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Reproductive biology is a necessary element for the management of elasmobranch fisheries. Traditionally, characterization of elasmobranch reproduction has involved lethal sampling to examine gross reproductive structures and development of embryos. However, this method is counterproductive to the conservation of shark populations. One non-lethal alternative is the measurement of serum hormones, which often vary according to reproductive events. Radioimmunoassay (RIA) has been used to measure hormone concentrations in reproductive endocrinology, but can be problematic for researchers. Alternatively, chemiluminescence immunoassays (CLIA) are routinely used for measuring circulating hormone concentrations in low-volume, non-extracted human serum samples. However these assays have not been previously examined for use with elasmobranch blood. In the first component of this study, I examined whether CLIA was a suitable alternative for detecting seasonal profiles of these hormones in the bonnethead, Sphyrna tiburo. This was accomplished by collecting serum from sexually mature male (n = 35) and female (n = 32) bonnetheads , measuring reproductive organs for maturity and reproductive stage, and measuring concentrations of testosterone (T) in males, and 17β-estradiol (E2) and progesterone (P4) in females using RIA and CLIA. CLIA was successfully validated for use with shark serum by assessing parallelism and spike recovery. CLIA-derived measurements were significantly correlated with those obtained with RIA (r = 0.809, 0.773, and 0.908 for T, E2, and P4, respectively; p