Tuesday, February 22, 2011

Red Sea Expedition: How far do fish move?

It is a great pleasure to introduce the first of a series of excellent guest bloggers who I have been working and diving with here at KAUST, in Saudi Arabia. While I am here examining the nutritional basis of corallivory, Lizzie is busily gearing up for an ambitious and important project that will examine the movement of adult reef fishes.

Dr. Lizzie Tyler is a postdoctoral researcher at King Abdullah University of Science and Technology (KAUST) in Saudi Arabia. She is studying the movement of coral reef fish in the Red Sea. She gained her doctoral degree from Oxford University in the UK, where she worked on marine reserves in Zanzibar, East Africa.


From Lizzie:

Marine reserves, areas in the sea which are closed to fishing or other human activities, are becoming an increasingly popular method for conserving the ocean and managing fish stocks. However, to understand how effective they are at protecting different fish, we need to know how far these fish move--or rather swim!

Coral reefs are rich in species, and fascinating to biologists and SCUBA divers, but they also provide important food fish. Here in Saudi Arabia, grouper or hammour is a prized food, especially the Nagil grouper (Plectorhinchus pessuliferus)

A 70 cm long Nagil we caught and successfully released.

In Dr. Michael Berumen’s Coral Reef Ecology lab here at KAUST, we are generally interested in how connected coral reefs are, that is, the extent to which any two reefs share juvenile or adult corals and fish.

If we protect a reef from fishing, we want to know what proportion of time our fish will spend on the protected reef, and whether they are likely to move to other reefs that are still being fished. This movement may be good: providing a supply of fish that have increased inside the protected reef to fishermen on other reefs. This movement may also help to maintain important processes on reefs where fish populations are low. For example, parrotfish are avid grazers, eating algae and dead coral and providing clean rock surfaces for juvenile corals to establish and grow.

Parrotfish in the fish market in Jeddah, Saudi Arabia.

Parrotfish are commonly caught, but are important grazers on coral reefs and if they move between reefs, they can graze on reefs that have been heavily fished, keeping them healthy.

My project focuses on measuring adult reef fish movement. We will be implanting small tags inside the stomach cavity of different fish species. These tags transmit a loud noise, at a very high frequency (above the hearing range of all marine animals).

To listen for these tags, we will place several receivers underwater on different reefs, which will remain stationary. Each tag inside a fish transmits a unique code, which is identified by the receiver. By looking at which receivers have heard which tags, we can map where fish have traveled.

An acoustic receiver being attached to a mooring line.
The receiver will be left there to listen for tags and later removed to download the stored data.

The challenging part of this project is that it requires us to be both fishermen and vets, since we need to capture fish successfully, without harming them, and then perform surgery under anaesthetic to insert the tag before they are released.

Inserting an acoustic tag in the stomach cavity of an emperor fish during surgery.
The fish are kept alive with water pumped over their gills containing anaesthetic.

A small tooth emperor (Lethrinus microdon), just released back on to the reef after surgery
(you can see the stitches on the belly!)

We hope that the results of our project will be used to help design marine reserves both in Saudi Arabia and on other coral reefs around the world. Wish us luck with the fishing!


1 comment:

  1. Really interesting post, thanks! Do you think that fish might move to find more food? Or maybe to find mates?