356
years between 1986 and 1998 (Table 1). The annual reproductive pattern was assessed by tracking gonad growth by measuring the monthly gonad index calculated as the monthly mean ratio of the wet weight of the gonad, relative to the wet weight of the individual for sea urchins (Gonor 1972) and of the wet weight of the body wall for sea cucumbers (Conand 1981). Macroscopic and microscopic observations were also made of the gonad to verify the sex and maturity stages.
Table 1. The locations, species, year of study and SST (mean annual) of the study sites on the Kenyan coast. The mean annual SST is calculated from NOAA data. Reef Lat Species Year SST Kanamai 3o 55' T. gratilla 87-88 26.9 Kanamai 3o 55' D. savignyi 92-93 26.9 Kanamai 3o 55' D. setosum 92-93 26.9 E. mathaei 92-94 26.9 Kanamai 3o 55' Ras Iwatine 4o 70' H. arenacava 97-98 27.1
3.03 ± 0.54% (sem). The gonad index then gradually increased to peak at 8.03 ± 0.21% between January and February at the peak of the northeast monsoons (Fig. 1). There was no significant difference between the overall average gonad index of females and male E. mathaei (Table 3.).
Table 2. The relationship between body size (weight for sea urchins and body wall weight for the sea cucumbers) and the gonad weight, and gonad index of individuals for the species sampled. For each comparison, the correlation coefficient r, and the sample size (in brackets) are provided. Species Size vs. gonad Size vs. gonad weight index T. gratilla 0.53 (163) * 0.08 ns D. savignyi 0.14 ns 0.60 (270)* D. setosum 0.56 (276)* 0.15 ns E. mathaei 0.41 (100) * 0.03 ns H. arenacava 0.51 (720)* 0.30 ns * = p < 0.0001; the sample sizes are the same for both comparisons
The relationship between individual size and gonad growth was determined by a correlation between the gonad index (%) and the weight (g) of individuals. The level of synchrony in reproduction between the sexes was determined by a correlation between the mean monthly gonad index of female and male individuals. Temperature and light measurements were obtained from NOAA climatic data for each location and averaged monthly from 1985 to 1994 and correlated against mean monthly gonad indices for each species. The northeast monsoons start in October and end in April, while the southeast monsoons occur from May to September on the Kenyan coast (McClanahan 1988). Lunar periodicity was measured in the sea urchins by inducing individuals to spawn using KCl every 2 to 4 days during the peak reproductive period. The gametogenic cycle was also tracked by calculating the mean gonad index every 2 – 4 days for several lunar cycles (new moon = lunar day 0) during the peak period of reproduction. Results There was a significant and positive relationship between individual gonad weight and body size for all species (p 50% full of sperm or ova (Pearse 1969).

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