BUT NO HIGHER
http://www.telegraph.co.uk/earth/main.jhtml?xml=/earth/2008/02/26/eafish126.xml
BY Charles Clover  /  26/02/2008

Fish can count, according to scientists, who have found that North
American mosquito fish have the ability to count up to four.

Previously it was known that fish could tell big shoals from small
ones, but researchers have now found that they have a limited ability
to count how many other fish are nearby.

This means that they have similar counting abilities to those observed
in apes, monkeys and dolphins and humans with very limited
mathematical ability.

Christian Agrillo, an experimental psychologist at the university of
Padua in Italy said: “We have provided the first evidence that fish
exhibit rudimentary mathematical abilities.”

Last year, he and his colleagues showed that if a female mosquito fish
is harassed by a male, she will try to avoid his attentions by seeking
solace in the largest nearby shoal; demonstrating that the fish can
tell bigger shoals from smaller ones.

The team first conducted a series of experiments to see whether a lone
mosquito fish would prefer to join a shoal of between two and four
others.

The results, published on the BBC Worldwide’s natural history site,
loveearth.com, show that females preferred to join shoals that were
larger by just one fish significantly more often – consistently
preferring shoals of four fish rather than three fish, and
consistently preferring shoals of three fish over those containing
just two.

A second series of experiments revealed the fish’s ability to process
larger numbers. The fish were not able to directly count over four,
but they were able to distinguish between larger numbers if they
differed by a ratio of 2:1.

For example, the fish could distinguish between a shoal of 16,
compared to a shoal of eight others. But they could not tell the
difference between a shoal of 12 compared to a shoal of eight, a ratio
of 3:2. This demonstrates that fish are able to visually estimate
larger numbers – but not very accurately.

Prof Angelo Bisazza, who led the latest research, said that fishes’
numerical abilities were actually on a par with the numerical
abilities of monkeys and human infants between six and 12 months old,
who were both able to visually count small numbers and less accurately
estimate larger ones.

Adult humans use a third counting mechanism, in which they verbally
count much larger numbers.

Dr Agrillo said: “The most interesting thing is that fish performance
is very similar to what is observed in adult humans who possess a very
limited vocabulary for numbers.”

For example, speakers of the Amazonian language Mundurukú lack words
for numbers beyond five. “Their limits in quantity tasks closely
resemble what we found in pre-verbal organisms such as fish!” he
added.

A variety of animals, including pigeons, parrots, raccoons, ferrets,
rats, monkeys and apes are to varying degrees capable of either
counting, adding or subtracting numbers. Most need to be trained to do
so.

Without training, adult rhesus monkeys are capable of subtracting
small numbers, and are capable of representing the number zero.

Wild lions apparently have a rudimentary ability to count. When a
pride of lions hears the roar of an approaching lion then two or three
females, rather than a lone greeter will always go out to meet the
stranger. But if two approaching lions can be heard, the resident
females send out four of their own.

Do fish count? Spontaneous discrimination of quantity in female
mosquitofish
http://lib.bioinfo.pl/pmid:18247068

BY Christian Agrillo, Marco Dadda, Giovanna Serena, Angelo Bisazza
Department of General Psychology, University of Padova, via Venezia 8,
35131, Padua, Italy

CONTACT
http://cprg.psy.unipd.it/agrillo.htm
email: christian [dot] agrillo [at] unipd [dot] it

ABSTRACT
http://www.springerlink.com/content/r8n475m318240045/
The spontaneous tendency to join the largest social group was used to
investigate quantity discrimination in fish. Fish discriminated
between shoals that differed by one element when the paired numbers
were 1vs2, 2vs3 and 3vs4, but not when 4vs5 or larger. Using large
numerosities (>4), the ability to discriminate between two numbers
improved as the numerical distance between them increased and a
significant discrimination was found only with ratios of 1:2 or
smaller (4vs8, 8vs16 and 4vs10). Experiments to control for non-
numerical variables evidenced the role played by the total area of
stimuli with both large and small numerosities; the total quantity of
movement of the fish within a shoal appeared also important but only
when large numerosities were involved. Even though the pattern of
discrimination exhibited by female mosquitofish is not fully
consistent with any of the existing models of quantity representation,
our results seem to suggest two distinct mechanisms in fish, one used
to compare small numbers of objects and one used when larger
numerosities are involved.

