Exploring the trophic structure in organically fertilized and feed-driven tilapia culture environments using multivariate analyses

Abstract

Reports of similar yields in manure and feed-driven tilapia culture environments raise questions on food utilization in these environments. The possibility that similar production rates are because of utilization of di¡erent foods was investigated using exploratory techniques of multivariate analyses. Using factor analysis, trophic pathways through which food becomes available to ¢sh were explored, and using ANOVA models, water quality, sediment quality and tilapia growth and yields were compared. Conceptual graphic models of the main ecological processes occurring in feed-driven and organically fertilized environments are presented and discussed. In both environments, autotrophic and heterotrophic pathways are important processes that result in the availability of natural foods that are utilized by the ¢sh. Extrapolated ¢sh yield data indicate that with equal nutrient input and stocking density, organically fertilized environments could achieve production rates similar to those in feed-driven environments. The general assumption that supplemental or complete foods are well utilized by tilapia in outdoor stagnant ponds remains challenged, and further research on tilapia feeding behaviour and food selection in feed-and organic fertilizer-driven environments is needed. Ã Signi¢cant at the 0.05 level. ÃÃÃ Signi¢cant at the 0.001 level.Same letters in the multi-comparison of means columns indicate no signi¢cant di¡erence at the 0.05 level. a4b4 Á Á Á. Coe¡., coe⁄cient; Sign., signi¢cance level: NS, not signi¢cant; %SS, percent of total sum of squares; TRT, treatment.Aquaculture Research, 2006, 37, 151^163 Trophic structure in pellet fed and organic fertilized ¢sh ponds P N Muendo et al.

Uptake of nitrogen from natural food into fish in differently managed polyculture ponds using 15N as tracer

“…Under traditional pond management, other fish species than grass carp also assimilated nitrogen from natural food resources. Especially high enrichments in 15 N were observed for Nile tilapia under traditional pond management which showed the strong dependency of Nile tilapia on a wide range of natural food resources as reported by many researchers (Beveridge et al 1989;Dempster et al 1993;Muendo et al 2006). Mrigal, known to be a bottom feeder on zoobenthos (Milstein et al 2002), also showed higher enrichments of the tracer within the first 15 days after tracer application.…”

Effects of stocking density and presence or absence of soil base on growth, weight variation, survival and body composition of pearlspot,Etroplus suratensis(Bloch) fingerlings

“…Most of the soil parameter values except organic carbon were higher at harvest compared with initial. It occurred mainly by the accumulation of nutrients from metabolites and feeds in the sediments (Islam, Sarker, Yamamoto, Wahab & Tanaka ; Muendo, Milstein, van Dam, Gamal, Stoorvogel & Verdegem ) and the incidence was supported by Avnimelech and Ritvo () who reported that cultured aquatic animals may contain between 5% and 40% of nutrients in the feed (carbon, nitrogen, phosphorus) and the rest is accumulated in pond sediments. Significantly higher amount of soil phosphorus and nitrogen contents in the higher density treatments compared with those in the lowest density indicated more accumulation of nutrients in presence of greater number of fish.…”

Improved Sustainable Aquaculture Systems for Small-Scale Farmers in Northern Vietnam

“…Unsuitable water quality elements such as water temperature (Sifa et al 2002;Cagauan 2001;Black 1998;Alcaraz et al 1993;Chervinski 1982), water oxygen (Black 1998;Ross 2000) and water pH (Svobodova et al 1993) levels were shown to have a negative effect on fish growth. Especially within extensive and semi-intensive aquaculture systems, fish growth is correlated with the availability and abundance of natural food resources (Rahman et al 2008b;Muendo et al 2006;Schroeder et al 1990;Spataru et al 1983;Kolar and Rahel 1993;Pucher et al 2011b), and both water quality and the availability of natural food are primarily or secondarily affected by the suspended particle load. During the research in Yen Chau district, ponds with maize and cassava fields on yellow soils in the watershed above and fed by rain water, showed a distinctly higher suspended solids load than ponds located on the rice paddy plateaus and fed by reservoir water.…”