Abundance and distribution of mangrove crabs in relation to environmental parameters such as soil salinity , soil pH soil organic carbon content, soil sulphur comtent and soil nitrogen content has been described by previous workers. Both gualitative and gualitative methods have been used to estimate the abundance of crabs in mangrove ecosystems and the dependence of mangrove crabs on the environmental condition has been described. Salinity ,water content in the soil ,ph ,total percentage values for carbon, nitrogen and sulpphur content of the soil and soil particle are some of the factors which have shown correlations with the distribution and abundance of crab. Macintosh1984 found that the low shore crab, Metaplax elegans could not tolerate salinities below 10%, whereas Persesarma onychophorum, inhabiting higher shore zones, colud tolerate several days at 5%. In the present study, the soil salinity varied between 60% to 80% and E. vesicolor and S. guttatum preferred low salinity range (57-67%) while the unidentified juvenile crab and M. thukuhar preferred higher salinity (80-82%).
Soil and water pH values also show correlation with the crab community structure. Low- pH conditions can be detrimental to crabs because they depend on calcium carbonate formation for exoskeleton and shell building. Low-pH values can cause exterior exoskeleton and shell erosion in crustraceans and hence they tend to avoid such places . Soil pH values in the upper zone of Kadolkele mangrove varied from 4.1 to 4.4 while it ranged between 5 and 6 in the lower zone. M. thukuhar and the juveniles of unidentified of all crab species were found to be high in the lower area where soil pH value is higher soil pH levels. This is in agreement whith the fidings of Plaziat. S. guttatum and S. smithii have shown positive correlation with soil pH in the Kadolkele mangrove.