SIMPLE MATH
http://www.loveearth.com/us/blog/news25february2008

Fish can count
BY Matt Walker  /  26 February 2008

Females preferred to join shoals that were larger by just one fish

Fish can count. We know that fish are able to tell big shoals from
small ones, but now researchers have discovered that fish can actually
count how many other fish are nearby.

‘We have provided the first evidence that fish exhibit rudimentary
mathematical abilities,’ says experimental psychologist Christian
Agrillo of the University of Padova in Italy, who made the discovery
while studying a group mosquitofish (Gambusia holbrooki).

Mosquitofish originally come from North America, but they were also
introduced to Europe almost a century ago. Females are highly social
and form shoals of between two and 20 individuals. Last year, Agrillo
and his colleagues showed that if a female mosquitofish is harassed by
a male, she will try to avoid his attentions by seeking solace in the
largest nearby shoal; demonstrating that the fish can tell bigger
shoals from smaller ones. But now the same team, led by professor
Angelo Bisazza, has discovered that the fish actually have a
rudimentary ability to count, and that they appear to do so using
similar cognitive mechanisms as other, higher vertebrates. ‘They show
a performance very similar to what is observed in apes, monkeys and
dolphins,’ Agrillo says.

His team first conducted a series of experiments to see whether a lone
mosquitofish would prefer to join a shoal of between two and four
others. Females preferred to join shoals that were larger by just one
fish significantly more often; consistently preferring shoals of four
fish rather than three fish, and consistently preferring shoals of
three fish over those containing just two. This means the fish were
clearly able to count up to four and demonstrates that fish have a
rudimentary mathematical ability to visually count how many items are
present if the number is small.

A second series of experiments revealed the fish’s ability to process
larger numbers. The fish were not able to directly count over four,
but they were able to distinguish between larger numbers if they
differed by a ratio of 2:1. For example, the fish could distinguish
between a shoal of 16, compared to a shoal of eight others. But they
could not tell the difference between a shoal of 12 compared to a
shoal of eight, a ratio of 3:2. This demonstrates that fish are able
to visually estimate larger numbers – but not very accurately.

Although it doesn’t sound much, it is actually on a par with the
numerical abilities of monkeys and human infants between six and 12
months old, who are both able to visually count small numbers and less
accurately estimate larger ones.

‘Our results show that organisms as diverse as primates and fish,
which diverged more than 450 million years ago, share similar
capabilities in the precise discrimination of small quantities,’ the
researchers say in Animal Cognition (DOI:10.1007/s10071-008-0140-9),
where they publish their findings.

Adult humans use a third counting mechanism, in which they verbally
count much larger numbers. Yet as Agrillo points out: ‘The most
interesting thing is that fish performance is very similar to what is
observed in adult humans who possess a very limited vocabulary for
numbers.’ For example, speakers of the Amazonian language Mundurukú
lack words for numbers beyond five. ‘Their limits in quantity tasks
closely resemble what we found in pre-verbal organisms such as fish!’
says Agrillo.

DO MOSQUITOFISH ONLY KILL MOSQUITOS?
http://en.wikipedia.org/wiki/Mosquitofish
http://landscaping.about.com/cs/pestcontrol/a/mosquitocontrol_3.htm
http://www.gambusia.net/

“Gambusias have traditionally been referred to as mosquitofish based
on the assumption they are ideal for mosquito larvae control. While we
prefer to retain gambusia in the title to this page (since this allows
for world wide understanding), we would like to suggest adoption of a
more suitable name for these species outside their natural range,
damnbusia. This is not an effort to damn this poor innocent fish, but
to inform the masses that this species can be a major pest and in many
cases more suitable alternatives exist for mosquito larvae control.
Hence we feel the name is far more educational and valuable than the
misnomer of mosquitofish.”

