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Creature Feature: MSI finds rare albino bat ray in San Francisco Bay

Anticipation and excitement gave way to utter shock and surprise last week when the instruction staff of the Marine Science Institute discovered a rare albino bat ray in their trawl net while training on the San Francisco Bay. Executive Director Marilou Seiff believes this is the first time in MSI's 50-year history that they've caught an albino bat ray. Albinism in bat rays has been reported, but it is rare. The albino bat ray, which was netted by MSI, is shown in the photo to the left.

During summer camp, school programs, and public voyages, MSI routinely catches

bat rays of all sizes, along with a variety of fish and leopard sharks. As part of these education programs, a trawl net is set behind our 90-foot research vessel, the Robert G. Brownlee. The marine animals that are caught are identified by the children and participants, and then released back into the Bay. Fish data volunteers also record such vital information as size and sex for research purposes.

When the albino bat ray (along with the day’s catch), was placed in our holding tank, it was obvious we’d caught something unique. The young ray showed tell-tale signs of albinism with its red-colored eyes and translucent, pink skin. As the above picture shows, internal structures, such as blood vessels and cartilage, were visible through the ray’s outer layers.

Bat rays normally have a black or dark grayish coloring on top with a creamy white underside. The picture to the left shows a bat ray of normal coloring. This bat ray was caught and released during an earlier voyage.

Albinism is caused when an animal is born with an absence of any pigmentation. For mammals (including humans) a lack of pigmentation results in white hair. In birds its white feathers and in reptiles its white scales. Albino animals also have characteristic pink or red eyes. This is caused by the lack of pigment in the iris, making the blood vessels of the retina visible.

Being an albino animal living in nature can be problematic resulting in a shortened life-span. Animals with albinism:

  • Lack protective camouflage making them easy prey

  • May be excluded from families or groups; or rejected by mates

  • May have reduced heat absorption in colder waters (for marine animals)

  • Have increased sensitivity to sunlight, possibility resulting in cancer

  • May have impaired eyesight

Despite these challenges, albino animals in the wild have been known to reach adulthood and breeding status. At MSI, we hope the San Francisco Bay albino bat ray, which was released, reaches adulthood and thrives.

We also hope you’ll take a moment – when traversing a bridge over the Bay or standing at its shores – and remember the albino bat ray and all the marine life that call the San Francisco Bay home.

California Bat Ray. The Elasmodiver Shark and Ray Field Guide. Web. 6-15-2017.

5-22-2017. Albinism in biology. Web. 6-15-2017.

Denise Mohsenin serves as the link between Marine Science Institute and the education community. She enjoys helping schools and teachers bring marine science and environmental literacy to their students. Her current favorite fish for teaching is the starry flounder. Ask her why at

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