Aquatic Wildlife, Amazon

Back on the boat, the next point of focus in the animal realm was the aquatic species. Marine wildlife is abundant in the many rivers and tributaries of the Amazon. There are more than 3,000 species, from turtles, dolphins, caimans, and giant otters to the weird and fascinating electric eel and Arapaima.

But I wondered what it is about the Amazon environment that breeds and produces such large quantities of species. It seems to be a variety of reasons. As mentioned at the beginning, the river is the largest in the world by volume. It carries more water than the next seven largest rivers combined. As such, the river system creates a huge network of interconnected habitats, providing different spots for aquatic species to inhabit and thrive. It is also nutrient-rich due to the sediment and organic matter flowing through the river.

The rainforest canopy helps regulate the water temperature providing shade, shelter and protection from predators. Then there are the floodplains. The seasonal flood cycle inundates massive forest areas, creating temporary pools and ponds rich in nutrients that support many species.

Let me tell you about some iconic species starting with the Arapaima. Native to the Amazon, the Arapaima has been around for over 20 million years and is often called a "living fossil". Growing up to 9ft (2.7m) in length and weighing up to 220lb (100kg), it is one of the largest freshwater fish in the world. With the ability to breathe air, it tends to be found in slow-moving, oxygen-deficient rivers and can survive outside of water for nearly 24 hours. Arapaima is a mouthbrooder, meaning the male scoops up the eggs, carries them until they hatch, and then holds the fry in its mouth for several weeks, protecting them from predators. The arapaima is an important food source for the indigenous communities. It is also prized in the fish trade, making them vulnerable to overfishing.

Another fascinating creature is the piranha. Often depicted in Hollywood movies as devouring people, these aggressive sharp-toothed fish do not threaten humans and tend to avoid areas where they are present. Actually, piranhas are more interested in nipping at the tail of larger fish, which makes up a good portion of their diet. While they are primarily carnivorous, they are also known to eat plants and fruit that fall into the water, making them omnivorous. Despite their small size, piranhas have a powerful bite that can crush and shred their prey. They are also fiercely territorial and use a variety of vocalizations, such as clicking noises, and displays, such as fin flaring, to communicate with each other and establish dominance.

I'll tell you about the Amazon River dolphin in my next letter.