Reproductive biology of the clingfishes (Gobiesocidae) from the Wellington south coast

Abstract

The reproductive biology of seven intertidal species of Gobiesocidae (Trachelochismus pinnulatus, T. melobesia, Dellichthys morelandi, Haplocylix littoreus, Diplocrepis puniceus, Gastrocyathus gracilis and Gastroscyphus hectoris) was studied and compared during 1981, 1982 and 1983. Samples were collected from Island Bay, Reef Bay and Te Raekaihau Point on the Wellington south coast. Information on the age, length-weight relationship, size at maturity, relative condition, reproductive periodicity, reproductive histology, fecundity, sex ratio, reproductive behaviour and sexual differentiation was obtained from field and tank observations as well as detailed measurements, dissections and histological studies. All species are short-lived (2-4 years maximum age) and spawn at about one year of age. The spawnings are seasonal, occurring from late June to early January with the timing and duration varying between species. Histologically the cycles of oogenesis and spermatogenesis are similar in all species but the eggs of clingfish differ from those of most other fish in having filamentous adhesive discs. Ecologically these clingfish species are either lithophils which live and spawn on stony substrates or phytophils which live and spawn amongst algae. The lithophilic clingfish (T. pinnulatus, T. melobesia, D. morelandi and D. puniceus) are more fecund for their size than the phytophils. They lay larger egg masses, usually with more than one female contributing, and these masses are guarded by the males. The phytophilic species (G. gracilis, G. hectoris and H. littoreus) while being less fecund for their size, have a lower ratio of males to females (1:3) in the sampled populations than the lithophils (1:1). Each female phytophil lays its eggs either in one place or in many small masses and these are not guarded. Another difference between the lithophils and the phytophils is that the phytophil males possess a pair of distinct adipose bodies in the region of their kidneys. Differences in reproductive biology and behaviour correspond to differences in habitat and spawning sites. These results show that the New Zealand clingfishes are reproductively diverse. This diversity occurs along ecological and not taxonomic lines.