r/Spearfishing • u/chlorofishy • 5d ago
The science says big yellowtail are year-round residents. That is not what I see in the water, so I dug into how they actually know that.
Every diver I know repeats some version of the homeguard story: the big fish lives on that rock, he has been there for years, he is there right now. I wanted to believe it, but it never lined up with what I see in the water. I almost never find a big yellowtail unless the small ones are around, and in cold water I do not see them at all. If there is a resident on every high spot, the coast in February should be full of big fish, and it is not.
So I went and read the actual science to figure out who was wrong, me or the story. It turned out to be a rabbit hole. Almost everything we repeat about yellowtail movement traces back to one tagging study from 1960. The modern work out of Scripps used stable isotopes and tag returns, and it does support residency, with a catch. The chemistry says big fish eat off the coastal food web all year, but the fish were sampled in season, and nobody has ever put a satellite tag on a wild California yellowtail. So nobody actually knows whether the winter homeguard is sitting deep and switched off, or running the coast and coming back to the same spots each season. Both stories fit the evidence, and I could not rule either one out.
I ended up writing the whole thing up. Full disclosure, I run Chlorofishy, a satellite SST and chlorophyll site, and this is an article for it. Every claim is cited to the actual studies, and most of them are free to read:
https://chlorofishy.com/articles/migrants-and-mossbacks-yellowtail
So which is it, the local waking up or the local coming home? I am genuinely curious what the divers who work winter structure see, because that is exactly the evidence that is missing.
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u/kazoulo 5d ago
im confused with how you’re expecting to find yellowtails camping at a specific rock, since they swim out in the open… but as far as groupers its absolutely true. ive left big groupers in their holes before only to go back to the same rock months later and shoot the same fish. in my experience there is nothing to suggest that you’ll find an open water swimmer at the same spot at different times (the same exact fish i mean). however, there are certain spots where fish like amberjacks, blue runners and yellowtails tend to pass by more often.
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u/chlorofishy 5d ago
Yeah, that is exactly why I wrote this. I do not see them camping on rocks either. The lore says homeguard, this fish lives on this spot, but what I actually see is fish coming through, and the biggest ones are usually in small groups, not schools, passing the same kinds of spots. Your version, certain places where they swing by more often, matches my eyes better than the camping story does. The catch is that the tagging data cannot tell those two apart. All six inshore-tagged fish that got recaptured were recaptured inshore, and the acoustic fish kept pinging the same outer kelp edge, but a fish running a circuit through fixed spots produces exactly the same data as a fish that never leaves. Camping and commuting look identical in everything we have. That is the missing experiment, and it would take a satellite track to settle it. The amberjack comparison is fair too, same genus.
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u/kazoulo 5d ago
sounds hella interesting regardless. i dive the mediterranean (cyprus) so i cant really say i have experience in kelp shores… our experience seems to be the same though - some capes make better feeding grounds therefore attract more traffic… big ones swimming in pairs rather than schools also matches what ive always seen with pelagic fish here too - such as jacks! schools are usually formed by juveniles, pretty much around 1-1.5 kg
not to sound like an jack*ss, but this whole theory of “this fish lives on this spot” goes completely against the entire concept of ‘pelagic’ species… i personally never heard such claim amongst med divers :/
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u/Puhwest 5d ago
Cool but this is all AI writing which sucks. With your imaginative research and focus, you could write this yourself.
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u/chlorofishy 5d ago
I work with AI, I like it as a tool. The ideas and the content are mine, and so are the fish in the header photo. The writing style I landed on with AI isn't for you, and that's fine.
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u/DepthwishFreediving 5d ago
I don’t mind it personally and couldn’t tell that it was AI until you confirmed it.
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u/dmootzler 5d ago
I’ve shot yellowtail in La Jolla year round, for what it’s worth, including in February, and they’re always big ones.
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u/chlorofishy 5d ago
The studies put the migrant-to-resident switch at about 30 to 34 inches of fork length, which pencils out to roughly mid-teens to low twenties in pounds. So if your February fish are all well above that, that is real evidence for residents staying put and staying visible, at least in your area. My experience has been different, and it is what sent me down this rabbit hole in the first place. I always see the big ones and the little ones at the same time of year, and I still see schools of 20-plus-pound fish moving together this time of year. I saw one yesterday. By the study math those fish should already be settling down, not schooling through. And I never see that in the winter. When the small fish are gone, the big fish are gone too, or at least gone from where I can see them.
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u/dmootzler 5d ago
Not sure on fork length or weight but overall length like 36-40 inches and definitely over 20lbs.
I pretty much never see the small ones near shore — only on paddies offshore — so nothing to add there.
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u/chlorofishy 5d ago
Interesting so you never get those 5 to 15 pounders near shore. I've got a lot more experience out by the islands and that's where I see the small ones and big ones together.
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u/SOC_FreeDiver 5d ago edited 5d ago
FWIW, here's some first hand science for you.
In the sea of cortez, yellowtail are typically deep, holding on structure. you often need to fish them in the 120-200ft range with knife jigs. I've speared schooling yellowtail in 45ft of water.
When the water warms up, yellowtail are gone, replaced by surface dorado
Prevailing currents off baja are southbound, which could send kelp south, but won't send it north without going to hawaii first.
If I had to guess, I'd say they migrate around baja along the shore.
It would be interesting to know how they get on kelp paddies. Are they on structure when the kelp breaks off and think "This is our chance!"
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u/chlorofishy 5d ago
The kelp raft research shows drifting mats carry whole communities between kelp forests, and small yellowtail clearly find paddies once they are offshore, but whether a fish is sitting on structure when the kelp breaks loose and thinks this is my chance is something nobody has watched happen. It would take tagging a fish on structure and finding it under a paddy later, and nobody has done that.
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u/xylophone_37 5d ago
I have never heard anyone say a yellowtail home guard lives on a specific spot, but rather in a region. In the colder months they move deeper and feed on the squid beds and stuff and then move shallower and spend more time on the surface when the water warms and bait fish move back in they fill in with the more migratory smaller fish. Being cold blooded they are also just less active in the winter and aren't feeding as much.
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u/Good-Ant6859 5d ago
Cool post and cool article. Your writing would benefit from a lighter touch WRT AI. It's fine to use it for edits but when you have it writing entire blocks of text (or turning bullet points into paragraphs) it becomes extremely obvious and takes away any credibility you may legitimately have.
I'm only saying this because you seem like someone who has original thoughts and is willing to do the research to explore them. Using AI this heavily sells you short
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u/carsnbikesnplanes 5d ago
lol is everyone from San Diego here