OCCURRENCE AND VARIATION IN THE DEPTH OF BURROWS OF MANGROVE CRABS AROUND A TROPICAL CREEK IN NIGERIA

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Keywords: Cardisoma armatum, Goniopsis pelii, Mangrove wetland, Burrow, Depth and width, Occurrence, Distribution

Abstract

Mangrove crabs are active burrowers in intertidal sediments of wetland, living beneath
drifts and high-tide marks in lagoon shores in many parts of the world. The occurrence,
distribution and burrow depths and diameters of the mangrove crabs, Cardisoma
armatum and Goniopsis pelii collected from a mangrove wetland of the Lagos Lagoon
were investigated between February and July, 2017. Burrows were counted biweekly on
permanent square plots marked out in the six stations, while the appearance of new
burrows as well as disappearance of old burrows, depths and diameters were recorded.
C. armatum was present in all the study sites with a total of 848 specimens and occurred
throughout the study period, while G. pelli with a total of 115 specimens occurred in two
study sites and during the wet season only. Species ratio was 1: 0.37 while the Chi-
squared value at 1 d.f and 5 % significant level was 557.93. The depth of the crab
burrows across the stations ranged from 16.65 – 33.47 cm with diameter ranging
between 4.0 – 6.40 cm. Crab burrows, its occurrence and distribution were observed to
be affected by natural and anthropogenic factors. There was a rapid decline in burrows in
the month of April when rainfall seized and anthropogenic factors like noise, refuse
dumping and construction works also played major roles in determining the dispersion of
burrows. Therefore, mangrove crabs and their burrows are greatly influenced by both
abiotic and biotic factors.

Published
2019-01-08