Guide to mesopelagic fishes of the southern Tasman Sea

Summary

This photographic guide to the mesopelagic fishes of the southern Tasman Sea is based on catches made during a program of bioacoustics and net sampling in the abyssal basin between New Zealand and Tasmania. The guide presents photographs and key diagnostic characters for 143 midwater fishes in 43 families. DNA barcoding was used in conjunction with existing published taxonomic keys and traditional morphometric methods to identify species where possible, and to differentiate “observable taxonomic units” (OTUs) where confident species identification was not possible.

The aim of this guide is to help non-specialist researchers, students and fisheries scientists to distinguish families of the dominant midwater fishes collected in trawls in the region, and to identify species where possible. We provide a brief introduction to deep-sea pelagic habitats in the southern Tasman Sea and illustrate the extraordinary diversity of fishes inhabiting this zone.

Mesopelagic fishes are notoriously difficult to identify, creating a problem for standardisation in even high- level identifications presented in non-taxonomic works. This problem is exacerbated if specimens are damaged during collection. This guide attempts to strike a balance between presenting photographs of specimens that were collected in good condition, while also giving the reader a realistic impression of normal specimen quality achieved from trawls. This way, diagnostic characters that are applicable to trawl-caught specimens are given and notes or photographs are given where there are particular diagnostic characters that are only visible on specimens in excellent condition. This guide cannot encapsulate or replace the large body of taxonomic literature available on mesopelagic fishes, or the taxonomic expertise required to use that literature. However, we hope to facilitate standardised reporting of mesopelagic fish catches and to engender an appreciation for the biodiversity values of the deep-sea pelagic zone.