Abstract
Feeding ratio and frequency have substantial effects on food digestion and assimilation in fish, yet few attempts have been made to determine their influences on the bioaccumulation of trace metals. In this study, juvenile Acanthopagrus schlegeli were exposed to either water-borne or dietary cadmium (Cd) at different feeding ratios (0, 2, or 4% body weight d(-1) [BW d(-1)] under waterborne Cd exposure and 1, 2.5, or 4% BW d(-1) under dietary Cd exposure) or feeding frequencies (1, 2 or 8 times d(-1)) for 5 wk. Under waterborne Cd exposure, the fish fed 0% BW d(-1) or 8 times d(-1) showed significantly lower growth rates and those fed 0% BW d(-1) or 1 time d(-1) exhibited higher Cd body burdens and Cd uptake rates compared to the other groups. The gut showed a significantly higher waterborne Cd uptake rate than the gills when fish were fasted or fed only 1 time d(-1). These results suggest that starvation and low feeding frequency facilitate waterborne Cd uptake. Under dietary Cd exposure, the fish fed 4% BW d(-1) or 2 times d(-1) grew faster. Cd body burden and Cd assimilation were higher in fish fed 2.5% BW d(-1) or 2 times d(-1). Dietary Cd retention was positively correlated with feed efficiency, suggesting the utilization of Cd probably coincides with the essential nutrients in fish. Overall, this study demonstrates that different feeding strategies significantly influence waterborne and dietary Cd bioaccumulation in marine fish. Therefore, feeding conditions have to be considered carefully for managing trace metal contamination in marine fish farming.
Highlights
128 million tons of fish provided about 3 billion people with almost 20% of their average per capita intake of high-quality animal protein in 2010 (FAO 2012)
Several studies have demonstrated that dietary trace metal assimilation is closely related to the ingestion rate (IR) and gut passage time (GPT) of diets (Zhang & Wang 2006a, Croteau et al 2007)
A growing body of study has revealed that changes in food quality have a significant effect on dietary metal assimilation in farmed marine fish, little is known about the influence of food quantity management on dietary metal bioaccumulation in farmed fish
Summary
128 million tons of fish provided about 3 billion people with almost 20% of their average per capita intake of high-quality animal protein in 2010 (FAO 2012). With respect to Cd bioaccumulation in black sea bream, our previous studies demonstrated that the gastrointestinal tract is the main site for dissolved Cd uptake (Zhang & Wang 2007a) and dissolved Cd bioaccumulation is apparently affected by metal pre-exposure (Zhang & Wang 2005, 2006b), water salinities (Zhang & Wang 2007b) and body size (Zhang & Wang 2007c). It remains unclear how feeding ratio and frequency influence growth and Cd bioaccumulation in black sea bream. We conducted a 5 wk feeding experiment to examine the effects of feeding ratio and frequency on (1) growth performance and feed utilization, (2) Cd body burden and (3) waterborne Cd uptake and dietary Cd assimilation efficiency in juvenile black sea bream
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