504
12 Species Case Studies
Colin ( 1978 ) documented differences in spawning activity between winter and
summer periods in Jamaica, as well as the afternoon spawning of the species.
Pair-spawning occurs from early to late in the day. Striped parrotfi sh can occur in
schools during its morning foraging activities, using the large numbers of fi sh
combined with smaller numbers of some other species to overwhelm herbivorous
territorial damselfi shes that maintain algal “farms” (Robertson et al. 1976 ) . The
damselfi sh can only drive off a few fi sh, while the remainder graze aggressively at
the exposed food patch. This behaviour, known as “mobbing”, is also seen in the
IWP greenthroat parrotfi sh, Scarus prasiognathos , which works with surgeonfi shes
such as Acanthurus blochii , to the same end.
In the striped parrotfi sh, it appears the same schools that overwhelm the damselfi shes remain cohesive and form a spawning aggregation each afternoon. In late
afternoon striped parrotfi sh aggregated over a reef pinnacle (the highest point among
nearby reef fi ngers) on the edge of a drop off. They engaged in group-spawning
(Fig. 12.48 ) for about an hour starting about 90 min before sunset (Colin 1978 ) . A
single terminal phase male was also at the site, trying to get females interested in
spawning with him (largely in vain). The striped parrotfi sh spawning aggregation
investigated in 1975 (Colin 1978 ) was still present in 1988 (Colin 1996 ) , but its
present status is not known. In Puerto Rico Colin and Clavijo ( 1988 ) had an aggregation of about 100 fi sh in a study area on a shelf edge coral reef. The fi sh spawned
as groups emerging from the aggregation in late afternoon, actively during the winter but at a lower level during summer. Their aggregation site was close to, but
slightly different than that of two species of Acanthurus . Again pair-spawning with
a terminal male also occurred in the area at the same time.
Bullethead parrotfi sh normally aggregate and spawn on a tidal schedule, typically just after high tide where there is a distinct tidal signal (Yogo et al. 1980 ;
Moyer 1989 ; Kuwamura et al. 2009 ) . It often has the highest number of observed
spawns of any reef fi sh (Sancho et al. 2000a, b ; Kuwamura et al. ( 2009 ) . In some
areas the local currents, generated by winds or wave pumping, may be out of phase
with the tidal amplitude, and the fi shes seem to use the currents rather than absolute
tide level to cue spawning (Sancho et al. 2000a ) . In most locations the species
spawns when high tide is during morning periods (Hamner et al. 2007 ; Kuwamura
et al. 2009 ; PLC unpublished data).
At Johnston Atoll, where currents in channels did not often correspond to tide
levels, Sancho et al. ( 2000a ) reported that bullethead parrotfi sh avoided spawning
on infl owing currents (ocean to lagoon) at a tidal channel, delaying spawning until
currents reversed to outfl owing. If currents reversed again, fl owing into the lagoon,
the fi sh interrupted their ongoing spawning. Sancho et al. ( 2000a ) also found some
differences in the spawning behaviour with currents in two different study sites at
Johnston Atoll. This indicates that a specifi c tidal phase is not used as a fi xed environmental cue across the geographic range of this species, but that fi sh are responding to directional water fl ows. Meyer et al. ( 2010 ) observed a school of roughly 800
bullethead parrotfi sh at the surface over 20–40 m depths in mid-day in the NW
Hawaiian islands, but based on the known spawning behaviour of this fi sh, this
appears not to be a spawning aggregation and is most likely a migration between
feeding areas. The suggestion of this schooling as an example of a “spawning
12 Species Case Studies
Colin ( 1978 ) documented differences in spawning activity between winter and
summer periods in Jamaica, as well as the afternoon spawning of the species.
Pair-spawning occurs from early to late in the day. Striped parrotfi sh can occur in
schools during its morning foraging activities, using the large numbers of fi sh
combined with smaller numbers of some other species to overwhelm herbivorous
territorial damselfi shes that maintain algal “farms” (Robertson et al. 1976 ) . The
damselfi sh can only drive off a few fi sh, while the remainder graze aggressively at
the exposed food patch. This behaviour, known as “mobbing”, is also seen in the
IWP greenthroat parrotfi sh, Scarus prasiognathos , which works with surgeonfi shes
such as Acanthurus blochii , to the same end.
In the striped parrotfi sh, it appears the same schools that overwhelm the damselfi shes remain cohesive and form a spawning aggregation each afternoon. In late
afternoon striped parrotfi sh aggregated over a reef pinnacle (the highest point among
nearby reef fi ngers) on the edge of a drop off. They engaged in group-spawning
(Fig. 12.48 ) for about an hour starting about 90 min before sunset (Colin 1978 ) . A
single terminal phase male was also at the site, trying to get females interested in
spawning with him (largely in vain). The striped parrotfi sh spawning aggregation
investigated in 1975 (Colin 1978 ) was still present in 1988 (Colin 1996 ) , but its
present status is not known. In Puerto Rico Colin and Clavijo ( 1988 ) had an aggregation of about 100 fi sh in a study area on a shelf edge coral reef. The fi sh spawned
as groups emerging from the aggregation in late afternoon, actively during the winter but at a lower level during summer. Their aggregation site was close to, but
slightly different than that of two species of Acanthurus . Again pair-spawning with
a terminal male also occurred in the area at the same time.
Bullethead parrotfi sh normally aggregate and spawn on a tidal schedule, typically just after high tide where there is a distinct tidal signal (Yogo et al. 1980 ;
Moyer 1989 ; Kuwamura et al. 2009 ) . It often has the highest number of observed
spawns of any reef fi sh (Sancho et al. 2000a, b ; Kuwamura et al. ( 2009 ) . In some
areas the local currents, generated by winds or wave pumping, may be out of phase
with the tidal amplitude, and the fi shes seem to use the currents rather than absolute
tide level to cue spawning (Sancho et al. 2000a ) . In most locations the species
spawns when high tide is during morning periods (Hamner et al. 2007 ; Kuwamura
et al. 2009 ; PLC unpublished data).
At Johnston Atoll, where currents in channels did not often correspond to tide
levels, Sancho et al. ( 2000a ) reported that bullethead parrotfi sh avoided spawning
on infl owing currents (ocean to lagoon) at a tidal channel, delaying spawning until
currents reversed to outfl owing. If currents reversed again, fl owing into the lagoon,
the fi sh interrupted their ongoing spawning. Sancho et al. ( 2000a ) also found some
differences in the spawning behaviour with currents in two different study sites at
Johnston Atoll. This indicates that a specifi c tidal phase is not used as a fi xed environmental cue across the geographic range of this species, but that fi sh are responding to directional water fl ows. Meyer et al. ( 2010 ) observed a school of roughly 800
bullethead parrotfi sh at the surface over 20–40 m depths in mid-day in the NW
Hawaiian islands, but based on the known spawning behaviour of this fi sh, this
appears not to be a spawning aggregation and is most likely a migration between
feeding areas. The suggestion of this schooling as an example of a “spawning