Informative approaches to ageing Antarctic fishes

Two concepts can be examined when studying the age of Antarctic fishes. Age can be considered in terms of the passage of time (chronological age), and it can also be examined as 'physiological time'. In this regard otoliths and post-mitotic tissues may contain a large amount of biological and ecological information about a fish's age and past life history. In otoliths this information may be divulged when structural and chemical components are investigated. External and internal examination of otoliths by light and scanning Electron Microscope (SEM) methodology demonstrated that rhythmic otolith architecture increased with fish size and was indicative of daily deposition, validated to be daily. Morphometric measurements of otoliths suggest that otolith size and fish size are directly correlated and that species differences in shape exist. Regression analyses of otolith dimensions may make it possible to estimate the age of a large number of fish easily. Chemical analyses of stable isotopes and elemental concentrations in otoliths suggest that otoliths may also contain hydrographic and nutritional information. A thorough utilization of structural and chemical analyses; Antarctic fish otoliths may make it possible to link growth to environmental occurrences. Measurement of the gerontological and metabolically accumulated cellular pigment, lipofuscin, in brain and cardiac tissue may make it possible to define physiological age. Internal and external structural and chemical analyses of otoliths combined with chemical analyses of nerve and cardiac tissue would increase the ease and precision of growth determinations in Antarctic fishes.