Life cycle study of Atlantic salmon with temperature and salinity as critical test variables

Webinar

Background

Optimal conditions during the various developmental stages in freshwater is the key to producing salmon that is robust when it is transferred to the sea. 

Today, a number of different production regimes are used by smolt producers. These are often primarily developed with capacity, efficiency and economy in mind, driven by an increased need for reduced production time in the sea, with less focus on fish health and welfare as a consequence. 

While hatchery producers are producing fry at a rapid pace to accommodate market needs, mortality during the hatchery phase increased in the period 2011 to 2019. 

This has generated greater attention towards lifecycle studies where the relationship between the conditions during the hatchery stage are linked to later performance in the sea and until slaughter, and towards gaining insights into whether hatchery production has become too intensive. 

Both flow-through and RAS facilities are used in commercial hatchery production. RAS technology enables farming under even more controlled conditions, and may involve more intensive production. 

Furthermore, the use of key input factors such as temperature and fish density, photoperiods and salinity have changed in recent years. Increased awareness of the use of these input factors throughout the hatchery stage may contribute to the production of robust fish that perform better throughout the course of the sea phase. 

In the Temp-Intens project, we have chosen to focus on temperature and salinity as key test variables. 

We will also perform economic analyses and study the relationship between the costs of the various stages of the production cycle and the implication of this on the total production cost per kg of salmon produced.

Goal

Temp-Intens’ main objective is to provide recommendations for commercial production of salmon through optimization of temperature and salinity. 

These critical test variables will be tested under different farming conditions in the hatchery stage, and the fish will be monitored all the way until they are slaughtered, in order to assess performance, health, welfare and product quality.

Sub goals

• Document whether fish farmed intensively using recirculation technology (RAS) or flow-through technology (FT) perform differently. 
• Assess the production intensity at water temperatures of 8, 12 and 14 °C and whether different temperatures affect the robustness of salmon in the long term.
• Investigate whether the fish’s performance depends on whether they are farmed under stable conditions, with a constant low or high temperature, or whether variation in temperature promotes robustness.
• Investigate whether gradual adaptation to salinity before being released into the sea makes the salmon better able to tolerate the transfer as opposed to going directly from freshwater to seawater.
• Calculate the economic profitability of intensive farming in the hatchery phase from hatchery to slaughter. 

The Lakseliv blog

In addition to disseminating our research in the form of meetings, conferences and publications, we have also created a blog with regular updates from the experiment with information about biological performance and project activities.

Read the blog (Norwegian language)

What we do

During the Temp-Intens project we will conduct a lifecycle experiment where we monitor the fish from 10 grams until it reaches slaughter size. The trial involves four temperature groups with four replicates. 

Roe from SalmoBreed and the same production batch are incubated at a raw-water temperature of around 7.5 to 7.8 degrees, i.e. below 8 degrees. All groups are initially fed at 10°C in a flow-through setting (FT) before being sorted and placed at the temperatures for groups 1–4 respectively, from a weight of 10 grams, either in a flow-through or RAS system (16 RAS tanks + 16 FT tanks): 

• Group 1: Constant temp @ 8°C 
• Group 2: Constant temp @ 12°C 
• Group 3: Constant temp @ 14°C 
• Group 4: Constant temp @ 8°C until termination of the 6-week winter signal (12L:12D), followed by a gradual increase in temperature up to 12°C. 

Around 21 days before the fish is transferred to net pens, the groups are divided in two and exposed to a salinity increase from 0 ppt to: 

• A) 32 ppt for approx. 21 days before transfer to net pen 
• B) Gradual increase to 15 ppt for 7d, 25 ppt for 7d, 32 ppt for 7d before transfer to net pen 

Established protocols for salinity increase in RAS will be followed. 

The trial will be closely monitored with frequent sample extraction. In addition to a number of response variables linked to health, welfare and performance we will also extract samples after slaughter to examine quality. We will also follow up closely with X-rays to detect any deformities and cases of nephrocalciosis. 

We will model how capital and operating costs for both hatchery and edible fish production are affected by the choice of critical test variables in hatchery production, and how this affects the sales value. The latter depends, among other things, on mortality, slaughter weight, quality and the price achieved. 

Bioeconomic models will be applied to analyse different scenarios and strategies based on data from the experiments in the project, financial data from related companies, the Directorate of Fisheries’ profitability surveys, our own research and other literature.