Fishing News - Peacock Bass Coloration Explained
Paper Explains Peacock Coloration
A recently completed research paper explaining the
variability in coloration of Cichla temensis, (the giant peacock bass) will be
published in an upcoming issue of “Neotropical Ichthyology”, a peer reviewed scientific
journal. Until recently, much of the fishing, management and scientific
community has believed these variants to be two separate species, or
subspecies, or even male and female differences.
The two extremes of peacock bass coloration are so wildly different
that they go by separate names (“açu” and “paca” in Brazil and “Speckled” and
“3-Bar” peacock bass in the U.S. sportfishing community). The new article
explains the nature of the color variation and describes the research that led
to the new understanding.
The project was undertaken because experienced peacock bass anglers
have observed several phenomena that brought the established beliefs into
question. First, not only are there two extremes in coloration, but anglers
routinely encounter a whole range of intermediate patterns. Furthermore, anglers
often catch fish involved in spawning activity, but these are always in the
3-bar form. The existing beliefs failed to explain this. In an effort to answer
the questions raised by these observations, the research, performed under the
joint auspices of Rutgers University (NJ) andThe University of Amazonas (Manaus), examined the question
based on a new hypothesis. Could these variants all be the same fish undergoing
seasonal changes related to their spawning behavior?
The project defined several coloration categories or stages
(see the photos 1 - 4 in column A in the illustration) to serve as working
tools and then examined the problem from three viewpoints.
First, it compared fish from each of the color categories to
other species of peacock bass that shared the same water, using traditional
taxonomic techniques (morphometrics). This confirmed that the variants didn’t
belong to any of the other species. Next, the variants were subjected to DNA testing,
which showed that they were indeed all members of the same species. Finally,
using precise measurements and surgical and photomicrographic techniques, the
study showed that these color and pattern variants were actually individual
fish changing their coloration cyclically over the course of the Amazon’s
yearly rainy and dry seasons. They gradually change from the speckled pattern to
the 3-bar pattern as they prepare to spawn during the dry season, remaining in
the 3-bar pattern until they finish guarding their babies.
The illustration shows the coloration variants as they
change from one pattern to another in the four stages defined by the project.
Column B shows the ovaries for the each of the stages. As a fish changes from
the speckled (paca) to the 3-barred (açu) form, the ovaries enlarge, becoming
thicker and fuller in preparation for spawning. By stage 4, they are large and
distended. Column C shows photographs of the contents of the ovaries
themselves, taken under the microscope. In the speckled stage, immature
precursors to eggs (called oocytes) are visible. As a fish progresses through
the stages, eggs begin to form and become mature. By stage 2, they begin to
show nuclei (containing genetic material). In stage 3, the eggs begin to fill
with the yolk that will provide the fry’s first food.
The eggs in stage 4 are large and fully mature and ready to
be deposited on a submerged wood surface in the peacock’s large nest.
The study precisely weighed both ovaries and testes
(collectively gonads) of two hundred fish in each of the coloration stages and showed
that the mathematical relationship between gonad size and coloration stage is
statistically significant. It is the same in both males and females, as is the
color change itself.
This new information allows anglers to better understand
these fish. For fishermen, this kind of knowledge is power. The better we know
our quarry, the more effectively we can pursue and catch it.
Scientists know that color can have biological value. Before
the spawn, the 3-bar coloration may help spawning fish find partners, saying
“Look how beautiful I am, spawn with me!” Later on, like other brightly colored
animals, they may be advertising the threat they pose. For example, brightly
colored poisonous frogs are warning potential predators not to eat them; the
results of that meal could be very bad for the predator. In the same fashion,
brilliantly colored, fry-guarding peacock bass parents may be warning other
fish to avoid trying to eat their babies; the results could be fatal for the
would-be predator. If you’ve ever caught a big peacock under a fry ball with a
prop bait, you’ll understand the accuracy of this threat immediately.
At the other color extreme, non-spawning fish are busy going
about the business of eating and fattening up for the long fast associated with
They need to hunt effectively in the flooded forests
bordering Amazon lagoons and backwaters. If you’ve ever looked into the dark, tea-stained
waters at the edge of a lagoon with their submerged wood, dappled with
leaf-filtered sunlight, you’ll understand exactly how a dark, speckled predator
can disappear into the shadows.
Camouflage is a very effective hunting tool.
Most peacocks spawn near the end of the dry season when low water
levels make more spawning area available. However, not all spawn at the same
time and different spots have different relative depths, so you’ll likely see
all of the coloration stages during a typical fishing trip. Now you can observe
them with a new perspective.
New information also provides scientists with a platform
from which to launch future studies - and further research is indeed underway.
The study was performed by, and the upcoming article was
authored by Paul Reiss of Acute Angling with invaluable assistance, guidance
and co-authorship provided by Dr. Ken Able of Rutgers and Dr. Tomas Hrbek, Dr.
Izeni Farias and Mario Nunez of the University of Amazonas. Funding was primarily
provided by Acute Angling, with generous assistance from many anglers who have
contributed funds for equipment purchases for the study’s jungle laboratory.
The journal “Neotropical Ichthyology” can be found online and
in print. The article will be available in its technical form on our website
sometime after it has appeared in the journal.
Edited by Acute Angling - 26/Feb/2012 at 10:51pm