Sunday, October 29, 2006

Relative Brain Size Of Males Vs. Female Scarlet Shiners

We have our initial data from examining the relationship between brain mass and somatic (body) mass in scarlet shiners, Lythrurus fasciolaris. This is based on examining 13 females and 27 males. Pooling all the data together yielded a reasonably tight relationship between brain mass and somatic mass. But there were some interesting outliers in the data set, lying fairly far off the regression line. So I separated the data into female and male sets and constructed graphs for each, including regression lines (surprisingly easy in Excel). The graphs are below. In short, they show that there's much less variation in brain size among females than among males. All of the data outliers are for male fish. A measure of this variation is the regression coefficient, R-squared, which varies between 0 and 1. A high value shows a tight relationship between the variables, a low value a weaker relationship. The females' have a high R-squared of 0.84, the males have a much weaker R-squared of 0.3. One would expect males to have more variation in such an important bundle of traits as brain size, since males have a much wider variation in reproductive success that's influenced by brain structures and functions. (Remember, if you click on the graph it will expand in a new window.)

Friday, October 27, 2006

Fish Species List From Hurricane Creek At The Walls Of Jericho

I received the fish species totals from last June's BioBlitz at the Walls of Jericho tract in Jackson County, AL. Three different groups sampled Hurricane Creek for fish. My group used seine nets initially, with a follow-up visit in July with more seining and also snorkeling observations by Casper Cox. The other two groups primarily used electroshocking, which is pretty much the only way some of the larger, more athletic fish species such as bass and redhorse suckers can be taken. Before pooling all of these observations, our group had captured or visually ID'd 26 species which I knew was low. Putting all three groups' results together, 38 species have been found in a roughly one kilometer stretch of a not very big creek. This is a large number by North American standards. My group found three species that the other groups didn't - the sawfin shiner, blotchside logperch, and common logperch, all three found on our second visit in July. Blotchside logperch are a species at risk, and also notoriously difficult to capture because of their preferred habitat of deep pools at the base of riffles. So we done good... The one glaring omission on this list to date is that no one has found any madtom species, a widespread group of small catfishes usually found in highland streams like Hurricane Creek. They're hard to find since they're nocturnal and often spend days in a burrow along a bank. We hope to do that by spring, anyway(!).

Anyway, here's the list:

(Binomial, Common Name)

Cottus carolinae, Banded Sculpin
Catostomus commersonii, White Sucker
Moxostoma duquesnii, Black Redhorse
Hypentelium nigricans, Northern Hog Sucker
Ambloplites rupestris, Rock Bass
Lepomis auritus, Redbreast Sunfish
Lepomis cyanellus, Green Sunfish
Lepomis megalotis, Longear Sunfish
Micropterus dolomieu, Smallmouth Bass
Micropterus salmoides, Largemouth Bass
Fundulus catenatus, Northern Studfish
Fundulus olivaceus, Blackspotted Topminnow
Campostoma oligolepis, Largescale Stoneroller
Clinostomus funduloides, Rosyside Dace
Hemitremia flammea, Flame Chub
Hybopsis amblops, Bigeye Chub
Luxilus chrysocephalus, Striped Shiner
Lythrurus fasciolaris, Scarletfin Shiner
Notropis albizonatus, Palezone Shiner
Notropis leuciodus, Tennessee Shiner
Notropis telescopus, Telescope Shiner
Notropis sp. "sawfin shiner", Sawfin Shiner
Pimephales notatus, Bluntnose Minnow
Rhinichthys atratulus, Blacknose Dace
Semotilus atromaculatus, Creek Chub
Etheostoma blennioides, Greenside Darter
Etheostoma caeruleum, Rainbow Darter
Etheostoma duryi, Black Darter
Etheostoma flabellare, Fantail Darter
Etheostoma jessiae, Blueside Darter
Etheostoma kennicotti, Stripetail Darter
Etheostoma nigripinne, Blackfin Darter
Etheostoma nigrum, Johnny Darter
Etheostoma rufilineatum, Redline Darter
Etheostoma simoterum, Tennessee Snubnose Darter
Etheostoma zonale, Banded Darter
Percina burtoni, Blotchside Logperch
Percina caprodes, Logperch

Monday, October 23, 2006

Return To The Walls Of Jericho Tract Last Saturday

I wrote this post last night, but through a series of stupid keystrokes lost it... So here it goes again.

