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Tropical Fish:
The Biotope Concept
What’s a biotope?
A biotope aquaria is an aquarium that is setup to simulate a natural habitat. The fish,
plants, water chemistry, and furnishings
are similar to those that can be found in a
specific natural setting.
So – didn’t we DO this already with
our NATIVE tank?
YES!!! Now you get to model TROPICAL
ENVIRONMENTS!
Tropical Fish Environments
Freshwater Tropical Regions of
the World
The Nearctic Region: our Native
Tropicals
Our Native Tropicals, cont. Florida
Why so little in North America?
The Great American Interchange
After the late Mesozoic breakup of Gondwana, South
America spent most of the Cenozoic era as an island
continent whose "splendid isolation" allowed its fauna to
evolve into many forms found nowhere else on earth.
These included Cichlidae, Loricariidae (Suckermouth
catfishes) and Characidae (Tetras). The niches filled by
these families in South America had already been
largely filled by Centrarchidae (Sunfishes), Ictaluridae
(Bullhead catfishes), and Cyprinidae (Minnows). Thus
the Competitive Exclusion Principle, along with a cooler
drier climate, effectively blocked successful colonization
of North America north of central Mexico on a grand
scale.
The Great American Interchange
Sciaenids
Cichlids
Characins
Poecilids
The most biodiversity on the
Planet: the Neotropics
Central America Rocky Lakes
Volcanic rocks makes for a hard water,
with high pH.
Lake Atitlan
Convict Cichlid
Rainbow Cichlid
Central America Rivers
San Juan River
The leaf litter from the surrounding
forests make the water somewhat
more acidic.
Guppy
Swordtail
Molly
South America River
Orinoco
Amazon
Lush rain forest generates a lot
of leaf material. The dissolved
tannic acids makes for a soft
water,with low pH.
South America Backwater Pool
During the rainy season, vast areas of
tropical rainforest are flooded. Many of
these areas lie permanently underwater
(igapos), while others dry out during the
dry season (varzeas). Lush rain forest
generates a lot of leaf material. The
dissolved tannic acids makes for a very
soft water,with low pH. Lack of currents
makes for a very nutrient-rich, dark
waters – (blackwater)
Cichlid Heaven: the Ethiopian
Region
African Ephemeral Pools
Niger Delta Cichlids
Tropical Fish of the Congo
Cichlid PARADISE: The Great
Rift Lakes of East Africa
Africa is splitting
apart. The area where
this happening is the
Great Rift Valley. Here
lie some the largest,
deepest lakes in the
world. Due to the high
mineral content, and
little aquatic plant
growth, the water is
extremely hard and
alkaline.
In the 1970’s, due to changing
diplomatic relations between
several African Nations and the
Western European nations,
scientists were allowed into
Eastern Africa's Rift Lake Valley for
the first time in decades. What
followed during the next two
decades was the emergence of
Lake Malawi and Lake Tanganyika
as the two richest sources of
indigenous species of cichlid
fishes in the world, as hundreds of
fascinating new species were
being discovered. The first such
species imported into the "hobby"
was the "golden Nyasa Cichlid,"
certainly among the most striking
cichlids ever.
An African Cichlid’s
NIGHTMARE: one more reason
to abhor that word!
The introduction of the Nile Perch into Lake Victoria, the largest
lake in Africa, which is bordered by Kenya, Uganda and Tanzania,
was a tragedy for the one diverse ecosystem of the Lake, while
from an economic perspective its status is quite disputable. As the
Nile Perch is simply overwhelming in size and appetite over the
other native fish species in the lake, which have evolved for
thousands of years under isolation and in which a particular family
of fish, the Cichlids (in particular haplochromine Cichlids) have
successfully radiated to fill virtually every available niche within the
segregated habitat, it has caused the extinction of more than 200
species of endemic native Cichlids through direct predation, which
is a monumental loss of biodiversity for Lake Victoria. The special
environmental conditions that enabled the high level of endemism
(over 400 endemic species of Cichlids once) have created a fragile
ecosystem as a whole in which the invasion of the Nile Perch has
more than wreaked havoc in. In Lake Victoria individuals often grow
to 250kg, and when fish of such a size forage they are mostly
indiscriminate, so many larger Perches have taken to cannibalism
quite happily. This in turn sustains the high population further, and
most of the native fish are negatively affected, including the
predatory fish species, as there are none that could match the Nile
Perch in size and appetite. With the decline of many algae-feeding
Cichlids in the originally pristine ecosystem of Lake Victoria, the
Algae prospered and plundered the water of oxygen, and low
oxygen levels was what many native fish could not cope with, albeit
not a problem for the introduced Perches. The deeper waters are
most oxygen-deficient and this drove many of the native fish into a
narrower depth range, reducing the species diversity. As the Algae
decomposed detritus is produced, which degrades the water quality
to intolerable levels for many native fish.
The South Asian Tropics
Rivers of South Asia
Barbs, Anabantids, & Botias
Wallace’s Line
Alfred Russel Wallace, the father of zoogeography, formulated his ideas on evolution by natural
selection while observing and collecting wildlife in the islands of Southeast Asia. He was
particularly impressed by the sudden difference in bird families he encountered when he sailed
some twenty miles east of the island of Bali and landed on Lombok. On Bali the birds were clearly
related to those of the larger islands of Java and Sumatra and mainland Malaysia. On Lombok the
birds were clearly related to those of New Guinea and Australia. He marked the channel between
Bali and Lombok as the divide between two great zoogeographic regions, the Oriental and
Australian. In his honor this dividing line, which extends northward between Borneo and Sulawesi,
is still referred to today as Wallace's Line.
Australian Region
Over the Rainbow…
Rainbowfishes form the most speciose group of fishes inhabiting freshwaters within the Australia-New Guinea region. Despite this,
relatively little is known about the biology and ecology of the majority of rainbowfish species in their natural habitat. A review of the
literature currently available does highlight a number of gaps in our knowledge of many species. There are some species where
there is a considerable amount of information available while there are other species where there is little or no information
available. In addition, there are specific gaps in the information available in otherwise well documented species. As well as a
number of species that are in need of additional research, information such as reproduction and natural habitat conditions is
limited. These include water quality requirements, spawning frequency and habitat preferences. Spawning information in the wild is
particularly lacking for almost all species, as is general information on egg and larvae development, habitat preference and water
quality tolerances.
Despite such a variety of species, research into their basic natural biology and ecology is lacking and most information that is
available is mainly based on aquarium observations. Obviously, there is urgent need for such studies in order that species can be
properly conserved and managed.
For more on setting up biotopes…
http://fish.mongabay.com/biotope.htm
http://badmanstropicalfish.com/bio-type.html
http://www.wetwebmedia.com/ca/volume_2/
cav2i6/biotopes_p1/biotopes_p1.htm
ENJOY!