The prevailing view regarding the fitness, evolution and
maintenance of male coho mating strategies has been based on
pieces of data from different salmon species. Since there is no
reason to suppose that all salmon species are the same, there is
a need for a quantitative description of male coho salmon
breeding behavior. The focus of this thesis is to provide a
detailed ethological study of male coho spawning behavior with
the objective of quantifying 1) patterns of movements, and 2)
interactions among males of different reproductive
tactics(alpha, satellite, jack), and breeding groups. Because
models that address the evolution and maintanence of
reproductive strategies require estimates of tactic fitness for
comparison, a secondary objective was to use the quantitative
data collected to speculate about costs of reproduction for
alternative reproductive tactics.
In total, 43 male coho were captured and radio tagged
during the 1992 and 1993 spawning escapements in Kanaka Creek.
Dominant hooknose males moved within a restricted stream segment
(mean daily distance (m) moved 86.33 SE 12.55) accessing the
females within the segment. Satellite hooknose males moved both
frequently and extensively (mean daily distance (m) moved 661.94
SE 200.13), often entering different waterways during their
breeding lifespan. Jack males were found to reside in a small
segment of stream throughout their breeding lifespan (mean daily
distance (m) moved 46.3 SE 40.3) and made use of a variety of
refuges, including the nest itself, from which to 'sneak'
fertilizations.
Sixty-two breeding groups were identified, each having a
anywhere from one to five male group members. Rates of
aggressive interactions (mean interactions per 10 minutes) were
found to differ significantly among males adopting different
reproductive tactics (P < 0.001). Alpha males had the highest
rate of aggressive interactions (15.2 SE 2.9 ) compared to
alternative male behaviors (first satellite 4.7 SE 0.9, second
satellite 5.7 SE 1.3, and jack 2.4 SE 0.9).
Aggression levels were found to differ significantly among
mating groups ( 0.01 > P > 0.025). Intermediate size groups had
the lowest aggression level, 11.57 SE 3.81 int/10 min (2 males)
and 13.49 SE 3.87 int/10 min (3 males). The highest level of
competitive interactions occurred when only one male and one
female were present (29.05 SE 12.50 int/10 min). Pairs of
combatants explained the increasing rate of aggression with
group size for groups containing more than one reproductive
tactic (2 to 5 males)(0.75 <P< 0.90).
Environmental conditions on the spawning grounds
influenced male behavior. Entry into tributaries was correlated
with precipitation. When temperatures and flow decreased dramatically during the week of Dec 20-26 (1993) ,
manoeuvrability was inhibited, and movement decreased. During
storm events in Thornvale Creek, turbidity increased and
spawning behavior ceased. As season progressed and available
females decreased, males were observed to engage in escalated
contests in the absence of females.
The evidence gathered during this investigation indicates
that the evolution and maintenance of male coho mating
strategies is more complex than previously described. Hooknose
males that adopt alternative reproductive tactics differ
significantly in their migration distances on the spawning
grounds and rates of competitive interactions. Furthermore,
there is a strict adherence to behavioral tactics and an
abundance of intermediate sized males in the population. Thus,
the results of this study support the idea that the satellite
tactic is not an unsuccessful one.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:BVAU.2429/7652 |
| Date | 05 1900 |
| Creators | Prince, Angela |
| 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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