Abstract:
This study was conducted on the morphology and microstructure of otoliths of
juvenile fish species from Kakum River Estuary, Benya Lagoon and the coastal
marine waters near Cape Coast in the Central Region of Ghana, to ascertain their
practical use in age and growth studies. Otoliths of twenty–nine (29) species from
fourteen (14) families were examined. A linear relationship determined for otolith
length – total length, which was described by the equation OL= a + bTL, gave a
range of r = 0.22 to 0.96 for commonest species from the three sites, thus
suggesting that otolith growth is dependent on somatic growth. Also, otolith
morphology was observed to vary among species as the morphological
characteristics were species – specific. The otolith microstructure of most of the
species showed clear primary growth increments but many lacked a hatch check,
hence the embryonic stage of the fish could not be identified in the otolith.
Observed patterns of increment deposition for some otoliths appeared to follow a
likely weekly pattern whereas others had no clearly-defined patterns of
deposition. The mullet species (Mugilidae) however, did not show clear increment
deposition as the otoliths had large portions which were obscured hence
increment deposition could not be defined for these species. In effect, the results
show that the microstructure of otoliths of some species could be used for age and
growth studies if increment formation rate can be validated. Also, otolith
morphology could provide a base-line information for species identification and
differentiation.
