Uhmm Humpback whales are a type of baleen whales, which don’t eat fish per se. They eat mostly krill, which is a very small shrimp type animal. And on occasion, they do eat small fish. They have a baleen which is a type of netting within the mouth to strain the krill from the seawater.
Humpbacks feed primarily in summer and live off fat reserves during winter.[112] They feed only rarely and opportunistically in their wintering waters. The humpback is an energetic hunter, taking krill and small schooling fish such as juvenile Atlantic and Pacific salmon, herring, capelin and American sand lance, as well as Atlantic mackerel, pollock and haddock in the North Atlantic.[113][114][115] They have been documented opportunistically feeding near fish hatcheries in Southeast Alaska, feasting on salmon fry released from the hatcheries.[116] Krill and copepods are prey species in Australian and Antarctic waters.[117] Humpbacks hunt by direct attack or by stunning prey by hitting the water with pectoral fins or flukes
From Wikipedia
I've been on whale watch cruises. Small fish congregate in what the captain called "bait balls". The whales come up from underneath, open wide, and let the resulting vacuum suck up all the small fish. So yes, they eat krill, but they also eat all manner of small fish. They separate the fish (or krill) from the seawater with their baleen plates, and allow the seawater to leave their enormous mouths.
