Great news! We’ve had numerous reports of solid dolphin (both common & bottlenose) and gannet feeding activity off Red Sands, Wild Coast. This is a mere 20 km south of Port Edward. Fishermen confirmed the presence of sardine in the stomachs of gamefish landed in this region. We can expect the advance shoals to reach Port Edward by the weekend, and if these shoals get squashed shorewards by warm water, then we can expect to be thrilled.

Sea surface temperature on 26th June 2010. image courtesy of MRSU

The arrival of these fish follows a period of cooling of shelf waters to within sardine’s preferred temperature range (compare the above SST image with that from the 21st June). In the image from the 26thJune, there is a clearly visible strip of 20 °C water reaching up to KZN. While these do not represent the epic conditions of 2004 (see below, but note the different temperature scales used), they should be sufficient to allow sardines to reach KZN.  Once again, the importance of temperature in regulating the movement of these fish is manifest as circumstantial evidence.

Sea surface temperature on 23rd June 2004. image courtesy of rsmarinsesa.org.za

We’ll be heading back down to Port St Johns on Sunday, where we will hopefully be able to conclude our shark tagging data collection.

photo: Will Robbins

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June 29th 2010

June 29, 2010

Finally, back in warm Durbs!! Back in boardshorts and t-shirts, even now at 18h00. And don’t even think about putting a heater on… Saying that, a cold front does arrive tomorrow.

It’s been an action packed few days, and not just on the football pitch either. Since the 22nd, we (myself and the Canadian Crazy 4), have attended 4 matches, spent 4 days in the Pilanesberg Game Reserve (watching a pride of lions feeding upon and fighting over an elephant carcass), and had crazy times in the fan parks of Jo’burg.

Four ladies of liberty and their buffoon-zela-man

Fun times before Japan vs Denmark in Rustenberg

and Japan qualify for the next round...

lioness feeding on elephant carcass

During this time, the sardine run activity has been slowly creeping northwards along the Wild Coast. The last report I had, 3 days ago, was of activity off Coffee Bay. If the northward progression is sustained, we should have some activity off Port St Johns any day now! We’ll keep you posted…

June 21st 2010

June 29, 2010

Common dolphins, Delphinus capensis. photo: Will Robbins

A very promising start for today’s research, with patches of foraging birds off Poenskop (the north end of PSJ Bay). There were nice concentrations of diving gannets, with at least 800 birds feeding between Port St Johns and Mntafufu River. Unfortunately, although there were quite a few common dolphins feeding, they did not isolate a patch of fish into a stationary baitball. We need a stationary ball with predators, and particularly sharks, feeding upon it before we can deploy our transmitters. Consequently, we spent the greater part of the morning doing exploratory dives to check whether the activity below the water line matched the chaos above. Regrettably, it didn’t.

diving Cape gannet, Morus capensis. photo: Will Robbins

One particularly noteworthy item: there were lots of bottlenose dolphins amongst this feeding activity. At one stage of the morning’s activity, we followed a pod of bottlenose dolphins with birds diving regularly above them, but at no stage did the bottlenose dolphins show any indication that they would form a bait ball. There were quite a few oil slicks and some smell of sardine on the water, so we were very hopeful. Unfortunately, the activity died down and by 11h00 one would never have suspected that anything had happened during the morning, if one did not notice the rafts of birds sitting and digesting what little food they were able to gather during the craziness.

Sea Surface Temperature 21st June 2010. image courtesy of MRSU

The activity from earlier this month seems to have all but disappeared. This is disappointing, but very interesting nonetheless. From the satellite images taken during this period, one can see that shelf temperatures have increased with all activity restricted to the southern end of the Wild Coast, where one can see nice cool temperatures. It seems very likely that the passing Natal Pulse from earlier this month allowed a limited amount of sardine through, which resulted in some netting on the KZN South Coast, but the warming of temperatures seems to have retarted the impetus of the main shoals, which appear to the languishing on the southern Wild Coast.

Because of the lack of activity, and because we need stationary baitballs for us to deploy our tags, we have decided to take a hiatus from the sardine run, and do some serious FIFA World Cup fan mongering!!! We intend to return to the Wild Coast on the 4th July, unless the activity gets going earlier…

June 20th 2010

June 29, 2010

Happy father’s day, and although there was not one father to be found on our boat, we had a very happy day indeed. Unfortunately, it was not happy scientists’ day, as it was very, very quiet on the sardine run front. The happiness came instead from the perfect Wild Coast weather, the clear water, the jumping humpack whales, charging common dolphin pods and flashy bonitos feasting upon our red-eye roundherring offerings.

