New Zealand mud snails in Falling Springs hatchery

[Mike]

Special regs are also associated with stocked fish in many cases. Saying infected PFBC hatcheries are ruled out as the cause when FS gets it’s fish from a hatchery in an infected waterway is not a believable notion. these special regs areas have both anglers and hatchery fish coming in.

I examined the above list and compared it to the traditional or the most likely traditional (before this yr) PFBC hatchery assignments. Only four of the streams on the list (based on my comparisons) appeared to be traditionally stocked with fish directly from the 2 affected PFBC hatcheries from what I can tell. I am uncertain about another, although it appears to me that it wasn’t.

 

[pcray1231]

So FSB already had snails. The simplest explanation of how they got into the hatchery is from the stream.

As far as balance, I don't really believe much of "balance" in nature. I absolutely believe one species can have an effect on another, so yes, I believe invasives will impact the system, and cause a lot of changes. But IMO this idea that everything was originally in perfect balance is a fairy tale. Boom/bust population cycles happened in virtually every ecosystem on earth well before man's influence. Frequently. Due to such things as droughts, floods, disease, natural range expansion of other species, volcanic eruptions, you name it. A careful study of historical animal populations reveals this. All evidence says prehistoric populations could be on the verge of extinction one year and thriving only a few years later, and vice versa. That's NORMAL in nature. It's not like populations of ANYTHING would be stable without us. Humans are the most stable population the Earth has ever known, and it's not close.

That does not excuse man from adding more triggers, such as chemical, habitat, invasives, etc. Just always strikes a nerve when people talk about balance, species finding their niche, etc. It's a little bit of a fairy tale.

 

[Fish Sticks]

I examined the above list and compared it to the traditional or the most likely traditional (before this yr) PFBC hatchery assignments. Only four of the streams on the list (based on my comparisons) appeared to be traditionally stocked with fish directly from the 2 affected PFBC hatcheries from what I can tell. I am uncertain about another, although it appears to me that it wasn’t.

I guess one would have to look at coops with known infestations prior to discovery of mud-snails at FS and as well as coops that historically and currently get fish from the original two hatcheries and where they went. To see where they went one would need stocking receipts.

 

[silverfox]

So FSB already had snails. The simplest explanation of how they got into the hatchery is from the stream.

As far as balance, I don't really believe much of "balance" in nature. I absolutely believe one species can have an effect on another, so yes, I believe invasives will impact the system, and cause a lot of changes. But IMO this idea that everything was originally in perfect balance is a fairy tale. Boom/bust population cycles happened in virtually every ecosystem on earth well before man's influence. Frequently. Due to such things as droughts, floods, disease, natural range expansion of other species, volcanic eruptions, you name it. A careful study of historical animal populations reveals this. All evidence says prehistoric populations could be on the verge of extinction one year and thriving only a few years later, and vice versa. That's NORMAL in nature. It's not like populations of ANYTHING would be stable without us. Humans are the most stable population the Earth has ever known, and it's not close.

That does not excuse man from adding more triggers, such as chemical, habitat, invasives, etc. Just always strikes a nerve when people talk about balance, species finding their niche, etc. It's a little bit of a fairy tale.

Regarding stability, I think the dinosaurs had a few million years on us. There's a huge difference between natural events that brought neighboring species into contact with one another and human-caused species mixing from around the globe. There's an even bigger difference when it's encouraged and defended.

I believe the term is equilibrium, and yes, it's always temporary, depending on the timescale you chose. If you have a species that has been present in a location for, say the last 20,000 years (since the Pleistocene ice age), and then man introduced species within the last 200 years that displaced that species, is that a "natural" occurrence akin to a landslide 50 million years ago mixing two neighboring species? Those boom/bust cycles took place over hundreds, thousands, or even millions of years. That's not at all the same thing as humans moving species around within the past 200 years. The rate of extirpations has gone through the roof since we learned how to build boats.

 

[Fish Sticks]

Regarding stability, I think the dinosaurs had a few million years on us. There's a huge difference between natural events that brought neighboring species into contact with one another and human-caused species mixing from around the globe. There's an even bigger difference when it's encouraged and defended.

I believe the term is equilibrium, and yes, it's always temporary, depending on the timescale you chose. If you have a species that has been present in a location for, say the last 20,000 years (since the Pleistocene ice age), and then man introduced species within the last 200 years that displaced that species, is that a "natural" occurrence akin to a landslide 50 million years ago mixing two neighboring species? Those boom/bust cycles took place over hundreds, thousands, or even millions of years. That's not at all the same thing as humans moving species around within the past 200 years. The rate of extirpations has gone through the roof since we learned how to build boats.

This stat from EPA speaks to the extirpations and extinctions being driven in a large part by AIS

“Invasive species are thought to have been involved in 70% of this century's extinctions of native aquatic species”

 

[silverfox]

This stat from EPA speaks to the extirpations and extinctions being driven in a large part by AIS

“Invasive species are thought to have been involved in 70% of this century's extinctions of native aquatic species”

I've seen quoted multiple times that nonnative species are also the #2 cause for extinctions.

 

[pcray1231]

Those boom/bust cycles took place over hundreds, thousands, or even millions of years.

No, that's the point I was trying to make. It's hard from fossil record because dating isn't super precise. But evidence suggest boom/bust cycles happened on yearly or several yearly timescales just like they do today. We're not talking slow gradual decline over 10's of thousands of years. We're talking about populations being cut by 60% in a year, and then recovering in the next 2 or 3 years, only to have it happen again. That is a NORMAL state of affairs in nature. Nothing is ever constant, and I'm not talking slow movement, I'm talking radical changes in population structures every couple years.

