Culture Suitability of Selected Coral Species for the Ornamental Export Market

Coralfarming for home and public reef aquaria, is a sustainable alternative toharvesting them from the reefs which are increasingly threatened by human andenvironmental factors, has received increasing interest during the last decade.This study assessed the culture potential of thespecies Pocillopora damicornis, P. verrucosa, P. eydouxi, Porites rus,Acropora humilis, A. selago and A. verwei by monitoring the survival andgrowth rates of fragments transplanted from the Mombasa Marine Reserve toculture tables deployed about 3m deep in the Mombasa Marine Park for 12 monthsbetween April 2010 and April 2011. The results show that almost all thebranches of the colonies from which culture fragments were cut showed full tissuerecovery after months. Percentage survival after six months of culture for A. humilis, P. eydouxii, P. rus, A. selago, P.damicornis, A. verwei, and P. verrucosa, were 91%, 88%, 80%, 79%,62%, 56% and 29% respectively. Survival increased with the size of the fragmenttransplanted and axial length of more than 2cm was considered to be ideal fortransplanting. High variations of growth rates were observed within the speciesand radial growth (branching width) was higher that axial growth for all thespecies. Standardized annual growth rate determined for healthytransplants was highest for A. selago (29.6±4.1mmand 68.3±8.3mm for axial length and branching width respectively), while thegrowth rate for A. verwei and A. humilis were similar (23.0±7.3mm and52.6±12.5mm and 23.3±8.2 and 53.3±16.5) and P.damicornis had the lowest overall growth rate (13.5±4.7 and 33.8±7.7mm).However, only the growth rates for A.selago and P. damicornis weresignificantly different. The monthly percentage increase in weight for A. selago, A. verwei, A. humilis, P. darmicornis and P.verrucosa were 6.4%, 5.2%, 3.1%, 1.6% and 0.9% respectively. Themain results of the study include biological information on growth and survivalof coral transplants, demonstration and basic methods of establishing mothercolony which can be used as a source for second generation seed for commercialculture. Culturing coral has the possibilities of providing alternativesustainable maritime economic activity to fishing communities

Seasonal variation in the length-weight relationship and condition factor of thirty fish species from the Shimoni artisanal fishery, Kenya

Seasonal variation in the length-weight relationship (LWR) and condition factor were assessed for 3 704 fish specimens constituting 30 fish species belonging to 11 families. The fish were sampled from artisanal fisher catches on the south coast of Kenya between March 2014 and March 2015. The regression results for the LWR were 0.57 for Siganus luridus and 0.97 for Lutjanus argentimaculatus during the northeast monsoon (NEM), and 0.76 for Scolopsis ghanam and 0.98 for Parupeneus macronema during the southeast monsoon (SEM). The ‘b’ values ranged from 1.8 for Siganus luridus to 4.3 for Plectorhinchus gaterinus during the NEM, and 1.4 for Plectorhinchus chubbi to 3.2 for Parupeneus heptacanthus during the SEM. The mean ‘b’ values for the SEM and NEM seasons were 2.73 and 2.63 respectively and significantly differed from 3 (t–test, P < 0.5). Mean condition factors of 0.37 (S.E = 0.01) during the NEM, 0.34 (S.E = 0.01) during the SEM for Hemiramphus far and 0.56 (S.E = 0.03) during the NEM, and 0.59 (S.E = 0.03) during SEM for Cheilio inermis were recorded indicating that these species were feeding poorly, the environment was not conducive, or that high competition for food from other species existed, while the other species had mean condition factors above 1 during the two seasons. The condition factor significantly differed for eleven species during the two seasons (P < 0.05).

Hook size selectivity in the artisanal handline fishery of Shimoni fishing area, south coast, Kenya

Selectivity of five handline fishing hook sizes was determined following Holt’s 1963 model using data that was collected during January to June, 2016. A total of 966 fish specimens comprising of 65 species belonging to 23 families were sampled. Fish abundance was low for large sized hooks while catch rate was higher. Species diversity was higher during the northeast monsoon season and at the study sites of Mpunguti and Nyuli. However, species diversity decreased with increase in hook size. All hook sizes had a higher selection for mature Lethrinus borbonicus while hook size No. 8 selected immature Lethrinus lentjan. Hook sizes No. 9 and 10 selected mature L. lentjan and Lethrinus rubrioperculatus, hook size No. 15 selected immature L. lentjan, L. rubrioperculatus and Aprion virescens, while hook size No. 16 selected immature A. virescens and L. rubrioperculatus. Species similarity was higher for fish caught by hook sizes No. 16 and 15, and No. 8 and 9, while those captured by hook size No. 10 differed from those caught by other hook sizes. The larger hook size No. 8 is recommended for the sustainable exploitation species in the artisanal handline fishery in Shimoni fishing area. Future work needs to consider the effects of bait type and size and the stock status of the fish under exploitation

