Impact of Human Disturbance on Fiddler Crab (<i>Uca tangeri</i>) Burrow Morphology, Distribution and Chemistry at Eagle Island, Niger Delta, Nigeria

Abstract

Fiddler crabs are described as ecosystem engineers because of their burrow constructing ability. It was hypothesized that human activity will impact crab burrows. The study area was delineated into lowly, medium and highly impacted plots. Crab holes were randomly counted and their width, length and surface area estimated. Burrow soils were collected and analyzed for Cadmium (Cd), Lead (Pb) and Zinc (Zn) using spectrophotometric method (HACH DR 890 colorimeter). The result indicates that burrow width was significantly different between impacted plots (P < 0.05). Lowly impacted plot had the largest width while highly impacted plot had the smallest width. In contrast, there was no significant difference in burrow length (P > 0.05), but highly impacted plot has the longest length while lowly impacted plot has the shortest length. Again, the surface area of crab burrow varies significantly (P < 0.05), and lowly impacted plot had the largest area (507.95 ± 61.84 cm 2 ) followed by medium (390.30 ± 57.65 cm 2 ) and high (265.16 ± 30.85 cm 2 ) impacted plots. Similarly, lowly impacted area has more number of burrows (n = 55) followed by medium (n = 30) and highly (n = 23) impacted plots. Highly impacted plot had the highest Cd and Pb concentration whereas lowly impacted plot had the highest Zn concentration. This implies that burrow morphology and chemistry exemplify the level of anthropogenic impact.

Impact of Mangrove Deforestation on Fiddler Crab Distribution and Soil Physico-chemistry at Eagle Island, Rivers State

“…There are a combination of mangrove and nonmangrove species growing in the area. The major species of mangrove found in the area are: red (Rhizophora racemosa), black (avicennia germians) and white (laguncularia racemosa) while the non-mangrove species are mostly grasses like m. longibracteatus [19]. Some Nypa…”

“…Their activities in outlining and constructing interconnections of burrows within the soil is an exhibition of their architectural prowess. Fiddler crabs (Uca tangeri) have been known to function as bio-monitoring agents in measuring the extent of human disturbance in mangrove environment [19] because their burrow constructing behaviours are highly impacted by human influences and disturbance. Burrow building activities of fiddlers and other crab population are quite vital to the survival of the mangrove ecosystem.…”

Human disturbance affects behavioural time allocation in a fiddler crab (<em>Austruca annulipes</em>) in Southern Thailand

“…Other crustacean species, such as sandhoppers (Atlantorchestoidea brasiliensis) and mole crabs (Excirolana braziliensis), are also sensitive to human disturbances, and their densities are negatively correlated with human impacts (Cardoso et al 2016;Suciu et al 2018). Fiddler crab (Afruca tangeri) density and body size have a negative relationship with human disturbances (Oliveira et al 2000;Numbere 2020).…”