Freshwater Institute Report

Freshwater Institute Field Trial

A field trial of the TimberFish Recirculating Aquaculture System was recently completed at the Freshwater Institute, a program of The Conservation Fund, located in Shepherdstown, West Virginia.

The Conclusions Section of the Final Report “Evaluation of Timberfish’s Proprietary System for Producing Fish Using Wood Chips at the Conservation Fund”, May 2011, prepared by The Conservation Fund Freshwater Institute, Shepherdstown, WV, is as follows.

“5.0 Conclusions

The Timberfish system successfully cultured rainbow trout from fingerling (26 g) to pan size (396 + 13 g) in 169 days (24 weeks) with only 1% mortality. Rainbow trout growth rate in the Timberfish system was nearly as fast as control fish fed to near satiation while grown at the same time in a single‐pass system at 12.5‐13oC. In addition, the Timberfish system successfully maintained good water quality for rainbow trout culture, even with a system hydraulic retention time of between 50‐100 days. While few organisms were found in the selector tray, invertebrates such as snails, earthworms, round worms, planarians, and fly larvae were observed in the system. Although we had no clear indication how much of the rainbow trout diet consisted of these invertebrates or periphytic growth, overall feed conversion in the rainbow trout was excellent at approximately 0.7 pound of feed per pound of gain. Thus, potentially 1/3 of the rainbow trout food intake may have come from organisms and periphytic growth that was produced within the Timberfish system. For these reasons, the Timberfish system appears to have considerable potential for rainbow trout production with little water or wastewater footprint and with reduced feed input.”

The report also contained a comparison of fish fillets from the TimberFish and a control system with respect to proximate analysis and fatty acid profile. Interestingly, while the TimberFish fillets had slightly more protein than the control fillets, they also had significantly less crude fat (3.9% vs 6.8%). However, the fat that was present in the TimberFish fillets was considerably more beneficial than that present in the control fillets. Quoting again from the Report:

“A fatty acid profile comparison indicated some key differences in fatty acid compounds when comparing the TimberFish and control fish (Table 5). From a nutritional standpoint, the benefit of incorporating fish into the human diet is the presence of elevated concentrations of PUFA1 compounds in fish as compared to other protein sources. In this analysis, noteworthy differences were apparent regarding the PUFA:MUFA2 ratio when comparing TimberFish to control fish. Specifically, the TimberFish fillets had a 0.77 PUFA:MUFA ratio and the control fish had a 0.71 PUFA:MUFA ratio indicating that the TimberFish were likely consuming organisms (e.g. invertebrates, biological floc) that imparted higher concentrations of PUFA compounds to the fish compared to the control fish. Further, the TimberFish omega‐3:omega‐6 fatty acid compound ratio was 2.6 compared to a ratio of 2.0 for the control fish, which is also considered nutritionally advantageous. And of particular note, the omega‐3 fatty acid compound cis‐4,7,10,13,16,19‐Docosahexaenoic (DHA) was found to be at a concentration of 17.80 +/‐ 1.24 g/100g of tissue in the TimberFish fillets and at 13.02 +/‐ 0.40 g/100g of tissue in the control fish fillets. It is considered by nutritional health professionals that incorporation of foods high in DHA results in multiple health benefits. And despite the fact that the TimberFish fillets had a lower concentration of crude fat than the control fish, the TimberFish fillets had a notably higher concentration of DHA.”

1 PUFA stands for polyunsaturated fatty acid.
2 MUFA stands for monounsaturated fatty acid.

Click here for a link to the full report.