Aquatic weeds hotspots in the Lake Victoria basin Uganda and on Lake Kyoga: implications for their management

Proliferation of invasive aquatic weeds has developed into a major ecological and socio economic issue for many regions of the world. As a consequence, inference on where to target control and other management efforts is critical in the management of aquatic weeds (Ibáñez et al., 2009). Notwithstanding, aquatic systems in Uganda in general and in the basins of Lakes Victoria and Kyoga in particular, have fallen victims to aquatic weeds invasion and subsequent infestation. If these aquatic weeds infestations are to be minimized and their impacts mitigated, management decisions ought to be based on up-to-date data and information in relation to location of infestation hotspots. Aquatic systems in the basins of the two production systems are important sources of livelihoods especially from fish production and trade yet they are prone to infestation by aquatic weeds. Thus, the invasion and subsequent infestation of aquatic ecosystems by aquatic weeds pose a major conservation threat to various aquatic resources (Catford et al., 2011; Kayanja, 2002). This paper examines the extent to which aquatic weeds have infested aquatic ecosystems in the basins of Lakes Victoria and Kyoga. The information is expected to guide management of major aquatic weeds through rational allocation of the scarce resources by targeting hotspots.

Frame survey (census of boats and fishing gear) Lake Kyoga and Lake Kwania (Uganda), May-June 1990

The census of a fishing industry is called a frame survey. This is a rather comprehensive term, because there are many aspects of a fishery which one might wish to know. This is illustrated by the report on the partial census executed by the ADP/FS on the southern landings of L.Kyoga during December 1988, which deals with many socio-economic aspects of fishermen's households.

Socio-economic processes on Lake Kyoga: potentials for participatory management and poverty eradication

The purpose of this paper is to review selected socio-economic aspects of the Kyoga basin lakes with a view to assessing, the potehtials within the fishing communities for participatory management and poverty eradication. This paper is based on information obtained from three categories of activities. First a review of existing data and reports was undertaken to establish existing knowledge on the subject and identify the gaps.

Fishing effort and the impact of fishing gears and fishing methods on fishes and fisheries of Kyoga basin lakes

Lake Kyoga at the time of Worthington Survey (Worthington, 1929) was fished by only natives around it. The fishing gears consisted of locally made basket traps, hooks and seine nets made out of papyrus. Fishing was mainly during the dry season as in wet season, the fishers would revert to crop growing. During 1937 to 1950s Oreochromis variabilis, oreochromis esculentus (Ngege) and Protopterus aethiopicus (Mamba) were the most important commercial fish species and contributed over 95% to the total landings until early 1950s when their proportions started to change as a result of changes in fishing techniques. The tilapiines' were then being caught using mainly basket traps and P.aethiopicus was caught in hooks prior to the mid 1950s.

Yellow Perch Population Assessment in Southwestern Lake Michigan

Division of Fisheries, Illinois Department of Natural Resources Grant/Contract No: Federal Aid Project F-123 R-16

The declining state of the gillnet fishery in Lake Victoria, Uganda

Lake Victoria had a multi-species fishery dominated until the 1970s by the tilapiine and the haplochromine cichlids (Kudhongania and Cordone, 1974). From about 1930 to 1960, the fisheries of Lake Victoria were managed by controlling the mesh size of gill nets. Gill nets of stretched mesh sizes less than 127 mm (5 inches) were prohibited as they cropped immature Oreochromis esculentus (Ngege), the most important commercial species on the lake (Graham, 1929). The catch per night in the legal 127 mm mesh nets was over 30 fish of O. esculentus prior to 1921 but dropped to 6 and 1.5 fish in 1928 and 1954, respectively, (Beauchamp, 1955), indicating overfishing of the stocks. The overall aim of the survey was to determine the available fish stocks being harvested by the gill net fishery. The specific objectives included the determination of the species composition and catch levels. Gill nets of mesh sizes from 25.4 mm (1 inch) to 228.6 mm (9 inches) were used.

