Assessing the toxicity of lead from recreational fishing gear to Daphnia magna

The presence of lead (Pb) sinkers and jigs lost to waterbodies from recreational fishing serves as a potential risk to aquatic ecosystem health. Assessing the toxicity of Pb released from fishing gear poses several challenges, and one proposed approach is to use Pb salts as a surrogate. However, it remains unclear how the toxicity of Pb salts compares with that of Pb derived directly from fishing gear. To test this, we measured Pb release from different concentrations of fishing sinkers (e.g., bell sinkers and split shot sinkers) at 4 and 30 °C for 48 hr. Furthermore, we compared the overt toxicity of Pb sinkers and jigs against Pb nitrate, Pb(NO3)2, toxicity using Daphnia magna. Water accommodated fractions were generated by suspending Pb sinkers (100 g/L) in water for 48 hr, which caused Pb dissolution exceeding water quality guidelines by ∼35 to 100 times, with additional impurities of zinc and cadmium in the split shot and bell sinkers, as well as iron, arsenic, nickel, and copper in the bell sinkers. These sinker types were not acutely toxic to D. magna; however, chronic exposure to water accommodated fractions released from both types of sinkers significantly affected reproduction (number of neonates produced over 21 days per D. magna) and growth. Therefore, discarded fishing gear may represent a notable source of environmental Pb as well as other metals. This study offers valuable baseline data to support future discussions on regulating Pb-based fishing gear in Canada and highlights the importance of developing cost-effective alternatives.