Sharks · Saltwater
Bonnethead
Sphyrna tiburo
Smallest hammerhead species, common in shallow coastal waters of the western Atlantic (North Carolina to southern Brazil, including the Gulf of America and Caribbean) and eastern Pacific (southern California to Ecuador). Notable among sharks for a documented omnivorous diet that includes digested seagrass.
Also called Bonnethead shark, Shovelhead shark, bonnet shark.
- Inshore
- Nearshore
- Regulated context
- 4 of 4 overlays reviewed
- Reviewed 2026-08-27
Open question · not settled here
The sources under this record disagree
Two bodies of evidence point different ways about how much pressure this fish can take, and the record does not pick a winner. Both positions are written out below in full. What to do about it is a person’s call, and the reviewer left it to one on purpose rather than letting a lookup decide.
Where this applies Federal Atlantic HMS EEZ waters (NOAA Fisheries) and Florida state waters (FWC) at minimum; every other Gulf and Atlantic coastal state sets its own rules again.
The reviewed context, unedited
Federal Atlantic HMS rules (NOAA Fisheries) govern federal EEZ waters; Florida state waters are governed separately by FWC, and every other Gulf/Atlantic coastal state sets its own rules again. The two regimes do not match field-for-field. Bonnethead currently carries the same light rule set as Atlantic sharpnose: no minimum size and 1 shark per person per trip federally, no minimum size and 1 shark per person per day (2-per-vessel cap) in Florida state waters, with FWC's separate shore-based permit/course applying to shore anglers. THIS SPECIES CARRIES A SEPARATE, UNRESOLVED FLAG THAT A HUMAN SHOULD RULE ON: a 2024 IUCN Red List reassessment and a peer-reviewed 2024 Frontiers in Marine Science paper both describe bonnethead as now assessed globally as Endangered — driven substantially by steep declines and taxonomic/cryptic-species findings outside U.S. waters — and the species was added to CITES Appendix II at CoP19. NOAA's own domestic species page, by contrast, states the Atlantic and Gulf of America bonnethead stock statuses are 'unknown' rather than overfished, and both stocks remain open with no minimum size in the currently active U.S. recreational fishery. This record does NOT unilaterally reclassify bonnethead as conservation_sensitive, because the domestic managing agencies have not made an overfished determination and the species is actively, legally targeted; but the global IUCN Endangered status is a real and serious signal that a person, not this record, should weigh before deciding whether presentation guidance for this species should be published, restricted, or removed. A proposed federal rule (Federal Register, published 2026-01-05, comment period closed 2026-03-06) would revise blacktip and spinner minimum size to a default 48 in and move Atlantic sharpnose and bonnethead bag limits from per-person to a per-vessel default with an annually adjustable range; as of the last check this session made, it had not been finalized. Confirm current status before relying on any figure here. Misidentification carries legal exposure: several similar-looking requiem and hammerhead sharks are federally and/or state prohibited, and a prohibited shark must be released without removing it from the water. Verify identification and the rule set for the exact water (state vs. federal) before harvest.
Rules for this fish change at a state line and sometimes inside one. Check the ones that apply to the exact water you are standing on before you act on anything here — this record is biology, not permission.
Take this somewhere
This page is the record. The reading is what happens when you add water, a season and a temperature to it — that is where the families below get ranked against each other instead of just listed.
Those three links carry the fish and nothing else. No conditions were declared on this page, so none travel, and the link says so rather than sending an empty reading.
The half nobody publishes
What this record does not know
Everything else on this page comes from a named agency or peer-reviewed source. This is the other side of that: the questions a reviewer went looking for an answer to and came back without, and the fields the record leaves empty because filling them would mean guessing.
It is here rather than at the bottom because a page that only shows what it knows is easy to read as a page that knows everything. For Bonnethead there are 10 of them.
Named by a reviewer
7Somebody looked for this and wrote down that they did not find it.
- Behaviour
Diel tendency, current-facing, depth movement, and thermal-driven behavior not sourced.
No water-temperature figures were found for this species.
- Identification
Typical (as opposed to maximum) weight not found.
Juvenile-specific appearance not resolved beyond the adult/general description.
- Forage
This session could not directly load the Leigh et al. 2018 paper (403 error on the publisher page); its seagrass-digestion finding is included because it is independently corroborated by NOAA's own species page and by a 2024 Frontiers in Marine Science review, but a direct read of the primary paper's quantitative results (e.g., percent seagrass in diet, digestibility figures) is still owed and is recorded here as a gap.
Seasonal diet emphasis not sourced.
- Season
Winter, spring, and summer entries are not supported by a sourced seasonal-movement account for this species; only the late-summer/early-fall pupping period is well documented. A genuine month-by-month or thermally-anchored seasonal calendar was not found this session.
Absent from the record
3No reviewer wrote a gap here. The field is simply empty, which is its own answer.
- Identification
No reviewed image. A photograph is only in this catalog when an agency or a named creator labelled the subject, and nobody has cleared one for this species yet.
