Abstract:
With capture fisheries output being threatened by overfishing and dwindling stocks, a long term
vision for the supply of fish to the worlds growing population is aquaculture. However, the issue of fish feeds
remains one of the challenges facing the aquaculture sector where the sources for most of the ingredients used
for fish feed formulation are the same as those used for human consumption. Hence, a strategic focus for
aquaculture must be to derive new sources, primarily taken from outside the human food chain, and to derive
them mainly from primary producers for example marine algae (seaweeds). However, the use of seaweeds as
animal feed is, among others, determined by their heavy metal status. U. rigida and H. opuntia are some of the
seaweed species primarily used in artisanal fishery at the south coast of Kenya as fishing baits and have the
potential for use as supplement ingredients in the formulation of fish feed for the widely farmed Nile tilapia. For
purposes of determining their safety for use in fish feeds, a study was carried out to determine the concentration
levels of Arsenic, Cadmium, Lead and Mercury. The heavy metals were investigated with respect to seasonal
and site variations. Seaweed sample analysis was done following Atomic Absorption Spectroscopy. The values
obtained were compared to the World health Organization (WHO) recommended levels for heavy metals in food
and feed supplements. The concentration levels were significantly different (p<0.05) in the two seaweed species,
varied with seasons and sites and compared variably with the WHO recommended levels.
