Research & Resources

Exciting research has been done over the last 10 years, mostly under the banner of North QLD Crayfish Farmers Association and funded by NQCFA & AgriFutures (formerly RIRDC)

NQCFA Selective breeding project

Back in 2007 NQCFA received a grant from RIRDC (now AgriFutures) for a selective breeding project (link to document) It involved a “cast of thousands”, well at least all the NQCFA farmers and a few academics and a geneticist. After 5 years of hard work managed by John Stevenson we produced a “domesticated redclaw” initially called the Tolga strain with superior growth over existing stock. AquaVerde has taken over the legacy of this project and although we haven’t continued with the highly managed breeding, we have kept the broodstock thoroughly mixed for the time when we have the capacity to continue this great piece of work.
AquaVerde is pretty proud that the first big use of our incubator was to help facilitate the selective breeding project. Without an egg incubator it would have been impossible to achieve the high level of control over the process needed.

Survival projects

In 2014 AgriFutures funded a 5-year project titled “Eliminate factors inhibiting redclaw farming from reaching its full potential”

This is a project under the auspice of the North Queensland Crayfish Farmers association. Colin Valverde is the Principle Investigator and liaises and coordinates with the researchers.

This project has three main study areas to do with removing bottle necks in crayling production: a) “control of Aeromonas hydrophila in the hatchery” using bacteriophage therapy (Lisa Elliott), b) “crayling survival” (Clive Jones/ Damian Rigg) and c) “handling stress mortality” (Leigh Owens and co.)

 

 

Nursery

Dr Clive Jones and PhD candidate Damian Rigg have been working on this part of the project (see nursery) It has involved pond, tank and aquarium trials to better understand craylings. And a lot of tedious work by Damian on metabolic rates, results are still coming in and more details to follow.

New Worm

Tenmnocephalids are a type of commensal that live on crayfish. Many different varieties have been described. They generally make their living on the crayfish but are not actual parasites and in moderate numbers do no harm. However, a worm that we always saw while stripping the eggs from females kind of had us worried. It seemed to live buried deep inside the egg mass and its internals were the same colour as the egg yolk of redclaw eggs. Coincidence? We think not! We brought it to the attention of some JCU academics who thought it had never been described by science before. A new species?? An honours student, Jenifer Brand came to study the worms on our farm and produced a paper (see attached) And to our amazement it turns out that it was a new species and yes, it does feed off redclaw eggs. Although it’s not completely clear to us if they feed on healthy eggs or already dead eggs. So, may we present to you the newly discovered Decadidymus valverdi (link to picture). We are honoured to now have a small parasitic egg worm named after us! During the study we catalogued 5 species of temnocephalids on our redclaw. The Latin names are too difficult to pronounce so we called them Fatty, Scaly, Glider, Squidy and our newly discovered worm: “10 balls”. Look up the Latin Decadidymus to understand why we call them10 balls.

Bacteriophage

NurseryVirusThis is a method where bacteriophage are isolated from problematic bacteria, amplified and re-inoculated into the system to control specific bacteria. Bacteriophage are similar in action to virus and look a lot like them. (link to project documentation, coming soon)

Virus

One of the only negatives of redclaw is the occasional mortalities that can occur after adult redclaw have been handled and stressed. We call it Stress Handling Mortalities (SHM), yes, I know not a very imaginative name. Anyway, it’s a problem for harvest and transport and sometimes for broodstock that are frequently handled, and also perhaps the mortalities in grow-out ponds are related? We asked Assoc Prof Leigh Owens to do some histology on some moribund crayfish to see if he could find any physiological reasons for the deaths. It’s been a long journey and quit a story to tell. But the result was the discovery of 2 new viruses that were previously unknown to science. We still have work to do but all populations tested for this virus have proven positive and it appears that the viruses have probable evolved with redclaw a very long time ago. Although the virus is always present it only causes problems for up to a week after a big stress event. We are hoping that a fix can be found for SHM that will not only reduce handling deaths but improve survival in our production ponds.

Resources