Smallmouth genetics

[Tim Smith]

This article might be of interest to some here.

 

Molecular Ecology

Volume 16 Issue 8 Page 1605-1624, April 2007

 

Broad- to fine-scale population genetic patterning in the smallmouth bass Micropterus dolomieu across the Laurentian Great Lakes and beyond: an interplay of behaviour and geography

CAROL A. STEPIEN, DOUGLAS J. MURPHY and REX MEADE STRANGE*Great Lakes Genetics Laboratory, Lake Erie Center and Department of Environmental Sciences, The University of Toledo, 6200 Bayshore Road, Toledo, OH 43618, USA

 

Abstract

 

Analysis of population genetic relationships reveals the signatures of current processes such as spawning behaviour and migration, as well as those of historical events including vicariance and climate change. This study examines these signatures through testing broad- to fine-scale genetic patterns among smallmouth bass Micropterus dolomieu spawning populations across their native Great Lakes range and outgroup areas, with fine-scale concentration in Lake Erie. Our primary hypotheses include whether genetic patterns result from behavioural and/or geographical isolation, specifically: (i) Are spawning groups in interconnected waterways genetically separable? (ii) What is the degree of isolation across and among lakes, basins, and tributaries? (iii) Do genetic divergences correspond to geographical distances? and (iv) Are historical colonization patterns from glacial refugia retained? Variation at eight nuclear microsatellite DNA loci are analysed for 666 smallmouth bass from 28 locations, including 425 individuals in Lake Erie; as well as Lakes Superior, Huron, and Ontario, and outgroups from the Mississippi, Ohio, St. Lawrence, and Hudson River drainages. Results reveal marked genetic differences among lake and river populations, as well as surprisingly high divergences among closely spaced riverine sites. Results do not fit an isolation-by-geographical-distance prediction for fine-scale genetic patterns, but show weak correspondence across large geographical scales. Genetic relationships thus are consistent with hypotheses regarding divergent origins through vicariance in glacial refugia, followed by colonization pathways establishing modern-day Great Lakes populations, and maintenance through behavioural site fidelity. Conservation management practices thus should preserve genetic identity and unique characters among smallmouth bass populations.

[Steve S.]

Okay, I admit I had to Google a few of these words because I had no clue!

 

Tim, is this study referenced to provide some insight to my inquiries about possible genetic differences amongst regional populations of smallmouth? I've read it a few times and I am absorbing a little more each time. Maybe you can break it down faster than my mind can!

[Tim Smith]

Steve:

 

Long story short, the author believes that the genetic differences in smallmouth bass in the Midwest are driven by:

 

1. Patterns of recolonization from thermal refuges after the glaciers melted.

 

2. Spawning site fidelity (that causes smallmouth to return to the same area to spawn year after year and localizes their genetic material in one geographic location).

 

3. Habitat (lakes vs. rivers).

 

He does not support the hypothesis forwarded by some that genetic differences increase with geographical distance between populations.

 

In other words, genetically vastly different fish may occur in the same river, but there is an underlying pattern of genetic differences across regions. I'd have to read the full article to know what those regions were.

[Norm M]

Very interesting idea that you can have different genetic groups of a species in the same flow . One of the selling points of the walleye stocking program on the Kankakee was that the fish would all come from the Kankakee/Iroquois rivers thus insuring that they would be native fish that were suited to the river .

 

I would have to think that even though there may be different genetic groups of a species within the same flow that they all nonetheless be genetically programed to survive best in that particular flow .

 

I do wonder what effects may come from mixing two or three genectically different groups even those from the same flow . Would hybrid vigor be possible from this pairing and could some of the trophy fish be a result of natural mixing at the confluence of two seperate genetic groups ?

 

Another question in my mind is could one of the genetic groups expand thier range in that flow as the river ages which could possibly make changes that suit that group just a little better ?

 

This gives me something else to ponder on those days when the smallies are a tad reluctant and I'm just not in the mode to switch species .

[Tim Smith]

Very interesting idea that you can have different genetic groups of a species in the same flow . One of the selling points of the walleye stocking program on the Kankakee was that the fish would all come from the Kankakee/Iroquois rivers thus insuring that they would be native fish that were suited to the river .

 

Using genetic stocks from a native flow preserves at least some of the genetic diversity of that flow, but might not preserve it all. Site fidelity and nesting behavior creates another layer of complexity. From the juvenile's perspective, going back to the place you wer successfully reared sure beats a random shot in the dark for a new place to spawn. Any adaptation that allows juveniles nesting site choice to benefit from their parent's success has a good chance to be passed on. That dynamic doesn't happen in all species and it may or may not happen in walleye.

 

I would have to think that even though there may be different genetic groups of a species within the same flow that they all nonetheless be genetically programed to survive best in that particular flow.

 

"Best" is usually a false concept where evolution is concerned. There are levels of adaptation to be considered here. For the individual, there are probably always some seriously sub-optimal genes for a given environment as it exists at a particular moment. But conditions change. So for instance those "bad" genes in a drought year might be "good" genes in a flood year. Those "bad" genes for a cold post-glacial river might be "good" genes when global warming kicks in. There isn't really a "best" because conditions are always changing. The hope is to preserve enough genetic diversity that the population can cope with whatever changes occur within the stream.

 

I do wonder what effects may come from mixing two or three genectically different groups even those from the same flow . Would hybrid vigor be possible from this pairing and could some of the trophy fish be a result of natural mixing at the confluence of two seperate genetic groups ?

