The Okinawa Aquarium currently holds 3 whale sharks. . Photo John Turner

The first record of a captive whale shark was in 1934 in a net enclosure of a natural bay at the Mito Aquarium, Japan. The shark was kept for 122 days. Other captives have been in more traditional aquarium-tank settings. Aside from the issues above, these captives have provided some interesting information on the growth rates of whale sharks.

One of the most significant captives was a neo-natal pup taken from the litter of a pregnant female caught in the Taiwanese fishery. This male pup was 60 cm long when it first arrived at the Marine Palace Ecological Aquarium, Oita, Japan, and was kept successfully for 3 years and 2 months until it died achieving a total length of 3.7 m - a growth rate of 116cm per year from birth size.

	The whale sharks share the Kurosio tank at the Okinawa Aquarium with a vast array  of pelagic marine life. Photo John Turner

The aquarium most notable for whale shark husbandry is the Okinawa Churaumi Aquarium, Japan. From 1980 to 1998, 16 whale sharks (14 males; 2 females) had been kept here and to this day 3 whale sharks are on exhibit. The sharks were all captured around Okinawa Island by set-nets during the months of March to September and ranged in size from 3.1 to 6.3 m weighing between 290 to 1750 kg.
The sharks were kept in the 27 X 12 X 3.5m Kurosio tank with the water temperature kept between 19.8 to 29.60C, matching environmental conditions during capture. Survival times ranged from as little as 3 days to the current record of nearly 10 years, dependant on their initial condition on arrival, as some animals had been injured during capture. 

The longest surviving whale shark is still at Okinawa aquarium. It was 4.6 meters long on arrival in March 1995. Now after 9 years 9 months of captivity the shark is over 7 metres in length, a growth rate of 24cm per year.

The whale sharks in the Kurosio tank are fed a mixture of krill, squid and fish sprats. The amount is calculated in relation to their body mass varying from 11% of their weight per week in the first year of captivity to 8% in the third and subsequent years.

Whale sharks in captivity do allow studies of growth rates to be made. Photo John Turner

Overall growth rates ranged from 21.6cm per year (4.5m male) to 29.5cm per year (6.35m female). While it has to be accepted that growth rates in captivity do not necessarily equate to those in the wild, these findings are of interest. It appears that whale sharks have dramatic growth rates in the first few years of life (in excess of 100cm per year) until they reach around 3m in length when growth slows by about 75%. Perhaps exponential early growth helps these defenseless slow-moving pups grow too large for all but the biggest of predators.

An international effort is necessary to ensure a safe haven for the whale sharks in the world’s oceans. If action is not taken soon, we may only ever watch these majestic animals through a glass barrier.