An Adult Bay Scallop Can Pump As Much As 15.5 Quarts of Water Per Hour
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secretive bivalve that spends shells. Its upper valve is a dark most of its short life hiding in mottled color, occasionally grasses, the bay bright yellow or orange, and its scallop is a prized dinner entree lower valve is typically white. for many Floridians and an Bay scallops may reach a shell important component of the height of two inches and live two marine ecosystem. Although bay years, although in Florida their scallops historically were a valu- Underwater Canaries life span is generally only one able seafood commodity, declin- year. ing populations in many coastal areas of FI~rida The bay scallop feeds continuously by "vac- have prompted restrictions that now allow only uuming" or filtering small particles of algae and recreational harvests. Scallops are highly sensi- organic matter from the water. It does this by tive to changes in water quality and therefore are funneling water over open pathways called an accurate barometer of an ecosystem's h! lth. One of these pathways takes in water and just as coal miners used canaries to detect an- off particles, while another expels the ing oxygen levels or the presence of dang rous water along with digestive wastes. gases, the bay scallop provides an early-wanning Scallops open their valves when feeding or system for scientists monitoring the quality of Florida's coastal waters. I Description ti ;'"" The bay scallop is a member of the shellfish am- An adult bay scallop can pump as much as 15.5 quarts of water per hour. ily known as bivalves-for its two valve$, or Scallop art after Pete Carmichael photo; used with permission. 2gb 8reathing and close them when predators ductive organs is influenced by the amount of approach. The shell can also be slammed shut to food available and the surrounding water tem- avoid silt, which can clog the animal's delicate perature. If too little food is present, the scallop gills. Many tiny blue eyes arrayed along the outer will direct all its energy toward survival and will rim of the shell detect movement near the animal forego reproduction. and serve as a warning system. When threat- A change in water temperature may trigger ened, the scallop can swim backwards by clap- spawning. In Florida, spawning occurs in the fall ping its valves and expelling water rapidly. Gen- when the temperature drops, although elsewhere erally, most people eat only the large adductor in their range, bay scallops typically spawn ear- muscle of the scallop. Scientists advise against lier in the year when the temperature rises. Each eating the other parts unless the scallop is har- scallop is capable of producing millions of eggs vested from approved shellfishing waters, at once, but the mortality rate is extremely high. because these viscera may contain waterborne Only one egg out of 12 million may survive to contaminants that can cause illness. adulthood. In about 36 hours, the fertilized eggs become LifeHistory tiny larvae that float in the water for about 14 A bay scallop has the remarkable ability to days before attaching to the base of seagrass develop both male and female sexual organs; blades. At this time, larvae are transformed into consequently, the scallop produces both eggs juvenile scallops, commonly called spat. The and sperm. An interval occurs between the spat gradually move up the seagrass blades, out " release of sperm and eggs so that self-fertiliza- .of the reach of bottom-dwelling predators such ",,;,ion is unlikely to occur; this interval helps to a"scrabs. But even then, survival is uncertain. As ",. prevent inbreeding. Development of the repro- many as 90% of the spat will die within six ,.. , Adult Bay Scallop Argopecten irradians Juvenile Scallop 5-7 cm 5-20 mm 180-365 days 60-120 days I t D-shaped Veliger 0.1 mm Spat 36-48hrs 1-5 mm ~ Newly Settled Spat Art after N. ]. Blake '*' (Univ. S. Fla. Dep. Mar. Sci.) 3~O days 0.3mm .and]. S. Gutsell (1930). 14-20 days 29c weeks of latching on to seagrasses. Those that believe poor water quality is responsible do grow large enough to avoid consumptioln by these declines. Currently, the most extensive bay predators will eventually drop off and fall t<l>the scallop populations are located north and west bottom, where they will remain the rest of ~heir of the Suwannee River, particularly near the fish- lives. ing hamlet of Steinhatchee and in St. Joseph Bay. Even as adults, scallops live a precatious Once a population is depleted, it may not be existence. A variety of marine creatures, includ- able to recover on its own, even with improved ing blue crabs, stone crabs, and whelks, arel able water quality and restrictions on harvest. Scal- to pry the scallop shells open and extract the lops are broadcast spawners, sequentially tender meat within. Sometimes the scallop can releasing eggs and sperm to maximize fertiliza- escape this fate by swimming