Managing Chesapeake Bay Blue Crabs
Is There a Better Way?

Douglas Lipton, Sea Grant Marine Economic Specialist

Despite an extremely poor year for landings in 1998, blue crabs remain one of the most valuable resources harvested from the Chesapeake Bay. Dockside value of commercial harvests in Maryland alone was worth $29.8 million, 66 percent of the total value of all species harvested from Maryland's portion of the Chesapeake Bay. Blue crab harvests also support an important processing industry, estimated to have produced $22.4 million worth of value-added products and provided employment to almost 1,200 workers in Maryland in 1998.

Fishery scientists use sophisticated population models to determine the status of the blue crab resource, whether, for example, a poor year is part of the natural fluctuation or a signal that the stock is in trouble. While there is some disagreement, the models point to concern that we may be harvesting too many crabs from the population, thus threatening the long-term viability of the resource. There is also concern that loss of habitat, principally sea grass beds, is also threatening the health of the blue crab resource by making crabs more vulnerable to predation. However, because of the large year-to-year variability in the blue crab resource, largely attributed to climatic and other natural environmental factors, it will be difficult to know for sure the amount of overfishing, if any, that is occurring. Watermen, whose livelihoods depend on catching as many legal-size crabs as possible, will be reluctant to agree to new regulations that limit today's harvest or restrict how, when and where they can harvest crabs for an uncertain return from greater harvests in the future.

Fishery economists in Maryland and Virginia agree that the current management regulations for blue crabs are doing nothing to offset the declining productivity and profitability of watermen. Jim Kirkley, an economist at the Virginia Institute of Marine Science has calculated that productivity of the blue crab pot fishery, the dominant gear type, has declined by 22 percent from 1960-1991. The cause, according to Kirkley, is that the same number of crabs is being harvested by an increasing number of pots. Therefore, more boats are being used, more bait is being fished and more fuel is being burned - and yet, there are no more crabs to show for all this increased effort.

An obvious question is why are watermen using more gear than is necessary to catch the amount of crabs they are harvesting? The answer is rooted in the fact that, unlike other types of industry, the marketplace doesn't efficiently regulate production in the blue crab fishery. While crabbers incur expenses for gear and fuel, there is no charge for the crabs themselves - this is the case for most open access fisheries. If there was a charge to watermen based on the number of crabs harvested, the cost for the remaining crabs would increase and production would eventually become unprofitable. In the blue crab fishery, if watermen want to catch more crabs, they can fish more gear and incur that expense, but they don' t have to pay more for the additional crabs they catch. The consequence is that when a harvester puts out another hundred crab pots, he or she catches more crabs while a second waterman catches less. So what does the second waterman do? He puts out another hundred crab pots. The total catch between the two crabbers stays the same, but we now have 200 more crab pots with associated bait and fuel that are totally unnecessary for catching the crabs. This story gets repeated over the thousands of watermen that crab in Chesapeake Bay.

In both Maryland and Virginia the management agency response to this situation has been to limit the number of crab licenses and amount of gear allowed per license. This does nothing to reduce the amount of gear in the fishery, and there are indications that under the current system the total amount of gear can still go up since not all watermen fish the maximum amount of gear they are allowed. Another management technique is to limit the time and areas where and when harvesting can take place. In many fisheries where such limits have been tried, the fishermen squeeze more and more effort into less time and space. An extreme case, before management was changed significantly, was the Pacific halibut fishery which would last for little more than a day per year.

Fishery economists have devised a number of potential techniques that can help return a fishery to a more economically efficient state. Most of these management techniques are rights-based - they confer on an individual, organization or firm a right to harvest a proportion of the harvest that, from the biological models, is deemed acceptable. The harvest can then be taken in as low a cost manner as possible to help ensure that the greatest profit is obtained from the resource.

With support from the Chesapeake Bay Commission, we have a two-year period to introduce these concepts to determine whether they are worth adopting in the Chesapeake Bay blue crab fishery. The Commission's Bi-State Blue Crab Advisory Committee has been awarded $300,000 from the states of Maryland and Virginia to devise a series of activities, among them, workshops and facilitated stakeholder meetings that will allow a closer examination of these and other management options by key stakeholder groups. I will be actively involved in this two-year activity as the Maryland Sea Grant Extension marine economic specialist, as will our Maryland Sea Grant Assistant Director for Communications and Public Affairs, Jack Greer.

