Friday, May 25, 2007

Female Telescope Shiner GSI At Hurricane Creek

I finally put together the data for female telescope shiner monthly GSI (gonado-somatic index) that we have for February through May of this year. It tells a more interesting story than I'd thought. Not surprisingly the value starts out low in February, when the fish are just beginning to prepare for reproduction, and increases some in March. But the jump to April was sharper than I'd thought, and is only slightly lower than May's 11.3. In truth there's a wider range of values for May, upwards of 25 for a high, which is very high for shiners; that means that 25% of their body mass is made up of the ovaries and developing oocytes. The thin bars in the graph represent standard error, the predicted range of where the true mean would be if we sampled every single fish in the creek.

The whole point of this, of course, is to define the peak spawning season for this species which seems to begin in April and go through... well, we don't know yet. I predict that the GSI value will remain high through July, and drop off in August. But we'll see. Our next trip to the Walls of Jericho is next Saturday, June 2. See you there? (Click on the graph to see it larger in a new window.)

Tuesday, May 22, 2007

Telescope Shiners' Whole Ovaries, In A Time Series

We've been working on describing the reproductive status of telescope shiner ovaries in the last several weeks. This takes two connected forms: describing the maturity of the ovary, and describing the developmental stages of the oocytes inside the ovary. We've made photographs of ovaries using a digital dissecting miscroscope, and then torn apart the ovary to separate the developing eggs which are then photographed in groups of about 50 mounted on microscope slides. The whole ovary images allow us to characterize their status at our leisure and double-check our assessments later, and the egg photos allow us to count, describe and measure the eggs using the digital software Motic 1.2. Eggs are stored in 10% buffered formaldehyde for further examination.

Below is a series of three whole (or almost whole...) ovaries from individuals collected from Hurricane Creek at the Walls of Jericho in March, April and May. All were photographed at X10 magnification, and the image area is about 18 mm wide. The March ovary has visible oocytes that are in the early stages of vitellogenesis, being loaded with phospholipoproteins. A typical oocyte in this ovary is about 0.7 mm in diameter. Both lobes of the ovary are visible, with the oviduct (exit) visible in the lower left.

The April ovary is larger, with the creamy yellow color indicating near-maturation. The largest yellowish oocytes are about 1.1 mm in diameter and are in late vitellogenesis, closer to being ripe. Less mature developmental stages are also present.

The May ovary is bigger still, with only one of the lobes mostly visible in this photo. The ovary is nearly transparent and the outer membrane is stretched tightly. Fully ripe oocytes are visible in the darker reddish area which is close to the oviduct. These largest oocytes are 1.4 - 1.5 mm in diameter. The full range of developing oocytes is present in this ovary.

March ovary:
April ovary:
May ovary:

Sunday, May 20, 2007

New Length-Weight Data For Telescope Shiners

We've been working on the 25 telescope shiners collected at Hurricane Creek on May 5. Their length-weight data are plotted in the graph below (in light blue) along with the February, March and April collections. We didn't find any individuals quite as big as several we found in April, but the overall average size of the fish is significantly larger based on a two-tailed t-test comparing April and May. Once again we found a lot more females, by a ratio of 18:7. Removing and weighing gonadal tissues also yields some very high GSI values (ovarian mass / body mass) for some of the females, as high as 25. So we found a group of reproductively active, well-fed fish on May 5. And remember, if you click on the graph below it will appear in a separate window in legible form.

Monday, May 14, 2007

Drawing Scarlet Shiner Blood, etc.

Jennifer has figured out how to draw blood from scarlet shiners. If you're good at it, with a large alpha male, you can get 50 microliters. She was able to get blood from about 20 scarlets last week, which is now in deep-freeze at -80 deg. C. We're getting close to attempting ELISA for 11-ketotestosterone assays. Enrique was able to remove the brains from the scarlets after bleeding, so he can run some more Westerns on them to determine NMDA receptor levels. With any luck we'll get a full picture of various measures of sexual differentiation in the species.

I spent several days at the Dauphin Island Sea Lab last week for the Program Committee meeting. The Sea Lab seems to be in good shape, with summer school enrollment up and a range of interesting course offerings. The state of Alabama has allocated $4.5 million this coming year for the Sea Lab, up from this year's $3.8 million.

Rachel will do her Master's defense on May 25 for her black darter work. I just received the first full version of her thesis. There are interesting differences she found between the two study sites, such as one population being significantly bigger and more fecund than the other. I'll tell you the whole story later...

Sunday, May 06, 2007

A Warm Day At Hurricane Creek, Finally

We made it out for a telescope shiner collecting trip at the Walls of Jericho yesterday. This was the first warm day in our collections, and three of us waded in the creek without waders on, while Loren opted for waders; the water was a brisk 14 deg. C. It took us about 5 hours of working the creek to collect 25 telescopes, less than our optimal goal of 30, but I think it'll be OK. We found some darters we haven't encountered much before like bluesided (Etheostoma jessiae) and fantail (E. flabellare), both in interesting breeding colorations. There was a threat of rain all day and we could hear distant thunder. I guess for that reason we only saw three other people on the property. Andrew who has been working with us was supposed to be camping there with his dorm mates, but I guess they backed out.

I finally took a photo of the gate into state property. To get to this point one has driven about 3 miles on a badly rutted road, and opened and relocked three gates. The gate pictured below is the most intense of them; notice the spikes sticking out to defend the gate against being opened by a vehicle pushing against it. The spikes are at the height of a typical radiator. The lock itself is in a steel-shielded box on the left end of the gate, making it almost impossible to blast open with a gunshot. And running off downhill on the right of the photo is the beginning of a reinforced fence of round steel pipe about a meter high to block any vehicles from making an end-run around the gate. This fence runs about 200 meters down to Hurricane Creek, which is steep-banked at this point.
On the way out we spotted an owl sitting in a tree right by the road, as shown below. I think the owl is a barred owl, but I could be wrong. I just stuck my camera outside the truck's window and took two shots. The owl just sat and stared.
And speaking of my truck, I finally have magnetic signs identifying who and what I am. This will hopefully head off any more confusion from some of the landowners whose property we must cross to drive onto state lands. I thought the signs look snazziest on the panel to the rear of the doors, as you can see in the photo below. I hope you agree.