28 April 2010

Fish survey at Cyrene Reef

What fishes can be found on Cyrene Reef? Collin and his colleagues from NParks conduct regular surveys to find out!
Collin and Jeff do the hard work of seining for fishes.

Despite the Reef's location near major installations like Pulau Bukom, there is an amazing variety of fishes on this seagrassy and reefy shore.

In particular, Collin tags the Alligator pipefishes (Syngnathoides biaculeatus) that are commonly seen in a deep seagrassy pool on Cyrene Reef.
These fishes are tagged with a tiny little orange marker so that each fish can be differentiated and records kept for each one.
To tag it, a tiny bit of harmless dye is inserted gently into the outer skin.
Fishes are marked at different parts of their body so that they can be differentiated.
Here's one tagged in a different part of the body.

Collin measures the fish to see how much it has grown since he last measured it. This kind of study will reveal a lot about our fishes as we monitor tagged individuals over time.
Like their relatives the seahorse, it is the papa pipefish that carries the eggs. These are not kept inside a pouch but stuck to the bottom of his long belly.

A closer look at the little round eggs on papa's tummy.
 Like the seahorse, this pipefish also has a prehensile tail. That is, it can curl its tail to grasp things!
After gently tagging and measuring the fishes, they are released back into the deep pool.
The Alligator pipefish is very hard to spot when it is among the seagrasses!

Among the surprises that turn up in the survey is this strange fish with a 'beard'.It is the Bearded filefish (Anacanthus barbatus) which is a kind of filefish (Family Monacanthidae)!
Here is a closer look at its face. It is holding up the 'beard'
into a point under the tiny upturned mouth.
It has a long broad tail.

There are usually lots of filefishes in the pool! They are often well camouflaged. There are three different coloured filefishes in this photo, can you see them? The bright green one with the white smiley mark is probably the Seagrass filefish (Acreichthys tomentosus), while the darker one on the lower bottom of the photo is probably the commonly encountered Fan-bellied filefish (Monacanthus chinensis). Filefishes belong to Family Monacanthidae and get their common name because they have a rough skin that has the texture of a file. They are also sometimes called Leatherjackets for their tough skin.
This one is probably the Strapweed filefish (Pseudomonacanthus macrurus).

Other fishes aften encountered in the fish surveys include razofishes (Family Centriscidae). These fishes are often seen hanging vertically head down over hard corals. They are also known to be found among the spines of large sea urchins such as the Long-spined black sea urchins (Diadema sp). And now we know they are also found among seagrasses!
These well camouflaged Variable fang-blennies (Petroscirtes variabilis) can be common among the seagrasses at Cyrene.Other fishes encountered in the fish surveys include flatheads (Family Platycephalidae), rabbitfishes (Family Siganidae), tiny cardinalfishes (Family Apogonidae) and pufferfishes (Family Tetraodontidae).

The fish survey is not only useful to learn more about Cyrene, but also helps lucky visitors get a first hand look at the rich marinelife that can be seen in a good seagrass meadow. It's hard to see these well hidden fishes without seining for them!
Collin shares with some visitors at Cyrene about how the survey is conducted.

It's amazing what we can find in a vast seagrass meadow just off the main business district of Singapore!
Thanks to the hard work put in to the regular fish surveys at Cyrene Reef.

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