An Injectable, Slow-Release Implantation Method for Exposing Fish to Chemicals over a Period of Weeks

Abstract A slow-release, injectable implant method was developed for administering test chemicals to cunners Tautogolabrus adspersus. The implant is composed of a matrix of a test chemical homogenized in a mixture of Ethocel (Dow Chemical) and coconut oil. The effectiveness of a subcutaneous implant of this matrix in vivo was determined by tracing plasma concentrations of three separate chemicals (estradiol, ethynylestradiol, and atrazine) over time in treated male cunners. Release from the implant was determined based on the percentage of the implanted concentration of test chemical (plus metabolites) that was detected in fish plasma over a 1–2-week period after implantation. Circulating estrogen concentrations measured in plasma from two different cunners that received the estradiol implant were almost identical, indicating that there is a reasonably even distribution of test chemical within the Ethocel–coconut oil preparation and that individual variability may be minimal for release of test chemical f...