Maria Sundaram
Ecology 510
February 12, 2008
Paper 1: The hearing abilities of the silver carp (Hypothalmichthys mobilix) and bighead
carp (Aristichthys nobilis).
Q1: The experimenters wanted to know whether an acoustic deterrent for these
fish could be found. They hypothesized that an acoustic deterrent set at the right
parameters would have the desired effect.
Q2: Using the Auditory Brainstem Response, fish were tested for their hearing.
The results of these tests showed that these fish are most sensitive to sound waves
between 750 and 1500 Hz. This test also showed that these fish have higher thresholds to
sounds below 300 Hz and above 2000 Hz. This suggests that the hearing of these fish is
acute enough to ensure the success of an acoustic deterrent for these fish.
Q3: The figures in this paper helped me a great deal to understand the
experimenters’ methods. Without these figures, I would not have understood fully how
they tested the Auditory Brainstem Response, nor would I have appreciated the tonotopic
sensitivity of carp.
Paper 2: Competitive interactions between age-0 bighead carp and paddlefish. Biotic C
Q1: This paper hypothesized that there would be competitive interaction between
bighead carp and paddlefish living in the same body of water. To test this, experimenters
developed mesocosms within ponds containing six paddlefish, six bighead carp, three
paddlefish and three bighead carp together, or no fish at all (a total of four groups).
Q2: They measured a number of different factors in the water and found that
water chemistry variables (dissolved oxygen, turbidity, conductivity, temperature, etc.)
were similar across groups and that their effect was only transient. A measurement of
zooplankton density showed that in the mesocosms with fish, zooplankton was decreased
from the control; but zooplankton density did not differ significantly among groups of
fish. Relative growth was measured and it was found that relative growth was negative
for bighead carp in the mesocosm with only bighead carp; it was also negative for
paddlefish in the mixed-fish mesocosm and the paddlefish-only mesocosm. Most
interestingly, the relative growth for bighead carp was positive in the mixed-fish
mesocosm. This result implies that bighead carp has a potential to successfully compete
with paddlefish for resources.
Q3: The two figures and one table in this paper described what was outlined
clearly in the abstract, in slightly more detail. They were not crucial to my understanding
of the experiment but would have been helpful to understand the more minute details of
the measurements that were made.
Paper 3: Nest distribution shaping within-stream variation in Atlantic salmon juvenile
abundance and competition over small spatial scales. Pseudo -abiotic
Q1: The experimenters pointed out that a patchy distribution of a population in a
stream leads to variations in population density. They wondered if this could be applied
to Atlantic salmon populations as well.
Q2: The construction of artificial nests in different points along a stream—using a
“patchy” distribution and a “dispersed” distribution—showed significantly varied
population densities in the patchy distribution, whereas in the dispersed distribution,
population density was relatively constant. The experimenters then posited that the way
in which a fish population is distributed can have major effects on juvenile competition
and other within-species interactions.
Q3: The figures in this paper were especially helpful for me to see the effects of
varying population densities on the entire population. They also helped me understand
how the experiment was set up.
Paper 4: Does increased abundance of sea lice influence survival of wild Atlantic salmon
post-smolt? Biotic
Q1: This paper suggested that the abundance of sea lice feeding off wild Atlantic
salmon would mean a decrease in the catch rate of Atlantic salmon.
Q2: The experimenters expected a 2% rate of infection of sea lice on untreated
Atlantic salmon. They also released a number of Atlantic salmon into the wild that were
given protection against sea lice. Results showed a higher recapture rate of the smolts that
were reared in the hatchery and were given protection against sea lice than the originally
wild Atlantic salmon. The conclusion the experimenters made was that sea lice may be
marginally effective on wild Atlantic salmon post-smolt mortality.
Q3: The figures in this paper mostly helped me to understand where this
experiment took place. A map clearly outlined the rivers and streams in Norway that
were studied. The other tables and graphs showed what was already outlined in the
abstract; however, they did illustrate the point of marginality perhaps better than the text.
Sources
Einum, S., Nislow, K.H., Mckelvey, S., and Armstrong, J.D. 2008. Nest distribution
shaping within-stream variation in Atlantic salmon juvenile abundance and
competition over small spatial scales. Journal of Animal Ecology. 77:167-172.
Hvidsten, N.A., Finstad, B., Kroglund, F., Johnsen, B.O., Strand, R., Arnekleiv§, J.V.,
and Bjørn, P.A. 2007. Does increased abundance of sea lice influence survival of
wild Atlantic salmon post-smolt? Journal of Fish Biology. 71:1639-1648.
Lovell, J.M., Findlay, M.M., Nedwell, J.R.,and Pegg, M.A. 2006. The hearing abilities of
the silver carp (Hypothalmichthys molitrix) and bighead carp (Aristichthys
nobilis). Comparative Biochemistry and Physiology. 143A:286-291.
Schrank, S.J. and Guy, C.S. 2003. Competitive interactions between age-0 bighead carp
and paddlefish. Transactions of the American Fisheries Society. 132:1222-1228.