Spotted Scat (Scatophagus argus) Breeding Guide

Scats spawn in coastal marine waters with a pelagic larval phase and are not bred in home aquaria; aquaculture relies on induced spawning.

Overview

Scatophagus argus, the spotted scat, is a diamond-shaped Indo-Pacific fish found from the Persian Gulf to Japan and south to New South Wales, Fiji and beyond. It lives in sheltered coastal waters such as estuaries, harbours, mangrove pools and the lower parts of freshwater streams. Fry inhabit freshwater and the species moves toward saltwater as it matures. It spawns in marine conditions and is not bred in home aquaria.

Sexing

Females reach sexual maturity at about 7–9 months and roughly 150 g body weight, while males mature at smaller sizes. Reliable external sexing for pairing is otherwise poorly defined.

Spawning Behavior & Trigger

In the Philippines, spawning is brought on by the monsoon rains beginning in June and July. The eggs are about 0.7 mm in diameter, transparent and spherical, and larvae hatch in roughly 20 hours at about 1.8 mm length. Larvae then pass through a pelagic tholichthys stage similar to that of butterflyfishes.

Egg & Fry Care

The pelagic larval phase requires open marine water and specialised rearing, which is why reproduction is the domain of aquaculture rather than the home aquarium. There is no parental care to exploit, and the salinity transition from marine larvae to brackish juveniles cannot easily be staged in a tank.

Common Challenges

Marine spawning conditions, a pelagic larval stage, adult size and a shoaling habit (groups of four or more) all place reproduction beyond reach for hobbyists. Scats are kept as brackish-to-marine display fish; any production for the trade comes from induced-spawning aquaculture.