The level of under reporting of catch and effort data in logbooks among largescale fishers on Lake Malawi

Accurate fisheries data are fundamental to fisheries management. This ensures accurate stock assessments and equitable allocation of fishing quotas, eventually leading to sustainable fisheries management. This study was conducted among large-scale fishers to assess the level of underreporting of catch and effort data in logbooks. Data on catch and effort were collected from large-scale fishers in the 2023 fishing season (primary data) and compared with historical data (secondary data) from the same period on catch and effort obtained from logbooks at the Department of Fisheries. The density plots, Q-Q plot and Shapiro-Wilk p-values showed that the secondary and primary catch data were normally distributed. The two-sample t-test showed that there was no significant difference between the two groups with a p-value of 0.2359. However, to make the comparison more robust and comprehensive with the Monte Carlo machine-learning approach, nonparametric methods (permutations and bootstraps) that work well even with normally distributed data were employed. The p-value obtained from the permutation test (0.202) indicated that the two datasets were not significantly different, implying that observed physical differences between the groups could be random. The original bootstrap statistics were approximately -959.8, with a standard error of approximately 728.28, indicating that, on average, the secondary catch data were lower than the primary catch data by approximately 960 units. The large standard error indicates that there could be substantial sampling variability, which should be studied and improved, especially in the secondary catch data. The confidence interval included zero, suggesting that observed difference in means was not statistically significant at 5% level. While point estimate was negative, broad confidence interval shows that the effect might be negligible or even in the opposite direction. This implies that the claims that commercial fishers in Malawi underreport logbooks submitted to Department of Fisheries may not be true or significant.