Sixgill sightings: database?

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SashimiFencer
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Sixgill sightings: database?

Post by SashimiFencer » Mon Aug 20, 2018 6:47 pm

Hello,

Just wondering if anyone has tried to understand the behavior of these elusive creatures. I know the Seattle Aquarium published a paper based on their research a few years back on their biting/tear behavior using bait station data. What I would like to know is if there is a pattern to the sightings by local divers based on :

-time of year (I think there's general agreement that summer/early fall is best for sightings in the Puget Sound), but has that shifted earlier or later in recent years?
-dive location
-depth
-currents
-flood vs ebb
-time of day
-any association to global climate? El nino years vs La Nina, etc.

any other relevant factors? Any thoughts?


For those interested in reading the paper, it's available online at:
PLoS One. 2016 May 31;11(5):e0156730. doi: 10.1371/journal.pone.0156730. eCollection 2016.
Feeding Behavior of Subadult Sixgill Sharks (Hexanchus griseus) at a Bait Station.

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BillZ
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Re: Sixgill sightings: database?

Post by BillZ » Mon Aug 20, 2018 8:45 pm

Scott Lundy was keeping a database a few years back but he finished his medical degree and moved to Cleveland. He now works 80+ hours a week so I'm not sure if he still monitors it.

https://catalyst.uw.edu/webq/survey/slu ... 6c642f250b

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Jeff Pack
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Re: Sixgill sightings: database?

Post by Jeff Pack » Tue Aug 21, 2018 7:14 am

Jeff and I have seen 6, all in hood canal, all depths from 160-230, all late day
=============================================

- I got a good squirt in my mouth
- I would imagine that there would be a large amount of involuntary gagging
- I don't know about you but I'm not into swallowing it

CCR discussion on Caustic Cocktails.

SashimiFencer
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Re: Sixgill sightings: database?

Post by SashimiFencer » Tue Sep 25, 2018 10:50 am

howdy,
I emailed Scott Lundy and he's no longer maintaining his Six Gill Database. (understandable since he's a busy surgical resident.) I'm still interested in trying to understand their behavior, so I'd like to start a database myself.

First, is there anyone with programming experience on this site who can help me? I'd like to build a site/app that makes it easy to enter using smartphones (or computer).

Second, does anyone know the researchers at the Seattle Aquarium? I might ask for some pointers for behaviors to monitor.

thanks!

Rockfish
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Re: Sixgill sightings: database?

Post by Rockfish » Tue Sep 25, 2018 12:47 pm

I was part of a project at the Seattle Aquarium about 10 years ago as a volunteer diver where we set up a bait station and would tag sharks and take biopsy samples.
They have been maintaining a database of sightings.
When last I talked with Jeff Christiansen (SA DSO and biologist) he said that the latest version of their website had removed the Six Gill Shark sightings report form and he was working with their webpage team to get it added back.
I would start with Jeff and go from there no sense in duplicating what they are or have already done unless you want to have a separate list.

Mike

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ljjames
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Re: Sixgill sightings: database?

Post by ljjames » Tue Sep 25, 2018 2:50 pm

+1

Rockfish wrote:I was part of a project at the Seattle Aquarium about 10 years ago as a volunteer diver where we set up a bait station and would tag sharks and take biopsy samples.
They have been maintaining a database of sightings.
When last I talked with Jeff Christiansen (SA DSO and biologist) he said that the latest version of their website had removed the Six Gill Shark sightings report form and he was working with their webpage team to get it added back.
I would start with Jeff and go from there no sense in duplicating what they are or have already done unless you want to have a separate list.

Mike
----
"I survived the Brittandrea Dorikulla, where's my T-shirt!"

SashimiFencer
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Re: Sixgill sightings: database?

Post by SashimiFencer » Tue Sep 25, 2018 6:52 pm

Will email Jeff C at the Aquarium to ask if they have analyzed their data already and if it can be shared with recreational divers to increase our likelihood of a Six gill sighting.

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Cmjstealth
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Re: Sixgill sightings: database?

Post by Cmjstealth » Fri Oct 26, 2018 6:49 pm

I like playing with this kind of data too and would be happy to help with related database prep, analytics, and/or input form development (if required: I agree with trying to not reproduce the wheel). I suspect there are already several sighting databases we could leverage.

I checked the reef.org dataset and I suspect getting a useful sized sample of data is going to be the biggest challenge. There are currently 17,903 WA reef.org surveys but sixgills were reported on only 21 dives - that's a sighting frequency less than 1/8th of 1%. Regardless we could try reaching out to those surveyors to get specifics not captured by the standard survey form. In addition I know several non-reef surveyors who have sighted them this summer. Can also ask the local dive clubs. Perhaps useful if combined with Scott's db and/or the historical aquarium dataset.

The latest raw dataset I have on hand from reef.org was pulled in July and had 17 sightings by that point. This isn't much although there may already be some noticeable trends like seasonality that have statistical significance (if I were to do the calculation). There appears a cluster of sightings around the June-Nov timeframe for example:

Image

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Cmjstealth
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Re: Sixgill sightings: database?

Post by Cmjstealth » Sat Oct 27, 2018 1:21 am

Update: More info if interested...
I played with the reef.org data some more and warm water temperatures (especially 54F+) and depth (>80ft) both correlate strongly with sixgill sighting frequencies. Perhaps the seasonality seen in the graph above might simply be a reflection of this pattern: they come shallower in response to the warm summer waters for some reason. Abnormal "heat event" years with warmer than average water temperatures also correlate though and I'm not sure yet if this is reflecting the same thing (I'm using both reef.org and NOAA water temp data). I wonder if there could be an indirect relationship with temperature like food availability or O2 (I haven't explored further).

Regardless of temperature, depth appears to have the strongest correlation with SF%. That SF% bump in March, for example, is the result of a rather deep cove 2 survey dive. One disclaimer is that this reef.org data doesn't indicate what depth the surveyor actually sees the sixgill- just the max depth of that dive. This could skew SF values slightly but I suspect it is still directionaly accurate:

Image

Again - all this is based on a vary small sample of sightings and I haven't calculated error margins for any of the groups so they may not all be statistically significant differences. That said, the nice thing about reef.org data is that it also effectively includes how many dives did NOT see sixgills. This is really important since data that only tracks sightings often only reflects the fact that an unusual amount of dives occurred at a particular location/time/depth/etc.

It doesn't look like the reef.org sample sizes will be large enough to draw conclusions regarding abundance by locations. Perhaps this is motivation for us to do more reef surveys at some other key sites? Also don't see any obvious patterns by time of day: like location this could mean there is no pattern or just that it is small and there isn't enough data to see. Diver reported current (none/slight/strong) also doesn't show much difference. I haven't added any NOAA tide or current station data yet to my data model but someday plan to do so for a unrelated project related to visibility prediction.

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BillZ
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Re: Sixgill sightings: database?

Post by BillZ » Sat Oct 27, 2018 10:29 am

Cmjstealth wrote:Update: More info if interested...
I played with the reef.org data some more and warm water temperatures (especially 54F+) and depth (>80ft) both correlate strongly with sixgill sighting frequencies. Perhaps the seasonality seen in the graph above might simply be a reflection of this pattern: they come shallower in response to the warm summer waters for some reason.>>>>>>>>>


My theory (with no real data to really back it up) is that the 6 Gills come up in July-August-September because the Salmon run during those months. Redondo, where most of the recent sightings have taken place, has an active fishing pier and the fishermen clean their catch and dump fish guts in the water, drawing the sharks in shallow.

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