Browsing by Author "Munga, Cosmas N."

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    Small-Scale Fisheries of the Tana Estuary in Kenya
    (Western Indian Ocean Journal of Marine Science, 2021-12-23) Manyenze, Fatma; Munga, Cosmas N.; Mwatete, Chrisestom; Mwamlavya, Hamadi; Groeneveld, Johan C.
    The role of small-scale fisheries in maintaining socio-ecological systems (SES) in the Western Indian Ocean is well-documented, yet few studies have addressed estuarine fisheries in the region. Small-scale fisheries in the Tana Estuary in Kenya are described in this paper, accounting for location along a salinity gradient, seasonality, gear types used, species composition and relative abundance of landings. Monthly shore-based sampling was undertaken at four locations in 2017 – Ungwana Bay near the estuary mouth, lower and mid-estuary, and upper estuary at Ozi village, ⁓10 km upstream. Fishing gear comprised of seine nets, gillnets, hook-and-line and traditional gear such as self-made traps, sticks and spears operated from the shore (foot fishers), dugout canoes, dhows and fibreglass boats with outboard engines. A total of 12,840 fish and crustacean specimens belonging to 89 species in 45 families were sampled. Landings were dominated by catfishes Arius africanus (31 %) and Clarias gariepinus (21 %), small pelagic fishes Pellona ditchela (10 %) and several sardine species (⁓5 %), croaker Otolithes ruber (10 %), eel catfish Plotosus limbatus (6 %), mullet Mugil cephalus (4 %) and Nile tilapia Oreochromis niloticus (4 %). Multivariate analyses (nMDS and ANOSIM) found that fishing gear (p < 0.05) and location (p = 0.001) significantly influenced catch composition, but season (p = 0.146) was not significant. Traps were used in the upper and mid estuary only and were selective for three catfish species. Seine nets (54 species) and gillnets (40 species) were least selective and used at all four locations. Rarefaction curves indicated that species diversity was higher at the bay and lower estuary than the mid and upper estuary, and that diversity was highest for canoe-gillnet and canoe-encircling net combinations. Catch rates (avg. of 2.3 to 8.4 kg.fisher-1.day-1) depended on gear type and was highest for monofilament gillnets. Catches comprised a broad size range of multiple species, but on average, seine nets selected smaller individuals than traps, gillnets and long lines. The high complexity and organization of the fishery at an estuary-scale makes it a good example of a relatively intact SES suitable for regional comparative analyses.
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    The Biology of Goldsilk Sea Bream (Family: Sparidae) from the Inshore Waters of North Coast Kenya
    (Western Indian Ocean Journal of Marine Science, 2019-11-21) Anam, Rashid O.; Munga, Cosmas N.; Gonda, James R.
    The biology of the sparid, Acanthopagrus berda (goldsilk sea bream) was investigated using catch samples obtained from artisanal fishers at selected fish landing sites in the Marereni and Ngomeni fishing areas on the north coast of Kenya. This species has not previously been studied in Kenya although it forms significant proportions of artisanal fish landings and is also a promising aquaculture species. In order to contribute to knowledge of this species, the length-weight relationship, condition factor and feeding preference for prey items were studied in a total of 751 specimens sampled from July 2013 to July 2014. Length-weight relationships for male and female individuals from both fishing areas were strongly correlated (Males: Marereni - R2 = 0.920, Ngomeni - R2 = 0.983; Females: Marereni - R2 = 0.966, Ngomeni - R2 = 0.941). The condition factor of mixed sexes was not significantly different between the two fishing areas (Marereni 2.15 ± 0.08; Ngomeni 2.05 ± 0.02) at p > 0.05. Gut content analysis recorded a total of 5 taxa in the diet (gastropods, molluscs, detritus, crustaceans and fish). The overall sample was dominated by female individuals with an overall sex ratio of females (405 individuals) to males (338 individuals) of 1:0.8 being significantly different at p < 0.05. The species exhibited isometric and positive allometric growth patterns, indicative of the physiological well-being of this species on the north coast of Kenya. Gonadal maturation occurred throughout the year with peaks in July, August and September. However, more work is needed on the biology, distribution, spawning grounds, behavior, and migration patterns along the Kenyan coast.
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    The Value of Long-Term, Community-Based Monitoring of Marine Turtle Nesting: A Study in the Lamu Archipelago, Kenya
    (Cambridge University Press, 2017-08-01) Olendo, Mike I.; Okemwa, Gladys M.; Munga, Cosmas N.; Mulupi, Lilian K.; Mwasi, Lily D.; Mohamed, Hassan B.; Sibanda, Mxolisi; Ong'anda, Harrison O.
    Monitoring of nesting beaches is often the only feasible and low-cost approach for assessing sea turtle populations. We investigated spatio-temporal patterns of sea turtle nesting activity monitored over 17 successive years in the Lamu archipelago, Kenya. Community-based patrols were conducted on 26 stretches of beach clustered in five major locations. A total of 2,021 nests were recorded: 1,971 (97.5%) green turtle Chelonia mydas nests, 31 (1.5%) hawksbill Eretmochelys imbricata nests, 8 (0.4%) olive ridley Lepidochelys olivacea nests and 11 (0.5%) unidentified nests. Nesting occurred year-round, increasing during March–July, when 74% of nests were recorded. A stable trend in mean annual nesting densities was observed in all locations. Mean clutch sizes were 117.7 ± SE 1 eggs (range 20–189) for green turtles, 103 ± SE 6 eggs (range 37–150) for hawksbill turtles, and 103 ± SE 6 eggs (range 80–133) for olive ridley turtles. Curved carapace length for green turtles was 65–125 cm, and mean annual incubation duration was 55.5 ± SE 0.05 days. The mean incubation duration for green turtle nests differed significantly between months and seasons but not locations. The hatching success (pooled data) was 81.3% (n = 1,841) and was higher for in situ nests (81.0 ± SE 1.5%) compared to relocated nests (77.8 ± SE 1.4%). The results highlight the important contribution of community-based monitoring in Kenya to sustaining the sea turtle populations of the Western Indian Ocean region.