Whale Shark (Rhincodon typus) Issues Paper

Department of the Environment and Heritage, May 2005
ISBN 0 6425 5082 4

Distribution & migration

The Whale Shark occurs in approximately 124 countries worldwide (Fowler, 2000 in Chen & Phipps, 2002). They have a broad distribution usually between latitudes 30°N and 35°S in tropical and warm temperate seas, both oceanic and coastal (Compagno, 1984). Although Compagno (1984) suggests that this species prefers waters with temperatures between 21-250C, the Whale Sharks sighted at Ningaloo Marine Park in Western Australia are predominantly found in waters with temperatures averaging 270C (Norman, 1999).

Global Whale Shark distribution

Global Whale Shark distribution

Source: Fisheries Global Information System (2004)

Information on distribution of Whale Sharks in Australia is based primarily on seasonal surveys at Ningaloo Marine Park, with very limited records collected elsewhere. Whale Sharks are known to occur in New South Wales, Queensland, Northern Territory, Western Australia, Christmas Island, Indian ocean and occasionally South Australia and Victoria (Compagno, 1984; Last and Stevens, 1994, in Pogonoski, Pollard and Paxton, 2002; Norman, 1999).

In 1999, a Whale Shark was tagged with a satellite tag at Ningaloo Marine Park in Western Australia and tracked for 420km away from the Australian shores towards Indonesia before the signal was lost (Norman, 1999). A further two Whale Sharks were tracked from Ningaloo Marine Park in 2002: the first travelled more than 2000 km to Christmas Island before the signal was lost; a second shark travelled approximately 1800km over a 35 day period towards Indonesia (Norman, 2004). However, longer term information on the movement and distribution of Whale Sharks in Australia is limited. Satellite telemetry studies off the Malaysian and Philippine coastline indicate that Whale Sharks swim an average of 24 km/day and have a minimum range of 2000 km (Eckert et al., 2002). Eckert and Stewart (2001) also found an average 24 km/day swim rate for Whale Sharks in the Sea of Cortez, Mexico, and the north Pacific Ocean.

Eckert and Stewart (2001) report the movement of one tagged whale shark of 13 000 km over 37 months as it migrated from the Sea of Cortez to the western north Pacific Ocean. The IUCN Shark Specialist Group affirms that the whale shark migrates extremely large distances (Cavanagh et al. 2003). Whale shark movements within a region may be precisely timed to coincide with localised productivity events and/or behavioural changes in their prey that allow for more efficient exploitation (Taylor, 1994; Norman, 1999; Wilson, Taylor & Pearce, 2001).

There appears to be spatial and seasonal segregation of Whale Shark populations according to size and sex (Norman, 1999 in CITES Prop. 12.35). It is possible that juvenile Whale Sharks exploit different ranges to that of more mature sharks, and that different age classes of males and females undertake alternative migration paths.

Whale Sharks have a tendency to be site-faithful (philopatric), returning regularly to the same seasonal feeding locations (CITES Prop. 12.35). For example, it has been possible to identify particular individuals (using photographic identification) returning to Ningaloo Marine Park and the Maldives in successive seasons (Norman, 2004). This tendency to form what are effectively discrete stocks makes the species particularly vulnerable to localised depletion by directed fishing activity (CITES Prop. 12.35). Range States for the Whale Shark are listed in Appendix 1.

Critical habitat

In Australian waters, Whale Sharks seasonally aggregate in coastal waters off Ningaloo Reef between March and July each year, at Christmas Island between December and January, and in the Coral Sea between November and December. (Taylor, 1994; Norman, 1999; Wilson, Taylor & Pearce, 2001; Norman, 2004; John Stevens, pers. comm.). Evidence suggests that seasonal aggregations off Ningaloo Reef are due to migratory behaviour associated with climatic and oceanographic processes, with a possible link between the abundance of aggregating Whale Sharks and the physical and biological oceanography of the region (Wilson, Taylor & Pearce, 2001). The importance of the plankton bloom and high productivity of the waters surrounding Christmas Island at the time of the mass spawning of the red land crab (Gecarcoidia natalis) in attracting Whale Sharks to this Australian External Territory cannot be underestimated.

The species is generally encountered in areas where the water surface temperature is between 21° and 25°C with upwellings of colder (17°C or less) water, and a salinity range of 34 to 34.5 ppt (Iwasaki, 1970 in Colman, 1997). These conditions may produce localised concentrations of the planktonic and nektonic prey on which the Whale Sharks feed (Colman, 1997).

Whale Sharks aggregate in certain areas rich in nutrients to feed on seasonal aggregations of tropical krill and baitfishes (Ningaloo Reef), red land crab (G. natalis) megalopa (Christmas Island), fish spawn (Belize), and shrimps (northern Borneo and Philippines) (CITES Prop. 12.35). It could therefore be suggested that these areas form a portion of the Whale Shark's critical habitat.