Port St Johns sunrise. photo: Vic Peddemors

We launched today through a mighty Mzimvubu sunrise to quiet seas and even quieter skies. The million dollar question was which direction to travel: south to Brazen Head or north to Mbotyi. Neither direction looked particularly promising, although, travelling northwards we did find plenty of gannets, schools of dolphins and pockets of fish (mostly red-eye roundherring and mackerel). We also passed oil slicks on the water with the distinctive smell of sardine. But no feeding pockets of predators. Very strange indeed. All the ingredients for some serious predatory feeding are there, but nothing is happening. Instead we filled our day with tracking a pod of about 300 dolphins 30 kilometers up the coast (and collecting some valuable data on their movements) and diving with some dusky sharks.

dusky shark, Carcharhinus obscurus. photo: Will Robbins

You can see, from the trackline posted below, that common dolphins swim up the coast in a zig-zag when foraging. What the trackline does not show, is how suddenly the whole pod changes direction to forage in the new direction, and how the shape of the pod changes. It was a very interesting exercise, indeed.

tracking common dolphin foraging

June 18th 2010

June 18, 2010

apologies for not being up to date. Still battling with the internet connection here (PSJ hippie-villie left behind the technology curtain).

will try to do our stuff today, on the blog tomorrow.

Not much action for us today – cool water was found at Mbotyi with all the activity that we managed to find.

more tomorrow

June 17th 2010

June 18, 2010

battling with the slow internet here. please check out my pdf…

June 17th 2010

June 16th 2010

June 16, 2010

June 16th 2010

Due to the terribly slow internet here in PSJ, I’ m attaching today’s blog as a pdf. HOpefully it is quicker like this. grrrrrrr.

During early June we had the first reports of sardine run activity off Port St Johns. Rod Haestier, our skipper for the 2010 sardine run, was dillegently stocking up the larder for our trip and was kind enough to phone me and let me know of the activity. The baitfish were mostly east coast roundherring (“red-eye”) and mackerel, but there was some sardine mixed in with them. There was plenty of predator activity with the usual birds diving and dolphins gorging themseves. What was particularly encouraging was the presence of many sharks at the surface. The activitywas so promising that the KZN Sharks Board lifted their shark nets and drumlines along the lower KZN South Coast. Over the past week, the activity seemed to be slipping south, to the Brazen Head area, just south of Port St Johns, but yesterday there were fresh reports of sardine off Waterfall Bluff. So, 2010 sardine run has started. Historically speaking, this year’s run is almost a month early. We head down on Friday, and we’re champing at the bit!!!

Why has the run started early this year? Let us look at satellite images (obtained from the Marine Remote Sensing Unit (MRSU) at http://www.afro-sea.org.za/) from the 6th June (Fig. 1):

Fig. 1. Sea surface temperature conditions along the South African east coast on the 6th June 2010
In Fig. 1, the star indicates Waterfall Bluff. You can see that a thin strip of cool water ( < 21 C) reaches up to Waterfall Bluff, indicating temperatures suitable for sardines to occur.  What is particularly interesting about this image, is the large meander in the Agulhas Current to the south of Waterfall Bluff (indicated by the black box). This meander appears to be a phenomenon called a “Natal Pulse”. Usually the Agulhas Current flows more or less parallel with the coastline between Durban and East London. This can be seen in the orange strip of warm water in Fig. 1. On a handful of occasions during the year, a large meander, called a Natal Pulse, forms off Durban and travels southwards at about 20 km per day. Interestingly, these meanders circumscribe cool, upwelled water (also visible in Fig. 1). Over the past 2 weeks, or so, I’ve been following the southward progress of the meander, visible in Fig. 1. The presence of the meander has coincided with the early arrival of the sardine run, and may well be partly responsible for the cool conditions and activity we’re seeing now. But wait, that’s not all… scroll down now and you will see a free image of chlorophyll a concentration (Fig. 2), also from the MRSU:

Fig. 2. South African east coast chlorophyll a concentration, 6th June 2010

When one compares Figures 1 and 2, one can see that the meander is associated with both cooler conditions and elevated chlorophyll a (chl a) conditions. Chl a is the green pigment found in all photosynthesising plants, and in single celled algae in oceans (see Figure 2). “Flowing” northwards from the base of the meander are elevated chl a concentrations, suggesting good feeding conditions for zooplankton, upon which sardine largely feed, besides feeding on algae themselves. Clearly visible in both images are strong thermal and chl a fronts, conditions which sardine are known to prefer. It is intriguing that the early occurrence of the 2010 sardine run may be explained using satellite imagery, and the case for using these tools to predict sardine presence continues to be built following our efforts from last year. More to follow…