Back to Search Start Over

[Untitled]

Authors :
W. D. Emmerson
Sara Fratini
Yunus D. Mgaya
Renison K. Ruwa
Martin W. Skov
J.P. Shunula
Marco Vannini
Francesca Porri
Richard G. Hartnoll
S. Cannici
Adriano Macia
Source :
Wetlands Ecology and Management. 10:203-213
Publication Year :
2002
Publisher :
Springer Science and Business Media LLC, 2002.

Abstract

The aim of this work was to determine the abundance of crabs inmangrove communities along a latitudinal gradient along the eastern coastof Africa from 4°S to 32°S. Surveys were made atMombasa (Kenya), Zanzibar (Tanzania), Maputo (Mozambique) and in theTranskei (South Africa). Crabs were estimated at three designated levelsin the mangroves by visual census using a common protocol, and numberswere converted to biomass.Even after standardising the selection of sites and methods of censusthere was still extensive variability in the data, emphasising the complexheterogeneity of mangrove ecosystems. Lunar phase (full versus new moonsprings) did not have a consistent effect on results, but shore height hadseveral effects. Total crab biomass was similar in the two lower shore strataexamined, but about twice as high at the top-Avicennia level. Theratio of grapsid biomass:ocypodid biomass also changed with height: fromnear unity in the lower mangrove, to 0.14 in the middle strata, but to 15at the top.There was no consistent latitudinal trend in total crab numbers, but totalcrab biomass increased from north to south. In addition there was aconsistent and marked change in the grapsid biomass:ocypodid biomassratio: this swung from 0.65 at Mombasa to 6.8 in the Transkei. This hasimplications for the transfer of primary production through the food chain. Grapsids are important macrophagous feeders on the leaves and other partsof mangroves, whereas ocypodids are microphagous deposit feeders.

Details

ISSN :
09234861
Volume :
10
Database :
OpenAIRE
Journal :
Wetlands Ecology and Management
Accession number :
edsair.doi...........bc942d91c837b43466dd69fa387eda2a
Full Text :
https://doi.org/10.1023/a:1020123713133