More effective ways to manage mixed populations of maturing and non-maturing
Atlantic salmon are needed, and a method to predict the percentage of maturing
salmon would be ideal. Maturing fish are known to swim slower and have a larger
condition factor (K) than non-maturing fish, and if differences are large, bimodality could
be evident in swimming speed and K factor data collected from mixed populations, and
used to predict the grilse (maturing salmon) percentage. To test this hypothesis, two
positions within the swimming aggregation were video recorded before and after the
fish were fed using a stereo camera system within commercial salmon farming cages.
From recorded images, swimming speed and morphological attributes were
determined. The expected bimodal distributions were not observed; all variables
showed a normal distribution with a single mode. Positional and temporal variations in
swimming speed and size measurements were found. The average swimming speed
was generally lower and the K factor higher in the upper section of the swimming
aggregation. Furthermore, the swimming speed and the condition factor were noted to
be respectively higher and lower before the feeding event. It was surmised that grilse
segregated themselves from the rest of the population, and / or differences in swimming
speed and other attributes between grilse and non-maturing salmon were too small to
statistically substantiate bimodality in the data sets. Results provide insight into the
relative importance of early grilse detection and removal in feeding management.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:BVAU.2429/6485 |
| Date | 11 1900 |
| Creators | Boucher, Eric Louis |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Relation | UBC Retrospective Theses Digitization Project [http://www.library.ubc.ca/archives/retro_theses/] |
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