Reproductive biology and body condition of exploited populations of Emperor Angelfish, Pomacanthus imperator (Bloch, 1787) along the Kenyan Coast

A substantial proportion (in terms of value and quantity) of the Pomacanthus imperator catch on the Kenyan coast are traded, and the species is also harvested as food in the artisanal fishery. However information on their reproductive biology is scanty. The overall sex ratio differed significantly from 1:1 according to chi-square test (p<0.05). Sizes at maturity (L50) were estimated to be 25cm and 28cm TL for females and males respectively. Fecundity was estimated to be in the range of 17,790-266,472 with a Mean ±SE of 79,353±11,747, and was linearly related to total length and ovary weight. March-April was the main period of reproductive activity based on gonad somatic indices and monthly proportion of mature individuals. The LWR indicated isometric growth both in males and females of P. imperator, as the allometric coefficient b values were not significantly different from the expected isometric value of 3 (Student’s t-test; p=0.12). Relative condition factor did not vary significantly between the months sampled. The reproductive parameters obtained from this study provide some baseline information for management of this species which has proven to be highly vulnerable to depletion due to overfishing.

Codend mesh size of beach seine nets influences fish species and size composition in Lamu, north coast, Kenya

AbstractBeach seine nets are commonly used in reef lagoons in Kenya, with potentially destructive impacts on reefs and other habitats. The species composition and size frequency of catches made by nets with codend mesh sizes of 25 mm, 38 mm and 44 mm were evaluated for samples collected during three sampling trips in the Lamu area between 2014 and 2016. A total of 98 fish species belonging to 41 families were recorded. Most species with highest diversity (D = 10.67) were caught by the 25 mm codend mesh, followed by the 38 mm (D = 6.69) and 44 mm meshes (D = 3.04), respectively. Size frequencies of dominant species Leptoscarus vaigiensis, Siganus sutor and Lethrinus lentjan depended on the codend mesh size sampled, with the 25 mm mesh retaining more immature individuals than the other two meshes. It is concluded that codend mesh size influences catch properties of beach seine nets used in Lamu, and that introducing a minimum mesh size would reduce the proportions of juvenile fishes landed. 

Gear-based species selectivity and potential interactions between artisanal and aquarium fisheries in coastal Kenya: implications for reef fisheries management

Due to the multigear, multi-species and open-access nature of most coral reef fisheries in the Western Indian Ocean region, there is a high potential for resource competition and fishing related conflicts, especially in shared fishing grounds. An understanding of resource overlap and competition between different co-occurring fisheries is therefore important for the implementation of ecosystem based fisheries management interventions. In this study, we used multivariate and ecological approaches to evaluate gear competition and interactions between artisanal and  aquarium fishers using a case study of the Shimoni area, southcoast of Kenya. Aquarium fisher catches were monitored from September 2010 to March 2013; while artisanal fisher catches were monitored from January to December 2014. Five artisanal gear types were observed to interact with the aquarium fishery. Non-target species valued by the aquarium trade constituted approximately 12% of the artisanal catches by weight and 10% by relative abundance, and was comprised of 18 fish families and 57 species. Handlines captured the highest number and diversity of non-target species while the lowest was observed for gillnets. The findings contribute towards better understanding of the dynamics of resource overlap between artisanal and aquarium fisheries on a local scale, and provide new insights on the cumulative sources of fishing pressure affecting reef fish populations in Kenya

Current status of sea turtle protection in Lamu Seascape, Kenya: Trends in nesting, nest predation and stranding levels

Temporal and spatial trends in sea turtle nest protection, predation and mortalities in the Lamu archipelago, Kenya were investigated based on nesting beach monitoring efforts conducted among five locations comprising 34 beaches. The nesting data was collected for a period of 17 years from 1997 – 2013 through beach patrols using standardized protocols while mortality data spanned from 2001 – 2013.  The causes of mortality were determined through general external examination. The green turtle, hawksbill, olive ridley and loggerhead turtle were recorded in the area. Out of a total of 2,017 nests recorded, 64.4% (n = 1299) were translocated while 10.2% were predated. Predation levels were not significantly affected by seasonality (p > 0.05); although the levels were lower during the wet Southeast Monsoon (SEM) season (9.2 ± 2.2 %) compared to the Northeast Monsoon (NEM) season (14.8 ± 3.0 %). A total 227 mortality cases were recorded between 2001 and 2013 of which fishery- related causes were the highest representing 53%. This was followed by unknown causes which constituted 20%, shark attacks (13%) and the tumor causing viral disease fibropapillomatosis (11%). Overall, the highest number of mortalities was recorded for Mkokoni (35%) while the lowest was recorded for Mvundeni (4%). Green turtles comprised 79% of the mortality cases recorded with a mean size range of 68.9 ± 1.9 cm CCL. The incidences of mortality occurred year-round; however, the incidence of strandings was higher during the dry NEM season in the months of January to March when fishing effort is also highest. The success of sea turtle conservation efforts in the Lamu seascape is clearly demonstrated by the increased nesting activity over time, as well as the reduced trend on sea turtle nest predation levels. To continue this success, it is vital that sea turtle conservation efforts including a comprehensive monitoring programme are supported

