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The common bully (Gobiomorphus cotidianus) was used as a bioindicator to assess the impacts of geothermal, bleached kraft mill effluent (BKME), sewage, and thermal discharges in the Waikato River, Northern New Zealand. A range of morphological and physiological parameters were measured to assess fitness in fish sampled upstream and downstream from these point sources. Isotopic signatures gave evidence that fish were resident at sites and showed a gradient corresponding to site-specific sources of carbon and nitrogen along the river. There were changes in the size range and age structure of the populations but, no physiological responses were detected. Limited impacts were observed on common bully health at individual discharge sites, or downstream where the river showed gradual deterioration in water quality, particularly nutrient enrichment, and increased turbidity. Despite the gradual deterioration in water quality no concomitant cumulative impacts were observed in common bully. Responses were largely local in nature, responding to point-source discharges. Population responses at the geothermal and BKME discharge sites warrant further study to investigate possible effects on fish recruitment.

A data-driven model based on an adaptive neuro-fuzzy inference system (ANFIS) was tested for the estimation of suspended sediment concentrations within watersheds influenced by agriculture. ANFIS models were developed using different combinations of inputs such as precipitation, streamflow, surface runoff and the watershed vulnerability index. A multi-watershed ANFIS model was also developed combining the datasets from all studied watersheds. The best results were obtained from a combination of precipitation, streamflow and watershed vulnerability index as input variables. Nash-Sutcliffe coefficients were improved for the multi-watershed ANFIS compared to watershed-specific ANFIS models. The introduction of the erosion vulnerability index significantly improved the ability of the ANFIS model to estimate suspended sediment concentrations within the watersheds. Furthermore, the inclusion of this index opens the possibility of using the ANFIS model to investigate the impact of land-use changes on sediment delivery.

A long-term monitoring study was conducted on effluents from a bleached kraft pulp and paper mill located in Eastern Canada. The study was designed to gain insights into temporal effluent variability with respect to fish reproduction as it related to production upsets, mill restarts and conditions affecting biological treatment performance. Final effluent quality was monitored between February 2007 and May 2009 using biochemical and chemical oxygen demand, total suspended solids, resin and fatty acids, a gas chromatographic profiling index, and the presence of methyl substituted 2-cyclopentenones. Selected effluent samples were evaluated for effects on fish reproduction (egg production) using a shortened version of the adult fathead minnow reproductive test. The events relating to negative effects on fish reproduction were upsets of the pulping liquor recovery system resulting in black liquor losses, operational upsets of the hardwood line resulting in the loss of oxygen delignification filtrates, and conditions that reduced the performance of biological treatment (e.g., mill shutdown and low ambient temperatures). The reductions in egg production observed in fathead minnow were associated with biochemical oxygen demand values > 20 mg/L, GC profiling indices > 1.2 and the presence of methyl-substituted 2-cyclopentenones at concentrations > 100 μg/L. This study demonstrated the importance of both in-plant measures for controlling the loss of organics as well as the optimum operation of biological effluent treatment for eliminating effluent-related effects on fish reproduction (egg production) in the laboratory.

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 approxi- mate the threshold lethal concentration. Median le- thal time to death did not provide a reliable endpoint for comparing sensitivities. Fish LC50 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 sensi- tivities, 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 sensitivities of larval and juvenile trout and bully in- dicated no significant differences between these life stages. Keywords dissolved oxygen; fish; freshwater; hypoxia; Anguilla australis; Gobiomorphus cotidianus; Retropinna retropinna; Paratya curvirostris; Paranephrops planifrons; Oncorhynchus mykiss; Galaxias maculatus

The acute and chronic effects of secondary-treated effluent from a New Zealand pulp and paper mill were assessed using both long-term adult and early life stage (ELS) laboratory exposures of rainbow trout. The relative impact of maternal exposure versus ELS exposure was assessed by a comparison of directly exposed eggs and larvae with the eggs and larvae of exposed adult trout that were reared in reference water. Rainbow trout were exposed to a secondary-treated mixed thermomechanical/bleached kraft mill effluent at a concentration of 15% or to reference water from the egg through to 320-d-old juveniles. The 2 adult rainbow trout exposures were undertaken with nominal concentrations of 10% and 12% treated effluent, respectively. There was no marked effect of water hardening with 15% effluent on fertility or survival of eggs to 16 d. In a subsequent exposure (with hardening in reference water), no significant effects were found on mortality to hatch, time to hatch, length at hatch, mortality to swim-up, mortality to 320 d, or deformity rate at hatch. At experimental termination (320 d), direct-exposed juveniles had smaller livers and reduced condition factor, likely due to differences in food consumption. In 2 subsequent consecutive experiments, exposure of adult trout to 10% and 12% effluent for 2 mo, followed by incubation of the fertilized eggs in reference water, produced no impact on fertility, survival to hatch, survival to swim-up, or length and weight of fry at swim-up. Exposure of adult trout to 12% treated effluent for 8 mo prior to egg fertilization also did not result in differing rates of fertility, mortality to hatch or mortality to swim-up. However, the 8-mo maternal exposure did result in swim-up fry that were significantly shorter and weighed less than the reference swim-up fry. This difference was directly attributable to smaller eggs in the 8-mo-exposed female trout. These results demonstrate that this pulp and paper mill effluent is more likely to elicit indirect impacts on progeny size through chronic exposure of adults to effluent during gonadal recrudescence rather than through direct exposure of early life stages to effluent.