434
Sea turtles are threatened by direct harvest both in offshore habitats and on nesting beaches, from egg to adult stages. Adult green turtles were intensively harvested
for their meat in the 1880s (Valverde and Holzwart 2017) when landings of that
species alone are estimated at 4800 to 6000 animals per year, across the GOM and
broader Caribbean (Darnell 2015). Adult loggerheads were harvested in Cuba
through the mid-1990s (Gavilan 1998). Harvesting of sea turtles became illegal in
the United States under the Endangered Species Act of 1973, and illegal poaching
at sea is thought to be rare in the US Gulf of Mexico (NMFS 2011). However, active
harvest may still occur outside of the US EEZ. An active illegal trade in hawksbill
tortoiseshells persists (NOAA 2013). Poaching of sea turtle eggs from nesting sites
continues in the United States and neighboring countries (NMFS 2008, 2011).
26.2.2 Shipping and Vessel Strikes
Commercial shipping has been a major industry in the GOM since the 1850s, when
the port of New Orleans was the second largest in the country (Darnell 2015). In
2016, GOM ports accounted for nearly 50% of total tonnage transferred through
American ports (US Army Corps of Engineers). Both marine mammals and sea
turtles are at risk of vessel strikes, and these are likely highly underreported for
pelagic species (Williams et al. 2011; Epperly et al. 1996).
26.2.3 Anthropogenic Noise
Offshore human activities also affect megafauna through elevated noise levels and
pollution. Oil and gas development took hold in the GOM in 1947 (Darnell 2015),
expanding rapidly thereafter. In 2018 over 50 thousand wells and 7 thousand drilling platforms were documented in the GOM (BOEM 2018). Seismic surveys using
explosive sound sources (airguns) are used to map subsurface oil and gas deposits.
These surveys are nearly continuous in the GOM, and they combine with shipping
noise to make average low-frequency ambient noise levels very high in the GOM
relative to levels in other ocean regions (Wiggins et al. 2016). Noise is considered a
chronic stressor for marine mammals because these species rely on sound to interpret their environment and communicate with one another (e.g., Wright et al. 2007).
26.2.4 Debris Entanglement, Ingestion, and Bycatch
Commercial fishing efforts in the GOM expanded after WWII, adopting novel technologies including purse seines, longlines, trawls, and gillnets, which increased the
occurrence of marine mammal and sea turtle entanglement in fishing gear (Lutcavage
K. E. Frasier et al.
Sea turtles are threatened by direct harvest both in offshore habitats and on nesting beaches, from egg to adult stages. Adult green turtles were intensively harvested
for their meat in the 1880s (Valverde and Holzwart 2017) when landings of that
species alone are estimated at 4800 to 6000 animals per year, across the GOM and
broader Caribbean (Darnell 2015). Adult loggerheads were harvested in Cuba
through the mid-1990s (Gavilan 1998). Harvesting of sea turtles became illegal in
the United States under the Endangered Species Act of 1973, and illegal poaching
at sea is thought to be rare in the US Gulf of Mexico (NMFS 2011). However, active
harvest may still occur outside of the US EEZ. An active illegal trade in hawksbill
tortoiseshells persists (NOAA 2013). Poaching of sea turtle eggs from nesting sites
continues in the United States and neighboring countries (NMFS 2008, 2011).
26.2.2 Shipping and Vessel Strikes
Commercial shipping has been a major industry in the GOM since the 1850s, when
the port of New Orleans was the second largest in the country (Darnell 2015). In
2016, GOM ports accounted for nearly 50% of total tonnage transferred through
American ports (US Army Corps of Engineers). Both marine mammals and sea
turtles are at risk of vessel strikes, and these are likely highly underreported for
pelagic species (Williams et al. 2011; Epperly et al. 1996).
26.2.3 Anthropogenic Noise
Offshore human activities also affect megafauna through elevated noise levels and
pollution. Oil and gas development took hold in the GOM in 1947 (Darnell 2015),
expanding rapidly thereafter. In 2018 over 50 thousand wells and 7 thousand drilling platforms were documented in the GOM (BOEM 2018). Seismic surveys using
explosive sound sources (airguns) are used to map subsurface oil and gas deposits.
These surveys are nearly continuous in the GOM, and they combine with shipping
noise to make average low-frequency ambient noise levels very high in the GOM
relative to levels in other ocean regions (Wiggins et al. 2016). Noise is considered a
chronic stressor for marine mammals because these species rely on sound to interpret their environment and communicate with one another (e.g., Wright et al. 2007).
26.2.4 Debris Entanglement, Ingestion, and Bycatch
Commercial fishing efforts in the GOM expanded after WWII, adopting novel technologies including purse seines, longlines, trawls, and gillnets, which increased the
occurrence of marine mammal and sea turtle entanglement in fishing gear (Lutcavage
K. E. Frasier et al.