A synthesis of water quality and contaminants data for the atlantic menhaden,brevoortia tyrannus: Implications for chesapeake bay

Abstract

Abstract Limited data are available on the effects of water quality and contaminant conditions on Atlantic menhaden, but data measuring the effects of temperature, salinity, temperature‐salinity interactions and dissolved oxygen are available forvarious life stages. Temperatures below5 °C and above 33 °C are lethal to larvae and juveniles but juvenile Atlantic menhaden demonstrate the ability to avoid high, potentially lethal temperatures in laboratory studies. Adult Atlantic menhaden prefer higher temperatures than juveniles. Juveniles demonstrate the ability to survive large shifts in salinity (i.e., changes of 31.5 ppt). Lethal dissolved oxygen (D.O.) concentrations of 1.1 mg/L are also reported for juvenile Atlantic menhaden. These hypoxic D.O. conditions can be found in the bottom waters of mainstem areas of Chesapeake Bay. Fortunately, this species usually inhabits the surface waters where D.O. conditions are higher. Toxicity data are available for Atlantic menhaden exposed to six single chemicals. Most of these studies were designed to evaluate the effects of biocides (primarily chlorine) and/or other interacting conditions such as increased temperature on the survival at various life stages of Atlantic menhaden. The toxicity of only one chemical (chlorine) has been evaluated with Atlantic menhaden larvae. Free residual chlorine (FRC) concentrations of 0.5 mg/L or more are toxic to larvae; a 10 °C thermal increase added simultaneously with this chlorine concentration is also lethal. Chlorine toxicity data with juvenile Atlantic menhaden are more numerous. Ninety‐six hour LC50's of 0.18 and 0.15 mg/L were reported at test temperatures of 15 and 25 °C respectively. Both of these toxic concentrations were much higher than the U.S. Environmental Protection Agency's (U.S. EPA's) acute and chronic water quality criteria for chlorine. Therefore, it appears that the chlorine criteria would be protective of this life stage. Moreover, juveniles were reported to avoid approximately half of the acute LC50's for chlorine. This strongly schooling species was reported to have better avoidance capabilities when tested in groups than when tested individually. Dechlorination practices are important for reducing potentially toxic effects of chlorine on juvenile Atlantic menhaden. Environmentally realistic concentrations of excess sulfite often associated with dechlorination would likely be either nontoxic or avoided if potentially toxic conditions existed. Also, juveniles generally avoided lower sulfite concentrations at higher temperatures. The toxicity of tributyltin (TBT) to juvenile Atlantic menhaden was evaluated in three studies: an acute toxicity study, an avoidance study, and a subchronic toxicity study. A TBT concentration of 4.5 μg/L was acutely toxic; concentrations approximately three times this value were avoided by menhaden at this life stage. Concentrations of TBT realistic in marina areas of Chesapeake Bay (for example, 0.093 and 0.490 μg/L) were reported to have no adverse effects on juveniles in 28 day sub‐chronic studies. Populations of Atlantic menhaden have remained stable in Chesapeake Bay in recent years. Despite the success of this fish, information on adverse water quality and contaminant effects may be useful. These data may be very important for managing the species or establishing protective water quality or contaminant regulations or standards. The following research is proposed with Atlantic menhaden: micro‐layer toxicity studies with eggs; standard acute and chronic single chemical or multiple chemical toxicity studies with early life stages; behavioral toxicity studies with juveniles using schooling behavior as an endpoint and in situ and on‐site ambient toxicity studies designed to determine not only survival, but histopathological, histochemical, behavioral and physiological effects.