The composition, nutritional status and digestibility of the diets of Sarotherodon mossambicus from nine man-made lakes in Sri Lanka

Abstract

SynopsisThe dietary composition and the nutritional status and the (digestibility of the diets of Sarotherodon mossambicus from nine reservoirs in Sri Lanka were evaluated. 'The feeding habits of S. mossambicus were variable from reservoir to reservoir; they ranged from herbivory to total carnivory. The protein, total lipid, carbohydrate and total organic matter content of the ingested material were related to the dietary composition and ranged from 18.53% to 35.15% (t-24.18%), 5.94% to 9.84% (X-7.91%), 11.6% to 34.7% (X-22.34%) and 34.4% to 64.4% (t-45.71%), respectively. Irrespective of the feeding habits, the diet contained a significant proportion of organic material which cannot be accounted for by protein, total lipid and carbohydrate. As much as the ingested material was related to the feeding habit, the digestibility of the nutrient components was related to the food material devoured. For example, the mean digestibility of the total organic matter in S. mossambicus feeding on detritus, plants and animal were 36.85, 33.5 and 29.5 respectively, and compared well with observations from elsewhere. It is hypothesised that the favourable nutrient quality of the available dietary material in the reservoirs of Sri Lanka, which could be and is effectively utilized by S. mossambicus, may have been, at least partially, responsible for its almost unprecedented success in Sri Lanka.

Detritivory in two Amazonian fish species

“…An alternative hypothesis is that algal carbon is being consumed not as deposited living algae, but rather as detritus formed from decomposition or excretion of the algae, and that could not be measured as chlorophyll. The organic matter ingested by L. pardalis and P. nigricans is within the broad ranges (5-70%) reported for other fish belonging to this trophic guild (Gneri & Angelescu, 1951;Bowen, 1979Bowen, , 1982Odum, 1973;Bowen et al, 1984;De Silva et al, 1984;Araujo-Lima & Hardy, 1987;Almeida et al, 1993;Sutton & Bowen, 1994;Yap, 1995;Resende et al, 1995;Catella, unpubl.). Crude protein contents were similar to the values reported for P. platensis and Tilapia mossambica (Peters) in South America (3·5-12%) (Bowen, 1981(Bowen, , 1984.…”

“…The tracers used were HROM and hydrolysis-resistant ash (HRA), both of which are not affected by digestive processes (Buddington, 1980;Bowen, 1981Bowen, , 1984De Silva et al, 1984;Galetto & Bellwood, 1994). The calculations were done separately and the digestibility was estimated by standard calculations (Smith, 1989).…”

A study on an herbivorous fish, Oreochromis niloticus L., diet and its quality in two Ethiopian Rift Valley lakes, Awasa and Zwai

“…Other workers reported that A.E. values obtained using all the above three reference materials did not show significant differences (De Silva et al, 1984). Further, higher A.E.…”

Detritus Feeders

“…This so-called detritivore is labeled as a notorious diet switcher (see Chapter 11), varying all the way from an algae-detritus diet to a carnivorous one (DeSilva et al, 1984;DeSilva, 1985). In fact Maitipe and DeSilva (1985) describe detritivorous, phytophagus, and zoophagus populations in 12 Sri Lankan reservoirs with seasonal variations occurring among the feeding types.…”