Thursday, April 8, 2010

#7 - Taking a moment to enjoy the show

Peter Gawne, Belize Expedition

Randi and I have now been looking into the diets of reef fish for some time now. Most of our dives are spent with our noses in the reef, not really paying attention to what's happening over our heads.

This particular dive was too deep for us to get two full sets of data. When working underwater, the deeper one goes the less time that you can spend down there. It's a complicated physiological process that involves the accumulation of tiny nitrogen bubbles in the bloodstream, but it will suffice to say that we did not have time to record another data set. On this dive we knew that we would have a little time to lift our heads out of the reef, take in some of the sights, and hopefully snap off a few pictures.

Thousands of Creole wrasses engaged in an elaborate mating dance over our heads.

On a peninsula of reef, extending up from the sand channel, we found Creole wrasses (Clepticus parrae) in the thousands. In the days surrounding a full moon Creole wrasses gather in huge numbers in order to spawn. These small fish aggregate in a spawning rush in order to play nature's numbers game. Creole wrasses spawn in large schools, all at once, so that a huge number of fertilized eggs are in the water at once. Predators, disease, and lack of food are but a few of the obstacles facing the young Creole wrasses on their journey toward adulthood. If even a fraction of these fertilized eggs survive, the Creole wrasses have accomplished their mission.

Atop our thin finger of reef, one of these obstacles is very apparent. The spawning rush attracts predators of all shapes and sizes. Egg-predators, such as damselfish, are drawn from the cover of the reef in order to feed on the plentiful eggs suspended in the water. The Creole wrasses stick to their numbers gamble, and make no attempt to protect their spawn or to deter the egg-predators.

Large, fast-moving horse-eye jacks patrolled the periphery of the reef.

Egg-eaters are not the only predators to join the party. Permit, groupers, cero mackerel, horse-eye jacks, barracuda and skipjack tuna all patrol the blue water surrounding the peninsula. These large predatory fish are present in great numbers, presumably to take advantage of the many fish that have been drawn into the open by the prospect of a free meal.

Two large tiger groupers hold in the distance as horse-eye jacks encircle the reef.

Large in both size and numbers on this particular dive, it was unusual to see so many groupers. Tiger, black and yellowfin groupers all made an appearance. These animals have been hunted extensively as their firm white flesh and great size makes them especially prized by fishermen. One of the groupers on this dive allowed Randi and I to get close enough to see an old wound on its head, probably from an unsuccessful spear-diver.

This dive has been one of the highlights of our trip. It has proven difficult for me to capture the scale of Creole wrasse spawning, so I hope the pictures provide some glimpse into the magnitude of the event. It was very nice to take a quick break in data collection to just sit back and enjoy the show that nature sometimes puts on.


Facebook Comments


Post a Comment