146
S.M. Adams
structure offish populations (Fig. 7.2). In many species, lipids that are built up and
stored in various compartments of the body are used over the winter and early
spring for basic maintenance needs and for gonadal development. Numerous
studies have shown that fish that fail to build up adequate lipid reserves before
winter generally experience some level of reproductive failure the following
spring. Because the quality of eggs is related to lipid quantity, the success of the
hatched larvae is a size-dependent phenomenon also related to maternal lipid
availability. Larger larvae hatched from larger eggs generally experience higher
survival and success because of enhanced feeding ability, decreased vulnerability
to predation, and a longer period of subsistence on endogenous energy before
exogenous resources become available. Relatively small differences in larval size
at the time of hatch may ultimately translate into substantial differences at the
population level in regards to long-term survival and success of the population.
Successful reproductive performance is intricately linked to the availability of
lipid reserves for gonadal development. Several studies have documented that the
health and level of lipid depots in the adult female in the fall prior to the overwinter nonfeeding period is a key indicator of reproductive success the following
spring. Related to this, studies are needed to better establish, for important economic and ecological species, the relationship between minimum or critical lipid
levels in the maternal parent and the ultimate effect of these levels on gonad
development, egg quality, and larval hatching success and survival. In addition,
the environmental factors that can affect the health and condition of the adult for
the period preceding the cessation of feeding and initiation of gonadal development should also be studied. For example, much is known about striped bass and
how environmental conditions in certain aquatic systems can place various
stresses on the adults, causing loss of body condition including reduced storage of
lipids. By understanding the dynamics of physicochemical factors, such as temperature and dissolved oxygen, and processes within the food chain that can have
negative impacts on adults, fishery stocks can be better managed to achieve higher
reproductive and population success.
7.2.4. Lipids and Environmental Stress
Exposure to environmental stressors is an inescapable aspect of an aquatic organism's life. Fluctuating thermal and hydrological regimes, pH, oxygen, siltation,
and contaminants impose constraints on the ability of an organism to cope with its
environment (Dehn and Schirf, 1986). Most aquatic species are adapted to their
environment, but this adaptation does not imply an absence of energetic expenditure to maintain homeostasis in the face of sublethal environmental stressors
(Wedemeyer et aI., 1984).
Environmental stressors first initiate the primary stress response system by
affecting biomolecular, biochemical, and physiological processes (Fig. 7.2).
These primary stress responses may be followed by secondary stress responses in
which alterations in energy allocation and metabolism occur (Leatherland and
Sonstegard, 1984; Mazeaud and Mazeaud, 1981), including changes in lipids,
S.M. Adams
structure offish populations (Fig. 7.2). In many species, lipids that are built up and
stored in various compartments of the body are used over the winter and early
spring for basic maintenance needs and for gonadal development. Numerous
studies have shown that fish that fail to build up adequate lipid reserves before
winter generally experience some level of reproductive failure the following
spring. Because the quality of eggs is related to lipid quantity, the success of the
hatched larvae is a size-dependent phenomenon also related to maternal lipid
availability. Larger larvae hatched from larger eggs generally experience higher
survival and success because of enhanced feeding ability, decreased vulnerability
to predation, and a longer period of subsistence on endogenous energy before
exogenous resources become available. Relatively small differences in larval size
at the time of hatch may ultimately translate into substantial differences at the
population level in regards to long-term survival and success of the population.
Successful reproductive performance is intricately linked to the availability of
lipid reserves for gonadal development. Several studies have documented that the
health and level of lipid depots in the adult female in the fall prior to the overwinter nonfeeding period is a key indicator of reproductive success the following
spring. Related to this, studies are needed to better establish, for important economic and ecological species, the relationship between minimum or critical lipid
levels in the maternal parent and the ultimate effect of these levels on gonad
development, egg quality, and larval hatching success and survival. In addition,
the environmental factors that can affect the health and condition of the adult for
the period preceding the cessation of feeding and initiation of gonadal development should also be studied. For example, much is known about striped bass and
how environmental conditions in certain aquatic systems can place various
stresses on the adults, causing loss of body condition including reduced storage of
lipids. By understanding the dynamics of physicochemical factors, such as temperature and dissolved oxygen, and processes within the food chain that can have
negative impacts on adults, fishery stocks can be better managed to achieve higher
reproductive and population success.
7.2.4. Lipids and Environmental Stress
Exposure to environmental stressors is an inescapable aspect of an aquatic organism's life. Fluctuating thermal and hydrological regimes, pH, oxygen, siltation,
and contaminants impose constraints on the ability of an organism to cope with its
environment (Dehn and Schirf, 1986). Most aquatic species are adapted to their
environment, but this adaptation does not imply an absence of energetic expenditure to maintain homeostasis in the face of sublethal environmental stressors
(Wedemeyer et aI., 1984).
Environmental stressors first initiate the primary stress response system by
affecting biomolecular, biochemical, and physiological processes (Fig. 7.2).
These primary stress responses may be followed by secondary stress responses in
which alterations in energy allocation and metabolism occur (Leatherland and
Sonstegard, 1984; Mazeaud and Mazeaud, 1981), including changes in lipids,