25
2 Ecosystem Aspects of Species That Aggregate to Spawn
through an ecosystem to and from a spawning site, the spatial and temporal scales
at which spawning aggregations operate need to be understood.
The most effective methods for measuring movements of aggregating species are
conventional mark-recapture studies and acoustic tracking (Chap. 9 ). Conventional
tagging typically relies on the cooperation of local fi shers to return tags and provide
accurate information on recapture location. Fish that are recaptured on the spawning
site also provide estimates of size- and gender-specifi c residence time, and growth
rate. Fish that are recaptured away from the spawning site provide estimates of
gender-specifi c migration distance and direction, swim speeds, resident habitats and
growth rates. Although most tag returns will be from areas with the greatest fi shing
effort, producing gaps in spatial data, this method can be used to calculate catchment area (Fig. 2.1 ).
Identifying migration pathways is more diffi cult and tag loss and damage can
reduce the effectiveness of this method (Wormald and Steele 2008 ) . Acoustic tags,
which transmit unique identifi cation codes from individual fi sh, used in combination
with a directional hydrophone or an array of underwater acoustic receivers (Domeier
2005 ) , provide detailed information on location, depth, residence time, frequency and
timing of migration, habitat use and small-scale movement patterns of tagged fi sh
(Holland et al. 1993 ; Zeller 1999 ; Meyer et al. 2000 ; Beets et al. 2003 ; Rhodes and
Fig. 2.1 Red hind ( Epinephelus guttatus ) functional migration area ( yellow polygon ) south of
St. Thomas, US Virgin Islands calculated from a mark-recapture study (Nemeth 2005 ) . Fish were
tagged at the spawning aggregation site ( red star ) and recaptured ( dots ) by fi shermen. Straight line
migration distances ( black lines ) defi ne the catchment area (500 km
2 ). Areas defi ned by white lines
delimit Red Hind Bank Marine Conservation District ( large ) and Grammanik Bank ( small )
2 Ecosystem Aspects of Species That Aggregate to Spawn
through an ecosystem to and from a spawning site, the spatial and temporal scales
at which spawning aggregations operate need to be understood.
The most effective methods for measuring movements of aggregating species are
conventional mark-recapture studies and acoustic tracking (Chap. 9 ). Conventional
tagging typically relies on the cooperation of local fi shers to return tags and provide
accurate information on recapture location. Fish that are recaptured on the spawning
site also provide estimates of size- and gender-specifi c residence time, and growth
rate. Fish that are recaptured away from the spawning site provide estimates of
gender-specifi c migration distance and direction, swim speeds, resident habitats and
growth rates. Although most tag returns will be from areas with the greatest fi shing
effort, producing gaps in spatial data, this method can be used to calculate catchment area (Fig. 2.1 ).
Identifying migration pathways is more diffi cult and tag loss and damage can
reduce the effectiveness of this method (Wormald and Steele 2008 ) . Acoustic tags,
which transmit unique identifi cation codes from individual fi sh, used in combination
with a directional hydrophone or an array of underwater acoustic receivers (Domeier
2005 ) , provide detailed information on location, depth, residence time, frequency and
timing of migration, habitat use and small-scale movement patterns of tagged fi sh
(Holland et al. 1993 ; Zeller 1999 ; Meyer et al. 2000 ; Beets et al. 2003 ; Rhodes and
Fig. 2.1 Red hind ( Epinephelus guttatus ) functional migration area ( yellow polygon ) south of
St. Thomas, US Virgin Islands calculated from a mark-recapture study (Nemeth 2005 ) . Fish were
tagged at the spawning aggregation site ( red star ) and recaptured ( dots ) by fi shermen. Straight line
migration distances ( black lines ) defi ne the catchment area (500 km
2 ). Areas defi ned by white lines
delimit Red Hind Bank Marine Conservation District ( large ) and Grammanik Bank ( small )