Examples of Species Dependent on America's WETLAND
LIFE STORIES OF A FEW COASTAL MARSH DEPENDENT ANIMAL SPECIES
OYSTERS
The most common commercially important species in Crassostrea virginia, but there are several other useful species in our waters. For commercial oyster production, Louisiana waters are second behind Maryland. Louisiana waters now produce 9 million lbs of meat/year ($3-4 million in dockside value).
There are two basic ways that Americans harvest oysters:
1. Harvesting wild oysters. This can be done by hand-picking clutches of oysters growing on the bottom or working a real oyster reef.
2. Seeding. This has traditionally been done by simply leasing the bottom of a body of water, buying a load of shells (usually Rangia clams) and shoveling them overboard all over the bottom, and returning later to harvest those that have grown to maturity. How does this work? Oysters each lay about a zillion (actually "only" 70-170 million) eggs that are spewed into the water column. These are fertilized after they leave the female and begin their larval development as they float about. Soon, their shells begin to grow and, when they become too heavy to float, they sink to the bottom. If they land on a hard surface (clam shells, rocks, another oyster), they cement themselves down and begin to grow; if they land on a soft surface, such as the muddy bottom, they usually die, or at least put more energy into shell growth than into soft tissue, so they are not good for human food!
So the theory is that the water is full of larval oysters, and, by ensuring a hard surface by depositing a shell layer on the bottom, a healthy crop may grow where it never did before.
Things are getting a little tougher for oystermen. Farming today may involve not only placing shells in open water areas, but farmers may have to pick them up once spat have formed and move them to a different salinity in order to get the best growth. In some instances, the farmer may have to move them more than once. This amount of energy going into oyster farming will have two impacts on the product: 1) it should enhance the quality and quantity of the product; 2) it will increase the cost of the product.
There is a lot of research under way attempting to enhance oyster production. The loss of Rangia clam shells for use as a substrate is viewed as a critical loss, and scientists are trying to find alternatives. Two potential solutions include:
1. Gypsum blocks. LSU's Institute for Recyclable Materials is testing blocks made of gypsum as a suitable substrate for the growth of oysters and other marine organisms. Early tests are encouraging, and there are huge mountains of gypsum available just upriver.
2. Reef blocks. These are wire containers filled with oyster shells, designed by Coastal Environments, Inc., in Baton Rouge (having Woody Gagliano as president). Their primary purpose is to use in constructing a breakwater in areas where the edge of the marsh or a bank is being eroded by wave action. The design, however, allows for spat to settle and grow on the oyster shells, thus turning the breakwater into an active oyster reef. An additional benefit is all the life that is attracted to a viable oyster reef - many species of sessile (anchored, not moving) critters, crabs, redfish, speckled trout, and more).
Oysters are filter feeders, having cilia around their gills to move water into their respiratory chambers. As the water passes through, food particles are removed; the average oyster circulates about 150 gallons of water per day through its system.
Since they are filter feeders, oysters are susceptible to accumulating harmful products if pathogens exist in the water. Heath officials are constantly monitoring water and measuring fecal coliform contamination. For the oyster harvest, the harvest line is changed quarterly depending on fecal coliform counts.
As in all critters that produce huge numbers of eggs, only a few oysters survive to reproduce. The magic number is one egg in four million, the rest either dying or, more probably, becoming assimilated into the tissue of a consumer! Sexes are separate, but they can change after spawning - usually from male to female. The oysters become sexually mature in one month at less than one inch long. They usually grow to two inches in the first year.
Spawning is temperature and salinity related and occurs from April to October, with the peak being between June and August. They prefer temperatures above 72°F and salinities above 6 ppt, though they can survive brief periods of freshwater. Although several weeks below 10 ppt is lethal to adults, one population is known to have survived for four weeks in 1 ppt during cold weather. Larvae die below 10 ppt. Permanent colonies are almost always in water ranging 10-40 ppt, but 15-20 ppt seems to be best due to a lack of predators in water of this range.
