Tropical Otoliths – Where to Next?

Abstract

The formation of alternating zones of different composition and optical density (translucent, protein rich zones and opaque, calcium rich zones) as otoliths grow throughout fishes lives is the underpinning basis of ageing from otoliths. A consistent theme throughout this book is that methods for enumerating otolith growth increments to estimate fish age are well-established but there is a general lack of understanding of the fundamental processes of increment formation. It remains surprisingly unclear what are the endogenous process responsible for this zone formation and how those endogenous processes interact with exogenous influences. This issue is not unique to tropical environments but perhaps takes on greater importance in the tropics because of the great diversity of species for which ages are sought and the consequent high cost of detailed validation of ageing methods if required for every species (Choat et al., Chapter 2).