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Hawaiian Fishes Like it Deep Coral reef twilight zone acts as a “locals only” hangout for Hawaiian coral reef fishes.

As if Hawaii didn’t already have enough to boast about – beautiful beaches, luscious green mountains, and lava – it now also wears the crown for the highest recorded levels of endemic coral reef fishes in the world.  In Hawaii, “endemic” fishes, or fishes that reside only in the Hawaiian Islands and nowhere else in the world, make up approximately 25% of all fish species. This percentage of local reef fishes put Hawaii among the top ten places in the world for unique reef fish – or so we thought.

Recent investigations to deep coral reefs in Hawaii (150-300 ft. below the surface, a.k.a. the coral reef “twilight zone”) have blown the previous estimates of endemic coral reef fishes out of the water.  Using technical diving gear, researchers documented coral reef fish abundance on mesophotic coral reefs (coral reefs deeper than 130 ft.) for the first time, and the results were astonishing.  They found that near the northern end of the Hawaiian Islands, local reef fish made up over 90% of the fish species observed.  This means that instead of local fishes typically being the minority on reefs, they completely dominate reefs at deeper depths.

While the “why” is still being investigated, it is likely that Hawaiian fish have adapted better to the colder, deeper reefs than the more widespread and tropical fish species common at shallow depths and more equatorial latitudes.  Which makes sense; we see a lot of “outsiders” in nice warm places like Miami Florida, but if you visit places like Dutch Harbor Alaska, its mostly locals, right?  Either way, these findings make the deep reefs of Hawaii one of the most unique and cool coral reefs in the world.

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Source: Community ecology of mesophotic coral reef ecosystems
Publication Date: 27 February 2010

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