Our jurisdiction spans across the Pacific Ocean and includes three archipelagos (Hawaiian, Mariana, and Samoan) and several remote areas (Howland, Baker, Jarvis, and Wake Islands; Kingman Reef; and Palmyra and Johnston Atolls). These locations provide essential habitat for a large variety of economic-, recreation-, and subsistence-valued coral reef fishes, deepwater snappers and groupers, and pelagic fishes. Understanding the life history of these species creates better informed quantitative stock assessments and, subsequently, ecosystem-based fisheries management.
For fish species caught in the commercial and recreational fisheries of the U.S. Pacific, our scientists collect samples (primarily otoliths and gonads) in many ways: during research missions, through our Territorial Bio-Sampling Program, the Hawaii Longline Observer Program, dockside and market sampling, and fishery donations. We use these samples to determine a fish’s age and assess its reproductive status. The resulting information is used to estimate life history (length-at-age, growth, and length- and age-at-maturity) and population dynamic (mortality) parameters. We specifically examine how these life history traits vary across a species’ range due to anthropogenic effects or environmental factors. We also study coral reef fish communities and responses of reef fish populations to anthropogenic (human-caused) factors.
Additional advances include:
- Geochemical techniques to directly validate estimated individual ages or age determination methods.
- Keys to externally distinguish between males and females.
- Identification of rare deepwater fishes seen during dives with remotely operated underwater vehicles (ROVs).
How do we figure out the age of fish?
We can determine a fish’s age by counting the lines in its otolith (ear bone). Otoliths form annual lines, similar to the rings in a tree trunk. However, every fish species’ otolith is unique—differentiating the early years of growth and the annual growth can be very difficult. One way to determine fish age more precisely is a technique called bomb radiocarbon dating. This technique relies on the rapid increase in radiocarbon that occurred in the world’s oceans as a result of nuclear weapons testing in the 1950s and 1960s, and uses its decay rate to estimate age. We estimate the age of numerous marine fishes by the radiocarbon found in their otoliths. We are now expanding radiocarbon dating to sharks and rays as well as marine algae, deep-sea corals, whales, and mollusks.