Analysis of fish catch data from 1985 to 1994 in the Kenyan inshore marine waters

Fish landing data collected by the Kenyan Fisheries Department from the nearshort coastal marine waters from 1985 to 1994 were statistically analyzed to determine trends in the traditional fisher's catch. Over the ten year period a significant decline occurred for total catch and for catches of seven commercially important fish families: Lethrinidae, Siganidae. Lutjanidae, Scaridae, Carangidae, Scombridae and Mullidae. 1994 registercd the lowest catch over ten years. The total catch for all the fish declined from a mean annual catch of 6150 metric tonnes in the 1980's to a mean of 5141 metric tonnes in the 1990's with the catch for 1986 being 2 times higher than that of 1994. Although Mombasa district had the highest mean annual landing, its total landings like that of Lamu and Kwale districts decreased over the years. However, Kilifi district showed a steady increase in catches over the years. The changes in fish landings is thought to be caused by lack of appropriate fishing regulations, leading to overfishing of the lagoonal reefs beyond their maximum sustainable yields

Genetic diversity and population structure of the African catfish, <i>Clarias gariepinus</i> (Burchell, 1822) in Kenya: implication for conservation and aquaculture

African catfish, Clarias gariepinus, is an important species in aquaculture and fisheries in Kenya. Mitochondrial D-loop control region was used to determine genetic variation and population structure in samples of C. gariepinus from 10 sites including five natural populations (Lakes Victoria (LVG), Kanyaboli (LKG), Turkana (LTA), Baringo (LBA) and Jipe (LJP), and five farms (Sangoro Aquaculture Center (SAN), Sagana Aquaculture Centre (SAG), University of Eldoret Fish Farm (UoE), Kibos Fish Farm (KIB), and Wakhungu Fish Farm (WKU)) in Kenya. Similarly, samples from eight localities (four natural populations: LVG/LKG, LTA, LBA, and four farmed: SAN, SAG, KIB, UoE) were genotyped using six microsatellite DNA loci. For the D-loop control region, samples from natural sites exhibited higher numbers of haplotypes and haplotype diversities compared to farmed samples, and 88.2% of haplotypes were private. All except LJP and LTA shared haplotypes, and the highest number of shared haplotypes (8) was detected in KIB. The 68 haplotypes we found in 268 individuals grouped into five phylogenetic clades: LVG/LKG, LTA, LBA, LJP and SAG. Haplotypes of farmed C. gariepinus mostly have haplotypes typical of LVG/LKG, and some shared haplotypes of the LBA population. Microsatellite analysis showed farmed samples have higher numbers of alleles than natural samples, but higher observed and expected heterozygosity levels were found in samples of natural populations. Fifteen pair-wise comparisons had significantly different FST values. All samples were in Hardy-Weinberg equilibrium. Samples from the eight localities grouped into four genetic clusters (LVG/LKG, LTA, LBA and SAG), indicating genetically distinct populations, which should be considered for aquaculture and conservation

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

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

Estimation of Age, Growth Parameters and Mortality Indices in Lutjanus fulviflamma (Forsskal 1775) (Pisces: Lutjanidae) from Kenyan Inshore Marine Waters

Age and growth parameters of the reef fish Lutjanus fulviflamma have been estimated from tri-monthly plots of length frequency data and a knowledge of the spawning time of the fish. The growth parameters, L&infin;, K and to were derived from the progression of modal lengths as; 35.0 cm (total length), 0.59 and -0.55 years, respectively. These parameters were used to fit a von Bertalanffy growth equation for the species as: Lt = 35.0 [1 - exp(1 - (0.59 (t + 0.55))]. The total mortality (Z), fishing (F) and natural (N) mortality coefficients were derived for the species from length converted catch-curve and Pauly\'s empirical formula as, 1.97, 0.27 and 1.70/year, respectively. The low fishing mortality (on a 0-1 scale), together with low exploitation rate(Eopt) of 0.137, derived for the stock of L. fulviflamma in Kenya\'s nearshore fishery suggests that the stocks are under exploited. The possible reasons for this under-exploitation are discussed. It is recommended that the growth parameters derived in this study be validated further in order to allow the application of this rapid age assessment method for other species in the Western Indian Ocean, given the difficulties of aging tropical fishes. Journal of Agriculture, Science and Technology Vol.3(1) 2001: 53-6

