119
5 Timing and Location of Aggregation and Spawning in Reef Fishes
Subsequently in this chapter the following abbreviations will be used: tropical western
Atlantic (TWA), tropical Indo-west Pacifi c (IWP) and eastern Pacifi c (EP). The
TWA includes both the North Atlantic (Caribbean, Gulf of Mexico, Bahamas-Turks
and Caicos archipelago, US east coast and Bermuda), and South Atlantic (Brazil and
Atlantic Islands). The IWP includes the islands of the central and western North and
South Pacifi c, much of Southeast Asia, the tropical Indian Ocean to the east coast of
Africa and the Red Sea.
If there is a single, or even a few, overriding reason(s) for the location and timing
of spawning, it is likely scientists would have identifi ed it (them) by now. For every
generality or hypothesis put forward about spawning aggregations, there is some
example that argues exactly the opposite. Also, what occurs in one location does not
necessarily follow in another and the potential for unknown fl exibility in spawning
ecology is always present. Most studies have tended to focus on one or at most a few
sites, and often put forward generalities based on those locations. While documenting and analyzing what happens at individual sites is necessary and important, it
may not provide answers to the overall questions of benefi ts or limitations of sites.
The locations and timing of aggregations are not necessarily “adaptive” for reproductive success at all times (Chaps. 1, 2, 4 ). Use of a site may promote success some
of the time while another site may be advantageous at other times (Colin 1995 ) .
While we have a limited ability to monitor the numbers of fi sh present and occasionally their success in spawning, scientists are usually unable to determine whether
such spawning actually results in life history success through to the settlement
stage, and beyond.
Most likely the factors infl uencing spawning aggregations will be an amalgam
combining aspects of the oceanographic and atmospheric environments (currents,
topography, seasonal temperature, salinity and weather) with the biological (species
specifi c needs with regard to feeding, social structure, predation, physiology and
genetics of larval and juvenile-adult stages) (Chap. 4 ). Also part of the mix are historical aspects of reef ecology and geomorphology as reef environments have shifted
from steep escarpments to broad reef expanses in the last 20,000 years since the
start of the Holocene transgression (Paulay 1990 ) .
The known scope and patterns of the “where and when” of aggregation spawning
reveal a wide diversity of strategies. Species and behaviour range from small resident aggregation (RA) species, typifi ed by Thalassoma bifasciatum, the bluehead
wrasse in the TWA and a variety of small wrasses (Labridae) and parrotfi sh
(Scaridae) in the IWP, to large transient aggregation (TA) species, which reach their
epitome in the TWA with Epinephelus striatus , the Nassau grouper and Lutjanus
cyanopterus , the cubera snapper (Chap. 1 ). While not as well known as these TWA
species, new knowledge indicates some IWP snappers (Labridae) (e.g. blackfi n
snapper – Lutjanus fulvus and blue-lined sea bream – Symphorichthys spilurus –
Chaps . 12.10 and 12.11 ) have large TA’s comparable to those of the TWA, but more
information on reproductive status through specimen collection is needed. Those
IWP groupers with documented aggregations tend to have many (to multiple 1,000s)
individuals spread over a relatively broad area at densities lower than those found in
some TWA groupers (PLC unpublished data, Figs. 2.6, 9.1, 9.9).
5 Timing and Location of Aggregation and Spawning in Reef Fishes
Subsequently in this chapter the following abbreviations will be used: tropical western
Atlantic (TWA), tropical Indo-west Pacifi c (IWP) and eastern Pacifi c (EP). The
TWA includes both the North Atlantic (Caribbean, Gulf of Mexico, Bahamas-Turks
and Caicos archipelago, US east coast and Bermuda), and South Atlantic (Brazil and
Atlantic Islands). The IWP includes the islands of the central and western North and
South Pacifi c, much of Southeast Asia, the tropical Indian Ocean to the east coast of
Africa and the Red Sea.
If there is a single, or even a few, overriding reason(s) for the location and timing
of spawning, it is likely scientists would have identifi ed it (them) by now. For every
generality or hypothesis put forward about spawning aggregations, there is some
example that argues exactly the opposite. Also, what occurs in one location does not
necessarily follow in another and the potential for unknown fl exibility in spawning
ecology is always present. Most studies have tended to focus on one or at most a few
sites, and often put forward generalities based on those locations. While documenting and analyzing what happens at individual sites is necessary and important, it
may not provide answers to the overall questions of benefi ts or limitations of sites.
The locations and timing of aggregations are not necessarily “adaptive” for reproductive success at all times (Chaps. 1, 2, 4 ). Use of a site may promote success some
of the time while another site may be advantageous at other times (Colin 1995 ) .
While we have a limited ability to monitor the numbers of fi sh present and occasionally their success in spawning, scientists are usually unable to determine whether
such spawning actually results in life history success through to the settlement
stage, and beyond.
Most likely the factors infl uencing spawning aggregations will be an amalgam
combining aspects of the oceanographic and atmospheric environments (currents,
topography, seasonal temperature, salinity and weather) with the biological (species
specifi c needs with regard to feeding, social structure, predation, physiology and
genetics of larval and juvenile-adult stages) (Chap. 4 ). Also part of the mix are historical aspects of reef ecology and geomorphology as reef environments have shifted
from steep escarpments to broad reef expanses in the last 20,000 years since the
start of the Holocene transgression (Paulay 1990 ) .
The known scope and patterns of the “where and when” of aggregation spawning
reveal a wide diversity of strategies. Species and behaviour range from small resident aggregation (RA) species, typifi ed by Thalassoma bifasciatum, the bluehead
wrasse in the TWA and a variety of small wrasses (Labridae) and parrotfi sh
(Scaridae) in the IWP, to large transient aggregation (TA) species, which reach their
epitome in the TWA with Epinephelus striatus , the Nassau grouper and Lutjanus
cyanopterus , the cubera snapper (Chap. 1 ). While not as well known as these TWA
species, new knowledge indicates some IWP snappers (Labridae) (e.g. blackfi n
snapper – Lutjanus fulvus and blue-lined sea bream – Symphorichthys spilurus –
Chaps . 12.10 and 12.11 ) have large TA’s comparable to those of the TWA, but more
information on reproductive status through specimen collection is needed. Those
IWP groupers with documented aggregations tend to have many (to multiple 1,000s)
individuals spread over a relatively broad area at densities lower than those found in
some TWA groupers (PLC unpublished data, Figs. 2.6, 9.1, 9.9).