The Great White Shark Mystery as reported in FINSA recently.
First question is, ‘are they a mystery?’ To me, a mystery is an event or experience, for which there is no logical explanation. A light in the night sky that suddenly appears and, as suddenly, disappears! We know very little about Great Whites. That does not make them mysterious. That merely indicates our lack of knowledge about them!
That, in turn, lines them up with several other major problems that are far more serious. These include, amongst others, Covid 19, Global Warming, and an over populated Planet, for none of which, it seems, do we have enough Knowledge, or the slightest clue of how to deal with anyone of them. However, I do believe that shortly, in this already highly technological world, increasing knowledge will produce the answers to deal with the first.
But, you may rightly point out, this a Fishing Industry magazine, so let’s get back to Great Whites, the probable ultimate Apex Predator in the biodiversity of the South African inshore fishing environment. With that term comes my first long standing problem. If it is an apex predator, what predates on it, and why, over the past three years, has their sudden disappearance from areas like False Bay and Diaz Island almost become the norm. False Bay has always been a known congregation area for great whites since I first started fishing there as a child. We always believed it was the seals on Seal Island that were high on their Menu of choice, but today know that seals are not necessarily their chosen diet. Like most predators, including humankind, convenience plays a large part in deciding what we eat..
Some twenty years ago, Diaz Island became one of the finest venues for Shark Cage Diving In the world. Then three years ago it suddenly changed when all the sharks, 90% or more Great whites, took off to who knew where. Slowly they returned, but then did the same disappearing trick six months later This time, in a. panic, the operators hit on the idea of attracting another species, the Bronze Whalers (Bronzies), who were often seen to have a go at the large chunks of fish used to attract the Great Whites to the cages containing the underwater spectators, before giving away to them with wise alacrity. With no competition any longer, the operators then used to initially attract over fifty at a time. Then came the commercial shark longline boats and skiboats to once again spoil the fun, and more importantly destroy a niche industry that attracted, as over 90% of their clients, extremely well-off overseas tourists.
The overriding question still remained! Why were the great whites leaving and to where?
About 18 months ago, a strange story started doing the rounds, and, reaching my ears, my first gut reaction was to respond, “Don’t tell me killer whales (Orcas), because, after more than sixty years at sea, I can assure you that Great Whites probably do not appear on their menus, except for the very extreme exception.” Although capable of prodigious migration for whatever unknown reason, they are an inshore species with a probable chosen diet of fresh (live) fish. Ask any line fisherman or even more so divers and spear-fishermen. Seals may come next, where they are readily available, though many of the places where they are encountered, seals are not. Meanwhile Orcas are normally deep sea inhabitants, and there is absolutely no proof that they have decided to change that habitat, neither from the scientists, nor the game fishermen. The latter have always occasionally encountered them, as I have, prodigious distances off Cape Point on the tunny grounds in the company of porpoises, seals and mainly yellowfin tuna, who all frequently hunt bait fish together. The Orcas, it appears love both fresh tuna and porpoise (dolphin) meat!
This unlikely story stated they left False Bay simply because of been harassed and eaten, at least in part, by “PORT” and “STARBOARD”, believe it or not being a pair of killer-whales; ie. Orcas. Well, I do not know why, but it certainly was not for a lack of food, or anything else scientifically specific. I fished False Bay, both semi-commercially and recreationally from 1954 until the 1980s, and in all that time only encountered Orcas just inside the mouth only twice!
However Orcas, found in all the oceans of the world, have a reputation of being one of the most intelligent of all sea mammals. That is why they are targeted by Marine and Sea Parks for training and display. They are family oriented, so normally found in small or medium size pods of as little as two, up to fifty individuals. They appear to decide on a chosen diet, frequently hunting as far as possible for whatever species of sea life that represents. There are many strange stories of their chosen feeding habits, such as tipping up or down ice floes so as to dislodge back into the water whatever is on top of them. Another is their oft encountered action of jumping onto sandbanks to either grab a seal or chase it back into the water. ( As far as I know not yet encountered in South Africa.) So whilst being accepted as normally occupying near off-shore coastal waters, a couples willingness to enter inshore shallow bays or waters is not so surprising.
During my line fishing days, Great Whites regularly fluctuated in numbers. Some years hardly any bothered us by stealing our fish off our lines, whilst at other times they almost seemed to shoal, and you had to up anchor and move well away, as no hooked fish reached the boat! Nor would it have been pollution, which is still only a minor problem sometimes inshore. Neither would it be one of my pet theories, I believe badly under rated by the scientists, human disturbance. Having said that, I must jump to the other side of the fence by saying that when it comes to underwater sound surveying, I believe the problem accentuated by scientific evaluation and the “Greenies,” is seriously overdone.
I repeat I do not know of any logical reason and if the study in False Bay from 2000 to date resulted in no firm indication, let alone finding, I think we must all accept that research on them is still in its infancy. Please also discount trophy targeting and inshore protective nets. Both these have been on a continuous decline for the past thirty years, the latter intentionally, and, in the case of the former, it has always been a totally insignificant activity to have had any meaningful effect on their population level. I am not right up to date on landing levels of great whites by shark longliners (only two or three have been active since licences were granted some years back) or any other longliner, and, surprise, surprise, there do not seem to be any reliable stats at the Department of Fisheries. Part of the reason is that Fisheries report less than one hooked great white per set. I also doubt that there is an annual aggregation of Great Whites off the South-east coastline at this time of the year. There are no more fish or seals there than anywhere else from Cape Town to Port Elizabeth. It is more likely that that our extraordinary mild winter weather, and the relaxation of “Lockdown” regulations have resulted in far more people and surfers in the water. Great Whites have always been inquisitive. Ask the divers again.
Port Elizabeth to Durban is a different story. The Sardine run, when the inshore water cools down, is a spawning migration of one of the most important parts of the Maritime inshore food chain, and everyone joins in, including the sharks. Their tendency to move north eastwards is accordingly unsurprising anyhow, let alone the now almost inarguable fact of Port and Starboards’ chosen diet as they clearly patrol the coast seeking their prey. It has also been surmised that in the absence of Great Whites a substitution of species has occurred with the Bronze Whaler (Carcharhinus brachyurus), and Cow (Seven Gill—Notorynchus cepedianus) sharks taking their place, as the next two Apex Predators behind the Great White. Predation substitution is a common marine environment occurrence. However, I find it personally difficult to grant the Seven Gill the status of an Apex Predator, though a Predator it is.
Why, you ask, are they named “Port” and “Starboard”? The reason is that male Orcas have uncommonly high single dorsal fins which can stand up as much as two and a half meters in a fully grown adult. This pair always swim side by side with each fin always flopping outwards every time. There has been some conjecture that they may be a male and a female. This is unlikely as the female’s dorsal fin is not as tall and curves backwards without flopping to the side.
So the Apex Predator Great White is now out-apexed by what is probably the ultimate Apex Predator of the oceans, not a fish but a mammal, though normally, but not always we now know, present in different oceanic environments. A pack of them is known to even attack whales!