322
P.L. Colin
often diffi cult to locate and recover the drifter to download data without some type
of radio beacon. Some drifters use a combination GPS receiver/Family Radio
Spectrum (FRS) radio (as a beacon) (Austin and Atkinson 2004 ) or cell phone to
allow locating the drifter. Such a system may also allow some transfer of data
electronically.
Satellite tracked drifters are the most capable for examining propagule dispersal over days to months providing location information nearly anywhere in the
ocean and for time periods of months to years; but in many instances their capabilities far exceed the needs of a limited project. GPS/FRS drifters may cost only
about US$200 (Austin and Atkinson 2004 ) while satellite tracked drifters cost a
few thousand dollars, plus location services costs. For projects with limited needs
and budgets (such as tracking egg movements for less than 24 h after spawning)
simple systems may suffi ce, but for regional work satellite drifters are usually
advisable.
9.6.16 Bathymetric Mapping
Combined with data from instrumentation of aggregation sites, detailed bathymetry
of sites provides an ability to interpret the sometimes confl icting information regarding
the possible benefi ts of sites in a physical and biological sense. The recording of
single point position/depth data in the National Marine Electronic Association
(NMEA) data from the GPS/depth sounder units has made it possible for researchers to easily map virtually any reef fi sh aggregation area in detail. Colin et al. ( 2003 )
and Kvernevik et al. ( 2002 ) described the basic system for single point bathymetric
mapping of spawning aggregation sites. Heyman et al. ( 2007 ) used a lower frequency transducer (greater depth penetration) to map some aggregation sites on
the Belize barrier reef and Kobara and Heyman ( 2008 ) did similar surveys in the
Cayman Islands. Solid state NMEA data loggers ( www.brookhouseonline.com ) are
simple, rugged and often allow longer data collection than portable computers.
Single point data (latitude, longitude, depth) allows production of limited resolution
maps, while side-scan and multi-beam sonar provide amazing resolution of large
areas of bottom (Burton et al. 2005 ; Kadison et al. 2006 ; Nemeth et al. 2008 ) .
The congruence of GPS derived maps allows previous data that is GPS located to
be applied to more detailed bathymetry at any time in the future. The location of the
tiger grouper, Mycteroperca tigris , aggregation site reported by Sadovy et al. ( 1994 )
was determined by GPS receiver and this could later be plotted on the multi-beam
sonar map of the Puerto Rico Virgin Island shelf showing it occurs on a broad
promontory of the shelf edge east of Vieques, Puerto Rico (Fig. 9.12 ).
Multibeam sonar is presently the ultimate in method for producing detailed maps
of the bottom for most spawning aggregation areas (Weaver et al. 2005 ; Nemeth
et al. 2008 ; Kadison et al. 2006, 2009 ) . Airborne LIDAR (Light Detection and
Ranging) can map reef and aggregation areas in relatively clear water (Brock et al.
2004 ) but is limited in depth capabilities.
P.L. Colin
often diffi cult to locate and recover the drifter to download data without some type
of radio beacon. Some drifters use a combination GPS receiver/Family Radio
Spectrum (FRS) radio (as a beacon) (Austin and Atkinson 2004 ) or cell phone to
allow locating the drifter. Such a system may also allow some transfer of data
electronically.
Satellite tracked drifters are the most capable for examining propagule dispersal over days to months providing location information nearly anywhere in the
ocean and for time periods of months to years; but in many instances their capabilities far exceed the needs of a limited project. GPS/FRS drifters may cost only
about US$200 (Austin and Atkinson 2004 ) while satellite tracked drifters cost a
few thousand dollars, plus location services costs. For projects with limited needs
and budgets (such as tracking egg movements for less than 24 h after spawning)
simple systems may suffi ce, but for regional work satellite drifters are usually
advisable.
9.6.16 Bathymetric Mapping
Combined with data from instrumentation of aggregation sites, detailed bathymetry
of sites provides an ability to interpret the sometimes confl icting information regarding
the possible benefi ts of sites in a physical and biological sense. The recording of
single point position/depth data in the National Marine Electronic Association
(NMEA) data from the GPS/depth sounder units has made it possible for researchers to easily map virtually any reef fi sh aggregation area in detail. Colin et al. ( 2003 )
and Kvernevik et al. ( 2002 ) described the basic system for single point bathymetric
mapping of spawning aggregation sites. Heyman et al. ( 2007 ) used a lower frequency transducer (greater depth penetration) to map some aggregation sites on
the Belize barrier reef and Kobara and Heyman ( 2008 ) did similar surveys in the
Cayman Islands. Solid state NMEA data loggers ( www.brookhouseonline.com ) are
simple, rugged and often allow longer data collection than portable computers.
Single point data (latitude, longitude, depth) allows production of limited resolution
maps, while side-scan and multi-beam sonar provide amazing resolution of large
areas of bottom (Burton et al. 2005 ; Kadison et al. 2006 ; Nemeth et al. 2008 ) .
The congruence of GPS derived maps allows previous data that is GPS located to
be applied to more detailed bathymetry at any time in the future. The location of the
tiger grouper, Mycteroperca tigris , aggregation site reported by Sadovy et al. ( 1994 )
was determined by GPS receiver and this could later be plotted on the multi-beam
sonar map of the Puerto Rico Virgin Island shelf showing it occurs on a broad
promontory of the shelf edge east of Vieques, Puerto Rico (Fig. 9.12 ).
Multibeam sonar is presently the ultimate in method for producing detailed maps
of the bottom for most spawning aggregation areas (Weaver et al. 2005 ; Nemeth
et al. 2008 ; Kadison et al. 2006, 2009 ) . Airborne LIDAR (Light Detection and
Ranging) can map reef and aggregation areas in relatively clear water (Brock et al.
2004 ) but is limited in depth capabilities.