Geography of Seal Island, False Bay

 

Seal Island, False Bay is a small, elongate rocky islet with its long axis oriented roughly north-south, measuring approximately 400 by 50 metres, and with a maximum elevation of about 7 metres above the high tide line. The island has a narrow western shelf, with the water depth dropping off to a depth of 20 metres within 5 metres of shore, and a broad eastern shelf, where the water does not drop off to comparable depths until about 20 metres from shore. Off the southern tip of the island is a small, craggy outcrop, the portion which protrudes above the surface at high tide is approximately 4 metres long and 2 meters tall.

Water temperature off Seal Island varies little throughout the year, hovering between 13 and 14°C at the surface and a degree or so cooler at the bottom where the depth is 20 m. [From March through September, the predominant winds at Seal Island are north westerly, changing to south easterly from October through February.]

Marine Biota off Seal Island

Seal Island is populated by approximately

  • 60,000 Cape Fur Seals,
  • roughly 200 Kelp Gulls,
  • small groups of Cape Cormorants and White-Breasted Cormorants,
  • as well as a few Sub antarctic Skuas and Jackass Penguins.

The shallow waters immediately surrounding the Island support large shoals of Southern Mullet, Red Roman and Hottentot. Occasionally, Jackass Penguins find their way to Seal Island from the breeding colony at Boulders Beach, located about 2 kilometres south of Simon’s Town.

The offshore waters surrounding Seal Island are inhabited by a variety of cetaceans, including

  • Bryde’s Whales,
  • Southern Right Whales,
  • Common Dolphins and
  • Dusky Dolphins.

Large smacks of jellyfishes are quite common throughout the waters of False Bay. Large flocks of Cape Gannets often follow pods of Common and Dusky Dolphins, plunge diving and feeding on shoals of small teleosts swimming a metre or two beneath the surface.

During February and March of each year, Bronze Whaler Sharks are relatively abundant in False Bay, where they are caught in nets to be sold locally as a food fish.