A comparison of alternative methods for estimating population density of the fiddler crab Uca annulipes at Saco Mangrove, Inhaca Island (Mozambique)

A comparison of alternative methods for estimating population density of the fiddler crab Uca annulipes at Saco Mangrove, Inhaca Island (Mozambique)

Visual counts of surface-active crabs both by binocular and burrow counting methods have been used in many studies to estimate population density. However, their reliability has not yet been assessed comparatively. Three methods for estimating the abundance of fiddler crabs Uca annulipes in a mangro...

Full description

Saved in:
Bibliographic Details
Published in:Hydrobiologia Vol. 449; no. 1-3; pp. 213 - 219
Main Authors: MACIA, Adriano, QUINCARDETE, Ivaldo, PAULA, José
Format: Conference Proceeding Journal Article
Language:English
Published: Dordrecht Springer 01-04-2001
Springer Nature B.V
Subjects:
Animal populations
Animal, plant and microbial ecology
Biological and medical sciences
Correlation coefficient
Crustaceans
Excavation
Fundamental and applied biological sciences. Psychology
General aspects. Techniques
Marine
Methods
Methods and techniques (sampling, tagging, trapping, modelling...)
Moon
Neap tides
Population density
Sex ratio
Spring tides
Uca annulipes
Mozambique
Africa
ISW, Mozambique, Maputo, Inhaca I., Saco
Lunar cycle
Brackish water environment
Burrower
Estimation
Brachyura
Environmental factor
Tidal rhythm
Method
Crustacea
Sex ratio
Mangrove
Arthropoda
Decapoda
Invertebrata
Population density
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Visual counts of surface-active crabs both by binocular and burrow counting methods have been used in many studies to estimate population density. However, their reliability has not yet been assessed comparatively. Three methods for estimating the abundance of fiddler crabs Uca annulipes in a mangrove forest (Inhaca Island, Mozambique) were compared from three different sub-areas: two sub-areas inundated only during spring tides and one sub-area inundated in both spring and neap tides. Burrow, binocular and direct (excavation) counting methods were performed by plotting ten 0.25 m super(2) quadrats in each sub-area over the four moon phases. Overall densities (per 0.25 m super(2)) differed according to method, sub-area and lunar phase. Burrow count overestimated crab density by up to 20%, while binocular count underestimated density by up to 41%. Correlation coefficient estimated for both counting methods showed that burrow count gives better density estimates than binocular count (0.91 and 0.56, respectively). Sex ratios were also investigated within the three sub-areas and at the moon phases. Males are dominant throughout the studied period except during new moon and first quarter, indicating that when the number of gravid females is low, sex ratio bias for binocular count is minimal.
Bibliography:ObjectType-Article-1
SourceType-Scholarly Journals-1
ObjectType-Feature-2
content type line 23
ObjectType-Article-2
ObjectType-Feature-1
ISSN:0018-8158
1573-5117
DOI:10.1023/A:1017502817087