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Questions on Rhinogobius

Home Forums Fresh and Brackish Water Fishes Questions on Rhinogobius

This topic contains 0 replies, has 1 voice, and was last updated by  mikev 5 years, 4 months ago.

Viewing 15 posts - 1 through 15 (of 122 total)
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  • #302483

    Matt
    Keymaster

    Finally getting around to adding some profiles for this genus, and decided that it might be best to begin with fish we can identify positively, then take it from there.

    So, I think these should be R. candidianus, but would appreciate confirmation. :)

    Rhinogobius-candidanus-maybe.jpgRhinogobius-candidianus-2.jpg

    #349403

    Ferrika
    Participant

    Could be R. candidianus or R. nantaiensis, Matt. That depends on the size. R. candidianus be about 10 cm , R. nantaiensis only 5.5 cm. Otherwise, there are no differences in the animals externally.

    With the animal on the 2nd picture I tend to R. nantaiensis because of the short snout.

    #349407

    Matt
    Keymaster

    Hi Jutta, do agree there seem to be two different fish in those photos but R. candidianus and R. nantaiensis should not look the same according to the key in Chen and Shao (1996)?

    • R. candidianus: cheek without spots in females and most males; lateral body usually uniformly dark brown; longitudinal scale rows 34-38 (35-37); scales between origin of 1st dorsal and pectoral fins 11-15 (12-13)

    • R. nantaiensis: cheek with significant spots in both sexes; midline of flank with a row of dark blotches; inner part of caudal-fin blue in adult male; longitudinal scale rows 33-36 (34-35); scales between origin of 1st dorsal and pectoral fins 10-12 (11).

    So. R. candidianus should be a deeper-bodied fish without spots on the cheek. Here are photos of wild-collected males from Taiwan, labelled R. candidianus and R. nantaiensis, respectively, and I think they show these differences quite well:

    Rhinogobius-candidianus-male-1.jpgRhinogobius-nantaiensis-male-1.jpg

     
    #349408

    Matt
    Keymaster

    Guess we need a copy of Aonuma, Y. and I-S. Chen. 1996.Two new species of Rhinogobius (Pisces, Gobiidae) from Taiwan. Journal of Taiwan Museum v. 49 (no. 1): 7-13.

    Can anyone help?

    #349410

    Ferrika
    Participant

    Hi Matt,

    it may be that we the second kind on the Photo have not named properly and this is not R. nantaiensis. But this kind looks the R. candidianus confusingly similar to, only that it remains smaller.

    #349425

    Matt
    Keymaster

    Hi Jutta, it might be, sure, but it does match the description quite closely and I think the spots on the cheeks (area in front of opercle) can be used to tell them apart?

    How were the fish in the hobby originally identified as R. nantaiensis?

    #349424

    Ferrika
    Participant

    @matt said:
    Hi Jutta, it might be, sure, but it does match the description quite closely and I think the spots on the cheeks (area in front of opercle) can be used to tell them apart?

    How were the fish in the hobby originally identified as R. nantaiensis?

    I don’t remember, Matt. May be, it was by me.

    However, the kind of the large animals sometimes have these red spots. However, it may also be that the two species have been crossed, as these are in the trade unfortunately never be differed.

    #349439

    Matt
    Keymaster

    Yep, according to Chen and Shao some male R. candidianus can have the spots.

    Do the smaller fish ever show dark markings along the middle of the flanks?

    #349440

    Ferrika
    Participant

    @matt said:

    Do the smaller fish ever show dark markings along the middle of the flanks?

    No, only sometimes. They change their colors like a chamäleon :-)

    #349441

    Matt
    Keymaster

    So sometimes the smaller ones do have dark marks on the sides?

    And the larger ones?

    #349443

    Ferrika
    Participant

    Both, Matt. As I wrote, they differ only in size.

     

    Perhaps will help you some Pics? Take a look at this: http://30.ferraqua.de/index.php/Rhinogobius-nantaiensis and this http://30.ferraqua.de/index.php/Rhinogobius-candidianus

    #349447

    Matt
    Keymaster

    Thanks Jutta, I’ve been looking at the pics and comparing them with the key.

    Another question if you don’t mind. Are either of the two fish more common in the trade, or both equally available?

    #349448

    Ferrika
    Participant

    This can be not so easy to answer, Matt. Nearly always, the animals are offered as Rhinogobius candidianus. Upon closer inspection, they are in 80% of cases Rhinogobius nantaiensis.
    Often they will even be delivered mixed.

    #349451

    Matt
    Keymaster

    That’s interesting, because the distribution of R. nantaiensis in the wild is much smaller than that of R. candidianus.

    Here’s the map from the review. R. candidianus was collected at localities 1-10, and R. nantaiensis only at 12 and 13.

    The pics I posted above are of fish collected at confirmed localities, so am wondering if we’re looking at something else here…

    Rhino-map-1.JPG

    #349455

    mikev
    Participant

    Jutta,

    how breedable are R. candidianus?

    (I’m tempted and they may be available with some effort…. actually,–sorry for the offtopic– since rhinogobius seem hard to find lately, so I’ve been substituting etheostomas… I’ll show later.)

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