Freshwater blood and fluid sucking leeches can pose a serious problem for freshwater crayfish. Typically it’s the common yabby (Cherax destructor) that you find leeches attached to or they have a nasty round scar indicating a leech has had a feed. The scar remains until the crayfish moults but the scar itself can create difficulty in moulting and can lead to the death of the crayfish. From an aquaculture perspective, leeches in your ponds are a big NO-NO and every effort should be made to catch and remove them as the unsightly scars on crayfish make them unsellable.
Most leeches can ingest several times their own weight in blood at one feeding and swell to a large fat size. Leeches attach to their hosts and remain there until they become full, at which point they disengage and fall off to digest their huge feed. Crayfish are most vulnerable when they are freshly moulted. Freshly moulted crayfish are already stressed out and weakened by the moult process, the additional blood loss from a leech feeding could be fatal. This risk of mortality is greatly increased if the crayfish is small and the leach large.
The example Marron with a leech attached was found in the swimming hole below North Dandalup Dam, WA.
Images compliments of Tegan & Josh Moylan
I had the pleasure of traveling to Victoria to present a lecture on “The Freshwater Crayfish of Victoria” to the Bendigo Field Naturalists Club. They were great crowd and I had a great time chatting with them.
Whilst in the Bendigo area I sampled the local creeks and streams, only finding yabbies Cherax destructor.
The following day I had an aquaculture consult in the Seymour area and whilst there I took the opportunity to sample the local creeks and streams. Again abundant Cherax destructor but then a very nice surprise. I found a colony of Engaeus lyelli. This was excellent as I also managed to capture berried females, something I haven’t come across in this species before.
For a full article on Engaeus lyelli “Click Here”
Travelling south to the Otways the following day I sampled creeks, streams and rivers, finding mostly Cherax destructor and glass shrimp Paratya australiensis. One nice surprise in the Campaspe River were Australian Basket Shell Mussels Corbicula australis. They are a widespread and common species but usually hard to find so finding them easily was a pleasing result.
Further south around Waurn Ponds another nice surprise was the capture of a berried female Engaeus merosetosus. Enagaeus merosetosus are relatively common and widespread in that area however, females with eggs are exceptionally rare so the capture of one greatly increases the general knowledge on the species. For a full article on Engaeus merosetosus “Click Here”.
I spent several days at Otway Crays, Bellbrae, Victoria with the owner Steve Chara. Steve is a mate and we spent a few days together surveying the general area. Mostly we were finding Cherax albidus and Geochara gracilis. Both species were abundant and we found thousands. For a full article on Geocharax gracilis “Click Here”.
We also found Engaeus sericatus at a number of sites.
Steve Chara is one of Victoria’s largest yabby farmers and I spent some time with him sorting, grading and packaging yabbies.
Steve had a bi-coloured yabby in a tank, this is a rare treat as these are extremely rare animals. For an article on Bi-Coloured Crayfish “Click Here”.
Unfortunately the expedition was over all too soon and I had to head back to the office.
This post relates to some photos Chris from Queensland sent me. They are of his Cherax depressus which he found in the Noosa area. He caught the pair after a heavy rain event and took them home to his aquarium. The area they were captured is usually dry so they only come out of their deep burrows and get active when there is water around.
This is what Chris said:
“These two Yabbies are very polite and well behaved, they were very cautious in the aquarium at first. I put a red LED floodlight on the tank at night, just to see what they got up to, and found that almost every night these two yabbies would be side by side “dancing” – it was the female trying to instigate mating. The male wouldn’t perform so he was isolated for a few days. Two days after putting the male and female back in the same tank she was berried.”
“The babies began dropping from the mother on about the 10th of Jan, 2014. I kept the mother in a Guppy breeding tank for a few days to separate the babies from the mum, on the assumption that the mother would eat the babies. After three or four days I realised that the babies were safe so I put the babies in with their mum in a separate tank. Almost all of the babies reattached themselves to the mum. After two weeks the mother and babies are still living together, she ignores her young as they climb on her claws and eyes and get piggybacks during feeding time, but they very rarely go to the tail anymore. The mother has shed her shell and simply appears to be happy, surrounded by her offspring.”
Cherax crayfish make great aquarium pets and they occur throughout most of Queensland. But make sure you are catching Cherax and not Euastacus. Please remember, all Euastacus freshwater crayfish are protected in Queensland under the Fisheries Act 1994 and Fisheries Regulation 2008, regardless of size. The catching or possession of these crayfish is totally prohibited so you cannot keep small ones as pets.
