Influence of photoperiod and rearing density of fry in production of stunted fingerlings of Catla catla (Hamilton)

Seed stunting is a process of suppressing the normal growth of fish by manipulating various factors affecting the growth process. The present study aimed at evaluating the influence of varied photoperiod and stocking density on the growth and survival of catla (Catla catla) during the stunting process.

Five treatments including control were used in triplicate and stocked with catla fry (0.84 g, 38.8 mm). Control, T-1 and T-2 groups were stocked with fry at 20 m³ densities and maintained at 12 hours light and 12 hours darkness (12L12D), 6L18D and 0L24D, respectively to study the influence of varied photoperiod. T-3 and T-4 were stocked with fry at 30 and 40 m³ densities respectively to study the effect of crowding on the growth. Control at 20 m³ density and 12L12D photoperiod served as control for both the studies.

There was a significant reduction in the survival, harvested body weight, total length and specific growth rate in the treatments T-1 and T-2 as compared to the control (P<0.05). Though these attributes were statistically similar (P>0.05) between T-1 and T-2, the values were relatively higher in T-1 suggesting considerable photoperiod effect on fish growth. Similarly, the HBW, total length and SGR significantly reduced from T-3 to T-4 with increased density depicting effect of crowding on growth. Such results indicated that both increased stocking density and decreased photoperiod lead to growth suppression and can be used as tools for seed stunting in catla.