Gentle giants

Despite being the world’s largest fish species, we know relatively little about the life history of the whale shark including their migration patterns and where they give birth. 

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whale shark

Whale shark © Simon Pierce / Galápagos Conservation Trust

 

Whale sharks are currently listed as ‘endangered’ on the IUCN Red List due to threats such as fishing pressure and collisions with large vessels, but we really need to learn more about them in order to protect them effectively.

 

Whale sharks in Galápagos

Whale sharks visit the Galápagos Islands seasonally, preferring the north of the Archipelago, particularly favouring Darwin and Wolf islands. The majority of individuals visiting Galápagos are mature females, 90 per cent of which are though to be pregnant, though this is yet to be proven.

Galápagos Conservation Trust (GCT) has supported the Galápagos Whale Shark Project for several years, the aim of which is to find out why the Galápagos Marine reserve is so important for this species, and learn more about their migration patterns through satellite tracking.

 

A whale shark being tagged © Simon Pierce / Galápagos Conservation Trust

 

Whale shark highways

New research from this project has given some interesting insights into how whale sharks feed and move in the area around the Galápagos Marine Reserve. By tracking 27 whale sharks throughout the Eastern Tropical Pacific and comparing this to environmental data, the team were able to show that whale sharks spend most of their time in this area travelling along fronts – the dynamic boundaries between warm and cold ocean waters.

There is a distinct boundary across the Eastern Pacific that separates the warm water north of the equator and colder water south of the equator, which the whale sharks are following almost like a highway.

This boundary, which also runs through Darwin’s Arch where the project team satellite tag whale sharks in Galápagos, seems to provide a perfect balance between food availability and temperatures for foraging activities. The cooler, nutrient rich waters provide plenty of zooplankton, the main food for whale sharks. On this boundary, these cold waters are warmed by the downward moving, upper layers of sea, which means that whale sharks feeding here need less energy to regulate their body temperature.

 

Why is this important?

It gives an insight into the ecology of the whale shark, which will allow better protection of this endangered species. By knowing where the sharks are feeding, conservation strategies can be further developed to protect these areas, and scientists now have an area on which to focus their efforts to gain better estimates of the whale shark population and more insights into the biology of this large, but elusive giant. 

 

Click here to find out more about the Galápagos Whale Shark Project 

Read the full paper in Plos One

 

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