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To explore the productivity of the coastal estuary ecosystem by researching how fish use estuaries as a spawning ground, nursery, and food source before returning to a freshwater habitat or the open sea.
Research the life cycle of one fish species: Striped Bass, Gaspereau, American Eel, Smelt, or Atlantic Salmon. Investigate when they use the estuary and for what reason. Take on the persona of the fish you study. Participate in an interview with someone posing as a reporter. Tell the reporter about your stop-over visit to the estuary for food and shelter.
Fish are classified according to where they live in the ocean. Cod, flounder, and Halibut feed and live near the bottom of the ocean. They are called Atlantic groundfish. Fish that feed in the surface or middle depth waters are called pelagic. Mackerel, Bluefin Tuna, and Capelin are examples of Atlantic pelagic fish. Fish that migrate from freshwater to the sea and back again for spawning are diadromous fish. Striped Bass, Gaspereau, American Eel, Smelt, and Atlantic Salmon are examples of diadromous fish. One of the most important stop-over sites in a diadromous fish's journey is the estuary.
Gaspereau (Alosa pseudoharengus)
An estuary is a transitional zone between a freshwater river and the open sea. In the estuary, warm shallow water, tides, currents, and wind carry rich organic nutrients from the bottom of the estuary to the water's surface. With every tide these nutrients are carried from the estuary to the sea. This exchange of organic material between the estuary and the ocean creates a very productive habitat for many plants and animals. Food is plentiful and shelter easy to find. In the protected Eelgrass communities of the estuary diadromous fish feed, spawn, and establish nurseries. They also use the estuary as a corridor to travel from saltwater to coastal freshwater rivers. Atlantic Salmon enter estuaries on their way to their spawning grounds upstream. They use the estuary as a transitional zone, to get used to the changes in the level of salinity from sea-water to freshwater. The young salmon use the estuary to feed on small fish and invertebrates before migrating to the sea.
Smelt and Gaspereau leave the sea and migrate through estuaries on their way to freshwater rivers to spawn. The estuary provides a necessary food source on the long distance journey. American Eels do the journey in the opposite direction. They enter estuaries as young fry in July and stay for 5-15 years to feed. When the time is right, they return to the sea to spawn.
Striped Bass reproduce in estuaries. The young stay for a year to feed on small invertebrates and then travel out to sea.
The estuary coastal ecosystem is like a fine restaurant. It has a varied menu to fit all the nutritional requirements of its diadromous guests. The estuary offers not only a popular menu but also comfortable accommodations, a necessary requirement for long distance travellers.
Winter Flounder (Pseudopleuronectus americanus)
* For information on diadromous fish in the estuary use the following resources:
1. By the Sea - A Guide to the Coastal Zone of Atlantic Canada, Module 3: Estuaries.
2. Scott, Atlantic Fishes of Canada
3. Atlantic Coastal Guide to Fishes, Audubon Field Guide
4. Contact your nearest Department of Fisheries and Oceans office for: Underworld Fact Sheets-Atlantic Pelagic and Diadromous Fish, Alewife (Gaspereau), American Eel, American Smelt, Atlantic Salmon.
If you are doing some extension activities, ask for Underworld Fact Sheets-Winter Flounder, American Shad, Turbot.
Name: sample sheet
|MATERIALS:||books and pamphlets on diadromous fish, paper, pen, Diadromous Menu and Accommodations Sheet|
|TIME REQUIRED:||4 hours|
|MINIMUM PEOPLE REQUIRED:||2|
|GRADE LEVEL:||5 and up|
|KEYWORDS:||estuary, Eelgrass, groundfish, pelagic fish, diadromous fish, nutrients, spawn, fish nurseries, Striped Bass, American Eel, Atlantic Salmon, Smelt, Gaspereau, Tomcod, American Shad, Turbot, Smooth Flounder, Winter Flounder, catadromous, anadromous|