Aquaculture Down Under

Don Webster, Eastern Shore Area Agent, and
Don Meritt, Shellfish Aquaculture Specialist

If you have trouble pronouncing a name like "Chincoteague," think twice about going to Australia. You could find yourself between Narrabeen and Woolongong while trying to get to Coolongatta and not know how to get there...or even how to read the names on the map! Aside from that, and remembering to drive on the left while you figure all this out, it's a vast and beautiful country, filled with friendly people. We recently had the opportunity to go there for the annual meeting of the World Aquaculture Society (WAS). In the week before the conference began, we traveled between Sydney and Melbourne visiting aquaculture sites and others involved with research and management of aquaculture and fisheries "Down Under."

Aquaculture in Australia currently employs over 7,000 people at the farm level and an additional 21,000 rely on some part on the industry. While the nation has a vast coastline and a relatively small population, it is a net importer of low value seafood and an exporter of high value products. Of all the products raised, none are more highly valued than the Australian pearl industry, which raises some of the highest quality cultured pearls in the world. The Australians learned the business from Asian experts and went on to enhance it. With Asia nearby, it has a ready market for all types of quality products.

Because of a narrow continental shelf and a lack of major upwelling zones, Australia is not a strong producer of wild fish; still, the nation has significant quantities of good water for aquaculture production potential. Government agencies predict that the industry will perhaps triple in size over the next decade, providing lots of opportunity for new jobs and revenue.

Oyster Culture in New South Wales

Arriving at Sydney airport at night after 22 hours in flight, we quickly got out of the city to avoid the morning traffic and spent the next several days in New South Wales traveling Australia's beautiful coast. The industry in New South Wales produces oysters, mussels, silver perch, yabbies (crayfish), and barramundi. Anxious to see the oyster culture methods used there, we spent time in Bateman's Bay visiting members of the Clyde River Oyster Association. There are about forty producers in the area who raise Sydney Rock Oysters using stick and tray culture. They produce a high quality product that is sold for the half shell trade.

Stick culture involves taking bundles of treated lath and placing them in areas where oysters spawn. Spat attach to the sticks, which are then stapled to intertidal racks for the initial growth period. They are periodically out of water, which helps to control fouling organisms and give the farmer time to clean them with a pressure hose.

Oysters are removed from the sticks either at harvest or earlier, when they may be finished out in trays before going to market. They are then sorted and graded, depurated in ultraviolet sterilization units for a period of time, packed and shipped.

The shellfish may be finished in trays which are either made out of wood frames or injection-molded plastic. The wooden frames have wire mesh firmly stapled to the bottom with stainless fasteners, while an internal series of braces divides the trays into compartments and allows oysters to be placed in them for growout. Another piece of mesh is used for the top but it is put on with steel staples so that they corrode over time and are easy to pull out for culling or harvest. Molded trays are produced with covers that snap in to hold the animals and with interlocking pieces at the corners that allow several trays to be connected together.

We have noticed over the years that most oyster growing areas are quite similar, no matter where they are located. There are usually piles of materials that the growers have tried over the years that have either been abandoned or just piled away until they might be used again. Oyster growers are constantly trying new ideas and working on ways to improve their operations and grow better oysters faster.

A constant project for the growers in this area is the destruction of spat from the Japanese oyster Crassostrea gigas. These are seen to compete with the local oysters and are not worth as much in the marketplace. At an oyster ecology conference several years ago that looked at the impact of C. gigas worldwide, Peters reported that while introduced oysters helped create an industry in Tasmania and South Australia where none existed, C. gigas was declared "noxious" in New South Wales and was to be destroyed where found. Growers here spend a great deal of time picking off the unwanted animals and destroying them so that they do not get a chance to compete with their Rock Oysters.

One oyster producer we visited used a French manufactured grading machine to sort his animals in sizes preferred by various segments of the market. We later were able to see many of these oysters on display in the Sydney Fish Market, where they were highly prized and commanded top prices.

Recognizing the need for trained aquaculture producers in New South Wales, the National Fishing Industry Education Centre offers correspondence courses for the industry. These combine mailed lessons, with telephone and Internet backup, along with short courses to handle hands-on work. Students successfully completing the course are awarded a certificate in Aquaculture Production. These courses have been very useful for people with some existing background in farming or aquaculture and have provided technical information for people who are scattered throughout a wide geographic range and unable to attend regular classes.

