Fishing

 

The Port River Dolphins use many different techniques to catch their fish including surface fishing, bottom feeding, Kick fishing (using their tails to stun the fish) and fish throwing. We often see the dolphins racing along the sides of moored boats, the marinas, wharves and the rocks. Sometimes they are racing back and forth chasing after a fish, other times they are using the movement of the water to locate and flush out garfish and other small fish that may be hiding.

An adult dolphin eats approximately 8-15Kg of fish per day. Dolphins do not usually chew their fish they swallow the fish whole, head first. Like all mammals dolphins need fresh water to survive. They do not drink water like we do but obtain water from the fish they catch.
Dolphins use echolocation to locate their food. Echolocation is when a dolphin releases a sequence of clicks or whistles and then analyses the returning echo to determine the size, shape, distance, direction, speed and even the density of an object.

The Port River Dolphins use many different techniques to catch their fish including surface fishing, bottom feeding, Kick fishing (using their tails to stun the fish) and fish throwing. Dolphins often work together when fishing and some of the dolphins will circle a school of fish while the others race in to grab the fish.

Birds will also often feed with the dolphins. Particularly when they are surface fishing and the fish are jumping out of the water trying to escape from the dolphin (See Birds and Dolphins).

We often see the dolphins racing along the sides of moored boats, the marinas, wharves and the rocks.  Sometimes they are racing back and forth chasing after a fish, other times they are using the movement of the water to locate and flush out garfish and other small fish that may be hiding. One dolphin named Unhap often waits near a submerged fence and as the Brim swim past he races towards them herding them against the fence.

Dolphins will often play with their food, I have regularly observed our port river dolphins throwing the fish and jelly fish they have caught into the air and then chasing after them.

Around the world people have observed many remarkable techniques that dolphins use to catch fish. These include “sponging“Sponging” – Using sea sponges as a foraging tool. The dolphins carry the sponges on their rostra. It is thought that the sponge is used for protection from sharp objects on the floor of the ocean when the dolphins are foraging. ”, “conching“Conching” – Using conch shells as a tool to catch fish. ”, “hydroplaning“Hydroplaning” – Dolphins race towards the beach and use the momentum to push themselves through the shallow water up onto the beach. This enables them to catch fish that are swimming in water that is only a 5-10cm deep. ”, using sand and silt as a barrier Dolphins have been observed swimming in a circle beating their tail on the bottom of the sea floor. This stirs up the sand and silt creating a barrier around a school of fish. and even helping and cooperating with fishermenOn the south coast of Brazil Dolphins have been helping humans catch fish for several years. The fishermen stand on the shore with their nets and wait for the dolphins to herd schools of mullet towards the beach. The fish that escape the fishermen’s nets swim away from the shore straight in to the mouths of the waiting dolphins. . Many of these techniques are very impressive and are clear examples of why dolphins are one of the most intelligent animals on earth.

 

Links to articles on fishing techniques

http://news.sciencemag.org/sciencenow/2011/07/why-dolphins-wear-sponges.html
http://www.wired.com/wiredscience/2011/08/dolphin-fishing/
http://reeftools.com/news/hydroplaning-dolphins-fish-in-shallow-water/#
http://www.youtube.com/watch?v=O6jKz3ogE50
http://news.discovery.com/animals/helpful-dolphins-120502.html



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