Written by Marco Quesada, Director of Conservation Internacional Costa Rica
The loss of predators greatly affects the functioning of marine ecosystems. Healthy ecosystems can not exist without predators.
Costa Rica to advance implementation of measures to discourage the shark trade. National and public interests of our country must promote sustainable fishing practices that ensure our food and environmental security.
Sharks and bycatch
A new study from the University of Miami on the vulnerability of twelve species of shark that are by-catch (caught unintentionally) in longline fishing lines shows that species have very different rates of survival once captured. In other words, some species die faster than others.
The study examined more than ten years of data and studied the effects of the depth and duration of the line in the water, the water temperature and the size of the animal, among other things, on the survival of sharks. It was determined that, among the species with the lowest survival rate being incidentally caught in fishing lines, are hammerhead and thresher sharks. Both species are often captured by poachers in Cocos Island.
Hammerheads have a very low survival rates after being captured.
This means that rangers have a low chance of rescuing alive these species when they are caught by illegal fishing gear within the protected area. This information, therefore, strengthens the need for control and surveillance in Cocos Island and for a zero tolerance policy to fishing gear within the National Park.
Predators and health of the oceans
The loss of predators greatly affects the functioning of marine ecosystems. In the absence of hunters to keep the prey populations in check, it is possible that the usual prey of the big fish begin to abound. From here, the whole food chain will be affected, in some cases altering the very chemistry of our oceans.
When a particular population begins to grow beyond what the ecosystem can sustain the species that feeds this population will begin to dwindle. Less predators, more prey. More prey, less food for that prey. This cascade effect causes a change in the ecosystem. They often become more fragile to environmental changes such as pollution or increased water temperature.
Conservation International partners such as Misión Tiburón have found that some coastal fishing gear catches juvenile hammerhead sharks and that they die fast. CIMAR too, through a project with CI, has determined that the bycatch of sharks and rays in shrimp trawls is high and that these animals, especially juveniles, are discarded at sea. These are negative impacts that we must correct.
We are working so that Costa Rica encourages sustainable fishing practices to ensure food and environmental security for our country. This is accomplished by placing limits to the total catches by species, reducing the maximum catch of marine species and preserving key ecosystems.
Beyond its beauty, sharks are a key element of marine ecosystems. Equally important are other predators that we like to have in our meals: snappers, groupers and croakers. Costa Rica must devise a national strategy, not sectoral, to preserve and exploit the sea. We should implement measures to prevent trade of species such as shark.
Conservation International works tirelessly to protect critical ecosystems such as mangroves and reefs, to incentive good practices within artisanal fisheries and to strengthen control and surveillance of our seas in order to reduce illegal, unreported and unregulated fishing.