Draft Report on 2012 Striped Bass Tagging Field Season

[Marty Gingras]

Hello all,

This is a link to a complete draft report on the 2012 adult striped bass tagging field season:

http://nrm.dfg.ca.gov/FileHandler.ashx?DocumentID=48061

The report is not an analysis of the striped bass population, but a description of what we did and saw.

Information on the fish we tagged will later be used to estimate striped bass abundance, annual harvest rate, annual survival rate, etc.

Thanks

Marty Gingras
BDR-IEP Program Manager
California Department of Fish and Game
Bay Delta Region
4001 North Wilson Way
Stockton, California 95205

Phone (209) 948-3702
Phone (831) 372-2581
FAX (209) 946-6355
email mgingras@dfg.ca.gov

[Darian]

Marty,.... I'm not ignoring this. Just trying to digest it all. Thanks for posting the link.

[Fish Guru]

Marty,
What method do the biologists use for sex determination in these fish? I was of the understanding that the only accurate options are either ultrasound or cutting them open, pretty surprising that the method used was not outlined in this report. Aren't details such as this usually included in these comprehensive scientific reports?

[Marty Gingras]

Marty,
What method do the biologists use for sex determination in these fish? I was of the understanding that the only accurate options are either ultrasound or cutting them open, pretty surprising that the method used was not outlined in this report. Aren't details such as this usually included in these comprehensive scientific reports?

Where and when we catch these fish, and how we catch them, means that we can (and do) accurately sex them by palpating their abdomens and seeing whether or not milt is expressed. A comprehensive scientific report would mention the method of sexing the fish, but the Cruise Report is not a comprehensive scientific report. That said, it's easy of to include and we'll do that in future. Thanks for the feedback.

[Dabalone]

So Marty, striped bass still the favorite whipping boy in the Delta and river system? What are the studies showing for striped bass predation and decline of salmon numbers? Any info appreciated.

Thanks in advance

[Lightly Simmered]

That is some excellent data, and I commend you for sharing that with us fisherfolk.

I must ask though, what is the purpose of collecting that data... what are the deliverables? It is useless for enumerating the population. It is useless for enumerating predation effects at the DM Canal or the CA Aqueduct. It's barely effective at comparing last year's population of fish to this year's population at that same reach. Why? Why spend that money?

Fyke Traps and water management? Interesting stuff, but it never says which way to point the spigot.

[Marty Gingras]

That is some excellent data, and I commend you for sharing that with us fisherfolk.

We produce the report (and one like it for sturgeon tagging) to sort of 'close the loop' with stakeholders who know we tag fish and wonder what we saw. What's in the report is descriptive rather than the sort of information on which management actions are taken.

I must ask though, what is the purpose of collecting that data... what are the deliverables?

Information on the fish we tagged (e.g., recaptures by anglers; recaptures by us) will later be used to estimate striped bass abundance, annual harvest rate, annual survival rate, etc. Those statistics are only possible to calculate after at least a year has elapsed since tagging.

It is useless for enumerating the population.

Not the case. Unless we tag fish, we can't use mark-recapture statistics to estimate striped bass abundance, annual harvest rate, annual survival rate, etc. We are working on an article about striped bass status and trends and I'll post it here when it's ready, but see here (pages 16-39) for an example of what we do with tagging and recapture data:

http://nrm.dfg.ca.gov/FileHandler.ashx?DocumentID=26562

It is useless for enumerating predation effects at the DM Canal or the CA Aqueduct.

Not sure what you mean by '...at the DM Canal or the CA Aqueduct...'. If you mean 'at the points of diversion', then you are correct and we don't claim it is. The estimates of striped bass abundance we produce based on tagging and recapture data have provided the quantitative basis for estimating predation by the striped bass population as well as by subsets of the population (e.g., by age and/or sex). See here for an example of what has been done (and can only be done) w/regard to predation because we tag fish:

http://www.escholarship.org/uc/item/1c788451

It's barely effective at comparing last year's population of fish to this year's population at that same reach.

See above.

Fyke Traps and water management? Interesting stuff, but it never says which way to point the spigot.

Not the case. An understanding of striped bass demographics (by tagging adults) and the production of young striped bass (by towing nets in the delta) has allowed us (and others) to look at the effects of flow on striped bass production.

The relationship between flow and striped bass production used to be fairly simple and our findings were used in the 1980s to protect flow for striped bass, but since invasion of the delta by a non-native clam the relationship has become a lot more complicated and difficult to discern.

[Lightly Simmered]

Thank you. That is a well thought out and informative reply. Much better than my ramblings at wee hours.

I understand that the purpose of the study/monitoring isn't to see what they're eating, but did ya take at peek into any stomach contents?

[Marty Gingras]

Thank you. That is a well thought out and informative reply. Much better than my ramblings at wee hours.

My pleasure. I'm happy to ave more people interested and aware of what we do and why we do it.

I understand that the purpose of the study/monitoring isn't to see what they're eating, but did ya take at peek into any stomach contents?

Not this season. It's actually a pretty big job to quantify stomach contents in a way that advances the science.

Incidental to taking precise measurements of length, weight and gonad weight for a bioenergetics study, a couple of years ago we looked casually at the stomach contents of some striped bass caught in the traps. Most of it was mush (as usual), but a few lamprey and several very young salmonids were pretty obvious.

[Lightly Simmered]

Again, thank you for your time sharing this data, your insight, and explaining our questions. Like you wrote, it really helps us all understand the "what's" and "why's". Without sounding like I'm kissing up too much (too late probably), it's above and beyond your duties, and you really are helpful in sharing this stuff with us guys beating the water with rods and reels. It's near and dear to us, so I hope you understand that sometimes we (errr, me) get a little snappy if we assume there's an easy finger to point toward a reason for "less fish". That finger is probably pointing the wrong direction or flat out wrong to stick out at all.

On the stomach content stuff, I was just hoping that your fellow researchers had curious minds, like any fisherpeople/scientists should, and that they looked at incidental stuff like that. Not much to write about I know (it does give a good idea for imitations), but anecdotal evidence can get some good ideas off the ground. What that is, I have no idea. That mush, or poop, you speak of by the way... yuck!!! I think it's the same stuff that comes out of a channel cat that's grabbed a little tight... delta muck somehow made more stinky and... ugh, THAT smell and THAT texture... UGH!!!

On the "why" stuff, any hypotheses on the ~50:1 m:f ratio? Is that true of the entire Sac/SJ population? Without looking it up, I'd guess that is very different than 'normal' populations on the East Coast. Chemical pollutants? Selective harvest by anglers? Movement/migration/trap efficiency? (i.e. location of traps, timing of traps, or method of trapping selecting for smaller fish and/or males?)...? Curious stuff that I'd think sends red lights somewhere. (That said, me and thinking don't always get along )