303
9 Studying and Monitoring Aggregating Species
as well as possibly allowing for comparative studies if aggregations are subjected to
different levels of fi shing effort. Then there is the “dumb luck” factor, which tells us
that to discover something which is unknown it is best to be in the right place at the
right time. The chances of this go up as more time is spent in the fi eld looking at what
is going on and, just as importantly, being able to recognize it when you see it.
The worldwide increase in diving tourism offers an opportunity for dive guides,
underwater photographers and fi lmmakers to discover new aggregations. Expedition
boats now visit the most remote areas of the ocean and if personnel on such vessels
are attuned to looking for aggregations, many new discoveries could be made. The
discovery of a spawning aggregation of the leather bass was made by guides from
an expedition vessel (Aburto-Oropeza and Hull 2008 ) .
Remote sensing is suggested for identifying aggregation sites (Kobara and Heyman
2007 ) using criteria such as the presence of reef promontories which may (or may not)
be associated with them (see Chap. 5 ). Satellite images provide a remarkable perspective on the upper geomorphology of reef areas, but are limited in some regards. In many
areas of the Caribbean region the insular shelf edge, along with many known TA sites,
is not even visible due to clarity of the water in Landsat seven images (see Fig. 5.12,
Chap. 5 ) and consequently satellite images are of little value in locating such sites.
Often the location of promontories and general geomorphology is already known
from other sources, such as generally available marine bathymetric charts, reducing
the importance of satellite images in locating such features. Remote sensing seems an
easy, high technology alternative to tedious fi eld work to discover aggregations, but
has not been applied with any success in locating any new aggregation. It is critical not
to dismiss the need for fi eld work to discover or verify the occurrence of aggregations.
Moreover, hypothesis-testing for locating new aggregation sites needs to include the
study of control sites not expected to be aggregation areas, and could be confounded by
loss of active sites due to overfi shing in the case of commercial species.
9.6 Measurement of Biological and Behavioural Aspects
of Aggregations
The biological and physical dynamics of aggregations are of great interest since
these are critical in the replenishment of population through recruits. Aggregations
exist in a physical environment which cannot be separated from the biological, but
aside from exceptional physical conditions causing reproductive failure, variation in
biological aspects may be more infl uential in determining the outcome of reproduction
(See Sect. 8.4 ).
9.6.1 Behavioural Aspects
Documenting the behaviour of aggregating fi shes is important but often a diffi cult
prospect. Data are obtained by observation, photographic or videographic methods,
9 Studying and Monitoring Aggregating Species
as well as possibly allowing for comparative studies if aggregations are subjected to
different levels of fi shing effort. Then there is the “dumb luck” factor, which tells us
that to discover something which is unknown it is best to be in the right place at the
right time. The chances of this go up as more time is spent in the fi eld looking at what
is going on and, just as importantly, being able to recognize it when you see it.
The worldwide increase in diving tourism offers an opportunity for dive guides,
underwater photographers and fi lmmakers to discover new aggregations. Expedition
boats now visit the most remote areas of the ocean and if personnel on such vessels
are attuned to looking for aggregations, many new discoveries could be made. The
discovery of a spawning aggregation of the leather bass was made by guides from
an expedition vessel (Aburto-Oropeza and Hull 2008 ) .
Remote sensing is suggested for identifying aggregation sites (Kobara and Heyman
2007 ) using criteria such as the presence of reef promontories which may (or may not)
be associated with them (see Chap. 5 ). Satellite images provide a remarkable perspective on the upper geomorphology of reef areas, but are limited in some regards. In many
areas of the Caribbean region the insular shelf edge, along with many known TA sites,
is not even visible due to clarity of the water in Landsat seven images (see Fig. 5.12,
Chap. 5 ) and consequently satellite images are of little value in locating such sites.
Often the location of promontories and general geomorphology is already known
from other sources, such as generally available marine bathymetric charts, reducing
the importance of satellite images in locating such features. Remote sensing seems an
easy, high technology alternative to tedious fi eld work to discover aggregations, but
has not been applied with any success in locating any new aggregation. It is critical not
to dismiss the need for fi eld work to discover or verify the occurrence of aggregations.
Moreover, hypothesis-testing for locating new aggregation sites needs to include the
study of control sites not expected to be aggregation areas, and could be confounded by
loss of active sites due to overfi shing in the case of commercial species.
9.6 Measurement of Biological and Behavioural Aspects
of Aggregations
The biological and physical dynamics of aggregations are of great interest since
these are critical in the replenishment of population through recruits. Aggregations
exist in a physical environment which cannot be separated from the biological, but
aside from exceptional physical conditions causing reproductive failure, variation in
biological aspects may be more infl uential in determining the outcome of reproduction
(See Sect. 8.4 ).
9.6.1 Behavioural Aspects
Documenting the behaviour of aggregating fi shes is important but often a diffi cult
prospect. Data are obtained by observation, photographic or videographic methods,