A dataset of distribution of the Geothelphusa (Decapoda: Potamidae) with their environmental parameters and stream indicators in eastern and southern Taiwan

Study Extent

The freshwater crabs appear in almost all clean freshwater bodies, from moist lowland forests to rugged mountains (Cumberlidge et al. 2009). There are 57 recognized Geothelphusa species, with 39 species in Taiwan (Shy et al. 2021). Over twenty Taiwanese Geothelphusa species live in stream ecosystems below 500 m above sea level (Shy and Lee 2009). In this paper, the 42 sampling sites in Taiwan (Fig. 1) are all natural habitats of streams with an elevation distribution of 2-998 m, and 33 sites (78.6%) are below 500 m altitude. The data of the 22 monitoring sites were collected quarterly from the summer of 2013 to the summer of 2015, but some surveys were abandoned due to a lack of water-related data for the drought. The other 20 sites were surveyed only once in the summer and fall of 2014.

Sampling

Crab investigation A complete search of 50 meters along the stream was conducted at each site. Then, six traps baited with dry pet food (Fig. 2) were set overnight (Chen et al. 2003) to collect the Geothelphusa crabs. After identifying species and measuring the traits of carapace breadth, carapace length, wet weight and sex, the captured crabs were released to their native habitats except for those with doubt in species identification needed for confirmation in the laboratory. Environmental parameters investigation The water temperature, pH value, dissolved oxygen and conductivity of the sampling sites were measured by a water quality meter (Horiba U-53) in situ. The water samples used to measure the values of BOD5, NH3-N, SS, FC and TP were preserved below 4 degree Celsius and analyzed in the laboratory within seven days from collection. In addition, the score table of cQHEI was also recorded in situ. The data of BOD5, NH3-N, SS, FC and TP were used to calculate two water quality indicators: River Pollution Index (Liou et al. 2004) and Water Quality Index 7 (Wen 2006). The data of the score table of cQHEI were used to calculate the other environmental indicator: the citizen Qualitative Habitat Evaluation Index (Hoosier Riverwatch 2019).

Method steps

1. The water sampling and the seven parameters required to calculate two water quality indicators, River Pollution Index and Water Quality Index, including pH value, dissolved oxygen (DO), biochemical oxygen demand (BOD5), ammonia nitrogen (NH3-N), suspended solids (SS), fecal coliform (FC) and total phosphorus (TP), were operated following the protocols published by Taiwan Environmental Protection Administration in 2013.

All the crabs were identified and recorded to species, but a few individuals labelled as "Uncertain" were too small to identify. There were 12 species and 1,006 crabs of the Geothelphusa recorded.

1. Geothelphusa albogilva
   common name: 黃灰澤蟹 rank: species
2. Geothelphusa bicolor
   common name: 雙色澤蟹 rank: species
3. Geothelphusa caesia
   common name: 藍灰澤蟹 rank: species
4. Geothelphusa cinerea
   common name: 灰甲澤蟹 rank: species
5. Geothelphusa ferruginea
   common name: 銹色澤蟹 rank: species
6. Geothelphusa ilan
   common name: 宜蘭澤蟹 rank: species
7. Geothelphusa lili
   common name: 力里澤蟹 rank: species
8. Geothelphusa olea
   common name: 黃綠澤蟹 rank: species
9. Geothelphusa pingtung
   common name: 屏東澤蟹 rank: species
10. Geothelphusa shernshan
    common name: 神山澤蟹 rank: species
11. Geothelphusa tawu
    common name: 大武澤蟹 rank: species
12. Geothelphusa tsayae
    common name: 蔡氏澤蟹 rank: species
13. Geothelphusa
    common name: 澤蟹 rank: genus

There were 42 study sites ranging from 120.601295 to 121.6641944 and 21.95916 to 24.75119444.