Seasonality in fish assemblage structure in an East African mangrove creek

The spatial and seasonal structures of fish assemblages in a tropical mangrove tidal creek, Tudor, Kenya, were analysed from monthly survey data, extending from October 2007 to July 2008, and covering the north-east (NEM; October–March) and south-east (SEM; April–July) monsoon seasons. A total of 2 118 individuals, representing 84 species belonging to 49 families, were caught. Gerres oyena, Terapon jarbua and Lutjanus fulviflamma were the dominant species in all seasons. There was within-creek seasonal variability in species abundance and diversity. Overall, the mean density (individuals m–2 ) was higher during the SEM season (0.368; SE 0.078) than the NEM season (0.255; SE 0.041). The NEM season had significantly more species (n = 69) than the SEM season (n = 63) ( χ2 = 317.891, p &lt; 0.0001). Two-way ANOVA indicated the influence of season and habitat on abundance of some species. The abundance of creek-resident species was significantly influenced by site whereas abundance of creekdependent and transient species was influenced by interaction between seasons and stations. Bray-Curtis cluster analysis defined two species assemblages, reflecting differences in temporal and spatial use of the creek by the fish species. Correspondence analysis indicated that seasonal fish assemblages were only distinct at the mouth of the creek with less clear seasonal structure in the upper region of the creek.Keywords: conservation, habitat functions, seasons, species abundanceAfrican Journal of Marine Science 2013, 35(2): 163–17

Patterns of juvenile reef-fish recruitment in Kenya’s shallow fringinglagoon reefs

Studies to understand local-scale patterns in the recruitment of juvenile coral-reef fishes within the western Indian Ocean (WIO) region are few, yet such knowledge is important in fisheries management. Underwater visual census surveys were conducted at five shallow fringing-lagoon reef sites along the Kenyan coast, between June 2012 and March 2016, to quantify patterns in the abundance of new recruits and juveniles. Recruitment was observed year-round, with a consistent pronounced seasonal peak in recruit densities and species richness during December to April of each year, which was strongly correlated with high sea temperatures. Annual variations in recruitment were also observed, with a higher recruitment peak in 2013 as compared with in other years. A total of 112 species belonging to 19 families were identified, dominated by species belonging to the Pomacentridae, Labridae and Apogonidae, which altogether represented 91% of the total number of recruits recorded. The species with the largest number of recruits (Chromis viridis, Thalassoma hebraicum and Gomphosus caeruleus) showed evidence of year-round recruitment, although the timing of recruitment peaks was not consistent. Multivariate analysis of the species composition separated mainland from offshore fringing-reef sites, and also revealed strong habitat associations, pointing towards increasing recruit abundance with increasing live hard-coral cover and rugosity. Live hard-coral cover, which constituted an average of 21%, was associated with 63% of the total number of recruits recorded. This study contributes new insight into local-scale patterns of juvenile reef-fish recruitment in Kenya and the WIO region, and demonstrates the important nursery function of shallow fringing-lagoon reefs.Keywords: fish assemblage, habitat associations, nursery habitat, spatio-temporal variability, underwater visual census, western Indian Ocea

