Our traditional seaside treat may be under threat if the much-loved cod can’t handle a rise in seawater temperature. The effects of climate change on animals and plants are common topics of discussion; in particular the economic implications of a possible decrease in fish stocks. With an increase in temperature, cold-water dwelling fish may find a future rise in temperatures a struggle. Cod prosper in cold water and are therefore a perfect test subject when investigating the impact of rising temperatures on fish.
A new study conducted at the National Institute of Aquatic Research in Denmark fitted more than 2000 cod from eight different North Atlantic fish stocks with advanced temperature gauges. The mini thermometers recorded the temperature of the water surrounding the fish once an hour over a one-year period, in order to determine the temperature of the water in the Northeast Atlantic that the cod are frequenting.
“It’s absolutely unique to have data from such a large and comprehensive study,” says Professor Ken Haste Andersen, one of four DTU Aqua researchers who participated in the project. Since the fish were tagged, over 900 have been caught and the data from the gadgets analysed.
“Some fish were found at temperatures as cold as -1.5 degrees [Celsius], while others swam quite happily in water that was nearly 20 degrees above zero. This shows that cod are relatively adaptable fish that can tolerate higher temperatures than was previously thought,” says Professor Anderson. “However, while this is true for adult cod, they appear to be somewhat more conservative in their choice of water temperature when they spawn. During this period, all the fish stocks studied consistently sought out water that had a temperature of between one and eight degrees.”
The study’s findings demonstrate that cod are more adaptable than previously believed. The authors suggest, though, that the narrow temperature range that the cod prefer for spawning may be the biggest issue when it comes to increasing temperatures and the struggle may be constrained to the larval stage of the cod’s life if they are unable to survive about eight degrees.
Image courtesy of Patrick Gijsbers (http://www.allemaal-beestjes.nl/cpg145/index.php) via Wikimedia Commons.
Righton, D., Andersen, K., Neat, F., Thorsteinsson, V., Steingrund, P., Svedäng, H., Michalsen, K., Hinrichsen, H., Bendall, V., Neuenfeldt, S., Wright, P., Jonsson, P., Huse, G., van der Kooij, J., Mosegaard, H., Hüssy, K., & Metcalfe, J. (2010). Thermal niche of Atlantic cod Gadus morhua: limits, tolerance and optima Marine Ecology Progress Series, 420, 1-13 DOI: 10.3354/meps08889
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Neat paper! It sounds like in many marine species, the juveniles are most at risk from a changing environment. Did they report on the spatial extent of these temperature limits? For example, do cod manage the temperature at spawning by migrating to deeper waters or to different locales at similar depths?