Aquaculture in Victoria

While in Melbourne, we visited the Victoria Department of Natural Resources. It is interesting to note that this department actually combines responsibility not only for natural resources but also for agriculture, aquaculture, and the environment. If these functions were combined in a place like Maryland, the resultant bureaucracy would be immense. Such a bureaucratic arrangement tends to follow a trend in many other countries, however, of combining both agriculture and fisheries functions in a single agency. The folks at Victoria DNR were very interested in information exchange and, like their counterparts from other Australian natural resource agencies, were much in evidence at the conference in Sydney where they were attending, participating, and working to keep things moving well.

Aquaculture in Victoria has a current value of approximately 18 million Australian dollars, with production around 2,000 tons. Strong growth is expected to double that production by 2001. The mainstay of the aquaculture economy in the state is salmonid farming, most of that rainbow trout, which is increasing at about ten percent per year. Atlantic salmon are also being grown here, as are eels; other species under development are abalone, scallops, oysters, and flounder.

The range of aquaculture businesses in Australia includes finfish, molluscs, crustaceans, and even other animals like crocodiles. Some products are silver perch (a freshwater native), snapper (also known as red-sea bream), prawns (never called "shrimp" here), various "crawdaddies" (marron, red-claw, and yabby), barramundi aquarium fish, and even bluefin tuna.

On the way back from Melbourne to Sydney for the conference we stopped at a trout farm for a look at Victoria's principal fish culture industry. The business included a hatchery for raising several species including the golden trout. Sales are through wholesale outlets and, at the same time, the company operates a very well run fee fishing operation. Nicely landscaped grounds, helpful employees, and a range of different size fish make this a very popular place in the region.

. . .

Back in Sydney, the World Aquaculture Conference featured eleven concurrent sessions on most days, showing the tremendous increase in aquaculture research and development that has occurred. The trade show featured the best of Australian companies and agencies, as well as those from other countries. Receptions featured aquaculture products from Australia and were of excellent quality.

At the close of the conference, the aquaculture industry put on a two-day expo at the Sydney Fish Market. This state-of-the-art facility normally trades over 400 different seafood products. The aquaculture exhibits showed production practices, had examples of their products available, and featured continuous cooking demonstrations. It was an interesting way to spend an afternoon and a credit to the aquaculture producers of Australia.

We came home with some good ideas, many new friends, and the hope that someday we'll be able to go back again to see more of this interesting country.

For more information on the World Aquaculture Society and for Aqua 2000 in Nice, France, May 2-6, 2000 see www.was.org. To obtain a copy of "The Ecology of Crassostrea gigas in Australia, New Zealand, France and Washington State" (UM-SG-TS-92-07), contact Jeannette Connors at (301) 405-6376 or connors@mdsg.umd.edu.

Biological Filtration in Aquaculture

Dan Terlizzi, Sea Grant Extension Water Quality Specialist

Probably the biggest challenge that aquaculture must contend with is the contained environment aquatic organisms live in: it is simultaneously a life support system and a waste removal system. Water in aquaculture systems provides oxygen and chemical components such as pH, alkalinity and hardness to support metabolism, while it removes carbon dioxide and nitrogenous waste products from the fish. All methods of aquaculture must provide for eliminating the wastes that are generated. In pond culture, waste removal may entail simple management strategies to maintain healthy microbial population, while in recirculation systems it requires carefully designed biological filters for treatment of nitrogenous wastes. Despite sophisticated engineering that has developed increasingly efficient filters, success or failure often depends on what amounts to a layer of "slime."

The slime I am referring to is the microbial film that covers the surface of materials in biological filters. This bacterial film is cultivated like an additional crop: ammonia, the primary waste product and key nutrient for these microbes, is added to the system during start-up so that it may be "seeded" with bacterial culture to begin colonization of the filter. Once the filter is established, we can stock the system with fish. Our investment now depends to a great extent on the effectiveness of the film. We know surprisingly little about this microbial colony - I often refer to it as a biological "black box," borrowing from the electronic expression referring to a system component where the input and output are known but the operations within are a mystery.

In biological filters we know that two genera of bacteria, Nitrosomonas and Nitrobacter, are involved in the conversion of ammonia to nitrite and nitrite to nitrate, respectively. But we don't understand a lot more. For example, periodically a functioning biological filter will "crash" or stop operating effectively for no apparent reason - ammonia levels in the system can rise dramatically, thus leading to fish mortality.

