684
the trawl. The fisheye is a device that provides the flatfish escape through an elliptical opening. Additionally, this BRD aims at the escape of pelagic juveniles through
the square meshes. Preliminary results show that this BRD reduces the 1:19 kg proportion to 1:9 kg, with an implementation cost of just 22 US$ per unit.
When fishery is regulated, fish populations, generally, respond with increased
production (King 2007). While fishing increases, mortality also increases, biomass
decreases and the low competition for resources among survivals prompts the population to respond with high population growth rates. If capture rate increases, the
biomass decreases until the fishing mortality stipulates the maximum sustainable
yield of a fish stock. If captures of smaller individuals continue, the trend is the
extinction of that stock. Estuarine landing data are thus necessary to identify
resources with greater vulnerability, higher resilience and more affordable sustainable yields.
20.5.3 Closure of Captures of Specific Stocks
By using scientific literature regarding the life cycle of fisheries resources, periods
of migrations and seasonality of abundance, government agencies (e.g. IBAMA,
ICMBio) is rich in rules for the sustainable exploitation of fish stocks in estuaries
and coastal adjacent water by the use closed periods (Castro et al. 2004; Barletta
et al. 2005, 2008; Silvano et al. 2006). This fisheries management strategy restricts
access of fishers to a specific location or times of the year. Closed periods are receiving attention and strength as an important short-term, emergency, management
option that help the recovery of fishery resources in Western Atlantic estuaries.
However, these will always remain palliatives unless more consistent actions don’t
follow and fail to restore environmental conditions (both biological and abiotic) to
guarantee support to stocks resilience. In addition, some other important measures
to guarantee the sustainable use of estuarine resources include no-take zones (associated to the spill-over principle), family or individual quotas for the capture of
common resources and efforts to reduce/eliminate untreated wastewater disposal
and to improve river flow quantity and quality. Closure is seldom applied to all
stocks at a time (complete exclusion zone), and difficult to inforce.
Considering the most captured fishery resource, the uça-crab, a study in the
Parnaíba Delta recorded that the capture per unit effort (CPUE) varied between 14.6
and 22.6 crab per picker per day from 1999 to 2002 (Legat et al. 2005). The total
monthly capture can exceed 2 million crabs when the CPUE is at its maximum,
producing up to 21 million crabs during the period of one year (Legat et al. 2005)
(Fig. 20.18). This is a strong evidence of over-exploitation and possible near collapse of uça-crab fishing if management options are not available quickly
(Fig. 20.18). Only recently, in 2014, it was decreed a closed period for the uçá-crab
in cycles of five days of interdiction and ten days of free catch from January to
March (BIOMADE 2015). Two federal environmental agencies are responsible for
the monitoring and surveillance, which occurs at Tatus port, the main access to the
M. Barletta et al.
the trawl. The fisheye is a device that provides the flatfish escape through an elliptical opening. Additionally, this BRD aims at the escape of pelagic juveniles through
the square meshes. Preliminary results show that this BRD reduces the 1:19 kg proportion to 1:9 kg, with an implementation cost of just 22 US$ per unit.
When fishery is regulated, fish populations, generally, respond with increased
production (King 2007). While fishing increases, mortality also increases, biomass
decreases and the low competition for resources among survivals prompts the population to respond with high population growth rates. If capture rate increases, the
biomass decreases until the fishing mortality stipulates the maximum sustainable
yield of a fish stock. If captures of smaller individuals continue, the trend is the
extinction of that stock. Estuarine landing data are thus necessary to identify
resources with greater vulnerability, higher resilience and more affordable sustainable yields.
20.5.3 Closure of Captures of Specific Stocks
By using scientific literature regarding the life cycle of fisheries resources, periods
of migrations and seasonality of abundance, government agencies (e.g. IBAMA,
ICMBio) is rich in rules for the sustainable exploitation of fish stocks in estuaries
and coastal adjacent water by the use closed periods (Castro et al. 2004; Barletta
et al. 2005, 2008; Silvano et al. 2006). This fisheries management strategy restricts
access of fishers to a specific location or times of the year. Closed periods are receiving attention and strength as an important short-term, emergency, management
option that help the recovery of fishery resources in Western Atlantic estuaries.
However, these will always remain palliatives unless more consistent actions don’t
follow and fail to restore environmental conditions (both biological and abiotic) to
guarantee support to stocks resilience. In addition, some other important measures
to guarantee the sustainable use of estuarine resources include no-take zones (associated to the spill-over principle), family or individual quotas for the capture of
common resources and efforts to reduce/eliminate untreated wastewater disposal
and to improve river flow quantity and quality. Closure is seldom applied to all
stocks at a time (complete exclusion zone), and difficult to inforce.
Considering the most captured fishery resource, the uça-crab, a study in the
Parnaíba Delta recorded that the capture per unit effort (CPUE) varied between 14.6
and 22.6 crab per picker per day from 1999 to 2002 (Legat et al. 2005). The total
monthly capture can exceed 2 million crabs when the CPUE is at its maximum,
producing up to 21 million crabs during the period of one year (Legat et al. 2005)
(Fig. 20.18). This is a strong evidence of over-exploitation and possible near collapse of uça-crab fishing if management options are not available quickly
(Fig. 20.18). Only recently, in 2014, it was decreed a closed period for the uçá-crab
in cycles of five days of interdiction and ten days of free catch from January to
March (BIOMADE 2015). Two federal environmental agencies are responsible for
the monitoring and surveillance, which occurs at Tatus port, the main access to the
M. Barletta et al.