10.06.18 North Monastery Urchin Sizing

Holds posts for RCCA Certified Divers from 2018

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Central Coast Regional Manager
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10.06.18 North Monastery Urchin Sizing

Postby dabbott » Fri Aug 24, 2018 4:32 pm

In an effort to get more urchin size data I've scheduled a couple of days for folks to go out and just get size data from sites that we didn't get it from when we surveyed it the first time. Collecting urchins size data is fairly straightforward so I have not scheduled anyone to act as Data Captain for these surveys. You and your buddy(s) will be on your own to dive the site and collect this info. Feel free to bring a non-reefcheck diver as a buddy but we want only RCCA certified divers to collect this data so that we can be sure everyone is doing it correctly.

Urchin sizing objective
The goal with urchin sizing is to get an accurate picture of the frequency of the different size classes of urchins. This data is important because it can tell us the rough age of the urchins and if the numerous urchins at a site recruited a long time ago in one major event or if they represent recent reproduction which has implications for what is occurring inside of urchin barrens.

All you will need is urchins calipers and datasheets (and you can get by without datasheets by writing on the back of a sheet or even just directly on your databoard). Both calipers and datasheets are in the locker at Bamboo Reef. The combo is 2995. If you plan on doing a few of these feel free to hang onto the calipers. After the survey photograph the datasheet and email it to me.

Urchin sizing technique
The key is to measure an unbiased sample of urchins as opposed to just the small ones or just the large ones. The best way to do this is to select an area and measure all the urchins in that area, then move on to the next area. The measurement we want is the diameter of the test. Wiggle the arms of the calipers through the spines until it presses up against the test. Then look at the centimeter scale at the bottom of the caliper, and count the number of visible cm marks and that is the size you record. Make sure you are using the centimeter scale not inches!. Ideally, we get AT LEAST 100 purple urchins and 100 red urchins, but if reds are not abundant just getting purples is fine.

You can go here to see what the calipers look like:
https://www.forestry-suppliers.com/prod ... mnum=59768

Where: North Monastery. Note: this site has a rough beach entry and I would not recommend this dive if you are not familiar with it.
Here is a description of the dive site:

http://www.montereyscubaboard.com/monte ... ery-beach/

When: Saturday, October 6th at 8:00 am (unless you decide on going on a different day and/or at a different time).

Thanks in advance for helping to collect this data!

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Re: 10.06.18 North Monastery Urchin Sizing

Postby jesseb » Sat Sep 29, 2018 2:56 pm

I will go out on 10/7 :)

Kristofer Vogelsong
Posts: 10
Joined: Thu May 31, 2018 1:29 pm

Re: 10.06.18 North Monastery Urchin Sizing

Postby Kristofer Vogelsong » Sun Sep 30, 2018 9:08 pm

Dan, I can do this if I don't make it on to the Point Joe boat.
Thanks, Kris V.

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