Scientific Value of Keeping Native Fishes In
Aquaria
Lawrence M. Page, Principal
Scientist
Center for Biodiversity, Illinois Natural History Survey,
Champaign, IL 61820
Fishes are kept in aquaria for a variety of reasons. Most aquarists keep
fishes because they enjoy observing the tremendous diversity of body shapes,
colors, and behaviors. Others keep fishes for the explicit purpose of learning
something new about them. Keeping only a few species of fish can quickly teach
an aquarist and his/her family some valuable lessons about the natural world.
Our native fishes are quite diverse – about 800 species are found in the
freshwaters of North America – and they show a great variety of morphological
designs and behaviors.
Keeping fishes in aquaria has led to many original
observations. It is one of the best methods for making scientific discoveries
about fishes, which can be extremely difficult to study in streams and lakes. In
fact, some fishes are nearly impossible to study in detail in the bodies of
water in which they normally are found. For example, fishes that live in turbid
rivers cannot be seen by human observers who are either above or in the water.
Fishes that live in clear water can be observed from a stream bank or by someone
with a snorkel, but often they are extremely uncooperative with a person trying
to study them. In aquaria, conditions can be controlled to simulate natural
conditions and may lead to observations that otherwise would not be made.
Although sometimes difficult to observe even in aquaria, spawning
behaviors can be particularly fascinating and relevant to species protection.
Some fishes spawn by scattering eggs, some lay eggs in secluded places and guard
them, others give birth to living young. One group of native fishes on which our
knowledge of spawning behaviors has grown greatly from aquarium observations are
darters. With about 180 species, darters are one of the two most diverse groups
of North American fishes. (The other group, the minnows, contains about 250
species.) Aquarium observations on darters have revealed a variety of
reproductive behaviors. Some bury their eggs in the substrate, some attach them
to plants or the sides of rocks, and some sequester them under rocks and guard
them. We know now the breeding habits of 103 species of darters. Only 25 of
these species have been observed in nature; the other 78 have been observed only
in aquaria.
Females of some of the egg-guarding species of darters prefer
to lay eggs with males that already are guarding eggs in their nests rather than
spawn with males without eggs. They shun males at least to some degree that have
not yet demonstrated that they can successfully guard eggs. Males of these
species compete for these choosy females and, in some species, have evolved
morphological traits that can make them more attractive to females. They have
evolved structures on their fins that look very much like eggs. These egg-mimics
can attract females to nest sites even though no eggs are present. Although not
always this spectacular, other amazing behaviors are shown by North American
fishes, and many of these behaviors are known only because they have been
observed in aquarium-held fishes.
In the United States, 70 species of
fish are listed as federally threatened or endangered because of habitat loss
and other forms of environmental degradation. This depressingly large number of
endangered fishes exists because people do not care or know enough to demand
that land be developed in a way that protects habitat for our native plants and
animals. The more that we know about our native fishes, the more we will
appreciate them for their beauty and their habits, and the more we will want to
protect their environments.
Scientists make excellent use of aquarium
observations. In fact, we would know far less about our native fishes if we did
not keep them in aquaria. Aquarists enjoy keeping fishes, but our native fishes
are the more significant beneficiaries of this
activity.