This PowerPoint presentation looks at my senior research presentation on the invasive species Pterygoplichthys disjunctivus, in Volusia Blue Spring, Florida. I discussed the implications that this species has had on this important ecosystem and addressed the methods which we used to have a greater understanding of how to better manage these species.

1. Introduction
Pterygoplichthys disjunctivus is an invasive species
originally from the Amazon Basin. Over the past two decades,
species of this family have established globally in several
tropical and sub-tropical regions, one of these being Volusia
Blue Spring (Gibbs et al., 2013). Pterygoplichthys disjunctivus’s
ability to withstand several environmental factors such as low
oxygen levels, desiccation, and high salinity levels has allowed
this species to successfully invade and alter ecosystems
(Rueda-Jasso et al., 2013). In part, it is also successful as
females produce close to 30,000 eggs per season and males
provide parental care (Hoover et al., 2005; Gibbs et al., 2008;
Rueda-Jasso et al., 2013). Due to this species’ increasing
worldwide distribution, it is vital to understand its life history
patterns (Gibbs et al., 2008).
Figure 1. Pterygoplichthys disjunctivus in Blue Spring
Population age and growth patterns for P. disjunctivus in
Volusia Blue Spring were established by Gibbs et al. (2013)
using patterns of otolith band pair deposition and associating
those patterns with seasonal conditions. Over the years, we
have observed size differences between males and
females, with males being longer and leaner, and females
being shorter and wider. Our goal was to use otoliths to
analyze the age and growth rates of male and female P.
disjunctivus. Based on our observations of their size
differences, we hypothesized that P. disjunctivus in Volusia
Blue Spring would grow at different rates throughout their
lives (Gibbs et al., 2013).
Methods
We collected Pterygoplichthys disjunctivus from 2012-2014
using pole spears, bringing a maximum sample of 20 fish back
to the lab on each monthly sampling date. The fish were
sacrificed with an overdose of the topical anesthetic MS222.
Standard length was measured to the nearest 0.5 cm with an
Aquatic Ecosystems Fish Measuring Board and Mass was
recorded to the nearest 5 g using a triple beam balance. Each
fish was then identified as male or female.
Figure 2. At least one lapillal otolith (A) was extracted from the
semicircular canals of each fish by sawing through the skull just
anterior to the gill opening. A total of 169 otoliths were removed,
glued on glass slides with cyanoacrylate cement, and given an
identification number. Saggital sections were made by grinding
down one or both sides of the otoliths using a modified turntable
and ultra-fine sand paper. Otoliths were further smoothed with
polishing paper.
Figure 3. Otoliths were viewed under a Ziess Axiostar Plus
compound microscope under magnifications of 50-100x. Age was
estimated by counting fast and slow growth band pairs, as you
would count the rings of a tree; age of each otolith was estimated
three separate times by two different readers. (L) Fast (pale) and
slow (dark) growth bands of two year old Pterygoplichthys
disjunctivus. (R) Otolith of five year old Pterygoplichthys
disjunctivus illustrating the repeated patterns of dark and pale
growth bands.
Methods
We performed an Analysis of Covariance (ANCOVA) to
compare male and female growth rates. We plotted our
estimated ages against standard length for all males, females,
and both genders combined to see how accurate our
estimates were.
Age and Growth of Male and Female Pterygoplichthys
disjunctivus in Volusia Blue Spring, Florida
Jennifer Gooch, Department of Biology, Stetson University, DeLand, FL
Results
Pterygoplichthys disjunctivus age estimates from both
readers were pooled and combined with those of Gibbs et
al. (2013) to obtain a larger sample size (n= 311). We
used a Coefficient of Variation (CV) to determine the
consistency of the age estimates we made for each fish.
Highly variable fish (CV>20) were eliminated from this
study as unreliable reads (n=10). We also calculated an
Index of Precision (D), which needed to be <5 to be
considered reliable. After eliminating the highly variable
fish, an average CV was calculated for the remaining fish
and found to be 8.39. D was calculated and was found to
be 4.84.
Conclusions
• Our hypothesis that male and female
Pterygoplichthys disjunctivus in Volusia Blue
Spring would grow at different rates was not
supported (P = 0.70), although males are longer than
females at any given age.
• Mature males and females likely expend the same
amount of energy during reproduction, with females
laying eggs and males providing parental care (Rueda-
Jasso et al., 2013). However, they each appear to
grow in different dimensions (P= 0.002), with males
growing longer and leaner, and females growing
shorter and wider.
• By understanding their growth rates, we can contribute
to the knowledge of Pterygoplichthys disjunctivus basic
biology. Our study can help managers control P.
disjunctivus populations in Volusia Blue Spring and in
other areas where this invasive species thrives.
Acknowledgements
I thank Dr. Gibbs for being my mentor and for helping
me throughout the duration of the research project. I also
thank Devin Burris for being my research partner. I thank
Dr. Bennington, Dr. Farrell, and Dr. Lind for helping me
with the statistical analyses. I also thank Blue Spring
State Park and the Stetson Biology Department for
allowing me to conduct my research.
Literature Cited
Gibbs, M., Shields, J., Lock, D., Talmadge, K., Farrell, T. 2008. Reproduction in an invasive
exotic catfish Pterygoplichthys disjunctivus in Volusia Blue Spring, Florida, U.S.A. Journal
Of Fish Biology, 73(7): 1562-1572.
Gibbs, M., Kurth, B., & Bridges, C. 2013. Age and growth of the loricariid catfish
Pterygoplichthys disjunctivus in Volusia Blue Spring, Florida. Aquatic Invasions, 8(2): 207-
218.
Hoover, J. J., Killgore, K. J., Cofrancesco, A. F. 2004. Suckermouth catfishes: threats to
aquatic ecosystems of the United States? Aquatic Nuisance Species, 4: 1-13.
Rueda-Jasso, R.A., Campos-Mendoza, A., Arreguin-Sanchez, F., Diaz-Prado, E., Martinez-
Palacio, C.A. 2013. The biological and reproductive parameters of the invasive armored
catfish Pterygoplichthys disjunctivus from Adolfo López Mateos El Infiernillo Reservoir,
Michoacán-Guerrero, Mexico. Revista Mexicana De Biodiversidad, 84: 318-326.
Figure 4. Although our age estimates were somewhat
noisier than Gibbs et al. (2013) (we tended to
underestimate age for both males and females relative to
standard length), the general pattern that fish increase in
standard length as they age, is still evident.
The parallel trend lines and an Analysis of Covariance
(ANCOVA) did not support a significant difference
between male and female growth rates (p = 0.70),
however, male are significantly larger than females (p =
0.002) (ANCOVA).
y = 7.2154x + 15.061
R² = 0.4618
y = 7.2149x + 13.272
R² = 0.4197
0
10
20
30
40
50
60
1 2 3 4 5 6
StandardLength(cm)
Age (years)
Male Female