Coal and nuclear electricity generation kill a significant number of fish through water intake systems. This matters for evaluating the impact of any new electricity load.
Most thermal power plants (coal, nuclear, and to a lesser extent gas) draw large volumes of water from rivers and lakes for cooling. This causes two underappreciated harms to fish:
Impingement — fish get trapped against water intake filters and die. Entrainment — eggs, larvae, and small fish are pulled through pumps and heat exchangers, killing them. A single coal plant in Ohio (Bay Shore coal plant) killed roughly 46 million fish and 2.2 billion fish eggs and larvae in 2005–06.
Some thermal plants use evaporative cooling while others return the water to the source warmer than it was drawn. This thermal pollution stresses aquatic life in two compounding ways: elevated temperatures reduce dissolved oxygen levels while simultaneously increasing organisms’ metabolic oxygen demand. Even small temperature increases can cause declines in bottom-dwelling species, and organisms in already-warm environments are especially vulnerable.
Impingement and entrainment don’t affect fish population levels because many of them would have died young anyway, other things like pollution have a much greater effect, and “only” ~10% of the wild population died due to the coal plant in the above case of the Ohio Bay Shore coal plant and Maumee River.
It’s also unclear what the net effect on wild-animal suffering is when comparing death in a water intake to death by natural causes. And as electricity generation shifts from thermal plants toward renewables, these specific harms should diminish.
From an EA perspective, this seems worth flagging for anyone working on wild animal welfare or assessing the environmental footprint of new electricity load like compute scaling. The fish mortality numbers are large in absolute terms even if they seem unlikely to cause population-loss, and this externality rarely features in discussions about electricity demand growth.
I could estimate the number of fish, fish eggs, and larvae killed due to thermal plants globally based on the Bay Shore coal plant, but without more information on how representative it is it would feel like false specificity. I feel ~50% sure it’s over 500 billion fish, fish eggs, and larvae globally per year.
This writing was part of a broader piece I wrote on space-based data centres.
To be honest it wasn’t my intention to argue that fish eggs have moral weight—I included them to give a sense of the scale of impact—but I can see how that came across, so apologies.
Fish eggs may more clearly have moral worth under non-utilitarian value systems, such as believing that all life that will eventually be sentient has intrinsic moral worth, or that impacts to nature should be minimised for intrinsic reasons (to be clear I don’t hold these views personally, but maybe having some level of moral uncertainty leads to a non-zero moral weight).
On evidence for fish eggs having moral worth under a utilitarian-ish values system, 1) I don’t know, it’s not my area, but 2) it seems pretty unlikely given fish larvae themselves seem to generally have pretty weak evidence for sentience immediately after hatching.