Species Description: The bay anchovy, Anchoa mitchilli, is a common and often extremely abundant fish of coastal and inshore waters of the western Atlantic. It is gray with a short head, very short snout, and a narrow silvery stripe about as wide as the pupil of the eye, running along the sides of the body. The dorsal fin is set far back on the body, just above or slightly in front of the insertion point for the anal fin. Ray counts are: dorsal = 14-16; anal = 24-30; pectoral = 11-12 (Hoese and Moore 1977, Robbins et al. 1986).
Potentially Misidentified Species: Bay anchovies are similar in appearance to two other common Anchoa species that co-occur throughout much of Florida. The striped anchovy (Anchoa hepsetus) often grows to be somewhat larger (to 15 cm) than the bay anchovy, and both it and the Cuban anchovy (A. cubana) have a dorsal fin that begins well in front of the anal fin. Bay anchovies are the only U.S. anchovies in which the dorsal fin begins at a point right above or only very slightly in front of where the anal fin begins (Robbins et al. 1986).
Regional Occurrence: Bay anchovies occur from the Gulf of Maine and Cape Cod, MA, south to Yucatan, Mexico, and throughout the Gulf of Mexico (Hoese and Moore 1977, Fives et al. 1986, Robbins et al. 1986).
IRL Distribution: Bay anchovies occur throughout the IRL system.
Age, Size, Lifespan: Bay anchovies typically grow to around 10 cm length (Robbins et al. 1986).
Abundance: Bay anchovies are often seasonal numerical dominants in areas in which they occur. Castillo-Rivera et al. (1994) report A. mitchilli accounted for 55% of all fish caught in an ichthyofaunal study of Pueblo Viejo Lagoon, Veracruz, Mexico. Peak abundance in this study occurred during September and October with a general increase in abundance during the wet season. Szedlmayer and Able (1996) note that bay anchovies accounted for more than half of all fish caught in their study of a southern New Jersey estuary fish community.
Rilling and Houde (1999) state that A. mitchilli is the most abundant fish in Chesapeake Bay.
Reproduction: Anchoa mitchilli is a a pelagic, serial spawner (Luo and Musick 1991, Zastrow et al. 1991). Szedlmayer and Able (1996) report that the species spawns both within estuaries and offshore over the continental shelf. Fives et al. (1986) suggest that individuals become sexually mature once they exceed 40 mm SL.
Field surveys by Rilling and Houde (1999) revealed that bay anchovy spawning in Chesapeake Bay occurred from May through September and peaked during July in the seaward third of the bay. The authors estimate that baywide daily egg production increased from 4.25 x 1012 in June to 8.43 X 1012 in July. Olney (1983) reports that 99% of fish egg catches and 67-88% of larval catches during this period are bay anchovies. During peak spawning, pelagic egg densities range from 10-1,000/m3 and larval densities reach 1-100/m3 (Olney 1983, Dalton 1987).
In the southern portion of its geographic distribution, spawning appears to occur year-round (Houde and Lovdal 1984).
Embryology: Larval duration in bay anchovies from the Newport River Estuary, NC, is around 45 days, at which time individuals of approximately 22.5 mm complete metamorphosis. Rapid larval growth rates likely allow animals spawned early in the season (May to early June) to mature and spawn by late summer or early fall of the same year (Fives et al. 1986).
Jordan et al. (2000) reports that Anchoa mitchilli larval growth rates are spatially and temporally variable, averaging 0.39-0.88 mm/day over two seasons of field investigation in the mid-Hudson River Estuary. The authors postulate that small-scale zooplankton patchiness, not salinity or temperature differences, governed growth rate variation.
Temperature: The species exhibits a tolerance for a broad range of temperatures, as evidenced by its distribution extending from Cape Cod south to Yucatan, Mexico.
Gunter (1947) indicates larger individuals (> 27 mm) are significantly more susceptible to lethal low temperatures.
Salinity: Bay anchovies display a tolerance to a fairly wide range of salinities. A coastal Texas field survey by Gelwick et al. (2001) reveals the species is typically found at salinities above 15 ppt in this environment. In contrast, Rozas and Hackney (1984) report that bay anchovies are a dominant member of the fish community of North Carolina low salinity intertidal creeks where salinity is often regularly 5 ppt or less. Felley (1987) reports that bay anchovies are found at salinities approaching freshwater in coastal Louisiana bayous. Individuals are occasionally parasitized by the glochidia larvae of the freshwater unionid mussel Glebula rotundata, suggesting individuals may spend time in low salinity waters (Parker et al. 1984).