Some of the most aggressive consumers of oysters (aside from people) are Black Drum (Ponogias cromis), stone crabs (Menippe mereenaris), blue crabs (Callinectes sapidus), and oyster drills (Thais haemastoma). Blue crabs can open live oysters quicker than a shucker at Felix's Restaurant and Oyster Bar! Oyster drills (a type of marine snail) are a special case. People think of snails as slow, innocuous animals. Oyster drills feed on oysters by drilling a hole directly through the oyster's shell, everting their stomach through the hole into the oyster's shell, and digesting the oyster. They drill the hole by using their radula, a rasp-like "tongue" that they methodically move back and forth until the hole is complete. Oyster drills require high salinities and warmer waters. Oyster reefs are generally safe if salinities remain <15 ppt. If salinities increase, the drills invade and can literally wipe out a reef in a matter of weeks.
Oysters may fall prey to parasites such as the protozoan Perkinsis marinus and the Bucephalus trematode.
During the warmer months of summer, oysters are susceptible to oyster fungus. Oystermen used to prepare their beds in spring and allow them to grow for two years. This resulted in 75-90% mortality. Now they work their beds in the fall and harvest them the following June before the fungus arrives. They also are sure to use water areas that are normally below 20 ppt; the fungus needs higher salinities.
Due to the opening of the Bonnet Carré Spillway and high waters from the Pearl River, oyster production in Lake Borgne has dropped by >90%. Not only did the opening of the spillway cause a drop in salinity, but the average temperatures increased, as well. When the introduction of freshwater does not get out-of-hand, there are three possible positive effects from its presence:
1. it controls pathogens
2. it introduces new nutrients
3. it retards salinity encroachment
THE OYSTER LEASE SCAM - A loop-hole that needs to be closed.
People who are professional oystermen normally harvest the bottoms of waterways for which they hold leases. As one would expect, someone leases a piece of habitat that will grow oysters; if it needs enhancing, they do so as economically practicable. If another interest, in the course of doing business, damages the oyster production in the lease, that interest is required to compensate the lessee. An example would be if a pipeline were laid across an open waterway and it removed some of that area from oyster harvest. The pipeline company would be expected to pay a damage fee to the oysterman. The same would be true if a seismic operation took place and a marsh buggy had to roll through the lease (some folks get as much as $1,250 per crossing and $250 per dynamite hole!). I think we would all agree that if the lessee's product is damaged, he/she is entitled to some compensation.
Of course, some folks found a way to turn a justifiable program into a huge profit! A recent seismic operation is a good example. An oil company applied for a permit to search for oil in a section of marsh in a Louisiana coastal parish. "Suddenly," people made application for oyster leases that blanketed the proposed seismic zone (allegedly, there are public servants who share in the wealth by sharing information about proposed oil field work).
When an oyster permit is granted, it applies only to waterways (oysters can't live on land), but, during the application phase, the applicant is granted "protection" for the entire area under consideration, water or not. This little glitch was quickly found and exploited.
The result of our example: The total cost of the seismic operation was just under $1,000,000. The oil company in question paid $290,000 (almost 30% of total cost of the project) in crossing fees (remember, they pay each time they cross a lease) to the lessees. The irony: there were no oysters in the water where the seismic operation took place!!! The law simply says that one must have a lease or application; it does not stipulate that oysters must be present.
By the way, the leases are very cheap, something like $2/ac/yr. You can see that one or two damage settlements can be quite profitable.
Did you, the tax-payer and consumer, enjoy that little glitch? Aren't you glad these glitches remain in the law?
