Exploring the biological information content of growth increments in otoliths of Recent and fossil species of the Gobiidae (Teleostei)

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Fish otoliths exhibit daily, seasonal and annual increments (growth rings and marks) that can provide important biological information on life history characteristics. Previously published studies indicate that growth analysis, determination of age at metamorphosis (transition from larva to juvenile fish) and at death is feasible based on otoliths of Recent gobiid (goby) species. In the proposed project we will first use the otoliths of Recent goby species to develop an optimized protocol for otolith thin-section preparation and to gather insights into analysis of growth patterns and age determination of a goby specimen. Because we are interested in identifying dwarf goby species in the fossil record, we will use for this first step the otoliths of two normal-sized (8-10 cm total fish length) and two dwarf goby species (< 4 cm total fish length). Next, we will apply the method to the otoliths of two fossil species (10 otoliths per species) to analyse growth and age patterns. The project will be conducted in collaboration with Dr. M. Afzal Khan (India) who has great expertise in determining growth rates and ages based on otoliths from Recent fish species. Fossil otoliths of gobies are very abundant in the fossil record since the Miocene. If we succeed in defining life history characteristics and ages for the fossil goby species studied during this project, fossil otoliths will provide a new proxy for understanding the biology of ancient gobies (and possibly also for other fish groups). Furthermore, identification of a fossil dwarf goby would open up a completely new source of information on ancient goby species diversity. Thus, the outcome of the proposed project would significantly advance our understanding of the evolution of an important group of fishes.