During this phase, it has been observed that some species of fish undergo a change in behavior. There is data that shows a reduction in catches of different species of fish as a direct result of seismic surveys in nearby areas. For example, studies in the North Sea estimated a reduction in abundance of some fish stocks compared to those that existed in the area before the seismic activity. The abundance of these populations decreased by 36% for demersal species, 54% for pelagic species and 13% for small pelagics. Especially vulnerable are fry and larvae, placed with minimum capacity to escape.
Surveys planned in these areas also threaten the areas proposed by Ecologists in Action (Ecologistas en Acción), GOB, Greenpeace and WWF / Adena, as sanctuaries for Bluefin Tuna fishing, a species in danger of extinction.
It is essential that we recognise the environmental and economic impacts that oil exploration and exploitation can have on the fisheries, an economic activity that provides important local and national social and economic benefits.
Drilling and Exploitation
Sludge compaction (used to put pressure on the stock oil as a lubricant for drilling or drills to reinforce the walls of the well) contains quantities of hazardous chemicals such as barium sulfate, heavy metals and polycyclic aromatic compounds. Furthermore, these processes utlise toxic injection of dispersants, corrosion inhibitors and biocides. Coupled with leaks of hydrocarbons (concentrations in the vicinity of the platforms can be up to thousands of times higher than normal) these processes generate a chronic pollution that can enter the food chain, resulting in problems for ecosystems and also for human consumption of seafood.
In the case of an accidental oil spill, the chemoreceptors of many marine species detect oil in the water and vary their migrations and movements, eventually disappearing and never returning to the location. Oil is deposited on the seabed, killing or causing sublethal effects in thousands of animals and plants vital to the ecosystem. Seafloor and bank algae are covered by a thin oily film that hinders photosynthesis and reproduction. Sublethal effects on marine animals may include deformities, loss of fertility, reducing the level of hatching eggs, alterations in behavior and varied effects from the toxicity of the spill.
After the oil disappears from the surface, the water presents a false ‘clean’ appearance, crystal clear due to the death of phytoplankton and marine life which normally ‘muddies’ the water. Phytoplankton are at the very basis of the diet of the larvae of commercial species such as sardines or tuna, for example, so the impact would be devastating.