Department of Environmental and Health Sciences

PATTERNS OF JUVENILE REEF FISH DIVERSITY ACROSS A MANGROVE-SEAGRASS-CORAL REEF CONTINUUM IN SOUTH COAST KENYA

2025-01-01T00:00:00Z

PATTERNS OF JUVENILE REEF FISH DIVERSITY ACROSS A MANGROVE-SEAGRASS-CORAL REEF CONTINUUM IN SOUTH COAST KENYA OTIENO, DENNIS Studying assemblage patterns of juvenile fishes across ecologically connected habitats is necessary for understanding connectivity. Mangroves, seagrass beds, and coral habitats are ecologically essential for the survival of juvenile fishes. These habitats are connected through various mechanisms related to larval supply, ontogenic feeding, juvenile migration, and opportunistic adult phases. A mangrove-seagrass-coral reef continuum on Kenya's south coast was investigated to assess connectivity using juvenile fish assemblages. Between August 2021 and August 2022, a beach seine was used to collect samples monthly for two days. Fish species diversity across habitats was determined using Shannon-Weiner diversity index (H'). Detrended Correspondence Analysis (DCA) was applied to investigate species associations with the three habitats. The trophic level of each fish species was obtained from FishBase. Sea surface temperature and salinity were measured monthly at each site using a YSI multi-parameter probe. Species associations with temperature and salinity were assessed using Canonical Correspondence Analysis (CCA). A total of 8,575 fish specimens representing 228 species from 52 families were recorded. The coral reef habitat had the most individuals (n = 3,186) and was the most species-rich (168 species), followed by seagrass (2,420 individuals, 132 species) and mangrove (1,783 individuals, 119 species). Significant differences in species diversity were observed across the habitats during the northeast monsoon (NEM) and the southeast monsoon (SEM) (p = 0.026). The Kruskall -Wallis test showed no significant differences in the mean number of individuals per haul across habitats H (2, N = 60) = 4.81, p = 0.090). It also showed no significant difference in the mean number of individuals per haul between seasons H(1, N=60) = 2.10, p = 0.150). A two-way ANOVA revealed significant differences in fish diversity across the habitats (df = 2; f = 5.677; p = 0.006). Pair-wise comparison using Tukey HSD test revealed differences in species diversity between the coral and mangrove habitats (p = 0.044), but no significant differences in species diversity between seasons (df = 1; f = 0.818; p = 0.097). Overall, 69 fish species were common across the three habitats. DCA results revealed a strong association of species Pempheris mangula, Yarica hyalosoma, Pristotis obtusirostris, Taeniamia fucata, and Apogon fragilis to mangrove habitat. CCA results showed a positive relationship with increased temperature in the mangrove habitat represented by Apogon fragilis and Taeniamia fucata, while species, such as Siganus luridus and Sphyraena barracuda, showed a positive relationship with increased salinity in seagrass habitat. The Kolmogorov-Smirnov (K-S) tests revealed no significant difference in trophic signatures between the mangrove and seagrass habitat (D = 0.2308; p = 0.4402), but a significant difference between the mangrove and coral habitat (D = 0.5385; p = 0.00055) as well as between the seagrass and coral habitat (D = 0.4615; p = 0.004906). This study demonstrates the existence of connectivity across a mangrove-coral seagrass continuum in Shimoni and recommends long-term studies on nearshore habitat connectivity for better conservation and management strategies, including ecosystem-based fisheries management.

COMPARATIVE GROWTH PERFORMANCE OF WILD JUVENILE SHOEMAKER SPINE-FOOT RABBITFISH (SIGANUS SUTOR) UNDER EXPERIMENTAL FEEDING WITH MACROALGAE DIETS

