426
on white shrimp spawners offshore and on pink shrimp juveniles in the nursery
areas in the early 1980s which added to the full developed offshore industrial fishing
effort. Gracia (1996) stated that the increase of selective artisanal fishing pressure
on white shrimp spawners led to recruitment overfishing affecting population
renewal. In the case of pink shrimp, the new artisanal was directed to juvenile even
under 2 months old (35 mm total length) in nursery grounds. Excessive fishing
effort resulted in growth overfishing and then affected the spawning stock biomass,
leading to recruitment overfishing.
Gracia (2004) stated that even though there could be many other factors affecting
the shrimp stock productivity in the Campeche Sound, the accumulated fishing
effort exerted on different shrimp life stages affected the shrimp reproductive potential and is the main factor driving shrimp fishery collapse. Signs of recoveries in
white shrimp stock occurred in 1986–1987 (Fig. 25.9) and were associated with
decreasing artisanal fishing effort combined with favorable environmental conditions (Gracia 1996). Although shrimp stocks have high resiliency, recurrent high
fishing by artisanal effort resulted in chronic recruitment overfishing episodes.
White and pink shrimp in the NGoM did not show clear impacts on yield preand post-DWH. White shrimp catch in the NGoM steadily increased in recent years;
coincidently, fishing effort has been reduced almost 50% (Hart and Nance 2013).
Much of the effort reduction was due to the impacts of Hurricane Katrina, which
destroyed many shrimp fishing vessels that were never replaced. Closing of almost
1/3 of the US exclusive economic zone due to the Deepwater Horizon oil spill also
reduced fishing effort on shrimp stocks. Estimates of white and pink shrimp spawning biomass show a steady increasing trend during the last few years. As well as
recruitment of white and pink shrimp has an increased trend. Spawning biomass and
recruitment fluctuations of both species are more likely due to the effect of environmental variations (Hart 2015a, b).
Shrimp reproductive strategy with early maturity, spawning along the year, high
fecundity, and two annual generations, which contribute to each other’s spawning,
make shrimp populations highly resilient to environmental or man-made stressors.
In both fisheries, but in an opposite way, fishing effort seems to be the principal factor that is affecting stock behavior. While in the NGoM reduced fishing effort is
allowing population rebuilding, in the SGoM high fishing effort maintains shrimp
stock in an overexploited condition.
25.7 Fishery Population Resiliency
One of the main concerns was the impact of oil spills on reproduction and population in early stages. Murawski et al. (2016) point out three important conditions that
affect significantly populations on its early life history: (1) exposure to oil results in
increased mortality and reduced fitness of animals exposed, (2) oil concentrations in
the environment are sufficient to cause increased mortality and sublethal
A. Gracia et al.
on white shrimp spawners offshore and on pink shrimp juveniles in the nursery
areas in the early 1980s which added to the full developed offshore industrial fishing
effort. Gracia (1996) stated that the increase of selective artisanal fishing pressure
on white shrimp spawners led to recruitment overfishing affecting population
renewal. In the case of pink shrimp, the new artisanal was directed to juvenile even
under 2 months old (35 mm total length) in nursery grounds. Excessive fishing
effort resulted in growth overfishing and then affected the spawning stock biomass,
leading to recruitment overfishing.
Gracia (2004) stated that even though there could be many other factors affecting
the shrimp stock productivity in the Campeche Sound, the accumulated fishing
effort exerted on different shrimp life stages affected the shrimp reproductive potential and is the main factor driving shrimp fishery collapse. Signs of recoveries in
white shrimp stock occurred in 1986–1987 (Fig. 25.9) and were associated with
decreasing artisanal fishing effort combined with favorable environmental conditions (Gracia 1996). Although shrimp stocks have high resiliency, recurrent high
fishing by artisanal effort resulted in chronic recruitment overfishing episodes.
White and pink shrimp in the NGoM did not show clear impacts on yield preand post-DWH. White shrimp catch in the NGoM steadily increased in recent years;
coincidently, fishing effort has been reduced almost 50% (Hart and Nance 2013).
Much of the effort reduction was due to the impacts of Hurricane Katrina, which
destroyed many shrimp fishing vessels that were never replaced. Closing of almost
1/3 of the US exclusive economic zone due to the Deepwater Horizon oil spill also
reduced fishing effort on shrimp stocks. Estimates of white and pink shrimp spawning biomass show a steady increasing trend during the last few years. As well as
recruitment of white and pink shrimp has an increased trend. Spawning biomass and
recruitment fluctuations of both species are more likely due to the effect of environmental variations (Hart 2015a, b).
Shrimp reproductive strategy with early maturity, spawning along the year, high
fecundity, and two annual generations, which contribute to each other’s spawning,
make shrimp populations highly resilient to environmental or man-made stressors.
In both fisheries, but in an opposite way, fishing effort seems to be the principal factor that is affecting stock behavior. While in the NGoM reduced fishing effort is
allowing population rebuilding, in the SGoM high fishing effort maintains shrimp
stock in an overexploited condition.
25.7 Fishery Population Resiliency
One of the main concerns was the impact of oil spills on reproduction and population in early stages. Murawski et al. (2016) point out three important conditions that
affect significantly populations on its early life history: (1) exposure to oil results in
increased mortality and reduced fitness of animals exposed, (2) oil concentrations in
the environment are sufficient to cause increased mortality and sublethal
A. Gracia et al.