SHARKS: ESSENTIAL IN THE OCEANS
Currently, they are the most endangered species in the Red List of the IUCN (http://www.iucn.org/).
Large sharks populations have been reduced up to 90% in the last 50 years, with 100 million sharks killed by humans every year. Spain captures half of all the sharks caught in the EU, which makes it the third country in the world in number of catches.
TOP OF THE FOOD CHAIN
A food chain is a linear system in which each individual feeds on the previous level and serves as food for the next one up. A food web is a set of interconnected food chains.
Several trophic levels are distinguished:
· Solar Energy.
· First level: primary producers such as fitoplankton, algae and marine plants. And primary consumers, such as zooplancton, among others.
· Second level: formed by the secundary consumers that eat primary consumers.
· Third level: is occupied by tertiary consumers that eat secundary consumers.
· Fourth level: top predators, such as Sharks.
Also as part of the chain we have the decomposers, which are responsible for the recycling of matter. Thus, each species plays an important role in the food chain; if a level was to be lost (extinction of some species) the whole system would be out of balance.
Shark fishing mainly aims for the fins, due to an increased consumption in Asian cuisine, where they are considered a luxury dish. To get the fins, fishermen do what is called “Shark Finning”, which is to capture the animals, cut their fins and then throw them back into the ocean still alive, they then fall to the bottom since they are unable to swim. They suffocate (as they need to swim to breathe) or are eaten by other fish, in terrible pain. They are also fished for their meat, cartilage and liver oil. Others are captured as bycatch.
Due to the considerable increase in shark captures, they are very vulnerable to human exploitation. They grow slowly and have a late maturation, which means they recover slowly from their downturn. Also many species have long gestation periods and give birth to few offspring. Their biological characteristics don’t allow Sharks to recover at the same rate as they are captured, so there is a decline in populations worldwide, having a cascading effect on other species.
KEEP OCEANS HEALTHY
Numerous scientific studies show that sharks are “key” species to the ecosystem, which means that a population decline or deletion will cause a collapse of the entire structure. We are already seeing today the decline of fish, shellfish and seaweed.
Their disappearance would severely damage the balance of the oceans, since they contribute to maintain.
The food chain in ecological balance: They tend to feed on their prey efficiently. Sharksmaintain diversity by feeding on abundant species, not allowing them to overpopulate and cause damage to the ecosystem.
The balance between corals and algae: They avoid overgrazing of algae’s vital habitats. The disappearance of sharks promotes the increase of the population of fish that prey on smaller fish species that live on the reef. Small planktonic fish have a key role in reef health as they feed on algae, balancing the conquest of space between corals and algae.
Their demise would favour an increase in algae that invade the space now occupied by corals. Losing coral areas reduces space for biodiversity and shelter for different species.
Healthy prey populations: sharks elect sick, slower or older fish because they are easier to catch. This keeps the population healthy, since it prevents the spread of diseases and averts outbreaks. The genetics of the prey are also strengthened, since the larger, healthier and stronger individuals are the ones that produce offspring.
The result is an increased number of healthy fish in the prey population.
Some sharks assist scavengers in getting food due to not eating the entirety of their prey. Other species act directly as scavengers, feeding on corpses and thus clearing the seabed.
A WORLD WITHOUT SHARKS
It is now the key moment to start considering whether we can live in a world withoutsharks in the oceans and seas. As a species, we need healthy oceans to survive, since, among other things, they provides much of the oxygen we need.
The disappearance of sharks would unbalance the whole system, directly affecting us.
It is up to us to realise how important these animals are and to seek alternatives to ensure their survival, which dates back over 450 million years.
Míriam Gil. Nakawe Education.