Our present knowledge is still too scarce to predict
what will happen to fishes in a high-CO2 world on both
short and long timescales. On the basis of the available
evidence, high CO2will affect fishes directly through acute,
potentially lethal impacts on vital physiological functions,
and chronic, sublethal impacts on more subtle but still
essential aspects of the life cycle. High CO2levels in water
will also influence fishes indirectly through impacts on the
aquatic environment such as increasing water temperature,
and on ecosystem structure and function. On the timescale
of 100– 200 years, shallow water fishes will incur greater
effects of CO2diffused from the atmosphere, whereas deep
sea species may be affected by high CO2levels, if CO2is
injected into the deep sea to reduce the rapid increase of
atmospheric CO2concentration [Ohsumi, 2004]. Over longer timescales of 500 – 1000 years, the ocean CO2 will
equilibrate with the atmosphere, thereby affecting all marine
biota. Our previous review pointed out that information
about the effects of CO2 on fishes was very limited for
marine species as compared with that for freshwater fishes,
and virtually nothing was known for deep sea species
[Ishimatsu and Kita, 1999]. This is unfortunate because in
recent years CO2ocean sequestration has increasingly been
suggested as a potential mitigation method, and knowledge
about the impacts of CO2
on marine organisms is essential
to discuss the feasibility of this strategy [Seibel and Walsh,
2001, 2003].