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).

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.

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

Author Correction: Global status and conservation potential of reef sharks

An Amendment to this paper has been published and can be accessed via a link at the top of the paper.</p

Widespread diversity deficits of coral reef sharks and rays

A global survey of coral reefs reveals that overfishing is driving resident shark species toward extinction, causing diversity deficits in reef elasmobranch (shark and ray) assemblages. Our species-level analysis revealed global declines of 60 to 73% for five common resident reef shark species and that individual shark species were not detected at 34 to 47% of surveyed reefs. As reefs become more shark-depleted, rays begin to dominate assemblages. Shark-dominated assemblages persist in wealthy nations with strong governance and in highly protected areas, whereas poverty, weak governance, and a lack of shark management are associated with depauperate assemblages mainly composed of rays. Without action to address these diversity deficits, loss of ecological function and ecosystem services will increasingly affect human communities

Global status and conservation potential of reef sharks

Decades of overexploitation have devastated shark populations, leaving considerable doubt as to their ecological status1,2. Yet much of what is known about sharks has been inferred from catch records in industrial fisheries, whereas far less information is available about sharks that live in coastal habitats3. Here we address this knowledge gap using data from more than 15,000 standardized baited remote underwater video stations that were deployed on 371 reefs in 58 nations to estimate the conservation status of reef sharks globally. Our results reveal the profound impact that fishing has had on reef shark populations: we observed no sharks on almost 20% of the surveyed reefs. Reef sharks were almost completely absent from reefs in several nations, and shark depletion was strongly related to socio-economic conditions such as the size and proximity of the nearest market, poor governance and the density of the human population. However, opportunities for the conservation of reef sharks remain: shark sanctuaries, closed areas, catch limits and an absence of gillnets and longlines were associated with a substantially higher relative abundance of reef sharks. These results reveal several policy pathways for the restoration and management of reef shark populations, from direct top-down management of fishing to indirect improvement of governance conditions. Reef shark populations will only have a high chance of recovery by engaging key socio-economic aspects of tropical fisheries