199
7 Aggregation Spawning: Biological Aspects of the Early Life History
However, egg size differences may be uncorrelated with adult fi sh size and vary
geographically or seasonally. For spherical eggs, small differences in egg diameter
produce greater differences in egg volume which consists largely of yolk. A 26%
increase in diameter results in a doubling of egg, and presumably yolk, volume.
Some large reef fi shes have small eggs; the humphead wrasse, Cheilinus undulatus ,
and bumphead parrotfi sh, Bolbometopon muricatum , the largest members of their
families, have hydrated eggs averaging only 0.66 and 0.65 mm in diameter, respectively (Colin 2010 ; Bell and Colin 1986 ) . The Micronesian wrasse, Labropsis
micronesica , a non-aggregating wrasse reaching less than 100 mm SL, has a
0.80 mm diameter egg, twice the volume of a humphead wrasse egg. In the Atlantic
its largest wrasse, the hogfi sh Lachnolaimus maximus (a possible, but unverifi ed
aggregator), has eggs 1.2 mm in diameter (Colin 1983 ) while eggs of the bluehead
wrasse, Thalassoma bifasciatum (reaching about 150 mm SL), with dual spawning
modes, are about 0.56 mm in diameter (Holt and Riley 1999 ) . While the egg of the
hogfi sh is quite large, the eggs of most other Atlantic species seem similar to
comparable Pacifi c species (Richards 2006 ) .
For the eggs of a single species, the infl uence of maternal age and condition
may determine the quality of eggs and subsequent survival/growth of larvae. The
“provisioning” of larvae with energy-rich TAG lipids (found largely in the oil globule)
increased with female age in black rockfi sh, Sebastes melanops (Scorpaenidae), and
correlated with subsequent growth and survival (Berkeley et al. 2004 ) . For reef
fi shes the importance of egg quality is known for some damselfi shes with demersal
eggs (reviewed by Leis and McCormick 2002 ) , although little is known for those
with pelagic eggs. In damselfi shes maternal hormones and nutritional components
incorporated into egg yolk, the size of eggs and the size of larvae at hatch are affected
by feeding conditions of the female and behavioural interactions with conspecifi cs.
The larvae resulting from such “superior” eggs grow and develop faster reducing
time spent in the pelagic environment, thereby reducing the potential for mortality
of a cohort. It has been shown for species of surgeonfi sh (Bergenius et al. 2002 )
and wrasse (Grorud-Colvert and Sponaugle 2006 ) , both species with aggregation
spawning, that fast early growth can have positive effects on recruitment success.
The role of social factors in spawning aggregations (with the possible exception
of sex change) is unstudied. It is conceivable that aggregations provide abundant
opportunity for adults, particularly females, to be infl uenced by their interactions
with conspecifi cs through hormonal actions and increased “quality” of their eggs,
similar to the effect identifi ed in damselfi shes or through sexual selection and mate
choice (McCormick 1998, 1999a, b ; McCormick and Nechaev 2002 , Chap. 3 ). For
transient aggregators (TAs), who often have their reproduction limited to a few short
periods each year, if social interactions and hormonal effects can improve “quality”
of eggs produced, their relatively short spawning season may also help to maintain
egg size and quality (as opposed to long spawning seasons when egg quality may
decline over time, Leis and McCormick 2002 ) . It would be important to know if the
nutritional fi tness of the ova is determined by feeding activities prior to any migration, which might take several days during which feeding may not occur, to evaluate
the benefi ts to egg quality when a transient aggregator then undertakes a signifi cant
7 Aggregation Spawning: Biological Aspects of the Early Life History
However, egg size differences may be uncorrelated with adult fi sh size and vary
geographically or seasonally. For spherical eggs, small differences in egg diameter
produce greater differences in egg volume which consists largely of yolk. A 26%
increase in diameter results in a doubling of egg, and presumably yolk, volume.
Some large reef fi shes have small eggs; the humphead wrasse, Cheilinus undulatus ,
and bumphead parrotfi sh, Bolbometopon muricatum , the largest members of their
families, have hydrated eggs averaging only 0.66 and 0.65 mm in diameter, respectively (Colin 2010 ; Bell and Colin 1986 ) . The Micronesian wrasse, Labropsis
micronesica , a non-aggregating wrasse reaching less than 100 mm SL, has a
0.80 mm diameter egg, twice the volume of a humphead wrasse egg. In the Atlantic
its largest wrasse, the hogfi sh Lachnolaimus maximus (a possible, but unverifi ed
aggregator), has eggs 1.2 mm in diameter (Colin 1983 ) while eggs of the bluehead
wrasse, Thalassoma bifasciatum (reaching about 150 mm SL), with dual spawning
modes, are about 0.56 mm in diameter (Holt and Riley 1999 ) . While the egg of the
hogfi sh is quite large, the eggs of most other Atlantic species seem similar to
comparable Pacifi c species (Richards 2006 ) .
For the eggs of a single species, the infl uence of maternal age and condition
may determine the quality of eggs and subsequent survival/growth of larvae. The
“provisioning” of larvae with energy-rich TAG lipids (found largely in the oil globule)
increased with female age in black rockfi sh, Sebastes melanops (Scorpaenidae), and
correlated with subsequent growth and survival (Berkeley et al. 2004 ) . For reef
fi shes the importance of egg quality is known for some damselfi shes with demersal
eggs (reviewed by Leis and McCormick 2002 ) , although little is known for those
with pelagic eggs. In damselfi shes maternal hormones and nutritional components
incorporated into egg yolk, the size of eggs and the size of larvae at hatch are affected
by feeding conditions of the female and behavioural interactions with conspecifi cs.
The larvae resulting from such “superior” eggs grow and develop faster reducing
time spent in the pelagic environment, thereby reducing the potential for mortality
of a cohort. It has been shown for species of surgeonfi sh (Bergenius et al. 2002 )
and wrasse (Grorud-Colvert and Sponaugle 2006 ) , both species with aggregation
spawning, that fast early growth can have positive effects on recruitment success.
The role of social factors in spawning aggregations (with the possible exception
of sex change) is unstudied. It is conceivable that aggregations provide abundant
opportunity for adults, particularly females, to be infl uenced by their interactions
with conspecifi cs through hormonal actions and increased “quality” of their eggs,
similar to the effect identifi ed in damselfi shes or through sexual selection and mate
choice (McCormick 1998, 1999a, b ; McCormick and Nechaev 2002 , Chap. 3 ). For
transient aggregators (TAs), who often have their reproduction limited to a few short
periods each year, if social interactions and hormonal effects can improve “quality”
of eggs produced, their relatively short spawning season may also help to maintain
egg size and quality (as opposed to long spawning seasons when egg quality may
decline over time, Leis and McCormick 2002 ) . It would be important to know if the
nutritional fi tness of the ova is determined by feeding activities prior to any migration, which might take several days during which feeding may not occur, to evaluate
the benefi ts to egg quality when a transient aggregator then undertakes a signifi cant