The Goby Takeover

In 1993, a thumb-sized invasive baitfish showed up in Lake Erie. Within a decade, it had rewritten the smallmouth bass diet from the bottom up. The seven-decade angling reflex that says "smallmouth eat crayfish, throw a craw pattern" is now describing a forage relationship that the food web largely moved past two human generations ago.

This article walks through the evidence, the timeline, the ecological mechanism, and the practical translation: when to keep the craw pattern in rotation, when to lead with a goby imitation, and where the sculpin streamer fits in a cold tributary reach that the goby invasion hasn't fully colonized.

The headline numbers, side by side

Before the round goby arrived in Lake Erie -- documented as first appearing in 1993 by Steinhart, Stein, and Marschall -- smallmouth bass diet was crayfish-centric. After it arrived, that shifted hard.

Three Tier 1-3 measurements anchor the story:

• Pre-invasion historical: crayfish occurred in 53.5% of Lake Erie smallmouth bass diets per the NYSDEC 2024 Lake Erie Smallmouth Bass and Yellow Perch Diet Analysis (Tier 1, citing historical pre-round-goby data).
• Post-invasion historical: round goby occurred in 73.3% of stomachs in the post-goby historical samples summarized by NYSDEC 2024 (Tier 1).
• September 2023, Eastern Basin, n=25 stomachs: round goby at 64.0% occurrence and 60.8% of total diet volume; crayfish at 8.0% occurrence and 6.8% volume (NYSDEC 2024, Tier 1).

A separate Steinhart, Stein, and Marschall study (Journal of Great Lakes Research, 2004) of first-year smallmouth bass in New York Lake Erie waters during 1999-2001 found that 75% of the fish those young smallmouth consumed were round gobies -- a multi-year, fish-prey-specific measurement that quantifies just how quickly the invasion remade the foraging menu for a single year-class.

In the span of about a decade after the goby invasion, the dominant smallmouth bass prey item flipped from a native crustacean to an invasive benthic baitfish. Three decades on, it is still flipped.

Sources:
NYSDEC, "Lake Erie Smallmouth Bass and Yellow Perch Diet Analysis" (March 2024) -- Tier 1
Steinhart, Stein, Marschall (2004), Journal of Great Lakes Research -- Tier 3

Where the goby came from, and how fast it spread

Round goby (Neogobius melanostomus) is native to the Black, Caspian, and Azov Seas. It arrived in North American waters through ballast-water introduction, with the first US detection in 1990 in Michigan per the USGS Nonindigenous Aquatic Species species profile. Within three years it was in Lake Erie. Within a decade it was established in all five Great Lakes plus tributary systems across eleven US states.

Three biological traits made the takeover thorough:

• Reproductive intensity. Females mature at one to two years and spawn every twenty days during the April-September window, with clutch sizes between 100 and 4,000 eggs per spawn per USGS NAS.
• Substrate preference matches smallmouth habitat. Goby densest densities are in 1-50 meter depths over rocky and sandy bottoms -- the same nearshore structure where smallmouth bass concentrate. Steinhart et al. measured nearshore goby densities exceeding 100 individuals per square meter in juvenile smallmouth habitat post-invasion. That is not a sparse forage population; it is saturating.
• Dietary versatility, with a dreissenid keystone. The USGS Central Lake Erie energy-pathway publication documents goby diet at 40.2% zooplankton and 38.3% dreissenid mussels by biomass. Goby is one of the very few benthivores that can crack zebra and quagga mussels -- meaning it harvests energy that was previously a dead-end input to the lake and pumps it back up into the food web.

The dreissenid connection is the structural reason the diet shift held. Round goby appeared with a built-in food supply (the also-invasive dreissenid mussels carpeting Lake Erie's rocky substrate) and immediately became the conduit moving that energy upward to fish-eating predators. Smallmouth bass, walleye, and a growing list of warmwater piscivores discovered, simultaneously, an abundant, calorie-dense, structure-oriented prey item that was effectively new to the lake.

Sources:
USGS NAS, Round Goby species profile (revised June 2026) -- Tier 3
USGS, "A potential new energy pathway in Central Lake Erie: The round goby connection" -- Tier 3
NOAA GLERL, Lake Erie Food Web brochure -- Tier 1

Why crayfish mattered, and what's left of them

Before goby, crayfish were the cornerstone of Lake Erie smallmouth diet. That 53.5% historical occurrence figure is not a coincidence -- it reflects a food web in which Cambaridae populations across the rocky nearshore and tributary cobble reaches were the most reliable single forage item for an opportunistic, structure-oriented predator. The Allison, Khan, Lieb, and Loughman 2019 peer-reviewed reassessment of Pennsylvania's Lake Erie basin documents at least seven native crayfish species across 54 stream sites, with Cambarus robustus (Big Water Crayfish), Faxonius propinquus (Northern Clearwater Crayfish), and Cambarus carinirostris (Rock Crayfish) most abundant. Crayfish were everywhere and smallmouth ate them.

