Mapping the Monterey Canyon

Credit: David Fierstein (c) 2000 MBARI

This aerial view of Monterey Bay from the south was created by combining computer-generated topographic and bathymetric data. Vertical relief has been exaggerated to better show the Monterey Canyon and mountains on either side of the bay.

May 2, 2018

For more than a century, fishermen have been drawn to the Monterey Bay region for its abundance and diversity of marine life – a richness that is in large part due to deep, submarine valleys that fork through the bay. One of those valleys, the Monterey Canyon, bisects the bay and drops to over two miles deep - twice the depth as Arizona’s Grand Canyon! It’s the largest and deepest canyon off the Pacific Coast, with tributaries including Soquel Canyon to the north, and Carmel Canyon to the south. Monterey Canyon starts just offshore of Moss Landing.  It reaches out towards the sea at over 400 kilometers in length - a topography of cliffs and spires, sediment slides and rocky faces. Krill from the deep canyons migrate up to the surface every night, helping to support the Monterey ecosystem.

In order to understand the dynamics of the canyon, Monterey Bay Aquarium Research Institute (MBARI), which is located in Moss Landing, has been mapping the ocean floor with an autonomous underwater vehicle (AUV) that is equipped with four mapping sonars - swath multibeam sonar, two sidescan sonars - and a sub-bottom profiler that operate simultaneously. According to George Matsumoto, Senior Education and Research Specialist, this is to understand the sediment flow as well as to find objects of interest or objects to avoid with their remotely operated vehicles. He likened the turbidity currents to mudslides on land - sediments get saturated and then slide. As the water gets denser, it moves downstream and a massive current carrying debris flows through the canyon. As George explained, “It’s different than a mudslide, as we are still trying to understand what might trigger it. It’s not heavy rains like on land, and it’s not just sediment moving. Sometimes the entire seafloor can shift.”

When asked how this impacts local seafood, he explained that deep dwelling canyon fish like black cod and grenadier can swim above the silt. However spot prawns can get buried. And there’s the potential for flatfish getting buried as well. But George pointed out, “Those aren’t really fished in the canyon.”  

However, commercial fisherman, Lorenzo Sanchez, who fishes out of Moss Landing for salmon, crab, and open access lingcod and halibut, credits the canyon for luring in his catch. “Salmon come by to eat the krill. And Dungeness crab seem to hang out along the rims of it.” 

On April 18th, MBFT executive director, Sherry Flumerfelt, delivered a presentation on our efforts to revitalize a sustainable, local seafood economy, as part of the MBARI seminar series. “By reaching out to organizations like MBARI, we hope to build opportunities for collaboration and understanding between the fishing community and our conservation and research partners.”

Sherry Flumerfelt