Consumer preference, growth and profitability of African catfish (Clarias gariepinus) grown in treated and aerated wastewater fed ponds in Kumasi, Ghana

Abstract

Recycling of wastewater provides a substantial solution to the global issue of water scarcity and high water use in aquaculture. However, this sustainable way of wastewater use has not been given much attention and exploration. This study focused on the consumer preference for fish grown in treated wastewater as well as the effect of aeration on the growth performance and economic benefit of African catfish (Clarias gariepinus) grown in treated wastewater. Two hundred (200) respondents from two communities (Chirapatre and Gyinyase) near the wastewater treatment plant in Kumasi were interviewed to determine their willingness to accept and pay for African catfish grown in treated wastewater. For the growth trial, a total of 600 fish (of average initial weight 39.12g) were stocked in two maturation ponds with 4 h (3:00am-7:00am) of aeration daily. The trial lasted for 12 weeks and variables monitored included the survival, growth performance (weight gain, specific growth rate, and yield) and water quality. Fish cultured in non-aerated wastewater ponds (NWFPs) under similar conditions as in aerated wastewater-fed ponds (AWFPs) served as control. The results indicated most important considerations for consumers in their choice of fish to consume were in order of importance; food safety, freshness of fish, taste and packaging. The proximity of consumers to the treatment plant, the price of fish, religion, and age and whether or not they were fish consumers affected their willingness to pay for African catfish grown in the treated wastewater significantly. For the growth trial, dissolved oxygen concentrations in the aerated ponds were significantly higher than in the NWFPs and this led to more than a doubling of the growth rates in the African catfish grown in the AWFPs (189.10g AE 11.32) as compared to the NWFPs (90.70g AE 11.59). The pond aeration improved fish growth significantly (p < 0.0098). On economic benefit, the aerated system yielded profits of 618.83 (€103.13) as compared to a loss of 104.99 (€17.50), which was incurred in the non-aerated ponds. Education of the consumers on the process of wastewater treatment and establishment of food safety guidelines will therefore be recommended to increase consumer interest in consuming fish from the treated wastewater.

Safe and sustainable business models for water reuse in aquaculture in developing countries

“…The principal mechanisms for fecal bacteria removal in maturation ponds are time and temperature, high pH (> 9) and high light intensity, combined with high dissolved oxygen concentration (Mara 2004;Kayombo et al 2010). The use of paddle-wheel aerators at times of low oxygen levels can significantly support fish production (Sey et al 2021) but should be solar-powered to avoid increased operational costs.…”

“…From a consumer perspective in both countries, no negative response related to wastewater-fed fish cultivation has been reported. Consumer surveys conducted, for example, in 2014 and 2018 in Kumasi (Ghana) showed that product attributes that influence consumers' fish-buying decisions were related to product price, size and perceived fish quality while the source of the fish was among the least important product attributes (Gebrezgabher et al 2015;Sey et al 2021), similar to results from Nigeria (Adeola et al 2016) or the purchase of potentially wastewater-irrigated vegetables (Keraita and Drechsel 2015). In Ghana, where the irrigation water in and around cities is severely polluted, the limited interest in the water source has been attributed to low education and health risk awareness (Drechsel and Keraita 2014).…”

“…The mean WTP for both fresh tilapia and smoked catfish with wastewater origin was comparable to their respective (freshwater) market prices (Gebrezgabher et al 2015). Interestingly, among households in treatment plant proximity, 66% of the respondents were not concerned about the source of the fish and those with knowledge of the plant and fish preparation had an even higher probability of buying them than consumers living elsewhere in the city (Sey et al 2021). It appears that having some knowledge of the water treatment process and the facility made consumers more comfortable with eating the fish (Howell 2021).…”

“…This is supported by a solar-powered aerator for both maturation ponds (Figure 8). Earlier research, when the ponds were still used for the whole cycle of fish farming, had shown that additional aeration was important for the viability of such a system (Sey et al 2021). More recently, the treatment plant has been re-engineered to include a triple biogas digester to further improve the incoming water quality.…”

“…This change was accepted as the business continued operating at a profit, achieving a gross margin of 69% in the first year of operation and 45% in the second year. An important component for the growth of fish in the maturation pond is additional aeration (Figure 8) (Sey et al 2021). In 2020, TriMark's operations and finances were significantly affected by the Covid-19 pandemic: (i) The government-ordered lockdown of restaurants interrupted a major income source for the whole sector (Okai 2020); (ii) staff were not allowed to resume work and maintain the system; and (iii) authorities feared that wastewater which potentially carries the virus might not be safe for aquaculture 2 .…”