This is a story about a big extension on the range of Uraspis secunda, or cottonmouth trevally, caught off the coast of Perth, Western Australia. The unusually strong Leeuwin current in 2011 seems to have pushed many pelagics and northern warm water species further south.
Date specimen collected: 17 March 2011 (I think). Location: FAD approximately 20km west of Rottnest Island Name of FAD: Possibly Fremantle sailing fad Depth: approximately 200m Fishing method: free diving with rubber powered spear gun
Anecdote: The weather was good so we decided to do a spear fishing trip (organized by Dstick) to the FADS in search of Dolphin fish (mahi mahi). The Leeuwin current has been particularly strong and a friend caught a state record dolphin fish the week before. We entered the water about 11am after having motor problems on the way out and spent a few hours looking for big dolphin fish, but only small dolphin fish were about.
I observed two trevally and 5 leatherjackets staying in close to the FAD itself, the leatherjackets generally staying within a 4m perimeter of the FAD and in the top 2-5m of the water column. The trevally would generally stay within 3m of the FAD and never rise above 5m in the water column. Every time the trevally were approached however they went to around 15m depth and only returned close to the top 5m of water after leaving. I’d never seen any trevally like this before so decided to shoot one and keep it for identification purposes as it was just so unusual. One guy even thought it was some sort of luderick as it had similar ludrick shaped bands on it. The pectoral fins however definitely identified it as a trevally species.
No large Dolphin fish were about so I decided to sneak up as far as possible on one of the trevally and take it. I speared the biggest trevally (612g) a bit low around the belly region but it held true and was humanely dispatched using the iki jimi method with a dive knife. I threaded the fish onto my float line and when passing the float line through the gill cavity and part of the gills were ripped off and drifted away.
The specimen was stored and compared with Fil-O-Fish which seemed to identify it as Uraspis uraspis, however there was no record of Uraspis secunda in this book. After contacting Mark McGrouther from the Australian Museum it was positively identified as a Uraspis species but without a microscope it was hard to distinguish between U. uraspis or U. secunda. Sue Morrison, curator of the WA Museum has identified the species most likely as U. secunda. The specimen is now in the care of the WA Museum. Cheers, Cameron Moir - Schaffer Loaders