Swimming crab – Ovalipes catharus – often called Paddle Crab, also Papaka
Often called paddle crabs. The width of the carapace of males is 150mm and 115mm for females. The males are heavier bodied and usually a bit darker in colour. When viewed from underneath the abdomen of the males are much narrower. The colour of swimming crabs is grey/brown with orange/brown spots. The carapace and legs are smooth to the touch. The most obvious difference between swimming crabs and other crab species is that the two back legs are flattened into paddles. In both sexes, there are five spines on each lateral edge of the carapace.
There are also 4 darker coloured spots on the carapace; two near the back, and two towards the front.
The female swimming crab lays up to 750,000 eggs and can do so up to three times per year.
There has been a big increase in the numbers of swimming crabs in some localities since 1970. This may well be a result of overfishing of species like rig sharks and other fish which prey on paddle crabs. Paddle crabs also make good bait for some fish species that prefer shellfish and crabs instead of fish fillet cut baits. Whole swimming crabs, and other easily caught crabs, or parts, make good bait for moki, rig sharks, and elephant fish.
At times swimming crabs can be a huge nuisance to surfcasters. If you reel in your line soon after casting out only to discover your bait gone then suspect swimming crabs to be the culprits. Every now and again a swimming crab will be accidentally hooked by surfcasters. I have found that if you suddenly strike hard on your surfcasting rod you are more likely to hook one. The hooks don’t always pierce the shell but instead snare one of the crab’s legs.
Paddle crabs are very good eating. They are almost identical in taste to rock lobster; if anything they are sweeter. Swimming crabs are commercially caught in pots, set nets and seines. You can take swimming crabs from wharves and piers using a baited net stretched across an old bicycle wheel raised and lowered by a rope.
It is possible to target swimming crabs by threading a dozen 3/0 treble hooks onto a length of heavy mono and connecting a sinker at the end. After baiting the hooks cast it out with your surfcasting rod. Wait five minutes then strike hard on the rod and keep a tight line while winding in. With luck, you will be able to catch a few good sized swimming crabs by this method.
They are present all around New Zealand mostly from low tide level out to about 10m but are found as deep as 100m in some areas. Though more abundant around the North Island they seem to grow to a larger size around the South Island. Paddle crabs burrow into the bottom backwards so that only their eyes are showing above the seabed. Paddle crabs eat shellfish like pipi and tuatua.
Watch out for the pinchers of swimming crabs as they can deliver a painful nip.
Paddle crab is excellent bait for rig and moki. Small ones can be used whole, but larger crabs should be cut in half or into quarters, and tied on the hook with bait elastic.