We spent Saturday at the Walls of Jericho property. Jennifer, Christian and Andrew joined me to meet land steward Nick Sharp who graciously drove us in via the hellacious road. I was hoping to find blotchside logperch and flame chubs in Hurricane Creek, and try to make the 2 km hike from the main campground area along the creek to the famous Walls of Jericho for which the property is named.

We actually did find one juvenile flame chub, and I think we could have caught more. They were in an unusual feature, what looked to be a natural ditch alongside the creekbed. I suspect this ditch is fed by a slow spring seep, since the water was clear and cool (the creek itself was 12 degrees C, quite a drop from July). Several other fish we caught all turned out to be juvenile creek chubs when I looked closely and saw that they had a black dorsal spot rather than the red blaze typical of flame chubs. Below is a photo of this "ditch" feature, visible in the left-middle of the picture as a circular shadow:

We netted lots of rainbow, black and Tennessee snubnose darters, and a single redline. No blotchside, not even any greenside, logperch or speckled darters which are also present. I'm now convinced that both black and Tennessee snubs are present. It's unusual to find sympatric species of snubnose darters, but it's true in Hurricane Creek. Some of the male black darters we netted were some of the biggest I've ever seen. I showed a ziplock baggie of darters to some hikers from a local conservation group, and blew their minds with the male rainbows and the redline. Even knowledgeable outdoors people usually have no idea that such colorful fishes exist in local streams. Below is a photo of, left to right, Andrew, Christian and Jennifer at our first seining site downstream from the campground/trailcrossing.

After lunch we started a hike to the Walls of Jericho. This is a striking geological feature, a limestone bowl being scooped out by gushing springs between 500 meter tall sandstone ridges. Limestone is much softer than sandstone, so a deepcut valley with Turkey Creek running over limestone debris runs down into Hurricane Creek. It's one of those things you have to see to fully appreciate. The trail into it is narrow, muddy, and lifethreatening, hugging the base of the sandstone cliff on the south side of the canyon. Christian had to give up not even halfway in because she was wearing flipflops(!). Once we made it in to the flowing springs, we immediately noticed that there were fish in the pools, apparently some kind of cyprinid minnows. But we had no nets so we made no real effort to snag any. Next time... And Nick told me that there are fish in a small creek that flows over the lip of the head of the limestone bowl. I've posted one picture below that gives some idea of what the place looks like. It's looking up the head of the bowl, with the lip in the middle with a tree trunk stuck in it from an earlier flood event. The sandstone cliffs rise to the left and right. The whole setting is more primeval than anything I expected to find in modern Alabama. Really, you gotta go!

Wednesday, October 18, 2006

Preliminary Parasites Data, Alright!

Christian has given me her Excel dataset from examining scarlet and striped shiners for Dactylogyrus gill parasite infestations in Swan and Limestone Creeks in north 'bama. This is a case where negative results are interesting; we found no statistically significant different in gill parasites per fish either between species, or between creeks. In principle there should be some difference, since the creeks are in different basins and the parasites are different species that infect specific species of fish. The one trend, albeit a weak one, is that fish have more parasites as they get bigger and older. This could mean that they're bigger targets for parasites to settle out of the water on the gills, or just that with time a given fish picks up more parasites by chance. Probably about 10% of the examined fish had no parasites (I should mention that we only examined the right gill structures as a proxy for all of the gills....)

Below are the data for all scarlet shiners (Lythrurus fasciolaris) examined from both creeks. A trend line shows the weak tendency for larger fish to have more parasites, with a correlation coefficient of 0.02 (that's what I mean by weak):

Below are the data from Swan Creek combined for both species. Again, there's a weak trend represented by the line, and a low correlation coefficient of 0.04:

So what does it all mean? I'm not completely sure yet, and that's what I'll be cogitating about as we further kick around the data.

And I still haven't talked more about Root Boy Slim and the Sex Change Band in my Vertebrate Reproduction class, I'll to get it together on that too.

