Responses of bay anchovy (Anchoa mitchilli) larvae under lethal and sublethal scenarios of crude oil exposure Tara A. Duffy a,n , William Childress a,b , Ralph Portier c , Edward J. Chesney a a Louisiana Universities Marine Consortium, 8124 Hwy 56, Chauvin, LA 70344, USA b Aquatic Germplasm and Genetic Resources Center, Department of Renewable Natural Resources, Louisiana State University Agricultural Center, 2288 Gourrier Ave, Baton Rouge, LA 70802, USA c Louisiana State University, Department of Environmental Sciences, Baton Rouge, LA, USA article info Article history: Received 4 December 2015 Received in revised form 12 July 2016 Accepted 19 August 2016 Available online 16 September 2016 Keywords: Bay anchovy HEWAF CEWAF Mortality Growth Development abstract Bay anchovy (Anchoa mitchilli) is an ecologically important zooplanktivorous fish inhabiting estuaries of the Gulf of Mexico and eastern North America from Maine to Florida. Because they have a protracted spawning season (spring through fall) and are abundant at all life stages in coastal estuaries, their eggs and larvae likely encountered oil that reached the coast during the Deepwater Horizon oil spill. We compared responses to oil exposure at different life stages and at lethal and sublethal conditions using acute, 24 h exposures. In a series of experiments, bay anchovy larvae were exposed to high energy water accommodated fractions (HEWAF) and chemically-enhanced WAF (CEWAF) at two stages of larval de- velopment (5 and 21 days post hatch, dph). HEWAF oil exposures induced significantly greater life stage dependent sensitivity at 5 dph than at 21 dph but chemically dispersed (CEWAF) exposure mortality was more variable and LC 50s were not significantly different between 5 and 21dph larvae. Acute exposure to two low-level concentrations of CEWAF did not result in significant mortality over 24 h, but resulted in a 25–77% reduction in larval survival and a 12–34% reduction in weight specific growth after six days of post-exposure growth following the initial 24 h exposure. These results show that younger (5 dph) bay anchovy larvae are more vulnerable to acute oil exposure than older (21 dph) larvae, and that acute responses do not accurately reflect potential population level mortality and impacts to growth and de- velopment. & 2016 Elsevier Inc. All rights reserved. 1. Introduction Bay anchovy, Anchoa mitchilli, is one of the most abundant species of fish in coastal bays and inlets from Maine to south Florida and the Gulf of Mexico (Hildebrand and Schroeder, 1928; Sheridan, 1978). Bay anchovy embryos and larvae typically dom- inate the ichthyoplankton catches in estuarine collections during the summer, while adults dominate trawl surveys in Gulf estuaries (Dovel, 1971; Flores-Coto et al., 1983; Olney, 1983; Houde and Al- pern-Lovdal, 1984; Chesney and Baltz, 2001). Because of its small size at maturity (30–40 mm), serial spawning strategy, and rapid larval growth rate (0.5 mm d 1 ), bay anchovy have tremendous potential as an important secondary producer and trophic link as a forage fish in estuarine habitats (Luo and Brandt, 1993). Their planktivorous feeding strategy continues into the juvenile and adult stages, making bay anchovy and other closely related engraulids important links for energy flow in estuarine systems of the Gulf of Mexico and southeastern Atlantic Ocean (Detwyler and Houde, 1970; Sheridan, 1978; Livingston, 1982; Houde and Alpern- Lovdal, 1984, 1985; Rakocinski et al., 1992). During the 2010 Deepwater Horizon (DWH) oil spill, significant amounts of oil reached coastal estuaries of the northern Gulf of Mexico (Silliman et al., 2012). Because bay anchovy is native to the Gulf of Mexico, and has abundant early life history stages in sur- face waters, it is likely that significant numbers of this species were exposed to crude oil at all life stages. Understanding the impacts of this oil spill on bay anchovy may help estimate po- tential damage to food webs and susceptibility of this ecologically important species to crude oil exposure during early life stages. Bay anchovy is also representative of the many other anchovy species that occur in the Gulf of Mexico (Robinette, 1983). Rapid growth and development in early stages of this species suggest it may be a sensitive sentinel for oil exposure in other fish species with rapid larval development ( o48 h) and are native to the Gulf of Mexico. Evaluating oil sensitivity in an ecologically important species that, to our knowledge, had never previously been used for toxicological studies may provide new insight into how this Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/ecoenv Ecotoxicology and Environmental Safety http://dx.doi.org/10.1016/j.ecoenv.2016.08.010 0147-6513/& 2016 Elsevier Inc. All rights reserved. n Corresponding author. Current address: Northeastern University, Department of Marine and Environmental Sciences,14 Holmes Hall, Boston, MA 02115, USA. E-mail address: t.duffy@neu.edu (T.A. Duffy). Ecotoxicology and Environmental Safety 134 (2016) 264–272