Fish collected from the receiving areas of 12 Canadian pulp mills were examined, including sites receiving effluent from kraft mills using chlorine as well as sulfite mills. Field collections included sampling of receiving water for chemistry and toxicity testing, and sampling of local fish for organ weights, hepatic MFO (ethoxyresorufin‐O‐deethylase, EROD) activity, plasma steroid levels, and levels of liver dioxins. The main objectives of this study were to determine whether the discharge of effluent from pulp mills to sites other than Jackfish Bay was associated with physiological or biochemical disruptions in wild fish, whether there was any correlation between waste treatment and the presence of biological responses in wild fish, and whether there was any association between the use of chlorine as a bleaching agent and these responses. Although white sucker collected near bleached‐kraft mills exhibited the highest EROD induction and dioxin levels, elevated enzyme activity was observed in fish from sites that did not use chlorine, and depressions in plasma sex steroid levels was not correlated with the level of EROD activity. The absence of chlorine bleaching or the presence of secondary treatment did not eliminate responses in fish, including decreased circulating levels of sex steroids, decreased gonadal size, and increased liver size. This survey has shown that (a) induction of hepatic EROD enzymes and depressions of plasma sex steroid levels during gonadal growth are found downstream of several pulp mills; (b) these changes are seen at some mills without chlorine bleaching and at mills that have secondary treatment; (c) substantial dilutions of nontoxic effluent do not appear to remove these responses; (d) the dominant factor determining the presence or absence of responses appeared to be dilution level; and (e) lab toxicity tests on invertebrates, rainbow trout, and fathead minnows could not predict the presence of these responses in wild fish.

Abstract-For the last 20 years, studies conducted in North America, Scandinavia, and New Zealand have shown that pulp and paper mill effluents affect fish reproduction. Despite the level of effort applied, few leads are available regarding the factors responsible. Effluents affect reproduction in multiple fish species, as evidenced by decreased gonad size, decreased circulating and gonadal production of reproductive steroids, altered expression of secondary sex characteristics, and decreased egg production. Several studies also have shown that effluent constituents are capable of accumulating in fish and binding to sex steroid receptors/ binding proteins. Studies aimed at isolating biologically active substances within the pulping and papermaking process have provided clues about their source, and work has progressed in identifying opportunities for in-mill treatment technologies. Following comparisons of manufacturing processes and fish responses before and after process changes, it can be concluded that effluent from all types of mill processes are capable of affecting fish reproduction and that any improvements could not be attributed to a specific process modification (because mills normally performed multiple modifications simultaneously). Improved reproductive performance in fish generally was associated with reduced use of molecular chlorine, improved condensate handling, and liquor spill control. Effluent biotreatment has been effective in reducing some effects, but biotreated effluents also have shown no difference or an exacerbation of effects. The role of biotreatment in relation to effects on fish reproduction remains unclear and needs to be resolved.

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BackgroundMany postglacial lakes contain fish species with distinct ecomorphs. Similar evolutionary scenarios might be acting on evolutionarily young fish communities in lakes of remote islands. One process that drives diversification in island freshwater fish species is the colonization of depauperate freshwater environments by diadromous (migratory) taxa, which secondarily lose their migratory behaviour. The loss of migration limits dispersal and gene flow between distant populations, and, therefore, is expected to facilitate local morphological and genetic differentiation. To date, most studies have focused on interspecific relationships among migratory species and their non-migratory sister taxa. We hypothesize that the loss of migration facilitates intraspecific morphological, behavioural, and genetic differentiation between migratory and non-migratory populations of facultatively diadromous taxa, and, hence, incipient speciation of island freshwater fish species.ResultsMicrochemical analyses of otolith isotopes (88Sr, 137Ba and 43Ca) differentiated migratory and non-migratory stocks of the New Zealand endemic Gobiomorphus cotidianus McDowall (Eleotridae). Samples were taken from two rivers, one lake and two geographically-separated outgroup locations. Meristic analyses of oculoscapular lateral line canals documented a gradual reduction of these structures in the non-migratory populations. Amplified fragment length polymorphism (AFLP) fingerprints revealed considerable genetic isolation between migratory and non-migratory populations. Temporal differences in reproductive timing (migratory = winter spawners, non-migratory = summer spawners; as inferred from gonadosomatic indices) provide a prezygotic reproductive isolation mechanism between the two ecotypes.ConclusionThis study provides a holistic look at the role of diadromy in incipient speciation of island freshwater fish species. All four analytical approaches (otolith microchemistry, morphology, spawning timing, population genetics) yield congruent results, and provide clear and independent evidence for the existence of distinct migratory and non-migratory ecotypes within a river in a geographically confined range. The morphological changes within the non-migratory populations parallel interspecific patterns observed in all non-migratory New Zealand endemic Gobiomorphus species and other derived gobiid taxa, a pattern suggesting parallel evolution. This study indicates, for the first time, that distinct ecotypes of island freshwater fish species may be formed as a consequence of loss of migration and subsequent diversification. Therefore, if reproductive isolation persists, these processes may provide a mechanism to facilitate speciation.