2025-01-01T00:00:00Z

COMPARATIVE GROWTH PERFORMANCE OF WILD JUVENILE SHOEMAKER SPINE-FOOT RABBITFISH (SIGANUS SUTOR) UNDER EXPERIMENTAL FEEDING WITH MACROALGAE DIETS BACHA, NAJDA ATHMAN Aquaculture is considered to offer one of the most crucial platforms for producing aquatic food on a worldwide scale. Over the years, there has been an increased dependency on fishmeal and soybean as the main protein ingredients in the aquafeed industry. Therefore, there is a need for an alternative source of protein in the aquafeed sector that is cost-effective and reliable. This study aimed to provide data on the comparative growth performance of cultured shoemaker spine-foot rabbitfish (Siganus sutor) under experimental feeding using three selected diets to recommend affordable alternative protein sources in fish diets. A semi-structured interview using questionnaires was conducted in Mkunguni, Kibuyuni, and Shimoni BMUs to assess the type of potential marine macroalgae where 62 fishers participated in identifying these naturally occurring marine macroalgae used as bait in the basket trap fishery. Proximate analysis for the macroalgae species used as bait was performed. Three diets were formulated: treatment I contained 100% macroalgae (macroalgae diet), treatment II contained 0% macroalgae (fishmeal diet) and treatment III contained 50% each of macroalgae and fish meal (mixed diet). Juvenile Siganus sutor individuals were collected from the wild and transported to the KMFRI lab and stocked in different flow-through systems of 1000-litre plastic tanks at a stocking density of 20 individuals/m3, and experimental feeding was conducted. Initial measurements of fish specimens were recorded using a graduated fish measuring board and electronic weighing balance for total length (cm) and individual weight (g). Sampling of fish specimens for growth was done bi-weekly for 28 days. Proximate results indicated the highest protein content in macroalgae species Fischerella sp. compared to that in Chondrophycus papillosus and Chaetomorphus crassa thus Fischerella sp. was selected for feed formulation. Fish growth in all feed treatments varied in mean body weight. Fish specimens fed with macroalgae diet (T1R1) recorded the highest total weight gain at 25.6 g followed by mixed diet (T3R1) and fishmeal diet (T2R2) at 19.8 g and 17.2 g, respectively over the experiment period. Fish fed with a mixed diet recorded the fastest growth in terms of total length gained by 0.41 cm, followed by macroalgae diet with 0.23 cm whereas fish fed with fishmeal had a decrease in mean total length by 0.05 cm. More results indicated fish specimens fed on fishmeal significantly differed in overall weight from those fed on a macroalgae diet and mixed diet (p < 0.05). However, no significant difference was observed in the overall weight of fish specimens between those fed on a macroalgae diet and those fed on a mixed diet (P > 0.05 in both cases). The highest survival rate was recorded in fish fed with a macroalgae diet at 83.0%, followed by mixed diet and fishmeal at 81.3% and 69.3%, respectively. Macroalgae diet was most proficiently utilized with a food conversion ratio (FCR) of 1.59. Siganus sutor individuals in experimental treatments II (fishmeal) and III (mixed diet) were not in good condition with condition factor (K) at -19.78 and -29.92, respectively. Based on these results, it is evident that using a macroalgae diet offers promising returns in terms of S. sutor survival rate compared to fishmeal although with higher growth performance.

