The use of traps and the need for conservation of Synodontis fisheries in Asa Lake, Ilorin, Nigeria

Abstract

The basket conical traps are commonly used to catch Synodontis species by the fishermen in Asa Lake, Ilorin,
Nigeria because these species are caught alive to attract higher market values. Fleets of these traps randomly
set at the bottom shoreline by fishermen at three different locations around the lake from the dam site to the
river source were examined for Synodontis catch in 12 months. The specimen of Synodontis schall and
Synodontis gambiensis were encountered with the latter occurring in August to October corresponding only
with the flood season around the lake. S. schall occurred throughout the seasons but more abundantly in the
traps during the dry season. All the specimens of Synodontis caught were found alive with mean standard
length ranging from 7.8 to 16.75 cm for S. schall and 16.8 to 22.48 for S. gambiensis. Their corresponding
weights ranges are 12.50 to 77.45 g and 49.75 to 92.76, for S. schall and S. gambiensis, respectively. Gravid
specimens of both species were caught between the months of June to August in both the fixed and the lost
traps. A total of 18 lost traps were recovered during the 12 months of research particularly during the flood
seasons. There were no lost traps in November to March. The period of low catch (October and November) also
corresponded with the season when the juveniles of S. schall became abundant in the lake. The total fish catch
in the wet and dry season was significantly different (P<0.05) in both species. ‘Ghost fishing’ a phenomenon that
usually occurred when the set traps were lost due to high floods around the lake and the need for conservation
of these valuable water resources are discussed.