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Hull Biofouling
ID Guide

Quick reference for divers cleaning ship hulls in South Australian waters

📍 SOUTH AUSTRALIA Field Pocket Guide
⚠️ Found something dodgy? STOP & REPORT

Version 3.0 • January 2026

How to Use This Guide

The Job

You're cleaning hulls. You need to spot the bad stuff before you scrape it off. This guide shows you what to look for and what to report.

Why It Matters

South Australia's gulfs and coastal waters support valuable aquaculture. European fan worm and Japanese kelp are established. The Northern Pacific Seastar could devastate SA fisheries if it arrives. Divers are our early warning system.

DECLARED — Declared pest under Landscape SA Act. Report to PIRSA/Fishwatch.
ESTABLISHED — Present in SA. Prevent further spread.
MEDIUM — Watch species. Report within 24 hours
NATIVE — Normal SA fouling, no report needed

⚠️ Found Something Dodgy?

  • STOP cleaning in that area
  • Take photos — close-up + wide shot, use hand for scale
  • Note location (bow distance, depth, port/stbd)
  • DON'T scrape it off until reported
  • Surface and tell your supervisor
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DECLARED — Report Immediately

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Northern Pacific Seastar DECLARED
Northern Pacific Seastar
Asterias amurensis
DECLARED - Aquaculture Threat!
  • HUGE — up to 50cm diameter
  • 5 arms with upturned tips
  • Yellow-orange with purple marks
  • Undersides completely yellow
  • Could devastate SA oysters!
Critical: Established in VIC/TAS. Would be catastrophic for SA aquaculture if introduced!
Carpet Sea Squirt DECLARED
Carpet Sea Squirt
Didemnum vexillum
DECLARED - Not in SA
  • Creamy/tan to yellow-grey
  • Waxy, veiny like varicose veins
  • Leathery feel, NOT slimy
  • Can thicken to 10cm
  • Smothers EVERYTHING!
Don't confuse with: Native sea squirts — thinner, gelatinous, no veiny texture
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DECLARED — Report Immediately

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Asian Green Mussel DECLARED
Asian Green Mussel
Perna viridis
DECLARED - Not in Australia
  • Young = bright emerald green
  • Older = brownish-green
  • Big — 80-165mm (hand-sized)
  • Blue-green iridescent inside
  • Check sea chests carefully
Don't confuse with: Blue mussel — blue-black, not green
Killer Algae DECLARED
Killer Algae
Caulerpa taxifolia
DECLARED - Not in SA
  • Bright green - stands out
  • Feather-shaped fronds
  • Creeping runners
  • Up to 65cm tall
  • Smothers everything!
Also Watch: Black-striped False Mussel (Mytilopsis sallei) — 20-25mm, dark stripes, check sea chests. Charru Mussel (Mytella strigata) — variable colors, blue-purple inside. Both DECLARED.
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ESTABLISHED in SA — Prevent Spread

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European Fan Worm EST
European Fan Worm
Sabella spallanzanii
ESTABLISHED - SA Ports
  • HUGE fan — 45-150mm across
  • Fan spirals inward (not flat)
  • Stripy — orange/purple/white bands
  • Brown leathery tube up to 400mm
  • Report outside known areas!
Don't confuse with: Native serpulid worms — smaller fans (<20mm), white hard tubes
Japanese Kelp EST
Japanese Kelp (Wakame)
Undaria pinnatifida
ESTABLISHED - SA
  • Large 1-3m, golden-brown
  • Central midrib runs full length
  • Wavy ruffled edges
  • Frilly sporophyll at stalk base
  • Smothers native kelp forests
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ESTABLISHED in SA — Prevent Spread

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European Shore Crab EST
European Shore Crab
Carcinus maenas
ESTABLISHED - SA Coast
  • Olive to dark green, 50-90mm
  • 3 blunt spines on rostrum
  • 5 spines each side of eyes
  • NO swimming paddles
  • Hides in sea chests
Asian Date Mussel EST
Asian Date/Bag Mussel
Arcuatula senhousia
ESTABLISHED - SA
  • Small — only up to 30mm
  • Thin, fragile, easily crushed
  • Greenish with zigzag markings
  • Iridescent radiating bands
  • Forms mats — smothers seagrass
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WATCH — Watch Species

Report within 24 hours
NZ Green-lipped Mussel WATCH
NZ Green-lipped Mussel
Perna canaliculus
DECLARED - NZ Vessels
  • Green "lip" on shell edge — key ID
  • Dark brown to bright green shell
  • MASSIVE — up to 240mm
  • Check vessels from New Zealand
Vase Tunicate WATCH
Vase Tunicate
Ciona intestinalis
ESTABLISHED - SA
  • Translucent yellow-green
  • Tube/vase shaped, up to 150mm
  • Two siphons at top
  • Soft and squishy texture
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Native — Normal SA Fouling

No Report Needed
Blue Mussel NATIVE
Blue Mussel ✓
Mytilus galloprovincialis
Mussel — Common SA
  • Blue-black shell, 50-100mm
  • Triangular/wedge shape
  • Clumps with byssal threads
  • NOT green — that's Asian one
Native Tube Worms NATIVE
Native Serpulid Worms ✓
Serpulidae & Spirorbidae
Tube Worm — Common
  • Hard white calcium tubes
  • Small feathery fans (<20mm)
  • Spirorbids are tiny 3mm coils
  • NOT big brown leathery tube
Native Sea Squirts: Thin jelly-like mats, various colours, NOT veiny/waxy. If unsure between native and invasive — always report it.
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Quick Reference Table

HIGH Priority Quick ID
Northern Pacific Seastar NOT in SA! 50cm, 5 upturned arms, yellow-orange
Carpet Sea Squirt Creamy veiny mat, waxy texture
Asian Green Mussel Bright green shell, 80-165mm
Black-striped Mussel Small 25mm, dark stripes, sea chests
Established SA Status & Notes
European Fan Worm Huge spiral fan 45-150mm, brown tube
Japanese Kelp 1-3m brown, central midrib, frilly base
European Shore Crab 5 spines beside eyes, no paddle legs
Asian Date Mussel 30mm, fragile, zigzag, forms mats
Native Species Key Difference from Invasive
Blue Mussel Blue-black shell, NOT green
Native Tube Worms Small fans (<20mm), white hard tubes
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Report It — South Australia

🚨 PIRSA Fishwatch

1800 065 522
24-hour Fishwatch hotline
pir.sa.gov.au/biosecurity/aquatics

MarineStream

Biofouling Manager:
Mat Harvey

Operations Manager:
Sam Diamond

www.marinestream.com.au

National Resources

Marine Pests:
www.marinepests.gov.au

NIMPIS Database:
nimpis.marinepests.gov.au

✓ When Reporting, Include:

  • Photos — close-up + wide shot with hand for scale
  • GPS coordinates if possible
  • Location on hull (bow distance, depth, port/stbd)
  • Vessel name and current location
  • Date and time of sighting
  • Your contact details

Hull Biofouling ID Guide — South Australia • Version 3.0 • January 2026

© 2026 MarineStream • Info from DAFF, PIRSA, NIMPIS

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