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Early and abrupt salinity reduction impacts European eel larval culture.
E Syropoulou1,2, E Benini1, S R Sørensen1,3
1Technical University of Denmark, National Institute of Aquatic Resources, Kgs. Lyngby, Denmark.
Fish Physiology and Biochemistry
|February 14, 2022
Summary
Reducing water salinity improves European eel (Anguilla anguilla) larval growth and survival. However, the optimal timing for salinity reduction is crucial to avoid negative side effects like pericardial edema.
Area of Science:
- Aquaculture and Ichthyology
- Fish Physiology and Molecular Biology
- Marine Biology
Background:
- Reducing water salinity to iso-osmotic levels is a common strategy in euryhaline fish farming to minimize osmoregulation costs and boost growth.
- The European eel (Anguilla anguilla) is a commercially important species, and optimizing its larval culture is of significant interest.
Purpose of the Study:
- To investigate the impacts of abrupt salinity reduction timing on European eel larvae.
- To assess the effects on morphological and molecular parameters, including growth, survival, and gene expression.
Main Methods:
- European eel larvae from three parental crosses were reared at 36 psu or subjected to a direct reduction to 18 psu at 1, 2, or 3 days post-hatch.
- Growth, survival, and the expression of growth-related genes (igf2, igf1) and stress-related genes (hsp70, hsp90) were analyzed.
- Water-transport-related aquaporin gene expression (aqp1, aqp3) was also examined to understand family-specific responses.
Main Results:
- Salinity reduction generally enhanced growth and survival, linked to more efficient energy utilization.
- Insulin-like growth factor 1 (igf1) expression increased in salinity-reduced groups, suggesting it as a potential growth biomarker.
- While stress indicators (hsp70, hsp90) were not upregulated, indicating low stress, pericardial edema was observed in all salinity-reduced treatments, irrespective of timing.
- Family-specific differences in aquaporin gene expression indicated varied capacities to cope with salinity changes.
Conclusions:
- Abrupt salinity reduction positively influences early growth and survival in European eel larvae.
- The timing of salinity reduction is critical, as it can induce malformations like pericardial edema.
- Further research is needed to establish an optimal protocol for salinity reduction at a precise developmental stage to maximize benefits while avoiding adverse effects in eel larval culture.