Tuesday, October 17, 2006

Sex Changing, Hormones, Fish Brains And The Usual Stuff

I was finally able to use some of my own current research in a lecture yesterday, showing my annotated digital image of a dorsal view of a scarlet shiner brain. This was in my Vertebrate Reproduction class and we're talking about different forms of sex determination in fishes, variously genetic, behavioral and temperature. Any internal signalling system has to go through the brain, of course, so it makes sense to look at a typical fish brain and point out where important features likes the hypothalamus and preoptic area reside. I also had a chance to mention one of my favorite bands from the late '70s, Root Boy Slim and the Sex Change Band, but that was a serious digression.

The good thing about doing this class is my realization that for our research on male scarlet shiner coloration and differentiation we should look at 11-ketotestosterone (11-KT) levels as the key androgen shaping secondary sexual characteristics. I had been thinking that the more common form of testosterone would be OK, but 11-KT is more potent for sexual activity in male fishes. It's more difficult to assay blood plasma levels, probably existing at about 15 picograms per microliter, but Jennifer says that she feels confident to do it so we will. The ELISA test kit for this costs 'bout $240 so that's what I'll request from the department.

Wednesday, October 11, 2006

Getting Out Again To The Creeks Soon... And A Mexican Note

I've been holding off updating for a coupla days, thinking that I'd have something interesting to report. And now I do, but it's relevant to Mexico. One of our NANFA Conservation Research Grant awardees, Nick Lang from St. Louis University, told me this morning that he and Dean Hendrickson from UTexas found a pair of Etheostoma segrex darters in Mexico in a creek where its status is tenuous. This creek might also be the only habitat for this species. NANFA gave Nick $700 in support of his travels from St. Louis to north Mexico to look for this fish, probably one of the rarest darter species. This is something to celebrate, as long as a pair exist in nature there's hope.

In the more mundane world of north 'bama we'll probably do a collecting trip next Monday to Swan Creek in Athens. And I've confirmed with Nick Sharp for a rendezvous to drive in to the Walls of Jericho on October 21 to do more seining and fish watching. Nick has to be on duty that day anyway, so it gives him an excuse to do wider patrolling of the property and hopefully to hang out with us for a while and check out the fishes. It'll be a busy day at the Walls that day; a local river conservation group is hiking in from the other side of the property, and a research team from Alabama A&M is banding birds on the property. I hope to introduce several students to the property, and to the possibilities of doing some kind of research project there in the next warm season.

Wednesday, October 04, 2006

Thinking 'Bout Flame Chubs

I've started to process what I've seen with flame chub distributions in north 'bama over the last 17 months. As part of this I've been googling around in search of any recent collections of flame chubs. The most interesting document I've found is "Response of Fish Communities to Cropland Density and Natural Environmental Setting in the Eastern Highland Rim Ecoregion of the Lower Tennessee River Basin, Alabama and Tennessee, 1999" written by Jeffrey R. Powell for the U.S. Geological Survey. Hell of a title, no doubt about that. What Powell and his co-workers did was to visit 20 creek sites in the geological region of the Eastern Highland Rim (around me here in Huntsville, west into Lawrence County, AL, and northeast to the Barrens of Tennessee) and do in-depth sampling with both seines and electroshockers. They related the diversity and abundance of fishes they found to various environmental and geological parameters.

It's interesting to me because they visited several sites that I've sampled for flame chubs. They found a single flame chub at a site we visited last summer and found none, Hester Creek in Madison County, AL. They also found 10 flame chubs at a site on Beaverdam Creek in Madison County, but I'm not sure yet if it's the same site we visited last year and found none. On the other hand, they found no flame chubs in Piney Creek, Limestone County, where we found them, and the same is true for Limestone Creek in Madison County (admittedly I've only found one there) and Indian Creek/Dry Creek in Madison County where we found a half dozen or so flame chubs. In total, Powell's group found flame chubs at 4 of their 20 sites. This ultimately confirms my findings of flame chubs being in decline, since the sites they visited are in the heart of flame chub territory and all are conducive to flame chubs in terms of stream size, flow and water chemistry. The most flame chubs they found, 10, was at Beaverdam Creek in AL, and 9 in Bradley Creek in the Tennessee Barrens.

This report is good work and it's an interesting baseline of fish communities. I found the report just by googling "flame chub", but if you're interested, the report is "Water-Resources Investigations Report 02-4268", part of the National Water-Quality Assessment Program.