SHRIMP
There are many species, but white, pink, and brown are the best for people to eat. They spawn offshore in spring and summer. White shrimp spawn closest to shore, then pink, then brown. Up to one million eggs are released into the water by each female - they are not carried as they are in crawfish. There are many larval stages. Development occurs in the constant environment of the sea. They gradually wash toward shore in onshore currents (if these are absent, most die). At d in, they begin the "postlarval" stage as they enter the estuaries. At this stage, they are no longer plankton, being capable of their own movement. At 1 in, they are termed "juvenile" and become bottom dwellers. They soon start to move offshore where they breed and the cycle begins again. Most live for one year to 16 months.
Since shrimp gain their nutrition from organic material coming from the marshes, shrimp harvest is directly correlated with available intertidal vegetation.
MENHADEN, or POGY (Brevoortia patronus) (Also called pilchard and mossbunker, but never by a respectable Louisianian!)
This species is euryhaline and (especially as juveniles) very sensitive to oxygen depletion. They are filter feeders, with the typical long gill rakers that "comb out" plankton from the water. Spawning takes place offshore after the first year. Each female may produce 122,000 eggs. The clear, slender larvae (<1.5 in long) enter the estuaries when they are 3-5 weeks old. The body deepens as they mature. In the estuaries, they may be quite abundant in the fresher areas. They move toward the open Gulf as they reach sexual maturity. Their schools reach their peak within 60 mi offshore during the colder months when the season is closed to allow for spawning. The fishery is open from April to mid-October. The fishermen set 1200 ft purse nets and catch a billion pounds per year.
Pogy are very important economically for:
1. oils (foreign) - for oleo production, lubricants.
2. fertilizer - Indians buried them with their crops; we now use them in many types of fertilizers.
3. fish meal that is used as food for poultry, beef, swine, and aquaculture raised fish.
Their predators include all carnivorous fish of the continental shelf and associated estuaries (like Lake Pontchartrain), especially jack cravelle, tarpon, and sharks.
The following story (entitled "The Chicken Bone is Connected to the Marsh Bone") illustrates how elements of the environment and economy are interconnected.
"I live in Montana. Why should I care about Louisiana's coastal erosion?" "I'm a teacher in Ohio. Why should I care?" "Yeah, I'm a car dealer in Helena, Arkansas. It doesn't affect me!"
WRONG! It does affect you, but I'm not surprised that you didn't know. As a matter of fact, few Louisianians have been apprized of their dependence on our coastal wetlands.
Assuming that, if you are reading this, you would be interested in being a member of the "in crowd", let me tell you a story that mixes biology, ecology, and a little economics along the way.
Our story begins with a non-descript fish called a menhaden. Locally, it is most often referred to as a "pogie." If you've never heard of it, maybe you've smelled it. Have you ever noticed that a drive through Pascagoula, Empire, or Cameron may be a genuinely malodorous experience (the locals call it the "smell of Money!")? This is the smell of pogie being changed from being fish to being another very important product, but we'll get to that a little later.
Pogie are small, schooling fish that are about five inches long as adults (the largest are about ten inches) and shiny silver in color. They swim in schools of oodles of millions (that's a "M" word) of fish and they represent the largest single fisheries in the United States. Certainly in tonnage they are Number One. That alone makes them very important, but there's more . . .
Remember what a "food web" is? It is basically a "who eats whom" list with arrows connecting each eater to one or more eatees. Pogie, that tremendously important commercial fisheries crop, eat plankton - tiny little critters and plants that exist as free floating life forms in the water column. On the other hand, pogie are eaten by most flesh eaters of the sea - redfish, trout, sharks, mackerel, tuna, cobia, bluefish, and more. So far I haven't found even a Louisianan who has a good recipe for pogie, but I'm sure someone out there does!
As important as pogie are in the food web of the Gulf, they are most important to humans as the basis for an extensive "economic web." An economic web is a list of all the ways people make money from products with arrows pointing the way between those that affect others (a graphic presentation similar to the food web). The basic part of the pogie economic web is obvious. Pogie fishermen buy boats, nets, gasoline, white rubber boots, clothes, cars, food, electricity, insurance, sunglasses, Dixie beer, brooms, ice, and so forth They hire many people: to dry-dock their boats, to work as deck hands, to haul supplies, etc. And don't forget what all these people and vendors do with the money they get from pogie fishermen - they spend it in many of the same ways!
