Use of the microalga Pavlova viridis as enrichment product for the feeding of Atlantic cod larvae (Gadus morhua)

• P. viridis was evaluated as live feed enrichment product for the feeding of Atlantic cod larvae.
• P. viridis enrichment influenced microbial communities.
• P. viridis enrichment resulted in similar feed ingestion rates in comparison to a commercial enrichment product.
• P. viridis supported development and growth of cod larvae.

An Atlantic cod larva (Gadus morhua) feeding experiment was carried out to compare three different live feed enrichment products for Brachionus ibericus and Artemia salina: 1) Nannochloropsis sp. microalgal concentrate (frozen) (N), 2) Pavlova viridis microalgal concentrate (frozen) (P), and 3) Larviva Multigain® (BioMar, Denmark) — formulated commercial product (CP). Over the experimental period of 42 days larvae of groups P and CP showed significantly higher instantaneous growth rates (G: 0.074 ± 0.001 d− 1 and 0.079 ± 0.009 d− 1) than larvae of group N (G: 0.04 ± 0.0 d− 1). Survival at the end of the trial of group CP was highest (20 ± 8%), whereas significantly lower survival was observed for groups P (7 ± 2%) and N (< 0.5%). Live feed ingestion by means of gut fullness index (GFI), evaluated at 4, 15 and 27 days post hatch (dph), was high for the larvae of group CP (GFI: 1.2 ± 0.1, 1.4 ± 0.0, 1.7 ± 0.2, respectively) and group P (GFI: 1.4 ± 0.1, 1.3 ± 0.1, 1.8 ± 0.2, respectively) compared to group N (1.0 ± 0.0, 1.1 ± 0.1, 1.2 ± 0.1, respectively). Larvae fed with CP enriched live feed were able to withstand an extended period of feed deprivation (of 4 or 5 days), whereas groups N and P were not able to re-initiate growth beyond the point-of-no-return, assessed on 5, 16 and 28 dph. Bacterial community diversity of tank water, feed and larvae of the three groups revealed that treatments N and P lead to similar, highly diverse microbial communities in comparison to group CP. Microalgal enrichment using P. viridis was not able to sustain the same survival rates as the commercial product, but resulted in a similar growth performance and feed ingestion rates and had a significant effect on microbial community diversity.