Simmons (1957) reports that bay anchovies have been collected in hypersaline environments at salinities of up to 75-80 ppt.
Dissolved Oxygen: Bay anchovies are highly intolerant of low oxygen conditions, and they are usually among the first animals to asphyxiate when they are captured in seine and trawl nets.
Gelwick et al. (2001) encountered bay anchovies at dissolved oxygen levels ranging from 7-10 mg/L. Laboratory observations by Breitburg (1994) indicate larval bay anchovies actively avoided hypoxic (< 1 mg/L DO) areas which are lethal to individuals within 24 hours.
Trophic Mode: Bay anchovies are primarily zooplanktivorous DeLancey (1989) listed brachyuran crustacean megalopae (larvae), copepods, and mysids as the most important prey items recovered from the guts of A. mitchilli collected from a South Carolina beach surf zone.
Predators: Bay anchovies are a major component in the diets of several species of piscivorous fish, including commercially important species such as weakfish (Cynoscion regalis), and striped bass (Morone saxatilis) (Baird and Ulanowicz 1989). Chain Pickerel (Esox niger) have also been reported as predators of bay anchovies (Meyers and Muncy 1962).
Safina and Burger (1989) indicate bay anchovies are one of two prey fish species most preyed upon by predatory fish and terns near Fire Island Inlet, NY. Bluefish (Pomatomus saltatrix) were identified as a major consumer of bay anchovies by these authors, and appear capable of altering anchovy population numbers through predation. McGinnis and Emslie (2001) report North Carolina royal Terns (Sterna maxima) and sandwich terns (S. sandvicensis) both prey on bay anchovies.
A strong association between bay anchovies and the Atlantic brief squid (Lolliguncula brevis) in a study by Ogburn-Matthews and Allen (1993) is likely reflective of a strong predator-prey relationship between these species. Gelatinous predators such as sea nettles (Chrysaora quinquecirrha) and ctenophores (e.g., Mnemiopsis leidyi) are known to consume bay anchovy eggs (Breitburg et al. 1997, Rilling and Houde 1999).
Habitats: Anchoa mitchilli is primarily a pelagic (water colum) species, a habitat preference that is consistent with the zooplanktivorous dietary habits of the species. Individuals are encountered over seagrass beds and unvegetated benthic areas (Orth and Heck 1980). Castellanos and Rozas (2001) collected more individuals over bare substrata than over vegetated areas. Bay anchovies occur in protected waters and tide pools as well as in beach surf zones (Crabtree and Dean 1982, DeLancey 1989).
Activity Time: Castillo-Rivera et al. (1994) captured significantly more bay anchovies in nighttime collections and suggested the nocturnal activity pattern might be a predator avoidance strategy.
Special Status: None.
Able KW, Nemerson DM, Bush R, and P Light. 2001. Spatial variation in Delaware Bay marsh creek fish assemblages. Estuaries 24:441-452.
Baird D and RE Ulanowicz. 1989. The seasonal dynamics of the Chesapeake Bay ecosystem. Ecological Monographs 59: 329-364.
Breitburg DL. 1994. Behavioral response of fish larvae to low dissolved oxygen concentrations in a stratified water column. Marine Biology 120:615-625.
Breitburg DL, Loher T, Pacey CA, and A Gerstein. 1997. Varying effects of low dissolved oxygen on trophic interactions in an estuarine food web. Ecological Monographs 67:489-507.
Castellanos DL and LP Rozas. 2001. Nekton use of submerged aquatic vegetation, marsh, and shallow unvegetated bottom in the Atchafalaya River Delta, a Louisiana tidal freshwater ecosystem. Estuaries 24:184-197.
Castillo-Rivera M, Moreno G, and R Iniestra. 1994. Spatial, seasonal, and diel variation in abundance of the bay anchovy, Anchoa mitchilli (Teleostei: Engraulidae), in a tropical coastal lagoon of Mexico. The Southwestern Naturalist 39:263-268.
Crabtree RE and JM Dean. 1982. The structure of two South Carolina estuarine tide pool fish assemblages. Estuaries 5:2-9.
