Sharks: The Ocean's Apex Predators and Their Fight for Survival
Sharks are among the most fascinating and ancient creatures of the ocean. They have existed for over 400 million years, far longer than dinosaurs. They belong to the class _Chondrichthyes_, distinguished from other fish by their cartilaginous skeletons. Today, approximately 1,000 species of sharks inhabit a wide range of environments, from shallow coastal waters to the deep ocean. They are classified within the superorder _Selachimorpha_, which includes all true sharks. Species vary greatly in size, from the small dwarf lantern shark, which grows to just about 20 centimeters, to the massive whale shark, which can reach lengths of up to 18–20 meters.
Sharks play a crucial role in maintaining the health and balance of marine ecosystems through several important ecological functions. One of their primary roles is population control. As apex predators, sharks regulate the abundance of their prey, preventing any single species from becoming overly dominant. Additionally, sharks impact the health of various marine habitats. By controlling the numbers of certain species, such as herbivorous fish, sharks help prevent the overgrazing of critical habitats like coral reefs and seagrass beds. In coral reef ecosystems, the presence of reef sharks helps control populations of smaller fish, such as parrotfish. Without these sharks, herbivorous fish could overgraze algae, which can degrade coral reefs.
Sharks also contribute to the health of prey species. By targeting weaker and sick individuals, sharks ensure that only the fittest members of prey populations reproduce. This process of natural selection promotes stronger and more resilient species, which is vital for the overall health and stability of marine ecosystems. Sharks further support nutrient cycling in marine ecosystems. By consuming prey and excreting waste, sharks recycle nutrients back into the environment, supporting the growth of other marine organisms.
Shark populations face significant threats, many stemming from human activities. One of the primary threats is overfishing. Recent studies estimate that between 63 and 273 million sharks are killed annually, with an average of around 100 million, though this figure continues to be debated and studied. Sharks are either directly targeted for their fins, meat, and other body parts or caught unintentionally as bycatch in commercial fisheries. The demand for shark fins, particularly for use in shark fin soup, has led to a practice known as finning. In this practice, sharks are captured, their fins are removed, and the rest of the body is discarded, often while the shark is still alive. Without their fins, sharks are unable to swim properly, leading to a slow and painful death.
As demand for shark products rises, their slow reproductive rate poses a critical issue. Many shark species mature late and produce relatively few offspring, meaning that populations cannot quickly recover once depleted. As a result, even moderate levels of overfishing can have devastating long-term impacts. Another significant threat is habitat loss. Sharks rely on diverse habitats, such as coral reefs, mangroves, and open oceans, for breeding, feeding, and shelter. However, coastal urbanization, pollution, destructive fishing practices, and climate change have degraded many of these environments.
In response to these threats, numerous international and local efforts have been initiated to protect shark populations. Countries like the United States and members of the European Union have enacted laws prohibiting shark finning in their waters, aiming to reduce shark mortality and encourage sustainable use. Banning the fishing of threatened shark species is also an important conservation effort. In Sri Lanka, for example, fishing for threatened species like the whale shark ( Minimuthu mora) oceanic whitetip shark (Polkola mora), and thresher sharks (Kasa mora) is prohibited.
The Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) regulates the global trade of endangered species, including shark species. As of 2022, nearly 100 species of sharks and rays are listed under CITES appendices, following significant additions at the 19th Conference of the Parties (CoP19). By controlling the trade of shark products, CITES helps reduce pressure on shark populations and encourages sustainable practices.
Sustainable fishing practices are also promoted to reduce shark bycatch, which is the unintentional capture of sharks during commercial fishing for other species. Selective fishing gear and implementing time and area closures help minimize shark bycatch. Additionally, catch limits and quotas for specific shark species vulnerable to overfishing help regulate populations and prevent extinction.
The establishment of Marine Protected Areas (MPAs) has become a crucial strategy in shark conservation. MPAs are designated regions where human activities, including fishing, are restricted providing safe havens for sharks and allowing their populations to recover. Notable examples include the Great Barrier Reef Marine Park in Australia and the GalÃĄpagos Marine Reserve in Ecuador. These protected zones help preserve shark species and the broader marine biodiversity they support.
Several countries have established shark sanctuaries, where shark fishing is prohibited. These sanctuaries, such as those in the Pacific (e.g., Palau and the Marshall Islands), offer a safe haven for shark populations to recover.
In conclusion, sharks are vital to marine ecosystems, helping regulate other species' populations and maintain ecological balance. Their role as apex predators, combined with their vulnerability to human activities, makes their conservation crucial for maintaining healthy ocean environments. Through continued international cooperation, improved fishing practices, and enhanced protection measures, we can work to ensure these ancient and remarkable creatures survive for future generations.
đDevmika Hapuarachchi
Second Year (21/22 batch)
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