In Search of the Elusive, Endangered Whale Shark

My four-hour flight from Doha, Qatar, lands at the tiny Djibouti City airport. On approach, the brilliantly clear East African skies afford a view of a largely barren, arid landscape shaped by plate tectonics and erosion. Closer to landing, the city of around 1 million, or just over 70% of the country’s population, comes into view.

I’m in Djibouti to join two researchers and eight shark enthusiasts led by Dr. Jennifer Schmidt of the Shark Research Institute. We’re on a seven-day expedition to find and identify as many whale sharks as possible, adding to the knowledge of this majestic but elusive fish species.

Following several days of rest from jetlag and exploration of the city, we begin our adventure on an 85-foot wooden Turkish gulet. After leaving the busy fishing port, the boat gently motors through the western Gulf of Tadjoura. The shipping ports and vessels diminish from sight as we enter the Bay of Tadjoura.

In the bay, the blue waters are void of any signs of humans, except for the occasional small fishing boat. The adjacent shores are rocky, sparsely vegetated and impressively mountainous. At 40 miles in length and 16 miles in width, the Bay of Tadjoura is a popular migration area for juvenile whale sharks who gather here to feed on the planktonic blooms between November and February.

En route to our first anchorage, a small pod of dolphins spotted us and playfully swam next to the boat’s bow for 20 minutes. And so began our marine adventure.

Our expedition aimed to identify as many whale sharks as possible and catalog their sightings into a worldwide database. This allows researchers to track their numbers and previous sightings and gain info on their migration routes.

Limited research exists on whale sharks, the world’s largest fish. Scientists believe they live for at least 100 years. At 3 feet long at birth, whale sharks are born live and fully developed, compared to most other fish that lay eggs that develop outside the womb. At sexual maturity at around 20-30 years old, they have reached around 26 feet for males and slightly larger for females. Adults may grow to over 65 feet and weigh over 75,000 pounds.

Whale sharks have a large mouth (up to 5 feet) on the front of their short snout, as opposed to below, as in most other shark species. This enables them to “filter feed” by continuously passing enormous volumes of water through their mouths, which are lined with gill pads that filter out any organism over 2-3 mm.

These fish swim slowly, averaging only 0.6 miles/hour. At this rate, snorkeling or free diving to observe these behemoths is relatively easy, as we quickly discovered. However, no assisted diving (such as scuba) can be used to observe these gentle giants, considered endangered by the IUCN Red List of Threatened Species, because it’s too disruptive to their natural behavior.

At our first location, expedition leader Dr. Schmidt explained the techniques used to photograph and video the fish. Each whale shark may be identified by the unique pattern of white spots on its right and left sides.

Ultimately, photographs or videos of these patterns are digitalized using software developed to identify celestial light formations. By comparing a creature’s patterns to the database of over 100,000 archived patterns of worldwide sightings, a whale shark may be identified as a previously spotted (and info on its habitat use and migration pattern inferred) or deemed a new sighting.

During our expedition, our morning routine began with recreational scuba dives. As a relatively new diver, I relished gaining experience and becoming more at ease with deeper and longer dives. Mid-morning consisted of searching for whale sharks from two eight-person skiffs.

Whale sharks tend to feed near the surface, so their massive bodies can be spotted easily in calm waters. In choppy waters, which we had almost exclusively, we scanned the waters close to our skiff for any glimpses of the large tail (caudal) fin, which tends to poke out above the surface. We boarded the skiffs again in the afternoons for more hours of searching.

We didn’t have much luck finding sharks from the skiffs, but on our third day, we found one close to our boat’s mooring. The skiff drivers approached the shark as we quickly donned our snorkeling equipment and jumped into the water. I plunged right in front of an approaching whale shark.

Though a little frightened by my first encounter, I photographed the approaching fish. It dove beneath me, continuing to feed passively without fear of me. I quickly swam after the shark, switching my camera to video mode to capture its patterns. We could determine the fish’s sex by diving beneath it. This one was a juvenile male about 15 feet long.

The shark eventually dove deeper, making it impossible to follow. Back on the skiff, we all beamed and shared our emotions about our first swim with a whale shark. I could barely contain my exhilaration.

Searching for sharks during the daylight hours on the skiffs became less fruitful throughout our week, though we continued in hope. Due to weather conditions, Dr. Schmidt hypothesized it wasn’t a great week for plankton, their primary food source. The water temperature soared to 84 degrees, far warmer than recorded in any previous season over 12 years.

We documented six whale sharks during our week. Interestingly, most interactions occurred just after dusk. By hanging a large light at the boat’s stern, planktonic species gathered in the illuminated surface waters. Almost every night, several whale sharks would come to feed on the aquatic smorgasbord the light facilitated.

From the boat’s stern deck and snorkeling the dimly lit waters there, we witnessed the sharks’ vertical feeding behavior. Positioning itself several meters below the surface, the sharks would orientate their massive bodies vertically and slowly travel to the illuminated surface while opening and closing their mouths, engulfing huge volumes of plankton. These nightly vertical feedings lasted hours, giving us an amazing after-dinner show!

In addition to searching for whale sharks, two researchers and I conducted plastic counts at four beaches within the Gulf of Tadjoura, part of a larger assessment conducted by researchers at Italy’s University of Insubria. Prevailing winds carry and deposit these macroplastics (bottles, flip-flops, toys, etc.) to most of the area’s wind-facing beaches and coastlines. We laid down a rope quadrant at each site and collected any plastics within that space for analysis of source and type.

Having recently evaluated microplastics from 10 beaches along the Delaware River Estuary and from filter-feeding mussels from the Delaware Inland Bays, I was struck with the enormity of plastic waste on these seemingly pristine beaches compared to my study sites on the U.S. East Coast. It’s a true testament to the far-reaching effects of our plastic consumption and ineffective or non-existent methods to limit its waste.

Despite the depressing visual of plastic littering the shores of these remote beaches, our field collections will hopefully add to the research evaluating the extent of plastic pollution and its sources in this remote part of East Africa.

This once-in-a-lifetime experience of documenting whale sharks made an indelible mark in my mind, and I also will cherish the memories formed with nine new friends on the expedition. As a professor with 30 years of research experience in coastal and marine pollution, I savored the opportunity to expand my research interests and broaden my expertise.

Lastly, I’m truly looking forward to bringing back my hands-on experiences to the classroom and sharing my knowledge and enthusiasm with my students through my annual fall course in oceanography.

Dr. Jeffrey Ashley is a chemistry professor at Jefferson. Watch his video from the trip here. 

(Photos/Courtesy Dr. Jeffrey Ashley, Dr. Jennifer Schmidt and David Robinson)