Now the pogie boat reaches its home base with a load of fish. The fish are rendered into oils and fish meal at a "pogie plant." Most of the oil goes to Europe where it is used in cosmetics, as glazing on pastries, and to make margarine (the FDA won't yet let us produce these products in America). The primary use of the meal is in making chicken (and catfish) food. It must be shipped to another plant (What does the trucker do with his money?), then many other suppliers and handlers are involved to get it to a chicken farm. Now the chicken rancher hires lots of people and spends lots of money to raise chickens. The rancher then ships them to a poultry processing plant (the trucker stops along the way to gas up, eat a burger, play a pinball machine, spend the night in a Motel 6, etc.) where lots of people are employed and lot of businesses receive lots of money for services rendered. Be sure you don't forget all those folks who work at the utility company supplying the electricity to the plant, and the guys at the ice plant, and the preacher at the church where the employees attend, and the person who fills the candy machine, and the people at the Chamber of Commerce, and . . . Do you think this could go on forever?
Now the processed chicken leaves and some goes to a grocery store, some to a restaurant, and some to Popeye's Fried Chicken. Many people now choose chicken as their main protein source because it is relatively cheap, but many others are required for health reasons to eat chicken. What would happen if they had no chicken? Oh, my gosh! Did you realize that we listed Popeye's? Without Popeye's, there would be no Mardi Gras!!! You can't watch a parade without eating fried chicken! The total economy of New Orleans would fail! And to think, it all started with pogie. Or, did it?
We mentioned earlier that pogie feed on plankton, so on what do plankton feed? Most get their energy from nutrients that float in the water. Off Louisiana's coast, these nutrients largely come from organic matter that washes from coastal marshes with each tidal flow. If the marshes did not exist, there would be no food for the pogie to eat. Additionally, pogie (as most other commercially important species from the sea) must spend a portion of their lives in coastal estuaries. Without coastal wetlands, there would be no place for pogie to complete their life cycle.
No marsh, no pogie . . . No marsh, no economic web. How will we replace the economic web if we lose our coastal wetlands?
The next time you have a meal of delicious chicken or pond-raised catfish, remember that you are enjoying the fine taste of processed Louisiana marsh!
THE LOUISIANA ALLIGATOR STORY
Alligators have long been important to Louisianians due to the value of their skins (belts, shoes, boots, luggage, the small chin scales for watch bands, etc.) and meat (sauce picante, gumbo, sausage, etc.). They have played a major role in the history of our culture.
Back in the 1960s and before, alligator populations were declining everywhere. Much of the loss was due to habitat loss, but most was due to poaching and other forms of unmanaged slaughter. In the mid-1960s, alligator hunting was outlawed, but the slaughter continued.
Typically, the folks who owned and managed marsh where alligators lived considered alligators the enemy. Most of these folks made their living trapping and fishing and they viewed that alligator as competition for these resources. If they did not kill alligators themselves, they certainly did not attempt to prevent poachers from doing so. Why would they? The poachers were doing them a favor!
With protection, poaching did not totally disappear, but it decreased markedly. Alligator populations began to enlarge, especially in prime habitat. Studies by the Louisiana Department of Wildlife and Fisheries (LDWF), formerly led by Ted Joanen and Larry McNease at Rockefeller Wildlife Refuge in Cameron Parish, indicated that the alligator could be a managed natural resource. Louisiana petitioned the U.S. government to allow an alligator harvest season in areas of high population. Louisiana had its first legal alligator season in September, 1972, much to the consternation of many animal and environmental groups. LDWF maintained that, if managed properly, alligators could contribute to the economy while their populations remain strong.
