Lab Requirements


Figure 30 - Food Sources and Growing Timeline. Author Illustration

Laboratory rearing requirements are the same for each type of aquaculture. Female crabs must be kept, mated, and their fertilized eggs harvested after brooding. The female crabs are housed in 90G fiberglass tanks with a footprint of about 1' x 2'. These tanks can be stacked onto shelving in order to minimize space requirements. The females are partnered with males for mating on a 4 foot by 8 foot table subdivided into 1 foot by 1 foot by 1 foot slots. After insemination and brooding the lab technicians harvest the fertilized eggs on a large workbench with several large sinks, flexible lighting, and materials storage. Immediately adjacent to this workspace, there will be a walk-in cooler/freezer and access to large quantities of sterile fresh/salt water. The most important aspect of the lab design is the drainage, because an improperly designed drainage system will require hours of cleanup where a better-designed one might only require minutes. Some successful operations use floors sloped into 1' wide and deep canals that run to a main drain.
When the eggs hatch and the blue crabs emerge as larvae, they quickly begin to develop through the 7 larval stages. As larvae, the blue crab is fed with rotifers, a phylum of microscopic and near microscopic pseudocoelomate animals. These rotifers can be raised in centrifuges or large tanks, and they are fed in turn using algae. If the rotifers are raised in centrifuges, the algae can be concentrated into paste and supplied in this manner. Otherwise, the algae would be grown in acrylic bags/cylinders, a process requiring a half-time employee. The crab larvae themselves are raised in 500 fiberglass tubes. They are somewhat expensive but, when empty, they are very light and can be easily shuffled around by a single person. Each tube holds approximately 10,000 liters and are stocked with larvae to a density of 150/L each. Four such tubes per raceway would be sufficient for a farm project of this size.

When the blue crab develops into the post-larval, or megalopae stage, it requires a food source of a higher biological order. Artemia, also known as brine shrimp or more commonly as sea monkeys, are a low developmental order crustacean perfect for this second round of live feed. Artemia feed on algae, brewers yeast, or even egg yolk. The artemia are hatched, grown, and concentrated in a series of 200L conical buckets. These buckets have a radius of approximately 2'0” and it is believed that 6 to 8 would be needed for this operation.

When the blue crab develops from the megalopae phase and into the juvenile state, he undergoes some substantial changes. From this moment forward, the crab is capable of withstanding waters with saline content as low as 3ppt, and his food sources become substantially more complex. Blue crabs can eat almost anything, but they prefer to eat worms, oysters, scallops, bay grasses, small fish and of course other crabs. Because the crab will grow in size so very substantially during this phase of his life, there is no room to house him in the laboratory. From this point, the blue crab enters the second phase of his geographic life—the raceway phase.
BLUE CRAB FARMING 25 BLUE CRAB FARMING 26
[21] For a visual, go to Solar Components Online—www.solar-components.com.