The Philippines are a part of the coral triangle, the global epicenter of marine biodiversity. We are blessed with a great number of species of corals, sea slugs, and fishes. There are a few fish families which are particularly species rich – one of them are the cardinalfishes. Fishbase lists 352 species, the majority of which are found in the tropical Pacific Ocean.
They Like to Hide
If you swim over the field of staghorn corals just in front of Salaya, you will see cardinalfish hiding between the coral fingers; if you spot a large, black Diadema sea urchin, some clever cardinalfish might be hiding between its spines; and you will also find cardinalfishes in the sea-grass, next to fan-corals and under table coral ledges. During the day, these fishes tend to hide, and retreat deeper into the safety of their home urchin or coral if approached too carelessly by a diver. You will find cardinalfishes alone, in small groups or in large aggregations.
Things change at night, when the cardinals become active hunters. Their large eyes help them locate crabs and shrimps even in very dim light. They are quite successful hunters, and if you do a night dive with us, you will see many cardinalfish hovering just above the sand, moving slowly while on the lookout for prey.
I always found the resemblance between a small, big-eyed reef fish and an elderly holy man rather mild, but the common name of the Apogonidae (this is how scientists call the cardinalfishes) stems from the golden skin color of many cardinalfish species, resembling the color of a cardinal’s robe.
A very interesting strategy many cardinalfishes use when they reproduce is mouth-brooding. After fertilizing the female’s eggs, the male fish gulps them up, and keeps them safe in his mouth. There the eggs are so much safer from predation by other fishes than eggs laid on a rock. If a hungry egg-seeking fish approaches, the cardinalfish dad can simply swim away with his clutch.
It’s a great strategy, but …. there is always a BUT. The problem is that a mouth full of eggs keeps the male cardinalfish from eating. This severely limits how often it can take care of a clutch of eggs. During breeding season, the health and fat reserves of male cardinalfish go downhill. In some cases, especially when they are terribly starved towards the end of the cardinalfish breeding season, males even eat their own offspring by swallowing the mouth full of eggs they are meant to keep safe!
There are so many crazy, unusual and fascinating things happening underwater! Cardinalfish reproduction is certainly one of them.
Photographing the Cardinals
Lastly, how do you get good underwater photographs of cardinalfishes? As so often, a careful approach is paramount. If you take your time to get close to them and wait patiently, they will get accustomed to your presence. It’s not likely that these fishes will try to escape, but they will turn away from you, and retreat deeper into their hiding space. For interesting head-shots of cardinalfish, you need to wait and stay calm.