Acronym NA
Category
Aquaculture
Title Identification of environmental signals that regulate smoltification and maturation in farmed salmon: A functional basis for reducing dieback and early sexual maturation Programme National Programme
Instrument (FP6)
Contact Type (FP7)
Strand (Interreg)
NA
Theme (FP7)
Activity Area (FP6)
Regional Area (Interreg)
Action (COST)
NA
Specific Programme (FP7)
NA
Funding source National Coordinator Kjetil Hodne Coordinator email kjetil.hodne@nmbu.no
Coordinator institution
NMBU - Norwegian University of Life Sciences (Norway)
Institutions involved
CIGENE - Centre for Integrative Genetics (Norway) ,
NA - Lerøy Norway Seafoods AS (Norway) ,
NA - Lerøy Vest AS (Norway) ,
NA - MOWI ASA (Norway) ,
Start year 2020 End year 2022 Funding (€) € 1,101,135 Website https://www.fhf.no/prosjekter/prosjektbasen/901590/ Summary "Optimal growth in the marine phase requires optimal smoltification in salmon. Unfortunately, it turns out that up to 20% of the fish released into the sea have a significantly reduced growth. These fish are often called loser fish. In addition to reduced growth, the taperfish has major problems with osmoregulation in seawater. This results in significant financial losses and, in addition, a huge welfare problem for the fish.
This project provides insights into how different production protocols can influence smoltification and sexual maturation, two critical phases in the salmon's life cycle..
Main goal:
To find methods that can effectively activate the brain-pituitary-thyroid axis and thus eliminate so-called loser fish when transferred to sea. An additional goal is to find optimal conditions that reduce or inhibit early sexual maturation by manipulating photoperiod.
Sub-goals:
• To characterize physiological parameters of taper fish with a focus on the thyroid system.
• To establish new methodological tools using knockout salmon to investigate smoltification and maturation.
• To understand how melatonin/photoperiod manipulation regulates cellular processes in the pituitary gland.
• To understand how changes in photoperiod and temperature affect smoltification and sexual maturation in salmon.
In the study, experiments were conducted to monitor various fish groups through smoltification and up to sea transfer. Some of these experiments were organized as full-scale field trials, where fish from the same population were subjected to different photoperiod regimes. The project also explored the use of various light spectra to prevent early maturation. Furthermore, knockout studies were conducted, and the pituitary cell structure was mapped based on single-cell mRNA sequencing.
The main findings include:
• Even with the synchronization of the population's development after a 5-week winter signal, the variation in endocrine status towards smoltification increases. This variation in endocrine status does not necessarily correlate with typical smolt parameters that measure the composition of different subunits of the sodium-potassium ATPase (nka). This can pose challenges for the optimal transfer of smolt to the sea.
• Tank experiments indicate that a 7-week winter signal with a light intensity of at least 0.15 μmol/m 2 /s at the tank bottom provides a robust smoltification signal, where the population remains synchronized even after the winter signal, up to the fully developed smolt.
• After transferring smolt from full-scale production to the sea, a subgroup of fish with reduced growth, termed 'losers', was identified. These fish had reduced thyroxine levels and reduced expression of a previously little-studied nka variant, nkaα3, in the gills.
• Dark periods after smoltification might help reduce sexual maturation. The use of light with a higher proportion of blue spectrum can also minimize sexual maturation, but the effect varies depending on light intensity and timing.
• A significant increase in plasma levels of 11-ketotestosterone (11-KT) was observed in male fish in the post-smolt phase where the water had a salinity level of 14 ppt, suggesting that this salinity level might not be sufficient to prevent sexual maturation.
• Intriguing findings were also made regarding the relationship between thyroxine (T4) and triiodothyronine (T3) throughout smoltification, as well as potential interactions between Tsh and gonadotropic cells regulating sexual maturation.
These findings offer valuable information on how environmental parameters like light and temperature can influence smoltification and sexual maturation. However, it is essential to emphasize that these results require further investigation to confirm their full implications and to develop robust, industrial solutions."
Keywords
Fish biology;
Land-based aquaculture;
Fish;
Salmon;
Open sea aquaculture;
Cage aquaculture;
Marine Region
76
Not associated to marine areas
0
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