xv
Preface
ready public access to the internet, site-based information of active aggregation
sites, for example, is just as readily available to those who may wish to exploit
aggregations as it is to those who wish to manage them.
Unfortunately, many of the species that aggregate to spawn are diffi cult to study
in the fi eld and scientists must be creative in addressing key questions. Large body
size and wide-ranging movements can make such species challenging to track,
while the brief duration and challenging fi eld conditions of annual spawning events
seriously limit many fi eld-based reproductive studies, especially of the experimental
or manipulation types. In the case of commercially important species, natural populations may already be much reduced or fi sh may be particularly wary. For some
research questions, smaller and/or non-commercial species, therefore, are useful for
testing hypotheses or conducting experiments. Many such examples are provided in
the chapters of this book, ranging from the small bluehead wrasse to various species
of smaller parrotfi shes and surgeonfi shes. There are also opportunities to use technological methods to describe spawning sites or to count fi sh. Nonetheless, considerable care is needed in the interpretation of such data unless it is thoroughly
ground-truthed. As one example, hydroacoustic surveys show much promise for
assessing fi sh numbers in aggregations without the need for diving. However, fi sh
numbers thereby obtained are valid only following demonstration (ground-truthing)
that the methodology is unquestionably reliable for the target species.
Information needed to manage aggregating species ranges from basic biology to
reproductive seasonality, migration distances, physical characteristics and number
of aggregation sites in a population or fi shery, to regular monitoring and the food
and economic value of aggregations to the local and national economy. Management
of aggregating species may be necessary on both aggregating and non-aggregating
(i.e. non-reproductive) phases. Spatial data are important for MPA designation and
should include catchment area and migration routes, if applicable. The period
between spawning and recruitment, the early life history, is virtually unknown yet
important for questions that explore the possible signifi cance importance of spawning times and locations (Chaps. 6 and 7 ). For fishery management, both fisherydependent and –independent data of aggregation and non-aggregation catches are
needed to provide the most comprehensive information. Understanding the value of
catches, selectivity and size/age-related mortality and reproductive schedules is also
important. Given the realities of data collection, however, much of this information
is unlikely to be forthcoming, and making best use of available data and using precedents and similar species are good starting points.
Finally, a better general appreciation by a wider public of the signifi cance of
aggregations to fi sheries and their vulnerabilities could lead to support or pressure
for the necessary protective policies and address the undeniable need for management. One option open to the conservation community could be to use aggregations
as ‘indicators’ of fi shery condition by developing an index that integrates intrinsic
(biology of the species, type of aggregation) and extrinsic (fi shery impacts) factors;
this possibility is explored in Chap. 8 . Such an index would help to highlight their
overall importance in marine ecosystems and coastal fi sheries. To manage these
species may call for a major shift in thinking, from viewing aggregations as ideal
Preface
ready public access to the internet, site-based information of active aggregation
sites, for example, is just as readily available to those who may wish to exploit
aggregations as it is to those who wish to manage them.
Unfortunately, many of the species that aggregate to spawn are diffi cult to study
in the fi eld and scientists must be creative in addressing key questions. Large body
size and wide-ranging movements can make such species challenging to track,
while the brief duration and challenging fi eld conditions of annual spawning events
seriously limit many fi eld-based reproductive studies, especially of the experimental
or manipulation types. In the case of commercially important species, natural populations may already be much reduced or fi sh may be particularly wary. For some
research questions, smaller and/or non-commercial species, therefore, are useful for
testing hypotheses or conducting experiments. Many such examples are provided in
the chapters of this book, ranging from the small bluehead wrasse to various species
of smaller parrotfi shes and surgeonfi shes. There are also opportunities to use technological methods to describe spawning sites or to count fi sh. Nonetheless, considerable care is needed in the interpretation of such data unless it is thoroughly
ground-truthed. As one example, hydroacoustic surveys show much promise for
assessing fi sh numbers in aggregations without the need for diving. However, fi sh
numbers thereby obtained are valid only following demonstration (ground-truthing)
that the methodology is unquestionably reliable for the target species.
Information needed to manage aggregating species ranges from basic biology to
reproductive seasonality, migration distances, physical characteristics and number
of aggregation sites in a population or fi shery, to regular monitoring and the food
and economic value of aggregations to the local and national economy. Management
of aggregating species may be necessary on both aggregating and non-aggregating
(i.e. non-reproductive) phases. Spatial data are important for MPA designation and
should include catchment area and migration routes, if applicable. The period
between spawning and recruitment, the early life history, is virtually unknown yet
important for questions that explore the possible signifi cance importance of spawning times and locations (Chaps. 6 and 7 ). For fishery management, both fisherydependent and –independent data of aggregation and non-aggregation catches are
needed to provide the most comprehensive information. Understanding the value of
catches, selectivity and size/age-related mortality and reproductive schedules is also
important. Given the realities of data collection, however, much of this information
is unlikely to be forthcoming, and making best use of available data and using precedents and similar species are good starting points.
Finally, a better general appreciation by a wider public of the signifi cance of
aggregations to fi sheries and their vulnerabilities could lead to support or pressure
for the necessary protective policies and address the undeniable need for management. One option open to the conservation community could be to use aggregations
as ‘indicators’ of fi shery condition by developing an index that integrates intrinsic
(biology of the species, type of aggregation) and extrinsic (fi shery impacts) factors;
this possibility is explored in Chap. 8 . Such an index would help to highlight their
overall importance in marine ecosystems and coastal fi sheries. To manage these
species may call for a major shift in thinking, from viewing aggregations as ideal