200
P.L. Colin
migration prior to spawning. Groupers at transient aggregations are known to feed
between lunar spawning periods, perhaps to maintain nutritional fi tness and egg
quality (see Chap. 2 ).
Social factors, perhaps increasing the survival of transient spawned larvae, might
provide reasons for the evolution and maintenance of aggregating behaviour. If the
larvae of transient aggregators, whose individuals often go through long migrations
and elaborate preparations for spawning, are inherently superior compared to nonaggregating species, it might help explain why aggregation spawning has evolved in
such species. The “stage duration” hypothesis “that larvae that grow and develop
faster have higher survival and enhanced recruitment” (Leis and McCormick 2002 )
has support from studies of temperate and tropical species (Bergenius et al. 2002 ;
Sponaugle and Pinkard 2004 ; Sponaugle et al. 2006 ) . Studies of hormone and nutrition
levels in adult females and in ova produced, both during ovulation and after spawning,
are needed of both aggregating and non-aggregating species, perhaps from single
families, to test whether aggregating species show particular benefi ts.
7.4.3 Spawning and Gamete Release
While maternal condition may increase growth and survival, potential benefi ts at the
start of ELH may accrue from aggregation spawning when the environmental conditions are benefi cial to the larvae. This might involve release into patches of water
having specifi c properties conducive to larval survival (food in the form of zooplankton?), dispersal and retention. What little is known about the ocean dynamics
related to the release of large numbers of propagules into a limited volume of water
over short time periods was considered in Chap. 6 . Some information on the biologically mediated dynamics of aggregations (food, predation) is provided here.
The overall movements of fi shes engaged in the release of eggs and sperm in
“free-spawning” reef fi shes has been given various descriptive terms – rush, burst,
dash, ascent, spawning run – and is the start of the process of early life history. Fishes
present in aggregations spawn in three manners; as individual pairs (pair-spawn), as
small groups that briefl y break away from a larger aggregation (group-spawn), or in
a single group comprising most individuals in the aggregation (mass spawn).
Fertilization occurs quickly (within 1 min or so), unlike in many broadcast spawning
invertebrates, and in most cases the vent areas of males and females are in very close
proximity when gametes are released (Colin 2010 ) , presumably increasing egg-sperm
contact. Available data indicate that fertilization rates are generally quite high
(90–100%) for many pair- and group-spawning species (Kifl awi et al. 1998 ) . The
massive sperm clouds released by some transient spawners (such as Nassau grouper,
cubera snapper – Lutjanus cyanopterus and leopard grouper – M. rosacea ) and high
associated gonadosomatic indices of their males suggest in such cases that virtually
all healthy eggs get fertilized (Colin 1992 ; Sala et al. 2003 ; Heyman et al. 2005 ) .
This may not be the case for some smaller pair spawning reef fi shes (Petersen et al.
1992 ) and sperm limitation may occur (Petersen et al. 2001 ).
P.L. Colin
migration prior to spawning. Groupers at transient aggregations are known to feed
between lunar spawning periods, perhaps to maintain nutritional fi tness and egg
quality (see Chap. 2 ).
Social factors, perhaps increasing the survival of transient spawned larvae, might
provide reasons for the evolution and maintenance of aggregating behaviour. If the
larvae of transient aggregators, whose individuals often go through long migrations
and elaborate preparations for spawning, are inherently superior compared to nonaggregating species, it might help explain why aggregation spawning has evolved in
such species. The “stage duration” hypothesis “that larvae that grow and develop
faster have higher survival and enhanced recruitment” (Leis and McCormick 2002 )
has support from studies of temperate and tropical species (Bergenius et al. 2002 ;
Sponaugle and Pinkard 2004 ; Sponaugle et al. 2006 ) . Studies of hormone and nutrition
levels in adult females and in ova produced, both during ovulation and after spawning,
are needed of both aggregating and non-aggregating species, perhaps from single
families, to test whether aggregating species show particular benefi ts.
7.4.3 Spawning and Gamete Release
While maternal condition may increase growth and survival, potential benefi ts at the
start of ELH may accrue from aggregation spawning when the environmental conditions are benefi cial to the larvae. This might involve release into patches of water
having specifi c properties conducive to larval survival (food in the form of zooplankton?), dispersal and retention. What little is known about the ocean dynamics
related to the release of large numbers of propagules into a limited volume of water
over short time periods was considered in Chap. 6 . Some information on the biologically mediated dynamics of aggregations (food, predation) is provided here.
The overall movements of fi shes engaged in the release of eggs and sperm in
“free-spawning” reef fi shes has been given various descriptive terms – rush, burst,
dash, ascent, spawning run – and is the start of the process of early life history. Fishes
present in aggregations spawn in three manners; as individual pairs (pair-spawn), as
small groups that briefl y break away from a larger aggregation (group-spawn), or in
a single group comprising most individuals in the aggregation (mass spawn).
Fertilization occurs quickly (within 1 min or so), unlike in many broadcast spawning
invertebrates, and in most cases the vent areas of males and females are in very close
proximity when gametes are released (Colin 2010 ) , presumably increasing egg-sperm
contact. Available data indicate that fertilization rates are generally quite high
(90–100%) for many pair- and group-spawning species (Kifl awi et al. 1998 ) . The
massive sperm clouds released by some transient spawners (such as Nassau grouper,
cubera snapper – Lutjanus cyanopterus and leopard grouper – M. rosacea ) and high
associated gonadosomatic indices of their males suggest in such cases that virtually
all healthy eggs get fertilized (Colin 1992 ; Sala et al. 2003 ; Heyman et al. 2005 ) .
This may not be the case for some smaller pair spawning reef fi shes (Petersen et al.
1992 ) and sperm limitation may occur (Petersen et al. 2001 ).