Telescope Shiners Get Fatter As The Spring Goes On...

We've done much of the first round of processing the telescope shiners we collected last Saturday at the Walls of Jericho. This gives us three months of length and weight data, back to February. I took the opportunity to run ANOVAs with the length and weight data (males and females combined) to determine if there are significant differences between months. These tests show no significant difference between the length of fish from the three months, with the mean bouncing around 45 mm for each month. But the weight showed an interesting pattern. Average mass has increased from month to month, especially from February to March. The February cohort is significantly different from March at the .05 level, and February is different from April at the .01 level. But March and February are not significantly different. My working hypothesis is that average mass will peak in July, but I'm not sure what level of statistical significance will appear when warm-season months are compared.

We eviscerated all 39 fish in the April collection yesterday. I don't have GSI values yet but many of the ovaries are large and nearly mature; oocytes are yellow with yolk, and something like 1 mm+ in diameter. This Friday we'll sit down and characterize the maturation status of ovaries, and begin to count eggs per fish. I came across one interesting way to characterize a fish's fecundity today on the NANFA Forum: once eggs are counted, calculate the ratio of eggs per gram of fish's body mass. Of course, since the biggest shiner we've collected weighs just over 4 grams, maybe we should transform that ratio to eggs per mg of mass. But I'll keep you posted.