What does "managed properly" mean? They set forth a management plan that was based on scientific knowledge of the species' natural history. The following steps were mandated:
1. The season would be in September each year. This assures that nesting is over.
2. Alligators can only be caught on hook and line. This prevents "hunters" (we'll call them harvesters since they are really simply running trot lines) from selecting the alligators they take. The catch is random. "Poling," the practice of using a long pole with a hook on the end, was outlawed since it is not random and gives the hunter the advantage.
3. Bait can legally be set anywhere, but by far the easiest location for the harvester is in canals and channels. During September, most female alligators are out in the marsh and most alligators in canals and channels are male. If most harvesting is in canals, most alligators taken will be male. Since one male can service many females, this insures that the egg producers are protected and it is thought that enough males would be left to take care of the ladies.
4. Hunters are advised to hang their bait high enough over the water so that only larger alligators can reach it. There is no fast rule of thumb, but some of my colleagues hang their hooks at 8" above the water and they have never caught an alligator of less than 6' long. When they hang at 18", they get gators about 10' and up. The level above the water becomes critical when harvesting is done in tidal zones where the tide may come in an submerge the bait (a good way to catch small gators and catfish!).
5. Harvesters must either own or lease the property where they set their lines. This controls who is where.
6. Each year, LDWF censuses alligators parish-by-parish. Their estimates are in alligators-per-acre-of-marsh and they annually determine how many alligators can be taken in each parish depending on how many acres each harvester controls. If population estimates are low, they set the harvest low; if high, they set it high. They can, of course, close the season, overall or locally, if their data suggest they should.
7. On the basis of "6," each licensed harvester is issued a certain number of tags. Each of these tags represents one alligator that they can harvest. If they lose a tag, that is one less alligator that can be harvested.
All of this adds up to a plan based on the knowledge of science of the species, annual population estimates, and controlling who harvests where. This should work well, but does it? I have been on several trips to harvest alligators. On these trips, I have witnessed the following:
1. LDWF personnel have met us and indicated, before they could even see us, that they knew who should be in the boat and how many alligators we had on lines.
2. All that we harvested (some 30 or so) have been males.
3. Their sizes have ranged from 4-13 ft.
4. In one instance, an alligator that had a tag affixed thrashed about in the boat and lost its tag. LDWF personnel required us to place a new tag on the skin, thus reducing our harvest by one.
5. The next spring, I have seen plenty of alligators in the harvest area.
In addition to the annual harvest, there are two other sources of alligator skins and meat.
1. Farming: Adult alligators are maintained in captivity; mated; their eggs incubated, hatched, and raised; the young are harvested.
2. Ranching: Alligator eggs are harvested from "wild" nests and removed to alligator farms. The eggs are hatched and the young raised. When the young reach 4' in length, 17% of the number harvested are required to be returned to the site of collection. This works well for alligator populations because a) normally only 17% reach this size in the wild and b) at this length, there are few predators (most predation takes place on the younger individuals).
This has recently become controversial, in that a study by Dr. Robert Chabreck of LSU has suggested that most, if not all, of the returned alligators are quickly consumed by the existing adult population. This has been refuted by Ted Joanen and Larry McNease, Louisiana Wildlife and Fisheries, who developed the management protocol. They say that predation can be minimized if the young alligators are returned to the nest (in the marsh), instead of the canals where the large adults are waiting for a meal.
The system seems to be working. Alligator populations are very healthy!
NUTRIA
Coypú or swamp beaver? Actually, both are common names of the aquatic mammal we most frequently call the Nutria (Myocastor coypus). Or, is it "nutra," "neutral," or "neutral rat," as frequently mispronounced in south Louisiana?
