The movements of adult leerfish Lichia amia in the Breede Estuary, Western Cape, South Africa: insights from acoustic telemetry

Abstract

Leerfish Lichia amia inhabit estuaries as juveniles before moving between estuaries and the marine environment as sub-adults and adults. While adults remain mostly in the marine environment, philopatry has been observed, with individuals returning to areas previously used, including estuaries. The extent to which adults use estuaries, however, is underexplored. As such, this study aimed to investigate this species’ spatio-temporal use of the Breede Estuary in the Western Cape Province of South Africa, using a long-term acoustic telemetry dataset (from 2016–2019) for 8 sub-adult and 2 adult L. amia (690–890 mm fork length). On average, the tagged fish spent 16.6% of their days monitored in the estuary, predominantly in the lower reaches, and were also recorded along stretches of the coastline. Although the presence of L. amia was largely unaffected by month of the year, the highest monthly residency index (0.33) was recorded in May. Tagged fish were recorded entering the estuary on average at 14:29 (±01:46) and exiting on average at 09:33 (±00:54) the next day. Though L. amia appear to use estuaries less as they age, this habitat remains important even for adults, particularly before their spawning migration, emphasising the importance of maintaining the health of estuarine ecosystems for the species’ protection.