270
Y. Sadovy de Mitcheson and B. Erisman
Challenges also persist in achieving effective aggregation management because
of misperceptions or lack of understanding that make it diffi cult to gain public and
political support. It is particularly in such areas that greater awareness and better
understanding of these fi sheries, and the economic and social implications of
losing them, are needed. An obvious example is that the many fi sh taken over a
short, often intense, period of time from aggregations give the illusion that there
are plenty of fi sh, with no hint that a high proportion of a stock or population might
be involved and hence that management might be advisable. As just one example,
orange roughy in the 1980s seemed to be a boundless resource. “On one occasion
54 tonnes were caught in only 20 minutes’ trawling – but this apparent abundance
was an illusion, as the fi sh had been concentrated in spawning schools.” http://
www.teara.govt.nz/en/fi shing-industry/5 (Robertson 1991 ) . In managed fi sheries,
there may also be the belief that conventional management obviates the need for
specifi c attention to be paid to aggregation management (e.g. leopard coralgrouper
trout in Australia Chaps. 11, 12.9 ).
From a technical fi shery monitoring perspective the seasonal change in behaviour of both fi sh and fi shermen associated with aggregations make fi sh abundance
diffi cult to estimate because catchability (i.e. the proportion of the total stock caught
by one unit of fi shing effort) changes over the year with the result that CPUE (widely
used as an indicator of fi sh abundance) is not proportional to fi sh abundance.
High catchability means that fi sh will continue to be caught in large numbers in
aggregations even as the population as a whole declines, making aggregation CPUE
a poor indicator of fi shery status (Fig. 8.6 , Chap. 11 ). For this reason, much care is
needed if only fi shery-dependent data are available to assess aggregation status, and
every effort made to periodically monitor aggregations by fi shery-independent
means, ideally including visual assessment (e.g. Colin et al. 2003 ) .
The value of protecting spawning adults to the fi shery at non-aggregation times
needs to be considered in fi shery models to assist managers and political and
community leaders in better appreciating the practical and economic implications of
management, or lack thereof, in the long term. It is unlikely that dive tourism alone
will bring higher economic benefi ts, especially if there is heavy social or economic
pressure to fi sh in the region. The switch from viewing spawning aggregations as a
target of fi shing to a focus of protection will require a major shift in understanding
and perspective that fi shery analyses can provide. It is of value to note that many
fi shers intuitively understand the importance of allowing females full of eggs to
spawn and can readily accept why aggregations might need to be managed (YSM
and BE personal observation). Indeed, in some countries (e.g. New Zealand,
Australia, USA, Bahamas) berried lobsters (females with external fertilized eggs)
have variously been protected in fi sheries for as much as 100 years; the same thinking
has not yet been applied to female fi sh.
Finally, we recognize the problem of shifting baselines (Pauly 1995 ) . Most
exploited aggregations are not managed, may have already declined substantially
or there is no community experience of reduced landings in aggregations when
these are newly exploited. This means that much of the potential production from
an aggregation may be lost before action is understood to be needed. Since even
Y. Sadovy de Mitcheson and B. Erisman
Challenges also persist in achieving effective aggregation management because
of misperceptions or lack of understanding that make it diffi cult to gain public and
political support. It is particularly in such areas that greater awareness and better
understanding of these fi sheries, and the economic and social implications of
losing them, are needed. An obvious example is that the many fi sh taken over a
short, often intense, period of time from aggregations give the illusion that there
are plenty of fi sh, with no hint that a high proportion of a stock or population might
be involved and hence that management might be advisable. As just one example,
orange roughy in the 1980s seemed to be a boundless resource. “On one occasion
54 tonnes were caught in only 20 minutes’ trawling – but this apparent abundance
was an illusion, as the fi sh had been concentrated in spawning schools.” http://
www.teara.govt.nz/en/fi shing-industry/5 (Robertson 1991 ) . In managed fi sheries,
there may also be the belief that conventional management obviates the need for
specifi c attention to be paid to aggregation management (e.g. leopard coralgrouper
trout in Australia Chaps. 11, 12.9 ).
From a technical fi shery monitoring perspective the seasonal change in behaviour of both fi sh and fi shermen associated with aggregations make fi sh abundance
diffi cult to estimate because catchability (i.e. the proportion of the total stock caught
by one unit of fi shing effort) changes over the year with the result that CPUE (widely
used as an indicator of fi sh abundance) is not proportional to fi sh abundance.
High catchability means that fi sh will continue to be caught in large numbers in
aggregations even as the population as a whole declines, making aggregation CPUE
a poor indicator of fi shery status (Fig. 8.6 , Chap. 11 ). For this reason, much care is
needed if only fi shery-dependent data are available to assess aggregation status, and
every effort made to periodically monitor aggregations by fi shery-independent
means, ideally including visual assessment (e.g. Colin et al. 2003 ) .
The value of protecting spawning adults to the fi shery at non-aggregation times
needs to be considered in fi shery models to assist managers and political and
community leaders in better appreciating the practical and economic implications of
management, or lack thereof, in the long term. It is unlikely that dive tourism alone
will bring higher economic benefi ts, especially if there is heavy social or economic
pressure to fi sh in the region. The switch from viewing spawning aggregations as a
target of fi shing to a focus of protection will require a major shift in understanding
and perspective that fi shery analyses can provide. It is of value to note that many
fi shers intuitively understand the importance of allowing females full of eggs to
spawn and can readily accept why aggregations might need to be managed (YSM
and BE personal observation). Indeed, in some countries (e.g. New Zealand,
Australia, USA, Bahamas) berried lobsters (females with external fertilized eggs)
have variously been protected in fi sheries for as much as 100 years; the same thinking
has not yet been applied to female fi sh.
Finally, we recognize the problem of shifting baselines (Pauly 1995 ) . Most
exploited aggregations are not managed, may have already declined substantially
or there is no community experience of reduced landings in aggregations when
these are newly exploited. This means that much of the potential production from
an aggregation may be lost before action is understood to be needed. Since even