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Materials that repel sharks could save lives . . . of sharks

A metal that reacts with seawater to produce an electric field may help keep sharks at bay. But the idea isn’t to protect humans from shark attacks. Just the opposite: scientists hope the metal will save sharks from senseless deaths in fishing nets.

An estimated 11 million to 13 million sharks die each year as “bycatch,” collateral damage in the hunt for other fish. Sharks grow slowly and can take many years to reach reproductive age, so their populations are being severely impacted by fishing.

In a recent study that offers hope for preventing some of these deaths, scientists from NOAA, four universities, and a research firm that develops shark repellents placed bars of the metal palladium neodymium in tanks holding juvenile sandbar sharks. The sharks avoided the metal bars and weren’t tempted by bait suspended within 12 inches of the bars. The study suggests that the metal could be used to ward sharks away from fishing gear.

Palladium neodymium is machinable and reasonably priced. But more study is needed to determine whether it can resist corrosion and remain effective as a shark repellent over long periods of time.

Thought to be an anglerfish, its two forward-facing eyes are a first for the fish world

Divers have spotted a new type of fish off Ambon Island in Indonesian waters. The striped fish, which is about the size of a human fist, is believed to be an anglerfish because it crawls along the ground and into crevices using leglike pectoral fins. But unlike most anglerfish, this species does not have a “lure” dangling from its head to attract prey, so it probably represents a family of fish previously unknown to science, says Ted Pietsch, a professor of aquatic and fishery sciences at the University of Washington.

Three scuba divers from Maluku Divers first spotted and photographed one of the fish in late January. In search of international experts to identify the fish, they found Pietsch, who says the fish is unmistakably an anglerfish because of the leglike fins on its sides. Anglerfish are also known as frogfishes and toadfishes.

The fish’s most unusual feature is its flat face. Most fish have eyes on either side of their head, and Pietsch says he has never seen a fish with two forward-facing eyes in his 40 years of studying fish.

The new fish appears to be fleshy with tough skin, because it is able to squeeze itself into very small cracks in coral reefs without getting scratched. That may be how it has escaped human attention for so long.

The divers who discovered the fish kept quiet about it for a while. But now that another adult, two juveniles, and a mass of eggs have been seen, the word is out.

Fish teeth demonstrate that you really are what you eat

Welcome to the prey’s-eye view of the three-spined stickleback. Mark Purnell, a research fellow at the University of Leicester in England, stained the fish to highlight the skeleton and examined surface textures on the teeth. Each tooth is about the width of a human hair, and its texture indicates what the fish ate. Sticklebacks that feed on worms lurking in the sand have scratched teeth; those that eat plankton floating near the top of the lake have smooth teeth. Purnell’s work on both modern and fossil sticklebacks and the wear on their teeth suggests that where the fish ate affected the evolution of their body shape—a first for evolutionary biology, which has never before used fossils to trace the evolutionary effects of feeding. Presumably, as the fossil fish changed what and where they ate, they faced different predators and their spiny defenses adapted accordingly.