The marine fishery in Kenya is predominantly small-scale and artisanal with about 11,000 fishers intensely fishing near shore coastal reefs using minimally selective fishing gears. A large majority (88%) of fishers use outdated equipment such as basket traps, beach seines, hand lines (hook and lines), fence traps, gillnets, spearguns and cast nets. Handmade canoes propelled by paddles (kasia) or sail power are used to access offshore waters, while only a few fishers have motorized boats. Although fishers along this coast know and express the potential of offshore fishing, most of them are disempowered and unable to access any of the largely untapped offshore pelagic resources. Using a unique dataset from four distinct coastal areas: Funzi-Shirazi bay area, Diani-Chale area, Mombasa-Kilifi north coast area and the Malindi-Ungwana bay area, containing species level length frequency catch data from the multi-gear and multi-species fishery, abundance of specific species, gear use comparisons in various regions, catch per unit effort and total catch estimate over a nine year period (2001 – 2009) were evaluated. Despite high diversity in the fishery, five species (Lethrinus lentjan, Siganus sutor, Leptoscarus vaigiensis, Lethrinus harak and Parupeneus macronemus) represented over 75% of the catch. A total of 11 legitimate gears were observed in this coastal artisanal fishery with basket traps (42%) being the most popular. Fishers along the Mombasa-Kilifi area predominatly used beach seines while those in Diani-Chale, Malindi-Ungwana bay and Funzi-shirazi bay predominaltly used spearguns, gillnets and basket traps, respectively. Apart from gillnets, a general declining trend for most of the gear types was observed since 2004. Beach seines recorded the lowest (20.9±0.2 cm) mean length while gillnets recorded the highest (34.2±0.3 cm). The highest catch (~26,000 metric tons) came in 2001 and the lowest (~15,000 metric tons) in 2005. The highest number of fishers was observed in 2008 while 2009 recorded the highest (4.8±2.3) mean number of hours per outing. The mean annual CPUE per region ranged from (1.5 kg.fisher-1.hr-1) in Diani-Chale to (1.0 kg.fisher-1.hr-1) in Malindi-Ungwana bay. Making use of questionnaire data, the attitudes towards offshore fishing strategies, FADs in particular, were evaluated. Some communities (about 25% in every location) were not even aware of FAD fisheries. With the imminent introduction of a FAD fishery in Kenya, it was concluded that, for this fishery to realize its full potential, training on FAD fishing techniques has to be done. Finally, effective management is necessary if small-scale fisheries are to continue providing food security for many poor coastal communities. Gear-based management in Kenya, although under represented and under studied, has the potential to be adaptive, address multiple objectives, and be crafted to the socio-economic setting. Management effectiveness in near shore fisheries has generally been evaluated at the scale of the fish community. However, community level indicators can mask species-specific declines that provide significant portions of the fisheries yields and income. This thesis seeks to identify ways in which the Kenyan artisanal fishery can be sustained and managed from within coastal communities, giving them the resources and education to effectively improve their lives. The introduction of a offshore FAD fishery and hence access to offshore pelagic species provides an opportunity to not only alleviate pressure on coastal resources but also to empower coastal communities and contribute to the growth of Kenya’s national economy as a whole.

The silky shark Carcharhinus falciformis forms the primary elasmobranch bycatch in tuna purse seine fisheries using fish aggregating devices (FADs) in all of the world’s tropical oceans. Its life-history traits of slow growth, late maturation and low fecundity make it vulnerable to over exploitation, as is apparent from historical bycatch trends. Very little is known about the associative behaviour of this species with floating objects, information which is essential in formulating effective mitigation and management measures. This study aims to address this knowledge gap through the use of various electronic tagging techniques in conjunction with dietary analysis. Dietary data were collected from 323 silky sharks incidentally caught at FADs. Approximately 40 percent of the diet consisted of prey associated with FADs while the remaining 60 percent were non-associated species of crustaceans, cephalopods and fishes. These results suggest that the associative behaviour is not primarily driven by trophic enhancement, but is likely a combination of predator avoidance, social interactions and feeding. Fine-scale behavioural data from silky sharks associated with drifting FADs were collected through the use of acoustic telemetry techniques. Acoustic tags were implanted into 38 silky sharks (69- 116 cm TL) at eight FADs. FADs were equipped with satellite linked acoustic receivers and abandoned to drift freely. Presence/absence and swimming depth data were telemetered via the Iridium satellite system. A total of 300 d of behavioural data were collected from 20 tagged individuals. Individuals remain associated with the same FAD for extended periods (min = 2.84 d, max = 30.60 d, mean = 15.69 d). Strong diel patterns were observed in both association and swimming depth. Typically individuals moved away from FADs after sunset and return later during the night, then remain closely associated until the following evening. Vertical behaviour also changed around sunset with sharks using fairly constant depths, within the upper 25 m, during the day and switching to rapid vertical movements during the night, with dives in excess of 250 m recoded. Broader scale movement behaviour was investigated using pop-up archival satellite tags (PSATs). Tags were deployed on 46 silky sharks (86-224.5 cm TL) for a total of 1495 d. Light data were used to calculate geolocation estimates and reconstruct the sharks’ trajectories. Movement patterns differed between animals and according to deployment duration. Several extensive horizontal movements were observed, with an average track length of 3240 km during an average tag deployment of 44.02 d. Horizontal movement patterns were found to correlate very closely with drift patterns of FADs. Consequently, it appears that the movement behaviour of juvenile silky sharks is strongly influenced by the movement of drifting FADs in this region. Ghost fishing of silky sharks through entanglement in FADs was also investigated using data derived from PSATs as well as underwater visual censuses. Thirteen per cent of the tagged sharks became entangled in FADs and entangled sharks were observed in 35 percent of the 51 FADs surveyed. Using this information in conjunction with estimated time that sharks remained entangled in the FAD (from depth data from PSATs), and scaling up according to estimates of FAD numbers, it was found that between 480 000 and 960 000 silky sharks are killed annually in this manner in the Indian Ocean. Subsequent management measures in this region prevent the deployment of FADs with netting that could lead to entanglement. Overall, floating objects appear to play a significant role in the juvenile life stages of silky sharks in this region. While their association with floating objects is clearly advantageous in an evolutionary sense, under current tuna fishery trends, this behaviour is certainly detrimental for the population.