Join me in the cold, dark, life-sustaining NE Pacific Ocean to discover the great beauty, mystery and fragility hidden there.

Grunt Sculpin – Little Fish, BIG Attitude!

Meet the fish that so often has people exclaiming “It lives HERE?!”

Yep, the tiny Grunt Sculpin is a powerful ambassador for raising awareness about the depth of biodiversity hidden in the cold, dark, rich waters of the north east Pacific. 

We are programmed to associate warm waters with exotic-looking fish species but read below for the Grunt Sculpin’s astounding adaptations and masterful mimicry. 

The species reaches only a maximum of 9 cm.

It is adapted to look like a Giant Acorn Barnacle (Balanus nubilis)!  When facing outward, its pointy nose looks like a closed Giant Acorn Barnacle and when the fish turns around, its tail looks like the foot of the barnacle that rakes in plankton.

Adapted to look like a Giant Acorn Barnacle!
Closed Giant Acorn Barnacles. See how similar this is to the nose of a Grunt Sculpin?
Foot of a Giant Acorn Barnacle. The tail of a Grunt Sculpin looks so much like this!

This little fish has giant attitude. When not hidden away in a barnacle (or a cup, see photo), it can be highly territorial, hopping around on its pectoral fins in a strutting, jerky fashion. A lot of literature reports that the Grunt Sculpin is an “awkward swimmer” but I solidly disagree. I once saw one flash away with lightning speed back to its hiding place. Yes, I was being an annoying photographer.

If you can’t find an empty barnacle shell. A cup will apparently do!

Ah and you probably think the males are the master strutters? Ha! The female is as fierce as can be. Reportedly, she will chase a male into a crack, an empty barnacle shell, or another place of no escape and guard him there until she is ready to lay her eggs. When she has laid them, the male is released to do his duty.

She watches him to ensure he fertilizes the eggs (up to 150 at a time) and then, according to some sources – she saunters off leaving the male to care for the eggs but may return once in a while to take on a shift. (Source: Aquarium of the Pacific.

Very young Grunt Sculpin. The Red-Gilled Nudibranch in the upper part of the image is only about 2 cm 

From Casey Cook, aquarist with the Aquarium of the Pacific (pers com 2022-12-19): “The female often pushes the male into guarding so she can roam. She will get very vocal, and demanding – making sure he does the job!”

The Grunt Sculpin’s pointy “bill-like” head is reflected in the species’ scientific name.

With regards to classification, the scientific name Rhamphocottus richardsonii reflects the Greek word for beak “rhamphos” which is appropriate for the Grunt Sculpin’s bill-like snout. This makes some people think that the species looks like a seahorse but note that they are not closely related at all. The Grunt Sculpin is the only member of its genus. It is truly one of a kind.

Juvenile Grunt Sculpin #1 of 3 photos.
Juvenile Grunt Sculpin #2 of 3 photos. 
Juvenile Grunt Sculpin #3 of 3 photos. 

Oh, and are you wondering about the name “Grunt” Sculpin? Apparently the species grunts when it is taken out of the ocean. You would too! Likely it also grunts when being defensive underwater. It is also the sound I make in my delight when I find one. It will be a very loud grunt indeed if I ever find one guarding eggs or with its tail-end extended out of a barnacle.

Below, more of my photos of Grunt Sculpins. 🙂

Grunt Sculpin next to a Gold Dirona (nudibranch species). See him /her?
Grunt Sculpin and a Clown Dorid (another nudibranch species).
A Grunt Sculpin “strutting” over the ocean bottom. See the cloud of silt lifted off as a result?
Another Grunt Sculpin in an empty barnacle shell.
And another.
You can’t see me.
Grunt Sculpin hiding in a broken mussel shell.
Juvenile Grunt Sculpin
I wonder if this one is female and about ready to lay her eggs?

And some more photos of individuals to show how similar their markings are.

– Aquarium of the Pacific – Grunt Sculpin
– Fishbase – Grunt Sculpin
– Love, M. S. (2011). Certainly more than you want to know about the fishes of the Pacific Coast: A postmodern experience. Santa Barbara, Calif: Really Big Press.

12 Responses to “Grunt Sculpin – Little Fish, BIG Attitude!”

  1. Ken Lund

    We use to get these at times in our prawn traps while fishing in Knights Inlet

    • Khelly

      Hi, I was just going to E you to share that we recently had about 50 grunts hatch at AOP wthen I saw your reference. Thank you. Our nursery is very productive lately. The grunts are tiny! and very well camoufaged. I also have two grandchildren in the form of zebra
      sharks. Their Daddy was in my wading exhibit for several years. Thank you for a grunt expereince.

    • Keith Urchuk

      These little rascals are also found when diving in discovery passage. They are fun tp watch and they are so beautiful.

  2. renoun

    I love grunt sculpins but the Pacific Spiney Lumpsucker is defiantly my favorite oddball fish of the PNW.

  3. CG

    I’m very curious about the fact that the grunt sculpins spit the babies out into the water column. I know the source is AoP, but i work there and i’m raising our baby grunts and i’ve never seen this happen. I’ve also had many grunts hatch without a male guarding the eggs, so i’m not sure about this…I’ll have to set up a camera at night time and find out. They are a wonderful fish though, thanks for the great article about them!

    • The Marine Detective

      Thank you SO MUCH for this feedback and your expertise. I will adapt the language in the blog to reflect this uncertainty. Please let me know if you find out more!

      • CG

        You’re welcome! I certainly will. I’m very curious about it too! I can just picture the adult shooting little larvae out of their mouths like cannon balls – so cute! 🙂

  4. Smartical Parical

    very helpful for my project! What do they eat exactly?

  5. Ed Gullekson

    I have a recent (last week) photo of a grunt protecting eggs. You can see hatched eggs and intact eggs in the photo. The grunt is in a giant barnacle shell. I am glad to share the image.

    Ed Gullekson


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