Observation of the Week, 9/8/16

This Brown smooth-hound shark, seen along San Francisco Bay by @sassafire, is our Observation of the Week!

Naturalist Morgan Dill grew up along the shores of Lake Michigan, and says she  “couldn’t be pried off the beach in the summers. I spent most of my days outside exploring, playing in the nearby creek and building forts in the backyard, scattering seeds I’d find and then watching them sprout and grow.” Now she’s a naturalist who works at the Crab Cove Visitor Center along the shores of San Francisco Bay, where she leads field trips, does seine netting, and educates folks about the bay’s flora and fauna.

Last week some visitors came to the visitor center saying they had found a small shark washed up on the tide line, so Morgan and her colleague went to check it out. They identified it as a Brown smooth-hound shark, “which we don’t typically see, though they are not uncommon,” she says, they confirmed it was a female and wasn’t injured. They then walked it out into the water and watched it swim away.

While Northern California is known for its population of Great White Sharks, that species usually hangs out along the coast, especially around the Farallon Islands, and only rarely enter the bay itself. There are, however, many other species of smaller sharks that call the bay home, such as Leopard Sharks, Northern Pacific Spiny Dogfish, large Broadnose sevengill sharks, and of course the small Brown smooth-hound shark, which is actually preyed-upon by the sevengills. Brown smooth-hounds average around two feet in length, and swim close to the bottom where they find invertebrates and small fish for food. Their name comes from their iridescent brown dorsal color. It’s tough to know why this one was so close to shore, but these sharks tend to pup in the shallow waters of the bay in spring and summer. The bay is an important nursery for many fish, including sharks. Not a commercially important fish, so far its population numbers have been holding steady, unlike many other shark species.

Morgan admits to not being “the most prolific of iNaturalist users when it comes to posting observations,” but she uses iNat in other ways, such as checking IDs of things she’s found, and she’s using it with high school students for a program she teaches that’s run by the East Bay Regional Park District and the Save the Redwoods League. “[The students] are always surprised that people are out there willing to look at what they find and identify it,” she says. “I love knowing they are getting real feedback from other citizen scientists, and have a feeling of contributing with their own experiences out in the field.”

And for Morgan herself, “I think that being a naturalist, and using iNat, makes me pay attention to the smaller details, and giving time to really consider what would help identify or distinguish an organism. Taking time pushes me to think about the beautiful intricacies of things, and ultimately discover more.”

- by Tony Iwane

- Here’s a short video showing a pregnant Brown Smooth-hound shark.

- Last year a Great White Shark was seen making a kill off of Alcatraz, the first known recorded incident of a Great White kill inside the bay.

- While most of us picture a Great White or something similar when we hear the word “shark,” sharks and rays (their cousins) are incredibly diverse. Here are some photos and descriptions of some of them, courtesy of the BBC. 

Publicado por tiwane tiwane, 08 de setembro de 2016, 08:54 PM


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