Posted on Thursday, 19 November 2015
This year’s Sardine Run included plenty of Sardines. It is not always the case given the name of this spectacle, however our boats fish finder, the “sounder” showed huge schools of fish moving through at depths of between 40 to 60 meters; too deep for us to safely dive.
On sending the fishing jig down to those showings, we successfully hooked and brought to the surface a couple of sardines to confirm that they were in fact Sardinops sagax, or more commonly known as South African sardines. Sardines are cold water species and are usually associated with areas that exhibit cold upwelling’s (the movement of deeper, cooler, nutrient-rich water into shallow coastal areas).
Scientists believe the sardines start migrating when a cold ocean current moving east from the Agulhas Bank is established. It is also believed that this migration up the east coast is only 2% of the whole biomass, with the other 98% moving up the west coast and is thought, but not confirmed, to possibly be a sub species of the Sardinops sagax . This ocean current needs to be below 21°C, as sardines prefer water temperatures between 14 and 20°C. The current is rich in plankton, the sardine’s staple diet. Sardines follow this current, staying in shore to avoid the warm temperatures of the Agulhas current, flowing in the opposite direction.
The Sardine Run began with some great sea bird sightings! First on the list was a Northern Giant petrel, which we saw scavenging with the Cape gannets as they returned to the surface from a deep dive, with their quarry of sardines. The Petrel would wait on the surface in the vicinity of where the gannets entered the water; the petrel would then grab a gannet as they surfaced with its powerful beak and start drowning them until they regurgitated the sardines, making for an easy meal. Other special sightings included that of the Shy albatross and the Indian Yellow – Nosed Albatross.
Along with the Common and Bottlenose dolphins that we snorkelled with nearly every day, we saw Spinners and Pan Tropical spotted dolphins and a wonderful sighting of the shy and elusive Humpback dolphins. We also saw a “brand new” Bottlenose dolphin that still had creases along its flank from being in its mother’s womb!
It is labelled the “Greatest shoal on earth” by the BBC who spent over seven seasons documenting this migration.
The Humpback whales did not disappoint! While on their annual migration north to the warmer waters of Southern Tanzania and Northern Mozambique, they move in shore to avoid the Agulhas current. The Humpback whale coincidently undertakes the longest documented migration of any individual mammal. We enjoyed excellent double breaches and were lucky to snorkel with these majestic leviathans. This year I noticed that there were already a couple of new born humpbacks migrating with their mothers and surrogate mothers, and as nature would have it, we witnessed a predation on a newborn, with Dusky, Tigers and Copper sharks feeding on the unfortunate calf. We believe the calf had probably succumbed to the cold water, as the pregnant whales normally only give birth in the warmer waters near the equator before returning back to the much cooler waters of the Antarctic. They do not feed during this migration and will only feed once they have returned to the Antarctic almost five months since their departure.
In addition to this, we saw spectacular dolphin, gannet, Brydes whale, sailfish and a few big Cape fur seals also getting in on the action on other small bait fish in the area, like the Red eye sardines and the South African anchovy who move close to the surface and in significantly smaller numbers than that of the South African sardine. This behaviour makes it nearly impossible for the top predator responsible for creating the bait ball, the Common dolphin, to ball up and keep stationary long enough for us to enjoy on scuba. It is still an absolute privilege to witness!
The seine netters along the Kwazulu Natal east coast, a couple hundred miles north of where we were, had a bumper season with reports of many nets being landed and sardine even washing ashore on some Durban beaches!
It is labelled the “Greatest shoal on earth” by the BBC who spent over seven seasons documenting this migration. It is believed to rival that of the Wildebeest annual migration in the Serengeti! If only we all had as much time and money as the BBC, we could experience the “Greatest shoal on earth” every year! And that’s the beauty of nature; you just never know when you going to hit the “Jackpot” and we can’t wait to get back next year. As they say “you got to be in it to win it”.
Join us on our next Sardine Run adventure.
Alistair Louw - Skipper and Expedition Leader, Sardine Run.