Population dynamics of two small cichlid fish species in a tropical man-made lake (Lake Kariba)

摘要

The population dynamics of two small cichlid fishes (Pharyngochromis darlingiandPseudocrenilabrus philander) were studied in Lake Kariba, a very large African man-made lake. They are of no economic importance but make up about 14 and 7 respectively of the inshore fish population and are the major components of the diet of fish-eating birds on the lake.P. darlingiisthe larger species (L∞= 156.5 mm) and is found on both shelving and steep, eroding shores. Its mortality rate differs in each habitat (Z= 0.44 and 0.72 month−1respectively), only 0.79 survive for 12 months and its MathType!MTEF!2!1!+- feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamiuaiaac+ cadaqdaaqaaiaadkeaaaaaaa!384D!P/overline B ratio is 5.45 (on shelving shores).Ps. philanderis smaller (L∞= 83.9 mm) and is restricted to shelving areas with abundant vegetation. Its monthly mortality rate was high (Z= 7.69), only 0.05 survive to 12 months whilst its MathType!MTEF!2!1!+- feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamiuaiaac+ cadaqdaaqaaiaadkeaaaaaaa!384D!P/overline B ratio was very high (7.69). The estimates of growth obtained forP. darlingidiffer considerably from those given in an earlier study in Lake Kariba and some possible reasons for this are discussed. In suitable habitats, the combined production of both species could be 40 kg ha−1yr−1which indicates their potential importance to the ecology of