Density, Distribution and Population Biology of Macrophthalmus (Venitus) dentipes Lucas, 1836, From Mangrove Areas of Pakistan
Macrophthalmus (Venitus) dentipes is a common inhabitant of mangrove areas along the Pakistan coast. Crabs from two mangrove sites, Korangi creek and Sandspit were sampled every month during Mar 2001 to Feb 2002 to study their populations. The average density of crabs ranged between 1 to 24 m -2 . For the density distribution, the nested design ANOVA showed no significant difference between stations, but significant difference within seasons and different tidal height (low tide level) at Sandspit and significant difference among tidal level at Korangi creek were observed. Significantly more small sized crabs were observed at the lower intertidal region. The present study demonstrates the importance of substratum characteristics in influencing the distribution and abundance of these sentinal crabs. `t' test showed carapace width (CW) of male and female crabs were significantly different at Sandspit and Korangi creek. The recruitment of juvenile crabs (CW < 5 mm) was observed throughout the year and the presence of ovigerous females from October to May indicated seasonal reproduction. The average size of ovigerous females was CW= 10.4 mm and the smallest ovigerous female was CW =7.0 mm.