Disclaimer:

The Nonindigenous Occurrences section of the NAS species profiles has a new structure. The section is now dynamically updated from the NAS database to ensure that it contains the most current and accurate information. Occurrences are summarized in Table 1, alphabetically by state, with years of earliest and most recent observations, and the tally and names of drainages where the species was observed. The table contains hyperlinks to collections tables of specimens based on the states, years, and drainages selected. References to specimens that were not obtained through sighting reports and personal communications are found through the hyperlink in the Table 1 caption or through the individual specimens linked in the collections tables.

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Common name: zebra blenny

Synonyms and Other Names: roundhead blenny, mangrove blenny

Taxonomy: available through www.itis.gov

Identification: Omobranchus obliquus is a small blenny with no crest on the head. The body is white to pale brown with narrow oblique brown marks on side with slanting or curved white lines between (Randall 2005). There is a narrow blue line below and behind the eye with a dull red spot on the operculum (Randall 2005, Allen and Erdmann 2012). There are irregular black lines ventrally on the head that continue onto the throat (Randall 2005). This species is sexually dimorphic with males slightly larger than females. Males have bright yellow pelvic fins and chin, and an electric blue spot on the posterior half of the dorsal fin (Baumgartner 2002).

Size: 7 cm total length (Randall 2005)

Native Range: Nicobar Islands to Samoa, and New Caledonia to Mariana and Caroline Islands (Allen et al. 2003).

Alaska	Hawaii	Puerto Rico & Virgin Islands	Guam Saipan

Hydrologic Unit Codes (HUCs) Explained
Interactive maps: Point Distribution Maps

Ecology: Omobranchus obliquus live in shallow brackish and marine waters up to 2 m deep close to shore (Myers 1999, Allen et al. 2003). They are solitary or live in small groups (Allen et al. 2003). This species is found in tidepools, on muddy to sandy bottoms with eel grass and algae; and near the edge of mangrove swamps (Springer and Gomon 1975).

The female lays demersal eggs that are guarded by the male in a nest. Nest sites include the surface of stones, abandoned worm tubes, crevices in dead coral, and empty bottles and cans (Allen and Erdmann 2012).

Field observations show that this species is primarily herbivorous, predominantly consuming filamentous algae on hard surfaces while occasionally small crustaceans are eaten (Baumgartner 2002). Juveniles consume a higher percentage of crustaceans, mainly copepods, to algae (Baumgartner 2002).

 

Means of Introduction: In 1951, USFWS stocked a concrete tank on Coconut Island, Kaneohe Bay, Hawaii with pieces of coralline rock bearing Tridacna clams and other organisms from near the Samoan Islands. The concrete tank was connected to Kaneohe Bay by a submerged inlet circulating water between the tank and the bay. Four live specimens of Omobranchus obliquus were collected from the tank in 1953 but misidentified as O. elongatus (Strasburg 1956) later identified as O. obliquus (Springer and Gomon 1975).

Status: Established in Kaneohe Bay, Oahu, Hawaii (Parenti et al. 2020)

Impact of Introduction: The impact of this species is 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)

Allen, G.R., R. Steene, P. Humann, and N. Deloach. 2003. Reef fish identification: Tropical Pacific. New World Publishing Inc. Jacksonville, Florida.

Allen, G.R., and M.V. Erdmann. 2012. Reef fishes of the East Indies. Volume 2. Tropical Reef Research, Perth, Australia.

Baumgartner, E. 2002. Resource use and behavioral ecology of the mangrove blenny, Omobranchus rotundiceps obliquus (Garman 1903). Ph.D. dissertation. University of Hawai’i, Honolulu, Hawaii.

Myers, R.F. 1999. Micronesian reef fishes: A field guide for divers and aquarists. Coral Graphics, Guam.

Parenti, L.R., D.E. Pitassy, Z. Jaafar, K. Vinnikov, N.E. Redmond, and K.S. Cole. 2020. Fishes collected during the 2017 MarineGEO assessment of Kane’ohe Bay, Oahu, Hawai’i. Journal of the Marine Biological Association of the United Kingdom 100:607-637.

Randall, J.E. 2005. Reef and shore fishes of the South Pacific: New Caledonia to Tahiti and the Pitcairn Islands. University of Honolulu Press, Honolulu, Hawaii.

Springer, V.G., and M.F. Gomon. 1975. Revision of the blenniid fish genus Omobranchus with descriptions of three new species and notes on other species of the tribe Omobranchini. Smithsonian Contributions to Zoology 177:1-135.

Strasburg, D.W. 1956. Notes on the blennioid fishes of Hawaii with descriptions of two new species. Pacific Science 10:241-267.

Other Resources:

Author: M.E. Brown

Peer Review Date: 5/11/2023

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.