The golden spots on the female kelp greenling above are more true to the markings on this Salish Sea fish than the off-color yellow specks you’ll see in most photographs. That’s because the image above isn’t a photo. It’s actually a hand-drawn illustration by biologist and illustrator Joseph Tomelleri.

Tomelleri draws fish for scientific research. His models are specimens that he receives from researchers or that he collects himself. Over the past 30 years, he’s drawn more than 1,200 scientifically accurate illustrations of about 900 species, carefully rendering the edges of their scales, the exact number of fin rays, and even the faint lateral line, or sensory organ, that runs down the sides of all fish. His lifelike artwork has been featured in thousands of publications, he estimates, helping ichthyologists better understand fishes and their changing ecosystems.

Historically, ichthyologists turned to artists to illustrate fish anatomy and morphology in their studies. But even in the age of digital photography, there are good reasons why Tomelleri’s scientific collaborators prefer his artist’s hand to photographic documentation. As Tomelleri explains, it can be difficult to find representative photos of a single fish species where identifying features such as color patterns and fin arrangement are consistent. “You may have some pictures taken underwater, with a fishermen holding them, or with the fish laying at the bottom of a boat,” Tomelleri says. “All the details that a scientist wants to show on a specimen would be all over the place.”

Fish trawled for research purposes can also become deformed or mutilated. But an illustrator can take a damaged fish and reconstruct it in a drawing, says James Orr, an ichthyologist at the Alaska Fisheries Science Center, part of the National Oceanic and Atmospheric Administration, who recently collaborated with Tomelleri.

It’s important that scientists have “a clear picture of what a fish looks like and its morphology,” says Orr.

Fishing trips that Tomelleri took with his father as a child spurred his curiosity in the creatures that lurked in deep holes and crevices underwater. In 1985, following his graduate studies in range management and botany at Fort Hays State University in Kansas, Tomelleri and his former classmates created a booklet of the fish living in a creek by the university. When photos failed to represent the fish accurately, Tomelleri stepped in to draw them.

“When you see a photograph, you can tell if [the fish has] been dead for two minutes,” says Tomelleri. “They just lose that little bit of spark.”

For one of his latest projects, Tomelleri worked with Orr and University of Washington ichthyologist Ted Pietsch to create scores of color pencil illustrations of fish species in the Salish Sea, which spans from Washington State to British Columbia. Orr and Pietsch have been collecting and documenting fishes in these inland marine waters since the mid-1980s and released an updated report this past September on species presence and diversity in the area. The paper, which features 23 of Tomelleri’s illustrations, is just a prelude to an upcoming 1,000-page comprehensive book that will contain locations, distribution, and habitats of all the known fishes in the Salish Sea, which now number 258.

The Salish Sea is a young system, according to Orr. Glaciers covered the area until 10,000 years ago, giving way to features like Puget Sound and the Strait of Georgia. Its vast range of habitats has given rise to diverse fish fauna, including the rare warm-blooded opah and the more common sockeye salmon—two species that aren’t often found in the same region.

It’s been 35 years since the last in-depth survey of Salish Sea fishes was completed (and that survey focused only on Puget Sound), and Orr has big expectations for his team’s follow-up. “It’ll be the first time I think [these fishes have] really been accurately depicted,” he says. “It’s like the fish is just jumping right off the page.”

As Orr and his colleagues collected the Salish Sea specimens, they sent them to Tomelleri, whose Leawood, Kansas studio looks more like the collection room of a natural history museum. Hundreds of fish specimens mingle with the Prismacolor pencils that give Tomelleri’s illustrations their “smooth, wet look,” as he puts it. One illustration—which can range from 6–7 inches to more than 20 inches long—generally requires an average of 25 hours to complete, though it can take much longer. To create the opah above, he racked up 70 hours at his drawing desk.

With every fish he draws, Tomelleri shades in a corner of the bigger picture of fish diversity in North America. “I’ve done other landscapes and wildlife, but that doesn’t interest me as much,” he says. What he really loves is venturing out into rivers and creeks with a big net or seine in hand and capturing the fish that duck in dark places.

“If you don’t have them fresh or see them live, you don’t see those colors. They are really beautiful and subtle sometimes,” he says. “That’s what I love to try to mimic.”