These inexplicable crashes have stimulated alternative approaches to waste removal in aquaculture systems - one of them is plant culture. Plants offer some advantages in waste removal compared with bacteria. Nutritionally, plants are well understood and can be readily evaluated for health. If a required nutritional component is in short supply, specific symptoms will appear in the plant and aid in the diagnosis, so that corrections can be made. Also, differences in plant nutritional requirements can be adapted to system needs. For example, in bacterial-based biological filters, the end product is nitrate which is not toxic to fish though it increases over time and contributes to the dissolved solids in the system. Some plants prefer ammonia, some nitrate and some will use both so that the nitrogen cycle components can be more effectively managed.

I referred earlier to the microbial biofilters as a second crop. With the use of plants in biological filtration, a second crop can be produced; however, it is important for growers to realize that a second crop involves a second learning curve and new management skills. Initially it is better to focus on a single product.

Plants are beginning to play an increasingly important role in waste removal in aquaculture. They have been used successfully in recirculation aquaculture systems and will likely be used more often in the future. Wastes generated in pond systems have also been successfully removed using plants in wetland biological filters. Plants are routinely used in aquatic ornamental systems for waste treatment. Howard Crum of Lilypons Aquatic Gardens recommends the ten percent solution which refers to having ten percent of a pond's surface area planted with submerged aquatic vascular plants. Although bacterial-based biological filters have been important in the development of aquaculture systems and will play an important role in the future, there is plenty of room for improvement. Many aquaculture systems of the future are likely to be improved by providing room for plants.

Selected Web Sites for Aquaculture Information

Progressive Pond Management Workshops

Yearly Pond Care & Maintenance in Southern Maryland

Jackie Takacs, Sea Grant Extension Regional Marine Specialist

With a grant from University of Maryland Extension, we will be conducting a series of workshops on year-round actions pond owners can take to maintain healthy ponds. The aim of these workshops, a cooperative undertaking with Charles County Extension Agent Pamela King and Maryland Department of Natural Resources Biologist Tamara O'Connell, is to teach preventative maintenance. Most pond owners do not seek help until there is a problem, for instance, dead fish or excess plants - unfortunately, by the time people realize they need help, the deterioration of their ponds has often become critical.

Pond maintenance requires the integration of several management systems:, among them watershed and water quality management, crop management and pest management. When done correctly, managing ponds is a year-round effort. Though not required every month, timing is critical - many practices build upon each other. An integrated management program will help pond owners prevent fish kills and minimize aquatic weed problems.

We held the first session on July 7th, an overview program that included an introduction to general principles and record keeping. Four more sessions, listed below, are scheduled.

All sessions will be held at the Charles County Cooperative Extension office, 9375 Chesapeake Street, #119, La Plata, Maryland 20646. Registration fee is $5,00 for the entire series or $2.00 per session. For more information and registration, call (301) 934-5403.

Aquaculture Publications

• ABC Prime: An Information and Research Update to the Industry
  
  Published by the Aquaculture Breeding Center, the Virginia Institute of Marine Science, this new periodic newsletter is edited by Standish Allen, the ABC Director. According to Allen, the core of ABC consists of "an infrastructure that will allow inhouse development of brood stocks and technologies for the benefit of the state of Virginia." The approaches, says Allen, range from traditional breeding techniques developed for agriculture to molecular technologies. To obtain a copy of the newsletter, contact Stan Allen or Tom Gallivan at the Aquaculture Breeding Center, (304) 684-7710, x7711 or by e-mail: ska@vims.edu.
  
  
• Aqua News
  
  A publication of the New England Aquaculture Educators Network AQUA. AQUA's goal is to prepare middle, secondary and postsecondary educators for introducing aquaculture curriculum into existing programs. According to Fenna Hanes, Director of the New England Technology Education Partnership, "Educators are teaching about aquaculture to prepare graduates to work in this emerging industry and teaching with aquaculture to engage students in the study of math and science and related fields." The current issue of Aqua News showcases the achievements of AQUA teachers and their students - articles were written by the educators and in some cases their students. To obtain a copy or subscription, call Fenna Hanes at (617) 357-9620 x136 or by email at fhanes@nebhe.org.