Glenn Wilson of the University of New England, Australia, , Belda Mosepele of the BIOKAVANGO Project and HOORC fish biologist Keta Mosepele have collaborated in work to introduce the use of otoliths in the study of fishery resources in the Okavango Delta. Following the eight day course in fish ageing methods conducted by Dr Wilson earlier this month, the researchers are developing a programme of further study to apply these methods to determine:
1. Growth and longevity. Basic descriptions of growth patterns and longevity are unavailable for virtually all Okavango fishes.
2. Year-class strength and flooding. Climate change, upstream abstraction and interannual climate variability all have the potential to alter annual Delta flooding patterns. Otolith data can assist in linking the importance of flooding and fish production through age-structure analyses to help forecast response to future conditions.
3. Which part of the flood pulse is most critical for spawning? From daily age estimates, hatch or spawning dates can be back-calculated and their timing matched to variables such as hydrology or climate.
4. Where are fish spawning? Otolith microchemistry may help discriminate between main-channel and floodplain origin of fish larvae.