The hotter the oven the more dramatic the effect of carryover cooking.
We often talk about carryover cooking in meat—how a roast, for example, will continue to cook even after it’s been removed from the oven, the result of heat migrating from the outer portions of the meat toward the center. This is why we often take a roast out of the oven before it’s fully cooked. But carryover cooking can also have a dramatic effect on fish and its loosely structured flesh.
To quantify the effect of carryover cooking on salmon, we cooked three batches of 1-inch-thick fillets on a wire rack set in a baking sheet at various oven temperatures until they were 125 degrees at the center. We then watched how that number rose as the fish sat outside the oven for 5 minutes. The salmon cooked at 250 degrees carried over an average of 7 degrees, just above the ideal 130 degrees for serving. The salmon cooked at 325 degrees rose 9 degrees at its center after 5 minutes, while the fish cooked at 350 degrees rose 15 degrees. And at 450 degrees? The salmon’s temperature rose a whopping average of 27 degrees after 5 minutes.
Though the extent of carryover cooking will vary depending on the type (and width) of the fish, these tests underscore why a low oven temperature can work best for fish, since the hotter the oven the more dramatic the effect of carryover cooking. A low oven temperature will help ensure that the flesh is evenly cooked from edge to center and stays near the ideal doneness temperature until the fish is served.