Animal Diversity Web

Geographic Range

This species of fish is indigenous to the Alantic coast of the United States, and ranges from Cape Cod to the shores of Florida (Shepherd, 1997). Seasonal migration leads the weakfish in a northern movement along the coast during the spring and then a migration to the warmer waters of the south in the fall. They are most abundant from the coasts of North Carolina to New York (Lowerre-Barbieri, 1996).

• Biogeographic Regions
• atlantic ocean
  • native

Habitat

Weakfish are found along the Atlantic coast. They migrate seasonally in the relatively shallow coastal water of sandy mud bottoms, and then to the brackish water of river estuaries for reproduction and feeding in the summer, finally returning offshore in the fall (Virginia Tech, 1996). During the spawning season, the most important habitat for the weakfish is the brackish waters of the Chesapeake Bay (Lowerre-Barbiere, 1995).

• Aquatic Biomes
• coastal

Physical Description

Weakfish have a length of about 1 meter (Zim, 1955). Weakfish are distinguished from other species in its genus by several meristic characteristics: the anal fin on weakfish have 11 or 12 soft rays, 11 to 13 gill rakers, and the lateral line scales number from 76 to 86. In adult weakfish the coloration of the dorsal scales are dark green fading into a silver underside. The coloration of the sides can range from spots of purple, green, blue, and gold that are generally found on the top half of the fish. The fins are yellowish in color. The basic shape of the weakfish's head is elongated, and it comes to a sharp point. The mouth is large and oblique, with the lower jaw protruding past the upper jaw. The dorsal fin of the weakfish is spiny, but the spines are flexible and usually the third or fourth spine is the longest. The anal fin is comparably smaller to other fish in the same family as the weakfish, with its base ending slightly in advance of the dorsal fin (Virginia Tech, 1996).

In male weakfish, there are extrinsic sonic muscles that extend throughout the body wall, and paired bilaterally at its origin on the trunk hypaxialis muscles. This muscle inserts on an aponeurotic sheet, that covers the dorsal surface of the swim bladder, and the muscles are separated from the lateral region of the body by connective tissue. This muscle is used in producing the 'drumming' or 'croaking' sounds that are possibly used for mating and/or prey calling. In females these muscles are present, but are vestigial (Connaughton, 1995).

• Other Physical Features
• bilateral symmetry

• Range mass

  0 to 0 kg

  0.00 to 0.00 lb

• Average mass

  5 kg

  11.01 lb

Reproduction

The weakfish reproductive biology is not well understood, despite studies on its spawning seasons. Weakfish may be a multiple spawner, which means that it has several mating seasons a year, or weakfish may have an extended spawning season (Lowerre-Barrieri, 1995).

There is some evidence that the male weakfish croaking sounds may be used in attracting a mate and playing a role in spawning behavior. This is because the male's sonic muscles, which are used in producing 'drumming' and 'croaking' sounds, increases three times its usual mass during spawning season (Connaughton, 1995).

Both male and female weakfish become sexually mature when they are roughly 1 to 2 years of age (Lowerre-Bariere, 1995). Weakfish are dioecious, meaning that the male and female reproductive organs are on separate individuals (Virginia Tech, 1996).

Spawning and egg-laying are all done near the shore of estuaries. Weakfish eggs are hard to identify, they have many similarities to other eggs of the sciaenid species that spawn at the same time as weakfish (Virginia Tech, 1996).

Behavior

Weakfish have an acute chemosensory response mechanism. In times of stress, weakfish gather into tighter schools. This was seen in lab studies when higher temperatures were used. The weakfish under these conditions showed a 35% decrease in their distance to the other fish in the school. Also the frequency of school formation increased in response to stress (Virginia Tech, 1996).

• Key Behaviors
• natatorial
• motile

Communication and Perception

• Perception Channels
• tactile
• chemical

Food Habits

During different life stages, the food selected by weakfish varies. In the larval and juvenile stages, weakfish primarily eat copepods, a type of crustacean. Young weakfish also feed on mysid shrimp and anchovies. As adults, weakfish are the top carnivore in the eelgrass habitat of the waters of the Chesapeake Bay. An adult weakfish eats a variety of species, including annelids, mollusks, crustaceans, and other fish (Virginia Tech, 1996). One specific species eaten by weakfish are drums, which are heavy-bodied clams that are abundant in bays and estuaries (Moyle, 1993).

Weakfish are visually oriented animals when it comes to feeding and seeking after prey (Virginia Tech, 1996). In addition, weakfish also mock the calls of their prey, like their chattering call to attract striped cusk eels (Sciaenid Acoustics Research Team, 1997).

When weakfish have a prey in sight, they move towards it slowly. When in close pursuit of prey within 20 to 50 cm, weakfish produce rapid fin movements of the caudal fin, making it lunge at the prey with it jaws open and opercules flared (Virginia Tech, 1996).

Economic Importance for Humans: Positive

Weakfish are important food and gamefish for people along the Atlantic coast. They are also a sport fish and recreational game fish (Zim, 1955).

Economic Importance for Humans: Negative

Unknown

Conservation Status

Weakfish live in the coastal waters of many states. Each state has jurisdiction over 3 nautical miles offshore from their state boundry; this means the state has control of conservation of weakfish in the fisheries in this determined area (Virginia Tech, 1996).

• IUCN Red List

  No special status

• US Federal List

  No special status

• CITES

  No special status

Other Comments

Weakfish have their common name because their jaws tear when caught with hooks. They are one of the best known fish in the Croakers family, scientific name Scianidae (Zim, 1955).

Contributors

Faith Gillum (author), Western Maryland College, Randall L. Morrison (editor), Western Maryland College.

References

Connaughton, M., M. Taylor. 1995. Effects of Exogenous Testosterone on Sonic Muscle Mass in the Weakfish, Cynoscion regalis. General And Comparative Endocrinology, 100: 238-245.

Lowerre-Barbieri, S., M. Chittenden, Jr, L. Barbieri. 1996. The multiple spawning pattern of weakfish in the Chesapeake Bay and Middle Atlantic Bight. Journal of Fish Biology, 48: 1139-1163.

Moyle, P. 1993. Fish: An Enthusiast's Guide. Berkeley: University of California Press.

Sciaenid Acoustics Research Team, Jan 7, 1997. "Weakfish (Cynoscion regalis)" (On-line). Accessed May 1, 2001 at http://personal.ecu.edu/spraguem/fish/cynreg.html.

Shepherd, G. 1997. "Weakfish, Cynoscion regalis" (On-line). Accessed April 30, 2001 at http://www.nefsc.nmfs.gov/fbi/age-man/weak/weaktext.htm.

Virginia Technological University, August 26, 1996. "Marine and Coastal Species Information System: Species weakfish" (On-line). Accessed April 30, 2001 at http://fwie.fw.vt.edu/WWW/macsis/lists/M010401.htm.

Zim, H., H. Shoemaker. 1955. A Golden Guide: Fishes. New York: Golden Press.