The picture that has raised controversy for years - Sharks do use shallow beach areas for reasons unknown…
During the early 1990’s, at a time when Dyer Island and Gansbaai used to be strange and unknown names, White Sharks were thought to exclusively use the little channel between Dyer Island and Geyser Rock, better know as Shark Alley. From 1996 onwards, these Sharks were found to actually be more numerous and active in the deeper waters surrounding the islands and the kelp beds where the Sharks could use their stealth and element of surprise to catch the Cape Fur Seals. Although Dyer Island rapidly gained international recognition as one of the hot spots for these Sharks, they only seemed to be present in large numbers from April onwards till October every year. White Sharks around Dyer Island are only temporary residents and only visit the area for a few days to a few weeks at a time. The small number of White Sharks observed around the islands during the austral summer months seemed to suggest that these Sharks used other areas and were virtually absent from the area. At the end of the year 1999, following the accounts from observations from the local fishing community, White Sharks were suddenly spotted in large numbers in an area Michael Scholl later named Shark Bay (Haaibaai). The amazing feature of this discovery is that this area is located only a few kilometres north of Dyer Island along the mainland coastline, in an open bay stretching from Uilenkraalsmond near Franskraal to Sandy Point near Pearly Beach, two small residential suburbs of Gansbaai separated by 15 kilometres of dunes and sandy beaches. From 2000 until 2007, the White Shark Trust investigated the two areas intensively and continuously, and identified two different habitats: offshore area around Dyer Island, and inshore area of Shark Bay. In 2003, Michael Scholl discovered that these sharks also frequently use the shallow near-shore and surf zone areas in Shark Bay.
The project has identified some key differences in white sharks observed around Dyer Island and in Shark Bay:
- Frequency of fresh bite wounds, potentially mating encounter scars, is higher in the inshore area of Shark Bay. Biting scars on the pectoral fins and in the gill area are often related to mating behaviour, but the high concentration of sharks in the area could also lead to frequent social interaction;
- A majority (97%) of sharks observed in Shark Bay are female, whereas around Dyer Island the sex ratio is 60% for the females. In some shark species, females are inhibited to feed for the weeks before and after giving birth. We hypothesis that maybe male sharks are inhibited to feed during the mating season in order to minimise injuries during the mating procedure involving the male shark biting the female in order to position the claspers for internal fertilisation;
- Although the average total length of observed sharks is similar between the two areas, large (>400 cm TL) and especially small (<250 cm TL) sharks are observed more frequently in Shark Bay. The large size of some of the sharks suggests that they could be sexually mature, which lends some evidence for the mating ground hypothesis.
Starting during the 2004/5 season, Michael Scholl initiated and conducted a boat-based transect survey of white shark distribution in the shallow waters (< 4 meter depth) along the Shark Bay beach. Over thirty white sharks were recorded on a single transect, some of the sharks were observed swimming in less than one meter depth, and previously undocumented social behaviour patterns were regularly observed: multiple sharks circling one another, follow and parallel swimming patterns, meeting and contact events, evasion behaviour, etc. It is possible that the shallow and highly aerated waters in the surf zone represent a resting area for white sharks. Most sharks observed in the shallows are larger sharks over the average length (320 cm TL), and their dorsal body coloration is considerably darker than that observed on sharks around the islands in deeper water. Although tanning has only been shown with hammerhead sharks, Michael Scholl suggests that white sharks may be directly affected by the sun, depending on their behaviour (swimming close to the surface or bottom) and their constantly changing habitat (shallow inshore, continental shelf or oceanic), and this may well affect their counter shading hunting strategy altogether. The sharks observed in the shallows do not seem to be attracted by chum, or interested in the natural preys occurring in the area, indicating that they are not using that area as feeding grounds (e.g. Stingrays, Teleost fishes, Dolphins, Seals). Initial observations also suggest that the sharks stay in the shallow waters for considerable amounts of time.
Michael Scholl advanced the hypothesis that White Sharks use these shallow areas potentially as mating grounds using the oxygen saturated water to quickly recover from their immobile love embrace. The lack of male Shark sightings could be explained from the hypothesis that male White Sharks could maybe be physiologically inhibited to feed during the mating period to prevent accidental fatal wounds to the female during the violent copulation event, hence they would not be attracted to food and not be seen by the researchers during chumming trials.
In order to better understand the behaviour of White Sharks in Shark Bay and especially in the shallow waters, Michael Scholl and the White Shark Trust initiated the use of Sea Kayaks to follow the Sharks without disturbing their natural behavior. The Sharks showed some initial interest and natural curiosity versus the Kayaks, and then moved on to their normal behavior without further care about the Kayaks. The now famous photograph taken by Michael’s best friend biologist Thomas Peschak, wildlife photographer and writer, has spread around the world in a flash and shows how humans can be in harmony with the ocean and its most feared predator. The importance to investigate and better understand the reasons for which White Sharks use shallow inshore areas such as Shark Bay along the South African coastline is two fold:
- if these areas indeed represent potential mating grounds (or of another ecological importance to the Sharks), these areas need to be immediately and completely protected from any human exploitation and use (fishing or tourism);
- to be able to assess, address et minimize the risk of the elevated Shark - Human encounters for beach users swimming and surfing.