- Presentation
No species-specific weighting rule is reviewed for Bonnethead. Its ranking comes from the shared model — season, temperature, water type, holding and forage — with nothing added for this fish in particular.
- Population context
No regional population profile is registered. The species-level reading stands on its own; it does not silently become a local one.
Where the record puts it
Water and range
Inshore
3 reviewed holding classes- Grass flat
- Sand hole
- Tidal creek
Nearshore
1 reviewed holding class- Nearshore reef
DepthShallow-water specialist; a specific depth figure was not found in the sources reviewed.
Moving waterNOAA describes bonnethead using shallow coastal water over sandy or muddy bottoms, coral reefs, and grass flats, and as common in bays and estuaries; not resolved to a finer tide-driven pattern from a sourced account.
LightNot resolved from a sourced account; recorded as a gap.
Thermal band
Temperature
- Reported active
- 68–86°F
A mix of measured preference and distribution data.
Carlson and Parsons (1999, Journal of Fish Biology) measured routine oxygen consumption of bonnethead sharks across "the entire seasonal temperature range (20-30°C)" -- i.e. the natural seasonal water-temperature span these northeastern Gulf of Mexico sharks experience from autumn through summer -- finding metabolic rate rose steadily with temperature (Q10 = 2.34). This is a lab respirometry study reflecting a real seasonal range rather than a stated preference or a catch-distribution figure, so it is recorded as mixed basis. No distinct cold/warm avoidance threshold was reported.
How it uses water
Behaviour
Widely described in the sources reviewed as common in bays, estuaries, and grass flats, consistent with loose group association typical of small coastal Sphyrnidae; a formal schooling-structure study was not reviewed this session.
NOAA and the peer-reviewed literature describe an omnivorous diet: benthic invertebrate prey (crabs, shrimp, snails) taken by grubbing/benthic feeding, alongside fish and — unusually for a shark — genuine digestion and assimilation of seagrass, not just incidental ingestion.
Not resolved to a specific diel pattern from a sourced account this session; recorded as a gap.
Spawning (conservation context)Roughly 5-month gestation; 4-14 live pups born in late summer or early fall, about 12 in at birth. Recorded as conservation context only; no pupping location is identified.
What it can eat
Forage
- Crustaceans
- Mollusks
- Small forage fish
NOAA describes an omnivorous diet of fish, crabs, snails, and shrimp 'in addition to grazing on seagrass — making them unique among sharks for this herbivorous behavior.' This is corroborated by peer-reviewed work (Leigh, Papastamatiou and German 2018, Proceedings of the Royal Society B) showing bonnethead sharks genuinely digest and assimilate seagrass rather than merely ingesting it incidentally while hunting benthic prey among grass blades — a rare, real, sourceable case of partial herbivory/omnivory in an elasmobranch. Diet capacity is not evidence of a current bait event, and seagrass consumption specifically should not be read as a targetable forage behavior — it is digestive/nutritional biology, not a bait cue.
- Feeding style
- Mixed
- Feeding zone
- Benthic
By life stage
- Adult
- Crustaceans (crabs, shrimp), mollusks (snails), small fish, and digested seagrass, per NOAA and the peer-reviewed seagrass-digestion study.
Diet capacity described here is not proof that a bait event is occurring on any given day. Observed current forage still comes from a user observation or Hatch Match. Seagrass digestion capacity in particular is a biological/nutritional finding, not a presentation cue.
Through the year
Season
Late summer
- Where they sit
- Shallow grass flats, sand holes, and bay/estuary edges.
What that changesFlats sight-cast and live/natural bait suspension are the reviewed inshore families that fit a shallow-water sight-fishing target on grass flats.
What would count against it
- treating pupping timing as a bite cue
Pupping season (late summer into early fall); no pupping location is identified.
Fall
- Where they sit
- Continues in shallow grass-flat and bay/estuary habitat; pupping continues into early fall.
What that changesSame reviewed inshore families as late summer.
Spawning · Late summer, Fall
NOAA gives a roughly 5-month gestation with 4-14 live pups born in late summer or early fall, each about 12 in at birth. Recorded as conservation context only; no pupping location is identified.
Recorded as conservation context. No spawning site, staging concentration or migration bottleneck is named anywhere in this catalog, because naming one is how a population gets fished out.
Telling it apart
Identification
What to look at
- Head is broad, smooth, and shovel- or spade-shaped rather than the strongly T-shaped, laterally scalloped head of scalloped hammerhead or the broad, flat, near-straight-edged head of great hammerhead — the single clearest mark separating bonnethead from the two federally/state-prohibited hammerheads it could otherwise be mistaken for.
- Sexually dimorphic head shape unique among sharks: adult females have an evenly rounded head margin, while adult males develop a distinct forward bulge in the center of the head once they reach maturity (NOAA).
- Scattered small dark markings on the dorsal surface and flanks over an otherwise gray, tan, or greenish back and paler belly.
