Are There Really More Female Than Male Telescope Shiners?
At the end of a hectic week, we sat down this afternoon and finished removing and weighing the gonads from the March 3 collection of telescope shiners. Out of 37 fish, 23 are female and 14 are male (if I counted correctly). The same pattern was present in our February collection, but I wasn't as sure of the accuracy of our count because it was harder to tell males from females from lack of gonadal development. We were talking about whether or not we somehow discriminated against males while seining for them. I know that the net's mesh is fine enough so that only fish smaller than about 15 mm could possibly slip through, and adult telescopes are at least 30 mm long in our experience. We also didn't throw back any fish and thus possibly discriminate against smaller males, because we were having a hard enough time catching fish that we kept all that we caught. So it may be a property of at least this population of telescope shiners in Hurricane Creek that there is a significant skew in the M:F ratio. I can't tell you what this means, or if it's adaptive in some fashion; but I hope further evidence leads to some working hypothesis as to what the hell's going on with this population (or is it a species-wide phenomenon?).
I sacrificed two scarlet shiners that I've kept in an aquarium since last August. One of them was brilliantly colored, and had tubercles on his head. Currently they're in a freezer. Next week we hope to extract carotenoid pigments from them and look for any relationship between carotenoid concentration and sexual display (coloration). Carotenoid pigments are the basis of red/orange color in many fishes, and in principle an alpha scarlet shiner that's very red should have a lot of carotenoids in its body. Carotenoids are also part of an animal's anti-oxidation mechanism, as is Vitamin E, for instance. Our protocol for extracting carotenoids will involve grinding up the whole body, rather than merely a surface extraction. So we'll get the whole count, hopefully. As usual, if I knew what was going to happen it wouldn't be an experiment, so we'll see.
I was just listening to a really grungy swamp-rock version of the song "John the Revelator" on WWOZ out of Nawlins. Somehow it was the perfect soundtrack for writing this entry. Now it's cut to an even swampier version of "If You Walk With Jesus" sung by a guy who sounds like Tom Waites. Well, I guess that's why I listen to the station. . . . .