Ready for a swim?
- Admin
- 4 days ago
- 3 min read
There are good news for those keen on jumping into Ōhiwa Harbour’s waters this summer. In early November the first of the weekly tests carried out over summer confirmed the water quality at the Ōhope boat ramp is ‘good’. This mirrors the great majority of the 113 samples carried out over the last five years. In 94 per cent of times the water quality was rated ‘good’, in only 3 per cent caution was advised and in 4 per cent of samples, all of which were taken in the high rainfall year of 2022, the area was deemed unsuitable for swimming.
During the swimming season from around November/December to February/March, regional and district councils, along with public health agencies, assess the health risks from faecal (‘poo’) contamination at swimming spots. Toxic algae is also regularly monitored at some river and lake sites. Land, Air, Water Aotearoa (LAWA) displays the results of the recreational monitoring on their website. LAWA checks for new data regularly throughout the day, and ensures we have the most up-to-date information on the water quality at swim sites across Aotearoa New Zealand.
As the five year sample data shows, water quality can be low after rainfall. LAWA and public health authorities recommend to avoid swimming for two to three days after heavy or prolonged rain regardless of the health warning status. This is because the water can be contaminated by farm and urban run-off which takes some time to settle out or flush away. They also warn not to not swim if you suspect an algal bloom is present.
One to watch out for: Asian paddle crabs
While any sizeable sharks and the stingray chasing orca are only rare visitors to the harbour it pays to watch out for the Asian paddle crabs. They are very capable swimmers and aggressive defenders of their territory making it a fierce competitor for native crabs and potentially giving humans a nasty nip. The first two were found in Ōhiwa Harbour in February 2020. They are not as widespread as in some other northern harbours but an ongoing trapping programme is carried out in both the Tauranga and Ōhiwa Harbours to monitor the new intruders.
Asian paddle crabs are relatively large swimming crabs with paddle-like hind legs. Adults can reach 12 cm across and are covered in small hairs which are not always visible. Other identifying features are six spines on each side of the outer shell; a shell colour ranging from olive green to chestnut brown and five spines on the upper surface of each claw. They love the sub-tidal areas to depths of about 15 m, typically in estuaries where there is firm sand or muddy fine sand. They are predators that feed mainly on shellfish, crustaceans, fish and marine worms.
Harbour users are encouraged to keep their boats clean and also keep an eye out for Asian paddle crabs. If the pests are discovered, they should be killed on site and reported to Bay of Plenty Regional Council via 0800 STOP PESTS (0800 786 773). It is illegal to move living pest crabs.
More information
‘Asian Paddle Crabs’, Bay of Plenty Regional Council,
The Marine Biosecurity Porthole New Zealand has published a quick guide to identify these crabs and distinguish them from other, native crabs:
