Consequently, significant gains could be obtained by selective breeding of diploid oysters. Several quantitative genetics studies have suggested that significant heritable variation exists for traits of aquaculture interest in oysters, such as disease resistance and growth. Triploid oysters have become increasingly important, as they yield better production performance than their natural diploid counterparts, mainly as a consequence of their high level of infertility. To date, the most significant genetic advance for the production of this species resulted from the development of polyploids. I think we'll have better luck this year.Temperature, pathogens and physiological imbalances linked to summer mortalities Field tests of the Morest Pacific oyster families took place in the Marennes-Oléron Bay and two other sites in France.ĭespite its growing economic importance, aquaculture production of Pacific oysters ( Crassostrea gigas) has not benefited much from genetic improvement. We had back luck this year, but it has been a great learning experience. "Everybody I talked to said they would like to do it again. "There's still a lot of interest within Stoney Creek," Ricci said. The state has no plans to cancel the program in any of the four Pasadena waterways that participated this year, Judy said. Many participating in the spat program are looking forward to giving it another shot this fall. The oysters were continuing to grow and survive in the river, which is what we need."Ī fully grown oyster can filter up to 50 gallons of water a day. "I thought 90 percent would have died, but they hadn't.
"We were thinking of the worst, but I was pleasantly surprised that the oysters we recovered in April were doing surprisingly well and surviving," Spadaro said. An Earth Day dive revealed a relatively healthy population and several "very large" oysters on existing reefs, he said. President of the Magothy River Association. Oysters also must deal with predators, such as worms and crabs.ĭespite the high mortality of oyster spat, oysters on reefs in the Magothy survived "surprisingly well," said Paul Spadaro, Caretakers must provide occasional maintenance on the cages to shake sand and sediment off the oysters. Stoney Creek had 20 cages and a total for Bodkin Creek wasn't available, though eight are hanging from a marina at Bodkin Point.įor people who participate in the program, the duties are simple.Ĭages must be kept in 4 feet of water or hung from docks or piers. Ninety cages were placed in Rock Creek, Wallis said. There were 600 cages placed in the Magothy River last fall, Treff said. The cages and spat are given to participants for free, on the condition the oysters will be taken to reefs after they have grown. The initial cost to the state is about $30 per cage, including materials, labor and spat, Judy said. "Mother nature really put the nail in the coffin," Treff said.Ĭages are built using prison labor and the spat are taken from a University of Maryland hatchery on the Eastern Shore. Readings in the Magothy River in late fall revealed salinity rates at or below four parts-per-thousand. Oysters typically need salinity rates above four parts-per-thousand to survive, though six parts-per-thousand or Coupled with the opening of the Conowingo Dam, a mass of fresh water flowed into waterways north of the Bay Bridge. Hurricane Irene dropped heavy rain on Maryland in late August and Tropical Storm Lee added more rain shortly thereafter. The plan was to recover the oysters next month and place them on reefs, where they would filter local waterways.įor Judy, the die-offs were discouraging. Under the program, the Department of Natural Resources in September gave participants spat and cages to hang from their piers, in which larval oysters were supposed to grow. Heavy rains in late August and September made the water too fresh for many spat to survive. Spat, larva that settles and begins to develop a shell, need water with a certain salinity - typically at least four
In in the four-year history of the program, this is the first time we've had such an event, so it was very unusual." "It's a very serious situation," said Chris Judy, manager of the Marylanders Grow Oysters program. In some areas all the spat planted were wiped out. (AP) - As oyster growers prepare to harvest their maturing spat in the coming weeks, things are not looking good.Īn unusually rainy fall lowered salinity levels in Pasadena creeks and rivers, apparently causing massive die-offs among young oysters planted as part of the state's efforts to reinvigorate the oyster population of the Chesapeake Bay.