1. Introduction
The presence or absence of Atlantic salmon (Salmo salar) in an ecosystem is an important
indicator of the general health of the broader aquatic system and the salmons’ high position in
the food chain makes its presence integral to the future conditions of the system (OMNR and
TRCA, 2005). As one of the most sensitive fish species in the watershed, the Atlantic salmon
is now extirpated in many regions of Ontario due to overfishing, pollution, habitat destruction
and the construction of dams and weirs preventing its migration (Ibid). In the Toronto region,
especially around the Humber River, human-made barriers have made it difficult for Atlantic
salmon to reach historic spawning grounds. Poor water quality from degraded areas along the
river (Ibid) has lead to a low success rate of about 20 percent in the wild (Fleming College,
Frost Campus, Fish Hatchery, 2011).
In the year 2000, 30 adult Atlantic salmon were released into the Humber River, some
with tags, in order to study interactions among salmon populations throughout the spawning
period and to assess spawning success (OMNR, 2002). However, over the winter many of the
embryos were unable to survive and the test results were inconclusive (Ibid). The
reintroduction of Atlantic salmon into the watershed would require stocking and attempts to
expand the range of other important fish species including walleye in order to ensure greater
success (OMNR and TRCA, 2005). The following study assesses why Atlantic salmon have a
lower success rate in the wild based on the health of the sample size in stock tanks.
This study focused on determining if there was a statistically significant difference
between the average length (in millimetres) and weight (in grams) of yearling Atlantic salmon
in Stock Tanks C1-C4 at the Fleming College, Frost Campus, Fish Hatchery. A sample size of
14 fish from each tank were measured by Ecosystem Monitoring and Assessment students.
Variables and control measures of the study will be discussed. The hatchery aims for a 70
percent success rate for release into the wild (Fleming College, Frost Campus, Fish Hatchery,
2011).
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2. Discussion
At the Fleming College, Frost Campus Fish Hatchery, many factors were considered that
could affect the growth of the Atlantic salmon in the stock tanks. The most significant
variables were the changes in time of day, individuals performing the assessment, and the
particular day of the week. Every person undergoing the procedure has their own technique
for the assigned protocol. Varying experiences and knowledge may contribute to these
changes. In order for the results to be conclusive and without bias, the same protocol should
be followed, but this is quite difficult to ensure. Equipment variations such as problems with
the weight scale and the level of anaesthetic in parts per million will have a significant impact
on the final results. Personal technique has a considerable impact on the protocol as some
Atlantic salmon yearlings may have been placed in the fresh water and dried for varying
lengths of time which would affect the weight of the specimen. If a yearling was not fully
anaesthetized it made it much more difficult to record its length as it was still in motion. The
sample size remained consistent at 14, but the feeding schedule and quantity of feed affected
the yearlings’ weight so it was important to account for time of day relative to feeding. The
temperature of the water varied which may have affected oxygen levels. Fish density affected
the overall appearance and sometimes weight of specimen because of tank competition for
food and nipping of fins. Bin size and stock tank size are also factors.
As previously discussed, the two main factors of this study, length and weight, have
fluctuating variables that may alter the results of the study. The small sample size of 14
impacted the results of these variables because of low variability. The more reliable method
for indicating fish growth is its individual length as this measurement is less likely to change
than its weight. However, this is not to assume that the Atlantic salmon’s length is not
affected, as it is shaped by many factors such as sex, site, cohorts, or specific environment
(Chambers and Miller, 1995). The measured weight of Atlantic salmon in this experiment
showed much statistical variance most significantly based on feeding; time of day, amount of
food, and even temperature at time of feeding (Arnason, Papst, and Hopky, 1992). The
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3. protocol and technique of those experimenting could also affect the weight, such as the length
of time the caught yearling was placed in the fresh water bath, as excess water could
contribute to the weight. Accurate reading of the weight scale, proper use of the scale, and
other factors affect the weight. Therefore, the weight of the Atlantic salmon is most likely
going to exhibit bias due to the many changing variables that could be represented in the
experiment. The best way to control for this is to monitor the time of day the experiment was
conducted relative to the time of feeding to control for variation. This shows that the most
conclusive results would be determined if all participants recorded their results at the same
time of the day while accounting for feeding time.
The difference between the average fish weight and the calculated bulk weight
rapid calculation is 59.58107143 grams for the former and 62.01785929 grams for the latter.
The bulk size should not be equal to but similar to the individual calculation and this is
reflected in the results. The results are different due to the changing variables that also exist
in this section. The protocol in which the assignment was exercised has the potential to alter
the results. The protocol needs to be followed precisely in order for the results to be the
same. The bulk weight rapid calculation measurement may be higher than the individual
measurements because of excess water content, technique including time spent in
anaesthetic, and time of day experiment was taken. Bulk weight could also be larger due to
exposure period and consumed food (Espmark and Baeverfjord, 2008).
Based on this study, it can be concluded that the Atlantic salmon remains an
important, yet sensitive, member of aquatic ecosystems. It should be noted that there were
many variables in this experiment, so a larger sample size might be the more conclusive
method for measurement. The results of this experiment can be used for further studies
about the survival rates of Atlantic salmon in the Sir Sandford Fleming College, Frost Campus,
Fish Hatchery based on the variables and control methods utilized in this exercise.
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4. References:
Arnason A.N., Papst M.H., Hopky G.E. 1992. Modelling the Increase in Variation of Fish
Weight. Canadian Journal of Fisheries and Aquatic Sciences. Vol. 49, 1992 Feb 16.
Chambers R. Christopher, Miller Thomas J. 1995. Evaluating Fish Growth by Means of Otolith
Increment Analysis: Special Properties of Individual-Level Longitudinal Data. Recent
Developments in Otolith Research. Columbia, South Carolina: University of South Carolina
Press. p. 735.
Espmark Asa Maria, Baeverfjord Grete. 2008. Effects of hyperoxia on behavioural and
physiological variables in farmed Atlantic salmon (Salmo solar) parr. [online]. Available from:
http://www.springerlink.com/content/94053198753n1327/fulltext.pdf. Accessed: 2011 Feb 1.
Fleming College, Frost Campus, Fish Hatchery. 2011. Personal Communication.
Ontario Ministry of Natural Resources. 2002. Lake Ontario Fish Communities and Fisheries:
2002 Annual Report of the Lake Ontario Management Unit.
Ontario Ministry of Natural Resources and Toronto Regional Conservation Authority (OMNR
and TRCA). 2005. Fisheries Management Plan. [online]. Available from:
https://ozone.scholarsportal.info/bitstream/1873/1698/1/263253.pdf. Accessed: 2011 Jan
28.
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