🔍

Hull Biofouling
ID Guide

Quick reference for divers cleaning ship hulls in Queensland waters

📍 QUEENSLAND Field Pocket Guide — Tropical Focus
⚠️ 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

Queensland's tropical waters are vulnerable to tropical pests. The Great Barrier Reef, Torres Strait, and major ports at Brisbane, Gladstone, Townsville, and Cairns need protection. Divers are the first line of defence.

PROHIBITED — Prohibited/Restricted under QLD Biosecurity Act. Report immediately.
WATCH — Emerging threat. Report within 24 hours
NATIVE — Normal QLD 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
2

PROHIBITED — Report Immediately

Page 1 of 4
Asian Green Mussel PROHIBITED
Asian Green Mussel
Perna viridis
PROHIBITED - Tropical Origin
  • Young = bright emerald green
  • Older = brownish-green
  • Big — 80-165mm (hand-sized)
  • Blue-green iridescent inside
  • QLD waters ideal for this species!
Don't confuse with: Blue mussel — blue-black, not green
Black-striped False Mussel PROHIBITED
Black-striped False Mussel
Mytilopsis sallei
PROHIBITED - Tropical Pest
  • Small — only 20-25mm (thumbnail)
  • Dark radiating stripes on shell
  • Prefers brackish/estuarine water
  • Darwin eradication cost $2.2M
  • Check sea chests!
3

PROHIBITED — Report Immediately

Page 2 of 4
Harris Mud Crab PROHIBITED
Harris Mud Crab
Rhithropanopeus harrisii
PROHIBITED - Not in Australia
  • Small (up to 25mm carapace)
  • Dark olive to brown colour
  • 3 spines each side between eyes
  • White-tipped claws
  • Lives in estuaries, sea chests
QLD Priority: On Biosecurity QLD's priority invasive species list. Major threat to estuarine environments.
Charru Mussel PROHIBITED
Charru Mussel
Mytella strigata
PROHIBITED - Tropical
  • Medium 22-50mm
  • Variable: black, brown, orange, green
  • Zigzags, spots, or bands
  • Blue-purple opalescent inside
  • Yellowish flesh — very variable!
4

PROHIBITED — Report Immediately

Page 3 of 4
Carpet Sea Squirt PROHIBITED
Carpet Sea Squirt
Didemnum vexillum
PROHIBITED - Not in QLD
  • Creamy/tan to yellow-grey
  • Waxy, veiny like varicose veins
  • Leathery feel, NOT slimy
  • Drips down like candle wax
  • Smothers EVERYTHING!
Don't confuse with: Native sea squirts — thinner, gelatinous, no veiny texture
White Colonial Sea Squirt PROHIBITED
White Colonial Sea Squirt
Didemnum perlucidum
ESTABLISHED - QLD
  • White or see-through
  • Thin sheet — hugs the surface
  • Smooth, not lumpy
  • Can see tiny dots inside
  • Found in some Aus ports
5

PROHIBITED — Report Immediately

Page 4 of 4
Asian Date Mussel PROHIBITED
Asian Date/Bag Mussel
Arcuatula senhousia
PROHIBITED - QLD
  • Small — only up to 30mm
  • Thin, fragile, easily crushed
  • Greenish with zigzag markings
  • Iridescent radiating bands
  • Forms mats — smothers seagrass
Chinese Mitten Crab PROHIBITED
Chinese Mitten Crab
Eriocheir sinensis
PROHIBITED - Species
  • Dense hair "mittens" on claws
  • White-tipped claws
  • Up to 80mm carapace
  • Olive-brown, 4 spines per side
  • Can carry lung fluke parasite
6

PROHIBITED / WATCH Species

Additional Priority Species
Killer Algae PROHIBITED
Killer Algae
Caulerpa taxifolia
PROHIBITED - GBR Risk!
  • Bright green - stands out
  • Feather-shaped fronds
  • Creeping runners
  • Up to 65cm tall
GBR Threat: Smothers native seagrass and coral. Can survive in anchor wells. Report any sighting!
Black Scar Oyster ESTABLISHED
Black Scar Oyster
Magallana bilineata
ESTABLISHED - QLD 2019
  • Small-medium sized oyster
  • Black scar inside shell
  • Detected in QLD & NT
  • Report new locations!
7

PROHIBITED — QLD Priority Pests

Check Vessels from South
Japanese Kelp Wakame PROHIBITED
Japanese Kelp (Wakame)
Undaria pinnatifida
PROHIBITED - Not in QLD
  • Large brown fronds 1-3m long
  • Prominent midrib down centre
  • Wavy/ruffled edges
  • Attached to hard surfaces
QLD Priority: On Biosecurity QLD list. Established in VIC/TAS but NOT in QLD waters. Report any sighting!
Brown Mussel PROHIBITED
Brown Mussel
Perna perna
PROHIBITED - Africa/S. America
  • Dark brown to black shell
  • Up to 90mm (fist-sized)
  • Dense thick clumps
  • Thick shell, hard to break
8

Native — Normal QLD Fouling

No Report Needed
Native Mussels NATIVE
Blue/Native Mussels ✓
Mytilus spp.
Mussel — Common
  • Blue-black shell
  • Triangular/wedge shape
  • Clumps with byssal threads
  • NOT bright green!
Native Tube Worms NATIVE
Native Serpulid Worms ✓
Serpulidae & Spirorbidae
Tube Worm — Common
  • Hard white calcium tubes
  • Small feathery fans (<20mm)
  • Christmas tree worms on coral
  • NOT big brown leathery tube
QLD Established Oysters: Black Scar Oyster (Magallana bilineata) and Suminoe Oyster (M. ariakensis) are established in QLD waters. Large oysters require lab ID — photograph all suspicious oysters for reporting.
9

Quick Reference Table

HIGH Priority Quick ID
Asian Green Mussel Bright green shell, 80-165mm — tropical threat!
Black-striped Mussel Small 25mm, dark stripes, sea chests
Harris Mud Crab Small 25mm, white-tipped claws, 3 spines each side
Charru Mussel Variable colors, 22-50mm, blue inside
Carpet Sea Squirt Creamy veiny mat, waxy texture
Asian Date Mussel 30mm, fragile, zigzag, forms mats
Chinese Mitten Crab Hairy "mittens" on claws
Japanese Kelp (Wakame) Large brown fronds 1-3m, midrib down centre
Brown Mussel Dark brown-black, up to 90mm, thick shell
Killer Algae Bright green feathery fronds, creeping runners
Native Species Key Difference from Invasive
Blue Mussel Blue-black shell, NOT green
Native Tube Worms Small fans (<20mm), white hard tubes
Native Crabs Most lack paddle-shaped back legs
10

Report It — Queensland

🚨 Biosecurity Queensland

13 25 23
DAF Call Centre
marinepests@daf.qld.gov.au

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 — Queensland • Version 3.0 • January 2026

© 2026 MarineStream • Info from DAFF, Biosecurity QLD, NIMPIS

11

Notes