- Average adult length
- NOAA: average 3-4 ft.
- Common angling size
- Most inshore recreational catches fall in the 2-4 ft range typical of the species; no minimum size currently applies in either federal or Florida state waters (see targetContext).
- Typical weight
- Not resolved to a typical figure; NOAA gives a maximum documented weight only (see maximumDocumentedSize).
- Maximum documented
- NOAA: maximum length about 5 ft, maximum documented weight 24 lb.
- Longevity
- NOAA: estimated maximum age 18 years (females), 16 years (males).
What it gets confused with
- Great hammerhead (Sphyrna mokarran)
- Federally and Florida-state PROHIBITED. Has a much broader, flatter, nearly straight-edged head and grows far larger; NOAA's own comparison note describes bonnethead's shovel-shaped head and roughly 5 ft maximum size specifically to distinguish it from great hammerhead.
- Scalloped hammerhead (Sphyrna lewini)
- Federally and Florida-state PROHIBITED. Has a distinctly scalloped (wavy-edged) hammer with a central notch, unlike bonnethead's smooth spade-shaped head.
- Smooth hammerhead (Sphyrna zygaena)
- Florida-state PROHIBITED (per FWC's prohibited list). Has a smooth-edged but much broader, more rectangular head and grows considerably larger than bonnethead.
What follows from all of that
Presentation families
Inshore
Flats sight cast
Present to a fish you have actually seen, leading it so the bait arrives without landing on it.
- spot first, cast second
- lead the fish
- quiet entry
- strip or retrieve across its path
What it asks of the tackle
- Depth control
- Low
- Sensitivity
- High
- Casting distance
- Moderate
- Weight range
- Unweighted to 1/4 oz
- Cover resistance
- Low
- Line visibility
- Low
- Retie frequency
- Moderate
Live / natural bait suspension
Present a natural food form with enough life or scent to hold in a station without looking mechanical.
- keep it alive or fresh
- match the holding depth
- minimize hardware bulk
- detect without pulling it away
What it asks of the tackle
- Depth control
- High
- Sensitivity
- High
- Casting distance
- Short to moderate
- Weight range
- As light as conditions allow
- Cover resistance
- Moderate
- Line visibility
- Low
- Retie frequency
- High
Tidal drift bait
Let a natural bait travel at the speed of the tide along an edge fish are feeding on.
- match weight to the run
- stay in the seam
- let it swing at the end
- reset up-tide
What it asks of the tackle
- Depth control
- Moderate
- Sensitivity
- High
- Casting distance
- Short to moderate
- Weight range
- 1/8–1 oz
- Cover resistance
- Moderate
- Line visibility
- Low
- Retie frequency
- High
Nearshore
Bottom contact
Keep a bait on or just above the substrate along a break, flat, or inside a weed edge.
- feel bottom
- drag or hop
- pause on the break
- stay in contact
What it asks of the tackle
- Depth control
- High
- Sensitivity
- High
- Casting distance
- Moderate
- Weight range
- 1/8–1/2 oz
- Cover resistance
- High
- Line visibility
- Low
- Retie frequency
- High
What moves them for this fish
No species-specific rule is reviewed for Bonnethead. Its ranking comes from the shared model — season, temperature, water type, holding water, forage — with nothing added for this fish in particular. That is a gap, not a claim that nothing is special about it.
Where every sentence came from
Sources
Agency
NOAA Fisheries, Bonnethead Shark species overview
Used for habitat, thermal band and presentation families; identification; behaviour; forage; season. Read 2026-08-30, next check 2026-11-27.
Agency
NOAA Fisheries, Bonnethead Shark: Science
Used for habitat, thermal band and presentation families; identification; behaviour. Read 2026-08-30, next check 2026-11-27.
Agency
NOAA Fisheries, Recreational Atlantic Shark Fishery Statuses, Minimum Sizes, and Retention Limits
Used for habitat, thermal band and presentation families. Read 2026-08-27, next check 2026-11-27.
Agency
Used for habitat, thermal band and presentation families. Read 2026-08-27, next check 2026-11-27.
Agency
NOAA Fisheries, HMS Recreational Compliance Guide 2025 (permit, shark endorsement, circle hook rule)
Used for habitat, thermal band and presentation families. Read 2026-08-27, next check 2026-11-27.
Agency
Used for habitat, thermal band and presentation families. Read 2026-08-27, next check 2026-11-27.
Peer reviewed
Used for habitat, thermal band and presentation families. Read 2026-08-27, next check 2026-11-27.
Peer reviewed
Used for habitat, thermal band and presentation families. Read 2026-08-27, next check 2026-11-27.
Peer reviewed
Used for forage. Read 2026-08-30, next check 2026-12-08.
Synthesis
Used for habitat, thermal band and presentation families. Read 2026-08-27, next check 2026-11-27.
A source with no link predates the rule that one has to carry a URL. It is still a real citation and still checkable; it just takes a search rather than a click, and that is worth knowing before you rely on it.