Lay a male and a female kelp greenling side by side and you’d have a hard time believing they’re one species. The females are freckled; the males carry blue patches ringed with reddish spots. Hexagrammos decagrammus also starts life drifting in open water before it settles into nearshore rock and kelp, and the males guard egg masses attached to rock, which ends up mattering more than the color once you’re deciding what to keep.
At a glance · The short version
Scientific name
Hexagrammos decagrammus
Family
Hexagrammidae: true greenling, the same family as lingcod.
Sexual dimorphism
Females freckled with small reddish/golden spots; males carry irregular blue patches surrounded by reddish spots.
Maximum age
WDFW: at least 18 years in northern Southeast Alaska and up to 25 years reported in Oregon.
Habitat
Intertidal/nearshore rocky areas, kelp beds and sand patches to roughly 150 ft.
What fish is this?
The Male and Female Look Different Enough to Fool You
Female
WDFW describes females as gray to brownish with dense small reddish-brown to golden spotting and mostly yellow-orange fins.
Male
Males tend toward gray/brown/olive with irregular blue patches over the front half to two-thirds of the body, each surrounded by smaller reddish-brown spots. Early taxonomists described the sexes separately because the difference is that striking.
Source: WDFW
Structural traits
Five lateral lines, a yellowish mouth interior, small cirri above the eye/head, and the greenling body shape help when color is muted. Use structure and sex-specific pattern together instead of assuming one sex is a different species.
Source: WDFW
The first year is not a kelp-bed life
Pelagic Young, Nearshore Adults
Eggs and larvae
NOAA life-history references describe attached demersal egg masses and pelagic larvae. California summaries note larvae/early juveniles can spend a long period in the open water before joining the nearshore benthic community.
Adult habitat
Adults use rocky inshore areas, kelp beds, and sand patches from the intertidal to roughly 46 m / 150 ft. WDFW says the species is common in Puget Sound; in California it is much more common from Morro Bay northward than in Southern California.
Source: WDFW · California Marine Living Resources
Depth and size
Historical California catch data show larger kelp greenling tending deeper than the smallest fish. Treat that as a size/depth tendency rather than a law: local kelp, tide, temperature, and prey still decide which exact depth is occupied.
Source: CDFG Marine Living Resources
Spawning
Egg Masses and Guarding Males
Season varies with latitude
NOAA’s species life-history record summarizes spawning around October-November, while California work places the broader local season roughly September-January and notes hatching progressively earlier farther north. The important point is a cold-season attached-egg system whose calendar shifts geographically.
Source: AFSC · CDFW Nearshore Fishes
Male guarding
Males can guard egg masses laid on rock and may tend multiple egg masses, potentially from more than one female. That means a conspicuous male in shallow spawning habitat can be protecting recruitment, not simply sitting on a feeding station.
What does it eat?
Flexible Nearshore Forager
Baseline diet
California summaries list crabs, amphipods, polychaete worms, ascidians, and other nearshore invertebrates as regular prey after settlement.
Opportunistic shifts
When juvenile fish or herring spawn become temporarily abundant, kelp greenling shift feeding toward the windfall. That is the useful behavior: the species is a benthic generalist with the ability to exploit short pulses of concentrated prey.
How would I fish the habitat?
Kelp Edge, Rock Pocket, Sand Seam
Evidence level. Habitat and diet above are sourced. The positions below translate that documented habitat and prey into a starting plan, not an account of a rod bent over this fish.
First waterinference
Work the transition instead of only the densest kelp: rock beside kelp, sand pockets inside reef, kelp edge over boulders, and current-facing pockets where prey is exposed.
Small bottom presentationsinference
Compact jigs, small legal natural baits, and crustacean/worm profiles fit the diet. Keep them near structure without dragging permanently through it.
Prey pulsedecision rule
If herring eggs or juvenile fish are suddenly abundant, follow the food signal before insisting on the usual crab/worm pattern.
Growth and age
Females Eventually Outgrow Males
Longevity
WDFW currently reports maximum ages of at least 18 years from northern Southeast Alaska and as high as 25 years from Oregon. ADF&G’s age laboratory documents an 18-year northern Southeast Alaska fish.
Source: WDFW · ADF&G Age Determination Unit
Sex-specific growth
California’s historical synthesis reports faster early growth followed by slower male growth, with females surpassing males at older ages. That means sex as well as age can influence the size distribution on a piece of habitat.
The decision layer
What Changes the Next Cast?
Spawning male on shallow egg habitat
Recognize the guarding role before repeatedly removing fish from the same small patch.
Only small fish shallow
Check somewhat deeper nearshore structure before concluding the area lacks larger greenling.
Fish suddenly leave normal bottom baits
Look for a temporary prey pulse such as herring eggs or juvenile forage.
Male/female look different
Use the sex-specific color patterns and structure; do not create a second species from the same fish.
— · Not established
What the Sources Don’t Settle
- a single coastwide spawning month
- a universal depth separating small and large fish
- a fixed age/size relationship independent of sex and region
None of the sources here explain why bigger kelp greenling tend to turn up deeper than small ones, and it’s only a tendency anyway. If the shallow rocks keep handing you little fish, try somewhat deeper structure before you write the spot off.
If a greenling is going in the cooler, the sex difference stops being trivia and becomes the reason you look twice at what you’re holding.
— · Sources
FEEDING ECOLOGY · STANDARDIZED
How this fish gets fed.
Primary prey
Crabs, amphipods, polychaete worms, ascidians and other nearshore invertebrates are regular prey; kelp greenling can also exploit temporary pulses of juvenile fishes or fish eggs.
Feeding mode / location
A flexible bottom and near-bottom forager using rocky reef, kelp, boulders, rubble, tidepools and hard-bottom edges. It normally searches benthic habitat but can shift toward concentrated prey when a short-lived food pulse appears.
Diel / seasonal pattern
The profile does not establish one universal diel feeding window. Seasonal prey pulses can temporarily reorganize feeding, while spawning can place conspicuous males on guarded egg masses that should not be mistaken for feeding stations.
Ontogenetic diet shift
The sources behind this page don’t spell out how the diet shifts from young fish to adult.
Opportunistic prey switching is retained as a feeding behavior; nest guarding remains reproductive behavior.
Primary References
- Washington Department of Fish and Wildlife: Kelp Greenling — sex-specific identification, range, habitat, size, and age.
- Alaska Fisheries Science Center: Kelp Greenling Life History — range, habitat, attached eggs, pelagic larvae, and spawning.
- California Department of Fish and Wildlife: Nearshore Fishes — California maturity/spawning research.
- California Marine Living Resources — sex-specific growth, diet, depth, and spawning summary.
Compiled 2026-09-11. Limits and advisories are set per water and per state and change between seasons — the managing agency for wherever you are fishing has the current answer.