SELECTIVITY OF HOOK SIZE ON LETHRINIDS IN THE SMALL-SCALE HOOK AND LINE FISHERY ALONG COASTAL KENYA

2025-01-01T00:00:00Z

SELECTIVITY OF HOOK SIZE ON LETHRINIDS IN THE SMALL-SCALE HOOK AND LINE FISHERY ALONG COASTAL KENYA NDIRITU, EVERLYNE NYAKINYUA Hook and line are commonly used fishing gear in Kenya’s small-scale coastal and marine fishery. The most abundant catches of this gear is made up of the fish family Lethrinidae. Despite this wide usage of the gear along the Kenya coast, there is still limited information on the effect of various sizes of hooks used in the hook and line fishery on the target fish species. Therefore, this study assessed the sustainability of the small-scale hook and line fishery on lethrinids by evaluating mortality and exploitation rates, proportion of immature and undersized fish individuals landed and catch per unit effort (CPUE) variations. Shore-based fish catch surveys were conducted for ten days in a lunar month from July to December 2021 in the selected fish landing sites of Mkunguni, Mwaembe, Kanamai and Mtwapa along the Kenya coast. Hook sizes were categorized into three groups based on the standard numbering system and comprised of large (No. 6 - 8), medium (No. 9 - 11) and small (No. 12 - 14) hooks. Four lethrinid fish species dominated the catches, Lethrinus borbonicus, Lethrinus lentjan, Lethrinus rubrioperculatus and Lethrinus mahsena, and collectively accounted for 77.7% of the total fish landings. L. lentjan was found to be heavily overexploited, L. borbonicus lightly overexploited and L. rubrioperculatus and L. mahsena underexploited, compared to different yield-based exploitation rates reference points. Lengths at first capture (Lc) for these four species were less than length at maximum yield per recruit (Lopt) and length at first maturity (Lm). Proportions of individuals below Lm and Lopt were high in small hooks (41-71% and 49-77%) compared to medium (35-51% and 45-62%) and large (<11% and 3-19%) hooks, respectively. The CPUE differed significantly across hook size groups and landing sites (p < 0.01) but not between seasons (p = 0.846). The high exploitation rate for L. lentjan suggests the need for management measures to be put in place that will prevent the stock from collapsing. The high vulnerability of L. mahsena to over exploitation warrants precautionary management measures to maintain light levels of exploitation for this species. The high proportion of individuals below Lm and Lopt of lethrinid species caught by small and medium hooks suggests that these hook sizes are causing recruitment and growth overfishing. Based on the results from this study, large hooks which captured low number of individuals below Lm and Lopt and resulted in higher CPUE should be trialed for use through gear modification to ensure the protection of the highly overexploited and vulnerable lethrinid species for sustainability in the fishery. Longer term studies covering larger fishing areas and depth distribution of target species are needed to develop comprehensive recommendations for the sustainable management of small-scale hook and line fishery in coastal Kenya.

FACTORS INFLUENCING CONTRACEPTIVE USE AMONG WOMEN OF REPRODUCTIVE AGE IN KENYA

2024-01-01T00:00:00Z

FACTORS INFLUENCING CONTRACEPTIVE USE AMONG WOMEN OF REPRODUCTIVE AGE IN KENYA NYAKUNDI, JANE BITUTU Kenya has one of the most effective family planning strategies in Sub-Saharan Africa. Contraceptive awareness in Kenya is relatively high but the uptake is still low indicating that the unmet needs still exist. Kenya is one of the top countries in the continent with more than 52 million people and it’s one of the most populous nations in Africa. The goal of the current research was to pinpoint the factors influencing Kenyan women within the ages of 15 and 49 who use contraception. This research study relies on secondary data obtained from a cross-sectional study done by the big project Performance, Monitoring Accountability for Action 2019 survey. The National Council for Science, Technology, and Innovation (NACOSTI) and the Kenyatta National Ethics and Research Committee (KNERC) provided ethical approval for data collection and all participating counties were administratively responsible. The research project's sample included 9,477 women of reproductive age (WRA) from 11 of Kenya's 47 counties. It was carried out utilizing the multistage cluster approach. Data was analyzed using Stata 16.1 analysis software, which generated frequency tables and pie charts. Logistic regression was performed to determine the relationship between Modern Contraceptive Method (MCM) intake and its factors ,95% confidence interval and a 0.05 p-value were used to show the variable correlations. About 39% of the respondents in the survey were aged 15-24 years, more than half 53.4% of the women were married and 4.5% of respondents had no formal education. Women in the middle quintile of wealth had significantly higher (aPOR 1.3, 95% C.I. 1.04, 1.57, p=0.017) odds of using MCM than women in the lowest wealth class and rural respondents were substantially less likely to use modern methods of contraception (aPOR 0.8, 95% C.I. (0.63, 0.93, p=0.033) than urban women. In comparison to married women, single women had lower odds of using MCM (aPOR 0.5 (95% CI. 0.39–0.56 p=0.000), and Muslims had lower odds (aPOR 0.6 (95% C.I. 0.42, 0.89 p=0.010) of using MCM than Catholics. The provision of family planning (FP) services was shown to be less in NHIF-covered facilities than in non-NHIF-covered ones (aPOR 0.535 (95% CI 0.29, 0.98, p=0.043). In the 11 counties of Kenya, 43.2% of WRA utilize modern contraceptives, and 98.4% of respondents are aware of these options. Contraception use in Kenya is low although MCM awareness is high. Initiatives to be geared towards the 15–19 age group, those from lower socioeconomic classes and people who live in rural areas.