Gambusia and mosquito control

Gambusia holbrooki and G. affinis (Cyprinodontiformes: Poeciliidae)
are native to southern and eastern USA, but now (following
translocation) have an extensive global distribution. Where mosquito-
borne diseases pose a threat to human health, and native fish are not
suitable control agents (such as urban areas in Thailand and
Venezuela) stocking water bodies with poeciliids (such as gambusia and
guppies Lebistes reticulatus) may be one of the few means of mosquito
control. These poeciliids are well-suited to stagnant waters, where
they tend to remain stationary just below the water surface, using the
relatively oxygen-rich interface layer. However, the effectiveness of
gambusia as a mosquito control agent is unclear. Gambusia may prefer
to consume macro-invertebrates other than mosquito larvae
(particularly large instars). Some of these macro-invertebrates
consumed may include species which also prey on mosquito larvae.
Gambusia, not having the aestivation/embryonic diapause capability of
some Cyprinodontiformes, die out in seasonal ponds, requiring a
restocking program. In any event, the larvae of many mosquito species
develop in rain-filled tree hollows and peridomestic containers, such
as coconut shells and discarded packaging, concealed from vertebrate
predators.

Gambusia as a competitor with native species

Interspecific competition for resources may extend to predation, by
gambusia, of eggs and larvae of endemic fishes and amphibians. Milton
& Arthington (1982) and Courtenay & Meffe (1989) listed reports that
implicated gambusia in the decline of various native fishes. In
Australia, gambusia was suggested to be an imminent threat to red
finned blue eye (Scaturiginichthys vermeilipinnis, Pseudomugilidae)
and Edgbaston goby (Chlamydogobius squamigenus, Gobiidae) (Unmack &
Brumley, 1991; Unmack, 1992; Wager, 1994, 1995; Wager & Unmack, in
prep). They also negatively effect southern blue eye (Pseudomugil
signifer) populations (Howe et al., 1997) and tadpoles (Morgan &
Buttemer, 1997; Webb & Joss, 1997). Glover (1989) reported gambusia
caused a decrease in desert goby (Chlamydogobius eremius) and spangled
perch (Leiopotherapon unicolor, Terapontidae) populations inhabiting
Clayton Bore in South Australia. Speculation that gambusia preyed on
the eggs and larvae of rainbowfish (Melanotaeniidae) in the wild
(Arthington & Lloyd, 1989; Arthington, 1991) was confirmed over summer
1997/98 in a field study in the upper Orara River, near Karangi, New
South Wales (Ivantsoff & Aarn, 1999). In New Zealand, Barrier & Hicks
(1994) showed that although gambusia was harassed by the larger black
mudfish (Neochanna diversus, Galaxiidae), gambusia ate their larvae.

Many examples from North America demonstrate the negative effects of
gambusia. Due in large part to predation, gambusia have eliminated
Gila topminnow (Poecilliopsis o. occidentalis) from almost it’s entire
range. Populations only persist where gambusia are absent or in a few
springs where other as yet unknown ecological characters allow them to
coexist (Minckley et al. 1991). The other subspecies, the Yaqui
topminnow (P. o. sonoriensis) is also in great danger as gambusia are
only just starting to invade and spread throughout the Yaqui River
system. Gambusia have a major impact on some pupfish (Cyprinodon spp.)
populations. While no extinctions due to this have been recorded,
coexisting populutions tend to be quite depressed in abundance.
Evidence collected in part by Unmack (unpub. data) from Ash Meadows,
Nevada suggests that when gambusia are decreased in abundance by
physical removal, significantly higher numbers of pupfish occur within
a year. Gambusia have also been demonstrated to cause extinction of
California newt (Taricha torosa populations (Gamradt & Kats, 1996).
Much to Diamond’s amazement gambusia are freely given out to anyone
who wants them in southern California. To directly quote Diamond
(1996);

“I phoned the Los Angeles County [West Vector Control] … District at
310-915-7370. In answer to my questions, a staff member told me: “Yes,
they would give me mosquitofish; no, there would be no cost to me; no,
I would not have to identify myself, fill out an application or
explain what I intended to do with the fish; no, the fish are harmless
and present no dangers of which I should be aware; yes, I could have
100 of them”.”

In summary, there is ample evidence that gambusia poses a threat to
endemic species in parts of Australia, New Zealand, and North America.
Hence the need to develop a gambusia control strategy. Complete
eradication is unlikely to be attainable, and may not be desirable.
Some options concerning biological agents are considered below. Other
options, including alteration of water flow rate, netting, and
application of piscicides have been trialed but are presently outside
the scope of this discussion.