272
Y. Sadovy de Mitcheson and B. Erisman
8.7.2 Fisheries Effects of Various Management Policies
It is important to document or model how various forms of management or protection of aggregations can generate increased revenue to fi sheries in the long term, to
track successes and failures following management, and to understand fi sher
responses following protection. Nemeth ( 2005 ) demonstrated that closure of spawning aggregations for red hind led to increased aggregation densities as well as
increased the number and average length of red hind in adjacent fi sheries. Likewise,
the banning of commercial gillnets on the spawning grounds of white seabass is
correlated with a recent increase in CPUE and catch of commercial fi sheries in
California (Allen et al. 2007 ) .
Other possible management models could also be explored, such as pulse fi shing or
rotational closures (e.g. Graham 2001 ) . However, while in principle complex management approaches might make sense on paper, the reality of management capacity usually precludes such approaches and calls for more conservative and simple measures.
8.7.3 Fisheries-Independent Surveys and Underwater
Monitoring of Aggregations
Direct surveys of aggregation sites are necessary to validate the existence of spawning aggregations, estimate fi sh abundance and monitor the timing and duration of
aggregations. The evaluation of these and other characteristics (e.g. catchment
areas, larval connectivity) of aggregations is necessary because fi sheries landings
and CPUE data often do not accurately refl ect the status of stocks for aggregating
species due to the problem of hyperstability (Chap. 11 , Sect. 8.3 ). Certain aggregation sites pose serious challenges for monitoring due to their remote locations, poor
visibility for diving, strong currents, or other factors. Increased utilization of multibeam hydroacoustic surveys and other new technologies show considerable promise
for surveying aggregation sites. However, hydroacoustic surveys are unreliable
unless carefully ground-truthed (Chap. 9 ).
8.7.4 The Economics of Aggregation Fisheries
Economic assessments of aggregation fi sheries and alternative uses of aggregations
are important because economics drive natural resource use practices and policies,
in which gains or losses in revenues rather than ecosystem health impart the greatest
infl uence on decision-makers. Appreciation of the overall and long-term economic
value of the fi shery production supported specifi cally by aggregations, as well as
economic implications of their losses, can come through fi shery modelling combined with economic data and biological information. This requires data on the
Y. Sadovy de Mitcheson and B. Erisman
8.7.2 Fisheries Effects of Various Management Policies
It is important to document or model how various forms of management or protection of aggregations can generate increased revenue to fi sheries in the long term, to
track successes and failures following management, and to understand fi sher
responses following protection. Nemeth ( 2005 ) demonstrated that closure of spawning aggregations for red hind led to increased aggregation densities as well as
increased the number and average length of red hind in adjacent fi sheries. Likewise,
the banning of commercial gillnets on the spawning grounds of white seabass is
correlated with a recent increase in CPUE and catch of commercial fi sheries in
California (Allen et al. 2007 ) .
Other possible management models could also be explored, such as pulse fi shing or
rotational closures (e.g. Graham 2001 ) . However, while in principle complex management approaches might make sense on paper, the reality of management capacity usually precludes such approaches and calls for more conservative and simple measures.
8.7.3 Fisheries-Independent Surveys and Underwater
Monitoring of Aggregations
Direct surveys of aggregation sites are necessary to validate the existence of spawning aggregations, estimate fi sh abundance and monitor the timing and duration of
aggregations. The evaluation of these and other characteristics (e.g. catchment
areas, larval connectivity) of aggregations is necessary because fi sheries landings
and CPUE data often do not accurately refl ect the status of stocks for aggregating
species due to the problem of hyperstability (Chap. 11 , Sect. 8.3 ). Certain aggregation sites pose serious challenges for monitoring due to their remote locations, poor
visibility for diving, strong currents, or other factors. Increased utilization of multibeam hydroacoustic surveys and other new technologies show considerable promise
for surveying aggregation sites. However, hydroacoustic surveys are unreliable
unless carefully ground-truthed (Chap. 9 ).
8.7.4 The Economics of Aggregation Fisheries
Economic assessments of aggregation fi sheries and alternative uses of aggregations
are important because economics drive natural resource use practices and policies,
in which gains or losses in revenues rather than ecosystem health impart the greatest
infl uence on decision-makers. Appreciation of the overall and long-term economic
value of the fi shery production supported specifi cally by aggregations, as well as
economic implications of their losses, can come through fi shery modelling combined with economic data and biological information. This requires data on the