Monitoring of fish community in the recipient of a greenfield pulp mill at River Uruguay during 2007-2010

摘要

A new Greenfield kraft mill started its operation in Uruguay in November 2007. The mill uses the latest pulp processing technology and is also the first modern kraft mill in Uruguay discharging the treated effluent to River Uruguay. As part of the environmental impact assessment process the mill started baseline studies on water quality, river biology and fish studies in the future recipient and reference areas two years prior to the start up. The studies have continued as monitoring studies. The abundance, biomass and species richness of the fish community as well as the condition and exposure state of fish have been studied. The task has been a serious challenge because there are more than 150 fish species in Uruguay River basin and very little is known about their life history. This is the first time in River Uruguay when regular fish monitoring studies have been performed at the same sites and using the same method. These monitoring studies have also given the opportunity to study the effects of the pulp mill effluents on fish community and to compare the results to baseline studies prior to mill start up. The studies have been performed two times per year in April and December using Nordic standard gill net series in two recipient areas and one reference area. Baseline studies indicated that the best species as an indicator species would be Bagre trompudo (Iheringichthys labrosus) because of its feeding character, number and size classes in test fishing catches and expected locality in distribution. The liver and gonad somatic indexes, condition factor and exposure state of this species have been included in the monitoring studies. This paper presents the fish studies of a three year monitoring period and the comparison to the situation prior to mill operation. The availability of the chosen indicator species will be also discussed in the paper.