What's striking about the post-invasion picture is what didn't happen. Crayfish weren't wiped out. The September 2023 NYSDEC sample still shows 8.0% occurrence and 6.8% volume -- non-zero, real, persistent. Native crayfish are still in Lake Erie tributaries, still in cobble-and-log-jam cover, still getting eaten when a smallmouth finds one. The food web didn't lose crayfish. It just gained a forage item so abundant and so calorie-dense that crayfish dropped from the dominant share to a meaningful-but-secondary share.

There's also a complicating factor: rusty crayfish (Faxonius rusticus), an aggressive native-displacer documented as cryptogenic in Lake Erie per USGS NAS, has been observed displacing native crayfish where established. In tributary stretches where rusty crayfish has pushed out native Cambaridae, the local crayfish forage base is itself shifting -- a smaller, more invasive-skewed cohort that is biologically still crayfish but ecologically a different system. Angler implication: olive-brown 1.5-3 inch craw patterns in hook 4-8 are still the right translation band, but local guides and shop intelligence carry weight on which streams have intact native crayfish populations and which have shifted.

Sources:
Allison et al. (2019), Proceedings of the West Virginia Academy of Science -- Tier 3
USGS NAS, Faxonius rusticus species profile -- Tier 3
PFBC, Aquatic Invasive Species program -- Tier 1

The translation: how the box should change

If the smallmouth diet evidence is the road map, the practical box for Lake Erie smallmouth (and the warmwater-window targets that come on as steelhead/trout pull back at 68-70 deg F) reorganizes around three patterns instead of one.

Lead with a goby imitation

For Lake Erie smallmouth bass during the post-spawn through pre-winter window, a goby-imitation streamer or jig is now the higher-percentage opening choice in structurally appropriate water.

• Streamers: sculpin-profile goby imitations weighted to swim near bottom, mottled olive-brown with the dorsal-spot marking that mimics goby's diagnostic black-spotted dorsal fin. Hook 1/0 to 4 matches the documented 4-7 inch adult goby size range (PA Sea Grant + USGS NAS).
• Tube jigs and ned rigs: 2.5 to 4 inch tube jigs in brown, green pumpkin, or black/red flake; drop-shot rigs with goby-pattern swimbaits; ned rigs with mushroom-head jigs. These translate most directly to the documented diet evidence.
• Presentation: bottom-bouncing along rocky substrate transitions, under woody debris cover, through the structurally rich nearshore zones where the documented 100/m^2 goby densities live. Goby is benthic. Patterns must work near bottom.

Keep the crayfish in rotation

The 8% / 6.8% September 2023 numbers are non-zero and the historical 50%+ diet share didn't vanish from the food web overnight. Crayfish patterns still produce on Lake Erie smallmouth -- they are just now a complementary piece rather than the default.

• Flies: weighted Woolly Bugger (olive/brown), Clouser Crayfish, Whitlock Near-Nuff Crayfish in hook 4-8 to match the 1.5-3 inch native Cambaridae body-length band. Bright orange/red for muddy water.
• Soft plastics and jigs: craw-pattern jigs and tubes in olive/brown for cover edges and rocky substrate.
• Where they shine: cobble cover, log jams, ledge transitions where a goby imitation would hang in structure that a craw pattern walks through more cleanly.

Reserve the sculpin streamer for cold-water tributary reaches

Native sculpin (Cottus bairdii and relatives) are a documented competitor that round goby aggressively displaces for spawning sites per USGS NAS. In Lake Erie tributary cold-water reaches where goby has established, native sculpin populations may be reduced -- meaning a goby pattern may be the better-supported choice even in water that historically held sculpin.

But in upper tributary reaches where coldwater conditions persist and goby pressure is lighter -- the same reaches that hold steelhead during cold-water windows -- sculpin patterns retain their traditional role. The mottled olive-brown sculpin streamer is no longer the universal "benthic dark baitfish" answer it was before goby invaded the system; where you fish and against what target now matters more than it used to.

Sources:
USGS NAS, Mottled Sculpin (Cottus bairdii) species profile -- Tier 3
GLFC Coldwater Task Group, "An Analysis of the Diet of Steelhead Trout in Lake Erie" (~2004) -- Tier 1

What the goby invasion did to the rest of the system

The smallmouth diet flip is the cleanest version of the story, but Round goby's establishment reshaped Lake Erie in ways that matter beyond what's on a smallmouth's plate.

Smallmouth bass length-at-age increased post-invasion. Steinhart et al. documented that first-year smallmouth grew faster after the goby arrived -- abundant calorie-dense forage facilitated the year-of-life transition into piscivory and supported accelerated growth. Better fish, in part, because of an invasive prey base. That is an ecological adjustment, not a positive outcome.

Goby preys on native fish eggs. USGS NAS documents round goby predation on lake trout eggs and other native fish eggs. Ohio Lake Erie historical smallmouth nest-protection rules were rooted partly in concerns about goby nest predation. Current ODNR 2026-27 regulations list May 1-June 26, 2026 as a restricted harvest window for Lake Erie black bass (one fish, 18-inch minimum), not a full closure -- check the current regulation before any nest-season recommendation.

