My work as a marine biologist has taken me to dive sites in some of the most remote corners of the world. When I meet a scuba enthusiast, and he or she learns of my work, the conversation inevitably turns toward them asking me, "So what is your favorite place to dive?" To this, I always reply, "Wherever I am diving today." There are destinations on our watery planet that offer special opportunities to see rare and unusual sights, but what enthralls me most about the underwater world is that if you take time to look closely enough, wherever you are, something will happen that can captivate and amaze you.
The latest episode of UnderH2O, our PBS Digital Studios online series, is a great example of this. During a seemingly routine Saturday afternoon shore dive, we stumbled on an epic battle of life and death between fish species that normally don't garner much attention from passing divers. Damselfish from the genus Abudefduf -- commonly called "sergeants" or "sergeant-majors" -- are nesting species that lay large mats of purple eggs on the reef. Males of these species guard the nests from predators for the five days that the eggs are incubating. There is no shortage of egg predators on a coral reef, and the work required by the guardian males is arduous. They are usually quite successful at running off the lone butterflyfish or toby that wanders by looking for a snack. However, when a large and well-organized school of predatory fish descends on a damselfish nest, all bets are off for the damselfish guards who can quickly find themselves outnumbered. The saddle wrasse -- a fish found only in Hawaii and one of the most common species on its coral reefs -- seems to have this figured out.
Last week, we went on a leisurely exploratory dive at a seemingly unremarkable location on the West side of Oahu. As we cruised around the reef we were met by the usual cast of critters common on reefs like this one -- including a good number of Abudefduf damselfish. We saw a few of these damselfish make lunging movements toward other approaching fish species. Curious, we swam closer and began to notice quite a few Abudefduf nests with ripe eggs.
The guarders were going about their business of fending off the occasional egg predator -- an interesting behavior but not dramatically more remarkable than other fish activities going on around the area. As we continued along the reef, with one eye casually monitoring the damselfish, we began to notice a growing school of saddle wrasses high above the nest area. Seeing wrasses behave like this is unusual, so we decided to stop moving and watch. We hunkered down close by in the sand, started our cameras rolling, and witnessed a spectacular display of the struggle between the need to reproduce and the need to eat.
After building their army to sufficient numbers, the wrasses descended on the damselfish nests and began devouring mouthfuls of eggs in what can only be described as a feeding frenzy. The poor damselfish were completely overwhelmed and tried with no success to scare off the wrasses one by one. The wrasses spent a minute or so at one nest before collectively deciding to move to another nearby nest, terrorize its helpless defenders, and wreak havoc on its fresh egg bed. This pattern continued for a full 45 minutes as the school of wrasses moved about in a coordinated manner, as if they were a single organism. They moved from nest to nest like bees flying among flowers in a garden, dining on nectar.
Had we failed to slow our dive -- to proverbially stop and smell the underwater roses -- we might have journeyed right past the damselfish nest and missed a fantastic display of competing natural forces.
Whenever we think about the next great place to dive -- lamenting that Indonesia's Wakatobi is too far away or that getting to the Red Sea is too expensive -- we always remind ourselves to open our eyes wherever we are and let the wonder of the underwater world come to us. It will always deliver.
Dr. Craig Musburger is a marine biologist and Emmy Award-winning underwater cameraman. He produces UnderH2O, a web series for PBS Digital Studios that follows him and his team on adventures that showcase the natural beauty of the ocean world.
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