249
8 Fishery and Biological Implications of Fishing Spawning Aggregations…
could be a specifi c driver of population declines (see Sect. 8.3.1 ) and examine the
role of fi shing technology (Sect. 8.3.2 ). In Sect. 8.4 we go on to explore the possible
biological (intrinsic) factors affecting responses to aggregation fi shing. We then consider whether aggregations in general, or perhaps certain types of aggregations, need
specifi c management attention, and address management options.
8.3.1 Specifi c Effects of Aggregation Versus
Non-aggregation Fishing
In the management of aggregating species, understanding the specifi c impacts of
fi shing their aggregations, as distinct from the overall impacts of total fi shing pressure on the target population throughout the year is important, albeit challenging.
Natural resource managers must decide where funds and capacity are best directed,
what kind of management is most appropriate and socially acceptable, and the economic implications for fi shing communities of actions such as aggregation closures,
or, conversely, their losses. Since detailed fi shery and biological information is
unavailable for most exploited reef fi shes, and because few datasets allow for indepth examination of their fi sheries, teasing out cause and effect of aggregation
versus non-aggregation fi shing is problematic. The challenge is further compounded
by the fact that other life-history characteristics, such as longevity or late sexual
maturation, can strongly infl uence responses to fi shing, and many aggregating
species exhibit these characteristics (Reynolds et al. 2005 ) . Moreover, making comparisons across very different taxa is complicated by phylogenetic differences,
while analyses that treat species values as statistically independent points are
questionable because closely related species may share traits through common
descent rather than through independent evolution (Felsenstein 1985 ) .
At least four approaches allow examination of possible fi shery implications of
fi shing spawning aggregations. The fi rst is to use information qualitatively across a
wide taxonomic range of species and determine whether those in which aggregations are specifi cally targeted have shown the most marked changes. The second is
to compare the fi sheries status of several aggregating species within a single multispecies fi shery, in which all species are exposed to similar fi shing profi les and show
general biological similarities yet exhibit different degrees of aggregating behaviour
and extent of targeting of aggregations. A third approach, and one that addresses
phylogenetic issues, is to select a single lineage that has both aggregating and nonaggregating species and examine fi shery or conservation status by species. The
fourth involves a comparison of the fi shing history of a single aggregating species
among locations or populations, ranging from situations where its aggregations are
targeted and make a signifi cant contribution to annual landings to those where
aggregations contribute little to the overall fi shery. While none of these four
approaches entirely avoids possible confounding factors of life history differences,
relatedness or the relative importance of non-aggregation fi shing, examining the
question from different perspectives at least provides a semi-quantitative means of
8 Fishery and Biological Implications of Fishing Spawning Aggregations…
could be a specifi c driver of population declines (see Sect. 8.3.1 ) and examine the
role of fi shing technology (Sect. 8.3.2 ). In Sect. 8.4 we go on to explore the possible
biological (intrinsic) factors affecting responses to aggregation fi shing. We then consider whether aggregations in general, or perhaps certain types of aggregations, need
specifi c management attention, and address management options.
8.3.1 Specifi c Effects of Aggregation Versus
Non-aggregation Fishing
In the management of aggregating species, understanding the specifi c impacts of
fi shing their aggregations, as distinct from the overall impacts of total fi shing pressure on the target population throughout the year is important, albeit challenging.
Natural resource managers must decide where funds and capacity are best directed,
what kind of management is most appropriate and socially acceptable, and the economic implications for fi shing communities of actions such as aggregation closures,
or, conversely, their losses. Since detailed fi shery and biological information is
unavailable for most exploited reef fi shes, and because few datasets allow for indepth examination of their fi sheries, teasing out cause and effect of aggregation
versus non-aggregation fi shing is problematic. The challenge is further compounded
by the fact that other life-history characteristics, such as longevity or late sexual
maturation, can strongly infl uence responses to fi shing, and many aggregating
species exhibit these characteristics (Reynolds et al. 2005 ) . Moreover, making comparisons across very different taxa is complicated by phylogenetic differences,
while analyses that treat species values as statistically independent points are
questionable because closely related species may share traits through common
descent rather than through independent evolution (Felsenstein 1985 ) .
At least four approaches allow examination of possible fi shery implications of
fi shing spawning aggregations. The fi rst is to use information qualitatively across a
wide taxonomic range of species and determine whether those in which aggregations are specifi cally targeted have shown the most marked changes. The second is
to compare the fi sheries status of several aggregating species within a single multispecies fi shery, in which all species are exposed to similar fi shing profi les and show
general biological similarities yet exhibit different degrees of aggregating behaviour
and extent of targeting of aggregations. A third approach, and one that addresses
phylogenetic issues, is to select a single lineage that has both aggregating and nonaggregating species and examine fi shery or conservation status by species. The
fourth involves a comparison of the fi shing history of a single aggregating species
among locations or populations, ranging from situations where its aggregations are
targeted and make a signifi cant contribution to annual landings to those where
aggregations contribute little to the overall fi shery. While none of these four
approaches entirely avoids possible confounding factors of life history differences,
relatedness or the relative importance of non-aggregation fi shing, examining the
question from different perspectives at least provides a semi-quantitative means of