106
J.H. Choat
fronts, passes or promontories (Sadovy de Mitcheson et al. 2008 ; Colin 2010a ) .
Secondly, many of these sites are infl uenced by oceanic current systems, especially
in the western Atlantic (Heyman and Kjerfve 2008 ) , or by outward fl owing tidal
currents in the Indo-Pacifi c (Colin 2010a , Chap. 6 ). Thirdly, both types of current
systems have the capacity to move propagules away from the immediate spawning
site and in some cases entrain them into eddies adjacent to the reef but retain them
in an open water environment beyond the predatory fi eld. It is also noteworthy that
many of the larger species that produce abundant propagules appear to spawn at
dusk or nocturnally which would reduce mortality from visual predators (Colin
1992 ; Samoilys 1997 ; Heyman and Kjerfve 2008 ) .
Teleost fi shes experience exceptionally high mortality rates in the larval and
juvenile phases, approximately fi ve times those experienced by terrestrial groups
(Perez and Munch 2010 ) . Although mortality decreases with increase in age and
size, only ~0.01–0.1 fi sh in a given cohort survive the fi rst year of life (Claisse et al.
2009 ; Perez and Munch 2010 ) . Reduction in the initial mortality rate would occur if
propagules moved rapidly through the predatory fi eld adjacent to the reef and into
an open pelagic environment. Any tendency to ensure pelagic propagules passed
rapidly beyond the near-reef predatory fi eld would be favoured by selection.
Larval retention and return of propagules to a natal reef will benefi t groups of
reef fi shes with specialized habitat requirements (Swearer et al. 2002 ; Almany et al.
2007 ; Jones et al. 2009 ) . A successful parental generation indicates that they occupy
an appropriate habitat for the next generation of recruits. While retention may benefi t
such species the case for those with wide distributions and general habitat requirements, including the four groups that dominate aggregate spawning, is less clear.
Retention and self recruitment may only be one of a range of dispersal strategies seen
in reef fi shes as a number of species consistently exhibit very wide dispersal of
larvae (Craig et al. 2007 ; Horne et al. 2008 ; Gaither et al. 2010 ) . Similar arguments
are made in the case of widely distributed tropical gastropods with differing levels
of stability in habitats occupied by adults (Crandall et al. 2010 ) . The case for wide
dispersal in a number of reef fi sh groups is strengthened by two sorts of observations. Firstly, many reef species with a supposedly short planktonic larval duration
can disperse over very wide distances including the East Pacifi c Barrier (Lessios
and Robertson 2006 ) . Secondly, transport into open-ocean and nutrient-poor larval
environments does not mean that these larvae are disadvantaged relative to those
retained in local nutrient rich waters. Although larval growth during the pelagic
phase may be reduced, compensatory growth prior to settlement and relatively high
survival compared to those retained in near-shore environments have been recorded
(Hamilton et al. 2008 b ) . The case for larval retention as a major reason for the
development of spawning aggregations is not supported by the evidence of larval
biology and phylogeography (see also Chaps. 6 and 7 ).
Although resident and transient spawners rely on advection to enhance egg survival they have different temporal patterns of spawning. This raises the question as to
how the costs of reproduction are met in the two groups. The alternatives are capital
breeding and income breeding (reliance on concurrent intake) (Warner 1995 ; Stephens
et al. 2009 ) . Income breeding in which daily reproduction is directly subsidized by
J.H. Choat
fronts, passes or promontories (Sadovy de Mitcheson et al. 2008 ; Colin 2010a ) .
Secondly, many of these sites are infl uenced by oceanic current systems, especially
in the western Atlantic (Heyman and Kjerfve 2008 ) , or by outward fl owing tidal
currents in the Indo-Pacifi c (Colin 2010a , Chap. 6 ). Thirdly, both types of current
systems have the capacity to move propagules away from the immediate spawning
site and in some cases entrain them into eddies adjacent to the reef but retain them
in an open water environment beyond the predatory fi eld. It is also noteworthy that
many of the larger species that produce abundant propagules appear to spawn at
dusk or nocturnally which would reduce mortality from visual predators (Colin
1992 ; Samoilys 1997 ; Heyman and Kjerfve 2008 ) .
Teleost fi shes experience exceptionally high mortality rates in the larval and
juvenile phases, approximately fi ve times those experienced by terrestrial groups
(Perez and Munch 2010 ) . Although mortality decreases with increase in age and
size, only ~0.01–0.1 fi sh in a given cohort survive the fi rst year of life (Claisse et al.
2009 ; Perez and Munch 2010 ) . Reduction in the initial mortality rate would occur if
propagules moved rapidly through the predatory fi eld adjacent to the reef and into
an open pelagic environment. Any tendency to ensure pelagic propagules passed
rapidly beyond the near-reef predatory fi eld would be favoured by selection.
Larval retention and return of propagules to a natal reef will benefi t groups of
reef fi shes with specialized habitat requirements (Swearer et al. 2002 ; Almany et al.
2007 ; Jones et al. 2009 ) . A successful parental generation indicates that they occupy
an appropriate habitat for the next generation of recruits. While retention may benefi t
such species the case for those with wide distributions and general habitat requirements, including the four groups that dominate aggregate spawning, is less clear.
Retention and self recruitment may only be one of a range of dispersal strategies seen
in reef fi shes as a number of species consistently exhibit very wide dispersal of
larvae (Craig et al. 2007 ; Horne et al. 2008 ; Gaither et al. 2010 ) . Similar arguments
are made in the case of widely distributed tropical gastropods with differing levels
of stability in habitats occupied by adults (Crandall et al. 2010 ) . The case for wide
dispersal in a number of reef fi sh groups is strengthened by two sorts of observations. Firstly, many reef species with a supposedly short planktonic larval duration
can disperse over very wide distances including the East Pacifi c Barrier (Lessios
and Robertson 2006 ) . Secondly, transport into open-ocean and nutrient-poor larval
environments does not mean that these larvae are disadvantaged relative to those
retained in local nutrient rich waters. Although larval growth during the pelagic
phase may be reduced, compensatory growth prior to settlement and relatively high
survival compared to those retained in near-shore environments have been recorded
(Hamilton et al. 2008 b ) . The case for larval retention as a major reason for the
development of spawning aggregations is not supported by the evidence of larval
biology and phylogeography (see also Chaps. 6 and 7 ).
Although resident and transient spawners rely on advection to enhance egg survival they have different temporal patterns of spawning. This raises the question as to
how the costs of reproduction are met in the two groups. The alternatives are capital
breeding and income breeding (reliance on concurrent intake) (Warner 1995 ; Stephens
et al. 2009 ) . Income breeding in which daily reproduction is directly subsidized by