| dc.description.abstract | Important aspects of the life history and population dynamics
of the northern pike, Esox lucius, in Savanne Lake, Ontario
were studied during 1977 and 1978. Feeding relationships involving
northern pike and walleyes, Stizostedion vitreum vitreum,
and the initial impact of an open water sport fishery on these
unexploited populations were also examined,
Schumacher-Eschmeyer spring population estimates of 2,621
and 2,508 for 1977 and 1978, respectively, represented the mature
northern pike population (ages 4-14 and greater than 45 cm in
length) most vulnerable to the sampling gear. Adult northern
pike did not appear to establish home ranges but moved throughout
the lake during the year. A sex ratio of 1.19 females to every
male was observed. Females were heavier than males at a given length and grew more rapidly at most ages. Fecundity estimates
of 9,675 eggs per unit body-weight (kg) and an average of 20,081
eggs per mature pike were low for this species. Growth rates of
Savanne Lake northern pike were slightly below average growth
rates in Ontario and Minnesota waters and probably reflect the
chemical characteristics of this lake, as well as the high density
of piscivores relative to available food. Total mean biomass
and annual production for age-groups 4-12 were estimated at
8,69 kg*ha[superscript-1] and 2,76 kg*ha[superscript-1]*yr[superscript-1] respectively, for the 1977-78 period. Low annual production was attributed to slow growth, low annual mortality, and the dominance of older age-groups in this unexploited population.
Relative abundance and seasonal availability determined the
incidence of prey consumed by adult northern pike and walleyes.
Yellow perch (Perca flavescens) especially juveniles (60-110 mm
in length), and shallow water ciscos (Coregonus artedii) predominated
in observed annual diets of both species. Invertebrates, notably mayfly nymphs (Ephemeridae) and crayfish (Orconectes
virilis), were of seasonal importance. Prey size was not a
critical factor in determining predation, since the majority
of examined northern pike and walleyes were capable of consuming
far larger prey than were actually found in their stomachs.
Northern pike appeared more vulnerable to angling than
walleyes and comprised the greater portion of total angling
yield for the open water study period. Catch per unit efforts
of 0.88 fish per man-hour and 1.12 kg per man-hour for northern
pike and 0.66 fish per man-hour and 0.48 kg per man-hour for
walleye resulted from minimal angling pressure (1.24 hours per
ha). Angling catches consisted primarily of northern pike,
50-70 cm in length and 5-7 years old, and walleyes, 40-50 cm
in length and 6-10 years old, representing dominant age and
size classes in the mature populations. | |
