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Menhaden

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Menhaden are small, oily-fleshed marine fish belonging to the order Clupeiformes. They are found in two different genera: Brevoortia and Ethmidium. Many people call them "the most important fish in the sea." This is because they act as a keystone species. A keystone species is an organism that holds an entire ecosystem together. Without them, the food web could fall apart. They serve as a vital link between tiny organisms and large predators.

Juvenile menhaden in the Chesapeake Bay, 1959–2019
Juvenile menhaden in the Chesapeake Bay, 1959–2019

These fish are omnivorous filter feeders. They swim in large, slow-moving, and tightly packed schools. To eat, they swim with their mouths open to strain food from the water. They take in materials in the same proportions as they occur in the surrounding water. A menhaden's diet changes as it grows older. Small fish under one year old eat mostly phytoplankton, which are tiny photosynthetic organisms. As they reach adulthood, they switch to eating almost exclusively zooplankton. This process transfers energy from microscopic life to much larger animals.

Juvenile menhaden in the Chesapeake Bay, 1959–2019
Juvenile menhaden in the Chesapeake Bay, 1959–2019

Scientists use DNA comparisons to organize North American menhadens into two main groups. The first group is large-scaled menhaden, which includes the Gulf and Atlantic species. The second group is small-scaled menhaden, which includes the Finescale and Yellowfin species. There are seven distinct species within the two genera. The genus Brevoortia contains species like the Atlantic menhaden and the Brazilian menhaden. The genus Ethmidium includes the Pacific menhaden. These species live in many areas, from estuaries to the continental shelf.

Juvenile menhaden in the Chesapeake Bay, 1959–2019
Juvenile menhaden in the Chesapeake Bay, 1959–2019

Menhaden play a massive role in the health of the ocean. By eating phytoplankton, they help mitigate toxic algal blooms. These blooms can create hypoxic conditions, which are areas with very little oxygen. This can be harmful to many marine species. Menhaden also provide food for many predators. This includes fish like striped bass, tuna, and sharks. It also includes birds like ospreys, pelicans, and herons. They redistribute a significant amount of energy between estuaries and the coastal ocean.

Juvenile menhaden in the Chesapeake Bay, 1959–2019
Juvenile menhaden in the Chesapeake Bay, 1959–2019

Humans use menhaden in several ways, though we do not eat them directly. They are processed into fish meal and fish oil. The oil is high in omega-3 fatty acids. These fats can help lower blood pressure and reduce the chance of heart attacks. This oil is also used in animal feed for chickens and guinea pigs. It is even used as a raw material for making lipstick. There are two main types of commercial fisheries. One is a reduction fishery, and the other is a bait fishery. The total annual harvest is approximately 500 million fish.

Juvenile menhaden in the Chesapeake Bay, 1959–2019
Juvenile menhaden in the Chesapeake Bay, 1959–2019

Overfishing has caused serious problems for menhaden populations. In 2012, the Atlantic States Marine Fisheries Commission declared the Atlantic menhaden were depleted. This was due to overfishing and poor water quality in the Chesapeake Bay. To help, managers have set various harvest caps. For example, a cap in the Chesapeake Bay was set at 51,000 metric tons in 2017. In 2020, a 10% coast-wide harvest cut was approved. This was the first time managers used "ecological reference points." This means they look at the needs of the whole food web, not just the fishing industry.

Juvenile menhaden in the Chesapeake Bay, 1959–2019
Juvenile menhaden in the Chesapeake Bay, 1959–2019

Menhaden also have a deep cultural history. The name comes from an Algonquian word related to using fish as fertilizer. It is believed that Tisquantum, or Squanto, advised Pilgrims to plant menhaden with crops. In the 1870s, menhaden oil became a popular alternative to whale oil. During this time, crews of African-American men worked on open boats. They used purse seines to catch the fish. These crews sang sea chanties to help them pull the nets. These songs came from West African, blues, and gospel traditions. This tradition declined when hydraulic winches replaced manual hauling in the 1950s.

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