Investigating the effects of extended artemia live feed feeding on larvae growth and survival in Ballan wrasse (Labrus bergylta)

Ffion Gibson * ⏐ Rebecca Stringwell * ⏐ Paul Howes * ⏐ Mike Gwilliam * ⏐ Robert Smith * ⏐ Isla Monaghan *

*Department of Biosciences, Centre for Sustainable Aquatic Research, Swansea University, Swansea, Wales, SA2 8PP, UK

Pages: 42-48 ⏐ Published: 27 Nov 2025 ⏐ DOI: https://doi.org/10.70145/BiSh0009

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Abstract

Ballan wrasse (Labrus bergylta) are increasingly being relied upon as cleaner fish in salmon farming, but commercial rearing faces major challenges, particularly low larval survival rates. One key constraint is the lack of a standardised weaning protocol, with uncertainty around when and how to transition larvae from live feed (Artemia) to dry diets. This preliminary study evaluated three weaning strategies to identify approaches that improve growth and survival. All larvae were fed enriched Artemia from hatching to day 52, after which treatments diverged: (1) standard weaning (C1; dry feed introduced at day 52 with a short co-feeding period), (2) extended weaning (T1; continued co-feeding of Artemia and dry feed for three additional weeks), and (3) delayed weaning (T2; Artemia-only feeding for three extra weeks followed by a direct switch to dry feed with no co-feeding). Six 50 L tanks, each stocked with 100 larvae, were randomly assigned to treatments (n = 2 per group). Morphometric data (total length, wet weight) and survival were recorded from day 52 to day 101 post-hatch. Survival at day 99 was significantly lower in the standard group (61–72%) compared to extended (90–96%) and delayed (98%) weaning. By day 101, larvae in extended and delayed groups had significantly higher weights than controls. Total lengths followed a similar trend, with extended and delayed larvae significantly exceeding controls. Extended weaning produced the largest larvae, while delayed weaning yielded the highest survival. These findings indicate that prolonging the period of live Artemia feeding, either through co-feeding with dry feed (T1) or by delaying the onset of weaning (T2), improves larval performance compared to the standard protocol. Prolonged access to enriched live feed likely allows larvae to reach a more advanced developmental stage before relying solely on dry diets, thereby reducing mortality and supporting improved growth.

Keywords: Ballan wrasse, weaning strategies, Artemia enrichment, larval survival, aquaculture

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