Maturity, age and growth of Oreochromis karongae (Teleostei: cichlidae) in Lake Malawi and Lake Malombe

Size-at-50% maturity, age and growth, of Oreochromis (Nyasalapia) karongae (‘chambo’) in Lakes Malawi and Malombe were studied. Similar size-at-50% maturity and growth patterns were found for populations in Lake Malawi, but differences were observed for Lake Malombe populations, suggesting that current chambo fisheries management regulations, based on findings from the southern part of Lake Malawi, may be applicable to the central and southern parts of that lake, but not to Lake Malombe

The Demand for Fish Products in Malawi: An Almost Ideal Demand System Estimation

The study analyzed the demand for fish products and the factors that affect the consumption of various fish products in Malawi. Considering four fish products, namely dried fish, smoked fish, fresh fish and tinned fish, the study employed a multivariate probit model and an Almost Ideal Demand System (AIDS) model to analyze factors affecting consumption and demand for fish products respectively. Results indicate that consumption of various fish products in Malawi is affected by age, education, gender, marital status, area of residence (Urban versus rural), distance to nearest market, household annual expenditure and occupation of the household head. With regard to demand for fish products, the study found that the demand for dried fish, smoked fish, fresh fish and tinned fish is inelastic and the various fish products were found to be substitutes. It was also noticed that households would increase their expenditure on fish products if their income increases. The results are an important step in designing policies that will increase fish production and ultimately increase fish consumption. The results also show the importance of value chain development by, among others, building the capacity of the fish processors in order to help them better respond to the market and consumer needs. Keywords: Multivariate probit, Fish, Consumption, AIDS model, Deman

Feeding ecology of Bathyclarias nyasensis (Siluroidei: Claridae) from Lake Malawi