I’ll do an article on how to tell the difference between Cherax and Euastacus for those of you that don’t know the difference, so stay tuned.
Aquatic Biodiversity Survey and Baseline Mapping of Freshwater Crayfish and Aquatic Species of the Gosford Local Government Area
As Part of the Australian Crayfish Project and a sub project 100056 we have been conducting aquatic biological surveys the whole of the Gosford LGA. This project is major sponsored by Australian Aquatic Biological and receives sponsorship from Gosford City Council under their Ecological Research Grants scheme 2010. The project reached fruition in May 2012 with a total of ten aquatic biological catchments reports being issued to Gosford City Council.
The biological surveys were undertaken as part of both the broad Australian Crayfish Project (ACP) and Australian Aquatic Biological Survey (AABS) and a targeted sub-project on the Gosford LGA, Project 100056, Australian Aquatic Biological 2010.
Surveys of the Gosford LGA are completed on a catchment/drainage basis and a total of ten catchment areas were independently surveyed.
1 Wamberal Lagoon
2 Terrigal Lagoon
3 Avoca Lagoon
4 Cockrone Lagoon and Surrounds
5 Green Point to Kilcare & Bouddi NP – Coastal Streams
6 Erina Creek
7 Narara Creek 100056-7 Completed 67, 77, 78, 86, 87.
8 Point Clare to Mullet Creek
9 Mooney Mooney Creek
10 Mangrove Creek to Wisemans Ferry
This was a two year project that discovered much new information The primary aim of Project No. 100056 is to determine what freshwater crayfish occur where in the Gosford LGA. Primarily freshwater crayfish are the priority and the Gosford LGA represents a significant area for crayfish distributions, yet little is known on the distributions of crayfish in this area. Prior to the start of this research project only two species have recorded distributions within the LGA (Euastacus australasiensis and Euastacus spinifer) yet the extent of their distribution are unknown. Additionally, the area includes a number of coastal lagoons, lakes and streams all with independent catchments draining directly to the Tasman Sea that have been isolated from each other for millions of years and many containing unrecorded crayfish species.
The project also records information on all the other aquatic fauna found in the LGA as well as information on landforms and vegetation. All this is in order to facilitate the better conservation and management of the aquatic ecosystems of the Gosford LGA.
Note: For environmental and hygiene reasons (transfer of pests, diseases and weeds, etc.) each of the catchments are treated as individual systems and are surveyed separately with equipment and personnel being sterilized between catchments. A copy of our Hygiene Protocol and Code of Practice is available online at www.aabio.com.au
We managed to map the distributions of four freshwater crayfish species that occur in the Gosford LGA. Euastacus australasiensis, Euastacus spinifer, Cherax destructor and Gramastacus sp.
Australian Aquatic Biological P/L Report 100056-8 to Gosford City Council included a survey of Green Point Creek at Pearl Beach, NSW. The creek was surveyed at the crossing on Diamond Road.
Here the creek here was strongly flowing over a sandy stream bed. There were shallow areas and deeper holes. The banks had some rock retaining walls but were well shaded with ferns and palms, etc. The creek was extremely healthy with abundant aquatic species present. Some plague minnows Gambusia holbrooki were present, we observed a small long finned eel, several flat headed gudgeons, many striped gudgeons and common jollytails.
Further upstream at Tourmaline Avenue the creek was surveyed again, here the stream was again sandy based with deeper holes and looked in excellent condition. We surveyed the stream finding only dozens of striped gudgeons and surprisingly the White Cloud Mountain minnow Tanichthys albonubes. The White Cloud Mountain minnow is an exotic freshwater fish. It is a species that would normally be found in a fish tank so it is alarming that this exotic species is established in numbers within this stream. It is a robust species and a member of the carp family being a native of China. Their robust nature and bright colouration makes them popular as an aquarium species and they are not normally found in natural waterways of NSW.
I did some research on this species and found that, NSW DPI has known about this feral population since late 2002 and continues to monitor the situation. Unfortunately, one of the specimens collected was gravid so conditions were suitable for breeding which is a big worry. Discussions with residents in the area report Australian Bass and eels in the deeper holes and freshwater crayfish further upstream.
Discussions with the Australian Museum also record this species from Piles Creek at Somersby, NSW. We did a preliminary survey of this creek specifically targeting the White Cloud Mountain Minnow but were unable to find it. That does not mean it’s not there however, it does indicate that it’s not proliferating well and numbers are either very small or scattered, etc. Unfortunately, we did find invasive Cherax destructor proliferating in the stream so that was not so good news.