June 27, 2025 — When fish biologist Eva Schemmel gets an early morning phone call from the Honolulu Fish Auction, it means something exciting has landed at Pier 38, the center of Hawai‘i’s commercial fishing village.
Recently, it was a record-sized gindai.
Weighing in at 4.95 pounds, the deepwater snapper may not look like a trophy fish to some (especially next to 100–200 pound tunas!). But it’s worth much more than its weight thanks to a collaboration between fishermen and NOAA life history scientists.
Understanding Fish Populations
Schemmel is part of a NOAA Fisheries team that studies the life history of fish species across the Pacific Islands—how they grow, reproduce, and die. These “fish detectives” collect clues from some of the region’s most valuable (and tasty!) commercial fish species to reveal the mystery of fish population structures. This information helps scientists maximize harvest opportunities for fishermen.
“It’s the key piece to understanding if your fishery is healthy,” Schemmel said. “With the best scientific information possible, you can maximize how much fishing you can do, while keeping fish populations reproducing at the same level.”
Healthy fish populations depend on reproductive adults, and it’s often the oldest, largest fish that play the biggest role in keeping their numbers going. By collecting enough samples from larger fish—like the recent gindai—scientists can determine the average and maximum lifespan of fish in a population. This data helps scientists create more accurate stock assessment models—the foundation for management measures.
Tick Tock: Fish With Hidden Clocks
The science of aging fish relies on a key piece of evidence: otoliths. Most fish have these tiny, jewel-like bones in their inner ears. They help fish hear and balance in their surroundings underwater. They also carry information about the fish’s growth, similar to growth rings in a tree. These lines provide a reliable estimate of the fish’s age.
Collecting otoliths is quick and doesn’t harm the catch. In return for this effort, NOAA Fisheries scientists gain a literal lifetime of data.