23 July 2015

Award-winning crayfish

Marmorkrebs are an integral part of a new aquaponics project at Western Michigan University.

In March, five Western Michigan University students won a $15,000 Wege Prize—a national sustainability award—for their aquaponics system.

Marmorkrebs get used in this project because:

Instead of buying regular fish food, the team will raise spirulina algae and marbled crayfish—both of which are easy to raise.

You can tell from the bit about Marmorkrebs on the infographic that this is a university project run by academics.

Marbled crayfish
This recently-discovered crustacean species reproduces through parthenogenesis, an asexual process in which a single female creates genetically identical clones. As an all-female species, marbled crayfish reproduce exponentially and are less aggressive than other species, which makes them better suited for aquaculture. They are fed spirulina algae and BSFL frass. Being omnivorous scavengers, the crayfish can also process undigested waste as supplemental feed. In this system, they are used as a feed component, but could be raised for human consumption if demand exists.

How can I tell this was written by an academic? Not because of the fancy word “parthenogenesis,” but because only an academic would refer to a species that appeared in the scientific literature twelve years ago as “recently described.”

I’m also a doing a bit of an eyebrow raise over this statement, “As an all-female species, marbled crayfish reproduce exponentially and are less aggressive than other species...”. It’s worded in such a way that might suggest the alleged lower levels of aggression are due to them being female, which is absolutely not the case. Female crayfish fight just as hard as males, and study after study has repeatedly found no strong effects on sex on outcome of fights.

Finally, I think it’s a little unlikely that Marmorkrebs are likely to have much demand for food for people. They’re a small species, and you’ve not going to get much meat off them compare to, say, Louisiana red swamp crayfish or redclaw crayfish.

External links

WMU Students To Build Sustainable Aquaponics Farm
Local Loop Farms

1 comment:

Neil said...

From my observations it seems the adult crayfish are most aggressive in the period after they molt but before producing their next batch of eggs.

They seem more aggressive immediately following the release of their young and then are increasingly more defensive till they molt.

Following the molt they become hyper aggressive. Instead of foraging during the night they are more likely to display ambush behaviors, climbing to high places and wait in a aggressive stance for prey.
During this time they also seem to be more inclined to cannibalism, consuming tank mates or juvenile crayfish. They also seem to be more inclined to high protein food sources such as meat scraps.

As soon as the next clutch of eggs is produced the crayfish becomes docile and secretive. The inclination towards high protein sources is gone and a plant based diet is again preferred.

I assume a male crayfish would be aggressive all of the time excluding the immediate pre and post molt period.

The adult marmorkreb alternates between long periods of lower aggression.

So maybe "less aggressive" on average over time?