YOY Smallmouths: Susquehanna River - 2012

[Fishidiot]

The PFBC has come out with the 2012 Young of the Year smallmouth bass survey for 2012. The YOY survey is intended to reflect spawning success of SMBs for that year. The short version is that the North Branch had a good year; the West Branch had a poor year. The main stem was good above Harrisburg but poor below it - at least by the standards of what has been seen in the last decade since the bass crash in the main stem and lower river. All things considered, it was probably about what one would expect. YOY counts can vary a lot by year with depending on weather and water levels.

Survey

 

[TimMurphy]

Dear Dave,

I know I'm not a scientist or statistician but when I saw that the while the success ratio appeared to be low in the mid Susquehanna at least it appeared to have doubled each year from 2010 to 2012.

But when I looked at the incidence of disease I saw that it also seemed to double as represented by the graphs from 2011 to 2012 what inspiration I had initially vanished.

Like I said I'm not a statistician, but if spawning success doubles each year and disease levels double each year there will probably never be a net growth in the population, at best you will keep a steady level that is relatively sparse in numbers compared to 15 years ago.

Regards,

Tim Murphy :-(

 

[barrybarry]

Tim... I'm kind of hoping you're statistician savant.

 

[barrybarry]

I know. I know. The rivers just been so dead lately. Kind of hoping I would see a positive post once and a while. I got nothing.

It did look really nice when I drove over it today.

 

[albatross]

I am a statistician and I agree with Tim...

 

[Fishidiot]

Tim,
You may be right.....and I would have said you're spot-on five or six years ago.

However, in recent years, I've become more skeptical of the correlation between columnaris sores and bass decline. In recent years, sores have been equal or more prevalent in the upper branches where bass populations remain robust. Despite an occasional substandard YOY class (which is predictable) SMBs in the North and West Branch are generally doing well whereas the main stem, especially the lower reaches, continues to fail to produce good reproduction.

From a glass-half-full point of view, one could conclude that things have stabilized with respect to population. My biggest fear five or six years ago was that the crash would extend upstream and we would see similar bass declines all the way up through the branches. This, however, does not appear to have happened (despite the prevalence of sores). I'm increasingly convinced that there is something in the lower river that we have not discovered.
Despite evidence of continued poor YOY in the main stem, the good news is that things aren't getting worse and there may even be some small scale improvement in lower river spawning. An optimist would say we're in an improving trend (although a very slow one).
My guess would be that the survey of adult bass will reveal similar trends as this YOY and the last several years of adult bass surveys.

 

[Mike]

In a simplified, theoretical scenario being given here just to make a point, if disease incidence was the same throughout the river system, survival of diseased fish might vary from location to location due to the presence of other stress factors, such as warmer water temps at night in downstream reaches than in upstream reaches. It appears that not all of the diseased fingerlings die; we have seen what appear to be recovering fingerlings (partially healed fins, for instance) during fall adult electrofishing runs. Those fingerlings are occasionally captured at the same time as the adults, although the focus is on adults during the fall sampling. It appears to be unlikely that the fingerling mortality rate is the same as the disease incidence rate; some appear to survive.

 

[TimMurphy]

Dear Mike,

I understand that evidence of disease does not necessarily mean that the fish will succumb to the disease. However, when the rate of increase in the incidence of disease more than triples in a year while the rate of spawning success barely doubles I can't see how anything can improve? That's what I see in the charts from 2011-2012 on the middle river.

Dear fishidiot,

To expound on what I wrote to Mike, until the ratio between incidence of disease and spawning success is reversed I cannot see how the river will ever improve? Having slightly more fish every year with greatly increased disease levels seems mathematically unsustainable to me.

I sincerely hope I'm wrong with that line of thinking and something surprising happens in the next year or two, but I'm not going to hold my breath.

Regards,

Tim Murphy :-(

 

[Maurice]

We are building a columnerous-pollutant tolerant breed of smallies Tim, be patient. Some fingerlings survive. Invasive species are resilient. If only we could stumble upon the magic bullet for near extirpation of the snakehead.

 

[1wt]

Maurice wrote:
If only we could stumble upon the magic bullet for near extirpation of the snakehead.

I didn't think the snakeheads were that bad in the lower susky? A few big Flatheads, but Snakeheads?

Maurice, you and I fish the same waters. It was a fishermen's paradise twenty years ago...... and now it really stinks!

Remember last year when you posted your trip to Wrightsville (at the John Wright Store) and you only caught one small catfish all night...... you complained about the crappy music there! lol

Ten years ago, the smallmouth bass would smash the white flies with gusto. Great top water fun with White Wulff's at that very spot.

Only five years ago, there were 5 fly fishermen there almost every night (I was one of them) and constant channel cat action on streamers ...... when the bass left, we would fish for anything that bites!

I still fish all the lower Susky spots every few weeks, but it is so terrible..... it makes me sick!

The C&R is a good thing, but I don't see a rebound for the bass.

 

[Mike]

The annual adult bass population surveys are underway on the Susquehanna. These should show whether or not the population has improved, declined, or stayed the same on a broad regional basis. Some of last year's scheduled surveys did not occur because of the high fall flows, so some sites are being sampled for the first time in two years.

 

[Mike]

The YOY SMB have been sampled for 26 years on the lower Susquehanna by Area 6 crews and me. Of the seven lowest YOY abundance indices (number of YOY sampled per 50 m site), four of those seven have occurred in the past four years. The remaining three occurred intermittently throughout the rest of that 26 yr period (sampling sites located from York Haven Dam downstream to Pequea).

 

[pcray1231]

Yeah, Tim's stats don't come out. Consider (just making up numbers to make the point):

year 1: 1000 YOY smallmouth bass, 10% disease rate among YOY fish. So we have 100 YOY diseased fish, and 900 YOY undiseased fish.

Now, both double, so:

Year 2: 2000 YOY smallmouth bass in the same area, 20% disease rate. So we now have 400 diseased fish, a full 4x as many as the previous year! But we also have 1600 undiseased YOY fish, which is still quite a bit better than the previous year. i.e. a net growth in overall undiseased population.

Of course, it can go the other way too, depending on actual numbers. And the two factors are probably somewhat independent, so it makes no difference on what you need to do from a management perspective. Just making the point that saying since both doubled, it's a wash, is NOT accurate.

 

[Chaz]

Is it possible that the river had too many SMb during the years of high catch rates and high populations and that this is just a natural adjustment?

 

[Fishidiot]

Mike wrote:
The annual adult bass population surveys are underway on the Susquehanna. These should show whether or not the population has improved, declined, or stayed the same on a broad regional basis. Some of last year's scheduled surveys did not occur because of the high fall flows, so some sites are being sampled for the first time in two years.

Any news on this Mike?
What's the short version: up, down, or about the same?