3. Variability of Otolith Morphology in Major Fish Species in Coastal Waters of Cape Coast-Elmina, Ghana

Abstract

The fish sagittae otoliths have unique structures for various fish species. These otoliths are very important hard parts in fish for growth and age studies. In this study, sagittae otoliths of major marine finfishes were analysed and compared using descriptive morphological characters. Information obtained was a first step that would lead to future age and growth studies on these fishes for stock assessment in fisheries management. The study was conducted in 2017, and 38 fish species belonging to 21 families were encountered in the beach seine landings (Cape Coast) and artisanal canoe and semi-industrial landings (Elmina), all in the Central Region of Ghana. The fish species and their respective sagittae otoliths were extracted using standard methods and all were digitally photographed. The observed differences among the otoliths were in their overall shape, margins and anterior region that were described to be oblong, obovate, discoid, oval, rhomboidal, anvil-shaped, ovate, circular, triangular, elliptic, spindle-shaped, tear-drop and rectangular. The margins were observed to be irregular, crenate and sinuate for various otoliths. Ranges of fish total lengths and sagittae otolith lengths were presented for various fish species encountered during the study. The largest otolith lengths were recorded in Pseudotolithus senegalensis (82 – 230 mm TL; 4.7 – 8.0 mm OL) and the smallest otolith lengths were observed in Sardinella aurita (76 – 209 mm TL, 1.4 – 3.5 mm OL). The results of these sagittae otoliths descriptions in this study would be a useful information towards ageing of finfishes which is lacking in Ghanaian waters.