| dc.description.abstract | The life history and population dynamics of the northern pike
(Esox lucius) within Squeers Lake, Ontario were studied in order
to provide information on pike found within oligotrophic lakes.
Results clearly demonstrate the Squeers Lake northern pike
population is relatively stable but small in size, has a very low
production rate, exhibits rapid growth, an early age of maturity
and an intermediate life span. The low availability of spawning
(and to a lesser extent nursery) habitat apparently regulates
population size. The rapid growth may be the result of abundant
food, lack of serious competition for food resources and presence
of favourable environmental conditions. Epilimnetic summer
temperatures 16-21°C) within the main lake basin were very near
optimal for "adult" pike (ie 18-20°C, Casselman, 1978), whereas
summer temperatures within the Western Arm (which formed the main
spawning and nursery area within the lake) were near optimum for
young-of-the-year and yearling pike (ie 26°C, Hokansen et al 1973).
To assess accuracy in age and growth assessment for the
Squeers Lake northern pike population, the validity of using scales
and cleithra was examined. The high percent frequency of
agreement, low index of average error (Beamish and Fournier 1981)
and index of precision (Chang 1982) indicate both scales and
cleithra are equally suitable tissues for assigning age structure
to Squeers Lake northern pike provided that marks interpreted as
annuli are in fact annually formed. An examination of the accuracy
of age estimates through the use of partly known aged fish (via iii
tetracycline labelling and mark-recapture methods) confirmed that
the checks identified on both aging tissues were in fact annuli.
Cleithra, were, however, more accurate for northern pike > age 10.
Therefore, when age estimates are required without killing the
fish, the use of scales can be recommended provided that the
population is relatively fast growing and precision levels between
the two tissues do not exceed 5%.
In order to further determine what factors may influence
northern pike growth and population size, the influences of lake
morphometry and chemistry on 14 northwestern Ontario populations
(including Squeers Lake) were investigated. Northern pike
populations found within deep-oligotrophic lakes exhibited low
population densities, a superior growth rate, piscivory and were
spawning and nursery habitat limited. Northern pike populations
from meso-eutrophic lakes had much greater population densities,
exhibited much poorer growth rates, were generally opportunistic
predators and appeared to be food limited. Northern pike from
mesotrophic and shallow-oligotrophic lakes exhibited intermediate
population size and growth rates with the maximal individual size
of fish from these populations approaching that of northern pike
from deep-oligotrophic lakes. With the increased acceptance of
individual lake management, a number of management alternatives are
proposed. | |