away. Occasional- tion by other scallops. If no other scallops are ly, the algae, tunicates, and other organisms that nearby, reproduction may not be successful. attach to scallop shells may conceal them from Consequently, a depleted scallop population predators-although this is not a reliabl1 de- may have to rely on neighboring populations to fense. c replenish its losses. fishing Regulations* Researchers frequently find the outside of stone Restrictions enacted to enhance the natural crab burrows littered with broken scallop shells. recovery of scallop populations have been placed on scallop harvesting. No commercial harvest of bay scallops is allowed anywhere in the state One creature, the pea crab, manages to live in and recreational catches are now limited. ~ harmony with the bay scallop; this little crab Before the restrictions were adopted, te~ finds protection within the scallop's shells. Whiile phone surveys of scallopers and aerial surveys of the pea crab does steal some food from the 'sc,al- popular harvesting areas were conducted by the lop, it doesn't take enough to jeopardiz~ 1:he Florida Department of Environmental Protec- health of its host. tion's Florida Marine Research Institute. Those Bay scallops are very sensitive to changes in surveys revealed that the intense fishing pressure temperature and salinity. They are also vulnera- placed on already depleted scallop populations ble to changes in water quality. Water made hindered natural recovery of some stocks. As a cloudy by floating particles and sedi~ents, result, all scalloping areas south of the Suwan- referred to as turbidity, can clog the scallop's nee River, including Homosassa and Crystal gills. The scallop can close its shell to protect rivers, were closed, and scalloping north of the these gills for short periods but is unable to shut out the dirty water for more than abou~ two Aerial surveys of the Homosassa and Crystal ~~r::~;toBay Scallops ~. rivers at the start of the scallop season showed the presence of 600 to 800 boats per weekend, Bay scallops were once plentiful throughout each carrying an average of four people. Florida's west coast but have virtually disap- peared in some areas. An extensive scallop, fi:sh- ery existed in Tampa Bay as recently a~ the I 960s, but scallops are rarely found therei now. Charlotte Harbor also supported a comm!erl:ial scallop fishery some 30 years ago. Scientists 29d Suwannee was restricted to the period from July lops in laboratories and releasing juveniles into through September 10th. the wild. Tampa Bay was selected for this project In areas where scalloping is permitted in July because researchers believe water quality there and August. each person is limited to a maxi- has improved enough to again support bay scal- mum of 2 gallons of whole scallops. or I pint of lops. scallop meat per day. A boatload of five or more In the laboratory, scientists are experiment- people can take no more than 10 gallons of ing with a variety of materials that mimic the whole scallops or 4 pints of scallop meat per day. natural seagrass meadows scallops require dur- These regulations. which took effect in 1995. will ing their development. In fact, scallops have be reevaluated in 1998 (unless modified in the already been successfully reared on artificial turf interim) to determine how effective they are at like that used on football fields. When they are protecting scallop populations. transplanted in the wild, the juvenile scallops are All scallopers operating from a boat must often placed in protective cages-dubbed "scal- have a valid saltwater fishing license from the lop condos" by one researcher. The cages help state. People who gather scallops by wading into shield them from predators until they are large shallow areas at low tide do not need a license. enough to spawn. Although the scallops die soon but they cannot use dive masks or snorkels ,to after spawning, it is hoped that the eggs they help them find the scallops. release will survive in the wild and eventually Researchers have suggested the sale of a spe- replenish the local area. cial "scallop stamp." which could be affixed to In Tampa Bay, citizens help assess the suc- fishing licenses. Information derived from suth cess of the transplants by participating in "The sales would provide researchers with valuable Great Bay Scallop Search." During this one-day information on the extent and locations of scal- event, teams of snorkelers swim along defined lop harvests. transects in the bay's seagrass beds and search ' j !m" Research 'i'!!:1i~ for scallops hidden among the thick grass car- pets. Although few adult scallops have been Scientists at the Florida Marine Research Insti- found by the volunteers so far, this event pro- tute conduct a variety of studies to assess scal- vides valuable baseline information with which lop populations and to learn more about their to compare the ultimate success of restocking environmental needs.