138
S.M. Adams
ing of how food availability and lipid reserves ultimately dictate important life
processes such as overwinter survival and reproductive performance. For example, for the major economic and ecological species of concern, and particularly
those from temperate and north-temperate areas that experience seasonal pulses in
energy and environmental parameters, a better understanding is needed concerning the relationships between minimal levels of fat reserves and the probability of
overwinter survival and future reproductive success. In addition, the relationships
between fish food availability during the growing season, levels of lipid stores in
the late fall, and future year-class strength should be more clearly defined. Within
the context of food availability, knowledge of the temporal patterns in total lipids
and fatty acid composition of the major prey species would also be useful in
helping to predict overwinter survival and future reproductive success. Even
though they are more difficult to quantify, it is also important to identify densitydependent processes that are instrumental in optimizing lipid levels in fish during
the growing season for overwinter survival and reproductive success. For example, the relative importance of changes in competition for food through changes in
intraspecific and interspecific competition, the role of density-dependent breeding
and spawning behavior (which could extend or reduce the feeding and growing
period), and competition for preferred habitats for feeding, spawning, and shelter
are all important for maximizing the amount of available energy ultimately allocated to lipid storage. Understanding these relationships between environmental
factors, lipid reserves, survival, and reproductive success is key to effective management of fishery resources and for maximizing the future success of fishery
populations.
7.2.2. Energy Allocation Strategies
Many fish species display annual cycles in growth and lipid storage that are tightly
coupled to levels of ecosystem production, particularly lipid production in the
phytoplankton (see Arts, this volume). An organism without an energy storage
capacity is constantly dependent on energy flow from its food source for survival.
Any interruption in this flow will result in decreased condition and health of the
organism and possibly death. When energy is stored, the organism attains increased homeostatic capacity or stability, which allows it to survive periods of
interruption in its food supply (MacKinnon, 1972). Energy storage as a resource
allocation strategy represents a way of buying a degree of independence from the
environment (Reznick and Braun, 1987). By storing energy, individuals can establish a "savings account" to draw on when environmental resources are scarce.
Energy reserves, therefore, provide a means of ameliorating temporal mismatches
between food supply and energy demand (King and Murphy, 1985; Shul'man,
1974). When food is constantly available throughout the year, there is little energy
conservation advantage in adapting a cyclic feeding or storage strategy. In systems with large seasonal variations in food availability, however, cyclic feeding
and storage strategies have a definite energy conservation advantage.
The deposition and use of lipid reserves are important in the overall allocation
of energy in fish and thus have an ultimate function in the demography and life
S.M. Adams
ing of how food availability and lipid reserves ultimately dictate important life
processes such as overwinter survival and reproductive performance. For example, for the major economic and ecological species of concern, and particularly
those from temperate and north-temperate areas that experience seasonal pulses in
energy and environmental parameters, a better understanding is needed concerning the relationships between minimal levels of fat reserves and the probability of
overwinter survival and future reproductive success. In addition, the relationships
between fish food availability during the growing season, levels of lipid stores in
the late fall, and future year-class strength should be more clearly defined. Within
the context of food availability, knowledge of the temporal patterns in total lipids
and fatty acid composition of the major prey species would also be useful in
helping to predict overwinter survival and future reproductive success. Even
though they are more difficult to quantify, it is also important to identify densitydependent processes that are instrumental in optimizing lipid levels in fish during
the growing season for overwinter survival and reproductive success. For example, the relative importance of changes in competition for food through changes in
intraspecific and interspecific competition, the role of density-dependent breeding
and spawning behavior (which could extend or reduce the feeding and growing
period), and competition for preferred habitats for feeding, spawning, and shelter
are all important for maximizing the amount of available energy ultimately allocated to lipid storage. Understanding these relationships between environmental
factors, lipid reserves, survival, and reproductive success is key to effective management of fishery resources and for maximizing the future success of fishery
populations.
7.2.2. Energy Allocation Strategies
Many fish species display annual cycles in growth and lipid storage that are tightly
coupled to levels of ecosystem production, particularly lipid production in the
phytoplankton (see Arts, this volume). An organism without an energy storage
capacity is constantly dependent on energy flow from its food source for survival.
Any interruption in this flow will result in decreased condition and health of the
organism and possibly death. When energy is stored, the organism attains increased homeostatic capacity or stability, which allows it to survive periods of
interruption in its food supply (MacKinnon, 1972). Energy storage as a resource
allocation strategy represents a way of buying a degree of independence from the
environment (Reznick and Braun, 1987). By storing energy, individuals can establish a "savings account" to draw on when environmental resources are scarce.
Energy reserves, therefore, provide a means of ameliorating temporal mismatches
between food supply and energy demand (King and Murphy, 1985; Shul'man,
1974). When food is constantly available throughout the year, there is little energy
conservation advantage in adapting a cyclic feeding or storage strategy. In systems with large seasonal variations in food availability, however, cyclic feeding
and storage strategies have a definite energy conservation advantage.
The deposition and use of lipid reserves are important in the overall allocation
of energy in fish and thus have an ultimate function in the demography and life