WWW.WAS.ORG • WORLD AQUACULTURE • JUNE 2024 25 (CONTINUED ON PAGE 26) substitution of commercial supplements with C. vulgaris during the initial 21 days post-hatching. In order to test the effectiveness of C. vulgaris as an enrichment for pikeperch we ran a trial comprised three treatments of live feed enrichment and one control group, administered to the larvae over the first 21 days post-hatching. The first treatment involved enriching the live feed with the “Selco Spresso” diet by INVE, while the second treatment utilized Ascorbic acid for enrichment. The third treatment employed C. vulgaris as the enrichment for live feed, while the control treatment utilized Nannochloropsis occulata. Following the 21-day period, a representative sample of larvae (100 per treatment) from each group underwent a 180-minute challenge in high salinity (15ppt) to evaluate resilience and cortisol levels. Additionally, data on growth and survival were recorded. Outcomes The results support the importance of the vitamin C for the pikeperch larvae. When looking at growth we can see how the treatments exposed to more vitamin C have a higher growth, followed by the control treatment, although no statistical differences were found between all the treatments (Figure 1). On the other hand, it can be observed there was a clear difference when we look at survival after 21 days (Figure 2), mostly between the vitaminexposed treatments versus the control. Although not statistically different, the Spresso treatment had the highest survival, followed by the Chlorella and the vitamin C treatment. Larval vitamin C content is presented in Figure 3. After running the 21 days experiment, we exposed 110 larvae per treatment to high salinity conditions during 180 minutes. No larvae survived from the control treatment and the Spresso treatment had the highest survival with 37%, followed by the Chlorella treatment (10%) and Ascorbic Acid treatment (7%) (Figure 4). We then compared the cortisol level of the larval that survived the experiment against a set of larvae that were not exposed to the salinity test. In Figure 4, the cortisol levels from the different larvae are presented. As expected, the larvae not exposed to the salinity test (Control) had the lowest cortisol levels, followed by the larvae from the Spresso treatment correlating to the highest survival rate from the salinity test. The larvae from the Chlorella treatment had the third lowest cortisol level flowed by the ascorbic acid treatment, then again correlating to the salinity test survival results. Conclusions Overall, our experience indicates that larvae exposed to the commercial diet (Spresso, INVE) yielded the most favorable outcomes, particularly in terms of growth, survival and stress resilience. These results were anticipated as Spresso not only contains vitamin C but also a variety of nutrients and supplements tailored to enhance larval performance. However, one might question why we would explore other enrichments when there are already comprehensive commercial options like Spresso available. The FIGURE 1. Pikeperch larval growth parameters (a. Total length and b. Myomere height) after 21 days from four treatments (Chlorella, Vitamin C (Ascorbic Acid), Spresso and Control (Nannochloropsis). FIGURE 2. Pikeperch larval Survival after 21 days from four treatments (Chlorella, Vitamin C (Ascorbic Acid), Spresso and Control (Nannochloropsis).
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