Density influence factors of fiddler crab in mangrove estuary of Cigu River in southwestern Taiwan
Date Issued
2009
Date
2009
Author(s)
Chen, Yao-Hung
Abstract
The study mangrove area, which was located at southwestern Taiwan has abundant biological resources and is one of important habitat of wild bird. The fiddler crabs were the most dominant species of benthic animals. In previous study, visual survey was the most efficiency and suitable method to estimate fiddler crab’s density in the mangrove estuary of Cigu River. Fiddler crabs were also captured and measured their morphology. The data were sampled monthly from July, 2008 to June, 2009, the purpose of this study was to comprehend density influence factors of fiddler crab in mangrove estuary of Cigu River. The transect sampling was vertical to tidal line. Besides, species discrimination, individual counts and sex judgement were also investigated by visual survey. The environmental factors, such as pH, salinity, temperature, dissolved oxygen, water content, organic matter, grain size and the proportion of mud/sand were also investigated. The results indicated that there were four species, such as Uca arcuata, Uca lactea, Uca triangularis triangularis and Uca vocans borealis. Carapace width of Uca arcuata and Uca lactea lactea had highly relevant with weight, and carapace length of Uca vocans borealis had highly relevant with weight. The mangrove estuary of Cigu River could be divided into three sectors, such as Cigu River sector, small water channel sector, Sangu River which was composed of different water and sediment factors. PCA also indicated that the variation of the mangrove estuary of Cigu River was mainly from sediment factors then water factors. Sangu River sector was suitable habitat for Uca arcuata and Uca lactea lactea compared to other two sectors. There were high Uca arcuata and Uca lactea lactea densities in high tidal zone of Sangu River sector. Sangu River sector had sedimental factors as following：grain size 48.8 ± 5.68 μm；mud/sand proportion 1.7 ± 0.38％；organic matter 3.56 ± 0.93 ％；water content 35.5 ± 4.76 ％。
Subjects
fiddler crab
Uca
habitat
Cigu River
mangrove estuar
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