574
Y. Sadovy de Mitcheson and P.L. Colin
the day, often in relation to tidal cycles. Despite the trends indicated, the adaptive
signifi cance of timing of spawning is not known.
Turning to the biological and socio-economic implications of fi shing on spawning aggregations and aggregating species, Chap. 8 by Yvonne Sadovy de Mitcheson
and Brad Erisman explores the extent to which they can be harvested sustainably
beyond low-level subsistence fi shing and looks with abundant eggs ready to hatch;
sources of the next generation at attitudes towards their management. In all documented cases, unmanaged exploitation has resulted in population depletions. While
it is clear that aggregation fi sheries are important and widespread globally, it is also
evident that they are typically poorly documented or managed. This is partly due to
the fact that large catches give an ‘illusion of plenty’, belying the need for any intervention and thwarting proactive management planning. Interestingly, while the idea
of protecting females that are clearly with abundant eggs close to hatching is widely
accepted in the case of egg-bearing (“berried”) lobsters and crabs, similar thinking
has never been applied to female fi sh that are clearly full of eggs. Likewise, while
few people would deny that turtle nesting colonies need protection and that nesting
seabird colonies should be left in peace, few fi sh spawning aggregations receive
similar care. Rather, they remain targets for fi shing rather than for protection.
From a biological perspective, there is a need to incorporate elements of fi sh mating
systems into fi shery models to generate different scenarios against which to assess
observations, make predictions or conduct comparative assessments. As aggregations
get smaller from overfi shing, we need to consider whether there are threshold
densities below which recovery is likely to be much compromised because of behavioural components, such as the Allee Effect. For species that change sex, are the
opportunities provided by aggregations to assess numbers of adult males and females
important for cuing sex change events and hence determining operational sex ratios?
Economic considerations should address long-term objectives as well as more
immediate short-term pressures. For example, gluts of fi sh produced by harvesting
TAs can be wasteful and lead to reduced unit prices as well as contribute to overfi shing of the species. It may, in the long term, be far more benefi cial for the fi shery if
fi shing is restricted to the non-spawning season, producing stable catches throughout
the year, better prices and a more productive fi shery because spawning is allowed to
take place undisturbed. In the development of fi sheries resources, it is not uncommon for the status of the resource, and hence its capacity to withstand development,
to be ignored. The widespread introduction of ice plants in the Pacifi c to encourage
and facilitate marketing from more remote locations, for example, took no account
of the underlying resource base that would be affected.
Turning now to the important task of improving information on aggregations and
monitoring those that are or could be managed, in Chap. 9 Pat Colin covers the
methods available to quantify and document the various aspects of spawning aggregations, highlighting those methods that are most effective under different circumstances, as well as various shortcomings. This chapter provides considerable updates
on the earlier SCRFA Methods Manual (Colin et al. 2003 ) . Fortunately, methods are
becoming more standardized, allowing for better comparisons among species and
localities and over time. The application of new technology is particularly promising
Y. Sadovy de Mitcheson and P.L. Colin
the day, often in relation to tidal cycles. Despite the trends indicated, the adaptive
signifi cance of timing of spawning is not known.
Turning to the biological and socio-economic implications of fi shing on spawning aggregations and aggregating species, Chap. 8 by Yvonne Sadovy de Mitcheson
and Brad Erisman explores the extent to which they can be harvested sustainably
beyond low-level subsistence fi shing and looks with abundant eggs ready to hatch;
sources of the next generation at attitudes towards their management. In all documented cases, unmanaged exploitation has resulted in population depletions. While
it is clear that aggregation fi sheries are important and widespread globally, it is also
evident that they are typically poorly documented or managed. This is partly due to
the fact that large catches give an ‘illusion of plenty’, belying the need for any intervention and thwarting proactive management planning. Interestingly, while the idea
of protecting females that are clearly with abundant eggs close to hatching is widely
accepted in the case of egg-bearing (“berried”) lobsters and crabs, similar thinking
has never been applied to female fi sh that are clearly full of eggs. Likewise, while
few people would deny that turtle nesting colonies need protection and that nesting
seabird colonies should be left in peace, few fi sh spawning aggregations receive
similar care. Rather, they remain targets for fi shing rather than for protection.
From a biological perspective, there is a need to incorporate elements of fi sh mating
systems into fi shery models to generate different scenarios against which to assess
observations, make predictions or conduct comparative assessments. As aggregations
get smaller from overfi shing, we need to consider whether there are threshold
densities below which recovery is likely to be much compromised because of behavioural components, such as the Allee Effect. For species that change sex, are the
opportunities provided by aggregations to assess numbers of adult males and females
important for cuing sex change events and hence determining operational sex ratios?
Economic considerations should address long-term objectives as well as more
immediate short-term pressures. For example, gluts of fi sh produced by harvesting
TAs can be wasteful and lead to reduced unit prices as well as contribute to overfi shing of the species. It may, in the long term, be far more benefi cial for the fi shery if
fi shing is restricted to the non-spawning season, producing stable catches throughout
the year, better prices and a more productive fi shery because spawning is allowed to
take place undisturbed. In the development of fi sheries resources, it is not uncommon for the status of the resource, and hence its capacity to withstand development,
to be ignored. The widespread introduction of ice plants in the Pacifi c to encourage
and facilitate marketing from more remote locations, for example, took no account
of the underlying resource base that would be affected.
Turning now to the important task of improving information on aggregations and
monitoring those that are or could be managed, in Chap. 9 Pat Colin covers the
methods available to quantify and document the various aspects of spawning aggregations, highlighting those methods that are most effective under different circumstances, as well as various shortcomings. This chapter provides considerable updates
on the earlier SCRFA Methods Manual (Colin et al. 2003 ) . Fortunately, methods are
becoming more standardized, allowing for better comparisons among species and
localities and over time. The application of new technology is particularly promising