Biometric relationships of the invasive crayfish Procambarus clarkii to the Egyptian freshwater drainage canals

El-Sayed M,Al-Damhougy A,Amer, A,Zaakouk A

doi:10.21608/eajbsz.2015.13478

Abstract

The specimens of the freshwater crayfish, Procambarus clarkii were collected from the River Nile tributaries at Al-Kanater Al- Khairiya, Qalyoubia governorate during the period from April 2010 to October 2011. The individuals of this species are small lobster-like freshwater crustacean. They have hard- rigid outer exoskeleton, and dark- red, or deep brownish color carapace, characterized by prominent whitish granules during the intermolt stages. The mature individuals of this species are varied from 6 to 10.5 cm in standard length, and from 6.5 to 11.5 cm in total length, and ranged between 10.38 and 56.34 gm in total body weight. The biometric study indicated that the relationship between body weight and standard length for the whole population (males and females) of this species is curvilinear, with positive regression coefficient b (slope) equals to 2.998, indicates to an isometric growth and correlation coefficient r 0.994, denotes to stability of this species at the prevailing environmental factors. For sex separate, the value of b showed also positive isometric regression coefficients, up to 3.359 and 3.118 for males and females respectively, indicating to slightly heavier males than females, without significance difference between sexes (T-test = 1.36, P > 0.05). These results also showed that, the values of regression coefficients b for the whole population during different seasons indicated heavier males and females during spring (3.719) and winter (3.879) than those in summer (3.091) and autumn (3.331). The values of relative condition factor Kn or the wellbeing for this species were varied from 0.89 to 1.11, with an average of 1.01, showing an ideal growth for the whole population with relatively high values in small and medium size-classes less than 9.0 cm in standard length. The relative growth rate of male's right chelae was varied from 2.63 to 6.3 cm, showing highly positive regression with an increase in standard length, sharply declined to vary between 1.93 and 3.93 cm in females, denotes to relatively weak correlation in females.

Highlights

The red swap crayfish, Procambarus clarkii (Girard, 1852) had been introduced into the Egyptian freshwater systems, the River Nile and its drainage canals, during the early 1980's via a private fish farm (Ibrahim et al, 1995; Ibrahim and Khalil, 2009).El-Sayed, A
M. et al This species belongs to family Cambaridae and is a very common native species lives in many freshwater bodies of the south-central U.S.A., Louisiana (Huner, 1995). It extended to other countries including Europe, Australia and China (Huner et al, 1993), and represents at the present times the most common wide spread species from over 400 species of freshwater crayfishes belonging to the families Astacidae, Cambaridae and Parastacidae around the world (Huner & Lindqvist, 1995)
A total of 166 specimens of Procambarus clarkii were collected from River Nile tributaries at Al-Kanater Al- Khairiya, Qalyoubia Governorate during the period from April 20110 to October 2011

Summary

Introduction

This species belongs to family Cambaridae and is a very common native species lives in many freshwater bodies of the south-central U.S.A., Louisiana (Huner, 1995). It extended to other countries including Europe, Australia and China (Huner et al, 1993), and represents at the present times the most common wide spread species from over 400 species of freshwater crayfishes belonging to the families Astacidae, Cambaridae and Parastacidae around the world (Huner & Lindqvist, 1995)

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