[Coral-List] Measuring damselfish on SCUBA?

[Felix Martinez - NOAA Federal]

Malin,

Small fish measuring boards work well. Just lay the fish down while in the
net. Commercially made ones tend to be on the larger side, so I ended up
making my own using pieces of a Plexiglas plate with a thin ruler glued on
top. Just cut a long/wide piece for the ruler and an end piece, then meld
together with. Here is a simple guide
<http://www.wikihow.com/Glue-Plexiglas>. I believe that acetone also works.

Another strategy is to use a pvc pipe cut in half. There are commercial
versions as well but easy to make your own. Glue a cap to one end of the
pipe then (carefully!) cut in half lengthwise. Glue the rulers and you are
ready to go. Bonus is you have two boards. The diameter of the pipe will
depend on the largest size of fish you are measuring. I have used these too.

If not measuring a lot of fish and you need precise measurements, an
alternative is to build a small long flat chamber where you can squeeze the
fish in for measurement. The width of the chamber again will depend on the
largest fish you will measure. In this case you may need to build multiple
versions to accommodate a large range of sizes. Easily built out Plexiglas
too. I built them just to take pictures (already had boards) but by adding
a ruler on one side you can use for both purposes

Felix

On Mon, Dec 5, 2016 at 11:28 PM, Malin Pinsky <malin.pinsky at gmail.com>
wrote:

> Hi all,
>
> I'm curious if anyone has a reasonably accurate technique for measuring
> damselfish fork length while on SCUBA. This would be for individual fish
> that we have caught and are holding in a net.
>
> Previously, we've been using a pair of calipers, but trying to hold the
> fish straight by hand has proven pretty imprecise (+/- a cm or so for 5-12
> cm fish).
>
> Many thanks in advance for any suggestions or ideas.
>
> Regards,
> Malin
>
> --
> Malin Pinsky
> Assistant Professor
> Department of Ecology, Evolution, and Natural Resources
> and Institute of Earth, Ocean, and Atmospheric Sciences
> 14 College Farm Rd.
> Rutgers University
> (848) 932-8242
> malin.pinsky at rutgers.edu
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> Coral-List at coral.aoml.noaa.gov
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>



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Felix A. Martinez, Ph.D.
National Oceanic and Atmospheric Administration
4840 South State Rd.; Ann Arbor, MI 48108
email: Felix.Martinez at noaa.gov
ph: 734-741-2254; fax: 734-741-2055

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