120
P.L. Colin
A few aggregating species have benthic eggs (10 out of 169 “confi rmed” to
“possible” aggregating species – Appendix) with somewhat different reproductive
strategies but are not considered in detail in this chapter. For the rabbitfi shes
(Siganidae) our knowledge is rudimentary; some may only pair-spawn (PS) and not
all may have negatively buoyant adhesive eggs (Chap. 12.22 ). For the triggerfi shes
(Balistidae), which excavate nests in sandy areas with demersal (but not attached)
eggs, knowledge is still fragmentary (Chap. 12.23 ).
Much can be learned about spawning sites from the study of both TA and RA
sites, as well as from non-aggregating species (pair and haremic spawers) that may
spawn at or near aggregation sites. Nearly all known TA sites have multiple species
using them, either simultaneously or sequentially. TA sites are generally fewer in
number that RA sites in a given area, but whether this provides any relative advantage in promoting reproductive success is not known. Comparative studies between
TA, RA and non-aggregation sites may identify those elements (if any) found at TA
or RA sites that benefi t reproductive success. RA sites offer some advantages in
studying aggregations, being more numerous and often occurring over longer periods
of the year usually with spawning during daylight hours.
5.2 Stability of Aggregation Site Location
Long-term use of specifi c aggregation sites is found among reef fi shes throughout
the world. TEK for TAs indicates consistent occurrence for some at particular spots
over multiple human generations (Craig 1969 ; Johannes 1978, 1981 ; Sadovy de
Mitcheson et al. 2008 ) . For RAs, consistent use of sites is also documented for
periods from several years (Heyman et al. 2005 ; Colin 2010 ) to decades (Colin and
Clavijo 1978 ; Colin 1996 ) . Small year to year changes in locations (10s to a few
100s of meters) have been reported for some large TAs (Colin 1992 ; Whaylen et al.
2004 ; Kadison et al. 2006 ) , possibly resulting from “nomadic” (not tied to any
particular feature along a section of homogeneous reef) behaviour of fi sh (Kadison
et al. 2006 ) , temporary changes in current direction or confusion of “staging areas”,
occupied prior to spawning (Chap. 2 ), with the actual nearby site of spawning.
Highly accurate data on aggregation locations have been collected only over a
relatively short time-frame but continued monitoring of locations over the long-term
is important. Documentation of aggregation site locations and the area occupied
by the aggregation, determined by Global Positioning System (GPS), will allow
determination of whether sites are moving over time. Mapping of site features and
bathymetry relative to the overall aggregation is also a high priority (Chap. 9 ).
5.3 Location and Geomorphology of Sites
For most of the last 120,000 years sea-level has been signifi cantly lower than at
present, with its lowest (about −120 m) just 20,000 years ago, and arriving at today’s
level only a few thousand years ago (Paulay 1990 ) . When sea level was lower, what
P.L. Colin
A few aggregating species have benthic eggs (10 out of 169 “confi rmed” to
“possible” aggregating species – Appendix) with somewhat different reproductive
strategies but are not considered in detail in this chapter. For the rabbitfi shes
(Siganidae) our knowledge is rudimentary; some may only pair-spawn (PS) and not
all may have negatively buoyant adhesive eggs (Chap. 12.22 ). For the triggerfi shes
(Balistidae), which excavate nests in sandy areas with demersal (but not attached)
eggs, knowledge is still fragmentary (Chap. 12.23 ).
Much can be learned about spawning sites from the study of both TA and RA
sites, as well as from non-aggregating species (pair and haremic spawers) that may
spawn at or near aggregation sites. Nearly all known TA sites have multiple species
using them, either simultaneously or sequentially. TA sites are generally fewer in
number that RA sites in a given area, but whether this provides any relative advantage in promoting reproductive success is not known. Comparative studies between
TA, RA and non-aggregation sites may identify those elements (if any) found at TA
or RA sites that benefi t reproductive success. RA sites offer some advantages in
studying aggregations, being more numerous and often occurring over longer periods
of the year usually with spawning during daylight hours.
5.2 Stability of Aggregation Site Location
Long-term use of specifi c aggregation sites is found among reef fi shes throughout
the world. TEK for TAs indicates consistent occurrence for some at particular spots
over multiple human generations (Craig 1969 ; Johannes 1978, 1981 ; Sadovy de
Mitcheson et al. 2008 ) . For RAs, consistent use of sites is also documented for
periods from several years (Heyman et al. 2005 ; Colin 2010 ) to decades (Colin and
Clavijo 1978 ; Colin 1996 ) . Small year to year changes in locations (10s to a few
100s of meters) have been reported for some large TAs (Colin 1992 ; Whaylen et al.
2004 ; Kadison et al. 2006 ) , possibly resulting from “nomadic” (not tied to any
particular feature along a section of homogeneous reef) behaviour of fi sh (Kadison
et al. 2006 ) , temporary changes in current direction or confusion of “staging areas”,
occupied prior to spawning (Chap. 2 ), with the actual nearby site of spawning.
Highly accurate data on aggregation locations have been collected only over a
relatively short time-frame but continued monitoring of locations over the long-term
is important. Documentation of aggregation site locations and the area occupied
by the aggregation, determined by Global Positioning System (GPS), will allow
determination of whether sites are moving over time. Mapping of site features and
bathymetry relative to the overall aggregation is also a high priority (Chap. 9 ).
5.3 Location and Geomorphology of Sites
For most of the last 120,000 years sea-level has been signifi cantly lower than at
present, with its lowest (about −120 m) just 20,000 years ago, and arriving at today’s
level only a few thousand years ago (Paulay 1990 ) . When sea level was lower, what