This video from California in the USA says about itself:
9 July 2015
Just very close and shallow to the shore of the Torrey Pines Cliffs, with the depth of between 150 and 200 feet, the blue whale had so many black specks all over its body! It also had a dorsal fin that had been torn off and shaped like a sickle! It is very unusual for a blue whale to have very many barnacles.
From Science News:
Barnacles track whale migration
Chemical composition of hitchhikers’ shells might reveal ancient baleen travel routes
By Thomas Sumner
12:01pm, September 27, 2016
DENVER — Barnacles can tell a whale of a tale. Chemical clues inside barnacles that hitched rides on baleen whales millions of years ago could divulge ancient whale migration routes, new research suggests.
Modern baleen whales migrate thousands of kilometers annually between breeding and feeding grounds, but almost nothing is known about how these epic journeys have changed over time. Scientists can glean where an aquatic animal has lived based on its teeth. The mix of oxygen isotopes embedded inside newly formed tooth material depends on the region and local temperature, with more oxygen-18 used near the poles than near the equator. That oxygen provides a timeline of the animal’s travels. Baleen whales don’t have teeth, though. So paleobiologists Larry Taylor and Seth Finnegan, both of the University of California, Berkeley, looked at something else growing on whales: barnacles. Like teeth, barnacle shells take in oxygen as they grow.
Patterns of oxygen isotopes in layers of barnacle shells collected from modern beached whales matched known whale migration routes, Taylor said September 25 at the Geological Society of America’s annual meeting. Five-million-year-old barnacle fossils have analogous oxygen isotope changes, preliminary results suggest. Converting those changes into migration maps, however, will require reconstructing how oxygen isotopes were distributed long ago, Taylor said.
Scientists have quantified how barnacles infest stony coral over a variety of conditions and reduce calcium carbonate on reefs. Coral reefs harbor diverse marine life and help prevent coastal erosion: here.