Twospine Blackfish

Interesting Info

• The Twospine Blackfish is a small, secretive freshwater fish found in the upland rivers and creeks of southeastern Australia, mainly in Victoria and southern New South Wales.
• It gets its name from the two spines at the front of its dorsal fin, which help distinguish it from the closely related River Blackfish (Gadopsis marmoratus).
• They are generally slim-bodied compared to River Blackfish, with olive-brown to dark grey colouring and fine mottling that blends perfectly with cobbles and leaf litter on stream beds.
• They prefer cool, clear, fast-flowing upland streams with rocky bottoms, boulders, and woody debris that provide plenty of hiding places.
• Twospine Blackfish are mainly nocturnal ambush predators, feeding on aquatic insects, crustaceans, and sometimes small fish.
• Historically, they were more widespread, but now their distribution is patchy and fragmented, restricted to certain tributaries of the Murray–Darling Basin and nearby upland catchments.
• They are considered poor dispersers, rarely moving far from their home pools, which means local populations are easily isolated.
• Breeding occurs in spring and early summer (October–December) when water temperatures rise. Females lay adhesive eggs under rocks or in crevices, and males guard the eggs until they hatch.
• Their young grow slowly and take 2–3 years to mature, which makes populations vulnerable to sudden environmental changes.
• Lifespan is surprisingly long for a small fish: individuals can live for 8–12 years, provided they survive predation and habitat disturbances.