The taxonomy of estuarine and brackish‐lake <i>Retropinna</i> from New Zealand (Galaxioidei: Retropinnidae)

Abstract

Abstract Retropinna osmeroides Hector 1871 (which is a growth fonn of R. retropinna ), R. media Stokell 1969, and R. diversa Stokell 1969 are shown to be junior synonyms of R. retropinna (Richardson 1848), which is thus the only coastal species of Retropinna in New Zealand. R. retropinna is sexually dimorphic, males having larger fins than females and a deeper abdominal keel. Reports that “nuptial tubercles” are present only in the male are found to be erroneous; ripe fishes of both sexes possess tubercles, although they are more prominent and widespread in the male. Fishes from the marine and estuarine environment exhibit clinal variation, with latitude and estimated mean air temperatures, in their number of vertebrae, head length, eye dimneter, and predorsal length. Brackish lake populations have fewer vertebrae than diadromous ones. R. retropinna probably spawns in spring and summer, having many small eggs. Spawning is thought to be either in estuaries or lowland rivers; larval life is marine. The fish mature usually at two years, a few not maturing and some surviving to spawn at three years. R. retropinna is found in lowland streams and rivers throughout New Zealand, penetrates long distances inland in some rivers, and occurs on the Chatham Islands.