Something Fishy - Ribbonfish stranded in Wellington
Strong westerly winds during spring sometimes bring oceanic fishes into shallow bays and harbours. One example is the ribbonfish.
On November 6, Nick Clarkson (Te Papa) reported a large silvery fish in distress off Oriental Bay in Wellington Harbour.
We went to investigate and found it lying in about 1m depth among the kelp. On examination it was discovered to be a ribbonfish, Agrostichthys parkeri, a member of the same family as the oarfish (family Regalecidae).
The fish was barely alive and in bad shape, with the tail eaten off and its fins broken. Estimating the lost end to be about 20cm, the complete specimen was just over three metres long.
Unlike the globally widespread oarfish, the ribbonfish is restricted to cool surface waters of the Southern Hemisphere. In our waters it has been recorded in an area bounded by the Challenger Plateau, Auckland Islands and southern Louisville Ridge. Several specimens have been beach-cast in the Wellington region and two were collected by spear fishermen.
Both the ribbonfish and the oarfish share a number of distinctive features. They have scaleless skin covered with raised dimples and a silvery colour that is easily rubbed off. Both have a mouth that is protruded like a john dory and are very fragile so break easily when lifted out of water. The main differences between the two are that the ribbonfish is much more slender, lacks dark markings on the silvery body, and the rooster-like crest on the head and elongate pelvic fins are absent (see photo). Small specimens up to 60cm long have some elongated dorsal rays and diffuse dusky markings, but these are rapidly lost as the fish grows. The upper head profile is also lower (~45º) whereas the oarfish head profile is almost vertical (~90º).
Virtually nothing is known about the biology of this rather secretive fish. The silvery colour acts as camouflage in the pelagic environment by reflecting light at the same wavelength as the water around it. Large eyes show that sight is important, and the lateral line running close to the ventral profile is characteristic of many species of surface-living fishes (e.g. flying fishes and garfishes).
The largest ribbonfish ever recovered was 307cm TL, beach-cast at Napier in October 1993. This specimen was a mature female, and it was shedding pale amber eggs 4 mm in diameter. Ribbonfish may also possess an unusual defence ability: two people who handled a 53cm live juvenile reported experiencing small but distinctive electrical shocks. However these were not experienced with the present badly-damaged specimen.
Elsewhere thought to be a rare species, this latest capture brings the total number of ribbonfish held in the National Fish Collection at Te Papa to 51 specimens. Please keep alert for unusual strandings as well as strange fishes you may catch - we will give a book on fishes for specimens registered into the NFC.
Museum of New Zealand Te Papa Tongarewa
Something Fishy is a monthly article prepared by fish section staff of the Museum of New Zealand reporting on amateur catches of particular interest to scientists, especially species which are rare or difficult to identify.
Museum scientists are always looking for specimens of rare or unusual fishes. We shall be happy to provide identifications in exchange for specimens. Seal specimens in a plastic bag with a label inside recording name, address, capture and location details, then wrap in newspaper, box, label "keep frozen", freeze, and send collect via Hall's Refrigerated Transport Ltd. to: Dr Clive Roberts, Museum of New Zealand, 169 Tory Street, Wellington.
Phone (04) 381-7311. Fax (04) 381-7310.• E-mail: firstname.lastname@example.org