What does Life History Mean? Species can be described by a wide range of traits, including behavioral patterns (ex: diurnal activity, schooling size, preferred temperature in water column); morphological body types (ex: maximum body size, body shape, mouth position); ecological influences (ex: diet, spawning strategy, depth of occurrence, life span); and biogeographical limitations (ex: geographic range extension, species distribution). Life History research seeks to understand each subset of these traits better and inform more sustainable fishery management practices. In one common example, knowing when in the year a species spawns a new generation can ensure healthy adults aren’t fished up too early, which would negatively impact the persistence and growth of the population.

How do we get that information? Otoliths, small calcium carbonate structures in a fish’s inner ear, are powerful tools for understanding fish life history. Much like tree rings, otoliths form annual growth layers that reveal a fish’s age, growth rate, and even movements across different ocean environments. Since otoliths are thin bones, they are quite fragile. To count their rings, the otolith is encased in resin, then the block is cut in half to show the cross-section of the rings. PICH has historically studied otoliths to uncover the life history of Gindai (Pristipomoides zonatus) in Hawaiʻi and the Republic of the Marshall Islands.