Abstract:
Abstract 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.