In Malawi, fish contribute about 60-80% to the country's animal protein supply. The greater proportion (> 50%) comes from Lake Malawi. Bathyclarias nyasensis and other clariid catfish contribute up to > 20% of the total catches. Catches of Bathyclarias nyasensis in the inshore area of the south-east arm of Lake Malawi are declining and a management plan for the fishery is essentially lacking. There is paucity of biological data that precludes the use of any option to manage the species. The principal aim of the thesis was to define the ecological role B. nyasensis, the most abundant and common of the Bathyclarias species. By examining life history characteristics within a food web context, it was hypothesized that the study would provide an insight into the interrelationships between species, and, hence form the basis for the development of a rational exploitation strategy for the species. The study was undertaken in the south-east arm of Lake Malawi (9° 30'S, 14° 30'S). The principal objectives of the study were to investigate the feeding ecology of B. nyasensis by examining morphological characters and structures associated with feeding, diet of B. nyasensis, food assimilated in the species using carbon (∂¹³C) isotope analysis, daily food consumption rate for B. nyasensis; and to relate the feeding ecology to life history traits such as age, growth, and some aspects of the reproductive biology of B. nyasensis. The suitability of sectioned pectoral spines and sagittal otoliths to age B. nyasensis was assessed. Due to reabsorption of growth zones with increasing spine lumen diameter with fish size, and the relatively low number of spines that could be aged reliably, only otoliths were used. The maximum age for B. nyasensis was estimated at 14 vears. Growth was best was described by the four parameter Schnute mc: lt ={42+(81¹·⁸ - 42¹·⁸)x1-e⁻°·°⁵⁽t⁻¹⁾}¹/¹·⁸ over 1-e⁻⁽⁻°·°⁵⁾⁽¹¹⁾ for female, lt={41+(98¹·² - 41¹·²)x 1-e⁻°·°²⁽t⁻¹⁾}¹/¹·² over 1-e⁻⁽⁻°·°²⁾⁽¹³⁾ and for male fish. Age-at-50% maturity for females and males were estimated at 7 years and 4 years, respectively. Typically, fish grew rapidly in the first year, but slower during subsequent years. Smaller fish were found inshore while larger fish were found in offshore regions. It was hypothesised that the rapid growth in the first year and slower growth later is a consequence of change in diet from high quality and abundant food source to a more dilute food and that this may be associated with a shift in habitat. Morphological characters associated with feeding were used to predict the food and feeding behaviour of B. nyasensis. The size of premaxillary, vomerine, pharyngeal dental and palatine teeth and premaxillary and vomerine tooth plates suggested the capability of B. nyasensis to handle both large and small prey, with a propensity towards smaller prey in composition to C. gariepinus. The molariform teeth on the vomerine tooth plate suggested that molluscs form part of the diet. The relative gut length (1.27±0.24) suggested omnivory, with an ability to switch between planktivory and piscivory. Buccal cavity volume and filtering area changed with fish size at 500-600 mm TL upon which it was hypothesised that the fish diet changed to planktivory at this size. Detailed diet analysis provided information upon which the above hypotheses could be accepted. Percent Index of Relative Importance (%IRI) and a multi-way contingency table analysis based on log-linear models were used to analyse diet data. Results showed that B. nyasensis is omnivorous, but with a distinct ontogenetic dietary shift from piscivory to zooplanktivory at 500 - 600 mm TL. The increased buccal cavity volume at the same fish size therefore, suggests that B. nyasensis is well adapted to filter the dilute zooplankton resource. Increased foraging costs of feeding on zooplankton explained the slower growth of larger fish. The dietary shift was finally corroborated by results of the ∂¹³C isotope analysis. A polynomial equation described the change in carbon ratios with fish size: ∂¹³C = - 33.188 + 0.4997L - 0.0045 (total length)² (r² = 0.598, n = 12, p=0.022). The ontogenetic shift in diet was synchronised with a habitat shift postulated in life history studies. In the inshore region, B. nyasensis were predominantly piscivorous (apex predators), and were zooplanktivorous in the offshore region, thereby forming part of the pelagic food web in the latter region. After examining "bottom-up" and trophic cascade theories, it was postulated that perturbations of the B. nyasensis stock would be discernible both at the top and lower trophic levels. As a piscivore and therefore apex predator, effects of overfishing B. nyasensis in the inshore region could cascade to unpredictable ecological changes in inshore areas and, due to the ontogenetic habitat shift, in the offshore regions. Examples of trophic cascade phenomena are provided. On the basis of the feeding study, it was possible to reconstruct the pelagic food web of Lake Malawi. Apart from the lakefly Chaoborus edulis, B. nyasensis is the other predator that preys heavily on zooplankton in the pelagic zone. Perturbations of the B. nyasensis stock could affect size composition of zooplankton which in tum, could affect production of C. edulis, a resource for the top predators in the food web. The findings of the present study contributed to the ongoing debate of introducing a zooplanktivore into the pelagic zone of Lake Malawi. Proponents for the introductions have argued that zooplankton predation by fish is inferior to that of C. edulis. Introduction of a clupeid zooplankton was proposed as a strategy to boost fish production in the lake. The zooplanktivore would either out-compete or prey on C. edulis to extinction. Opponents to this view argued that zooplankton biomass in the pelagic region was too low to support introductions and that the fish biomass in the pelagic region may have been underestimated. Results from the present study suggest that planktivorous fish (including B. nyasensis) might not be inferior to C. edulis in utilising the zooplankton resource; B. nyasensis is well adapted to utilise the dilute zooplankton resource, and by omitting B. nyasensis from previous studies, overall zooplankton predation by fish may have been underestimated by between 7 - 33%. On the basis of the theoretical migratory life history cycle of B. nyasensis, it is recommended that the current interest in increasing fishing effort in offshore areas should proceed with caution. Ecological changes that may have occurred in the inshore areas due to overfishing have probably not been noticed: as the offshore zone has never been fished. The latter zone may have acted as a stock refuge area. Higher fishing intensity in the offshore areas could lead to serious ecological imbalances and instability. The study has shown that life history characteristics studied in the context of the food web, and in the absence of other fisheries information and/or data, strongly advocates the precautionary principle to managing changes in exploitation patterns

Genetic diversity and structure of potamodromous Opsaridium microlepis (Günther) populations in the inlet rivers of Lake Malawi

Studies were carried out to determine the genetic diversity and structure of endangered Opsaridium microlepis (Mpasa) populations in the affluent rivers of Lake Malawi; Linthipe, Bua, Dwangwa and North Rukuru. A total of 200 DNA samples of O. microlepis from four river populations were analyzed at 20 microsatellite loci. The primers’ discriminating power was high (mean PIC, 0.76) yielding a total of 295 alleles with a range of 10-22 and an average of 15 alleles per locus. All the populations were not in Hardy Weinberg Equilibrium probably due to outbreeding that leads to heterozygosity excess. This observation was further supported by heterozygosity excess exhibited by 100% of the population-locus combinations (mean FIS, -0.30) and lack of  evidence for genetic bottleneck. The populations exhibited high genetic diversity as evidenced by high mean Shannon information Index (I=1.64) and high observed heterozygosity (Ho = 0.98). Genetic relationships among the populations appear to be less  influenced by geographical distance (Mantel’s statistics Z, 0.18; p = 0.6369) implying that the populations do not fit into the  isolation by distance model. Nevertheless, the populations are highly differentiated (FST = 0.17; AMOVA among populations = 16%). This is supported by inter-deme migration of less than one individual per generation (Nm=0.91) as determined by Slatkin’ private allele method. Therefore, these populations are probably still large and distinct requiring separate monitoring  and management due to inferred restricted gene flow and considerable population differentiation.Keywords: Mpasa, Lake Malawi, population structure, genetic diversity, microsatellites, threatened species, conservation

Experimental evaluation of influence of FADs on community structure and fisheries in coastal Kenya

Fish aggregating devices (FADs) have been widely used by commercial fisheries to increase the catchability of pelagic stocks in the open sea. FADs have the potential to enhance nearshore small-scale fisheries where stocks are often overfished. This study examined changes in catch composition, abundance, catch and effort, and aspects of diversity in Kenya's nearshore coastal fisheries after deployment of anchored fish aggregating devices (AFADs). The study combined both fishery independent and dependent methods in assessing changes in fish assemblages post-deployment. Results showed orders of magnitude increase in length, weight, commercial value, and catch per unit effort (CPUE) of landed catch after deployment of FADs suggesting that FADs had a positive effect on the local fishery. Species richness at FAD sites increased post-deployment (n = 281) compared to pre-deployment values (n = 223). Simultaneous use of several complementary structural indices may be required in order to accurately describe and monitor fish assemblages around the FADs. The findings suggest that AFADs are capable of creating both short and long-term impacts on livelihoods, with the potential to deflect pressure on the overfished nearshore fish stocks. However, more research will be needed on redistribution of fish around FADs, design and placement configuration, and site selection amongst others

Testing a global standard for quantifying species recovery and assessing conservation impact.

Recognizing the imperative to evaluate species recovery and conservation impact, in 2012 the International Union for Conservation of Nature (IUCN) called for development of a "Green List of Species" (now the IUCN Green Status of Species). A draft Green Status framework for assessing species' progress toward recovery, published in 2018, proposed 2 separate but interlinked components: a standardized method (i.e., measurement against benchmarks of species' viability, functionality, and preimpact distribution) to determine current species recovery status (herein species recovery score) and application of that method to estimate past and potential future impacts of conservation based on 4 metrics (conservation legacy, conservation dependence, conservation gain, and recovery potential). We tested the framework with 181 species representing diverse taxa, life histories, biomes, and IUCN Red List categories (extinction risk). Based on the observed distribution of species' recovery scores, we propose the following species recovery categories: fully recovered, slightly depleted, moderately depleted, largely depleted, critically depleted, extinct in the wild, and indeterminate. Fifty-nine percent of tested species were considered largely or critically depleted. Although there was a negative relationship between extinction risk and species recovery score, variation was considerable. Some species in lower risk categories were assessed as farther from recovery than those at higher risk. This emphasizes that species recovery is conceptually different from extinction risk and reinforces the utility of the IUCN Green Status of Species to more fully understand species conservation status. Although extinction risk did not predict conservation legacy, conservation dependence, or conservation gain, it was positively correlated with recovery potential. Only 1.7% of tested species were categorized as zero across all 4 of these conservation impact metrics, indicating that conservation has, or will, play a role in improving or maintaining species status for the vast majority of these species. Based on our results, we devised an updated assessment framework that introduces the option of using a dynamic baseline to assess future impacts of conservation over the short term to avoid misleading results which were generated in a small number of cases, and redefines short term as 10 years to better align with conservation planning. These changes are reflected in the IUCN Green Status of Species Standard

