Modelling and forecasting of catfish species yield from Mangochi artisan fisheries of Lake malawi in Malawi

Most of the wild fish stocks in Malawi either are fully or over exploited. This challenge underpins importance of forecasting using available data to support sustainable fisheries management. The study aimed at modelling and forecasting Catfish (Mlamba) species yield from artisan fishery on Lake Malawi in Mangochi District as they are becoming important food fish due to decline of more important fish species such as Oreochromis(Chambo). The study was based on secondary data on fish catches between1976 and 2012, collected from Fisheries Research Unit of the Department of Fisheries in Malawi. The study considered Autoregressive Integrated Moving Average (ARIMA) processes to select an appropriate stochastic model for forecasting the species yield. Appropriate models were chosen based on ARIMA (p, d, q). Autocorrelation function (ACF), Partialautocorrelation (PACF), Akaike Information Criteria (AIC), Box-Ljung statistics, correlogram of residual errors, distribution of residual errors, ME, RMSE, MAPE and MAE. Selected model was ARIMA (0, 0, 1) for forecasting artisan landings of Catfish from Lake Malawi in Mangochi District from 2013 to 2022. Based on the chosen model, forecast for artisan Catfish landings showed mean of 352 tonnes and mean of actual catches was 362 tonnes. However, catches in year 2022 are projected to be 360 tonnes, slightly below the actual catches mean but above 236 tonnes in 2010, assuming other factors remain constant. Confidence intervals of the forecasts included a zero and as such over exploitation of the species cannot be ruled out. Landings of the fishery will increase to 360 tonnes and remain stable through year 2022 necessitating fisheries managementconsideration to improve the trend. Policy makers should secure sustainable exploitation of Catfish species, among artisan fishery in the study area by controlling all fishing effort that lands the species such as gillnets, beach seines, open water seines among others

Effects of common carp and African catfish on plankton, periphyton, benthic macroinvertebrates in pond ecosystem

As the common carp Cyprinus carpio and African catfish Clarias gariepinus affect biotic assemblages in aquatic ecosystems through their benthivory, their introduction has been considered an environmental concern. We compare the effects of common carp and African catfish on adjacent trophic level assemblages of plankton, periphyton, benthic macroinvertebrates and native tilapia in a pond ecosystem at the National Aquaculture Center, Zomba, Malawi. Four treatments were involved in the study: ponds with common carp (T1), ponds with African catfish (T2), ponds with both common carp and African catfish (T3), and ponds lacking both common carp and African catfish (T4). In all treatments, the endemic Shire tilapia Oreochromis shiranus was also present as part of the local macrofauna. Results showed that T1 had the most abundant phytoplankton but the lowest periphyton, zooplankton and benthic macroinvertebrate abundance and diversity. T4 had the least phytoplankton but the most abundant and diverse zooplankton, periphyton and benthic macroinvertebrates. There was no significant difference between T2 and T3 (both intermediate to T1 and T4) in terms of phytoplankton, periphyton and benthic macroinvertebrate abundance and diversity. Better water quality regime and increased biomass of native tilapia fish were observed in T3 ponds. We conclude that the farming of common carp in aquatic ecosystems containing African catfish may not adversely affect the environment and that the polyculture of African catfish and common carp can be adopted as a management strategy to mitigate the potential adverse effects of common carp

Efficiency of oxidation ponds in wastewater treatment

Aresearch was conducted at Kauma oxidation ponds, a Sewage water treatment plant found in Lilongwe, Malawi with an aim of establishing the efficiency of these sewage treatment ponds in treating sewage wastewater. Water samples from the effluent discharging points in the maturation ponds were collected and analysed in the labouratory for, BOD, Coliform bacteria, Total Nitrogen (TN), Phosphorous and Chlorophyll-a. Other parameters like Temperature, DO, and pH were measured on site. It was found out that FCB, TP, TN, Chlorophyll a and BOD were 4.59x103CFU, 1.94x103µg/L, 1.78x103µg/L, 2.68x103µg/L and 10.6mg/L, way abovethe WHO guidelines for drinking, swimming and bathing waters for which uses is the Lilongwe river to which this effluent is discharged. The presence of FCB, BOD, P, chlorophyll-a, in large quantities indicates the inefficiency of the oxidation ponds. Furthermore, the presence of high concentration of chlorophyll-a indicated a heavy loading of the river with organic matter found in phytoplankton demanding a tertiary treatment to have a clean water discharged into the river system

Effect of varying levels of dietary vitamin C (ascorbic acid) on growth, survival and hematology of juvenile tilapia, Oreochromis karongae (Trewavas 1941) reared in aquaria

Vitamin C (ascorbic acid) requirement of juvenile Oreochromis karongae was studied by incorporating varying levels of ascorbyl-2-polyphosphate in a 40% crude protein diet to obtain 0, 20, 40, 60 and 80 mg ascorbic acid equivalent kg-1 diet. Juvenile fish of 3.7g ± 0.02g initial body weight were used for the study. After 84 days of the experiment, the fish fed AA- supplemented diets had significantly (P &#60 0.05) higher specific growth rate protein conversion efficiency and protein efficiency ratio; and significantly (P &#60 0.05) better feed conversion ratios than non supplemented fish. Fish fed non supplemented diet recorded a 33 % rate of mortality, where as those fed with a diet supplemented with 60 mg ascorbic acid kg-1 had mortality as low as 4.4 %. Hematological indices showed a significant increase (P &#60 0.05) with dietary AA level. Diet containing 60 mg kg-1 of AA showed the maximum growth performance, while the broken line model gave 51 mg ascorbic acid kg-1 diet as the optimal level required by juvenile O. karongae. Our data show that ascorbic acid is essential for O. karongae growth performance

Heterogeneity in male and female farmers’ preference for a profit‐enhancing and labor‐saving technology: The case of Direct‐Seeded Rice (DSR) in India

Labor‐saving and income‐increasing technologies may affect women farmers differently from men. However, very few studies explicitly account for women's preferences for new technologies. We carried out a discrete choice experiment with 337 female and 329 male farmers in Maharashtra, India, to measure their willingness to pay (WTP) for direct‐seeded rice (DSR) with drum seeder and to understand the gender differences in marginal valuations of key attributes. We used the Women's Empowerment in Agriculture Index (WEAI) to collect self‐reported data on the role and say of women in different domains of decision making. The respective gender roles of women and men in the family and on the farm are aligned with their preferences. Men have a greater say over how the family spends the cash. Accordingly, men tend to have a higher WTP for attributes that increase income (increase in yield) or reduce cash costs (reduction in seed rate). Women contribute a large share of the labor for transplanting rice, much of which is unpaid work on family farms. Women, therefore, seem to value labor saving more. Women in our sample were more interested in the new technology and had a higher WTP for it