 

Hybrid vigor has to do with either increased size or fitness of the offspring of two genetically different parents. I'm not entirely sure at what level of genetic difference something truly becomes "hybrid vigor". Certainly the need for heterozygosity is real. The basic mechanism is this: All species have a pool of harmful recessive genes that only do harm when each parent contributes a copy of that harmful gene to their offspring (i.e. the offspring has 2 copies of that negative gene and is "homozygous" for that trait). Hybridization increases the diversity for each gene in the breeding population and reduces the chances that deleterious recessive genes will occur together in offspring. You always want enough heterozygosity in a population to keep down the number of homozygous deleterious recessives. If you don't have enough heterozygosity, you get "inbreeding depression" (think brother + sister = scenesfromdeliverence).

 

Are trophy fish sometimes genetic hybrids? Eh. I doubt it? Big parents make big offspring.

 

Hybrid vigor doesn't make hybrids a good thing in every case. Florida largemouth bass crossed with northern largemouth bass make really, really lousy parents and their offspring don't survive well. If the strains are different enough, when you cross them they fare poorly in nature..sometimes very poorly (think gorilla + human = holyhelldontevengothere). This is called "outbreeding depression" and it's the main reason stocking programs have begun trying to minimize the use of stocks from outside the natural breeding population for a given site (for instance Trent's program on the Kaskaskia).

 

Another question in my mind is could one of the genetic groups expand thier range in that flow as the river ages which could possibly make changes that suit that group just a little better ?

 

Yes. Any environmental change at all can favor one genetic group over another IF those genes are linked to favorable adaptations in the new environment.

 

The study cited above, and most genetic studies of this nature make no such assumption about the adatations (or even the morphology) associated with the differing genetic strains they have identified.

[Norm M]

Thanks for the response Tim , gives me more to ponder .

 

Are you going to be at Oakwood this Saturday ?

[Tim Smith]

Are you going to be at Oakwood this Saturday ?

 

That's the plan, Norm. Will we see you there?

[Norm M]

Lord willing and the crick don't rise .

[jamie]

Very interesting subject. In doing our own research over here we have found at least 2 species of smallmouth(northern & Neosho) and 1 hybrid mix (meanmouth). It's very interesting to see that these may indeed branch out further to specific waters subspecies. I'd like to say I caught a Batavia Fox Northern Neosho with a touch of Geneva Dam Strain mixed in. Ahhh the possibilities.

[Mike Clifford]

Were there ever any post-stocking studies done on the Kankakee from those walleye stockings, Norm?

 

I certainly enjoyed knowing that we can catch trophy eyes once again, but would also like to know what the effects are on other native species- specifically smallmouth.

 

This sounds like a familiar line of thinking to you, I know- but it deserves a look.

Absolutely nothing has been done to slow the sedimentation problems, and those walleye stopped reproducing for a reason. Nature has a funny way of evening the score, and man steps in and decides what is best for us at the time.

Will the smallies follow suit?

Eventually, they will.

[Norm M]

Mike ,

 

I don't think the walleyes have had much if any impact on the smallie population . While the numbers of 19-20 inch smallies is down this year that is something I have been expecting and predicting . Those are mostly old fish that are dying from natural causes due to old age in my opinion .

 

My total numbers of smallies is about what it shoud be given that I have spent more time pursuing other species . My walleye numbers are the best they have ever been . I attribute that to a larger population of walleyes than in times past , more time fishing for them and above all else I know I'm a better fisherman than I was when the walleye population was at fishable size years ago .

 

A bigger concern to me than interspecies competition is the continuing loss of habitat and degradation of existing habitat for many of the native species to the river . Northern Pike in particular in my favorite stretches have become almost non existant mostly due to the loss of spawning areas . We have been losing both walleye and smallie spawning areas ever since the increase in sand and silt over the K3 dam started 2 years ago . What is just as bad is the smothering of rocky areas that support the bottom of the food chain . When the bottom of the chain suffers it doesn't take long to bring down the top .

 

Yes the river is changing, increased sedimentation , larger areas of weedgrowth ,more shoreline development , more subdivisions dumping lawn chemicals into the storm sewers, the quarry on Rock Creek , more water being used for irrigation , increase in numbers of species such as largemouth bass and gar in areas they were to quote a biologist "present but not in significant numbers ".

 

I don't think it will become a largemouth river in my life that's left but it may in my son's lifetime .

 

Tim , sorry for the hijack .

[Jim Kast]

Are you going to be at Oakwood this Saturday ?

 

Is there going to be acceptable wading conditions in the general area? If so, I'll be there, always wanted to fish that waterway. If not, I'll bring my PFD and float over the deep holes!

[Tim Smith]

Is there going to be acceptable wading conditions in the general area? If so, I'll be there, always wanted to fish that waterway. If not, I'll bring my PFD and float over the deep holes!

 

Bring it, Jim!

 

The flows are actually low just now. They're just a mite stirred up from the rain...they'll be in great shape by Saturday.

 

This is starting to look like a pretty fun outing!

[Norm M]

Maybe someone will hit the trifecta , smallie , spot and smallie/spot hybrid . Be on the look out for a toothy critter with an affinity for X-Raps .

[Tim Smith]

Maybe someone will hit the trifecta , smallie , spot and smallie/spot hybrid . Be on the look out for a toothy critter with an affinity for X-Raps .

 

It's usually a largemouth in the third slot, Norm. Check the belly spots.

 

Don't hold your breath for walleye.

[Norm M]

Tim ,

 

T'was a musky that commited the theft . I'm 2 for 4 on the critters down yonder .

 

Got a pickerel one day with Phil , but don't remember which flow .

 

I'll bow to your expertise on the bass ID . The ones that I thought was hybrids had kinda of a smallie look but somewhat of a toothpatch like a spot .