144
S.M. Adams
Docker et aI., 1986). When external food is scarce, larger larvae from larger eggs
survive longer than those hatched from smaller eggs (Ware, 1975). Higher survival of these individuals resulting from larger eggs has been noted, particularly
for several salmonid species (Gall, 1974). A positive relationship between
viability of offspring and total lipid concentration in the eggs has been demonstrated for a number of species (Brown and Taylor, 1992; Kamler, 1992; Thorpe et
al.. 1984). Eggs characterized by higher lipid content tend to produce larger
larvae, which provides the larvae with several survival advantages (Kamler, 1992;
Thorpe et aI., 1984). Higher lipid reserves in the maternal parent and the eggs
improve the ability of larvae to delay initial feeding for longer periods than larvae
with less energy resources (Brown and Taylor, 1992), with larger larvae having
more energy reserves for seeking and capturing prey.
Body size, which is based on endogenous energy available from the egg, is an
important variable also influencing the physiology, ecology, and behavior of
larval fish (Miller et aI., 1988). Mechanisms that regulate larval success and
growth operate in a size-dependent fashion. For example, body size influences the
vulnerability of larval fish to predation through differential encounter rates and
predator escape abilities. Also, the ability of larger larvae to successfully feed is
enhanced because they have longer reaction distances to prey and increased
swimming abilities. Swimming performance also influences the ability of larval
fish to maintain their position in optimal areas for growth and survival (Brown and
Taylor, 1992). Before feeding occurred, Knutsen and Tilseth (1985) demonstrated
that mouth gape size was correlated to egg size. Therefore, the importance of
larval size to feeding is that a broader spectra of prey sizes are available to the
larger larvae compared with smaller individuals.
Relatively small differences in larval size at the time of hatch may translate into
substantial differences at the population level in regard to long-term survival,
subsequent recruitment, and year-class strength (Adams and DeAngelis, 1987).
Fish that incur very small size advantages early in their life history proportionally
increase their probability of survival because of slight advantages in foraging and
swimming abilities. escape from predators, and maximization of the period between depletion of endogenous energy stores and feeding. This later point becomes particularly important if the production of food resources is mismatched in
time with the initiation of larval feeding.
The trade-offs between number and size of offspring is an important factor
determining reproductive potential (Pepin and Myers, 1991). Properties of larvae
as related to egg size have counterbalancing advantages, however, depending on
the reproductive strategy employed (Kamler, 1992). In species with r strategies
(i.e., those that produce many small eggs) from the total biomass of eggs in the
ovary, a larger number of smaller individuals develop that use food resources
more efficiently and exhibit a high potential for rapid growth. In species with a k
strategy (i.e., those that produce a few large eggs), fewer but larger larvae are
produced, and their larger size increases their chances of survival because the risk
of predation is reduced (Miller et al.. 1988) and their prey capture and foraging
S.M. Adams
Docker et aI., 1986). When external food is scarce, larger larvae from larger eggs
survive longer than those hatched from smaller eggs (Ware, 1975). Higher survival of these individuals resulting from larger eggs has been noted, particularly
for several salmonid species (Gall, 1974). A positive relationship between
viability of offspring and total lipid concentration in the eggs has been demonstrated for a number of species (Brown and Taylor, 1992; Kamler, 1992; Thorpe et
al.. 1984). Eggs characterized by higher lipid content tend to produce larger
larvae, which provides the larvae with several survival advantages (Kamler, 1992;
Thorpe et aI., 1984). Higher lipid reserves in the maternal parent and the eggs
improve the ability of larvae to delay initial feeding for longer periods than larvae
with less energy resources (Brown and Taylor, 1992), with larger larvae having
more energy reserves for seeking and capturing prey.
Body size, which is based on endogenous energy available from the egg, is an
important variable also influencing the physiology, ecology, and behavior of
larval fish (Miller et aI., 1988). Mechanisms that regulate larval success and
growth operate in a size-dependent fashion. For example, body size influences the
vulnerability of larval fish to predation through differential encounter rates and
predator escape abilities. Also, the ability of larger larvae to successfully feed is
enhanced because they have longer reaction distances to prey and increased
swimming abilities. Swimming performance also influences the ability of larval
fish to maintain their position in optimal areas for growth and survival (Brown and
Taylor, 1992). Before feeding occurred, Knutsen and Tilseth (1985) demonstrated
that mouth gape size was correlated to egg size. Therefore, the importance of
larval size to feeding is that a broader spectra of prey sizes are available to the
larger larvae compared with smaller individuals.
Relatively small differences in larval size at the time of hatch may translate into
substantial differences at the population level in regard to long-term survival,
subsequent recruitment, and year-class strength (Adams and DeAngelis, 1987).
Fish that incur very small size advantages early in their life history proportionally
increase their probability of survival because of slight advantages in foraging and
swimming abilities. escape from predators, and maximization of the period between depletion of endogenous energy stores and feeding. This later point becomes particularly important if the production of food resources is mismatched in
time with the initiation of larval feeding.
The trade-offs between number and size of offspring is an important factor
determining reproductive potential (Pepin and Myers, 1991). Properties of larvae
as related to egg size have counterbalancing advantages, however, depending on
the reproductive strategy employed (Kamler, 1992). In species with r strategies
(i.e., those that produce many small eggs) from the total biomass of eggs in the
ovary, a larger number of smaller individuals develop that use food resources
more efficiently and exhibit a high potential for rapid growth. In species with a k
strategy (i.e., those that produce a few large eggs), fewer but larger larvae are
produced, and their larger size increases their chances of survival because the risk
of predation is reduced (Miller et al.. 1988) and their prey capture and foraging