Seasonal variations in abundance and sex ratio of the freshwater crayfish Procambarus clarkii from four freshwater localities, River Nile, Egypt

M., El-Sayed A. A.; A., Shaaban E.; A., El Feky F.A.; S., Abd El Gawad S.; H., Mohamoud N.

doi:10.21608/eajbsz.2018.13426

Seasonal variations in abundance and sex ratio of the freshwater crayfish Procambarus clarkii from four freshwater localities, River Nile, Egypt

Document Type : Original Article

Authors

¹ Faculty of Science (Boys), Al-Azhar University, Cairo, Egypt,

² National Institute of Oceanography and Fisheries, Al Kanater, Egypt

³ Faculty of Science (Girls), Al-Azhar University, Cairo, Egypt

⁴ National Institute of Oceanography and Fisheries, Al Kanater, Egypt,

⁵ Faculty of Science (Girls), Al-Azhar University, Cairo, Egypt.

10.21608/eajbsz.2018.13426

Abstract

A total of 693 specimens of the freshwater crayfish, Procambarus clarkii were collected from four sites chosen along the River Nile, at Helwan (Site #1), El Warraq (site #2), El Rahawy (Site #3) and El Rayah El Mounofy (Site#4) during the period from summer 2014 to the following spring 2015. Most individuals of the collected specimens were characterized by hard-rigid outer exoskeleton, with dark-red, or deep brownish color carapace. But some specimens had old green or grey color carapace with scars and epibiotes. The collected specimens showed spatial and temporal variations, recorded 242 specimens (34.92% of all) from El Rayah El Mounofy, declined gradually into 173 (24.96%), 163 (23.52% ) and 115 (16.59%) at El Warraq, El Rahawy and Helwan, respectively. Seasonally, the highest number of individuals was 266 (29.4%), collected in spring, of them 115 were obtained from El Warraq, but declined gradually into 193 (28.9%) in summer, and 183 (24.3%) in autumn and reached the minimum number (51 individuals, 17.3%) in winter. The present results also showed that, no specimens were collected from Helwan during winter, and only 3 individuals were obtained from El Warraq, compared with 17 and 31 specimens collected from El Rahawy and El Rayah El Mounofy, respectively. In contrast, during summer, only 11 specimens were collected from El Rayah El Mounofy. The fluctuations in number of collected individuals of this species were greatly correlated with increasing in water temperature and water level after winter enclosure. The general sex ratio was 1:0.47 males: females and showed significant statistical variations between sites and seasons, recorded 1:0.40, 1:49, 1:0.63 and 1:0.40, males to females at Helwan, El Warraq, El Rayah El Mounofy and El Rahaway, respectively. The present data showed that, the whole populations of this species were varied from 6.6 to 14.3 cm in total length, from 26.84 ±14.42 at Helwan to 34.48±22.5g at El Rahawy.

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