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.)