Carnivorous fish such as the sea bass have known to be heavily reliant on fishmeal as the primary source of protein in their diet. However, with the environmental impacts of the fishmeal industry, recent tests suggest that insect protein have proven itself worthy as a sustainable alternative.
Feed Trial Parameters
According to feed trials done by HCMR research institute in Greece, fishmeal replaced with mealworms (Tenebrio Molitor) in the diet at different levels have shown positive results with regards to FCR and mortality. European Sea Bass fingerlings of ~4g were monitored over a period of 9 weeks with 3 different levels of replacement. TM0 as control (0% substitute), TM30 (30% substitute) and TM100 (100% substitute). After 9 weeks, 8 fingerlings in each tank were anaesthetised with blood samples drawn for histopathology to assess their gut health. An additional 60 fish per group were kept for Vibrio Harveyi disease challenge, a vital pathogen found in marine species. Thereafter, the cumulative mortality score was recorded for 10 days.
At the end of 9 weeks, TM100 had the lowest FCR of 0.77 (Control FCR:0.87). The FCR performance of both substitute groups surpassed the control group with a notable improvement for TM30. Weight gain was 13.7% higher than control (Fig.1) with a 7% lower FCR (Fig.2).
Disease Challenge Result
The results were surprising with both substitute groups outperforming the control group, showing better gut health and lowered mortality. For TM30, presence of abnormal intestinal villi in the gut was lowered to 2 (control: 5). Reducing the cumulative mortality of TM30 by 45%.
The benefits of replacing fishmeal with mealworm in the diets of sea bass are clear, environmental or growth efficiency. Other research on mealworms inclusion in aquafeed has also reported a positive effect on growth.