Descended fish mortality rates

https://www.pcouncil.org/documents/2022/11/h-4-a-supplemental-gmt-report-3.pdf/?fbclid=IwAR3gkDusJsY1enhduEPtSoRWRhyhU-cn0QD2VdfwtDuinW_HMTtrmh9c5tg_aem_AcMhdsM3p6Arb63fetovUGmIs9yycLNIvUn5siHEyf7XMeFHKvn5GDyCL71KmP4gsTc&mibextid=Zxz2cZ

So if I read the charts right there is about a 3% to 10% mortality rate on fish descended when caught up to 30 fathoms deep. Whereas there is about 10% to 60% mortality on fish released on the surface.

Nice to see data on this.
Thanks for sharing.

So if I read the charts right there is about a 3% to 10% mortality rate on fish descended when caught up to 30 fathoms deep. Whereas there is about 10% to 60% mortality on fish released on the surface.

I don't think it's quite that good for the descended fish. From Table 1, when using a descending device, it is 3% for canaries and 16% for blacks at 30 fm, and according to Table 2, for olives and yellowtail (which are in the strangely-named "pelagic guild"), it's 34% at that same depth.

I find a lot of this confusing. For example, they claim that if you use a descending device, then canary RF have better survival rates than black RF down to 50 fathoms, but from 50-100 fathoms, blacks do way better. That seems a bit implausible. And, I'm wondering how they decide that a fish survived after it was descended. Do they just assume it survived if it doesn't float back up to the surface within a few minutes? If so, that seems like it would be error prone as, for example, a fish might "survive" for a few minutes, but die shortly thereafter.

So if I read the charts right there is about a 3% to 10% mortality rate on fish descended when caught up to 30 fathoms deep. Whereas there is about 10% to 60% mortality on fish released on the surface.

I don't think it's quite that good for the descended fish. From Table 1, when using a descending device, it is 3% for canaries and 16% for blacks at 30 fm, and according to Table 2, for olives and yellowtail (which are in the strangely-named "pelagic guild"), it's 34% at that same depth.

I find a lot of this confusing. For example, they claim that if you use a descending device, then canary RF have better survival rates than black RF down to 50 fathoms, but from 50-100 fathoms, blacks do way better. That seems a bit implausible. And, I'm wondering how they decide that a fish survived after it was descended. Do they just assume it survived if it doesn't float back up to the surface within a few minutes? If so, that seems like it would be error prone as, for example, a fish might "survive" for a few minutes, but die shortly thereafter.

great questions, I have a very nice, very $$$ descender, it is important to me.  But i've always wondered....does a Ling just gobble them up?  they're targets for the whole ride down...and possibly a bit dazed and confused when they get back down.

I have a very nice, very $$$ descender, it is important to me.  But i've always wondered....does a Ling just gobble them up?  they're targets for the whole ride down...and possibly a bit dazed and confused when they get back down.

Which one? I bought a nice ($$$) one without looking at the details, and then got around to reading the instructions and found the shallowest depth setting is 100', and I'm almost always fishing more shallow than that, so I went back to the bounce ball.

I'm not going to lay down money for a new one until I see an open nearshore season though. I won't be surprised if nearshore rockfish goes the way of the abalone.

I think the inexpensive Shelton Descender is possibly the best.
You only need to descend to 60' regardless of depth caught.
The slower you bring the fish up and the quicker you put it back down, the better.

What I get out of the data (and I don't know how they measure mortality - Oregon has video of fish recompressing and swimming off) is that in my depth range (5-25 fathoms) survivability is very good for descended fish. Deeper than 50 fathoms (the deepwater depth that they opened to fishing) mortality is almost a given, and I have heard that lots of Yellow Eye are getting caught. So on those trips they should just say that you keep everything you catch and stop at your limit. It would lead to fewer fish killed.

And open up the nearshore to non-motorized with descenders rigged and ready.

Hi Joe

Thank you for sharing great information.
I wish they did a better job presenting the information. 
I have been using Shelton Descender for many years and am very happy with it.  Simple to use and easy to carry.

Paul

I use a Shelton descender. It's rigged with a 32 oz cannonball. If it weren't for that descender, I guarantee that I'd be killing 100% of the yelloweye I pull up from 100 ft. They float on the surface and refuse to attempt to swim down. YEs are notorious for "blowing up" from any depth, and I can only rarely get one to swim down on its own.

The biggest issue is ensuring you bring enough lead with you to descend larger fish. The 32 oz cannonball isn't enough for the bigger YEs. I'll start tacking on additional lead balls until I can get the fish to sink. Sometimes, that takes up to 5 pounds of lead. Be sure you have enough lead for those fish, otherwise your descender can be worthless.

On my buddies boat we would just bring the downrigger with one of those pressure release clips attached to the ball. This worked out great since using a dedicated rod to descend was a real hassle and people didnt particularly like doing that. With the downrigger we could keep fishing and let the fish acclimate at 50' before dropping it down to 60' where the devise would release. I think it has a 60 and a 90 setting but I can't remember. One day we couldn't get out of the yelloweye and had to descend 10+ of them. I remember only 2 floated back up but we tried our best to get them on that clip again. bird and seal food .

I always have the safety pin in my kayak but have not needed to use it yet at the depths I fish. I have used just my teaser hook on the chin skin of some fish to give them some help and then yank them off at depth which works in a pinch. Chinas sometimes have a hard time getting there fat heads to sink lol.