What a Super El Nino Means for California Divers: New Fish, Warmer Water, and a Few New Hazards
- Bret Whitman
- 1 hour ago
- 5 min read
You have probably seen the map going around, the one with the big orange arrows pushing warm water up the California coast and a bunch of sharks and sea snakes riding along with it. It looks dramatic, and honestly the basic idea is real. A strong El Nino warms up the eastern Pacific, and that warm water pulls a lot of southern species north with it. Some of that is great news for us as divers. Some of it is stuff you want to know about before you get in the water. Here is how I am thinking about it.
What Is Actually Happening
El Nino is a pattern where the surface water in the eastern Pacific runs warmer than normal for months at a time. When that warm water pushes up against Southern California, it does two things. It drags warm-water species north, well past where they normally live, and it shuffles the whole food chain around as the bait moves and the predators follow. We have seen this before. The 2015 and 2016 El Nino years brought fish to San Diego that most of us only see in Baja, and it also brought a few surprises nobody was expecting.
The Good News: New Fish Show Up
For a diver, a strong warm-water year can be one of the best things that happens all decade. When the warm water moves in, so do the fish that live in it. In a good El Nino off Southern California you can see:
Mahi-mahi (dorado). These usually live way down south, but in a warm year they push right up into SoCal waters and hang around kelp paddies and floating debris offshore.
Tuna and yellowtail closer in. Warm water and the bait that comes with it can bring bluefin, yellowfin, and yellowtail within reach of a day boat, sometimes within reach of the beach.
The occasional wahoo or billfish. In the warmest years, fish that belong in the tropics start turning up off our coast.
On top of the new species, the water offshore often turns warmer and bluer, which makes for better visibility and more comfortable diving. If you have been wanting to try bluewater hunting, a strong El Nino year is when the opportunity comes to you.
More Sharks, Including Baby Great Whites
The same warm water brings more sharks, and that is worth talking about honestly. Most of what shows up is nothing to lose sleep over, but you should know it is there. You may see more hammerheads and other warm-water sharks that follow the bait north. You will also see more juvenile great white sharks close to shore. Southern California already has nursery areas where young white sharks spend their first few years in the shallows, and warm water tends to make those aggregations bigger and push them into more spots.
Juvenile white sharks are mostly eating rays and fish, not looking for divers, and encounters almost always end with the shark leaving. Still, use your head. Keep your fish on a float line well away from your body, do not dive in dirty water where you cannot see what is around you, and if a shark is showing too much interest, get out. That is good advice every year, and it matters more in a warm one.
The Weird One: Venomous Sea Snakes
This is the part of the map that grabs everyone, and it is real, just not as common as it looks. The yellow-bellied sea snake is the only sea snake in the eastern Pacific, and it normally lives in warm tropical water far to the south. In strong El Nino years a few of them get carried north and wash up on Southern California beaches. It happened during the last big warm-water stretch, with snakes turning up in San Diego, Orange County, and as far north as Ventura.
Here is what you need to know. The yellow-bellied sea snake is venomous. It is not aggressive and it very rarely bites, but the venom is no joke, so you do not touch it. If you find one on the beach or in the water, leave it alone, keep kids and dogs away from it, and let a lifeguard know. Do not try to move it or throw it back. The ones that wash up are usually sick or dying in water too cold for them anyway. Seeing one is rare, but in a strong El Nino it is possible, so it is worth knowing what you are looking at.
Warm Water Also Means Domoic Acid
One more thing that comes with warm water and does not make the flashy graphics: harmful algae blooms and the domoic acid that comes with them. Warm, nutrient-rich water can feed big blooms of a certain algae that produces domoic acid, and that toxin builds up in shellfish and in small fish like anchovies and sardines, and in the guts of the fish that eat them. It does not cook out, and it can make you seriously sick.
If you take shellfish, or you are eating the whole small fish, this matters. Check the current California Department of Public Health advisories before you harvest or eat anything, especially mussels, clams, and scallops, and pay attention to warnings about anchovy and sardine viscera. It is a quick thing to check and it is not worth guessing on.
How I Am Playing It
None of this should keep you out of the water. A strong El Nino is honestly one of the more exciting things that can happen to California diving. Here is how I adjust:
Look offshore for the new species. Warm blue water, kelp paddies, and floating structure are where the mahi and the pelagics stack up.
Stay sharp about sharks nearshore. Keep speared fish away from your body, dive in clean water, and do not push it if something is acting interested.
Do not handle anything that looks like a snake. Take a picture, tell a lifeguard, and move on.
Check the toxin advisories. Look up the CDPH shellfish and domoic acid advisories before you eat what you take.
If you want to keep an eye on water temperature, visibility, and conditions at your spot so you can time your dives around all of this, check the SpearFactor Fish & Dive Conditions Tool at conditions.spearfactor.com.
Get in safe and enjoy the warm-water fish while they are here. As always, check the current CDFW regulations before you take anything, follow the CDPH advisories before you eat it, and remember that conditions and the fish that come with them can change fast in an El Nino year.
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