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P.L. Colin
instrumentation or measurement. Interviews with fi shers and experienced divers can
provide useful information on behaviour and are considered further in Chap. 10 .
Behavioural work should not be limited to times and locations of aggregation. For
some transient species, not all individuals are known to migrate to aggregation sites.
Behaviour during non-aggregation periods has potential for providing added insight
into changes occurring during aggregation and spawning. For example, the social
structure of Nassau grouper on their normal home ranges is quite complicated,
both during and outside of aggregation periods, with what appear to be dominance
hierarchies, territoriality and intra-specifi c aggression (Chap. 12.6 ).
9.6.2 Tagging and Tracking
Conventional external tags are very useful for aggregation studies. Fish can be
tagged while aggregated (Nemeth et al. 2007 ) or while dispersed (Colin 1992 ) . Tagrecapture has also been used to estimate size of aggregations (Luckhurst et al. 2006 ) .
Nemeth et al. ( 2007 ) determined the “functional spawning migration area” of red
hind aggregations in the Virgin Islands from tagging studies (Chap. 2 ). Distances
and routing of migration relative to the aggregation site, differences between sexes
and sizes of fi sh, can be examined if a suffi cient number of fi sh are tagged. Having
a fi shery outside of the aggregation, and fi shers willing to return the tags (usually
with a reward and following an information campaign) is important for success. In
such cases, the preparation phase for such a study is important to ensure that fi shers
know about the tags and where to return them as well as the reasons for the study.
Planning such studies needs to take into account that recapture rates when using
such tags (at least not in relation to aggregations) may be as low as 5%, so sample
sizes need to be scaled accordingly (Nemeth 2005 ) . The education value of this type
of tagging is high since the fi shing community is typically directly involved and can
immediately understand the distances that fi sh are moving if informed of tagging
location and reason for study.
Acoustic tagging is often intended to track “local” movements of fi shes, but if large
numbers of receivers are dispersed can monitor movements around entire islands or
along coastal features (Domeier 2005 ; Nemeth et al. 2007 ; Starr et al. 2007 ) . Tagging
fi sh before migration to an unknown spawning site combined with a dispersed array
of receivers could be a useful method for discovering an unknown spawning aggregation. This approach would probably be useful for species like Nassau grouper which
are believed to migrate along shelf edges at specifi c times (Colin 1992 ) and along
consistent pathways which can be instrumented with receivers.
External and acoustic (ultrasonic) tagging are mutually advantageous (Nemeth
et al. 2007 ; Starr et al. 2007 ) . External tags can provide information on short to
long distance migration to and from spawning aggregations, as well as growth of
individuals. Acoustic tagging provides data on occurrence and persistence of
individuals at an aggregation, site fi delity over time and local movements (Zeller
1998b ; Zeller and Russ 1998 ; Nemeth et al. 2007 ; Starr et al. 2007 ) .
P.L. Colin
instrumentation or measurement. Interviews with fi shers and experienced divers can
provide useful information on behaviour and are considered further in Chap. 10 .
Behavioural work should not be limited to times and locations of aggregation. For
some transient species, not all individuals are known to migrate to aggregation sites.
Behaviour during non-aggregation periods has potential for providing added insight
into changes occurring during aggregation and spawning. For example, the social
structure of Nassau grouper on their normal home ranges is quite complicated,
both during and outside of aggregation periods, with what appear to be dominance
hierarchies, territoriality and intra-specifi c aggression (Chap. 12.6 ).
9.6.2 Tagging and Tracking
Conventional external tags are very useful for aggregation studies. Fish can be
tagged while aggregated (Nemeth et al. 2007 ) or while dispersed (Colin 1992 ) . Tagrecapture has also been used to estimate size of aggregations (Luckhurst et al. 2006 ) .
Nemeth et al. ( 2007 ) determined the “functional spawning migration area” of red
hind aggregations in the Virgin Islands from tagging studies (Chap. 2 ). Distances
and routing of migration relative to the aggregation site, differences between sexes
and sizes of fi sh, can be examined if a suffi cient number of fi sh are tagged. Having
a fi shery outside of the aggregation, and fi shers willing to return the tags (usually
with a reward and following an information campaign) is important for success. In
such cases, the preparation phase for such a study is important to ensure that fi shers
know about the tags and where to return them as well as the reasons for the study.
Planning such studies needs to take into account that recapture rates when using
such tags (at least not in relation to aggregations) may be as low as 5%, so sample
sizes need to be scaled accordingly (Nemeth 2005 ) . The education value of this type
of tagging is high since the fi shing community is typically directly involved and can
immediately understand the distances that fi sh are moving if informed of tagging
location and reason for study.
Acoustic tagging is often intended to track “local” movements of fi shes, but if large
numbers of receivers are dispersed can monitor movements around entire islands or
along coastal features (Domeier 2005 ; Nemeth et al. 2007 ; Starr et al. 2007 ) . Tagging
fi sh before migration to an unknown spawning site combined with a dispersed array
of receivers could be a useful method for discovering an unknown spawning aggregation. This approach would probably be useful for species like Nassau grouper which
are believed to migrate along shelf edges at specifi c times (Colin 1992 ) and along
consistent pathways which can be instrumented with receivers.
External and acoustic (ultrasonic) tagging are mutually advantageous (Nemeth
et al. 2007 ; Starr et al. 2007 ) . External tags can provide information on short to
long distance migration to and from spawning aggregations, as well as growth of
individuals. Acoustic tagging provides data on occurrence and persistence of
individuals at an aggregation, site fi delity over time and local movements (Zeller
1998b ; Zeller and Russ 1998 ; Nemeth et al. 2007 ; Starr et al. 2007 ) .