Population dynamics of an invasive species Carassius auratus in the Shatt Al-Arab River, Iraq

The population dynamics of the crucian carp, Carassius auratus in the Shatt Al-Arab River, Iraq was studied from November 2015 to October 2016 with monthly samples collected by different fishing gears. The FAO-ICLARM Stock Assessment Tool (FiSAT II) software was used for the mathematical analysis. Length-weight relationship was calculated as W= 0.0149L3.065 for fish length 4.6 to 26.8 cm. Growth parameters L∞, K and Ø were computed as 29.1 cm, 0.51 and 2.635. The total (Z), natural (M) and fishing (F) mortalities were 2.69, 1.09 and 1.60, respectively. Exploitation rate (E) was 0.59. Length at first capture (Lc) was found to be 10.04 cm. C. auratus displayed one main pulse of annual recruitment. The relative yield per recruit analysis revealed that the exploitation rate (E) of C. auratus was higher than the biological target reference points E0.1 and equivalent to Emax. It could be concluded that the C. auratus stock in the Shatt Al-Arab River is operating nearby the exploited situation and needs some precautionary measures to avoid the overexploitation by activating the national law of fishing, exploiting and protecting aquatic resources, in particular preventing illegal fishing methods and follow up the execution of the closed season to prevent the decline of our fish resources.