Yellow Perch Population Assessment in Southwestern Lake Michigan, Including Evaluation of Sampling Techniques and Identification of the Factors that Determine Yellow Perch Year-Class Strength April 1, 2007 – March 31, 2008

Division of Fisheries, Illinois Department of Natural Resources Grant/Contract No: F-123 R-14

Yellow perch population assessment in southwestern Lake Michigan, including evaluation of sampling techniques and identification of the factors that determine yellow perch year-class strength April 1, 2006 – March 31, 2007

Division of Fisheries, Illinois Department of Natural Resources Grant/Contract No: F-123 R-13

Yellow Perch Population Assessment in Southwestern Lake Michigan, Including Evaluation of Sampling Techniques and Identification of the Factors that Determine Yellow Perch Year-Class Strength April 1, 2008 – June 30, 2009

Division of Fisheries, Illinois Department of Natural Resources Grant/Contract No: Federal Aid Project F-123 R-15

Fishers’ perception on livelihood strategies, adaptation and mitigation measures to cope with changes in climate variables around Lake Wamala, Uganda

Fisheries support livelihoods but are threatened by climate variability and change which intensified since the 1970s. This study used quantitative and qualitative methods to determine the extent to which fishers around Lake Wamala in Uganda were copying with perceived changes in climate variables and the impacts on their livelihoods, to generate knowledge to enable the fishers increase resilience and sustain their livelihoods. Fishers were aware of changes in climate manifested by unpredictable seasons, floods and droughts. Fishing was the main livelihood activity. The African catfish had replaced Nile tilapia as the dominant fish species. There was damage and loss of gear, boats, landing sites and lives, and changes in fish catches and sizes, income and fish consumption during the perceived floods and droughts. The fishers adapted to the changes through increasing time on fishing grounds and changing target species and fishing gears but innovative ones diversified to high value crops and livestock which increased their income beyond what was earned from fishing thus acting as an incentive for some of them to quit fishing. Diversification to non-fishery activities as a form of adaptation was enhanced by membership to social groups, weekly fishing days, fishing experience and age of fishers but its benefits were not equally shared among men and women. Mitigation measures included planting trees, mulching gardens and protecting wetlands. Adaptation and mitigation measures were constrained by limited credit, awareness and land. The required interventions included improving access to credit, irrigation facilities and appropriate planting materials and raising awareness. The study showed that the fishers were aware of changes in climatic variables and the impacts on their livelihoods. There were also adaptation and mitigation measures practiced by the fishers which if promoted and their constraints addressed, could increase resilience of fishers to climatic change and sustain their livelihoods.

The impact of exploitation, competition, and predation on the changing stocks of Lake Victoria

The dramatic decline in fish species diversity in Lake Victoria has been attributed to predation by Nile perch, Lates niloticus Linne, without sufficient justification. Exploitation, interspecific competition and hybridization had profound impact on the decline of the indigenous commercial fish species. The roles of exploitation, competition and hybridization, and of predation by the Nile perch on changes in species diversity have been discussed. Lates was largely responsible only for the decline of the haplochromine stocks.

Annual report on fish production Lake George, Edward and Kazinga Channel (Kichamba Region) 1993/1994

This report gives details of catch assessment statistics of Lakes George, Edward and Kazinga channel plus minor Lakes in western Uganda. Eight districts are covered namely:-Kasese, Bushenyi, Rukungiri, Kabarole, Ntungamo, Mbarara, Kabale and Kisoro. Of the eight districts major lake fishery is in the first four, the rest minor lake fishery as shown below:-Ntungamo- Nyabihoko and Nyakiyanja, Mbarara-Mburo, Kachere and Nakivale, Kisolo- Mutanda, Mulehe, Chahafi and Kayumbu) and Kabale Lake Bunyonyi). Data on Lake Bunyonyi was not availab1e for both 1993/94; however reports say fewer Clarias are caught using basket traps and hooks.

