Using baseline biological and ecological information to design a Traffic Light Precautionary Management Framework for leerfish Lichia amia (Linnaeus 1758) in southern Angola

Abstract

The coastline of southern Angola is sparsely populated and, largely because of a protracted civil war, has very lightly exploited inshore fish stocks. This has provided the almost unprecedented opportunity to determine prefishing-state reference points and to implement management strategies at the early stages of exploitation. The leerfish Lichia amia is distributed from the Mediterranean Sea, along the west coast of Africa to the southern and eastern coasts of South Africa. Despite its importance in recreational catches in South Africa and Angola, there is little information on the biology of this species. The leerfish is one of the three most dominant recreational shore-fishery species in southern Angola, and a biological study on the species was conducted in that region between May 2005 and December 2006. The mean length of captured fish was 767 mm fork length (FL) and 6.8 kg, and the catch per unit effort was 0.13 fish angler−1 h−1 and 0.79 kg angler−1 h−1. The growth of the leerfish population (in mm) was described by: L t = 1 137(1 − e0.22(t + 1.58)), and its total mortality was estimated to be 0.41 (±0.05). Female mortality (0.40 ± 0.06) was lower than that for males (0.44 ± 0.14), and the length and age-at-50% maturity was 623 mm FL and 2.4 years respectively. Female fish with ripe ovaries were found between June and November. The male:female ratio was 1:1.9. Leerfish fed exclusively on fish, mainly sardinella Sardinella aurita (62% frequency of occurrence). Based on this biological information, a theoretical Traffic Light Precautionary Management Framework is constructed for the species. Appropriate management regulations and potential future threats to the species are discussed.