The nutrition of stomachless phytoplanktivorous fish in comparison with Tilapia

Abstract

The contents of alimentary tracts of stomachless phytoplanktivorous fish, including silvercarp (Hypophthalmichthys molitrix), Esomus danrica thermoicos, and Amblypharyngodon meletinus were investigated microscopically and compared with those of Tilapia (Oreochromis mossambicus, a fish with stomach).The predominance of detritus in the food and the low efficiency with which phytoplankton is utilized prove, that stomachless fish are not primarily herbivorous. The possibility of omnivorous feeding as an alternative is discussed. These results may contribute to our understanding of the role of filterfeeders in aquaculture and ecosystems.

Gut contents of silver carp, Hypophthalmichthys molitrix, and the disruption of a centric diatom, Cyclotella, on passage through the esophagus and intestine

“…Lazzaro, 1987 . Although phytoplankton are considered to be the major nutritional component of many filter-feeding fishes, the digestibility of algae has been a matter of debate for Ž decades, i.e., gut content comparison between fore-gut and hind-gut Ni and Chiang, . Ž 1954;Spataru, 1977;Bitterlich, 1985a and analysis of digestive enzyme Bitterlich, . 1985b,c show that it is rather difficult for silver carp to digest algae with cellulose cell wall, while studies by using isotope techniques indicates that this fish digests green Ž algae and cyanobacteria efficiently Iwata, 1976;Shi et al, 1976;Zhu, 1982;Zhu and .…”

“…The examination of the gut contents of silver carp collected from cultured pond showed that most of the algae present in the fore-gut Ž . appeared intact in the hind-gut Ni and Chiang, 1954;Spataru, 1977;Bitterlich, 1985b .…”

“…In-vitro incubation of a filamentous cyanobacterium Anabaena flos-aquae with the digestive juices of silver carp resulted in only 9.5% of the algal protein being hydrolyzed ( )Ž . to free amino acids Bitterlich, 1985b . No cellulase in the gut of silver carp was found Ž .…”

Applicability of gill raker filtrates and foregut contents in the diet assessment of filter-feeding Asian carps

“…In this respect, Vörös et al (1997) found that silver carp were effective in filtering algae larger than 10 µm, even though other studies reported lower values (i.e., 4-5 µm) for the minimum size of filtered particles (Omarov 1970, Kucklentz 1985, Xie 1999. Silver carp is considered to be primarily a phytoplankton feeder (Kolar et al 2007, and references therein), although Bitterlich (1985) suggested that it may not be able to meet its energy requirements by consuming phytoplankton alone. This is probably due to the low digestibility of some phytoplankton taxa (Dong et al 1992) and to the gut fluids of silver carps lacking the cellulase enzyme needed to break down algal cell walls (Kolar et al 2007).…”

The trophic ecology, functional morphology and phylogeny of the hemiramphidae (beloniformes)

“…Oreochromis mossambicus, which also has a pharyngeal mill, gastrically digests algae and has an ingested carbon assimilation efficiency of between 50 and 80%, Bitterlich, 1985). Klumpp and Nichols (1983) demonstrated the lack of acidity in the alimentary tract of H.…”