Tim Walsworth
Zoology 511
Wednesday Lab
Ecology of Your Fish
Yellow perch (Perca flavescens)
“Solar Ultraviolet Radiation and the Spawning Habitat of Yellow Perch, Perca
flavescens” by Williamson, et al identifies ultraviolet radiation from sunlight and
dissolved organic carbon (DOC) as abiotic factors that affect the behavior and function of
yellow perch. The UV radiation affects yellow perch by damaging their eggs, which
perch often lay in shallow waters. Therefore, the perch need to select a habitat to spawn
that is deep enough that the UV radiation is not intense enough to damage the eggs. As
the ozone continues to be depleted, lakes will be exposed to more intense UV radiation,
which would force the perch to spawn in deeper waters, which could expose them to
predation and colder temperatures. The colder temperatures would slow the maturation
of the eggs, thus leaving them vulnerable to predation for longer periods of time. This
paper used several charts and graphs to explain the results of the study. These were very
helpful, as it is much easier to explain the results visually than through words. The
graphs show the distribution of the eggs and the mortality rates of the eggs, among other
results.
“Ontogenetic Changes in the Distribution of Larval and Juvenile Yellow Perch
(Perca flavescens): A Response to Prey or Predators?” by Post, et al identifies prey
density and predator habitat as factors influencing where larval and juvenile yellow perch
live in lakes, whether it be offshore or nearshore, and at what times of day these areas are
occupied. The results of this experiment showed that the movements of the perch did not
always coincide with where their preferred prey was located. However, their movements
did not always coincide with a lack of predator presence, except the initial migration after
hatch. However, when the authors compared these results to other experiments done,
they concluded that this initial avoidance of predators would not hold up in all lakes,
especially those that had offshore predators, such as walleye. The graphs and tables used
in this paper were very helpful in explaining some of the points the authors were trying to
get across, such as which prey were preferred at different stages of perch development
and what time of day the fish were eating compared with what type of prey were in their
location.
Striped Marlin (Tetrapturus audax)
“Trophic dynamics and seasonal energetics of striped marlin Tetrapturus audax in
the southern Gulf of California, Mexico” by Abitia-Cardena, et al identifies chub
mackerel, the California pilchard, and the jumbo squid as the primary diet of the striped
marlin, and whose presence affects the range of the striped marlin. These organisms that
swim in large schools allow the striped marlin to maximize its energy intake as they can
eat many organisms in one feeding. Since these organisms swim in large schools, the
striped marlin does not need to expend much energy getting from one prey item to the
next, allowing for energy to be stored so as to be used for other processes, such as
reproduction and migration. The presence of these prey organisms south of the Gulf of
California leads the authors to conclude that the area is along a migration route for the
striped marlin, and also near an unknown spawning habitat. The tables and graphs in this
paper helped visualize the relationships between food/energy intake and time of year,
which species is being preyed upon at what time of year, and which species was most
prevalent in the stomachs of the striped marlin.
“Vertical and horizontal movements of striped marlin (Tetrapturus audax) near
the Hawaiian Islands , determined by ultrasonic telemetry, with simultaneous
measurement of oceanic currents” by Brill, et al identifies temperature change and
oceanic currents as two abiotic factors that affect the movement of striped marlin. The
striped marlin’s vertical movement was affected by the change in temperature with
change in depth. The authors found no absolute temperature preference, just preferred
temperatures relative to the mixed layer. The striped marlin spent nearly all of its time in
waters no cooler than that 2 degrees Celsius lower than that of the mixed layer, or in the
warmest water available. The horizontal movement of the striped marlin was affected by
the oceanic currents, which caused the marlins studied to swim in slowly curving arcs.
The figures in this article gave visual support to the ideas presented about direction of
travel being affected by the currents and also to the effect of temperature on swimming
depth. The individual graphs of depth against temperature for each fish followed were
especially interesting, as they showed how the patterns of depth control by temperature
were repeated in each fish.
Literature Cited
Abitia-Cardenas, L. A., Muhlia-Melo, A., Cruz-Escalona, V., Galvan-Magana, F. 2002.
Trophic dynamics and seasonal energetics of striped marlin Tetrapturus audax in
the southern Gulf of California, Mexico. Fisheries Research 57: 287-295.
Brill, R. W., Holts, D. B., Chang, R. K. C., Sullivan, S., Dewar, H., Carey, F. G. 1993.
Vertical and horizontal movements of striped marlin (Tetrapturus audax) near the
Hawaiian Islands , determined by ultrasonic telemetry, with simultaneous
measurement of oceanic currents. Marine Biology 117: 567-574.
Post, J. R., McQueen, D. J. 1988. Ontogenetic changes in the distribution of larval and
juvenile yellow perch (Perca flavescens): a response to prey or predators?
Canadian Journal of Fisheries and Aquatic Sciences 45: 1820-1826
Williamson, C. E., Metzgar, S. L., Lovera, P. A., Moeller, R. E. 1997. Solar Ultraviolet
Radiation and the Spawning Habitat of Yellow Perch, Perca flavescens.
Ecological Applications 7(3):1017-1023.