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The Peaks and Troughs of California Seamounts

Featured Image: An orange basket star covers a yellow Picasso sponge at Davidson Seamount, approximately 75 miles off the California coast. Courtesy of NOAA.

Seamounts Are Oases of Life

Seamounts are found all across the world’s oceans, acting as small oases of life dotting the otherwise sparse deep seafloor. These massive underwater volcanoes provide ecologically crucial habitats that support incredibly vibrant and beautiful hotspots of marine life. In part, this stems from the large effects that seamounts exert on local currents, resulting in the increased upwelling of nutrient-rich water, and the greater influx and retention of food in the area.  A wide variety of marine life maintains strong associations with seamounts, including open ocean (pelagic) species such as tuna, sharks, billfish, seabirds, sea turtles, and marine mammals, as well as benthic organisms such as deep-water corals and other sponges. Scientific expeditions to seamounts frequently discover new species. In one study, 29-34% of the observed species were new to science. California seamounts are no different; they are home to many newly-discovered species including corals, a giant jellyfish, and worms.

Ecosystems in Crisis

Unfortunately, the fragile seamount ecosystems off the coast of California are endangered by a number of anthropogenic (human caused) impacts including climate change, pollution, oil and natural gas extraction, deep-sea mining, and overfishing. Like all marine systems, seamount habitats are subjected to increasingly warm, less oxygenated, more acidic, and food-limited conditions as the result of our rising emissions of greenhouse gases. These conditions will make it difficult or perhaps impossible for habitat-forming species such as corals to survive in the future. Pollutants, ranging from excess nutrients, plastics, and chemical waste, threaten to upset the delicate balance of seamount food webs. Oil and natural gas drilling can have disastrous effects on deep-sea ecosystems, while deep-sea mining could result in the wholesale destruction of entire habitats. Though neither industry is very active in California waters, there are known oil and precious mineral deposits that are likely targets for future exploitation. Commercial fishing represents a widespread threat to deep-sea ecosystems around the world. Bottom-trawling for groundfish, which involves dragging a massive net across the seafloor, is particularly damaging to fragile cold-water coral and sponge ecosystems. Once disturbed, these long-lived and slow-growing communities may not recover within our lifetime. Two of the most-fished California seamounts, Tanner and Cortes Banks, have been heavily exploited for their historically abundant tuna, swordfish, rockfish, seabass, sea urchins, squid, mackerel, spiny lobsters, and abalone. Recreational fishers alone catch a staggering 5,000-10,000 fish per year at the banks, while the abalone fishery was forced to close in 1997 due to the near-complete collapse of the population.

A large school of rockfish circle an outcrop of brown stony corals and hot pink hydrocorals at Cortes Bank, a seamount just 80 miles off the coast of Los Angeles. Courtesy of NOAA.

Conserving the California Seamounts

Despite their ecological importance and threatened status, most seamounts have little or no protection from human impacts. In California waters, there are an estimated 63 seamounts that span the entire length of the coastline. Of these, only Davidson Seamount has been granted permanent, strong protection from fishing, drilling, and mining due to its inclusion in the Monterey Bay National Marine Sanctuary in 2008.

The rest of the California seamounts have more limited protections from fishing as regulated by the Pacific Fishery Management Council. The council derives its authority from the Magnuson-Stevens Fishery Conservation and Management Act, the primary law governing fisheries management in US federal waters. While the council’s ultimate goal is to promote the optimal exploitation of fisheries, they are also under mandates to identify and protect essential and vulnerable habitats. In January 2020, the council finalized new regulations that improved the protection status of the California seamounts and other marine habitats. Known as Amendment 28, the regulation reopened a previously closed area to bottom trawling, while also creating two large trawling closures.

One of the primary actions of Amendment 28 was to reopen an historic fishing ground that had been closed for almost two decades. In 2002, large declines in groundfish populations wrought by overfishing resulted in the enactment of a large closure that prohibited bottom trawling activities in an area covering more than 2,000 square miles along the California coastline. Due to rebounding groundfish populations there, the new regulation reopened this area to trawling activities. Amendment 28 also added a series of smaller closures totaling 13,000 square miles to bottom trawling fisheries, including many habitats containing sensitive coral and sponge habitats. The goal of these closures were to protect a variety of features including canyons, seamounts, and methane seeps. In addition to these closures, the new regulations closed all waters deeper than 3,500 m (11,500 feet) to fisheries with gear that contacts the bottom, adding protection for a large offshore area with many seamounts.

Bottom trawl fishery closures altered by Amendment 28 to the Pacific Coast Groundfish Fishery Management Plan, effective January 1, 2020. The former trawl closure (grey), established in 2002, was reopened for bottom trawling, adding approximately 2,000 square miles of fishing grounds. New Essential Fish Habitat (EFH) conservation areas were established (orange), closing an area of approximately 13,000 square miles including large closures in the Southern California Bight (see inset map). The Amendment also closed a 130,000 square mile offshore area referred to as the Deep-Sea Ecosystem Conservation Area (DECA, green) to fisheries that use bottom-contacting gear.

The Need for Permanent Protection

The new regulations enacted by the Pacific fishery council do provide a level of protection for the California seamounts and other deep-water habitats, but also highlight the need for stronger and more permanent protection from human impacts. However, these regulations can be undone by future council actions, opening up sensitive ecosystems to damage from destructive fishing practices again. Deep-sea coral and sponge communities are extremely long-lived and slow-growing. Once they have been trawled, they will not fully recover in the span of a few decades. Therefore, conservation measures must not only be effective, they must be long-lasting to fully safeguard these important ecosystems. We need to act now to secure strong and permanent protections for seamount habitats before they are irrevocably damaged.

We need your help to ensure that California’s underwater treasures are conserved for generations to come. Please take Marine Conservation Institute’s Seamountaineer Pledge  to show your support for seamount conservation!

Note: Right now scientists on board the research vessel Nautilus are mapping and investigating areas off the coast of California that include some of the seamounts discussed above. They will live stream videos from the ship while exploring: deep-sea coral habitats, hydrothermal vents, an extensive octopus aggregation, a search for meteorite fragments. Click here to see a schedule of livestreams and the video. View Marine Conservation Institute videos of marine life on the seamounts here.