Our jurisdiction spans across the Pacific Ocean and includes three archipelagos (Hawai‘i, Mariana, and Samoa) and the Pacific Islands Heritage Marine National Monument (Howland, Baker, Jarvis, and Wake Islands; Kingman Reef; and Palmyra and Johnston Atolls). These locations provide essential habitat for a large variety of coral reef and pelagic fish, and deep-water snappers and groupers that are economically, recreationally, and subsistently valuable. Understanding the life history of these species can better inform quantitative stock assessments and, subsequently, ecosystem-based fisheries management.
Our Research
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, including:
- NOAA Research Missions
- Bio-Sampling Programs
- Longline Observer Programs
- Dockside and Market Sampling
- Fishery Donations
- Fishery Independent Surveys such as the Bottom Fishery Independent Survey
We use these samples to determine a fish’s age and assess its reproductive status. Histological cross sections of the gonads (ovaries or testes) are examined to assess reproduction characteristics such as gender, reproductive maturity, spawning season, and spawning frequency. This information is used to estimate life history—length-at-age, growth, and length- and age-at-maturity—and population dynamics, like spawning seasonality and mortality.
It is not uncommon for the same species of fish to have different growth rates and reproduction in different regions of the Pacific. Therefore, we further examine how these life history traits vary across a species’ range and possible anthropogenic or environmental factors (e.g., food availability, water temperature). This information is used to provide the most accurate and regionally specific information for estimating population abundance and fisheries stock status.
How Do We Figure Out the Age of Fish?
We estimate the age of a fish by counting growth zones in its otolith (ear bone). Otoliths form annual growth zones (annuli), similar to the rings in a tree trunk. However, the clarity of the annuli between species can vary, making it difficult to determine between annual and early years of growth. In certain difficult species, such as billfish, ages can be estimated from other calcified structures, such as fin spines.
Independent age validation methods are also used to verify fish ages, including the bomb radiocarbon chronometer and amino acid racemization. These studies are important in confirming that both the ageing method and calcified structure used, reflect the true age of the fish. Emerging techniques are also being explored to estimate fish age, such as Fourier-transform near infrared spectroscopy (FT-NIRS) and DNA methylation.
Histological slide from striped marlin (Kajikia audax) gonad. Credit: NOAA Fisheries
Current Research
Pelagic Species
We are working with the Pacific Islands Regional Observer Program to collect samples from the Hawai‘i Longline Fleet, as well as international partners in Japan and Taiwan to collect samples across the North Pacific Ocean. The results from this project will result in robust parameter estimates and allow identification of spatial variability in age, growth and maturity for appropriate incorporation into stock assessments.
Billfish Species
Shark Species
Assessments of Pelagic Species
Bottomfish Species
We are collecting biological samples from all bottomfish management unit species from all jurisdictions: Main Hawaiian Islands Deep Bottomfish Species, Marianas Bottomfish Species, and American Samoa Bottomfish Species. We are currently working on several of the bottomfish species life history including ʻŌpakaʻpaka (Pristipomoides filamentosus), Onaga (Etelis coruscans), Lehi (Aphareus rutilans), and Gindai (Pristipomoides zonatus).
Reef Species We are working with partners to support coral reef life history. This has included trainings, biological sample collections, and life history assessments.
