Johnston’s Weedfish

Heteroclinus Johnstoni
Johnston´s Weedfish - Marinewise © 2023 MarineWise

Quick Facts

Scientific name Heteroclinus Johnstoni
Other names Southern Weedfish, Weedy Seadragon
Size Up to 40 cm (15.74 in)
Weight Under 1 kg (2.2 lb)


Habitat & AU Distribution Coastal waters amongst rocky reefs & sandy areas with vegetation rich with algae
Depth Range 1 - 15 m (49 ft)
Johnston's Weedfish Distribution

Interesting Info

  • Johnston’s Weedfish is endemic to Australia and is commonly found along the southern coastline, primarily inhabiting the eastern shores of Tasmania and extending northwards along the South Australian and Victorian coastlines.
  • They have a slender elongated body, resembling a piece of drifting seaweed. They showcase various colour patterns and can range from green to brown, often with irregular markings or spots, allowing them to blend perfectly with their rocky and weedy habitat.
  • These fish primarily feed on small invertebrates, including crustaceans, amphipods, and tiny marine worms, which they forage for in the nooks and crannies of rocky reefs.
  • Johnston’s Weedfish exhibits a remarkable ability to tolerate varying environmental conditions, including fluctuations in temperature and salinity, which allows them to survive in tide pools during low tide.
  • They has limited swimming abilities due to their modified pectoral fins, which are adapted for crawling and adhering to rocks rather than propelling through the water.
  • During the breeding season, male Johnston’s Weedfish undergo colour changes and develop vibrant patterns to attract potential mates and establish dominance among other males.
  • These fish exhibit a unique breeding behaviour known as male brood care. During the breeding season, which typically occurs in late spring and early summer, males guard the eggs in their mouths until they hatch, ensuring their safety and providing them with oxygen-rich water.
  • Their estimated average lifespan is between 3 – 4 years.
Species Interaction

Recreational Fishing, Aquarium, Snorkeling & Diving

The Johnston’s Weedfish is not a species targeted for recreational fishing but is often caught as bycatch when targeting other species. They can occasionally be found in established reef aquariums. In the wild can be an exciting experience for snorkelers and divers. Due to their camouflage ability, patience and a keen eye are necessary to spot them amidst the rocky and weedy environment. Slow and gentle movements are essential to avoid startling these shy creatures.

Scientific Classification

Kingdom: Animalia

Phylum: Chordata

Class: Actinopterygii

Order: Perciformes

Family: Clinidae

Genus: Heteroclinus

Species: Heteroclinus Johnstoni

Conservation Status

In Australia, Johnston’s Weedfish is classified as “Least Concern” on the IUCN Red List. However, due to its limited range and specific habitat requirements, monitoring its population is crucial to maintaining its status.

How to catch
Johnston’s Weedfish

Catch Difficulty: Easy

Tackle: Running Sinker Rig

Bait: Fresh cut flesh baits, Prawns, Squid, Worms

Technique: Keep bait close to the reef/structure

Popularity: Not targeted - Bycatch

Johnston’s Weedfish
As Aquarium Fish

Care Level: Moderate to difficult

Temperament: Shy

Diet: Carnivore

Reef Compatible: Yes

Minimum Tank Size: 40 gallons

Recreational Viewing
- Snorkeling & Scuba

Finding: Intermediate

Temperament: Shy

Location: Inner Reef, Lagoon

Danger: None

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