ARC Marine Tank Tuesdays: The New Crayfish Nursery

ARC Marine’s crayfish larvae get a new home

Today marks the inaugural release of our crayfish larvae in to their new home, in our lab at Brixham! Six weeks ago, we tickled the crayfish babies from their mother’s abdomen in to a small netted holding tank. Now they’re getting an upgrade and we’ve dedicated a whole tank for them to live, thrive and grow in.

ARC Marine crayfish tank

Above: the new crayfish tank

 

The larvae and their parents, Reggie and Ronnie are very important to us at ARC Marine because we get to study how they live around our structures. They are Australian Red Claw Crayfish Cherax quadricarinatus, but we hope that they will inform us about the UK’s native white claw crayfish Austropotamobius pallipes.

In the original aquarium with Reggie and Ronnie are some structures that we’ve created to make them feel at home. We’ve given them half a 12.5cm Reef Cube and specially designed crayfish inserts that have a conical entrance like a burrow. Reggie and Ronnie spend a lot of their time in the inserts peeking out, with their antennae, antennules and chelae (claws) poking out. They also use the half cube to shelter from us prying humans as we walk past and they’re out and about foraging for food.

A while ago we discovered that Ronnie was berried, meaning she had a clutch of eggs under her abdomen. Low and behold they hatched in to tiny crayfish larvae. Hopefully their successful mating indicates that they are happy and healthy.

We’ve also tried to provide habitat for our larvae by giving them some of our mini 3D-printed models of Reef Cubes. The young crayfish showed a near immediate interest to the cubes, with the majority spending their time in and around the cubes. It was very positive to see and could inform our design process, to provide small cubes for larvae in the wild. It is possible that the cubes encourage less aggression from the juveniles as the young were spotted fighting more frequently without the cubes and they seemed to get on better in the cubes. This could mean that the increased shelter provides a richer mix of territories, leading to less disputes. We’ve seen two larvae at a time leaning out of the top of a cube, with their chelae raised like they’re manning a sentry post; with others milling about below.

Originally, we had hoped to release all the larvae in with their parents. We separated an area of the adults tank with netting and made a mini cray fish city for ten of the larvae. Ronnie their mother was suspiciously keen to get in there. The next morning we found her in there and the larvae were absent. We removed the netting and later found some of the larvae, but we feared that she had eaten the others. Her intentions may have been to get away from her male counterpart Reggie for some personal space (understandable) or they could have been to cannibalise her children, we don’t know. In any case, it was decided to give the larvae their own home instead, avoiding a load of stress and murderous intentions.

On the 6th of November 2018 preparations were made to move the young into a separate tank, so that better observations can be made. Today on the 20th we released the larvae in to their new home.

ARC Marine Crayfish juvenile Reef CubeARC Marine Crayfish juvenile Reef Cube

Above: the crayfish juveniles exploring their new home

So what’s the point?

The United Kingdom’s waters are filled with a massive variety of weird and wonderful life but there are many species that fly under the radar, like the white clawed crayfish A. pallipes. A. pallipes is the UK’s native cray fish. It is a decapod crustacean (crabs, lobsters, prawns etc.) with a range from The Balkan Peninsula, to Great Britain and Ireland; and it is an endangered species. Historically, A. pallipes was a commonly fished species around the UK but it has been near wiped out by a crayfish plague (caused by a water-based mould). Efforts to substitute dwindling populations with the American signal crayfish led to further declines, as the American species out-competed our UK crayfish. Furthermore, the invasive species carries the deadly crayfish plague, whilst having a resistance. We at ARC Marine would like to give our native cray fish the chance that they deserve so we create bespoke habitats for them and plan to initiate a regime of invasive crayfish trapping. So far, we have set up a reef of our Reef Cubes at Vobster Quay with a small introduction of 36 A. pallipes. Along with the larger introduction of A. pallipes elsewhere in Vobster we hope that this will make a thriving population.

Check back soon for more details on how the crays are doing and what they’ve been up to. We’ll be observing their abundance around the tank to see if they prefer our habitats to plain gravel.

By Sam Hickling and Jamie Matthews

Tank tuesdays is a series of mini articles describing the marine life here at ARC Marine’s aquaria; and their interactions with our artificial habitats.