Yellowheaded jawfish

The yellowheaded jawfish in the reef aquarium are very industrious diggers of burrows, which they reinforce using pebbles. They can frequently be observed working on their burrows, shoveling out mouthfuls of sand and stealing pebbles from their neighbors.

Jawfish seldom stray far from the protection of their burrows, spending most of their time hovering at the mouths of their burrows waiting to snatch passing plankton. In the evening they retreat into their burrows for the night, using several large pebbles to cover the burrow opening to conceal it from nighttime predators.

Other organisms in photo:

• Next to the burrows (at left center of photo) is a brown encrusting gorgonian colony.
• Behind and to the right of the jawfish is a large open brain coral.
• Above this coral is a male Banggai cardinal fish (facing away from the camera). Another view of this black and white striped fish can be seen just to the right of the center of the main Coral reef aquarium photo.
• In the left foreground is a colony of brown zooanthid anemones being overgrown by a sponge.

The diverse spawning behaviors of reef fish:
Jawfish and Banggai cardinal fish exhibit interesting breeding behaviors, which must be put into context to be fully appreciated.

• Most marine fish (and also most marine invertebrates) release sperm and eggs into the water. Eggs and larval fish drift in the water currents. These larvae often look nothing like the adults. They live a planktonic existence for a few weeks or months, before undergoing a physical transformation that changes them into miniature versions of the adults. Once this metamorphosis has taken place, the young fish seek out a suitable reef habitat where they will settle down and start living a lifestyle more typical of adults of their species.
• Clownfish and damselfish (such as our green chromis), however, attach their eggs to rocks, defending them from predators and keeping them clean until they hatch. The larval fish are then planktonic as described above.
• Male jawfish, on the other hand, carry their eggs in their mouths until they hatch, at which point the larval jawfish live a planktonic existence for awhile.
• Banggai cardinalfish males also carry their eggs in their mouths, but their eggs are very large. Consequently, the young are also very large and look like miniature adults upon hatching, and they spend no time drifting as plankton before settling into the seagrass beds where they will spend the rest of their lives. As a result, this species does not disperse to new areas very well, and in the wild it is only found in the vicinity of the Banggai islands near Sulawesi. Fortunately, these fish reproduce quite readily in captivity, and our pair is captive bred.

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