Common name: scat
Synonyms and Other Names: spotted butterfish, common scat, argusfish, spotted scat, green scat, butterfish, Ephippus argus, Chaetodon argus (original combination)
available through www.itis.gov
Identification: The family Scatophagidae is characterized by a small, non-protractile mouth, a deep notch between the spinous and soft parts of the dorsal fin and an anal fin with IV spines. The scat can be distinguished from the following similar families as follows (summarized from Kottelat 2001):
deep dorsal notch mouth anal fin spines other
Scatophagidae present non-protractile IV
Chaetodontidae not present protractile III to V
Pomacanthidae not present protractile III prominent preopercle spine
Drepanidae present protractile III elongate pectoral fins
Scatophagus argus: The body is quadrangular and strongly compressed. The dorsal head profile is steep; snout rounded. The body is greenish-brown to silvery with many brown to red-brown spots. Spines and rays of the dorsal fin are separated by a deep notch. Small ctenoid scales cover the body. The small, horizontal mouth is not protractile. The teeth are villiform, in several rows on the jaws. Dorsal fin with XI spines and 16-18 soft rays. Spinous and soft segments of dorsal fin separated by a deep notch. The anal fin has IV spines and 14-15 soft rays. Pectoral fins with 16-17 rays. Pelvic fins with I spine and 5 soft rays. Males have a concave curvature of the head above the eye, whereas in females the head ascends at a constant slope (Barry and Fast 1992). Adults can reach approximately 30 cm TL, but occasionally larger individuals are observed (see Khan 1979). From Barry and Fast (1992), Kottelat (2001) and Allen et al. (2003).
Juveniles are greenish-brown with either a few large, rounded blotches (approximately the size of the eye) or 5-6 broad, dark vertical bars. Individuals greater than about 4 cm SL have blackish spots (typically slightly smaller than eye) loosely arranged in vertical rows. In large adults, the spots may be faded, and appear only on the dorsal part of the flanks.
It is unclear whether nominal S. argus is in fact composed of more than one species. Differences in the marking pattern (i.e., bars versus spots, size of spots) of juveniles has lead to contention over whether the species should be partitioned. The "red scat" (Scatophagus argus rubifrons) may not be a distinct variety of scat, but merely a developmental stage of the common spotted scat (Barry and Low 1992).
See Kottelat (2001) for identification details.
Size: to about 35 cm TL (Kottelat 2001) and 1.2 kg (Barry and Fast 1992)
Native Range: Nearshore waters of the Indo-Pacific, from southern India and Sri Lanka to southern Japan and Tahiti. Includes northern Australian coast, Philippines, Indonesia and the Southeast Asian coast. See Kottelat (2001) for details. Occurs in fresh, brackish and marine waters.
An individual was collected off Cedar Key, Levy County, Florida, in 1992. Another scat was captured in 3-ft of water in a mud/mangrove habitat near the St. Lucie inlet in July 2011.
Table 1. States with nonindigenous occurrences, the earliest and latest observations in each state, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Scatophagus argus are found here.
Table last updated 2/27/2023
† Populations may not be currently present.
Ecology: The species lives in coastal muddy areas including estuaries, mangroves, harbours and the lower courses of rivers (Bianchi 1985; Rainboth 1996). Scat has a broad diet and eats detritus, filamentous algae, phytoplankton, aquatic macrophytes, zooplankton, benthic invertebrates and other macrozoobenthos (Khan 1979; Datta et al. 1984; Rainboth 1996). Barry and Fast (1992) reported adult scat from the Philippines were primarily herbivorous while the juveniles preferred zooplankton. Although scat were named for their purported habit of feeding on offal (Scatophagus argus is translated from Greek to "spotted feces-eater") it may be a misnomer as this behaviour has not been confirmed in diet studies (Barry and Fast 1992).
Females mature at about 7-9 months of age and 150 g, while males mature at a smaller size (Barry and Fast 1992). In the Philippines, spawning is triggered by monsoon rains that begin in June and July and bring rainfall, cooler temperatures, increased river outflows and lower salinities (Barry and Fast 1992). Eggs are about 0.7 mm in diameter and are transparent and spherical (Barry and Fast 1992). The larvae hatch about 20 hours after fertilization at a size of 1.8 mm (Chang and Hsieh 1997).
