146
P.L. Colin
Islands – Kadison et al. 2006 –, Little Cayman Island – Whaylen et al. 2004 ; Belize
– Heyman et al. 2005 ) and similar timing occurs for Nassau groupers, red hind, and
yellowfi n groupers, Mycteroperca venenosa .
Data are less available for the IWP, but the seasonal extent of TAs may be longer and
different than the TWA. The blackfi n snapper, Lutjanus fulvus , has been documented to
aggregate nearly every month of the year in Palau (Chap. 12.10 ) and there are reports
from traditional knowledge of TAs occurring year round, particularly in groupers
(Hamilton et al. 2005 ) e.g. squaretail coralgrouper (Chap. 12.8 ). It would be interesting
to know if the relatively limited annual water temperature ranges in equatorial locations
might account for reported variation in aggregation seasonality. TEK from Melanesia
indicates some groupers have year-round aggregations in some areas while others had
seasons limited to 3–4 months, varying between localities (Hamilton et al. 2005 ) .
Validating differences in patterns of aggregation timing and of fi sh numbers is not
simple. Often the timing and fi sh number peaks of aggregation for any month and over
fairly long seasonal periods are not easily documented (Chap. 9 ). Peak fi sh numbers
in an aggregation may occur for only 1 day during a lunar month, and not necessarily
on the same day of the lunar cycle each year, with surveys on days either side of the
peak having dramatic decreases in fi sh numbers. Unless surveys cover several days in
a row, the peak period may be missed and a sub-peak day mistakenly assumed to
represent the peak fi sh numbers (e.g. Fig. 12.77). The diversity of methods employed
to gather data on numbers of fi sh in aggregations also introduces another set of challenges to comparing results. For example, three species of groupers aggregating at
Ulong Channel in Palau have reported durations or repeated aggregation formation
over 2.5–6 months (spring and summer), with some fi shes present continuously at the
site. Johannes et al. ( 1999 ) reported, during 1994–1996 peak aggregation months, as
February-March for squaretail coralgrouper, June for camoufl age grouper and MayJune for brown-marbled grouper. Colin (unpublished data) using a different and more
accurate GPS-based method at the same site (Chap. 9 ) obtained different results, fi nding the peaks in 2005 to be June–July for squaretail coralgrouper, July for camoufl age
grouper and June for brown-marbled grouper. Figure 12.15 shows peaks at a nearby
site. It is not known whether differences between the studies are artefacts or real.
Johannes et al. ( 1999 ) also reported different months for peak aggregation for three
different channels in Palau. It is clear that surveys need to be conducted simultaneously in different areas to address such questions. The value of quantitative and repeatable methods for determining fi sh distribution and abundance in aggregations as well
as gathering physical data is highlighted by this example (Chap. 9 ).
It has been suggested that the seasonality and locations of reef fi sh spawning
may be related to the cycles of primary productivity, with fi shes spawning during
periods when there is adequate zooplankton, supported by phytoplankton production, for larval feeding (Johannes 1981 ; Heyman et al. 2005 ) . This might be the case
in areas with clear seasonality of primary production, such as the EP (Erisman et al.
2007 ) but is less likely to occur in the tropics which potentially have relatively
stable, but low, zooplankton populations (Chaps. 6 and 7 ). Evidence indicates that
adequate early feeding of larvae is important for ultimate survival of the pelagic
stage (Bergenius et al. 2002 ) .
P.L. Colin
Islands – Kadison et al. 2006 –, Little Cayman Island – Whaylen et al. 2004 ; Belize
– Heyman et al. 2005 ) and similar timing occurs for Nassau groupers, red hind, and
yellowfi n groupers, Mycteroperca venenosa .
Data are less available for the IWP, but the seasonal extent of TAs may be longer and
different than the TWA. The blackfi n snapper, Lutjanus fulvus , has been documented to
aggregate nearly every month of the year in Palau (Chap. 12.10 ) and there are reports
from traditional knowledge of TAs occurring year round, particularly in groupers
(Hamilton et al. 2005 ) e.g. squaretail coralgrouper (Chap. 12.8 ). It would be interesting
to know if the relatively limited annual water temperature ranges in equatorial locations
might account for reported variation in aggregation seasonality. TEK from Melanesia
indicates some groupers have year-round aggregations in some areas while others had
seasons limited to 3–4 months, varying between localities (Hamilton et al. 2005 ) .
Validating differences in patterns of aggregation timing and of fi sh numbers is not
simple. Often the timing and fi sh number peaks of aggregation for any month and over
fairly long seasonal periods are not easily documented (Chap. 9 ). Peak fi sh numbers
in an aggregation may occur for only 1 day during a lunar month, and not necessarily
on the same day of the lunar cycle each year, with surveys on days either side of the
peak having dramatic decreases in fi sh numbers. Unless surveys cover several days in
a row, the peak period may be missed and a sub-peak day mistakenly assumed to
represent the peak fi sh numbers (e.g. Fig. 12.77). The diversity of methods employed
to gather data on numbers of fi sh in aggregations also introduces another set of challenges to comparing results. For example, three species of groupers aggregating at
Ulong Channel in Palau have reported durations or repeated aggregation formation
over 2.5–6 months (spring and summer), with some fi shes present continuously at the
site. Johannes et al. ( 1999 ) reported, during 1994–1996 peak aggregation months, as
February-March for squaretail coralgrouper, June for camoufl age grouper and MayJune for brown-marbled grouper. Colin (unpublished data) using a different and more
accurate GPS-based method at the same site (Chap. 9 ) obtained different results, fi nding the peaks in 2005 to be June–July for squaretail coralgrouper, July for camoufl age
grouper and June for brown-marbled grouper. Figure 12.15 shows peaks at a nearby
site. It is not known whether differences between the studies are artefacts or real.
Johannes et al. ( 1999 ) also reported different months for peak aggregation for three
different channels in Palau. It is clear that surveys need to be conducted simultaneously in different areas to address such questions. The value of quantitative and repeatable methods for determining fi sh distribution and abundance in aggregations as well
as gathering physical data is highlighted by this example (Chap. 9 ).
It has been suggested that the seasonality and locations of reef fi sh spawning
may be related to the cycles of primary productivity, with fi shes spawning during
periods when there is adequate zooplankton, supported by phytoplankton production, for larval feeding (Johannes 1981 ; Heyman et al. 2005 ) . This might be the case
in areas with clear seasonality of primary production, such as the EP (Erisman et al.
2007 ) but is less likely to occur in the tropics which potentially have relatively
stable, but low, zooplankton populations (Chaps. 6 and 7 ). Evidence indicates that
adequate early feeding of larvae is important for ultimate survival of the pelagic
stage (Bergenius et al. 2002 ) .