Study shows salmon grow bigger with colder temperatures

A study carried out by the Royal Veterinary College (RVC) in London has shown Atlantic salmon incubated at lower temperatures are longer, heavier and more muscular than those incubated at higher temperatures.

With global salmon consumption having more than doubled in the last 15 years, optimising the embryonic development of the fish will increase production yield and meat quality, according to the research.

Study author Neil Stickland explains: “Our results demonstrate that whereas salmon incubated at 10°C hatch earlier, the fish incubated at 5°C show a more sustained period of post-hatch muscle growth and by 21 weeks are significantly longer, heavier and have more muscle fibres than those fish incubated at a higher temperature.

“We also demonstrate that fish raised at 5°C show increased food seeking activity throughout development and that this may explain their sustained growth and muscle development.”

1,200 fertilised Atlantic salmon eggs were obtained from a hatchery in Pitlochry, Scotland. These were divided into two groups: one was kept at 5°C, whilst the other had the temperature gradually raised to 10°C over two days. After hatching, both groups of larvae were kept at 5°C – near the natural ambient temperature for Atlantic salmon.

From each temperature group, measurements were taken at six weeks and 21 weeks after first feeding. At least 20 fish from each group were measured for length and body mass.

Embryos incubated at 10°C hatched 45 days after fertilisation, whereas embryos incubated at 5°C hatched 98 days after fertilisation (Higher temperature embryos hatched twice as fast as those at 5°C).

The average mass of the fish incubated at 10°C was significantly greater than those incubated at 5°C at six weeks after first feeding.

However, at 21 weeks, the average mass of the fish incubated at colder temperatures was significantly heavier (After 21 weeks average wet mass of salmon incubated at 5°C was over 60% greater than salmon incubated at 10°C) in addition to being significantly longer (After 21 weeks average length of salmon incubated at 5°C was over 30% greater than salmon incubated at 10°C).