Seafaring Scientist Seeks Deepwater Fishes

Tomio Iwamoto spends weeks at sea to collect bottom-dwelling fishes.

Academy ichthyologist Tomio Iwamoto needs much more than a fishing pole to catch his study subjects, a group of deepwater fishes called grenadiers that live up to 6,000 meters below the surface. There, where the sun never shines, animal carcasses and decaying plant material float down from above, fueling invertebrates and small fishes, which grenadiers eat; grenadiers, in turn, are fed upon by larger animals such as commercially important codfish, seals, and sea lions. Iwamoto is studying the evolutionary relationships of these important links in the bottom-water food chain.

To collect grenadiers, Iwamoto mainly depends on others. He may spend up to 5 weeks on a fishing boat living with crews and sifting through bycatch, or on an oceanographic vessel accompanying other scientists sampling deepwater life. In this fashion, Iwamoto has cruised the Pacific coast from the Bering Sea to Southern California, sampled the waters around New Caledonia and the Philippines, and surveyed most of the western tropical Atlantic.

To study grenadiers in deep waters of Bering Sea, Tomio Iwamoto went aboard the Yakushi Maru, a Japanese fishing trawler. Fish are dropped to holding area below deck for sorting. Tomio helps sort fish into baskets and works on collaborative surveys of Japanese catch. August 1980. Photo: Tomio Iwamoto

Grenadiers are also known as rat-tail fish because of their long, scalytails. Drawing: Kuronezumia paepkei, species of grenadier firstdescribed by Shcherbachev, Sazanov and Iwamoto in 1992.

Yakushi Maru, Bering Sea, June 27, 1979 Photo: Tomio Iwamoto

Iwamoto was part of a recent Academy expedition to the African islands of São Tomé and Príncipe, where he collected fishes that spend their early years in the ocean, but find freshwater streams as juveniles in which to live out their lives. While Iwamoto is excited about his new subjects, unlike them, he is not ready to leave the sea. "I'm not sure I want to transfer over to land-based research just yet," he says.

Kintino Cabral and Tomio Iwamoto seining in local river of São Tomé e Príncipe (islands off West Africa). Photo: Dong Lin