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Questions on Rhinogobius
November 29, 2012
9:00 am
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Matt
Málaga, Spain
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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.jpgImage Enlarger

Rhinogobius-candidianus-2.jpgImage Enlarger

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November 29, 2012
11:58 am
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Ferrika
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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.

greets Jutta
November 30, 2012
9:34 am
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Matt
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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.jpgImage Enlarger

Rhinogobius-nantaiensis-male-1.jpgImage Enlarger

 
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November 30, 2012
9:35 am
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Matt
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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?

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November 30, 2012
12:16 pm
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Ferrika
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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.

greets Jutta
December 4, 2012
8:09 am
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Matt
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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?

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December 4, 2012
10:41 am
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Ferrika
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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.

greets Jutta
December 5, 2012
11:23 am
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Matt
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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?

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December 5, 2012
11:28 am
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Ferrika
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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 :-)

greets Jutta
December 5, 2012
1:04 pm
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Matt
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So sometimes the smaller ones do have dark marks on the sides?

And the larger ones?

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December 5, 2012
4:42 pm
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Ferrika
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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.ph.....antaiensis and this http://30.ferraqua.de/index.ph.....andidianus

greets Jutta
December 6, 2012
2:07 pm
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Matt
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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?

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December 6, 2012
2:34 pm
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Ferrika
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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.

greets Jutta
December 7, 2012
9:57 am
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Matt
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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.JPGImage Enlarger

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December 7, 2012
4:52 pm
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mikev
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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.)

December 7, 2012
5:00 pm
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Ferrika
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Mike, IF they spawn times, relatively simple. It's just sometimes quite difficult to persuade them to spawn.
Although the larvae are free-swimming, but relatively large, and eat from the beginning Artemia nauplii.
The same applies also for the Rhinogobius nantaiensis. Of which I had from one clutch 150 pups :-)

Matt, the high proliferation of R. nantaiensis could be one reason why so many animals are caught. Whose populations may be in a place far greater than that of R. candidianus. The catcher collect (unfortunately) often several catches in a container before bringing them to the exporter. And I guess they do not differentiate the animals.

greets Jutta
December 10, 2012
7:35 pm
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Matt
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Thanks Jutta. Some unspecified 'thing' is still niggling me though. Do you mind if we list it as R. cf. nantaiensis for now?

Mike if you have more Etheostoma you must get some pics on!

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December 10, 2012
10:28 pm
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Ferrika
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Matt said
Do you mind if we list it as R. cf. nantaiensis for now?

 

For me that's ok, Matt. I would rather have one cf. too much, as the animals are referred constantly wrong.
Honestly, most of the identifications at Rhinogobius are only max. 70% sure.

greets Jutta
December 11, 2012
6:08 am
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mikev
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Thanks, Jutta! I think I'll try to get them...
Etheostomas: Matt, will try over the break. The guys I got are these [Image Can Not Be Found] (not my photo) (Savannah Darter == Etheostoma fricksium; with luck I'll have another species by the end of the week).

December 11, 2012
8:36 am
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Matt
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Ferrika said  

For me that's ok, Matt. I would rather have one cf. too much, as the animals are referred constantly wrong.
Honestly, most of the identifications at Rhinogobius are only max. 70% sure.

Ok great, thanks again Jutta. So, do the nantaiensis always have the spots on the cheeks?

What a superb-looking fish Mike. Cool

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