There are two real evolutionary strategies here. There are larger, longer lived animals. They tend not to vary as much in population. They also tend to be more mobile. Slow declines, slow advancement. One bad summer or flood, some die, some go to greener pastures, but you don't get a terrible collapse of their overall population. But when declined, they don't recover as well either, it takes them a long time to breed and fill "voids", so their strategy is to outcompete other species even when in the minority. The other strategy is to live short and reproduce fast. These animals don't compete in the long term anywhere. They take advantage of openings, get there first, and just outbreed everything else and enjoy their boom. During the booms, the range spreads, and hopefully you seed new territory. Eventually a bust comes, other animals outcompete you, and your population falls back to low levels or even leaves an area entirely, but not before that boom seeded 3 new areas...

Same as forest do. When you clearcut an area, it gets taken over by fast growing weeds, progressing to the faster growing trees, eventually the longer lived and slower growing stuff takes it over. Until a flood, fire, tornado, something knocks it out and you restart the cycle. The same occurs with animals. Something happens, wipes everything out in an area. And the fast reproducing critters pour in and just overpopulate. Boom. There may be a few predators around but not enough, they breed quicker, that's the population's strategy. Such a boom is attracting the bigger, slower reproducing things though, and htey'll catch up. When they do, they'll reach a tipping point and trim back the fast breeders. With the rapid boom strategy, comes the rapid bust. The population dies back to low levels or goes away entirely, but not before seeding some new areas, ready for it's next spot to boom.

 

[troutbert]

Almost every stream where they have been found so far either has a special reg area on it or it is geographically close to or is a trib to a stream with a special reg area. Only three of the below waters don’t match that description. It would be interesting to see more data from waters not associated, as described above, with special reg areas.

In Pennsylvania, NZM have been reported from at least 13 counties (Figure 4). NZM were first documented within Pennsylvania in 2005 from Lake Erie in the vicinity of Presque Isle State Park (Levri et al. 2007). In 2013, NZM were discovered in Spring Creek, Centre County (Levri et al. 2020). Since 2018, NZM have also been reported in numerous streams and several rivers, many of which are popular trout waters in southeastern or central Pennsylvania including Bald Eagle Creek (Centre/Clinton Co.), Big Spring Creek (Cumberland Co.), Bushkill Creek (Northampton), Cedar Creek (Lehigh Co.), Codorus Creek (York Co.), East Branch Brandywine Creek (Chester Co.), Falling Spring Branch (Franklin Co.)., Fishing Creek (Clinton Co.), Jordan Creek (Lehigh Co.), Lake Erie (Erie Co.), Lehigh River, (Lehigh/Northampton Co.), Little Lehigh Creek (Lehigh Co.), Monocacy Creek, (Northampton Co.), Perikiomen Creek (Bucks Co.), Pohopoco Creek (Carbon Co.) Saucon Creek (Northampton Co.), Schuylkill River (Berks, Montgomery, and Philadelphia Co.), Spring Creek (Centre Co.), Trindle Spring Run (Cumberland Co.), Trout Creek (Lehigh Co.), Tuplehocken Creek (Berks Co.), Valley Creek (Chester Co.), Wissahickon Creek (Philadelphia Co.), and Wyomissing Creek (Berks Co.).

The great majority of these are limestone streams or tailwaters, with just a few exceptions.

None are typical "mountain streams."

 

[silverfox]

Correct; however, the extinction and extirpation rate due (in part) to species mixing has exploded exponentially since we've started moving around the planet. The current mixing of species is unprecedented in the earth's history. So to suggest that this is all just part of the natural order of things is simply not true.

 

[Mike]

The great majority of these are limestone streams or tailwaters, with just a few exceptions.

None are typical "mountain streams."

That’s right. There is some speculation that there are some higher alkalinity requirements for shell/exoskeleton construction, but that remains to be seen. I say that because I used to think the same thing about scuds and then I found them in a mountain-top Schuylkill Co stream with a total alkalinity of less than 1 mg/l.
And if I recall correctly, the headwaters of Sinking Ck, Centre Co are a bog, which is acidic, yet a short distance downstream but well above Colyer Lk one can find crayfish.

 

[troutbert]

That’s right. There is some speculation that there are some higher alkalinity requirements for shell/exoskeleton construction, but that remains to be seen. I say that because I used to think the same thing about scuds and then I found them in a mountain-top Schuylkill Co stream with a total alkalinity of less than 1 mg/l.
And if I recall correctly, the headwaters of Sinking Ck, Centre Co are a bog, which is acidic, yet a short distance downstream but well above Colyer Lk one can find crayfish.

The reason the mud snails are found in limestoners and tailwaters and not in mountain streams may also be related to base flow. Mountain streams have flashy flows. High velocity flows might sweep them away downstream. And in low flows much of the streambed is dry. Both of these might hinder snail populations.

 

[cuboodle]

Truck them to the north fork of the little beaver creek the train derailment chemicals will kill the snails off.

 

[pcray1231]

Correct; however, the extinction and extirpation rate due (in part) to species mixing has exploded exponentially since we've started moving around the planet.

I agree with that. In large part, due to habitat destruction and isolation.

Naturally, a population goes through boom/bust cycles. Locally. But while one location is busting, another is booming, and these locations are interconnected. Development not only reduces the available habitat, but also isolates them, by creating distances between suitable habitats, and barriers like roads and such. When a local habitat goes bust, there's not a constant seed of a few individuals entering from nearby places that are booming.

If the species is extirpated locally, when conditions improve, there's no population to take advantage of it. Which, of course, also leaves a niche open to other invasives entering via natural or artificial means.