beach

Whanganui River Mouth – Te Kai Hau ā Kupe

Where a river meets the sea is a place of great fascination to people all over the world. It’s usually a place of great abundance for fishing as well as gathering whatever interesting wrack gets washed down the river and cast up onto the shore. If the river is large enough it becomes an entrance for shipping or boating, with all the consequent dangers associated with channels, rips and sand-bars.

The Whanganui River entrance has been shaped and changed by major human intervention from its original form. When we at look at old photographs or paintings of the river-mouth, what we see is very different from what is there today.

The building of channel-protecting moles on either side of the river entrance completely transformed, not only the river mouth, but also the coastal area to the west. Interrupting the longshore current that flows from west to south east causes the suspended sand to gradually accumulate against the obstruction. This has created expansive sand-dunes at Castlecliff and has moved the shoreline steadily seawards.

 

1. Castlecliff photo

 Whanganui River Mouth, Castlecliff Beach; Frank Denton, 20th century.  Ref: 1802.1016

One early image of the river mouth is a photograph of Castlecliff Beach by well-known Whanganui photographer Frank Denton. You can see beach visitors enjoying a stroll on the sand. The beach stretches around a natural curve at the river mouth and the sea-swell washes into the river. Ladies lift the hems of their long dresses over the wet sand while children play and paddle in the shallows at the edge of the river. In the far distance a line of surf marks the edge of the sea.

A set of three small watercolour paintings by itinerant artist Christopher Aubrey show the river mouth prior to the construction of the moles. Although the paintings are faded and damaged by long exposure to light and damp, all the details are still visible. Each painting depicts the curve of the river towards the entrance at different times of day. Looking closely, we can see that in 1894 there was a significant sandbar, indicated by a thick line of surf across the across the river entrance. The line of surf across the river-mouth ends at a sand-spit that stretches out from a large cliff on the Castlecliff bank of the river.

Along the river margin stretched a beach with a gentle sloping edge, forming a useful pathway for riding horses or for herding a flock of sheep to the freezing works in the background. The Wanganui Freezing Works were established in 1891 to process the farm animals produced in the surrounding rural areas and freeze them for transport out of the region by ship. The paintings also show ships berthed in the river adjacent to the freezing works, a large ship anchored just offshore and a small vessel crossing the sandbar.

Despite the better shipping channel created by the construction of the moles, the difficulty of negotiating the sand-bar and surf have resulted in a number of shipwrecks over the years, including the Port Bowen which, in 1939, ran aground on a sand-bank, fully laden with a cargo of mutton and lamb from Whanganui destined for export to England.

With the proposed development of Whanganui Port it will be interesting to notice and record further changes to the landscape of the Whanganui River mouth and see how future sea-going vessels manage the difficulties of “crossing the bar”.

 

Margie Beautrais is the Educator at Whanganui Regional Museum

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Seashore Critters

The beach may be a nice place to visit, but you wouldn’t want to live there. Windy, hot, dry, barren and occasionally flooded by seawater, it’s a hostile environment for small animals. And yet there are some species that manage to make the beach their home. I spent a day at Mōwhanau recently with children from Brunswick School, turning over driftwood and logs and looking for interesting critters.

1. hopper

A common beach sandhopper (Bellorchestia quoyana), when examined closely, reveals its crustacean nature.

Photo: Crispychipp / Wikimedia Commons CC-BY-SA

Sandhoppers are the most abundant denizen of the beach. Under every piece of driftwood or seaweed is a multitude, which spring away or scurry down burrows when disturbed. These little creatures, properly known as amphipods, are actually crustaceans, not insects. They are cousins to crabs, crayfish and even the slaters in your garden. Like all crustaceans, they breathe through gills which they have to keep moist. Most of the roughly 10,000 species live in the sea, but amphipods can be found in any damp environment. Some Southern Hemisphere hoppers even live far from the coast in forest leaf litter.

2. log

A log, like this one found on Mōwhanau Beach, is like a tiny oasis, providing shelter and food for a whole community of invertebrates
Photo: Whanganui Regional Museum

 

On the beach amphipods burrow down to damp sand during the day and come out at night to feed on anything the tide has washed up. Close up, they resemble tiny humpbacked shrimps, ranging in colour from dark grey to pinkish-orange, and have powerful hind legs for jumping. Sandhoppers are an important part of the beach ecosystem, not just as food for larger animals, but as scavengers that break down seaweed and carry those nutrients as deep as 30 cm into the sand.

Another creature found under beach logs is the native seashore earwig (Anisolabis littorea). These are flightless, and much larger than the introduced European earwigs in your garden. Their Māori name, matā, is also the word for obsidian – black volcanic glass – because they’re similarly shiny and black.

Seashore earwigs are omnivores, feeding on seaweed or catching amphipods with their nippers. Unlike most insects, they take good care of their young; after mating, the female drives off the male and guards her clutch of eggs and helpless babies. Once the baby earwigs get large enough to fend for themselves, all bets are off. They can flee the nest, eat each other, or eat their mum (and she’ll happily snack on them if they try). Female matā have long straight nippers while males have curved asymmetrical ones.

3. earwig

The native seashore earwig or matā (Anisolabis littorea) is a beautiful glossy black creature found under beach debris all around Aotearoa
Photo: Lisa Bennett / NatureWatchNZ CC-BY-NC, with permission

Although they look fearsome, curving their pincers over their back like a scorpion, I’ve handled earwigs for years and never been nipped. The kids from Brunswick School were initially cautious, but when I showed them how you can gently let a big coastal earwig crawl from hand to hand, they all wanted to try.

The “ooh yuck!” response when presented with a creepy-crawly is not innate in children, but learned from their parents, peers and authority figures. There are native invertebrate species going extinct right now. Voters don’t care because bugs are “yucky”. Museums like Te Papa and Puke Ariki are putting on insect exhibitions to help fight this perception. If we adults are frightened of harmless little insects, it’s not the insect’s fault. We need to get over our irrational fears, model good behaviour for kids, and, on our next visit the beach, turn over some logs with them and see what we find.

 

Dr Mike Dickison is Curator of Natural History at Whanganui Regional Museum.