Preliminary examination of hatching season and growth of Engraulicypris sardella (Pisces: Cyprinidae) larvae and juveniles in Lake Malawi

The hatching period and the growth of Malawian cyprinid Engraulicypris sardella larvae and juveniles collected from two sites along the southwestern shoreline of Lake Malawi were investigated using otolith increment information. The lapillus was used to determine the age in days following previous studies. The hatching months of fish estimated on the basis of lapillus increment counts were from November to July (nine months of a year), demonstrating that this species had an extended spawning season. Based on the age analysis, the fish were separated into two hatching groups: fish that hatched in the rainy season and those that hatched in the dry season. The growth rate of the former (0.70 mm TL per day) was significantly higher than the latter (0.52 mm TL per day). This growth difference was considered to be due to water temperature in the lake.Keywords: Engraulicypris sardella larvae and juveniles, lapillus increments, growth, spawning season, Lake Malaw

Does Paying for Aquatic Resources Matter? A Case of an African Riverine Ecosystem

Valuation of environmental goods and services has an important role to play in the protection and conservation of riverine resources. However, the literature shows a dearth of information regarding factors that influence people’s willingness to pay (WTP) for riverine resources. This research study was undertaken to find out key factors that affect the willingness of people to pay for the conservation of aquatic resources in the lower section of the Linthipe River in Malawi. Data was collected through household interviews, focus group discussions, key informant interviews, and contingent valuation (CV) surveys. The study noted that communities were willing to offer $3.51 per year for the conservation of aquatic resources in the river. This study established that the people’s WTP is a function of education level, household usage of the goods and services, community support in the management of the resources, household income, and distance of the household from the river ecosystem. The study further discovered that the pay-out level of the users along the Linthipe River was driven by household usage of resources from the river, period of stay in the area, and level of household income. Our recommendation is that government and development partners should popularize the important role played by rivers and streams to surrounding communities and beyond to appeal for more support from users. The authorities must further empower the communities along the rivers and streams to sustainably manage the aquatic resources for the continued appreciation of aquatic resources by future generations

Modeling Diet Decisions for People Living with HIV in Consideration of Age, Weight, Height, and Gender Constraints

Research Article published by Scientific & Academic PublishingPeople living with HIV as well as AIDS patients, who do not receive proper and timely medical treatment, are open targets for all kinds of other infections owing mainly to their relatively weak immune systems. We emphasizes upon the fact that, in most (if not all) such cases, poor nutrition intensifies the progression of the disease and that achieving basic nutritional recommendations is important at all stages of the disease. This paper aims to develop a cost-effectiveness computing model (mathematical model) in diet decisions for people living with HIV in consideration of age, weight, height, and gender constraints. The consideration of these factors tends to avoid undertaking/overtaking of the nutrients which may lead to more serious problems. This model combines multiple linear regression model and linear programming model. The multiple linear regression model predicts the nutrient requirements in the human body of the factors age, weight, height, and gender. The multiple linear regression model gives out the maximum allowable amount of nutrients (upper bound) and minimum amount of nutrients required (lower bound). These results are used to restrict some constraints in the linear programming model, while others are restricted to the maximum allowable amount of foods. From the linear programming model adequate amount of foods that achieve the nutrients recommended are computed. The linear programming problem formulated is solved by the two phase simplex method in MATLAB. Results show that multiple linear regression predicted values are close enough to the actual recommended dietary/daily intake values. The optimal nutrients are reached at much less cost when the multiple linear regression predicted values are used as nutrient recommendations to restrict the constraints in linear programming model compared to when actual recommended dietary/daily intake values are used. Since our model gives adequate amount of foods at much less cost than when the actual values are used then this justifies that our goal has been successful reached. The mathematical model developed could potentially be extended to different groups of people who must manage their diets and therefore promises to have a wider applicability