Redfin bully

Description

The Redfin bully (Gobiomorphus huttoni) is a small, freshwater fish endemic to New Zealand. It is characterized by its robust body, large head, and distinctive red-orange fin margins, particularly prominent in breeding males. This species is an amphidromous goby, meaning it migrates between freshwater and marine environments during its life cycle, with larvae developing at sea before returning to freshwater as juveniles.

Physical Characteristics

Body shape

elongated

Coloration

Body coloration is highly variable, ranging from olive-green to dark brown, often mottled or blotched to provide camouflage against stream beds. The most distinctive feature is the bright red-orange to orange-yellow margins on the dorsal, caudal, and anal fins, particularly vibrant in breeding males. Females and non-breeding males have duller fin coloration. A dark spot is often present at the base of the pectoral fin.

Scale type

ctenoid

Mouth position

terminal

Distinctive features

Bright red-orange to orange-yellow fin margins (especially in males), Two distinct dorsal fins, Large, broad head, Robust, cylindrical body, Dark spot at the base of the pectoral fin

Dorsal fin

Two dorsal fins; the first dorsal fin is spiny, and the second is soft-rayed. The fin margins, especially of the second dorsal, are often red-orange.

Tail fin

Caudal fin is rounded to slightly emarginate, with red-orange margins.

Pectoral fin

Large and fan-like, often with a dark spot at the base. Used for maintaining position in currents.

Distinctive fins

Anal fin also exhibits red-orange margins, particularly in breeding males. Pelvic fins are fused to form a disc-like sucker, characteristic of gobies, used for adhesion to substrates.

Identification Tips

Habitat

Water type

freshwater

Depth

Typically found in shallow waters, from a few centimeters to a meter or more, often in riffles and runs.

Environment

Primarily found in clear, cool, well-oxygenated freshwater streams and rivers, particularly those with stony or gravelly bottoms. They prefer areas with moderate to fast currents and abundant cover provided by rocks, logs, and aquatic vegetation. They are also found in the lower reaches of rivers and estuaries during their migratory phases.

Geographic range

Endemic to New Zealand, found throughout both the North and South Islands, as well as Stewart Island. They are one of the most widespread native freshwater fish species in the country.

Aquarium Information

• Care level: intermediate
• Temperament: territorial
• Diet: carnivore
• Minimum tank size: 75 liters (20 gallons) for a single specimen, larger for groups or breeding pairs.
• Temperature: 10-22°C (50-72°F)
• pH level: 6.5-7.5
• Hardness: Soft to moderately hard (5-15 dGH)
• Compatibility: Best kept in a species-specific tank or with other robust, similarly sized native New Zealand fish that can tolerate cooler, flowing water conditions. Avoid very small or delicate fish due to potential territorial aggression.
• Special requirements: Requires excellent water quality, strong aeration, and a well-filtered tank. Provide plenty of hiding places using rocks, driftwood, and dense planting. A substrate of gravel and sand is preferred. Mimicking a stream environment with good flow is beneficial. Breeding requires specific conditions, including a suitable spawning site (e.g., flat rock) and potentially a period of cooler temperatures.

Wild Information

• Conservation status: least concern
• Seasonality: Breeding typically occurs from late winter to early summer (August to January in New Zealand), with peak activity in spring. Juveniles migrate upstream from estuaries during spring and summer.
• Market price: Not commercially fished or sold for consumption. Occasionally available in the aquarium trade, with prices varying.
• Commercial importance: none
• Taste: Not typically consumed.
• Texture: Not typically consumed.
• Nutritional value: Not typically consumed.

Key Facts

Similar Species

Scientific Classification

Kingdom

Animalia

Phylum

Chordata

Class

Actinopterygii

Order

Gobiiformes

Family

Gobiidae

Genus

Gobiomorphus

Species

huttoni

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