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Did You See That? The Art of Observing Marine Life

By Marty Snyderman

The fish, a spectacularly colored grouper, paused and opened its mouth. Finning only slightly to maintain its position just a foot (30 cm) or so above the reef, this brightly colored red and blue-spotted grouper waited patiently for another fish, a cleaner wrasse, to provide its services. Within only a few seconds the cleaner approached and went to work, moving from the tail toward the head along the grouper’s body. The cleaner paused every few seconds to pick at the skin of the grouper.

Like other cleaner species, cleaner wrasses help rid groupers and other host animals of irritating ectoparasites that can be found on the skin of the hosts. In doing so the cleaners gain a meal while the host benefits by getting cleaned.

My dive buddy and I followed the grouper as it slowly moved down the reef. We watched as another fish, the same general size and shape as the cleaner wrasse, appeared. Looking quite confident that additional cleaning services were about to be rendered, the grouper paused and opened its mouth. In the blink of an eye, the fish I thought was a second cleaner wrasse swam up and bit a chunk of skin out of the side of the obviously startled grouper.

Clearly, the attacker was a mimic, a species that does a good enough job of imitating a cleaner species to fool groupers and other fishes into thinking the mimic is the real deal. It’s a risky business to try to fool well-equipped predators, but if well-done, the act of deceit can provide a mimic with a meal. If done badly, no more meals will be necessary. This mimic was a tiger blenny, a fact that, like the grouper, I realized only after the daring blenny had enjoyed its success.

After the dive I excitedly asked my diving buddy what she thought of the scene we had just witnessed, and much to my surprise, her only comment was, “that big fish sure is pretty.” At first I thought she was putting me on, but I soon realized that she had missed both the cleaning and the attack. She had noticed that the grouper had its mouth open rather wide, but she wasn’t sure why. She thought the fish might have been injured.

Observing marine life is like putting puzzle pieces together. When you look at one fish, you see only one piece of the puzzle. Yet when you connect the pieces — say a fish to its habitat and to other creatures within that habitat — you begin to see the inner workings of a marine ecosystem.

But how does one go from fish watcher to underwater naturalist? First, the more you dive, the more you will begin to see various subtleties, and the better observer you will become. You’ll find that your awareness of the underwater world increases with time, the number of dives and the variety of habitats you get to explore and enjoy. Second, it helps to learn about what’s going on under the waves so you are more likely to recognize the happenings that you encounter during your dives.

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