it collected from seagrass bed of Seribu Island (Kepulauan Seribu) Indonesia
Could this interactive key to Siganidae help? http://www.fishbase.se/keys/questions.php
Hi Adinda,
Juvenile Siganus spp. are difficult to ID with pictures that do not show the full detail of their fin structures. The specimen seems to be in a poor condition and both the dorsal and anal fins are not clearly presented to be able to accurately count the spines and soft rays. It would also be very useful to see a fully displayed tail fin to determine the degree of forking. For example, S. argenteus looks very similar to both S. canaliculatus and S. fuscescens but its tail fin is more deeply forked compared to the other two species. Based on your picture we cannot see if that is the case. If you still have the specimen you may try to take more pictures and post them again. The juvenile you are showing is probably either S. canaliculatus or S. fuscescens. S. canaliculatus has a slightly more pointed snout and longer pectoral fins than S. fuscescens. Since the number of spines and soft rays on dorsal and anal fins in these two species are same it will be difficult to ID which one it is. I hope someone who has practical experience with these species will be able to identify it for you. In the future, try to arrange the specimen like you see in this picture from ReefBase before you take a photo.
http://www.fishbase.se/photos/PicturesSummary.php?StartRow=3&ID=4456&what=species&TotRec=13
Mount the specimen on a dissecting tray and use pins to pin and spread all the fins. Once done you can drop a few drops of fixative (e.g., 10% formalin solution) on the fins to keep them in place and then take the pins out before taking pictures. Also when you are taking the photo use a higher f-stop, like f16- f18 or higher, to get as much depth of field as possible so that the spines and rays are in clear focus. If you have problems with light try increasing the ISO number. You can use a flash or side lamps to illuminate the specimen and try to use a contrasting background colour to highlight the spines and rays. I have attached a couple of papers that I hope you’ll find useful in the future.
Tomas
Dmitry Telnov & Tomas (Tom) Tomascik thank your help and explanation.
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