When Whale Food Moves: How Climate Change Put Humpbacks in the Ropes, and How California Fixed It

In 2014, a huge patch of unusually warm water settled off the west coast of North America. Scientists nicknamed it the blob. Over the next two years, it rearranged the coastal ocean so thoroughly that humpback whales ended up feeding in the same narrow strip of water where crabbers had set thousands of traps. Each trap was tied to a rope running up to the surface. Entanglements soared.

This is a climate story, and it’s also one of the rare ones where the people involved built a solution together.

Whales live and die by dense food

This week on the How to Protect the Ocean podcast, we’ve been looking at how giant whales feed. Lunge feeders like humpbacks and blue whales can’t graze on scattered food. They need dense swarms of krill or tight schools of small fish like anchovy to make each energetically expensive lunge worth it.

Off California, that food usually sits along a wide band of cold, nutrient-rich water fed by upwelling, where deep water rises to the surface. What we rarely talk about is that these food patches move. They shift with circulation and temperature, and when the band of good water shifts or shrinks, the whales have to follow. A whale that stays put in empty water starves.

The heatwave that squeezed the coast

Between 2014 and 2016, a marine heatwave spread across the Northeast Pacific. Warm surface water squeezed the food-rich zone off the West Coast into a thin strip right along the shore. Scientists call this habitat compression.

Jarrod Santora, a researcher with NOAA and UC Santa Cruz, led the study that connected the dots. His team found that predators normally spread out offshore moved inshore because that’s where the food was. Humpbacks switched from eating krill to eating anchovy, and the anchovy were close to shore.

Close to shore is exactly where the Dungeness crab fishery works. Each trap sits on the bottom, tied to a rope that runs up to a buoy. Thousands of traps means thousands of vertical ropes hanging through the water the whales had just moved into.

A second blow: toxic algae

The warm water also fed a massive bloom of toxic algae, which made crabs unsafe to eat. The crab season was delayed until late March 2016, so the busiest stretch of crab fishing landed in spring, right when humpbacks arrived to feed.

Before the heatwave, about 10 humpback whales a year were confirmed entangled off the West Coast. In 2015, there were 53. In 2016, there were 55.

Nobody in that story did anything new or reckless. The ocean moved, the whales followed their food, and the ropes were already there. Normal fishing became dangerous because the map underneath it changed. If you followed North Atlantic right whales moving into the Gulf of St. Lawrence, this pattern will sound familiar.

What do you do when the danger moves every year?

California set up a working group of crab fishermen, state managers, scientists, and conservation groups. Together they built the Risk Assessment and Mitigation Program, or RAMP. It tracks whale sightings, ocean conditions, and entanglement reports, and lets the state shorten the season, close zones, or limit fishing depth when risk climbs.

Those closures protect whales, and they also cost crabbers months of fishing. Spring closures became common, and the fleet felt it. So the question became: what if crabbers could keep fishing and take the rope out of the water?

Enter pop-up gear

Picture a crab trap on the seafloor with no rope going up. Its line and buoy are packed down on the bottom with it. When the fisher comes back, they send a signal from the boat, the trap releases its buoy, the line floats up, and the trap gets hauled in like any other. This is pop-up gear, also called ropeless or on-demand gear.

Between hauls, there’s nothing hanging in the water for a whale to swim into. That matters because entangled rope often wraps where a whale’s flipper meets its body. It digs in as the whale swims, drags gear that slows it down, and opens wounds that can become infected and fatal.

In spring 2025, during the season when traditional gear was shut down to protect whales, 12 California crabbers tested pop-up gear at full scale. They set 1,163 strings and hauled 25,721 traps. The gear came up on signal 98% of the time, and only 0.2% was lost. Those traps landed more than 217,000 pounds of crab worth about $1.4 million, during months the boats would normally have sat at the dock.

Just before Christmas 2025, the California Department of Fish and Wildlife made it official. Pop-up gear was approved for commercial Dungeness crab fishing during spring closures, from April 1 to July 15. Weeks later, when the state closed parts of the central coast to traditional traps because of whales, crabbers in those zones could keep fishing with pop-up gear. CDFW Director Meghan Hertel described it as a way to keep one of California’s most iconic fisheries going while protecting whales and sea turtles. Commercial crabber Brand Little called it “excellent news for California’s commercial crab fishery.”

Whales stay protected, crabbers keep working, and crab still reaches the table.

The ocean keeps moving

In 2024, entanglements jumped again: 31 humpbacks confirmed off the West Coast, nearly double the year before, with a cluster near Monterey in the fall linked once again to whales crowding inshore after dense prey.

Pop-up gear is new, and switching is a significant investment for many fishers. It also only covers part of the season so far, so plenty of rope is still in the water. That’s why people on the water remain part of the early warning system.

What you can do

If you see a whale tangled in rope or gear, report it right away to your local stranding or entanglement hotline. Stay with it at a safe distance if you can, and give responders as much information as possible. Never try to cut it free yourself. Entangled whales dive, and people have died trying to help. Trained teams can free the whale; they just need to know where it is.

Look up your local hotline now and save it in your phone before you head out on the water. In the United States, NOAA’s hotline is 1-877-SOS-WHALE (1-877-767-9425).

Picture a spring morning off central California: humpbacks lunging through schools of anchovy, a crab boat working nearby, and no buoys or ropes on the surface. Just a signal sent, a buoy popping up, and a trap coming home full. The food will keep moving. With clear water, the whales can follow it safely.

Takeaways

• Whale food patches move with ocean temperature and circulation, and whales must follow them.
• The 2014 to 2016 marine heatwave compressed food-rich upwelling water into a narrow coastal strip.
• Humpbacks shifted from krill to nearshore anchovy, overlapping with Dungeness crab gear.
• A toxic algae bloom delayed the 2016 crab season into the humpbacks’ spring arrival.
• Humpback entanglements rose from about 10 a year to 53 in 2015 and 55 in 2016.
• California’s RAMP lets managers close or limit fishing when entanglement risk climbs.
• Pop-up gear keeps rope on the seafloor until the fisher sends a release signal.
• The 2025 trial: 25,721 traps hauled, 98% reliability, 0.2% gear loss, about $1.4 million in crab.
• California approved pop-up gear for spring closures in December 2025.
• If you see an entangled whale, report it and keep your distance. Never try to free it yourself.