Sharks - Bronze Whalers

Way back in the '70s diving and spearfishing was at its bubbling best. And a lot of spearos from that time regularly encountered sharks. Especially at places like the (now protected) Poor Knights islands. Bronzies they mostly were, feisty medium-sized fish averaging around two metres in length: sharks very keen on removing fish from the end of a spear or a trailing float.

Eventually, many of these divers moved on from spearfishing. As they did so underwater sightings of bronzewhalers became increasingly rare. Most attributed this to the fact that they weren't dragging bleeding fish around the ocean any more. But some noted that friends who were still keen spearos were also not having bronzewhaler encounters like they did in the 'old days'. It was suggested that perhaps all was not well with bronzewhaler population.

Around this time yours truly began his second period of education on the biology and life history of bronzewhaler sharks. The first installment of my 'bronzie education' had started innocently enough. This was as the wide-eyed grand nephew of a captivating character known as Bill Brambley who, along with his family, farmed land and fished the sea on and around the south head of the Manukau Harbour. They caught large sharks in waters the farm overlooked. You may have read of their exploits in The Sea Cockies Of The Manukau by Mavis Brambley. Big bronzies hooked on forty-four gallon drums and lengths of chain a mere stone's throw from the beach made for exciting times.

Kelly Tarlton's Underwater World took me back there. We caught big bronzies (and other sharks) in the shadow of the old Brambley homestead and learnt much about all the sharks that frequent this amazing harbour. Most of the bronzies encountered were large pregnant females looking for a place to drop their young. They were not suitable as aquarium animals. Preferred were school sharks (tope), sevengills, spotty dogfish, and smaller medium-sized bronzies. The latter were the hardest to track down. These were beautiful sharks: their flanks glowed with a polished copper sheen and a distinctive steel grey stripe ran from nose tip to gill openings. On the underside their pectoral fins had noticeable dusky tips and their noses were notably pointed rather than round. Their whole demeanour spoke of a speedy predator rather than a cruising opportunist.

At the time I questioned whether these were just juvenile features or whether they might be a different species from the normal garden variety of 'harbour' bronzewhaler, but the texts I had at the time weren't up to the task of answering. They mentioned only the well known Carcharhinus brachyurus. I left it at that.

Time passed and eventually an excellent title on the identification of sharks and rays came my way: Sharks And Rays Of Australia by PR Last & JD Stevens. Inside was a description of a species of bronzewhaler, recorded from northern New Zealand, that looked very similar to Carcharhinus brachyurus, our typical 'harbour' bronzewhaler, but also distinctly different. The excellent plate drawing in the back of the book stirred old memories and activated long forgotten neurons. Quickly I dug up as many old bronzewhaler photos as I could get my hands on. All were inconclusive. One or two of the sharks I had photos of looked suspiciously like this 'other' species of bronzewhaler (Carcharhinus falciformis) but the vagaries of my photographic ability meant that no firm conclusions could be made. Once again, I let the issue slide...

Then local Bay of Islands taxidermist, Kevin Flutey, encountered some bronzewhalers off Bird Rock in the middle of this hot La-Nina summer of 1999. Kevin had been fishing in the game club's Small Boat Contest and had chosen to berley for sharks. Now Kevin is no novice to shark fishing - it is his passion - and he is unquestionably good at it. On this day, however, Kevin was having trouble tracking them down. They were not in the blue water off Ninepin Rock and they were not off Piercy Island. Eventually, he found a bunch of bities in shallow reef country quite close to the Bird. What was more surprising was that they were not the expected blue sharks and makos but bronzewhalers. Kevin described four or five bronzies circling the boat at one time. Sizes of the individual sharks ranged from a metre long right up to the two metre-plus fish he landed and later weighed-in at one hundred and sixteen kilos.

What was unusual was that this was a pack of bronzies in the Bay of Islands: waters where the harbour bronzie (Carcharhinus brachyurus) is not that common. Sure, they are caught up the Waikare estuary in summertime, and in some of the big bays and inlets, but are never described as being 'frequently encountered' not like they are in the Hauraki Gulf, and those big west coast harbours. To encounter a pack of them at Bird Rock could be deemed unusual; quite enough encouragement for an ichthyophile like myself to prick up his ears and take note.