Sculpin and other native competitors are under pressure. USGS NAS documents round goby competing aggressively with mottled sculpin for spawning sites. Where goby has displaced sculpin in nearshore and lower-tributary substrate, anglers are seeing fewer sculpin in the cold-tributary reaches that used to hold them densely.

Sources:
Steinhart, Stein, Marschall (2004), Journal of Great Lakes Research -- Tier 3
USGS NAS, Round Goby species profile -- Tier 3
ODNR, Ohio Fishing Regulations 2026-27 -- Tier 1

What we don't know yet

Several things you might want to know are not in the public record at search depth, and we won't invent them:

• Current adult walleye goby-selectivity, quantified. Walleye eat round goby -- widely acknowledged in Lake Erie fisheries discussion -- but a contemporary adult walleye diet study giving a goby-occurrence percentage parallel to the NYSDEC smallmouth numbers is not in the sources we found.
• Steelhead goby-selectivity in Lake Erie tributaries, quantified. The GLFC 2004 Coldwater Task Group steelhead diet analysis lists round goby as a documented prey item but not at the top biomass levels (those are emerald shiner and rainbow smelt). A tributary-specific study would close this gap.
• Lake trout goby-diet share in Lake Erie. A 36% Lake Ontario figure surfaced in general search but needs primary source confirmation; we are not citing it without a Tier 1-3 anchor.
• Tributary-by-tributary goby distribution within Ohio and New York rivers. PA Sea Grant documents goby in PA Lake Erie plus French Creek + Fairview Gravel Pits + Lake LeBeouf. Comparable named-tributary data for Ohio (Conneaut, Chagrin, Rocky, Vermilion, Grand, Cuyahoga) and NY (Cattaraugus, Chautauqua, Eighteen Mile, Canadaway) is not surfaced at search depth.
• Quantitative predator size-class selectivity. Which goby size does each smallmouth size target? The Steinhart and NYSDEC studies document overall composition; selectivity-by-size is a finer-grained question that would inform pattern-size choice more precisely.

If you have access to studies that close any of these gaps, send them along.

The takeaways

The story in one paragraph: Round goby invaded Lake Erie in 1993. Within a decade, smallmouth bass diet flipped from approximately 53.5% crayfish occurrence (pre-invasion historical, NYSDEC 2024) to approximately 73.3% goby occurrence (post-invasion historical, NYSDEC 2024) and 75% goby share of fish prey in first-year smallmouth during 1999-2001 (Steinhart et al. 2004). The September 2023 NYSDEC Eastern Basin sample puts goby at 64.0% occurrence and 60.8% volume, with crayfish at 8.0% occurrence. The flip held.

For the smallmouth box (summer warmwater windows):

• Lead pattern: goby-imitation streamer or tube jig in mottled olive-brown, hook 1/0 to 4, worked along rocky substrate transitions and structure edges.
• Complement: crayfish pattern in olive/brown, hook 4-8, for cobble cover and log-jam structure where bottom-hugging craw imitations work cleaner than streamers.
• Conditional: sculpin pattern in cold upper-tributary reaches where goby is less established.

For the steelhead box (cold-water windows): the GLFC 2004 diet evidence puts emerald shiner and rainbow smelt at the top of the documented prey list, not goby. Cold-water tributary steelhead patterns still center on shiner-and-smelt imitations, sucker spawn during the spring 50 deg F window, and traditional egg patterns -- with goby and sculpin extensions remaining translation heuristic until a Lake-Erie-tributary-specific quantitative steelhead diet study anchors them.

For warmwater conditions (water 68-70 deg F or above): shift away from steelhead/trout per state-agency thermal guidance. The post-invasion smallmouth fishery, with goby as its primary forage anchor, is one of the strongest evidence-backed warmwater options Lake Erie has.

Why we're publishing this

SHA is building toward being the authoritative source for Steelhead Alley entomology and biology. The round-goby story is the single best-documented diet shift in the Lake Erie food web -- the numbers are specific, the timeline is dated, the mechanism is understood. Most fishing content addresses it with a one-line "smallmouth eat goby now" assertion that loses the texture: the 53.5% historical anchor, the 73.3% post-invasion shift, the 75% first-year-smallmouth Steinhart figure, the September 2023 64.0%/60.8% current measurement, and the persistent-but-secondary 8% crayfish share that means the older pattern still works just not as the default.

If you fish Lake Erie smallmouth, this is the evidence we'd want you to have before opening the box.

Full source list

Continue learning

• The Steelhead Alley Seasonal Calendar -- the annual rhythm placing goby visibility in the seasonal Alley forage picture.
• Steelhead Forage Briefing -- the broader forage framework round goby fits into.
• Crayfish Life Cycle -- the crayfish lifecycle pillar -- crayfish are the prey class round goby largely displaced.