ounting and recording every fish they see in four 100-square-meter areas. For key species, such as the yellow tang, they also note size, and keep a special watch for baby fish, known as recruits.
Unlike freshwater tropical fish, which are cultivated in tanks, most ornamental saltwater fish are caught in tropical reefs. In Hawaii, divers often herd fish into large nets, then use hand nets to scoop them into buckets. Hawaiian collector David Dart says that in good weather, an average diver can pull in 100 to 150 yellow tang a day. On other reefs around the world, collecting is more aggressive: fishermen use cyanide to stun fish, making them easy to scoop up.
The monitored sites include areas protected for a minimum of ten years that prohibit collecting, fishing or both, recently restricted areas closed only to aquarium collecting, and those open to all fishing. Walsh’s numbers are beginning to detect trends. Three years into a five-year study, he has found that yellow tang is no longer declining in the newly protected areas but continues to decline in open areas.
Aquarium collecting is not the only threat to reef fish. Overfishing, warming oceans and pollution from human development all threaten both the reefs themselves and the fish that feed off them. On the day I drove to Hanauma Bay, a Marine Life Conservation District on Oahu and Hawaii’s most famous snorkeling spot, the beach was oddly empty except for police officers. It was closed because a broken pipe was spewing sewage over the reef.
In his surveys, Walsh also counts the baby recruits in protected and unprotected areas. The fact that he has yet to detect much of a difference worries him. "Without an increase in recruitment, the reserves won’t realize their full potential," he says.
On another day, off the Maui coast, the sea is calm and so deeply blue that the sky pales in comparison. Diving just underneath the waves, you can hear the songs of humpback whales. Chris Kelley and his crew are fishing for onaga and ehu, which live at depths of up to 1,000 feet. The researchers record the location of every fish reeled in and correlate that information with seafloor images they get from a sonar fish finder. They note each individual’s sex, length and weight, then throw it back. These fishing trips, combined with observations made in submersible dives, are painting a picture of the lives of these little-known species.
Kelley has found that adult fish prefer craggy outcrops, while the young seem to hover over lower relief outcrops. Ehu live closer to the bottom, while onaga school several meters above it. Kelley has surveyed bottom fish habitat throughout the main Hawaiian Islands, and in several months, he will present his recommendations for Hawaii’s 19 bottom fish reserves to the state government. The areas were set up with scant knowledge of the type and location of critical fish habitat. Now, Kelley’s data shows that at least two of the reserves are misplaced, lacking the jagged topography the fish call home.
In Pupukea on the north shore of Oahu, I follow Carl Meyer, a graduate student at the University of Hawaii, into the water. He shows me how easy it is to catch fish at night, bare-handed. Shine a light into their eyes and they freeze like deer on a road. He grabs a striped convict tang. In one study, Meyer caught dozens of fish, tagged them with ultrasonic transmitters and released them. Then, to learn their movement patterns, he paddled after them in his hydrophone-equipped kayak.
He discovered that the three species he tracked (blue spine unicorn fish, yellowstripe goatfish and blue jack) all had well-defined home ranges. With the regularity of bank employees, they commuted daily between their sleeping areas in the reef and their feeding grounds. While unicorn fish stayed within the reserve, the goatfish and jack had home ranges three times the reserve size, exposing them to daily danger. Meyer concluded that tripling the reserve’s size, which is currently a mere tenth of a square mile, would protect these mobile species.
In a statement issued last autumn, 16