Diversity of Shallow-Water Species in Prawn Trawling: A Case Study of Malindi–Ungwana Bay, Kenya

Bottom trawling is a common fishing method that targets bottom-dwelling fisheries resources. It is non-selective and large amounts of by-catch are discarded, raising serious sustainability and ecosystem conservation concerns. In this study, a shallow-water bottom-trawl fishery was evaluated using logbook catch data between 2011 and 2019 and the species composition data collected by fisheries observers between 2016 and 2019. The logbook data showed a twenty-fold increase in the annual catches with a ten-fold increase in fishing effort and an increase in the proportion of retained catch from 2011 to 2019. The observer data showed that for prawn, the by-catch ratio ranged from 1:3 to 1:9 during the four years. Multivariate analysis revealed significant differences between the compositions of retained and discarded catches mainly attributed to Pellona ditchela, Nematopalaemontenuipes, and Secutor insidiator. There was no significant decline in species diversity and the trophic level of the catches over the 4-year observer period indicating no marked impact of trawling on the stock at the current level of fishing effort. This study provides baseline information on the prawn trawl fishery against which the performance of the management regulations may be evaluated towards the Ecosystem Approach to Fisheries management

Diversity of Shallow-Water Species in Prawn Trawling: A Case Study of Malindi–Ungwana Bay, Kenya

Bottom trawling is a common fishing method that targets bottom-dwelling fisheries resources. It is non-selective and large amounts of by-catch are discarded, raising serious sustainability and ecosystem conservation concerns. In this study, a shallow-water bottom-trawl fishery was evaluated using logbook catch data between 2011 and 2019 and the species composition data collected by fisheries observers between 2016 and 2019. The logbook data showed a twenty-fold increase in the annual catches with a ten-fold increase in fishing effort and an increase in the proportion of retained catch from 2011 to 2019. The observer data showed that for prawn, the by-catch ratio ranged from 1:3 to 1:9 during the four years. Multivariate analysis revealed significant differences between the compositions of retained and discarded catches mainly attributed to Pellona ditchela, Nematopalaemontenuipes, and Secutor insidiator. There was no significant decline in species diversity and the trophic level of the catches over the 4-year observer period indicating no marked impact of trawling on the stock at the current level of fishing effort. This study provides baseline information on the prawn trawl fishery against which the performance of the management regulations may be evaluated towards the Ecosystem Approach to Fisheries management

Population structure enhances perspectives on regional management of the western Indian Ocean green turtle

To refine our understanding of the spatial structure of the green turtle (Chelonia mydas) populations in the South West Indian Ocean (SWIO), we analysed patterns of mitochondrial DNA (396 base pairs control region fragment) variation among 171 samples collected at five distinct locations (Kenya, Northern Mozambique, and three locations in the Republic of Seychelles: the Granitic, Amirantes, and Farquhar groups) and compared them to genetic data (n = 288), previously collected from 10 southern locations in the SWIO. We also analysed post-nesting satellite tracks (n = 4) from green turtles nesting in the Amirantes group. Pairwise comparisons of haplotype frequencies showed significant genetic differentiation amongst rookeries and suggest that the SWIO hosts two main genetic stocks of nesting green turtles that could themselves be divided in two sub-stocks that still need to be confirmed: A. the Southern Mozambique Channel, that could be composed of two sub-stocks (a1) Europa and (a2) Juan de Nova, and B. the Northern SWIO (N-SWIO) comprising two sub-stocks (b1) the Seychelles archipelago stock—SEY; and (b2) the remaining Northern SWIO rookeries. The newly revealed differentiation of the Seychelles population is supported by restricted migration of females tracked from the Amirantes group suggesting relatively limited links with other regional stocks. We hypothesize that this differentiation could be due to local and regional current patterns and to the role of the Indo-Pacific Barrier as a genetic break, enhanced during periods of sea level decrease associated with a rare but continuous flow of hatchlings and young juveniles from Western Australia