Growth Performance of Three Forage Fish in a Hyper-Saline Lagoon: The Coorong, South Australia

The present study investigates environmental impacts on the growth performance of three forage fish: small-mouthed hardyhead (Atherinosoma microstoma), Tamar goby (Afurcagobius tamarensis), and sandy sprat (Hyperlophus vittatus) in the Murray Estuary and Coorong. Fish were sampled using a seine net and fish age was estimated using the daily increment of sagittal otoliths to determine growth patterns of these three forage fishes. The estimated growth rates were 0.019 day−1 (r2 = 0.98) for small-mouthed hardyhead, 0.038 day−1 (r2 = 0.95) for Tamar goby and 0.016 day−1 (r2 = 0.94) for sandy sprat. The length-weight relationship indicated the slope (b = 2.96; r2 = 0.97) in small-mouthed hardyhead, (b = 3.06; r2 = 0.98) in Tamar goby and (b = 3.1; r2 = 0.88) in sandy sprat. Spatiotemporal variation in the condition factor was observed in all three-forage fish across the salinity gradients. Chlorophyll-a, water transparency, salinity, and to a lesser extent temperature and oxygen predominantly influenced the growth of forage fish. This study indicates that environmental factors can greatly influence the growth parameters of forage fish. The findings offer new insights into the growth variations of small-bodied forage fish in a reserve estuary with a broad salinity gradient.