Now one of our most familiar rodents, the nutria had a most interesting introduction to our continent from its native Argentina. A few were released in the marshes around New Orleans during the early 1930s, but were presumably all captured by trappers. About that time, the great Louisiana naturalist, E. A. McIlhenny, better known for his famous Tabasco hot sauce, imported 20 or so nutria and placed them in an enclosure at his wildlife refuge on Avery Island near New Iberia. The nutria did well, but in the late 1930s they invaded the adjacent wetlands - and there are two stories of how this happened. The urban myth is that a storm allowed their escape into the marshes. The truth is that Mr. McIlhenny was urged by the Louisiana Department of Wildlife and Fisheries to import the animals and release them into the marsh to create a new fur crop! Also, now there is evidence that others also imported nutria in several places in the state.
The stage was set - miles and miles of suitable habitat virtually devoid of competitors. An additional positive feature was that there were only two real potential predators for adult nutria: large alligators and humans. Juveniles, however, are preyed upon by an assortment of predators such as snakes, turtles, gar, and some raptors.
At first, the trapper considered them a nuisance, but once the value of the pelt and carcass were realized, the nutria became economically valuable. In less than 30 years, nutria became the number one fur crop in the U.S., with most pelts going to France where they were popular wear. For some reason, they never caught on in the U.S., even though they were marketed as "Hudson Bay Seal," a name that drew attention to their pelt's similarity to seal fur while hiding its less than attractive source! They continue today to be utilitarian wear in southern South America.
There is a connection between nutria and a beautiful yellow flower that literally covers the surface of swamps and freshwater marshes each fall. This flower is Smooth or Nodding Sticktight (or Beggertick) (Bidens laevis or B. cernua, respectively; flowers erect in the former and nodding in the latter), but better known as "fourchette" in south Louisiana. These flowers produce a seed that has barbed awns which hook into the skin of nutria, causing a severe dermatitis and ruining the pelt. It is strange that a plant that provides such beauty can have such a devastating affect on the economy!
Nutria are strict vegetarians, but they do not eat only nuisance plants such as water hyacinth and alligatorweed. They eat a wide variety of species, including rice and sugarcane. Their messy feeding habits make them particularly wasteful - they only consume 10% of what they cut down with their sharp incisors. Nutria are aquatic by nature and live in burrows. This habit frequently causes problems for humans, because their burrows weaken levees. In areas with tall vegetation, they often form "hides" by tunneling about under matted grass.
They are quite social and family units may stay together for a time. Their babies frequently cling to their backs as the adults swim about. Nutria can often be heard calling to one another in the wetlands. Their voices sound like "n-e-e-w" or a nasal "nan-cy."
Humans who work in the marsh may get an occasionally case of "nutria itch," resulting in severe itching and swelling. It is caused by a small roundworm (a nematode of the genus Strongyloides, pronounced "strong eh loy' dees") that is parasitic in nutria intestines. Nematode eggs leave the nutria in its feces, and they hatch into tiny larvae that swim about in the water. Normally, these larvae burrow into a nutria, become adults, and the cycle begins again. If some hapless human who is not wearing boots comes along, the larvae burrow into his or her skin. Since humans are not the normal host, the larvae burrow about until they die. The whole process can cause three weeks of unmitigated agony!
Since they are now rarely hunted and the number of large alligators has declined, nutria populations are out of control. Populations in some stretches of Louisiana marsh may reach 6,000 nutria per square mile! When the populations of these ravenous critters get too high, they may eat all the vegetation, including the roots. This results in barren areas, sometimes hundreds of acres in size, referred to as "eat outs." This leaves the marsh vulnerable to further destruction by natural forces. Marsh ecologists now believe that the uncontrolled nutria population is a major contributor to the demise of our coastal wetlands.
So, nutria are eating out coastal marshes since there is no present market for their pelts. What are we to do? Let's eat them! They actually have a wonderfully lean meat that tastes great. Just after World War II, they were sold in the U.S. as "Hoover Hogs." Nutria is marketed in Europe under the name "ragondin" (the French name for nutria). Obviously, we have to convince folks that they are not rats (note: not all "rodents" are "rats," e.g., squirrels). We may get a little help from science.