Mercury effects on predator avoidance behavior of a forage fish, golden shiner (Notemigonus crysoleucas)

Abstract

Mercury contamination of fish is widespread in North America and has resulted in the establishment of fish consumption advisories to protect human health. However, the effects of mercury exposure to fish have seldom been investigated. We examined the effects of dietary mercury exposure at environmental levels in a common forage species, golden shiner (Notemigonus crysoleucas). Fish were fed either an unaltered diet (12 ng/g wet wt methylmercury [MeHg] as Hg), a low-Hg diet (455 ng/g Hg), or a high-Hg diet (959 ng/g Hg). After 90 d mean fish whole-body total Hg concentrations were 41, 230, and 518 ng/g wet wt, respectively, which were within the range of concentrations found in this species in northern U.S. lakes. There were no mortalities or differences in growth rate among groups. Groups of fish from each treatment were exposed to a model avian predator and their behavioral response videotaped for analysis. Brain acetylcholinesterase (AChE) activity was determined in fish after behavioral testing. Fish fed the high-Hg diet had significantly greater shoal vertical dispersal following predator exposure, took longer to return to pre-exposure activity level, and had greater shoal area after return to pre-exposure activity than did the other treatments, all of which would increase vulnerability of the fish to predation. There were no differences in brain AChE among treatments. We conclude that mercury exposure at levels currently occurring in northern United States lakes alters fish predator-avoidance behavior in a manner that may increase vulnerability to predation. This finding has significant implications for food chain transfer of Hg and Hg exposure of fish predators.

Mercury Bioaccumulation in Northern Two-lined Salamanders from Streams in the Northeastern United States

“…Although obvious lethargy was not noted for salamanders from any other stream location during the investigation, effects from contaminants, including mercury, on biota may be extremely subtle and difficult to detect (Webber and Haines, 2003). Other researchers have observed negative effects of both nitrate (Rouse et al, 1999) and aluminum (Clark and Hall, 1985;Clark and LaZerte, 1985) on palustrine amphibian species at levels comparable to or lower than the nitrate and aluminum water concentrations (Table 1) recorded at the BBWM ammonium sulfate treatment stream (WBB), however it is unknown which chemical attributes or interactions were primarily responsible for causing lethargy in these individuals.…”

Adverse effects from environmental mercury loads on breeding common loons

“…Prey item Hg levels that are correlated with reductions of 40% and 41% in fledging success are 0.16 ug/g (ww) (Evers et al 2004) and 0.17 ug/g (ww), respectively (Burgess and Meyer, this issue). Prey fish behavior may also succumb to elevated Hg levels; studies have found cyprinnids with 0.52 ug Hg/g (whole body, ww) to school erratically (Webber and Haines 2003), which could lead to lethargic loons disproportionally selecting fish that exhibit inhibited predator-avoidance behaviors.…”

Mercury Contamination of Biota from Acadia National Park, Maine: A Review

“…Although there have been many recent advances in evaluating Hg exposure and its toxicological effects on aquatic biota (Pickhardt, Folt, Chen, Klaue, & Blum, 2002;Webber & Haines, 2003), many questions remain unanswered. Weiner et al (2003) concluded that there has been little progress in addressing toxicological effects of Hg contamination on biota, compared to scientific advances in identifying environmental and biogeochemical factors influencing Hg bioavailability and biotic exposure to MeHg.…”

“…Acidified freshwater ecosystems in the northeastern United States with high temperatures and dissolved organic carbon levels facilitate MeHg bioaccumulation and biomagnification (Gilmour & Henry, 1991;Weiner et al, 2003 and references therein). High concentrations of Hg in aquatic biota have the potential for sub-lethal effects (i.e., reduced foraging and inability to avoid predators; Webber & Haines, 2003) that may negatively influence population dynamics (Evers, Lane, & Savoy, 2003a). The effects of MeHg on biota can be detrimental and include reduced reproduction and development, lower productivity and growth, aberrant behavior, and death (Thompson, 1996;Weiner et al, 2003).…”