Leigh Intrigue – How Did It Get Here?


By John Anderson with Introduction by Bob Rosemergy

John Anderson writes….

Last summer, someone saw a fish they didn’t recognise. It happens all the time of course, and people soon get shy of shooting something simply because they didn’t know what it was, and dealing with the ribbing their mates give them when they pull a bluefish or green wrasse over the gunwales of the boat. But Graham Hope is an experienced diver and a good observer so his sighting of a black and white banded, deep bodied fish that was sort of ‘Maomao-ish’ was odd. Invariably, sightings by knowledgeable divers of queer fish either turn out to be some deep water ‘oogly’ that found itself in the shallows or a subtropical species that has drifted down to New Zealand on the warm summer currents as a juvenile and has grown on here. The vast majority of these subtropical vagrants get snuffed out by winter’s chill so these types of sightings are of small fish, maybe 100mm long, in their first and possibly last summer here. Graham’s fish was described as about 300mm long so presumably several years old. The deep water refugee line of enquiry went nowhere either, as the vertical black and white stripes clue narrowed the search down to only very few possibilities, all of which he rejected. A mystery then and without a photo, or even better, the fish itself, was one unlikely to be solved.

Fast forward nine months and we were diving in the same location. On pushing off the sand and turning to check there was no great white shark behind me (don’t pretend you don’t do it yourselves), the maomao bolted and with them, right at the edge of visibility and also bolting, was … something?

I pride myself on knowing my fish even the odd ones and I thought back to Graham’s sighting and pondered. So I began to dive the same spot, repeatedly, half doubting that I hadn’t just imagined it but figuring it was worth 20 minutes.

Just on deciding to give up six or eight dives later, Kolt moseyed past and asked why I was stuck in one spot, to which I answered I was hunting a particular fish and explained.

‘Oh, I think I saw what looked like a black and white striped black angel fish right here a few dives back!’ confirmed Kolt.

That steeled my resolve. It was game on, today the mystery gets solved.

Two dives later from out of the back of the school of maomao it came. Heading straight on, I have to admit I still had no idea what it was but when it turned, its facial profile is unmistakable; Knifejaw. I pulled the trigger.

Later, it took Kolt Johnson a few minutes googling to answer the question categorically.

Oplegnathus fasciatus

, the barred knifejaw. Very odd indeed because he is not a deepwater oogly, nor is he a sub tropical wanderer lost. No, the barred knifejaw is a north Pacific shallow reef generalist, native to Japan, Korea and Taiwan.

It begged the question: How did this fish find itself 9,000 kms from home, in more or less the right sort of environment on the wrong side of the world?

He definitely didn’t swim here. A quick google provides the most likely answer because barred knifejaws seem to be developing a nasty habit of showing up a long way from home and that hasn’t gone unnoticed. Two showed up in the Mediterranean and half a dozen on the west coast of America. They are hitchhiking on ships. ‘In ballast water,’ I hear you shout but no, probably not. Surviving in ballast water for five, six or whatever weeks it takes to get from Asia to here is the preserve of the lower animals, invertebrates and whatnot. It’s a pretty shitty environment in there and you need to be the larvae, egg or very small version of an animal that’s as tough as old boots to get out of there alive.

Much more likely is in the ship’s sea chest. A sea chest is a recess, maybe the size of a small room in the largest of ships, built into the hull from where the ship draws its cooling water. To stop sticks and weed and rubbish getting up the intake pipes that feed off the sea chest it has a grill across the front. You can quite imagine some small fish setting up shop in there while the ship sits in port in Korea for a couple of weeks and deciding to stay when the ship departs. In fact, if he’s grown too big to fit back out through the mesh, he mightn’t have a say in the matter! He’d be stuck in there for life if sea chests weren’t also the ideal place to smuggle, oh, I don’t know, tonnes of cocaine?

When the ship reaches New Zealand, the good folk at Customs sometimes take an interest in what might be concealed in the sea chest and see fit to send some divers over the side to remove the mesh and take a look inside. And so our little friend might come to find his freedom in his new home. Okay, mostly the sea chest grill is removed simply for servicing reasons, maintenance of the cooling systems etc but I like to think our voyager was involved in something more than a little shifty. In support of my theory, I’d like to offer up that if he gained his freedom in a mundane maintenance process, he should right now be residing under a wharf at Marsden Point or Auckland Port rather than on a headland at Leigh Harbour having been liberated by smugglers who somehow offloaded their stash before berthing in Auckland. Okay, I’m clutching at straws here but it’s a mystery and I like mysteries.


STOP PRESS … Update from Ministry of Primary Industries (MPI) on dealing with similar finds …


The person who’d speared the unusual organism (fish in this case) should refrigerate it, photograph it and contact MPI on the pests and diseases hotline – 0800 80 99 66. The marine incursion investigator would then look into it, provide further advice on shipping the fish to MPI (should that be required) and would also provide the notifier with information about what it was.

Any unusual sea life should be reported to MPI on 0800 80 99 66. It is helpful if fishers or divers capture photos or take samples if they can, and carefully note the location

Also … MPI advise that transport via sea chest is indeed the most logical and likely explanation for how an Oplegnathus fasciatus ended up in New Zealand. Fish do get relocated via sea chests, but it’s not known to be a common occurrence. When it does happen, the fish tend to be few in number (say, one – three individuals)

The movement of fish species via sea chests appears to be an infrequent event that involves low numbers of individuals, and MPI believes it’s unlikely that there are significant numbers of non-indigenous fish introduced to New Zealand waters in this manner.

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