Last week, a humpback whale swam into the Hudson River as far north as the George Washington Bridge. Humpbacks have been returning to the waters around New York in significant numbers in recent years, although a whale swimming in the inner harbor is extremely rare. Ninety miles to the east, in the Shinnecock Canal on Long Island, tens of thousands of menhaden, also known as bunker fish, clogged the canal. There were so many fish in the restricted waterway that they used up all the oxygen in the water and died. A clean-up is underway.
In a very real sense, the two events were related.
Why have the humpback whales returned to the waters around New York? There appear to be two primary reasons. First, there are now simply more humpbacks than there were only a few years ago. From a low of only about 700 whales in 1986, the population of North Atlantic humpback whales has made a dramatic recovery and is no longer considered threatened. Efforts nationally and internationally to protect the species have been remarkably successful.
In addition to there being simply more of them, the other reason that the humpbacks have returned is because of the menhaden; a small, oily fish, also called bunker fish, pogey, whitefish,fat-bat and bug-heads. Humpback whales love to eat the young menhaden. And like the humpbacks, the menhaden have returned after have been seriously over-fished.
Menhaden, which rarely grow longer than 15″ long and swim in large schools, play a major role in the coastal environment, providing food for sea bass, dolphins, bluefish, ospreys and eagles, and yes, humpback whales. The menhaden also feed by filtering the water, cleaning it of algae, which can improve water clarity.
So why was the humpback whale swimming up so far into the Hudson River last week? It is likely that it was chasing a school of menhaden up the river. Based on photographs and video of the whale lunge feeding it appears that it had a good meal.