The scat has venomous spines that can inflict painful wounds that ache for several hours (Barry and Fast 1992).
Means of Introduction: Probable aquarium release. Although interest has been shown in aquaculture (Datta et al. 1984; Barry et al. 1993), the species remains of minor commercial importance. It is occasionally sold in local markets on Indo-Pacific islands and in Southeast Asia where it is caught with gill nets and traps (Bianchi 1985; Rainboth 1996; Kottleat 2001). The species is found in the Hong-Kong live-fish market (Lee and Sadovy 1998). It is a delicacy in the Philippines (Barry and Fast 1992). Juveniles are collected for the aquarium trade.
The species has been introduced in Malta (Mediterranean Sea) where it is thought to be established (Zammit and Schembri 2011). The Maltese population is thought to have arrived via aquarium releases, although the fish now appears occasionally in the fishery. Interestingly, the spotted scat had been deemed a low risk for introduction and establishment in Malta, as its habitat requirements were considered a poor match for the area (Zammit and Schembri 2011). The surprising establishment of this species in Malta indicates it may be more flexible with regard to habitat requirements than originally considered.
Status: Reported in Florida.
Impact of Introduction: The impacts of this species are currently unknown, as no studies have been done to determine how it has affected ecosystems in the invaded range. The absence of data does not equate to lack of effects. It does, however, mean that research is required to evaluate effects before conclusions can be made.
References: (click for full references)
Barry, T. P. and A. W. Fast. 1992. Biology of the spotted scat (Scatophagus argus
) in the Philippines. Asian Fisheries Science 5: 163-179.
Barry, T. P., M. T. Castanos, M. Paz Soccoro, C. Macahilig and A. W. Fast. 1993. Spawning induction in female spotted scat (Scatophagus argus). Journal of Aquaculture in the Tropics 8: 121-129.
Bianchi, G. 1985. FAO species identification sheets for fishery purposes. Field guide to the commercial marine and brackish-water species of Pakistan. FAO, Rome.
Chang, Su-Lean and Chieh-Shih Hsieh. 1997. Studies on the early development and larval rearing of the spotted scat Scatophagus argus. Journal of Taiwan Fisheries Research 5: 41-49.
Datta, N. C., B. K. Bandyopadhyay and S. S. Barman. 1984. On the food of an euryhaline perch Scatophagus argus (Cuv. and Val.) and the scope of its culture in fresh water. International Journal of the Academy of Ichthyology, Modinagar 5: 121-124.
Khan, M. Z. 1979. A note on the occurrence of a large sized spotted butterfish Scatophagus argus (Linnaeus) at Rajpara (Gujarat). Journal of the Marine Biological Association of India 21: 193-194.
Kottelat, M. 2001. Scatophagidae. Scats. pp 3623-3626 In: Carpenter, K. E. and V. Niem (Eds.) FAO species identification guide for fishery purposes. The living marine resources of the Western Central Pacific. Vo. 6. Bony fishes part 4 (Labridae to Latimeriidae), estuarine crocodiles. FAO, Rome.
Lee, C. and Y. Sandovy. 1998. A taste for live fish: Hong Kong's live reef fish market. Naga 21: 38-42.
Rainboth, W.J., 1996. Fishes of the Cambodian Mekong. FAO Species Identification Field Guide for Fishery Purposes. FAO, Rome, 265 p.
Zammit, E. and P.J. Schembri. 2011. An overloked and unexpected introduction? Occurrence of the spotted scat Scatophagus argus (Linnaeus, 1766) (Osteichthyes: Scatophagidae) in the Maltese Islands. Aquatic Invasions 6 (Sup 1): S79-S83.
Revision Date: 4/30/2018
Peer Review Date: 11/25/2011
Schofield, P.J., 2023, Scatophagus argus (Linnaeus, 1766): U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, https://nas.er.usgs.gov/queries/FactSheet.aspx?SpeciesID=945, Revision Date: 4/30/2018, Peer Review Date: 11/25/2011, Access Date: 3/31/2023
This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.