The Macrocheira Kaempferi, or the Japanese Spider Crab, has been previously highlighted as a species of interest for experimentation with Mariculture. This report aims to detail the important elements of the Japanese Spider Crab, and how it may be possible to breed them efficiently as a luxury good in the Kamchatkan Inner Sea area. We have compared our own notes and hypotheses with surviving records from pre-flood Horseshoe Crab Mariculture from China, and will be providing a feasibility assessment for the pleasure of the First Citizen, our patron.

Spider Crab Culture

Pre-Flood the crabs were originally found along the eastern coastline of Japan, between the 30th and 40th latitudes. Climate changes have led to their migration north across the Kuril Islands towards our own coastline, with some being sighted as far north as the 55th Latitude, the main instigator being temperature changes. We have determined that a range of 10 to 20 degrees Celsius is ideal for a bountiful population, consisting of a range high enough for the larval state to endure, up to around 20 degrees, and low enough for adults to prosper: closer to ten degrees. We have found small groups of spider crabs exploring beyond their natural means, but these groups seem to be older specimens, as denoted by span of claw to claw. Temperature seems to be so vital to spawning rates that brief temperature spikes can kill young at surprisingly high rates.

Crabs average at a central carapace of 37 - 40 centimetres long, with arms that stretch several meters. Their dimorphism is limited to an altered shape of central carapace. In bio-construction, the crabs are relatively weak and poorly put together, with their legs often being removed in commercial fishing. They possess the ability to regrow legs through molting, though only to a limited degree. Their reproductive potential is extremely high, allowing small numbers of be implanted to suitable locations to create much larger populations. Furthermore, there is no parental instinct, allowing young populations to grow and thrive on their own. In fact, these creatures fail to demonstrate many of the social activities of even other variants of Spider Crab, being largely independent.

As Omnivores, these crabs are relatively easy to feed, being able to subsist off of almost anything so long as a source of bones is nearby. They skirt along the seabed and pick up scraps of food in the wild, whether meat or plant life. They have been known to utilise sponges as tool, but on a much rarer basis than other crab species. The young seem to use them as camouflage, whereas the elders are large enough that they do not seem to need it. These sponges are often still living. The specific species of sponge does not seem to be important. Estimates for their lifespans are unknown, beyond the first youthful period, though old world knowledge suggests longer than a century. For our benefits, they become a viable crop within only a few months.

Suitability for Mariculture

Japanese Spider Crabs require a very specific range of temperatures for raising, and seem to do better at certain depths later in life. While these conditions can be simulated in artificial environs, they are far from optimal for raising. One proposal has been the construction of deep pools within buildings, allowing the crabs to live at appropriate depths in a controlled temperature environments. Such pools would need to be 100 meters deep, with about five meters of floor space per crab minimum, and food to be regularly sprinkled down into the tank. Maintaining a sandy bank 100 meters tall along a slope downwards while still feeding these creatures is an ambitious project. While our estimates say this would not be worth the cost of construction, we do not have the evidence available to conclusively rule against this.

Due to the intrinsic temperature security of the Inner Sea, and the gentle slopes available along it’s edges, the possibility for partially isolated Mariculture is a much more feasible possibility. While we predict a larger amount of environmental disruption to the process, and admit that the predicted 15 degree temperature average over the year is below optimum levels, it is much more viable a solution. Such a process would require a higher scale system of Mariculture, taking up a wider area and dislocating a larger number of local species. However the relative cheapness of building and maintaining these semi-enclosed areas along the affected shoreline would allow a much more efficient setup.

We also maintain that there is a significant benefit to introducing the Spider Crabs to the Inner Sea as wild creatures. There is a significant catch of them becoming a regional staple for as long as the temperature does not drop drastically, and minimal estimated conflict with other creatures of the region. Unlike most marine life, there has been a very low report rate for major mutation in Spider Crabs, and it is professional consensus that more hardy creatures make for a more healthy food ecosystem.

Conclusion

We support the proposals of Semi-Enclosed Mariculture and Inner Sea Introduction, while recommending against investment in fully artificial environments. We believe that Semi-Enclosed Mariculture is the most efficient set up, and that Spider Crabs are capable of adapting to these conditions very well. The greatest threat to the project is the ambient temperature. We would advise a testing program be held over a 12 month period to monitor the crabs response to temperature variation, before heavily investing in the project.

[Meta: Thank you Encyclopedia of Life for making me want a pet crab. 3 Commercial Abstract.]