Abstract Full Text:PDF Recommended articles Mail to Author How to Cite

¹ Lahore College for Women University, Department of Zoology, Faculty of Natural Sciences, Lahore, Pakistan DOI : 10.4194/1303-2712-v18_1_25 Viewed : 8221 - Downloaded : 4056 High stocking density is a major problem in extensive aquaculture in Pakistan. Present study investigated its effect of growth, levels of thyroxine (T4) and cortisol in two major carps of Pakistan; labeo (Labeo rohita) and catla (Catla catla). One cohort of labeo (n=30) was kept at high stocking density (HD) (25 g/L). HD cohort was split into two replicates, each containing a total of 15 fish. Second cohort of labeo (n= 10) was reared at low stocking density (LD) of 4.4 g/L. LD cohort was divided into two replicates, each containing a total of five fish. Similar protocol was followed for catla. Trial continued for the period of 30 days. At the end of trial, condition factor significantly decreased in HD cohorts of both species. Levels of cortisol in HD cohorts (210 ± 2.00 nmol/L in Catla catla; 425 ± 3.00 nmol/L in Labeo rohita) were significantly higher than those in LD cohorts of both species. Values of T4 in HD cohorts were found to be 1.48 ± 0.20 pmol/L in Catla catla and 1.74 ± 0.10 pmol/L in Labeo rohita at the end of trial which were significantly lower than at the commencement of trial. Suppression of growth, elevation in the levels of cortisol and decrease in profile of T4 in HD cohorts of both species was due to stress induced by high stocking density. Furthermore, present study found that optimum stocking density for extensive farming of both species should be approximately 4.4 g/L. Keywords : Labeo rohita; Catla catla; stocking density; condition factor; T4; cortisol