The internet is full of superlatives related to all kinds of topics but we’re planting a flag in this virtual ground, and stating outright that these videos of mass spawning aggregations from Unique Dive Expeditions are some of the most amazing reef fish behavior we have ever seen captured on video. As far as reef fish are concerned, the majority of fishes we are interested in practice pelagic spawning techniques between two fish.
Wrasses, angelfish, most surgeonfish and most types of basslets spawn when two fish show the right cues, decide to get it on, and rise to the surface to do the deed. But there’s a small cohort of fishes who gather in massive aggregations to practice a seasonal spawning event consisting of many members of a population.
Nowhere is this spectacle of mass spawning aggregations more in play than on the reefs of Palau where divers have recorded huge swarms of a handful of very common aquarium fishes. The spawning rituals of orange spined unicorn fish, aka standard naso tang, Naso lituratus, moorish idols, threadfin snappers, and many more were completely unknown until it was revealed that these fish gather in huge numbers to spawn as a collective.
The huge schools of naso tangs, moorish idols, bumphead parrotfish and threadfin snappers gather in numbers so large that these species form mono-specific “walls” of each species when they gather at certain places, during certain time of the year, to spawn en masse. Unlike the paired up pelagic spawners who mate practically every night with just two fish, the species involved in these mass spawning events also happen to be the types which show the least amount of variability, have huge geographical distributions, and also have very long larval durations.
Think about it, when’s the last time you ever saw, heard about, or read about an aberrant moorish idol or naso tang? Quasi-never. There’s definitely a link between mass spawning, wide distributions and larvae which take a long time to settle out of the planktom; we dont know what it is but it is well and thoroughly documented in these videos by Unique Dive Expeditions.
All geeking out about fish biology aside, these videos are some of the most unique and profound we have ever seen and it makes us want to visit Palau more than ever. When we dive we’re really scoping out the corals of the reef and looking for great colonies, cool shapes and interesting colors. However, should we be faced with a veritable wall of moorish idols or naso tangs in numbers so dense they practically block the sun, we’ll be sure to pay attention to the more charismatic members of the reef.