Title: Population parameters and exploitation rate of Engraulicypris Sardella and Rhamphochromis species in southern Lake Malawi: Case of light attraction fishery

Type:
Final project
Year of publication:
2004
Publisher:
UNU-FTP
Place of publication:
Reykjavík
Number of pages:
39

Abstract

Growth parameters (L∞ and K) and mortality coefficients (Z, M and F) were estimated for Engraulicypris sardella and Rhamphochromis species caught in southern Lake Malawi using light attraction (kauni) fishery. The number of recruitment peaks, growth performance index (ø’) and exploitation ratio (E = F/Z) was also assessed for each species. Routines in the FAO-ICLARM Stock Assessment Tools (FISAT II), Length Frequency Distribution Analysis (LFDA) software and Excel SOLVER were used to estimate the parameters from length distribution data collected from March to November 2000. The key parameters were used in relative yield (Y’/R) and biomass per recruit (B’/R) analyses to derive reference points and evaluate the exploitation status of the two species caught by light attraction fishery (chilimira nets). Relatively high K and low L∞ values, typical of short-lived tropical fishes, were obtained, combined with high Z, M and F estimates, these results imply low annual survival and high turnover rates. Both Engraulicypris sardella and Rhamphochromis species exhibited year-round recruitment, with Rhamphochromis having two recruitment peaks. The values of current exploitation rates for Engraulicypris sardella from light attraction fishery in Southern Lake Malawi seem to be sustainable. However, Rhamphochromis values were very high compared to the estimated reference points of Emax, E0.1 and E0.5. Overall, the results indicate that Engraulicypris sardella was fished at maximum sustainable yield in 2000 and for Rhamphochromis there was over-fishing. The results provide preliminary baseline information (as well as reference points) that can be incorporated into wider reference systems relevant to current fisheries assessment and management in Lake Malawi.

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