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Survey crew with the NOAA Twin Otter aircraft at Hyannis Airfield – (from left) NOAA Corps pilots Kristy Twining and Nicole Cabana, and a typical crew of observers: Misty Niemeyer, Cynthia Christman, and Misty Nelson. A 2004 graduate of Humboldt State University in Northern California, Christman did aerial, shoreside and small boat surveys for whales and seals on the West Coast. Christman came to the Northeast in 2005, part of a Humboldt invasion that has brought at least five observers to work on East Coast marine mammal surveys. NOAA/NEFSC photo.

This image of harbor and gray seals is an “oblique” picture shot out the side window of the survey craft, a NOAA Twin Otter, during a January, 2006 flight over Gull Island, a small island off Penikese Island. NOAA/NEFSC photo by Cynthia Christman, MMPA Research Permit 775-1600-09.

Vertical image of gray seals hauled out on a sandbar near Muskeget Island in December, 2005, from the belly of the Twin Otter. NOAA/NEFSC photo by Peter Duley, MMPA Research Permit 775-1600-09.

Observer Peter Duley taking an oblique photograph out the Twin Otter’s side window during a February seal flight. NOAA/NEFSC photo by Cynthia Christman, MMPA Research Permit 775-1600-09.

by George Liles

The NEFSC’s airborne marine mammal observers spend most of their time peering out the windows of a NOAA Twin Otter aircraft, scanning the waters for whales. When they spot their prey, the aerial observers’ work is just beginning. While the NOAA pilots drop their Twin Otter aircraft below 1,000 feet and fly tight circles, banking at steep angles, the observers busy themselves shooting photographs out the windows. The photographs are later analyzed in the lab, where biologists are able to identify individual whales.

This winter, the observers have added a new wrinkle to their picture-taking. The NEFSC aerial team, led by Tim Cole, has been shooting out the belly of the NOAA aircraft, taking “vertical” pictures of the haul-out sites favored by New England’s burgeoning gray seal population.

“The vertical pictures ensure we’ll get coverage of an entire island,” explains Cynthia Christman, a biologist who came to the NEFSC in January 2005 to work on right whale surveys.

Right whale work remains the bread-and-butter for the aerial observers, but since December the team has been flying for seals on days when off-shore weather makes whale flight impossible. One seal survey route takes the biologists on a tour of the Cape and South Shore, where they take the traditional “oblique” photographs out the aircraft’s side windows. Gordon Waring, the NEFSC seal expert, uses those photographs to monitor the size and distribution of local seal populations.

“We’re looking for trends,” Waring explains. “Is the number of seals in an area going up or down? We’re also monitoring habitat use – are they expanding their haul-out sites?”

A second seal survey takes the crew to Muskeget Island, off Nantucket, and two islands off Maine, where they take pictures of gray seal mothers and pups for Stephanie Wood, a University of Massachusetts/Boston graduate student who is studying seal populations on the islands during pupping season.

Wood’s work requires an accurate count of all the seals on the island, including animals hauled up in the sand dunes. The aerial team decided to use vertical pictures because the top down images can be lined up more easily to provide a count of seals on the entire island. The vertical images may also reveal seals hauled out in rocky ledges where they would be hidden from oblique photographs.

“We got the idea from Wayne Perryman, a biologist at the Southwest Fisheries Science Center who started doing right whale vertical photogrammetry in the summer of 2000,” Cole says.

Cole’s group began developing a vertical system in 2003. “We developed our system for whales,” Cole says. “It’s the best way to get accurate length and width measurements.”

The NEFSC survey crew used the vertical technique in nine seal surveys conducted between mid-December and early February. To survey Muskeget Island, they flew 12-17 passes over the island while a face-down observer shot as many as 400 pictures out a portal in the belly of the plane. While survey flights are generally not for the faint of heart or weak of stomach, the vertical picture taking is a special invitation to nausea: the view out the belly of the aircraft offers not a glimpse of the horizon – just a continual dizzying panorama of water, rocks and beaches.

The vertical images will allow Wood to count the number of gray seal pups on the islands at five points in the pupping season. With a complete record of seal births over the course of one season, she will be able to make a model of pup production that will allow biologists to estimate the number of seals born for those years (past and future) where they have only partial data about births.

While lab-based biologists pour over the thousands of seal pictures, the NEFSC’s airborne biologists are still in the air, flying whenever the weather is good. The gray seal surveys are finished for the winter, but the monthly Cape survey will continue through May, and the photographic hunt for right whales will last through June.

Posted March 20, 2006