At an average of 4000 calories per fish stored, this is when the coastal brown bears really put on the weight, eating from 10 to 50 fish/day
When do the bears begin to eat the salmon?
The answer to this is easy, but not exact. It's as soon as they can! Bears seem to have an uncanny knack for knowing when the salmon begin to run and will show up within a few days, often congregating at shallow spots along the creek where it is easier for them to catch the fish. Depending on the geographic location in either Katmai or Lake Clark National Parks, salmon may be available as early as late June or as late as August-September in other areas.
How many salmon does a bear eat a day? Do they eat the whole
The short answer to both questions is it depends. How many salmon they eat depends how many they can catch, and how large of a bear they are. If the salmon are numerous and each bear can catch the number of salmon they want, they will catch somewhere between 10 and 20 a day, but large males have been seen catching and eating as many as 50.
Each salmon is roughly worth 4,000 calories in entirety, and 20,000 calories ingested a day is common. In the height of a salmon run, bears are estimated to gain from 2 to 4.5 lbs in fat a day. That’s very important for that winter hibernation period. If the salmon numbers are high, and the bear is skilled at catching fish (something they get better at with age), bears are known to switch to just eating the fatty parts of the fish. Fat has twice the calories of protein, so it's possible to see a bear just eat the brains, the skin, and the eggs if it's a female salmon. They may lay that carcass down and then go get another. Although you may consider that wasteful, nature won't allow it and the red mass of protein will be utilized later by less skilled bears, cubs, or even other species such as bald eagles, gulls, magpies, or even other fish like the dolly varden that follow the salmon.
This large bear is skinning the just caught salmon. When the fish are really running in large numbers some good fishing bears may only eat the skin, roe (eggs), and brains. The rest does not go to waste however, and the waste is quickly devoured by less skilled fishing bears and/or eagles and trout waiting near by.