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(18-65) Pulp mill effluent affects growth, sex characteristics and reproduction of fathead minnows. Parrott, Joanne*,1, Wood, Craig2, Boutot, Peter2, Blunt, Beverly1, Baker, Mark1, Dunn, Susan3, 1 National Water Research Institute, Burlington, Ontario, Canada2 Noranda Technology Centre, Pointe Claire, Quebec, Canada3 Fraser Paper Inc., Edmundston, New Brunswick, Canada ABSTRACT- During Environmental Effects Monitoring studies, wild fish collected downstream of Nexfor Edmundston bleached sulphite mill (BSM) had reduced gonad size and fecundity. To assess BSM final effluent, long-term growth and reproduction tests were carried out in a flow-through bioassay trailer at the mill secondary treatment lagoons. Fertilized fathead minnow eggs were exposed to 0, 1, 3.2, 10, 32, 50 and 100 % final effluent (or ethinylestradiol, EE2 10 ng/L as a positive control). Effluent (10 to 50 %) caused a significant increase in the growth of fish at 30, 60 and 125 days post-hatch. Changes in external sex characteristics, such as ovipositor index, were seen at 60 days post-hatch in EE2 and in 32 and 48 % effluent. Liver-somatic indices were increased in fish exposed to EE2 and effluent concentrations 32 % and higher. At 125 days, some male fish had ovipositors in effluent concentrations as low as 10 %. Higher effluent concentrations (32-100%) resulted in a majority of fish that looked externally like females. Egg production began about 70 days post-hatch. Fish exposed to 0 to 3.2 % effluent produced eggs (in total about 2000 per treatment), while fish in 10 % effluent produced only 250 eggs. Fish in higher effluent concentrations (32% to 100 %) produced no eggs, despite significantly increased weight, length and condition factors in males and females. This finding is consistent with wild fish exposed to pulp mill effluents, that often have increased size-at-age and condition factors, but smaller gonads, compared to reference fish. Key words: pulp mill effluent, fathead minnow, lifecycle, reproduction |
