Gizzard Shad / Dorosoma cepedianum

At-a-glance biology

• Size at age (western Lake Erie): males Age 1 = 141 mm (5.5 in), Age 2 = 273 mm, Age 3 = 313 mm, Age 4 = 343 mm, Age 5 = 349 mm; females Age 1 = 140 mm, Age 2 = 285 mm, Age 3 = 335 mm, Age 4 = 364 mm, Age 5 = 386 mm per Tier 3 Bodola 1966. Maximum length ~52 cm (~20.5 in) per Tier 3 USGS NAS.
• Great Lakes status: cryptogenic in the southern Great Lakes (Ontario, Lake St. Clair, southern Lake Erie, southern Lake Michigan) per Tier 3 USGS NAS -- native-vs-introduced is uncertain in these basins. Honest framing avoids collapsing to "native" or "introduced".
• Spawning thermal trigger: ~67 deg F water temperature in western Lake Erie; spawning early June into July, peak mid-June (Tier 3 Bodola 1966).
• Optimal thermal range: 22-29 deg C (~72-84 deg F) per Tier 3 USGS NAS. This is the SAME band as the trout/steelhead heat-stress threshold -- shad activity peaks where steelhead are already stressed.
• Diet: juveniles eat copepods + cladocerans; adults are planktivorous filter-feeders straining phytoplankton + zooplankton + detritus (~13% of wet-weight biomass daily in bottom sediments per USGS NAS).
• Winterkill threshold: Tier 3 Fetzer et al. 2011 controlled-treatment experiments showed low mortality above 46 deg F and high mortality below 39 deg F; cold stress (not starvation) is the primary driver; YOY shad die fastest within each treatment.

Source-disciplined claim summary

Gizzard shad is a Lake Erie food-web anchor for warmwater predators -- the GLFC Lake Erie Forage Task Group March 2016 report (Tier 1) documents 2015 adult walleye diets as over 84 percent gizzard shad by dry weight, and age-0 gizzard shad accounted for 34 percent of fall diets for both Smallmouth Bass and White Bass. This is the source-backed anchor for the gizzard-shad pattern-mapping entry defaulting target_species to walleye + smallmouth_bass. Historical YOY walleye diet context per Tier 3 USGS adds further evidence: young-of-year walleyes in extreme western Lake Erie fed primarily on gizzard shad and alewives in summer, shifting to emerald shiners in fall.

The steelhead-specific claim is intentionally NOT made. Per Tier 1 GLFC 2004 Coldwater Task Group, the documented Lake Erie steelhead top prey items at the n=349 stomach sampling scope (West Central Basin June-October overall) were emerald shiner, rainbow smelt, round goby, and juvenile yellow perch -- gizzard shad was NOT among top documented prey. Two non-exclusive structural explanations are honest to preserve: (a) by Age 1, gizzard shad are already 5.5 inches and outgrow steelhead mouth gape, while the documented diet items sit comfortably below that band; (b) GLFC 2004 sampled stomachs primarily July-August, after the spring window when YOY gizzard shad are smallest and most predator-vulnerable, and away from any post-winterkill shoreline-scavenging window. The absence is a sampling/selectivity-scope observation, NOT proof steelhead never eat gizzard shad.

Current population status per Tier 1 GLFC FTG March 2026: 2025 age-0 gizzard shad biomass was 0.8 kg/ha, down 74.8 percent from 2024 and 75.4 percent below the 2014-2024 mean. YOY year-class strength is currently low. Cold-front winterkill remains a documented mechanism per Tier 3 Fetzer et al. 2011, with harbors and lower river sections as the documented winterkill zones for both gizzard shad and white perch -- placing periodic shoreline-dead-shad windows near steelhead access points.

Honest gaps

• Tier 1-3 quantitative steelhead-on-gizzard-shad diet selectivity for Lake Erie tributaries -- no source surfaced at present.
• Current adult walleye + smallmouth bass quantitative gizzard-shad selectivity beyond the GLFC FTG 2015 snapshot [source-required].
• Tributary-specific winterkill incident timing for Steelhead Alley harbor mouths [source-required].
• Quantitative steelhead gape-limit thresholds (which steelhead size class can consume which shad size class) [source-required].
• Wind-driven dead-shad concentration patterns at named harbor mouths [source-required].
• Lake Ontario applicability is outside this Lake Erie-focused profile's scope.

Where this matters to anglers

Pattern selection priority for shad imitations at the Lake Erie scope is walleye > smallmouth bass >> steelhead/trout. For per-river presentation: pearl/silver shad-profile streamers (deep-belly Game Changer baitfish, Sex Dungeon white/silver, Murdich Minnow pearl), Sparkle Minnow at size 1/0 to 4 for adult-class or 4-8 for YOY-class. For gear/spin: paddle-tail swimbaits + jigging spoons in pearl/silver/chrome, Cleo-style spoons, soft-plastic shad bodies on jig heads. Cast and retrieve along harbor mouths and lower tributary sections during warmwater walleye/smallmouth windows; troll for open-water walleye summer feeding; jig spoons in deeper offshore zones where shad schools suspend.

Critical steelhead caveat: gizzard shad is NOT a documented Lake Erie steelhead diet item at the GLFC 2004 sampling scope, and the gizzard-shad pattern-mapping entry intentionally excludes steelhead/trout from default target_species. Shad-pattern flies have a defensible place in the open-water + harbor-mouth predator rotation, but DO NOT promote gizzard shad as a primary steelhead pattern. The most defensible steelhead-adjacent gizzard shad window is post-winterkill shoreline scavenging in late winter / early spring (water 34-46 deg F per Fetzer Tier 3 evidence) -- and even that linkage is translation heuristic until a steelhead-diet study captures it.

See also

• Gizzard Shad Lifecycle (Long-Form Profile) -- the full source-disciplined working profile with predator-diet detail, winterkill mechanism, and pattern-mapping notes.
• Lake Erie Goby Takeover -- companion forage-shift coverage explaining how smallmouth bass and walleye diets reshuffled around the invasive round goby; gizzard shad sits in that same warmwater predator forage pool.
• Source Discipline and the Tier Hierarchy -- the Tier 1-3 evidence framework behind every source-status label on this page.

Source list