Unfortunately, I missed the weigh-in. A few days later, though, I managed to get myself to Kev's place with shark book in hand. A quick examination of the photos Kev had developed told the story: he had in fact caught a silky shark or bluewater bronzewhaler (as some like to call them). This was a shark, according to the text, that preferred coastal areas washed by warm oceanic waters and was most common in seas warmer than twenty-three degrees Celcius. This made the shark a La-Nina shark: commonest in those years when La-Nina weather conditions deliver large quantities of warm blue water to our shores.

To this end I suddenly realised why those old divers had so many shark stories from the 'old days'. The seventies were noted for having a number of consecutive La-Nina years in the one decade. Parts of the eighties and much of the mid-nineties were more El-Nino oriented with less abundant blue water flows inshore. Herein lay the answer to the varying levels of bronzie encounters reported by divers over the years. The numbers of bronzewhalers being encountered was being influenced, in part, by the vagaries of the warm currents that flowed by Northland each year. Now it was 1999, La-Nina was once again in full swing and the blue water bronzies were back!

My somewhat belated discovery of this fact threw some shark conservation issues into the air. When people worried about excessive bronzie captures they needed now to account for the two different species. It has already been widely proven that the inshore populations of bronzewhaler are under stress (mostly thanks to their propensity for drowning in flounder nets) but what about the offshore species? Drift netting would have hammered them (again during those years that divers reported them scarce) but with drift netting now supposedly pushed back into pirate waters maybe this oceanic variety of bronzewhaler is making a comeback.

Many more questions remained unanswered. I wondered about those little bronzies we'd encountered in the Manukau all those years ago and what mix of bronzie captures in the north are made up of which species. I have examined as many bronzie photos as I can get my hands on (not a lot) and discovered that people like Paul Embling have been catching bluewater bronzies off ledges with marlin potential and harbour bronzies in, well...harbours! But I'm still fascinated by the scope and range of the two species; what their distribution is in this country, and how their different behaviour relates to the environment they choose to live in (the bluewater bronzie has already been suggested to be a pack animal that hunts in small schools).You can rest assured it is something I'll be paying very close attention to in the future.

Identifying a 'pelagic bronzie' 

Both bronzewhaler species have a similar size potential, so don't be fooled by size alone, or the place that you encounter your bronzewhaler. 'Harbour' bronzewhalers can be found well offshore, and I'm sure that 'bluewater' bronzewhalers venture right into shallow warm waters. But a 'harbour' bronzewhaler has a lower temperature tolerance so is more likely to be caught in mid-winter over a hapuku ground than a bluewater bronzie, and further south.

The fastest way of telling them apart is to look at their anal fin. The bluewater bronzie (Cacharhinus falciformis) has an anal fin with a noticeable 'hook' in it. This differs from the harbour bronzie's anal fin which is squarer in profile. However, this is not a diagnostic feature and can't be relied upon. To differentiate these two similar looking sharks exactly you must measure the length of the inner margin of the second dorsal fin and determine where the origin of the first dorsal fin occurs in relation to the free rear tip of the pectoral fin (this is the rear-most portion of the pectoral fin near the body). The inner margin of the second dorsal fin should be around twice the height of this same fin. The origin of the first dorsal fin should start behind the pectoral fins' free rear tip.

The bluewater bronzie tends to have a narrower facial profile too, with a distinct point on the nose. The harbour bronzie's nose outline is always distinctly oval in shape.

There are also colour differences but with shark colouration being somewhat variable between individuals it is not something you can positively pin down.

Suffice it to say that the bluewater bronzie has a greater tendency to have dusky tips on the anal fin and underside of the pectoral fin, and its overall colour is described as being a rich orange-brown with a coppery lustre. The harbour bronzie is most often described as being just 'brown'. But again, habitat can influence colouration so do go and measure fin length and fin placement before making any sweeping declarations about what species of bronzie you have caught.

Happy shark hunting! And do remember to use small-barbed hooks (I use Gamakatsus) and release that shark to live another day.

	This article is reproduced with permission of New Zealand Fishing News 1999 - by Craig Worthington Re-publishing elsewhere is prohibited