Author(s)

Sinthumule Hangwelani, Mokgoebo Matjutla John, Gumbo Jabulani Ray

Abstract

Inland aquaculture systems are on the rise worldwide, including in South Africa to provide affordable fish and promote local economic growth. But the main cost input, is the supply of fish feed. Thus, there is a need to develop local fish feed to offset the rising cost of commercial fish feed. The study was aimed at assessing the effects of a local low-cost pigeon pea feed on the limnology of aquaculture systems using three types of feed, viz. commercial feed (control), pigeon pea feed (one roasted and one raw). The results as computed by the Czekanowski coefficient statistical analysis showed that the commercial and low-cost feed had similar environmental impacts (p < 0.05). When environmental fac- tors fluctuated, there was a fluctuation in phytoplankton composition which led to the proliferation of cyanobacteria species in all the aquaculture tanks. A total of 446 phytoplankton species were identified in the commercial feed tank, 601 species in the roasted fish feed and 630 species in the raw fish feed. Phytoplankton spectra were recorded from six taxonomic groups namely: Chlorophyta, Euglenophyta, Dinophyta, Bacillariophyta, Chryasophyta and Cyanophyta (the dominant taxonomic group). Most of the physio-chemical parameters were within the recommended aquaculture guidelines of the Department of Water & Forestry, making the feed suitable for fish feeding. The results show that the three fish feeds (commercial feed, roasted pigeon pea feed and raw pigeon pea feed) all influenced the health of the aquaculture system with both beneficial and harmful algae growing in the system. This shows that the pigeon pea formula has similar impacts on the aquatic health of aquaculture tanks.

Keywords

Cyanobacteria, Cyanotoxin, phytoplankton, water quality, aquaculture, pigeon pea