Cast-net fishery on northern portion of Lake Victoria and upper Victoria Nile

This project survey on cost-net was conducted at the Northern portion of Lake Victoria and Upper Victoria Nile. The selected fish -Landing sites, where sampling exercises were carried out include: Loco, Jinja pier (covering Lake Victoria) and Railway bridge, New bridge and Kalange (covering upper Victoria Nile). Research was focused on the cast-net design, target commercial fish stocks, impact of cast-net on the fish stocks, mesh-size and techniques ofcast-netting. The research results show that cast-net fishery destroys fish breeding and nursery grounds and other fish ecosystem. The gear targets Oreochromis niloticus and Occassional by catches e.g. Lates niloticus, Mormyrus Kannume Bagrus docmak and Clarias gariepinus. The multi-panel cast-net of mesh-sizes ranging from i (5lmm) to 6' (152mm) were adaptable by fishermen but they mostly caught immature fish. Nevertheless, this gear showed highest efficiency compared to other gears used at the project area. These research results will be useful to researchers, extension workers and Fishenes, students under taking special research or study on this gear.

Changes in catches and biological characteristics of Nile tilapia (Oreochromis niloticus Linnaeus) in Lake Wamala (Uganda) under changing climatic conditions

There have been changes in catches and biological characteristics of the Nile Tilapia, Oreochromis niloticus (Linnaeus) in Lake Wamala (Uganda) since its introduction and establishment, but the factors which have contributed to these changes are not adequately understood. This study examined changes in catches and biological characteristics of Nile tilapia in relation to changes in temperature, rainfall and lake depth to provide an understanding of the role of changing climatic conditions. There was an increase in minimum, maximum and average temperature since 1980, but only minimum (0.021ºCyr-1) and average (0.018ºCyr-1) showed a significant trend (p < 0.05). Rainfall increased by 8.25 mmyr-1 since 1950 and accounted for 79.5% of the water input into the lake while evaporation accounted for 86.2% of the water loss from the lake. The lake depth was above 4 m during the years rainfall was above normal average of 1180 mm, except during the period 2011-2014. The contribution of Nile tilapia to total catch and CPUE changed with rainfall and lake depth up to 2000, after which they decreased despite increase in rainfall. There was a strong positive correlation between lake depth and average total length of Nile tilapia (r = 0.991, p < 0.001) and length at 50% maturity (r = 0.726, p < 0.001). The length-weight allometry between high and low lake depths was significantly different [t (6) = 3.225, p < 0.05], with Nile tilapia being heavier (for a given length) at high lake depth than at low lake depth. Fecundity of Nile tilapia was higher and egg diameter lower than what is reported in literature. Nile tilapia shifted from algal dominated diet during the wet season to include more insects during the dry season. The study showed that the catches and biological characteristics of Nile tilapia change with climate and hydrological factors and these need to be considered in management of the fisheries of Lake Wamala.

Aspects of the fishery and biology of the African catfish Clarias gariepinus (Burchell, 1822) amidst environmental changes in Lake Wamala (Uganda)

Environmental changes are some of the factors that affect fisheries and biological characteristics of fishes. The African catfish Clarias gariepinus (Burchell, 1822) has biological characteristics that enable it to persist under various stressful environmental conditions. However, few studies have examined how the African catfish responds to conditions created by a changing climate. The study examined some of the fishery and biological characteristics of African catfish in Lake Wamala (Uganda) to provide an understanding of their response to changing climatic conditions using data for the period 1950 - 2013. Temperature around the lake increased by 0.02ºC/year since 1980, commensurate with the regional trend, while rainfall was above average since 1996, except in 2004 and 2008. Lake depth was strongly positively correlated with rainfall (r =0.83, n= 6, p<0.05) up to 2000, after which, lake depth decreased amidst increase in rainfall. The contribution of African catfish increased from 20% to 85% and 17% to 78% respectively to commercial and experimental catches respectively between 1975 and 2013 despite the decrease in lake depth. The modal total length, condition factor, food, and fecundity did not change. Only size at first maturity decreased from 37.5 to 30 cm TL in females and 39.5 to 34.2 cm TL in males between 1999/2000 and 2012/2013. The biological characteristics of the African catfish were comparable with those of the same species in other lakes and remained relatively stable. The results suggested that the African catfish has the capacity to persist and/or adjust appropriately under conditions created by climate variability and change, and if properly managed, can sustain the fisheries of Lake Wamala.