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How feeding period and diet influence salmon egg production

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By Milthon Lujan

Feeding of breeders and manipulation of ovulation timing. Source: Fjelldal et al., (2024); Aquaculture.
Feeding of breeders and manipulation of ovulation timing. Source: Fjelldal et al., (2024); Aquaculture.

The Atlantic salmon (Salmo salar), a commercially important fish species, faces seasonal changes in its natural habitat that regulate its development and reproduction. Fortunately, we can manipulate its environment to optimize egg production in aquaculture.

Scientists from the Institute of Marine Research (IMR), Nofima, Mowi Feed, AquaGen AS, and Benchmark Genetics Norway AS examined how the feeding period with breeder diet (9 vs. 17 months) interacted with the manipulation of ovulation timing (early (November), normal (December), late (February)) on the egg production capacity of breeders and egg quality in Atlantic salmon females in the sea-winter (∼12 kg).

The study delves into two key factors influencing this process: breeder diet duration and ovulation timing manipulation.

What is known in salmon reproduction?

Currently, there has been progress in fully manipulating salmon reproduction. The main strategies are presented below:

  • Environmental manipulation: By mimicking natural changes in day length and temperature, we can control ovulation timing in farmed salmon. This allows for flexible production programs, boosting overall salmon production.
  • Nutritional optimization: Specialized breeder diets rich in marine ingredients and micronutrients improve egg quality. However, replacing these ingredients with sustainable alternatives requires further research.
  • Feeding period: While the optimal duration of the feeding period for breeder diets is unknown, research suggests it affects egg production and nutrient deposition.
  • Ovulation timing: Manipulating ovulation timing can affect egg quality. Early ovulation might hinder optimal nutrient deposition, while delayed ovulation may increase muscular degradation in breeders, affecting egg composition.
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What the new study proposes

The study investigates the combined effect of feeding period and ovulation timing on egg quality, and explores the potential of using plant-based alternatives in breeder diets while maintaining quality.

Scientists highlight that understanding these factors can optimize egg production. Furthermore, improving egg quality leads to healthier fry and a continuous supply of quality smolt to the salmon industry.

Diet and timing: a balancing act

While manipulating photoperiod and temperature can control ovulation timing, the ideal feeding period with a specialized breeder diet remains unexplored. The research addressed this gap by investigating the combined impact of these factors on egg production and quality in Atlantic salmon.

Key findings:

The feeding duration (9 vs. 17 months) had no significant effect on egg production. This suggests a 9-month feeding period may be sufficient, making production more cost-effective and sustainable.

Manipulating ovulation timing affected egg quality:

  • Early ovulation resulted in smaller eggs with higher swelling rates but lower survival rates.
  • Late ovulation resulted in larger eggs but increased mortality from fertilization to first feeding.
  • Overall, manipulated ovulation reduced egg quality without affecting egg count.

Benefits for the salmon industry

Research results suggest that a 9-month breeder diet is sufficient for Atlantic salmon egg production, promoting economic and environmental sustainability.

They also emphasize that manipulating ovulation timing may have negative consequences for egg quality and potentially for fish welfare.

Finally, scientists highlight that further research is needed to explore even shorter feeding periods and address potential welfare issues with late ovulation manipulation. This study adds to efforts to control salmon reproduction, including avoiding early puberty in salmon, embryonic development timeline, among other topics.

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Future research

Based on research results, the following research lines are opened:

  • Identifying the optimal feeding period for breeder diets to maximize egg production and quality.
  • Understanding the long-term impacts of ovulation timing manipulation on breeder and offspring health.
  • Developing alternative and sustainable ingredients for breeder diets while maintaining optimal egg quality.

Conclusion

“According to the biological results reported here, the feeding period with breeder diet can be set at 9 months, making Atlantic salmon egg production less costly and perhaps more sustainable due to lower marine resource consumption,” concluded the scientists.

By understanding and manipulating environmental factors and diet, we can ensure optimal egg production in farmed salmon while promoting sustainable practices. This research has significant implications for the future of salmon aquaculture, contributing to its economic and environmental viability.

The study has been funded by the Fisheries and Aquaculture Industry Research Fund (FHF), Mowi, Benchmark Genetics, Aquagen, Nofima, and IMR.

Contact
Per Gunnar Fjelldal
Institute of Marine Research (IMR), Matre Research Station, Matre 5, 5984 Matredal, Norway.
Email: pergf@hi.no

Reference (open access)
Fjelldal, P. G., Adam, A. C., Berge, G. M., Lein, I., Hevrøy, E. M., Næve, I., … & Hamre, K. (2024). Spawning manipulation, broodfish diet feeding and egg production in farmed Atlantic salmon. Aquaculture, 580, 740227.