The title of my research project is “The Reproductive Biology of Eleotris Sandwicensis.” As you can probably guess from the title, I am interested in elucidating the reproductive biology of this endemic O‘opu. What exactly does this mean, and why would I want to do it? First of all, basically nothing is known about the reproductive biology of this species. We have no idea when it spawns, how many times it spawns, how large a fish has to be in order to spawn, how many eggs a female is capable of producing. This type of information is vital to resource managers and policy makers because it helps them to understand how to best manage populations of this species. Without this type of basic biological information, it is almost impossible to enact policy aimed at protecting these fish. By doing this research, I hope to add another link to the chain of knowledge about O‘opu that is slowly growing in the field of stream biology.
The aim of my study is to learn about reproductive seasonality (at what time of the year are these fish reproductively active?), size at maturation (how big must they get before they reproduce?), spawning frequency (can they spawn more than once in a season?), and fecundity (how many eggs can a female spawn?). I would also like to know if there is a difference in terms of reproductive biology between fish collected from altered/degraded streams and fish collected from pristine streams.
In order to obtain this information, I have been collecting several fish per month from streams on Oahu, Kauai and Hawaii. I take measurements of each fish (length, weight), and dissect the gonads out of each fish. Gonads are preserved and examined using various methods to help me determine things like spawning seasonality, spawning frequency and fecundity. One of these methods is to use histology to microscopically examine the individual gonadal cells. To do this, I embed gonads in paraffin wax and slice them into sections that are thinner than a single hair. I then mount the sections on a slide and stain them to bring out important cellular features that allow me to examine the cells under a light microscope. By doing this, I can determine whether a fish is reproductively mature at the time of capture. I can also tell if a fish has just spawned prior to capture.
I have collected 15 months worth of data. Once my field collections are completed I will continue to work in the lab doing histology and microscopy as well as statistical analysis of the data in order to determine what I have found.