Ecological studies on the freshwater crayfish Procambarus clarkii in the River Nile, Egypt

Abstract

The red swamp crayfish, Procambarus clarkii (Girard, 1852) (Decapoda, Cambaridae), is a native species in the southern and central regions of the United States. It was introduced into the River Nile in the early 1980s and has become a resident in the Egyptian freshwater ecosystems, but up till now no detailed study has been done to know its stock or even its population dynamic in the River Nile. The population dynamical parameters of Procambarus clarkii were estimated based on 3465 specimens (1455 males and 2010 females) (7.0 – 15.0cm TL), collected from two locations along the River Nile; from 2009 to 2012. Length frequency analysis was used for age determination of the animal from river Nile by applying the Bhattacharya method and ELEFAN I software. The population ranged between 7 and 13.8 cm TL (3.5 – 7.4 cm CL) for males from 7 to15 cm TL (3.5 – 8 cm CL) for females. By applying the Modal Progression Analysis (MPA) and ELEFAN I, it is obvious that, the longevity extends one year for males and one and half years for females. It is also observed that, the most dominant age group for males was the second age group representing 68% of the total SUMMARY 102 male specimens. In addition, the most dominant age group for female specimens was the second age group representing 54.6% of the total female specimens. The basic age-length data obtained by means of MPA and ELEFAN I were used for studying the growth pattern and show that this species attains its highest growth rate during the first six months of life.