Dalton PD. 1987. Ecology of bay anchovy, Anchoa mitchilli, eggs and larvae in the mid-Chesapeake Bay. Unpublished Masters Thesis, University of Maryland, College Park, Maryland.
DeLancey LB. 1989. Trophic relationship in the surf zone during the summer at Folly Beach, South Carolina. Journal of Coastal Research 5:477-488.
Felley JD. 1983. Nekton assemblages of three tributaries to the Calcasieu Estuary, Louisiana. Estuaries 10:321-329.
Fives JM, Warlen SM, and DE Hoss. 1986. Aging and growth of larval bay anchovy, Anchoa mitchilli, from the Newport River Estuary, North Carolina. Estuaries 9:362-367.
Gelwick FP, Akin S, Arrington DA, and KO Winemiller. 2001. Fish assemblage structure in relation to environmental variation in a Texas Gulf coastal wetland. Estuaries 24:285-296.
Gunter G. 1947. Differential rate of death for large and small fishes caused by hard cold waves. Science, New Series 106, No. 2759:472.
Hoese HD and RH Moore. 1977. Fishes of the Gulf of Mexico. Texas, Louisiana, and Adjacent Waters. Texas A&M University Press, College Station TX. 327 p.
Houde SD and JA Lovdal. 1984. Seasonality of occurrence, foods and food preferences of ichthyoplankton in Biscayne Bay, Florida. Estuarine Coastal Shelf Science 18:403-419.
Jordan RC, Gospodarek AM, Schultz ET, Cowen RK, and K Lwiza. 2000. Spatial and temporal growth rate variation of bay anchovy (Anchoa mitchilli) larvae in the mid Hudson River Estuary. Estuaries 23:683-689.
Luo J and JA Musick. 1991. Reproductive biology of the bay anchovy in Chesapeake Bay. Transactions of the American Fisheries Society 120:701-710.
McGinnis TW and SD Emslie. 2001. The foraging ecology of royal and sandwich terns in North Carolina, USA. Waterbirds: The International Journal of Waterbird Biology 24:361-370.
Meyers CD and RJ Muncy. 1962. Summer food and growth of chain pickerel, Esox niger, in brackish waters of the Severn River, Maryland. Chesapeake Science 3:125-128.
Ogburn-Matthews MV and DM Allen. 1993. Interactions among some dominant estuarine nekton species. Estuaries 16:840-850.
Olney JE. 1983. Eggs and early larvae of the bay anchovy, Anchoa mitchilli, and the weakfish, Cynoscion regalis, in lower Chesapeake Bay with notes on associated ichthyoplankton. Estuaries 6:20-35.
Orth RJ and KL Heck Jr. 1980. Structural components of eelgrass (Zostera marina) meadows in the Lower Chesapeake Bay: Fishes. Estuaries 3:278-288.
Parker RS, Hackney CT, and MF Vidrine. 1984. Ecology and reproductive strategy of a South Louisiana freshwater mussel, Glebula rotundata (Lamarck) (Unionidae:Lampsilini). Freshwater Invertebrate Biology 3:53-58.
Rilling GC and ED Houde. 1999. Regional and temporal variability in distribution and abundance of bay anchovy (Anchoa mitchilli) eggs, larvae, and adult biomass in the Chesapeake Bay. Estuaries 22:1096-1109.
Robins CR, Ray GC, and J Douglas. 1986. A Field Guide to Atlantic Coast Fishes. The Peterson Field Guide Series. Houghton Mifflin Co., Boston. 354 p.
Rozas LP and CT Hackney. 1984. Use of oligohaline marshes by fishes and macrofaunal crustaceans in North Carolina. Estuaries 7:213-224.
Safina C and J Burger. Population interactions among free-living bluefish and prey fish in an ocean environment. Oecologia 79:91-95.
Simmons EG. 1957. An ecological survey of the upper Laguna Madre of Texas. Publications of the Institute for Marine Science, University of Texas 4:156-200.
Szedlmayer ST and KW Able. 1996. Patterns of seasonal availability and habitat use by fishes and decapod crustaceans in a southern New Jersey estuary. Estuaries 19:697-709.
Zastrow CE, Houde ED, and LG Morin. 1991. Spawning, fecundity, hatch-date frequency and young-of-the-year growth of bay anchovy, Anchoa mitchilli in mid-Chesapeake Bay. Marine Ecology Progress Series 73:161-171.