142
S.M. Adams
uct of its life history adaptation and natural selection, which allows it to compete
successfully in its environment.
Allocation of available energy for growth, metabolism, reproduction, and lipid
storage usually follows species-specific patterns or strategies. If the environment
is significantly altered through natural or anthropogenic changes, then until a new
steady state is reached, allocation patterns may be disrupted and the continued
success of a species in that particular environment may be compromised. Alterations in energy allocation patterns from the expected or normal state could be a
useful indicator of aquatic system dysfunction. Studies are needed that focus on
how changes in allocation patterns can ultimately affect ecologically significant
functions such as reproduction, survival, and growth dynamics. For example, in
aquatic systems that become increasingly affected by a variety of stressors, increasing amounts of assimilated energy would be diverted to metabolic processes
for maintaining or repairing damaged biological systems. In this situation, less
energy would be available for growth, reproduction. or lipid storage. Under these
circumstances, it would be worthwhile to know the relationship between environmental perturbations. changes in allocation patterns. and the effect on lipid storage, survival. and reproductive performance.
7.2.3. Reproductive Development and Early Life History
Population failure in many fish species is highly variable and may occur, in part,
because of reduced reproductive fitness of adult populations during years of low
food supply and inadequate fat reserves. During the winter fasting period, fish
gonads are developed by using lipid reserves (Love, 1980) which are the main
source of energy for the synthesis of generative tissue (Shul'man, 1974) (Fig. 7.1).
Poor reproductive success have been attributed to both the reduced condition of
the gonad during maturation and decreased larval success following hatching.
When maternal diets are deficient, insufficient transfer of lipids to developing
oocyte may reduce fecundity and the viability of the progeny (Heming and Buddington, 1988; Watanabe. 1985). Lipids that are transferred to the gonads are
incorporated as nutritive material in the yolk of the oocyte and serve as the
principal endogenous food source for the developing embryo. The level of fat
reserves in the body and the rate of their utilization in gonad maturation, therefore,
is a major determinant of reproductive success.
Inadequate fat reserves have been implicated in the reduced reproductive success of several fish species. Because of a lack of summer food, mature yellow
perch were unable to build sufficient fat reserves to meet the demands of oogenesis and winter maintenance requirements (Newsome and Leduc, 1975). In walleye, reproductive success and variations in year-class strength have been partially
explained by the energy condition of the female and the proportion of the stock
able to spawn successfully each year (Henderson et aI., 1996). Thus, recruitment
success in this species is dependent on the energy acquired before spawning,
including that energy obtained from reabsorption of previous gonadal tissue (Henderson and Nepszy, 1994). Tyler and Dunn (1974) also reported that in winter
S.M. Adams
uct of its life history adaptation and natural selection, which allows it to compete
successfully in its environment.
Allocation of available energy for growth, metabolism, reproduction, and lipid
storage usually follows species-specific patterns or strategies. If the environment
is significantly altered through natural or anthropogenic changes, then until a new
steady state is reached, allocation patterns may be disrupted and the continued
success of a species in that particular environment may be compromised. Alterations in energy allocation patterns from the expected or normal state could be a
useful indicator of aquatic system dysfunction. Studies are needed that focus on
how changes in allocation patterns can ultimately affect ecologically significant
functions such as reproduction, survival, and growth dynamics. For example, in
aquatic systems that become increasingly affected by a variety of stressors, increasing amounts of assimilated energy would be diverted to metabolic processes
for maintaining or repairing damaged biological systems. In this situation, less
energy would be available for growth, reproduction. or lipid storage. Under these
circumstances, it would be worthwhile to know the relationship between environmental perturbations. changes in allocation patterns. and the effect on lipid storage, survival. and reproductive performance.
7.2.3. Reproductive Development and Early Life History
Population failure in many fish species is highly variable and may occur, in part,
because of reduced reproductive fitness of adult populations during years of low
food supply and inadequate fat reserves. During the winter fasting period, fish
gonads are developed by using lipid reserves (Love, 1980) which are the main
source of energy for the synthesis of generative tissue (Shul'man, 1974) (Fig. 7.1).
Poor reproductive success have been attributed to both the reduced condition of
the gonad during maturation and decreased larval success following hatching.
When maternal diets are deficient, insufficient transfer of lipids to developing
oocyte may reduce fecundity and the viability of the progeny (Heming and Buddington, 1988; Watanabe. 1985). Lipids that are transferred to the gonads are
incorporated as nutritive material in the yolk of the oocyte and serve as the
principal endogenous food source for the developing embryo. The level of fat
reserves in the body and the rate of their utilization in gonad maturation, therefore,
is a major determinant of reproductive success.
Inadequate fat reserves have been implicated in the reduced reproductive success of several fish species. Because of a lack of summer food, mature yellow
perch were unable to build sufficient fat reserves to meet the demands of oogenesis and winter maintenance requirements (Newsome and Leduc, 1975). In walleye, reproductive success and variations in year-class strength have been partially
explained by the energy condition of the female and the proportion of the stock
able to spawn successfully each year (Henderson et aI., 1996). Thus, recruitment
success in this species is dependent on the energy acquired before spawning,
including that energy obtained from reabsorption of previous gonadal tissue (Henderson and Nepszy, 1994). Tyler and Dunn (1974) also reported that in winter