Friday, September 7, 2007

Protecting marine life: more than just a ban on harvesting

If you're going to run cattle, you need to not only manage the cows, but also the pasture.

It's a message that seems self-evident, but may be missed by some of those who would manage marine life by banning harvesting alone.

With reef fish, for example, if you seek to protect them, you need to also protect the reef itself. That's the conclusion of Edward DeMartini, of NOAA's Pacific Islands Fisheries Science Center in Honolulu, and Todd Anderson, of San Diego State University. Their study on the subject was published in the Bulletin of Marine Science (2007, Bulletin of Marine Science 81:139-152).

The two studied the behavior of baby fish, including yellow tang, kole and others, at three Big Island locations, one of them a protected site, one open to wind and waves, and one semi-protected.

They found that when possible, they often clustered within the branches of finger corals. The corals provide them two key things: food and protection.

“The Hawaiian-endemic finger coral Porites compressa provides essential habitat for juvenile yellow tang, kole, and numerous other reef fishes,” DeMartini wrote in an email.

“Finger coral provides an essential habitat for many species of herbivorous (algae-eating) fishes because its dead basal surfaces (surfaces on which turf algae proliferate) also provide shelter from predation by fish-eating fishes,” he wrote.

It's clearly not simply that they happen to occur here, but such sites form preferred shelter for these small fish. And that means the little fishes are more likely to survive to become big fishes.

There's more science to be done on the issue, but the scientists said that clearly the complex structure of a healthy reef is an important part of protecting the fish life on it. It suggests, for example, that it's not enough to simply tell people they can't kill a species. You also have to prevent folks from smashing the bottom with boat anchors, from breaking up corals as they walk on the reef, and from letting muddy water smother the nearshore ocean floor.

“Corals habitat also must be protected from destructive human influences such as anchor damage and the sedimentation that results from unregulated coastal development, in order to preserve the juvenile habitat that is necessary for population replenishment,” DeMartini wrote.

© 2007 Jan W. TenBruggencate

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