Comparison of length-weight relationship and condition factor of redbelly tilapia Coptodon zillii (Gervais, 1848)‎ from three different locations in Basra, Southern Iraq

الملخص EN

Current study was conducted in three locations, the first was floating fish cages, the second was fish earthen pond and the third was Shatt Al-Arab River north Basra Governorate at Hartha District.

A total number of 266 fresh redbelly tilapia (Coptodon zillii) fishes were collected from the locations using different nets i.e.

hand net in the first location and cast net in the second and third locations.

The fishes transported to the laboratory of Aquaculture Unit in boxes with crushed ice.

Samples were taken from 1/4/2017 to 1/10/2017.

Water temperature during sampling period ranged between 17 to 31 °C and salinity between 1.1 to 3.2 ppt.

The number of examined fish was 97, 92 and 77 from cages, pond and wild fish respectively.

The mean fish total length varied between (16.60, 14.19 and 12.78) cm and weight varied between (109.42, 60.05 and 49.12) g for cages, pond and wild fish respectively.

No fish recorded less than 5 cm or more than 25 cm.

The values of the exponent 'b' in the length–weight relationship varied between 3.1655, 2.9596 and 2.9978 for cages, pond and wild fish respectively.

In this study, C.

zillii showed to undergo positive allometric growth (b> 3) in cages but the pond and wild fish exhibited negative allometric pattern of growth (b< 3).

Modified condition factor values ranged between 1.34 to 2.04 for cage and wild fish respectively, relative condition factor values were 1.00, 1.00 and 1.01 for cage, wild and pond fish respectively, while Fulton’s condition factor values ranged between 1.76 to 2.13 for pond and cage fish respectively.

The statistical analysis showed that there were significant differences (P<0.01) in "K" values between the three locations considering modified and Fulton’s condition factors, while no such significant differences (P>0.01) found in relative condition factor.