296
P.L. Colin
in areas where aggregations would occur. Theft or disturbance of instruments is a
problem in many areas, but some (temperature and salinity loggers) can be hidden
for extra protection if needed.
OT – Sampling and Analysis of Otoliths
There are many standard techniques for preparing and analyzing otoliths (reviewed
by Campana 2001 ; Campana and Thorrold 2001 ) . For tropical species that
aggregate to spawn, it may be possible to identify annual growth rings in otoliths
(e.g. Choat et al. 2006 ). For larvae and young juveniles, daily growth increments
may be visible and quantifi able in otoliths, including settlement marks indicating
the transition from pelagic to benthic life. Otolith chemistry (stable isotope ratios)
also provides some prospects for looking at life habits of young and adult aggregating fi shes (Patterson et al. 1999 ) , or the environment in which larvae have grown up
(Patterson et al. 2005 ) .
RV – Remote Operating Vehicle (ROVs) and Submersibles
ROVs are seldom used for spawning aggregation observations, but can be useful
where fi sh are deep or easily disturbed by a diver. Starr et al. ( 2007 ) used a
ROV to observe spawning by the yellowfi n grouper, Mycteroperca venenosa , at
40–45 m along a reef drop off at Glover’s Reef, Belize, as well as observing aggregations of two other grouper species. Submersibles are usually beyond the fi nancial
capabilities of most aggregation studies, but Erisman et al. ( 2009 ) observed spawning of leather bass, Dermatolepis dermatolepis , from a sub at Cocos Island (east
Pacifi c), while Gilmore and Jones ( 1992 ) observed deep grouper aggregations off
Florida.
SC – Specimen Collection
Fishes from aggregations may need to be collected by researchers themselves, if
there is no active fi shery on the aggregation, using hook and line, fi sh traps, or by
Fig. 9.2 Modern current meters provide accurate data on current speed and direction at ( a ) a single
depth for the acoustic doppler current meter and ( b ) at multiple depths above (or below ) for the
acoustic doppler current profi lers ( ADCP ). The units gather provide data on temperature and, if
hard mounted on the bottom, the tide (Photos: Patrick L. Colin)
P.L. Colin
in areas where aggregations would occur. Theft or disturbance of instruments is a
problem in many areas, but some (temperature and salinity loggers) can be hidden
for extra protection if needed.
OT – Sampling and Analysis of Otoliths
There are many standard techniques for preparing and analyzing otoliths (reviewed
by Campana 2001 ; Campana and Thorrold 2001 ) . For tropical species that
aggregate to spawn, it may be possible to identify annual growth rings in otoliths
(e.g. Choat et al. 2006 ). For larvae and young juveniles, daily growth increments
may be visible and quantifi able in otoliths, including settlement marks indicating
the transition from pelagic to benthic life. Otolith chemistry (stable isotope ratios)
also provides some prospects for looking at life habits of young and adult aggregating fi shes (Patterson et al. 1999 ) , or the environment in which larvae have grown up
(Patterson et al. 2005 ) .
RV – Remote Operating Vehicle (ROVs) and Submersibles
ROVs are seldom used for spawning aggregation observations, but can be useful
where fi sh are deep or easily disturbed by a diver. Starr et al. ( 2007 ) used a
ROV to observe spawning by the yellowfi n grouper, Mycteroperca venenosa , at
40–45 m along a reef drop off at Glover’s Reef, Belize, as well as observing aggregations of two other grouper species. Submersibles are usually beyond the fi nancial
capabilities of most aggregation studies, but Erisman et al. ( 2009 ) observed spawning of leather bass, Dermatolepis dermatolepis , from a sub at Cocos Island (east
Pacifi c), while Gilmore and Jones ( 1992 ) observed deep grouper aggregations off
Florida.
SC – Specimen Collection
Fishes from aggregations may need to be collected by researchers themselves, if
there is no active fi shery on the aggregation, using hook and line, fi sh traps, or by
Fig. 9.2 Modern current meters provide accurate data on current speed and direction at ( a ) a single
depth for the acoustic doppler current meter and ( b ) at multiple depths above (or below ) for the
acoustic doppler current profi lers ( ADCP ). The units gather provide data on temperature and, if
hard mounted on the bottom, the tide (Photos: Patrick L. Colin)