The Japanese Goby is similar to Krefft’s Goby

February 8, 2018 | Posted in: Bony fishes, Invasive species

I have been helping Catherine McMahon from Port River Shellfish Restoration Project to monitor oysters being kept in baskets in the Port River system. One interesting aspect of the monitoring is the marine life that turns up in the oyster baskets. We have found fish, shells, pygmy squid, nudibranchs, flatworms, shrimps, blue-ringed octopus, etc..

I have been pleased to find a Krefft’s Frillgoby in a basket a couple of times. This stems from the first time that I had heard of them. I had come across another species of fish that was suggested as possibly being a Krefft’s Frillgoby at the time. It turned out to be a Congolli.

Certainly, I have written about this several times, including the articles at:

I found another specimen of Krefft’s Frillgoby in an oyster basket recently. I had the identification of it confirmed via iNaturalist. That, in itself, wasn’t overly exciting, but I did get a bit excited when I discovered that the Krefft’s Frillgoby is very similar to an invasive species of Japanese fish that may be introduced into our waters by overseas ships. My two recent Krefft’s Frillgoby discoveries were both at a shipping wharf at Outer Harbor.

Glancing through a couple of old “Introduced Marine Pest Guides” I came across references to the Japanese Goby, Tridentiger trigonocephalus. The fish was listed in both a collection of Marine Pest Identification Cards issued by the NSW Department of Primary Industries, and “A Guide to the Introduced Marine Species in Australian Waters” published by the Centre for Research on Introduced Marine Pests (CRIMP).

It turned out that the Japanese Goby was the first card in the Marine Pest Identification Cards folder. The front of the card featured two very contrasting photos of a Japanese Goby. This first photo looks nothing whatsoever like a Krefft’s Frillgoby: –

This second photo, however, does resemble a Krefft’s Frillgoby a little: –

These four Australian native fish species similar to the Japanese Goby are featured on the back of the card: –


The second fish shown is a Krefft’s Frillgoby.

The CRIMP Guide to the Introduced Marine Species in Australian Waters shows these two photos of a Japanese Goby: –

This time, the second photo looks nothing whatsoever like a Krefft’s Frillgoby. The first photo, however, does resemble a Krefft’s Frillgoby a little. For comparison, here are some of my recent photos of the ‘Krefft’s Frillgoby’ found at Outer Harbor: –

The Japanese Goby is said to compete with native Australian species. We need to be on our guard and keep any eye out for them.

I sent an email message to Marine Pest Sectoral Committee – Secretariat saying, “We believe that we have been finding specimens of Godiva quadricolor in the Port River at Garden Island. A photo of the most recent sighting is attached.

We have also been finding what we believe to be Bathygobius krefftii in the Port River at Outer Harbor. But these specimens could possibly be the similar Tridentiger trigonocephalus. Photos are attached for your perusal. Regards, Steve Reynolds”

I soon received a response saying, “Hi Steve, thank you for taking the time to report these potential marine pests. We have forwarded the information to the Department of Primary Industries and Regions South Australia, who will conduct an investigation into these reports and may contact you for further details.

 Please send through any further reports of suspected to marine pests to this email or within South Australia via phone to the Fishwatch hotline on 1800 065 522.  Kind regards, Cian “

(Cian Foster-Thorpe, Aquatic Pest and Health Policy, Department of Agriculture and Water Resources, GPO Box 858, Canberra ACT 2601)

Steve Reynolds is the current President of MLSSA and is a long-standing member of the Society. Steve is a keen diver, underwater explorer, photographer and is chief author of the Society's extensive back catalogue of newsletters and journals.


  1. Paulette Gaeta
    September 14, 2018

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    Hi Steve, just wondering, how did you know who to contact to report it?

    • Steve Reynolds
      October 4, 2018

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      I reported it to the Federal agency who said that they passed it on to the State agency (I think), but I never heard any more about it at all.

  2. Steve Reynolds
    October 4, 2018

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    8 months have passed without any word from PIRSA. Experts are saying that a recent sighting of mine is a Japanese Goby – see

  3. Peter
    November 12, 2018

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    Hi I live on the upper reaches of the port river and whilst filming a new fishing invention of mine I have captured some amazing colourful black gobies & including the Japanese Goby as indicated by your picture above. Thought you might be interested. The black gobies are a real pest for recreational fisherman, as they grab bait and take it straight under a rock.

    • Steve Reynolds
      November 13, 2018

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      Thanks for these details, Peter. We are certainly interested in seeing any photos or film footage of your gobies.

  4. Steve Reynolds
    December 2, 2018

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    Peter sent us an email reply on 2nd December 2018, saying “Please see the link below to the gobies you may need to skip to 2.40 to start seeing the gobies. The Goby in question appears at 8.23 in the rock cave on the right.” See . The video shows juvenile bream, oyster blennies and Krefft’s or Japanese gobies. (Peter has a new patent pending invention/online business -see .) We are still finding gobies in Port River oyster baskets, but we haven’t been able to take the time to check them out at all.

  1. The Observed Behaviour of a Mating Pair of Krefft’s Frillgoby in an Aquarium | Marine Life Society of South Australia Inc. - […] […]

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