Ecology, fish and fishery of Lake Liambezi, a recently refilled floodplain lake in the Zambezi Region, Namibia

摘要

Lake Liambezi (300 km(2)) refilled in 2009 after a prolonged 22-year dry period. Its aquatic macrophyte populations, fish fauna and fishery shortly after refilling are described. The emergent aquatic macrophyte Phragmites australis formed dense stands covering large parts of the lake, while extensive beds of submerged Lagarosiphon ilicifolius and Najas horrida occurred in shallower areas. Twenty-nine fish species were recorded in experimental gillnets. Catches were dominated by Brycinus lateralis and Schilbe intermedius, contributing 39.5% and 38.5% by weight, respectively. Large-meshed (3-4.5 inch) monofilament and multifilament gillnets emulating those used in the commercial fishery caught mostly Oreochromis andersonii (42.7% by weight) and Serranochromis macrocephalus (28.3% by weight), respectively. Commercial gillnet catch per unit effort (CPUE) averaged 7.0 kg 100-m net(-1) night(-1), and the annual yield for 2011/2012 was estimated at 2 700 tonnes. Aquatic macrophytes and fishes quickly recolonised the lake and, just two years after refilling, the lake supported a thriving fishery that yielded 4.5 times more than the 600 tonnes recorded in 1974.