Spotted Seatrout Reproductive Biology Impacted By the Deepwater Horizon Oil Spill

The April 2010 Deepwater Horizon oil spill impacted shoreline marshes and estuaries in the northern Gulf of Mexico (GOM).  Spotted seatrout (Cynoscion nebulosus) are an estuarine resident, spring-summer spawning species in the GOM; thus, both adult and young-of-the-year fish were potentially exposed to oiled waters during 2010.  We compared historical data on reproductive parameters of spotted seatrout from Barataria Bay Louisiana (1995 data) and the Mississippi Gulf coast (1999 data) to data collected from the same locations one year post-spill (2011).  The Gonadosomatic Index of females from both areas was significantly lower in 2011 than pre-spill values. In 2011, delayed ovarian development and a lower percentage of fish in the actively spawning sub-phase were seen in Mississippi, and a higher percentage of non-reproductive fish was seen in Louisiana compared to pre-spill data. The prevalence of atretic vitellogenic oocytes was significantly higher in Mississippi and Louisiana fish in 2011, and spawning frequency was significantly reduced from every 4-5 days to every 13-38 days post-spill in both areas.  These results indicate that relatively short-term, low level exposure to oiled waters can significantly impair fish reproductive parameters a year after the oil spill, which has population-level implications for many GOM fish species.