The acute lethality of low dissolved oxygen (DO) was examined in laboratory studies using several New Zealand freshwater fish and two invertebrates at 15°C. The 48-h LC50 value was used as the endpoint for acute DO sensitivity as, owing to rapid mortality, this was found to best approximate the threshold lethal concentration. Median lethal time to death did not provide a reliable endpoint for comparing sensitivities. Fish LC 50 values varied from 0.54 to 2.65 mg litre -1 , with inanga whitebait (Galaxias maculatus; 2.65 ± 0.19 mg litre -1 , mean + SEM) being the most sensitive species tested. Common smelt (Retropinna retropinna; 1.83 ± 0.08 mg litre -1 ) and rainbow trout (Oncorhynchus mykiss; 1.61 ± 0.06 mg litre -1 ) were similar in their sensitivities, whereas common bully (Gobiomorphus cotidianus; 0.91 ± 0.06 mg litre -1 ) and shortfin eel elvers (Anguilla australis; 0.54 ± 0.03 mg litre -1 ) were the most tolerant fish. The shrimp (Paratya curvirostris; 0.82 ± 0.09 mg litre -1 ) and freshwater crayfish (Koura, Paranephrops planifrons; 0.77 ± 0.06 mg litre -1 ) were also tolerant to low DO. A subset of experiments to determine the relative M05001;

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Abstract-Northern leopard frogs (Rana pipiens) and green frogs (Rana clamitans) were evaluated at eight wetland sites, four of which were within apple orchards, to determine if environmental changes associated with orchard management affected measured biological parameters. Size, age, genetic variation, condition indices, levels of circulating steroid hormones, 7-ethoxyresorufin-Odeethylase activity (EROD), and organochlorine and organophosphorus residues in breeding males sampled at pond sites in orchards were compared to the same parameters measured in breeding males from reference sites. Also, the size and physiological condition of young-of-the-year captured in orchard and reference ponds were compared. No evidence of a reduction in genetic variation was found in populations of either species at any sites, but unexpectedly high average heterozygosity values (0.191-0.282) in concert with low overall fixation indices (0.012-0.059) in adults of both species did suggest that pond populations were interacting with neighboring populations in nonorchard habitats. Few significant differences in levels of circulating steroid hormones or condition indices of breeding males were found among sites. Significant EROD induction in male green frogs collected from one orchard site during one sampling event was the only indication that a metabolic challenge due to presence of cytochrome P450-inducing toxicants may have existed, whereas elevated concentrations of organochlorines (dichlorodiphenyltrichloroethane [DDT]-or endosulfan-related) in green frog tissues suggested that frogs at three orchard sites were taking up pesticides. Significant differences in size of equivalent-age male and juvenile leopard frogs and green frogs occupying different study sites suggested that suboptimal habitat characteristics existed at one or two of the four orchard sites. However, site-specific habitat deficiencies could not be related to orchard study sites in general, and, thus, wetlands in apple orchards appeared to provide viable breeding habitat for both northern leopard frogs and green frogs.