In this issue:
Shad Restoration
by Libby Campbell, BTW Educator, Alice Ferguson Foundation
Of all the service projects available to Washington, D.C. area students, probably the wettest and most adventurous is the shad restoration project run by the Interstate Commission on the Potomac River Basin, the ICPRB. In late April and early May students go out onto the Potomac River in boats to catch male and female shad, remove roe (eggs) and milt (sperm), and return the fish safely to the river. The roe and sperm are combined, and the fertilized eggs are kept in aquaria in classrooms until they hatch. The tiny fish are then returned to the river to complete their life cycle. Information about this project can be found on the ICPRB website at <http://www.potomacriver.org/shadrestoration.htm>.
Shad are anadromous fish, meaning they live most of their life in saltwater, returning for a few months in the spring to freshwater in order to breed. In the 17th century the shad were so abundant that their numbers choked every freshwater stream on the Atlantic coast. Each female deposits from 60,000 to 150,000 eggs, which hatch in 6 to 10 days. The young fish grow rapidly through the spring and summer, gradually moving from fresh to brackish water as they develop. By fall they migrate out into the ocean, where they join the adults to range the coast in huge schools until they mature, which takes 3 to 5 years.
The American shad, Alosa sapidissima, is the largest, best known, and most delicious of the herring family, which also includes menhaden and alewives. Consequently the American shad has been intensively fished for its bony but succulent flesh and the Chesapeake delicacy, shad roe. So important has this fish been as a food source that a shrub, Amelanchier sp, which blooms each year at the same time as the arrival of the spawning shad, is commonly called the shad bush, and has been used by fishermen for centuries to announce the spring fishing season.
Shad, like all herring, have large silvery scales the reflect light to dazzle daytime predators. These scales are deciduous, so that if a predator does grab a fish, the victim may escape by leaving a few scales in the predator's mouth. The belly of a herring tapers to a sharp keel, casting a sharper shadow than a more rounded fish, thus making them less visible to predators from below*. A mature adult shad weighs about 4 pounds, and is two feet long.
Shad are sensitive to many environmental factors. They prefer water of 13° to 18° Celsius, and key their seasonal movements to these temperatures. They need a neutral pH and will not tolerate acidity. There must be sufficient dissolved oxygen in the water, and plankton (microscopic plants and animals) as food for developing hatchlings. Even more importantly the adults must be able to reach their spawning grounds, which are believed to be where they were themselves hatched. If there are barriers erected such as dams, or if they are intensively fished before spawning, the shad will not be able to reproduce.
Humans have impacted the spawning waters of shad by development and pollution. However it is most likely that the largest factor in the decline of shad (estimated in 1980 to be less than 1 % of historic populations) is simply overfishing. As early as the mid-19th century, shad fish hatcheries were established to attempt to restore the species. Today this effort is continued by state government bans on commercial fishing of shad, habitat restoration projects, and restocking efforts such as the ICPRB program.
The decline of shad, as well as many other fish species, is a worldwide problem. This spring a conference is being held in Baltimore, MD, on the status and conservation of shads across the globe. (See web site <http://www.cqs.washington.edu/~hinrich/shad/shad2001/shad2001.html> for more information.) If you are interested in a lot more information about the American shad, look at the web site <http://www.chesapeakebay.net/info/american_shad.cfm> hosted by the Chesapeake Bay Program.
The shad restoration project is a hands-on opportunity for students to make a difference in their environment as they learn the interconnectedness of humans and Nature. By becoming a part of the project students "take ownership" and make a commitment to preservation of the species. This can create a lifelong interest in preserving the environment.
* Fish: An Enthusiast's Guide, by Peter B. Moyle, p. 77.
|
|
