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Variability of larval assemblages within marine habitats has an effect on population structure of adults, and on patchiness of populations in space and time. However, despite this effect, few studies have examined this variability in the Western Indian Ocean (WIO) especially in relation to marine park boundaries. In this study, we tested the hypothesis that seasonality and biophysical variables influence fish larval assemblage structure within two of the oldest marine parks in Kenya of differing reef structure. Monthly samples were obtained from the parks using oblique plankton tows for 14-24 months. A total of 38 families and 52 genera of fish larvae were obtained from Malindi Marine Park, while 20 genera in 20 families were sampled from the more enclosed Watamu Marine Park but with a connection to an estuarine system. The preflexion larvae comprised over 80% of the total larvae in the parks with the dominant groups being; Gobiidae, Blenniidae, Engraulidae and Apogonidae. The availability of a wide size range of larvae for some groups like Blenniidae, Gobiidae, Engraulidae, Labridae and Scaridae indicated the possibility of some larvae completing their pelagic phase within the parks. Larval densities differed significantly between seasons and stations in both parks, with higher densities ranging between 95-311 larvae/100 m 3 during the calm northeast monsoon (NEM) season, compared to 5-58 larvae/ 100 m 3 during the stormy southeast monsoon (SEM) season. Stepwise multiple regression analysis indicated a significant positive influence of zooplankton density on fish larval abundance in Malindi Park, while a positive and significant influence of temperature was found in Watamu Park. Distinct assemblages of larvae occurred within the parks indicating within park patchiness in larval distribution and, perhaps existence of retention features. These results provide useful baseline data on larval distribution in the WIO, and will be useful in understanding population dynamics of adult populations when complimented with additional oceanographic data.

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Samples were collected monthly at four fixed stations in Mida creek from May 1996 to April 1997, in order to determine the species composition, abundance and diversity of phytoplankton and zooplankton collected with 20-and 332-µm mesh size plankton nets respectively. Sampling also included measurement of salinity and temperature. Peaks in phytoplankton abundance occurred in May and January, following the long rains in April-May and the short rains in November-December. Zooplankton densities followed the phytoplankton peaks with the main peak occurring in February after the major phytoplankton bloom. Similarly, smaller peaks occurred in May and March. Copepods dominated the zooplankton forming up to 60% of total species composition. High zooplankton diversity occurred in June-July when zooplankton abundance was lowest as compared to February-March. Spatially, the highest diversity was recorded at station 1 located towards the open sea as compared to the other stations located farther inshore.

ABSTRACT1. Larval supply to reef sites influences adult population structure, reef connectivity and conservation potential of marine reserves, but few studies have examined this topic in the Western Indian Ocean (WIO).2. Fish larval supply to Malindi Marine Park in Kenya was studied using light-traps for a period extending from March 2005 to June 2006. The traps caught pre-settlement fish larvae at two sites spread across the park. Catch rates (number trap À1 night À1) were used to represent larval abundance and to test the influence of seasonality and habitat characteristics on larval abundance in the park.3. Thirty-three species of reef fish larvae in 15 families were sampled. Larval supply to the park was more diverse during the north-east monsoon season (30 species) than in the south-east monsoon season (15 species 4. Family-specific temporal variation in larval abundance showed dominance of the families Apogonidae and Caesionidae in the park, with higher abundance during the north-east monsoon months. A few families (e.g. Canthigasteridae) showed dominance during the south-east monsoon season. Regression and rank Spearman correlation analyses indicated positive correlation of chlorophyll-a with larval supply while water depth had significant negative correlation with abundance of the Apogonidae and Caesionidae.5. On a short-term temporal scale larval abundance in the park was highly correlated with the new moon lunar phase more than the full moon. However, on a long-term scale (16 months) larval supply to the park was significant only over a 2-month period and was correlated with environmental productivity more than ambient temperature. These results are useful in understanding the role of larval supply in structuring adult fish populations and the factors that force larval flux at reef sites.