Why Are Sharks and Whales Not in Rivers Anymore?

Sharks and Whales Not in Rivers: Why?

Here’s why sharks and whales are not in rivers anymore: Some sharks and smaller whale species can be found in rivers, but the majority avoid them. Due to pollution, aquatic constructions, boats, and fishing nets, whales and sharks try to stay away from coastal waters. Rivers can only be accessed from coastal waters. So if you want to learn all about sharks and whales and their connection to rivers, then this article is for you. Let’s jump right in! Why Are Sharks and Whales Not in Rivers Anymore? The natural flow of rivers has been compromised by humans in many ways, often making them uninhabitable for animals that need clear water and lots of food. Although some sharks and smaller whale species can be found in rivers, the majority avoid them. Large quantities of food are only available in oceans and seas, and sharks and whales need them to survive. Since they had no reason to go into freshwater over the centuries, their bodies adapted to the natural properties of saltwater only. Not only do the seas contain enough food for these predators, but the water also has properties that help them with infected wounds after fights with other predators. Whales and sharks try to stay away from the coastal sea and ocean waters due to pollution, aquatic constructions, boats, and fishing nets. Coastal waters are also the only places where they can get access to rivers. Why Are the Coastal Waters a Bad Environment for Sharks and Whales? A lot of physical pollution (garbage) and chemical pollution can be found in coastal freshwater and saltwater environments. The population of marine birds and fish are affected by this. They either swallow the contaminants or get caught in them. Animals are more likely to come across private and commercial boats in coastal waters. Animals are naturally frightened of human activities and tend to remain at safe distance. Different types of structures around coastal environments can disrupt the normal functioning of sharks and whale pods. Dams and bridges cut off essential food supplies, so marine animals tend to stay in open waters where there is more food. Many times, sharks and dolphins get caught up in fishing nets by accident. The animals are unaware of them and, once trapped, send signals to others of their kind to stay away. What Whales Can Live in Freshwater? The first type of whale that pops up in our minds when we mention these animals is probably the enormous blue whale. Along with 13 other large whale species, they form a group known as “Baleen whales.” Baleen whales swim slowly and open their mouths to randomly get food and water inside. Afterward, they push the water out through baleen plates where the food gets trapped (filtered) and swallowed. All Baleen species are unable to live in freshwater due to their size and the type of nutrition they need. A group of whales smaller in size are the toothed whales, which count almost 70 different species. Few of them can be found in freshwater. The biggest representative is the sperm whale, which is almost the size of the baleen species. While the feeding method of baleen whales is limited, the possibilities for toothed whales are vast. These possibilities mean that they can find food in many different habitats, including freshwater. Some toothed whale species can be found in lakes and rivers. At some point, though these environments are inadequate for them, they developed a few adaptations that made river trips possible. Few toothed whales have whiskers used to detect prey in muddy and murky rivers and lakes; also, they produce low-concentrated urine to keep the internal salinity stable. Toothed whales with the ability to inhabit freshwater can only be found in Asia and South America. These species include: South Asian river dolphin Indus river dolphin Irrawaddy dolphin Chinese river dolphin Amazon river dolphin Bolivian river dolphin Araguaian river dolphin Asian Freshwater Whales The one freshwater whale species no one is sure still exists is the Chinese river dolphin. In 1997, the species had 13 individuals, and the last sighting of such an animal was back in 2018. The endemic dolphin of the Yangtze River could be extinct as a result of electrofishing, habitat degradation, dam construction, and other human activity. On the south of the Asian continent, the Indus and south Asian river dolphins all have one thing in common – eyes the size of a pinhead, which make it possible for them to see in their muddy environment. South American Freshwater Whales All three species of South American freshwater whales (Amazon, Bolivian, and Araguaian) have long-toothed rostrums and are nearly blind. They inhabit several rivers in South America and get around using echolocation only. The Amazon River dolphin is the most abundant of the dolphins and shares its habitat (Amazon and Orinoco Rivers) with the tucuxi. The tucuxi are classified as oceanic dolphins that occasionally go into freshwater. Why Can’t Large Whales Live in Freshwater? First of all, the freshwater environment is too shallow for whales to live in. There is very little they can eat in that environment. Freshwater can also be easily polluted and become hazardous for whales. Whales share the ocean with marine animals that can live in freshwater, but they need different circumstances to survive. Over the years, whales and their prey biologically adapted to the properties of saltwater only. If a whale travels into a freshwater environment that’s naturally shallow, it risks getting stuck. Similar to when a whale gets trapped on a beach after the tide goes out, this is called “beaching.” Has Anyone Seen a Baleen Whale in a River? In 2020, three humpback whales, which belong to the group of baleen whales, have been spotted in the East Alligator River. The river belongs to the Kakadu National Park (Australia), and contrary to its name, it’s inhabited by crocodiles and not alligators. This was the first time a humpback whale was seen in a river. Before that, they …

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