Nursing duration and pond fertilization level affect polycultures of Indian major carp (rohu Labeo rohita and mrigal Cirrhina mrigala ) with monosex Nile tilapia Oreochromis niloticus

Abstract

This study investigated the effects of nursing duration on the subsequent performance of rohu (R) Labeo rohita and mrigal (M) Cirrhina mrigala in polyculture with monosex male Nile tilapia (T) Oreochromis niloticus at four levels of pond fertilization. Nile tilapia, rohu and mrigal were stocked at a ratio of 4:1:1 in a 90‐day trial based on 40 20‐m2 pens fixed in four 400‐m2 earthen ponds. Growth of carp fingerlings during prolonged nursing (5 or 12 months) was stunted compared with fish nursed over a conventional duration of 3 months (3) but showed superior growth subsequently. Mean daily weight gain of stunted rohu (12) ranged from 2.2 to 2.8 g per fish day−1 compared with 1.1–1.6 g per fish day−1 for younger fish (3). The comparable ranges for mrigal were 1.9–2.8 and 1.4–2.1 g per fish day−1. Growth of Nile tilapia was inversely related to duration of carp nursing at the four levels of fertilization. Nile tilapia showed more response to increasing levels of fertilizer input (Y=−1.421+1.716X, where Y is the daily weight gain of Nile tilapia and X is the fertilizer level, r2=0.98, P<0.01, n=12). At a high level of fertilization (3.0 kg N:1.5 kg P ha−1 day−1), performance of stunted fingerlings (5 and 12) of both rohu and mrigal was similar (range 2.3–2.8 g per fish day−1, P>0.05), but younger mrigal (M3) grew faster than rohu (2.1 g per fish day−1 and 1.6 g per fish day−1 respectively). Older rohu (12) appeared to perform particularly well, and Nile tilapia poorly at the lowest level of fertilization (1.5 N:0.75 kg P ha−1 day−1), suggesting the impact of age of seed on competition within polycultures. The net fish yield (NFY) of tilapia was not affected significantly (P>0.05) by differential stocking age of carps; therefore, combined NFY of the three experimental fish species was not affected by the age of carp, as tilapia was the dominant species in polyculture. The highest combined NFY of all species in the most intensively fertilized pond (3.0 N:1.5 P kg ha−1 day−1) was calculated at 4.06±0.08 g·m−2 day−1, which was significantly higher (P<0.001) than the yield (1.82±0.12 g·m−2 day−1) from the pond with the lowest fertilization. At the highest fertilizer level, tilapia, rohu and mrigal contributed 72%, 14% and 14%, respectively, to the NFY, whereas the ratio was 60%, 20% and 20% at the lowest fertilization level. The study indicated that yields from tilapia in polyculture with the two carp species in more eutrophic water can be optimized if advanced nursing of carps is practised. Moreover, higher inputs of inorganic fertilizer and advanced nursing of carp are economically attractive under Bangladeshi conditions. Advanced nursing of rohu also improves its performance in more extensive systems when tilapia densities are high.

Influence of juvenile stunting on grow-out performance of rohu, Labeo rohita (Hamilton, 1822)

“…Further, weight gains after 12 months surpassed the latter significantly, demonstrating overcompensation of growth. Hossain et al (2003) reported higher growth of 5-and 12-month stunted juveniles of rohu and mrigal Cirrhinus mrigala (Ham.) compared to younger ones in polyculture with Nile tilapia, which confirmed the existence of CG.…”

“…Such results indicate a minimal influence of stunting duration on subsequent growth in these treatments. Chakrabarti, Sarkar, and Ghosh () (in Hossain et al., ) reported retarded growth in 6‐month overwintered mrigal during a subsequent grow‐out phase, whereas overwintered rohu were unaffected. Santiago et al.…”

“…Hossain et al. () reported higher growth of 5‐ and 12‐month stunted juveniles of rohu and mrigal Cirrhinus mrigala (Ham.) compared to younger ones in polyculture with Nile tilapia, which confirmed the existence of CG.…”

“…() in their review of cyprinids have reported full, partial, as well as no CG responses. Stunted juveniles of bighead carp Aristichthys nobilis (Richardson 1845) have shown lower weight and length attainment in the grow‐out phase (Santiago, Gonzal, Aralar, & Arcilla, ), while in another cyprinid, rohu Labeo rohita (Hamilton, 1822), stunted juveniles exhibited a CG response in the subsequent grow‐out phase under polyculture (Hossain, Little, & Bhujel, ). Such reports, in favour and against the CG response in cyprinids, present an ambiguity on the existence of the phenomenon in stunted rohu, the important Indian major carp.…”

Effect of Pond Fertilization with Vermicompost and Some Other Manures on the Pathogenic Bacterial Populations of Treated Waters

“…In the recent years, utilization of animal wastes for pond fertilization has become a very common practice in the modern aquaculture systems (Dhawan and Kaur, 2002a, b;Hossain et al, 2003;Jha et al, 2004). However, this practice has caused noticeable harm to the environment by proliferating growth of pathogenic bacteria like Aeromonas sp.…”