A preliminary study of the ecology and commercial fish catches was car
ried out in the Toho-Todougba, Ahouangan and Dati lakes (1500 ha) in s
outhern Benin (West Africa) over a period of 18 consecutive months. Wa
ter quality, species richness, and the reproductive biology of the dom
inant species, Sarotherodon galilaeus, were examined. Unlike Lagoon To
ho-Todougba, lakes Ahouangan and Dati are less favourable for fish pro
duction because of their high total iron content and their relative lo
w pH. The study revealed the existence of 19 species belonging to elev
en (11) families: 16 species in Lagoon Toho-Todougba, 12 in Lake Ahoua
ngan, and 7 in Lake Dati. Lakes Ahouangan and Dati had a relatively hi
gh faunal similarity whereas Lagoon Toho-Todougba exhibited a relative
ly low faunal similarity with the former systems. In Lagoon Toho-Todou
gba, six cichlid species were the most important component of the fish
ery: Sarotherodon galilaeus, Tilapia guineensis, T. zillii, T. mariae,
Chromidotilapia guntheri, Hemichromis fasciatus. Three catfish specie
s Chrysichthys auratus, Clarias agboyiensis, and Clarias lazera were h
arvested in low abundances. Some other fish, such as Polypterus senega
lus senegalus, Protopterus annectens and Heterotis niloticus were capt
ured sporadically, with H. niloticus appearing more consistently in ca
tches than the others. Although not abundant, Gymnarchus niloticus and
the African pike, Hepsetus odoe, were almost always present in the ca
tches. Ctenopoma kingsleyae appeared only in Ahouangan. Some predatory
species, such as Notopterus afer and Xenomystus nigri, are encountere
d only in lakes Ahouangan and Dati. In Lagoon Toho-Todougba, Sarothero
don galilaeus had a sex ratio (male:female) of 0.49:1, and size at mat
uration was estimated as 12.3 cm TL. The spawning period extended from
May to September with the peak occurring in July. Fecundity was corre
lated to log-body length (r = 0.74) and log-body weight (r = 0.76). Fi
sh catches were estimated at 389 kg ha(-1) year(-1); about 73% of whic
h was Sarotherodon galilaeus. The overexploitation of juvenile fish an
d the use of this lagoon for the irrigation of palm tree plantations h
ave reduced fish recruitment and mean size.