Estrogenicity and intersex in juvenile rainbow trout (Oncorhynchus mykiss) exposed to Pine/Eucalyptus pulp and paper production effluent in Chile.

Pulp and paper mill effluents (PPMEs) have been shown to increase gonad size, cause early maturation, and disrupt hormone functions in native and non-native Chilean fish. In this study, we assessed reproductive (plasma vitellogenin; VTG, gonad development) and metabolic (ethoxyresorufin-O-deethylase activity; EROD) end points, relative liver size (LSI) and condition factor (K) of juvenile female and male rainbow trout exposed to effluents. Unlike previous studies, which have focus either on the specific effects of effluent on fish in laboratory exposures or biotic population statuses downstream of discharge sites, we simultaneously assessed the impacts of PPMES on trout using two approaches: (1) laboratory exposures of tertiary treated PPME produced from processing Eucalyptus globulus or Pinus radiata; and (2) in situ bioassay downstream of the combined discharge of the same pulp mill. Despite an increase in the average gonadosomatic index (GSI) in exposed fish, no statistical differences in gonad size between exposed and unexposed individuals was detected. However, both female and male fish exposed to effluents showed significantly higher concentrations of plasma VTG, so more in fish exposed to Eucalyptus-based effluent when compared to Pinus PPME. In addition, male fish showed intersex characteristics in all exposure assays (Eucaliptus and Pinus) and, despite the low concentration of effluent in the river (<1% [v/v]), similar responses were observed in the caged fish. Finally, EROD activity was induced in both in situ exposures and laboratory assays at the higher PPME concentration (60-85% PPME). This study confirms estrogenic effects in Chilean fish exposed to PPME and the necessity for biological effects monitoring in addition to the assessment of physical-chemical endpoints as required in current government regulations.

Liver ethoxyresorufin-O-deethylase and brain acetylcholinesterase in two freshwater fish species of South America; the effects of seasonal variability on study design for biomonitoring.

Responses at low levels of biological organization to evaluate environmental changes and water quality have been used for many years. South America is no different, and recently biochemical endpoints in fish have been used to assess the impacts of industrial and sewage effluents on wild fish populations. For Chilean native freshwater fish, basic biological data is scarce and data on 7-ethoxyresorufin-O-deethylase (EROD) and Acetylcholinesterase (AChE) activity is practically absent. Moreover, extensive variation in these two biochemical endpoints exists among species and seasons. In this article we evaluate seasonal variation in liver EROD and brain AChE activities in Trichomycterus areolatus and Percilia gillissi, two widely distributed native freshwater fish species in central Chile. We observed a marked seasonality in hepatic EROD activity in both species, with maximums for P. gillissi during winter months and sex differences in February, July, August and December. T. areolatus showed no sex differences, and peaks in EROD activity in the middle of summer, winter and late spring. Species differences in EROD activity were observed with activity being 1-2 orders of magnitude higher in P. gillissi compared to T. areolatus. Scarce seasonal variation and no sex related differences in brain AChE for both species were observed. Multivariate analysis (PCA) indicated that physical water quality parameters had some degree of responsibility for the seasonal responses found. The seasonal variability data of these biochemical endpoints were used to optimize study design for future monitoring programs, planning timing of sampling, increasing statistical power by collecting specific sample sizes required.

Application of artificial photoperiod in fish: a factor that increases susceptibility to infectious diseases?

This paper describes and evaluates the mortality associated with the potential stressor effect induced by application of artificial photoperiods in rainbow trout (Oncorhynchus mykiss). After application of artificial photoperiods, high mortalities of trout subjected to this management were recorded (36% in LD 14:10 and 25% in LD 24:0) as compared to controls (7%). The recorded signology related to diseased trout included darkening, lethargy and erratic swimming. Among the morphological changes, skin lesions and ulcerative-type necrosis could be observed. Blood tests, histopathology and isolation of pathogens identified as Flavobacterium psychrophilum, associated with Aeromonas, Pseudomonas and Saprolegnia sp., were performed. The application of artificial photoperiods suggests that fish may be more susceptible to opportunistic diseases; thus, it is advisable to emphasize preventive measures in fish subjected to this management.