Plainfin Midshipman Fish

Each year, just west of Seattle, Washington, there is a very special event for bird lovers. The plainfin midshipman fish spawns, many within the oyster beds of the Hood Canal, and Bald Eagles come en masse to feast on the fish. How does this happen? Let’s take a dive into the lives of the plain midshipmen to better understand.

Plainfin Midshipman of Big Beef Harbor

Big Beef Harbor, located on the Olympic Peninsula in Washington state, is a well-known spawning ground for plainfin midshipman fish. 

The plainfin midshipman fish, also known as the midshipman toadfish, is a species of fish that belongs to the family Batrachoididae. It is found along the Pacific coast of North America, from Alaska to California. In terms of appearance, the plainfin midshipman fish has a broad head with a large mouth and a protruding lower jaw. Its body is elongated and flattened, with a mottled brown or gray coloration that provides excellent camouflage against rocky coastal habitats. It has a dorsal fin that runs along its entire length, as well as an anal fin and pectoral fins.

The plainfin midshipman fish is a bottom-dwelling predator, feeding on crustaceans, mollusks, and small fish. It is typically found in rocky intertidal zones and nearshore waters, where it hides in crevices and under rocks during the day and emerges at night to hunt for prey. It is an interesting and important member of the Pacific coast's marine ecosystem, with its unique vocalizations and specialized adaptations making it a fascinating subject of study for biologists and ecologists alike.

Plainfin Midshipman Breeding Season

During the breeding season, which typically occurs between May through June, male plainfin midshipman fish establish nests on rocky substrate in shallow water near the shore. These nests are typically located in crevices or under overhangs. Many create their nests in the oyster beds. Once established, the nests are defended aggressively by the males. 

Once a male has established a nest, he will begin attracting females to the site. Female plainfin midshipman fish are known to be attracted to the "drumming" vocalizations produced by the males, as well as the flashing pattern of light produced by their photophores. When the female arrives, the male will court her by circling her and rubbing his body against hers. Once the female is ready to spawn, she will lay her eggs in the depression in the center of the nest, and the male will immediately fertilize them with his sperm.

The female will lay anywhere from a few hundred to several thousand eggs, depending on her size. The eggs are small and adhesive, and will stick to the stones and shells in the nest. The male midshipman will guard the nest and the eggs, fanning them with his fins to ensure that they receive sufficient oxygen.

After fertilization, the male plainfin midshipman fish will guard the nest and care for the eggs until they hatch, which can take up to two months. During this time, the male will not feed and may lose up to 30% of his body weight. Once the eggs hatch and the larvae are released, the male will resume feeding and will eventually regain the weight he lost during the spawning period. Unlike salmon, the plainfin midshipman does not die after spawning. 

The eggs will hatch after about a week, and the larvae will drift out to sea, where they will undergo a period of development before returning to the coast as juvenile midshipman fish. The spawning behavior of the plainfin midshipman fish is a fascinating example of the intricate reproductive strategies that have evolved in marine species, and it is an important aspect of the fish's life cycle.

It’s safe to say that the plainfin midshipman spawning at Big Beef Harbor is a fascinating natural spectacle that attracts researchers and visitors alike. The vocalizations and bioluminescence of the fish, combined with their unique nesting behavior and parental care, make for a truly remarkable natural phenomenon.

Birds of Big Beef Harbor

Several species of birds are known to eat plainfin midshipman fish, particularly those that inhabit coastal areas where the fish are found. Some examples of birds that may prey on midshipman fish include:

• bald eagles
• great blue herons
• ospreys
• cormorants
• and various species of gulls and terns

As the tide goes out each day, the plainfin midshipmen that built their nests in the oyster beds become exposed. Birds and marine life, like otters, feast each day on the fish, providing birders and photographers an amazing day of bird watching. It lasts for weeks, with the height typically falling in late May to early June. 

Bird Bitch offers photography excursions each year to photograph this bird bonanza. Visit our Bird Tours page to see upcoming tours.