Alongshore distribution and abundance of fish larvae off the coast of Kenya

Knowledge is limited on the fish larval assemblage in shallow lagoonal reefs along the Kenyan coast. Fish larvae from five lagoons, spanning 120 km on the Kenyan coast, were sampled in March 2007 and April 2008 to compare interannual spatial variations in species composition, abundance and diversity along the coast. In all, 2 644 fish larvae were sampled, comprising 26 families and 37 species in 2007 and 43 families and 73 species in 2008. The larval assemblage was dominated by Gobiidae, Blenniidae, Pomacentridae and Gerreidae during both years. Larvae hatched from non-pelagic mode of spawning constituting 92% of total numbers. Mean larval abundance (no. 100 m–3 ± SE) along the coast ranged from 5.0 ± 1.0 to 414 ± 226, with highest densities occurring on the northern sites of Watamu (414 ± 226) and Malindi (31 ± 10). Interannual variation in larval abundance between 2007 (2.17 ± 0.3) and 2008 (2.16 ± 0.1) was not significant (p > 0.05). Shannon-Wiener species diversities between sites ranged from 1.2 ± 0.4 to 2.3 ± 0.3, with highest diversities occurring in Mombasa (2.2 ± 0.5) and Nyali (2.3 ± 0.3). In 2007, the occurrence of preflexion larvae increased northwards from Mombasa (18.2%) to Watamu (86.4%), whereas in 2008, the reverse was the case with the incidence of preflexion larvae reducing northwards from Mombasa Marine Park (76%) to Watamu Marine Park (2%). These trends indicate interannual variation in larval source sites for fish species. Correspondence analysis revealed distinct larval assemblages at sites along the coast, which varied between years. Keywords: abundance, alongshore, diversity, fish larval assemblages, reef lagoonsAfrican Journal of Marine Science 2010, 32(3): 581–58

Morphometric variation in the cutlassfish Trichiurus lepturus on the Kenyan coast: implications for stock identification and management

Morphometric variation was used to study population structure of the cutlassfish Trichiurus lepturus on the Kenyan coast. In all, 16 morphometric measurements taken from 193 individuals from six sites were subjected to multivariate statistical analysis in order to determine possible stock differentiation. Multivariate analysis of variance indicated significant differences in the means of a combination of the morphometric characters among the sites, and discriminant function analysis by groups showed the presence of phenotypically distinct populations on the south and north coasts of Kenya. A classification tree analysis of morphometric characters validated the distinct groups and indicated certain characters to be useful for classifying specimens to source sites. The likely presence of distinct north and south stocks of T. lepturus on the Kenyan coast observed in our study will require validation by other methods, but indicates the potential need for spatially explicit models for managing fish populations on a large spatial scale.Keywords: bottom trawl, fisheries management, gillnets, morphometrics, multivariate analysi

Spatial Variation in Growth and Mortality Parameters of the Marbled Parrotfish, Leptoscarus Vaigiensis (Quoy and Gaimard, 1824) on Different Reefs Along the Kenyan Coast

Growth and mortality variations of Leptoscarus vaigiensis (Quoy and Gaimard, 1824) was studied among six reef sites exposed to different fishing pressure in coastal Kenya in order to test the hypothesis of phenotypic plasticity. Monthly fish samples were obtained from marine parks (protected or no-take areas), marine reserves (partially protected areas) and non-protected reefs from May 2011 to April 2013. Measurements for total lengths (cm) and body weights (g) were recorded. Growth (K, L∞) and mortality (Z, M, F) parameters of the species were determined using the ELEFAN I program and compared between sites. Results showed higher asymptotic length (L∞) esƟmate (~ 31 cm) for parrotfish from the reserve site and lowest estimate (26-27 cm) from the marine park site indicating that the potential for growth is influenced by factors other than levels of protection. Fish from park sites had equal but lowest growth rates (K yr-1) of 0.46 compared to 1.73 ± 0.11 and 1.36 ± 0.84 for fish from non-protected and reserve sites, respectively. As expected, total mortality estimates (Z yr-1) were lower for protected areas (1.69-1.96) and higher for reserve (2.87-9.15) and non-protected (4.39-5.30) sites. This study showed divergence of growth parameters of a coral reef fish exposed to different levels of fishing pressure, thereby providing insights into the possibility of utilizing the parameters as indicators of environmental stress