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I need data regarding the aspect ratio for caudal fins of different Elasmobranchii. It should be some easily retrievable information but apparently fishbase doesn't have this type of data for many species.
Do you know any other database maybe that is specific for morphometric measurements?

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update: the answer below describes a database for freshwater ray-finned fish (Actineropygii), which does not cover the taxa you want (elasmobranchs are a subclass of the cartilaginous fishes, Chondrichthyes, which is a separate taxon). I'm going to leave the answer up anyway in hopes that it's useful/interesting to someone.

(Searching for elasmobranch morphometric database finds a description of the MEDLEM database (Mediterranean elasmobranchs, Mancusi et al 2020) which (1) doesn't seem to be publicly available and (2) probably has only overall length measurements, not the details you need ...)

Brosse et al. 2021 report on a global fish morphology database. I think you can almost but not quite get aspect ratios of caudal fins from this database. Specifically, they state that they have taken all of the measurements listed in figure 1a:

picture of fish, key of available morphological measures

I'm not sure exactly how you define aspect ratio of the caudal fin, but I'm assuming that it would be something like (tail length/tail depth), or based on the measurements here, ((max body length - body length)/caudal fin depth) = (MBl - Bl)/CFd. However, the authors don't make the raw morphometric measurements available, only derived values that are listed in their figure 1b, which include MBl (in centimeters), "body elongation" = Bl/Bd, and "caudal peduncle throttling" (CFd/CPd).

If you had the raw morphometric values you would almost have what you needed (I'm a little surprised they're not included in the database along with the derived measures), but you'd have one more big problem. To get caudal fin length you would need max body length measured in pixels rather than cm (MBl is taken from Fishbase; the rest of the measurements are taken in pixels, since they're derived from analysis of images with unknown scales). If the authors measured max body length in pixels when they did their image analysis, you could derive what you need from that ...

One could contact the database maintainer / contact (their e-mail is in the README file from the database, which you can get from the link below) and ask for help.

Data availability statement

FISHMORPH is publicly available through figshare (https://doi.org/10.6084/m9.figshare.14891412). We kindly ask users to cite the present paper in any published material produced using these data. Users are free to use the FISHMORPH data and to contact the au- thors for details or collaborations. We also encourage any potential data contributor to contact S.B. with potential datasets to expand the database


Brosse, Sébastien, Nicolas Charpin, Guohuan Su, Aurèle Toussaint, Guido A. Herrera-R, Pablo A. Tedesco, and Sébastien Villéger. “FISHMORPH: A Global Database on Morphological Traits of Freshwater Fishes.” Global Ecology and Biogeography 30, no. 12 (2021): 2330–36. https://doi.org/10.1111/geb.13395.

Mancusi, Cecilia, Romano Baino, Caterina Fortuna, Luis Gil De Sola, Gabriel Morey, Mohamed Nejmeddine Bradai, Argyrios Kallianotis, et al. “MEDLEM Database, a Data Collection on Large Elasmobranchs in the Mediterranean and Black Seas.” Mediterranean Marine Science, April 28, 2020. https://doi.org/10.12681/mms.21148.

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  • $\begingroup$ Thanks for the answer, it's very detailed. Aspect ratio is the ratio between the maximum width of the fin to the power of 2 ($Cfd^2$ in this case) and the actual surface area of the fin. From data you described I don't think it's possible to obtain this metric. Thanks though, its definitely useful in other cases. $\endgroup$
    – Mirko
    Mar 6, 2022 at 7:23

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