Anchoa mitchilli

Anchoa mitchilli
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Clupeiformes
Family:	Engraulidae
Genus:	Anchoa
Species:	A. mitchilli
Binomial name
Anchoa mitchilli (Linnaeus, 1758)

Anchoa mitchilli is a species of fish in the Engraulidae family. It also commonly goes by the name "Bay anchovy."

Etymology

The word Anchoa comes from the Spanish word anchova meaning "herring-like" or a herring like fish. The species name Mitchilli was named in honor of Dr. Samuel L. Mitchill, a New York senator and American naturalist who wrote several documents on North American fishes.

Description

The Anchoa mitchilli or "Bay Anchovy" is a small, slender, schooling fish with a greenish body and a silvery stripe that runs along the body. It is characterized by its very long jaw, silvery belly, lateral stripe, and single dorsal fin. The dorsal fin is located directly above the anal fin origin. The dorsal fin contains 12 to 14 rays and the anal fin contains 24 to 27 rays. Bay anchovies can grow up to a total length of 100 mm (4 inches). They are considered the smallest anchovy species occurring in South Carolina.

Habitat and biology

The bay anchovy is the most abundant and important species native to the Chesapeake Bay. Bay anchovies, as other members of the family Engraulidae, typically aggregate in large schools. Schooling occurs in deep waters during winter and moves into the shallows in warmer months. The bay anchovy is also widely tolerant of salinity and temperature. Specific habitat features, structure, and shoreline development are not particular concern for bay anchovy, but hydrographic features that affect water quality could limit its distribution and abundance. They feed mostly on zooplankton. They are planktivorous fish which use gill rakers—comb-like structures on their gill arches—to strain the water for food. Bay anchovies can live up until the age of three but usually live around the age of two.

Reproduction

Bay anchovies spawn from spring through late summer, once water temperatures reach at least 54 degrees. The peak of spawning occurs in July (late spring) and summer when low dissolved oxygen (DO) may limit the distribution of all life stages. Oxygen levels below 3.0 mgl-1 can be lethal to eggs and larvae and DO below 2.0 mgl-1 is critical. In South Carolina, spawning occurs in the evening during the summer months. Eggs are pelagic, and larvae hatch within 24 hours. Growth in this species is rapid, especially at higher temperatures, with a fish reaching maturity a few months after hatching.

Predation

Bay anchovies are an important source of food for predatory fish, including the sea trout, southern flounder, striped bass, bluefish, and weakfish. Although the species itself has no recreational or commercial value, it fulfills a crucial role in the coastal food web.

Anchoa mitchelli vs Anchoa hepsetus

Compared to the co- occurring and larger striped anchovy, Anchoa hepsetus, the bay anchovy has a shorter snout and the silvery stripe on the side of the body is less distinct. Bay anchovies are characterized by a single dorsal fin, a silvery head and lateral stripe, silvery belly and a very long jaw. The larger striped anchovy has a more distinct lateral stripe and longer snout (longer than eye diameter). Bay anchovies (and other anchovy species) are similar in appearance to fishes of the herring family (Clupeidae). However, they can be distinguished by a prominent silver stripe on either side of the body and lack of scutes (bony scales) along their bellies. Bay anchovies are of a greenish color above and silvery below and have a single dorsal fin, which is located midway along the body. They are often confused with silversides (Menidia spp.), but the two can be easily distinguished—anchovies lack a spine in the dorsal fin and have a large, gaping mouth that extends almost to the edge of the opercle, whereas silversides have two distinct dorsal fins, the first with four spines, and a very small mouth that is tilted upwards.

Decline

Bay anchovy populations in the Chesapeake Bay fluctuate annually, however the Maryland Department of Natural Resources Juvenile Finfish Seining Survey indicates the bay anchovy has suffered from poor recruitment in recent years. Bay anchovy numbers have shown a dramatic decline since 1994 in Maryland's portion of the Chesapeake Bay and its tributaries documenting the first long-term decline ever recorded for the species. The 1997 Juvenile Finfish Seining Survey Index for bay anchovy is the lowest on record.

In the past few years bay anchovies have been the prevalent forage fish in the Buzzard's bay area of Massachusetts. Clouds of them are seen on any bottom with structure throughout the summer months. Previously Menhaden were the prevalent forage fish but have been scarce recently and the void seems to be filled by the smaller bay anchovy.

References

Chesapeake Bay Program. Bay Field Guide. Bay Anchovy Anchoa mitchilli http://www.chesapeakebay.net/bfg_bayanchovy.aspx?menuitem=32815

Bay Anchovy Data. Anchoa mitchilli Chesapeake Bay Ecological Foundation, Inc. 2011 http://www.chesbay.org/forageFish/anchovy.asp Bay Anchovy "Anchovy mitchilli" Maryland Department of Natural Resources http://www.dnr.state.md.us/bay/cblife/fish/bay_anchovy.html