Oyster situation ‘stressed"

            A newly released state report on the oyster harvesting situation in Apalachicola Bay shows that the drought is beginning to take its toll on the population at the same time that a record number of oyster licenses have been issued to work the bay.

            "The situation is stressed right now but it's not dire," said Mark Berrigan, chief of the bureau of aquaculture development, for the state department of agriculture and consumer services. "It may be dire by the end of the winter harvesting season."

            The oyster resource assessment report summarizes surveys conducted by the Division of Aquaculture during 2006 through 2008, and finds that "the abundance of juvenile, sub-legal, and market-size oysters suggest that the overall condition of many reefs has declined over the past two years.

            "The outlook for oyster production for the 2008/2009 winter harvesting season in St. George Sound (Cat Point, East Hole, Porters Bar and Platform) is not promising, but may not be as dire as previously projected," reads the report. "However, it is unlikely that reefs in St. George Sound could sustain concentrated harvesting effort for the remainder of the winter harvesting season."

            The report uses productivity of greater than 400 bags per acre as an indicator of healthy oyster reefs capable of sustaining commercial harvesting. Experts find that oyster populations are capable of supporting limited commercial harvesting when stocks exceed 200 bags per acre, and are considered depleted when marketable stocks are below 100 bags per acre.

            While production estimates from Cat Point, East Hole and Dry Bars exceeded 400 bags per acre on sampling intervals prior to the opening of the winter harvesting season over the past two years, the estimated oyster population on Cat Point Bar and East Hole Bar during 2007 and 2008 did not indicate strong production trends, contends the report.

            "Stable or declining population estimates on Cat Point and East Hole Bars over the past two years generally indicated that oyster populations were stressed, most likely from factors associated with higher salinity regimes," said the report, referring to the effect of the drought on the level of saltwater in the estuary.

Lull in fishing effort helps Cat Point rebound

            The report said estimates of production for Cat Point Bar declined from 514 bags per acre in August 2007 to 478 bags per acre in Jan. 2008 and 381 bags per acre in Sept. 2008. Oyster density also declined from 264 to 123 oysters per square meter during the same sampling intervals.

            But because of what the report called "unusually low harvesting effort" on Cat Point and East Hole Bars at the beginning of this year's winter harvesting season, the numbers of available oysters appear to have swelled.

            "Estimated production, of 784 bags per acre, has rebounded on Cat Point Bar since September, probably as a result of limited fishing effort during the first two months of the winter harvesting season," said the report.

            The fact that no one had fished on them has allowed some of the smaller oysters there to grow to market size," said Berrigan. "There are oysters there. They're not necessarily plentiful there but they can catch enough right now to make a living. But how long that will last I don't know.

            The experts said data over the past three years indicates oyster abundances and potential production are slowing due to declines in what it called "recruitment, survival and growth.

            "Negative trends in population dynamics are likely associated with higher salinity regimes, which in turn contributed to alterations in the food web and higher natural mortality," it said.

            "What we're seeing now is the realization of a prediction we had made that essentially two years after the beginning of a drought or so we begin to see problems," said Berrigan. "We're quite confident these are drought-related problems."

            He said that while oysters initially "do quite well under high salinity conditions," their reproductive success is affected over the longer term.

            "You don't get the number of recruits and they don't survive well, but typically these droughts don't last that long and they can be masked," said Berrigan. "The data for eight months is still not clear as to exactly what we're finding out there, but we're beginning to tend to a stressful situation.

            "The lack of freshwater is a primary contributor to environmental quality out there and once the environmental quality changes several things happen," he said. "The environment becomes more marine, which allows for establishment of marine predators such as boring sponges, whelks, drills and stone crabs.

            "This changes the food web so that the phytoplankton is changed (and it is a question) whether or not there is adequate nourishment for young oysters to grow," Berrigan said. "Also disease is a summer stress situation, and certainly we have had that problem of losing oysters during the summer."

            "When you combine all these things, there is stress on environmental quality and it causes stresses on these animals and it eventually take its toll," he said.

Higher salinity leading to greater predation

            The report states clearly that predation of young oysters has increased due to the higher salinity in the bay. "A successful spat settlement was recorded in the spring of 2008, but the positive effect of recruitment to the larger size classes was absent, suggesting an extensive mortality among spat and juvenile oysters," it reads. "Observations by divers indicate that increased predation is contributing substantially to mortality among spat and juvenile oysters.

            "Stone crab burrows (on Cat Point Bar) have been estimated to be as high as one burrow per square meter in areas where stone crabs are concentrated," reads the report. "The presence and abundance of stone crabs can be associated with higher salinity regimes which allow predators with marine affinities to become established within the estuary.

            The report notes that while Dry Bar and other eastern bars traditionally have been subject to the most harvesting pressure, reefs in the western portion of the bay and the "Miles" and St. Vincent Sound areas are expected to continue to support harvesting at moderate levels.

            "The impacts of high salinity are less severe on the western reefs than on the eastern reefs. The prevailing circulation patterns move freshwater from the Apalachicola River westward over Dry Bar and St. Vincent Bar, and into the Miles, mitigating somewhat the impacts of prolonged high salinity conditions," reads the report.

            With no increase in production expected, "any change can be expected to be a reduction in standing stocks and production as harvest continues. If demand holds, there remains a likelihood that oyster resources could be stretched by the end of the winter harvesting season," said the report.

            "The recent closures of oyster harvesting areas in Louisiana and Texas as a result of Hurricane Ike placed additional pressure on the productive reefs in Apalachicola Bay to meet the early season demand," it notes. "This concentrated harvesting effort could lead to reduced stocks at the end of the harvesting season."

Landings last year highest since 2002

            The report notes that since 1980, reported landings in Florida have ranged from about 1 million to 6.5 million pounds of meats, with the highest landings were reported in the early 1980s. Annual dockside values for oysters from Apalachicola Bay have ranged from about $1 million to $5 million dollars since 1980.

            Last year, reported oyster landings from Apalachicola Bay were about 2.65 million pounds of meat, continuing a trend of increased landings since 2002 (See chart).

\           "During this period landings appeared to be correlated with resource availability and fishing pressure, and were dependent upon market demand," said the report.

            In 2007, oystermen reported 29,104 trips and the number of Apalachicola Bay Oyster Harvesting Licenses reached 1,142, the highest number of licenses sold since the license was created. (See chart).

            Berrigan said that oysters typically adjust well to oscillations in the natural conditions and oyster mortality should be seen in the context of the larger cycles.

            But, he said, two factors are troubling, market demand and the persistent drought. "Market demand is certainly off," he said. "Shellfish, oysters, are really reflective of the economy. We see this all the time, most half shell oysters are eaten at restaurants and the restaurant business drops off in a hurry during tough economic times."

            The second fear is that the ebb and flow of the natural cycles may not be as foreseeable as they once were, due to increased development and water use upriver.

             "The scary reality is that these things typically end in a natural way because of a flood or something like that because the bay is renewed because of flooding in the drainage basin," said Berrigan. "But if they have to fill up that entire (basin) before water gets into Apalachicola Bay the full cycle may not be a possibility.

            "That's the scary part," he said. "The natural cycle may now be interpreted to a point that it's not reinvigorated."