Anticoagulant rodenticides (ARs) areused in rateradication eﬀorts on island wildlife refuges. ARbait pellets can get into coralreefareasduring broadcasting and leadto exposure ofnon-target organisms, such as marine ﬁshes. The objective of this study was to determine the sensitivity of representative saltwater ﬁshes, Red-toothed triggerﬁsh (Odonus niger) and Black triggerﬁsh (Melichthys niger), and common freshwater ﬁshes, fathead minnow (Pimephales promelas), and largemouth bass (Micropterus salmoides) to ﬁrst generation ARs, diphacinone (DPN) and chlorophacinone (CPN), as well as a second-generation AR, brodifacoum (BROD). Acute toxicity of ARs was evaluated by single dose, intraperitoneal injections. The median lethal dose (LD50) ranges were 137−175μg DPN/g, 155−182μg CPN/g, and 36−48μg BROD/g for Red-toothed triggerﬁsh and 90−122μg DPN/g, 125−164μg CPN/g, and 50−75μg BROD/g for black triggerﬁsh. Laboratory surrogate test ﬁsh species fathead minnow and largemouth bass were of similar sensitivity toward AR-induced toxicity compared to triggerﬁsh based on LD50 values. Sublethal eﬀects on elevated clotting time occurred in dose-dependent fashion in all ﬁsh tested. Fish appear to have low sensitivity to AR chemicals as compared to other taxa, in particular mammals and birds, based on across-taxa comparisons of species sensitivity distributions of whole body, single dose acute lethality (LD50 values). The sensitivity of ﬁsh to waterborne exposures of ARs has yet to be fully evaluated and indeed may prove more hazardous to ﬁsh.