Sustainable Aquaculture @ Stirling

The University of Stirling partnered with Nutreco and Victory Farms in Kenya to assess the impacts of shortening the commercial production cycle of a local strain of caged tilapia to produce higher yields of small-sized fish (200g vs. 400g fish), thus improving feed efficiency, eliminating costly mono-sex technology, and enhancing cash flow. Additionally, nutrient outcomes and environmental impacts were assessed comparing the novel and conventional systems.

This project also undertook market research to understand urban and rural demand and preferences for various sizes of tilapia compared with other animal-sourced foods. It found a large and largely underserved rural demand for 200g fish, which could be supplied through production models that produce a higher percentage of smaller fish by partially harvesting fish part-way through the cycle. This partial harvest also supports improved cash flow, which can be a limited factor for smallholder producers.

This project was funded by KTN Agrifood Africa Innovation Rounds, with in-kind support from Nutreco and Victory Farms. The results have been published in the journal “Aquaculture”.

Spreadsheet model

Alongside the field research we have developed a spreadsheet model which is designed to help farmers and extension workers consider different production strategies for tilapia produced using cages in tropical lakes. In particular strategies that include producing a greater proportion of smaller fish for price sensitive consumers. It can also be used as an educational tool to help focus on different aspects of cage farm management. As it uses mathematical models it should not be considered an accurate prediction of farm production or financial performance. However, many variables can be adjusted according to the users knowledge and experience, so we hope that it will be useful in at least stimulating ideas and further experimentation.

The spreadsheet models the growth of tilapia in one or more cages over a period of time chosen by the user and indicates likely production volumes, fish sizes and feed usage. By entering basic farm costs and selling prices, an indication of financial returns is also provided. Up to four production scenarios can be compared and mixed to develop an overall strategy. The scenarios include the possibility for a partial harvest of a cage to produce an interim harvest of smaller sized fish.

Whilst the spreadsheet is designed to be as easy to use as possible, it requires some complexity to be adaptable to different circumstances. We have therefore written a manual to accompany the spreadsheet which provides further information about how to use the spreadsheet, and the considerations and principles on which it is based. There is also a set of video tutorials available on YouTube (links below).

Download links:

Tilapia Production Spreadsheet (v1.1) (Excel)

Tilapia Spreadsheet Manual (v1.1) (PDF)

Tutorial Videos (YouTube Playlist)