Whale Sharks

Tracking an Elusive Animal

Summary
These gentle giants can grow to be the size of a school bus! So why don't we know more about where they go?

Introduction
The whale shark (Rhincodon typus) is the largest known extant fish species. While they are typically observed at lengths between 18-32 feet, mature adults can reach more than 60 feet (18.3 m) in length. The sole member of the genus Rhincodon and the only living member of the Rhincodontidae, whale sharks are slow-moving, filter-feeding elasmobranchs that eat plankton and prefer tropical and warm-temperate seas. Rarely found in water temperatures below 70°F (21°C), adults are often found feeding at the surface, but may dive as deep as 3200 feet (1000m).

Growth, longevity, and reproduction of the whale shark are poorly understood. Studies looking at growth bands in their vertebrae have estimated whale shark lifespans at 80-130 years. Whale sharks are ovoviviporous and pregnant females can carry as many as 300 fertilized eggs at a time, but it is unknown where they give birth. Because they grow slow and mature later than other species, thier populations are particulalry vulnerable to losses from bycatch, vessel strikes, and poaching. Because of this, the species was listed as endangered in 2016.

In January of 2021, NOAA shark scientist, Dr. Eric Hoffmayer, and his team released a publication outlining the seasonal occurrence of whale sharks in the northern Gulf of Mexico. The team of researchers looked at more than 800 sharks that were sighted or tagged to try an understand thier travel patterns throughout the course of the year.

Data Activity

NOAA researchers compiled sighting and tracking information over 16 seasons and then created figures to illustrate patterns in the data. Study each of the following images and then answer the questions below.

Sightings by Season

Distribution by Season

Migration Tracks

Discussion

• What do the data show about whale shark populations in the northern Gulf of Mexico?
• How does the number of whale sharks in the Gulf compare from season to season? Is this what you expected to see? Why or why not?
• Compare the three data figures, which do you think is the best one for determining how whale sharks migrate in the Gulf of Mexico? 
• Whale sharks face threats from changing climate, entanglement in fishing gear, vessel strikes, illegal fin harvest, and decline in plankton populations. If you were a legislator, how would you work with scientists to develop a plan to help protect the whale sharks from one or more of these threats?

Additional Information

Whale Sharks: The Gentle Giants of the Sea (50 minutes)

Tracking Whale Sharks in Indonesia (Interactive Website)