First record of male freshwater eels (Anguilla dieffenbachii) caught at sea

Study Extent

South Taranaki Bight

Sampling

On 22 April 2014, two A. dieffenbachii were caught in the D'Urville Sea Valley, South Taranaki Bight, by a commercial trawler; the centroid of the trawl shot, 40 22’S, 174 03E, was 36 km NNE of Stephens Island (Marlborough Sounds), and 98 km West of Foxton Beach. The trawl (116 m opening, 60 m height, 108 mm codend mesh) was deployed at 2140 h on 21 April and retrieved at 0600 h the following day. The average bottom depth was 122 m, but as the trawl fished mid-water, the actual depth of capture is uncertain. The eels were noticed by Ministry for Primary Industries onboard observers who froze them prior to forwarding to the Museum of New Zealand, Te Papa Tongarewa, for confirmation of identification.

Method steps

1. When thawed, one eel measured 608 mm TL and 474 g, and the second 648 mm (but was not weighed). Both eels were identified as A. dieffenbachii from external features (body shape, colour, insertion and length of the dorsal fin and pattern of vomerine teeth), while examination of the gonads confirmed they were males. As they were catalogued as museum specimens, it was not permitted to make incisions and remove both testes, so no gonadosomatic index could be calculated. The eye indices (vertical x horizontal diameter; Todd Citation1981b) were 9.36 and 9.88 mm2 respectively; the average index for silver longfin male eels of similar lengths at the start of their seaward migration would be 9.2 and 10.26 mm2 respectively (calculated from the eye index/total length relationship given by Todd (Citation1981b)).

New Zealand Longfin Eel

1. Anguilla dieffenbachii
   common name: New Zealand longfin eel, ōrea rank: species

South Taranaki Bight, New Zealand