=
ery
unstable system, but so far it works," says Goldschmidt. </font=
><font
color=3Dblack><o:p></o:p>

Even if
the lake does recover its former diversity quickly, it will not be the same
diversity. For one thing, it will never now be rid of <st1:place w:st=3D"on=
">Nile</st1:place>
perch. There is also the major threat posed by eutrophication to consider.
Human beings, like cichlids, are distinguished by their adaptability, but i=
f
eutrophication continues at the rate it is, then the lake will one day stop
providing both drinking water and protein. "A lake without oxygen woul=
d be
a disaster for about 30 million people," says Goldschmidt. </fo=
nt><o:p></o:p>

In that
case, the misery portrayed in Sauper's film would only be the tip of the
iceberg, and recovery would be delayed by a major human catastrophe on a sc=
ale
that is, perhaps, impossible for us to imagine. <o:p></o:p>

* More
at www.darwinsnightmare.com <<a href=3D"http://www.darwinsnightmare.com"
target=3D"_blank">http://www.darwinsnightmare.com</a>><fon=
t
color=3Dblack> <o:p></o:p>

* What
did you think of this article? Mail your responses to life at guardian.co.uk &=
lt;<a
href=3D"life at guardian.co.uk">life at guardian.co.uk</a>> and
include your name and address.<o:p=
></o:p>

<font
color=3Dblack><o:p></o:p>

Regards<font
color=3Dblack> 
Paul Blake 
paul.blake at nrm.qld.gov.au</font=
><font
color=3Dblack> 
Block A 
80 Meiers Road 
Indooroopilly QLD 4068<f=
ont
color=3Dblack> 
--------------------------------------=
 
Ignorance more frequently begets
confidence than does knowledge: it is those who know little, and not those =
who
know much, who so positively assert that this or that problem will never be
solved by science. - Charles Darwin<o:p></o:p>

--------------------------------------<font
color=3Dblack> <o:p></o:p>

<br
style=3D'mso-special-character:line-break'>
<![if !supportLineBreakNewLine]> 
<![endif]><o:p></o:p>=

************************************************************************</=
span> 
The information in this e-mail togethe=
r
with any attachments is 
intended only for the person or entity=
to
which it is addressed 
and may contain confidential and/or
privileged material. 
Any form of review, disclosure,
modification, distribution 
and/or publication of this e-mail mess=
age
is prohibited.  
If you have received this message in
error, you are asked to 
inform the sender as quickly as possib=
le
and delete this message 
and any copies of this message from yo=
ur
computer and/or your 
computer system network.  =
 
**************************************=
********************************** <o:p></o:p>

</div>

=20=20=20=20

</body>

------=_NextPart_001_000A_01C59CF9.7AB1F580--

------=_NextPart_000_0009_01C59CF9.7AB1F580
Content-Type: text/html;
name="header.htm"
Content-Transfer-Encoding: quoted-printable
Content-ID: <header.htm at 01C59CF9.79BDD180>

=
<![if !supportFootnotes]>

<![endif]><o:p=
></o:p>

</div>

<![endif]><o:p=
></o:p>

</div>

<![endif]><o:p=
></o:p>

</div>

<![endif]><o:p=
></o:p>

</div>

<fon=
t
size=3D1 color=3Dblack face=3D"Arial Narrow">v:\common\office\fmsm_word\templates\normal.dot</=
span><span
class=3DFilename><o:p></o:p></=
span>

</div>

</body>

------=_NextPart_000_0009_01C59CF9.7AB1F580--

Next message: Gary Lange: "RE: [RML] Little fish fights back"
Previous message: Scott Davis: "Re: [RML] Little fish fights back"