New Zealand's “mystery fish”, the grayling (upokororo of the Maori) was extremely abundant in many rivers and streams until late last century, but from 1870 onwards it declined rapidly in numbers until in 1920 it occurred in only a few isolated localities. Very few have been recorded since then. Several theories have been put forward to explain their disappearance: that the early settlers over-exploited them (vast numbers were taken out of some rivers); that destruction of the bush in some way adversely affected their river habitats; or that the introduced trout proved too successful as a competitor. Grayling reach 12 in., occasionally 18 in. in length. Silver in colour when they enter rivers from the sea, they later darken to a greyish brown, sometimes becoming almost golden. Few details are known of their life history. Formerly they migrated up rivers in large shoals in late summer, spent the autumn and early winter up-stream (perhaps spawning), then disappeared again in early spring, presumably returning to the sea. The early Maoris used basket traps to catch the upokororo in large numbers as they ascended the rivers; large fish were called tirango; small fish, repe. “Grayling” is a misnomer for this New Zealand fish, which is not related to the European or American grayling, but belongs in a separate family with one other Australian species.
by Lawrence James Paul, B.SC., Fisheries Division, Marine Department, Wellington.