The New Zealand grayling (Prototroctes oxyrhynchus) is an extinct species of fish that was endemic to New Zealand. It was known to the Māori by many names, including pokororo, paneroro, kanae-kura, and most commonly, upokororo. The variety of names for the fish came from either multiple iwi, or to describe the fish at different periods of its life cycle. Even though this fish is named grayling, it is not related to the 'typical' or 'true' graylings of Europe and America (genus Thymallus), lacking the large dorsal fins true graylings are characterised by. It is, however, closely related to the Australian grayling (P. maraena). The New Zealand grayling was an amphidromous species, migrating between freshwater and saltwater during different seasons as well as stages in their life cycle. The last sighting of the New Zealand grayling was in 1929, and it was declared extinct in 2018.
Taxonomy The New Zealand grayling, previously part of the family Prototroctidae, is now part of the family Retropinnidae which contains smelts and graylings found in the southern hemisphere. Previously, smelts and southern graylings were classed into two separate families, Prototroctidae for graylings and Retropinnidae for southern smelts, however, now all six species under these families are classed in Retropinnidae. The fish is part of the genus Prototroctes, which contains two species, the New Zealand grayling (P. oxyrhynchus) and the Australian grayling (P. maraena). The New Zealand grayling likely diverged from the Australian grayling during the mid-Miocene, about 14 million years ago. Two slightly older fossil Prototroctes species, P. modestus and P. vertex, are known from the early Miocene-aged St. Bathans Fauna of New Zealand, exclusively from fossil otoliths. Their relationship to P. oxyrhynchus, the only Prototroctes to have inhabited New Zealand into historical times, is unknown, as the specimens of P. oxyrhynchus lack any otoliths due to their preservation methods. Two complete fossil skeletons of an indeterminate Prototroctes have also been identified from the mid-Pleistocene of New Zealand, and these could potentially represent fossil remains of P. oxyrhynchus.
Description The New Zealand grayling was a medium-sized fish which, when matured, measured between 30–45 cm (12–18 in) in length and slender in shape with the presence of an adipose fin. As an amphidromous fish, during their migration, it was found that graylings, originally silvery in colour, would darken to a grey or brown, and turn occasionally gold, while the underbelly remained light.
Dentition The dentition of the fish comprises a blunt and rounded snout, with the upper jaw containing a single row of long, blunt teeth that were situated close together forming a comb-like structure. The lower jaw, which contains another single row of smaller and sharper teeth, is slightly shorter than the upper jaw, and less rounded, forming a point that fits just inside the row of teeth on the upper jaw.
Diet The dentition and digestive system of the New Zealand grayling suggests the fish was omnivorous, feeding on both aquatic insect larvae such as caddisflies, and plants such as waterweeds growing on the rocks of riverbeds. The fish is suspected to have been herbivorous at times.
Distribution The New Zealand grayling was widely distributed throughout both the North and South Islands of New Zealand throughout the 1800s; however the range of the fish decreased to more isolated parts of New Zealand in the 20th century, such as some streams in the East Cape, Wairarapa and Otaki districts on the North Island and on the west coast of the South Island. It was found in freshwater rivers and streams during autumn and winter, and migrated to New Zealand's surrounding seas in early spring. The fish is believed to have spawned in freshwater rivers before migrating to the sea and returning to freshwater to reproduce.
History The New Zealand grayling was often hunted by Māori. A traditional way the Māori people hunted the New Zealand grayling was by using a basket trap known as a hīnaki, lodged in a river to capture fish swimming downstream. The traps were often left overnight, so by morning, fish that were guided into the trap by the mānuka brush walls would be caught at the top of the tapered "V", not being able to swim back against the current to avoid being caught. This method of catching the fish was effective as it allowed dozens of fish to be captured at a single time. Another method involved two parties, one group startling the fish by beating the water with sticks, and another waiting downstream with nets. The fish was abundant in the 19th Century. It was prized by early European settlers, unlike many other, and it became a sporting fish. Hundreds of graylings were often caught at once. The first declines in fish numbers were noted in the 1870s, and by the 1880s the New Zealand grayling was no longer found in most rivers. The population decreased so much by the 1900s that shoals would be reported on in newspapers. The last confirmed sighting of the fish being in 1923, when Peter Buck asked Māori living in the Waiapu Valley to teach him traditional fishing methods. In 1951, some years after the last sighting, the species was given full legal protection by the Freshwater Fisheries Regulations. It is the only New Zealand native freshwater fish ever to be protected. In August 2018, the New Zealand Department of Conservation classified the New Zealand grayling as "Extinct" under the New Zealand Threat Classification System.
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