254
Y. Sadovy de Mitcheson and B. Erisman
recreational fi shers (Sects. 8.2.2 and 8.2.3 ). Of 28 species reviewed, information on
aggregation behaviour was available for 10, mainly the largest (>1 m TL), species
that had the shortest reproductive seasons (Tuuli 2010 ) . In the Colorado River Delta
in the northern Gulf of California the totoaba and Gulf corvina ( Cynoscion othonopterus ) have undergone complete fi shery collapses and were the only species
known to form massive, dense, brief and highly localized aggregations at just a few
sites (Cisneros-Mata et al. 1995 ; Roman-Rodriguez 2000 ) . The totoaba was the fi rst
commercial marine food fi sh to be listed on Appendix I (1975) and is yet to recover.
In Australia, aggregation-fi shing appears to be the major reason for declines in the
mulloway and black jewfi sh (see above), and in China it was very likely the principal
factor leading to the threatened conservation status of the Chinese bahaba, and the large
yellow croaker (Sadovy and Cheung 2003 ; Liu and Sadovy de Mitcheson 2008 ) .
8.3.1.4 Approach Four – Spawning Aggregations Within a Species,
Geographic Variation in Fishing Intensity and Stock Condition
Fishery status can be compared for a single species among places or populations
where aggregations are subjected to different levels of fi shing pressure. To do this
we need (1) assessments of population status (either from fi shery stock assessment
or using some other indicator such as trends in body size or in CPUE) and (2)
monthly landings data or information that distinguish catches between spawning
and non-spawning seasons. Although more quantitative data are needed to identify
the effects of fi shing on aggregations versus impacts of fi shing on the stock as a
whole, available qualitative and quantitative information for the Nassau grouper
strongly suggests declines in fi sh sizes and numbers associated specifi cally with
aggregation-fi shing. For example, where aggregations have been protected
for a number of years and monitored, numbers are substantial or have stabilized
(e.g. Cayman Islands; Philippe Bush 2009), whereas where there has been little
effective protection aggregations are much reduced or no longer form (e.g. Belize,
Cuba, Puerto Rico and parts of Mexico) (Sadovy 1993 ; Aguilar-Perera 1994, 2007 ;
Sala et al. 2001 ; Heyman and Wade 2007 ; Claro et al. 2009 ) .
Since it is unlikely that more detailed assessments are forthcoming in the near
term, we propose that the indications from different Nassau grouper stocks, combined with the analyses in approaches 1–3 above, unequivocally call for a conservative approach to managing aggregation-fi sheries.
8.3.2 Effects of Gear Types and New Technologies
Access to and exploitation of spawning aggregations has become easier due to the
emergence of new technologies and more effective gear types. Devices such as
detailed fi shing charts, Geographic Information Systems (GIS), bathymetric maps,
sonar, and Global Positioning Systems (GPS) make aggregations less diffi cult
to fi nd, characterize, exploit, relocate, and communicate to others (Sadovy and
Y. Sadovy de Mitcheson and B. Erisman
recreational fi shers (Sects. 8.2.2 and 8.2.3 ). Of 28 species reviewed, information on
aggregation behaviour was available for 10, mainly the largest (>1 m TL), species
that had the shortest reproductive seasons (Tuuli 2010 ) . In the Colorado River Delta
in the northern Gulf of California the totoaba and Gulf corvina ( Cynoscion othonopterus ) have undergone complete fi shery collapses and were the only species
known to form massive, dense, brief and highly localized aggregations at just a few
sites (Cisneros-Mata et al. 1995 ; Roman-Rodriguez 2000 ) . The totoaba was the fi rst
commercial marine food fi sh to be listed on Appendix I (1975) and is yet to recover.
In Australia, aggregation-fi shing appears to be the major reason for declines in the
mulloway and black jewfi sh (see above), and in China it was very likely the principal
factor leading to the threatened conservation status of the Chinese bahaba, and the large
yellow croaker (Sadovy and Cheung 2003 ; Liu and Sadovy de Mitcheson 2008 ) .
8.3.1.4 Approach Four – Spawning Aggregations Within a Species,
Geographic Variation in Fishing Intensity and Stock Condition
Fishery status can be compared for a single species among places or populations
where aggregations are subjected to different levels of fi shing pressure. To do this
we need (1) assessments of population status (either from fi shery stock assessment
or using some other indicator such as trends in body size or in CPUE) and (2)
monthly landings data or information that distinguish catches between spawning
and non-spawning seasons. Although more quantitative data are needed to identify
the effects of fi shing on aggregations versus impacts of fi shing on the stock as a
whole, available qualitative and quantitative information for the Nassau grouper
strongly suggests declines in fi sh sizes and numbers associated specifi cally with
aggregation-fi shing. For example, where aggregations have been protected
for a number of years and monitored, numbers are substantial or have stabilized
(e.g. Cayman Islands; Philippe Bush 2009), whereas where there has been little
effective protection aggregations are much reduced or no longer form (e.g. Belize,
Cuba, Puerto Rico and parts of Mexico) (Sadovy 1993 ; Aguilar-Perera 1994, 2007 ;
Sala et al. 2001 ; Heyman and Wade 2007 ; Claro et al. 2009 ) .
Since it is unlikely that more detailed assessments are forthcoming in the near
term, we propose that the indications from different Nassau grouper stocks, combined with the analyses in approaches 1–3 above, unequivocally call for a conservative approach to managing aggregation-fi sheries.
8.3.2 Effects of Gear Types and New Technologies
Access to and exploitation of spawning aggregations has become easier due to the
emergence of new technologies and more effective gear types. Devices such as
detailed fi shing charts, Geographic Information Systems (GIS), bathymetric maps,
sonar, and Global Positioning Systems (GPS) make aggregations less diffi cult
to fi nd, characterize, exploit, relocate, and communicate to others (Sadovy and