Changing ocean conditions have long been known to cause variability in abundance of wild fish stocks. With current conditions changing in ways not previously seen in historical times, more variability of wild fish stocks and ecosystems is to be expected.
Brad Warren, of Sustainable Fisheries Partnership, recently called attention to a paper documenting how Atlantic herring larvae react to higher CO2 concentrations in sea water. Higher oceanic CO2 concentrations are one of the consequences of more CO2 in the atmosphere, and mixed with water they form carbonic acid, and are responsible for increasingly acidic sea water.
Warren says ‘to my knowledge, this is the first paper with ‘strong indications that a commercially important fish is directly, physiological vulnerable to elevated CO2. ‘
The paper, by A. Franke and C. Clemmesen of the Leibniz-Institute of Marine Sciences in Germany, examined larval survival of Atlantic herring as they were exposed to higher concentrations of CO2.
They found a strong correlation between higher CO2 levels and poorer nutrition and growth. The effect doesn't kick in until the more extreme CO2 levels are reached, which Warren says our levels that have only been recorded in a few locations in the surface and nearshore ocean so far.
The impact is not on the hatch rate or size or health of the larvae who have normal yolk sacs at all concentrations tested. The impact is no subsequent growth. At the higher CO2 levels, a marked decline in health and consequently larval survival was predicted, based on analysis of overall health of the larvae.
The suggestion is that elevated CO2 will be another stress factor that depresses survival for Atlantic herring larvae, and as a result, the acidification of ocean waters in the major herring spawning areas should be closely monitored.
Republished with permission from Seafood News