Effects of stocking density on growth, yield and profitability of farming Nile tilapia, Oreochromis niloticus L., fed Azolla diet, in earthen ponds

Abstract

Two consecutive experiments were conducted to study the e¡ects of stocking density on growth, food utilization, production and farming pro¢tability of Nile tilapia (Oreochromis niloticus) ¢ngerlings (initial mean weight:16.2 AE 0.2 g) fed Azolla, as a main component in diet. In experiment 1, ¢sh were hand-fed twice daily with three isonitrogenous (28.5% crude protein) and isocaloric (14.5 kJ g À1 ) diets A30, A35 and A40 containing 30%, 35% and 40% Azolla, respectively, for 90 days. Diets were formulated by mixing Azolla with locally available by-products. No signi¢cant di¡erences were found in growth parameters and production (P40.05). Total investment cost was signi¢cantly higher with A30 (Po0.05), but same pro¢tability values were obtained with all diets (P40.05). In experiment 2, three stocking densities, 1, 3 and 5 m À 2 , were assigned to three treatments T 1 , T 2 and T 3 respectively. Fish were hand-fed twice daily with diet A40. The ¢nal mean weight (89.53^115.12 g), the mean weight gain (0.811.10 g day À1 ), the speci¢c growth rate (1.90^2.20% day À1 ) and the apparent food conversion ratio (1.29^1.58) were a¡ected by stocking density, with signi¢cant di¡erence (Po0.05) at 5 m À 2 , compared with the other densities. Stocking density did not affect survival rate (P40.05).Yield and annual production increased with increasing stocking density, ranging from 7.10 AE 0.90 to 25.01 AE 1.84 kg are À1 and 28.79 AE 3.66 to 101.42 AE 7.48 kg are À1 year À1 , respectively, with signi¢cant di¡erences between all densities (Po0.05). Higher stocking density resulted in higher gross return and lower cost of ¢sh production, with signi¢cant variations (Po0.05). The net return increased with increasing stocking density (Po0.05). However, both densities of 3 and 5 m À 2 produced the same pro¢tability values. On the basis of growth values and economic return, it was concluded that Nile tilapia could be raised at a density of 3 ¢sh m À 2 with A40 to improve production and generate pro¢t for nutritional security and poverty alleviation in rural areas.

Desempenho produtivo da tilápia do nilo em tanques-rede numa represa pública: modelo empírico de classificação

“…Em relação às taxas de sobrevivência (TS), ABOU et al (2007) reportam que a TS não é dependente da DE, em contraposição, já YI et al (1996) consideram que a baixa TS diagnosticada (57,2%) em seus estudos estaria correlacionada diretamente com as altas DE, que, por sua vez, promoveriam alto consumo de oxigênio dissolvido no período noturno, com reflexos nas primeiras horas da manhã. Neste estudo, obteve-se uma TS satisfatória, pois variou de 88 a 93% (Tabelas 1 e 2).…”

Lake-Based Nursery Rearing of Nile Tilapia (<i>Oreochromis niloticus</i>) Fingerlings in Nylon Hapas: Effects of Stocking Density on Growth, Survival and Profitability

“…However, increasing it to a certain level may enhance total fish yield and lead to higher gross and net return at a lower cost of production [20] [21] [27]. Moreover, where land, water, manpower and other facilities are limiting it may be more profitable to adopt higher stocking densities [28].…”

Produccion de tilapia nilotica (Oreochromis niloticus L.) utilizando hojas de chaya (Cnidoscolus chayamansa

“…), donde se obtuvo el mismo resultado que con la ración completa (El-Sayed, 1999, 2006. Así mismo, la azolla (Azolla filiculoides) es una planta acuática que ha sido usada como alimento en su forma natural para peces en China (Lu & Li, 2006) y estudiada como sustituto de harina de pescado en sistemas a gran escala en áreas rurales de África (Abou et al, 2007). La aplicación potencial de plantas terrestres como complemento alimenticio ha recibido escasa atención.…”