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Chesapeake Bay News

Archives: January 2007


Virginia Spat-on-shell Experiments Hold Promise for Bay's Oyster Population

It is no secret that Chesapeake Bay oysters are in trouble. Years of over-harvesting, disease and poor water quality have decimated populations to the point where their numbers are just one percent of historic levels.

Over the years several different methods have been developed to assist in the rehabilitation of the oyster population. While many of these methods have been successful, recent experiments performed by the Virginia Institute of Marine Sciences (VIMS), Virginia Marine Resources Commission (VMRC) and Virginia's oyster industry demonstrate that “spat-on-shell” oyster production may become a viable and effective process for growing healthy and harvestable oysters in Virginia waters.

The University of Maryland Center for Environmental Science (UMCES) has been utilizing spat-on-shell oyster restoration techniques in the Bay since the mid-1960s. Last year, the UMCES facility produced more than 350 million spat-on-shell, of which 325 million were used in Bay restoration. In 2006, the second year of spat-on-shell programs in Virginia, 25 million spat were produced.

In order to reach maturity, spat need to attach to a solid surface. While rocks and other underwater debris are suitable for oyster growth, spat have higher success rates growing upon other oyster shells.

Using carefully engineered aquaculture procedures, spat are cultured in specialized tanks and allowed to “set” onto oyster shells, or cultch. In a few months the spat, numbering about a dozen per shell, will have grown into tiny oysters no larger than a fingernail. The advantages of growing clusters of oysters together rather than raising and planting single cultures are threefold:

  • predation from cownose rays is diminished
  • the oysters are able to be planted at a younger stage of their development
  • and spat-on-shell colonies provide better reef building characteristics.

VIMS, VMRC and volunteers from Virginia's oyster industry placed 18 sets of spat-on-shell oysters in Virginia waters between July and October of 2006. Locations for the sets varied widely, with sites in Pungoteague Creek and the Coan, Piankatank, Rappahannock and Ware rivers. Set sizes also varied from as little as 127,000 to as many as 3.6 million.

Results so far have been promising with survival rates ranging from 17 to 98 percent. While these numbers are heartening, spat-on-shell production projects should not be viewed as the silver bullet that will solve all of the oyster's woes, but they may be able to help the Virginia oyster populations rebound to higher levels. To find out more about oyster restoration in Virginia, please visit: http://www.vims.edu/.

Keywords: oysters

The Art of "Catch and Release" Angling

Angling is one of America's greatest pastimes, and on the Chesapeake Bay it is a borderline religion. Fishing the Bay's waters has existed since man first inhabited the shores of the Chesapeake. Centuries ago, Native Americans in the region used massive weirs to corral fish for easier harvesting. Captain John Smith, the first European to explore the Bay, described his fishing excursions when he wrote, “that abundance of fish, lying so thick with their heads above water, as for want of nets we attempted to catch them with a frying pan.”

Thankfully, technology has allowed us to move away from trying to snag a fish with Captain Smith's old standby skillet, and today the Bay's recreational fishing industry is booming. Last year, in Virginia alone, anglers took an estimated 3.6 million trips, supporting over 9,000 fishing-related jobs and contributing over $823 million to local economies.

While some of these anglers will catch only what they intend to keep and then head back to the dock to tell fish stories, others practice the art of “catch and release.” When done properly, catch and release fishing does no harm to the fisherman's quarry. However, if done improperly, mortality rates of fish can exceed eight percent.

Physical injury and stress are the two main factors influencing the survival of fish that are caught and then released. Hook wounds, mishandling during release and physiological exhaustion from the fight are primarily responsible for mortality rates.

Most mortality from hook wounds occurs when anglers use natural baits. Natural baits tend to be swallowed more frequently (deep hooking) than artificial lures, and the hooks used often puncture vital organs. The use of non-offset circle hooks can drastically reduce deep hooking. According to a Maryland Department of Natural Resources study, deep hooking rates for conventional hooks was 17.2 percent while rates using the non-offset circle hooks was 3.4 percent.

Anglers should handle fish that are to be released with care. Fish are covered in a mucosal film that protects them from parasites and bacteria. When too much of this film is removed, the fish can contract skin infections that can lead to death. Once caught and brought aboard, handling the fish with a wet glove or towel will minimize the amount of protective film that is lost. Fish should not be allowed to flop around or make contact with any surfaces inside the boat. If possible, keep all fish that are to be released in the water while removing the hook and avoid at all costs handling the gills and soft underbelly.

By its very nature, the lure of catch and release fishing is the thrill of fighting a fish to the surface. While this practice is exhilarating to the angler, it can be devastating to the fish. Fighting a fish to the point of its exhaustion contributes dramatically to mortality rates. High water temperatures and low salinity levels also contribute to higher mortality rates among fish that are caught and released. “Playing” the fish should be avoided at all costs and fish should be retrieved using steady, deliberate retrieval techniques. During periods of extreme environmental conditions, catch and release fishing should be minimized.

All responsible anglers should practice proper catch and release techniques. Not only do these techniques help protect fish stocks, but they also present a great opportunity to teach younger anglers stewardship of their natural resources. Employing the practices mentioned above is easy and allows both the fish and the fisherman to come away no more worse for wear.

Keywords: recreation, fishing

Good News, Bad News for the Bay's Crab Population

The blue crab may be the most popular resident in the Chesapeake Bay. Its likeness appears on signs, t-shirts and storefronts throughout the watershed. Moreover, it's the main ingredient in the delectable dish that makes the region famous: crab cakes.

To ensure numbers of this famous crustacean remain healthy, Bay Program partners closely monitor both crab populations, or “crab abundance,” and pressure from fishing.

In 2006, the abundance of adult crabs in the Chesapeake Bay remained well below the restoration goal. According to scientists, the current population of legal-sized crabs is at 57 percent of the Bay Program's 232 million pound “biomass” goal. (Biomass is the quantity of living matter, expressed as a concentration or weight per unit area.) These numbers are estimated through winter dredge and summer trawl surveys. Although not at a historic low, this marks the 10th consecutive year the crab population has been below the restoration goal.

But the news is not all bad for crabs. In 2005, the crab harvest was below 46 percent of the adult population, which conserved 20 percent of the breeding stock. This marks the first time since 1997 that the crab harvest met this management target. If sustained, this level of fishing pressure should conserve enough breeding crabs to lead to a larger abundance in the future. Harvest pressure for 2006 will be estimated once the current winter dredge surveys are complete.

So while the total abundance of blue crabs continues below the restoration goal, there is hope that fishing pressure will remain steady around the management target level in coming years. That could lead to higher crab populations in the coming years, which is good news for crabs and crab lovers everywhere.

Keywords: blue crabs
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