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Nickel (Ni) is an ubiquitous, naturally occurring metalthat is associated with metal mining and other industrialactivities. Despite elevated Ni concentrations reportedfor many industrial receiving waters, Ni receives littleresearch attention addressing factors influencing itstoxicity to freshwater fish. This study examined theinfluence of water hardness, pH, and total suspended solids(TSS) in soft, reconstituted water on Ni toxicity to larvalfathead minnows (Pimephales promelas). Increasingwater hardness from 20 to 140 mg L-1 (as CaCO3) reduced acute Ni toxicity by 5-fold (96-h LC50s 0.45 and 2.27 mg Ni L-1, respectively). Low pH had a slight protective effect against Ni toxicity relative to neutral pH conditions. At pH 5.5, the 96-h LC50 was 0.69 mg Ni L-1, compared to 0.54 mg Ni L-1 at pH 7.0. However,Ni toxicity was significantly reduced at pH 8.5 where the 96-h LC50 was 2.21 mg Ni L-1. These results were explainedon the basis of Ni speciation. Total suspended solids also reduced Ni toxicity (expressed as 96-h LC50s) from 0.35 to 1.12 mg Ni L-1 over a TSS range of 10 to 100 mg L-1.This reduction of toxicity due to TSS is significant becausemine effluents often have a combination of elevated TSS andmetals. The ameliorative effect of TSS was not as significantas high hardness or pH probably because there is a TSS threshold, after which physical irritation to fish gills counteracts any protective effect conferred by TSS. This finding is relevant to choices made in design of mine effluenttreatment systems; i.e., there may be an optimum range ofTSS concentrations that protect aquatic biota againsteffects of metals that remain after treatment.

Larval fathead minnows (Pimephales promelas) were placed at four exposure sites for 7 days in each of five lakes surrounding the Key Lake uranium mine in northern Saskatchewan, Canada. Fish placed in lakes receiving Mo-contaminated mill effluent demonstrated higher mortalities than those placed in lakes receiving Ni-contaminated mine-dewatering effluent, which was not significantly different from reference sites. No significant differences were detected in fish growth among the study lakes because of the high (90%) mortality in Fox and Unknown lakes. Principal components analysis characterized exposure sites by total and dissolved metal concentration. Stepwise multiple regression of fish mortality on principal components generated from total metal data revealed that principal component 1 could account for 84% of the variance associated with fish mortality. Careful examination of the metals that correlated strongly with principal component 1 and with fish mortality suggested that dietary Se toxicity probably resulted in the differential fathead minnow mortality observed among study lakes.

AdultHoplocampa montanicolaRohwer emerged in mid-May, 6.2 ± 3.2 days (mean ± SE) prior to the period of peak anthesis inAmelanchier alnifoliaNuttall. Oviposition, one egg per flower, occurred during the period of petal drop in late-May; a mean ± SE of 2.2 ± 0.2 eggs were deposited in each inflorescence. Eggs hatched 7.7 ± 3 days (mean ± SE) after the period of primary petal drop and larvae fed on a mean ± SE of 1.8 ± 0.14 fruit per infructescence. Larvae completed development by the end of June, just as the first fruit ofA.alnifoliawere beginning to ripen. Larvae overwintered in the leaf litter.AdultAnthonomus quadrigibbusSay (previously assigned to the genusTachypterellus) were first collected in mid- to late-May during the periods of anthesis and fruit drop inA.alnifolia. Immature fruit fed upon were often extensively damaged. Oviposition occurred toward the end of fruit drop inA.alnifolia, 30.6 ± 2.5 days (mean ± SE) after the period of peak anthesis. Only one egg was laid in a puncture at the base of a fruit. Larval feeding was restricted to ovules and occurred in fruit retained on the plant. Pupation and adult emergence occurred in mid-July as fruit were ripening. The new generation of adults then entered the leaf litter to overwinter.

Elevated concentrations of arsenic, nickel, and molybdenum in aquatic systems around northern Saskatchewan uranium mines are an environmental concern. Early life stage fathead minnows were used to assess toxicity from several aquatic systems near the Key Lake and Rabbit Lake uranium operations. Hatching success of fish embryos exposed to waters receiving contaminants associated with uranium ore milling was reduced by 32-61% relative to controls. Mortality differed in two lakes receiving mill effluents because of opposing factors influencing metal toxicity (i.e. low pH and high hardness). In one mill receiving water (Fox Lake), larval mortality was 0%, whereas mortality was 85% in water collected from a downstream location (Unknown Lake). Fish embryos exposed to open-pit dewatering effluent receiving waters, or water from a flooded open pit (i.e. pit waters), hatched 26-39% earlier than those exposed to reference or control water. The combination of low water hardness and elevated nickel concentrations in pit waters contributed to the early hatching. Egg hatchability and hatching time were more sensitive indicators of toxicity than 'standard' endpoints, like larval mortality and growth. Current regulatory emphasis on single contaminants and standard toxicological endpoints should be re-evaluated in light of the complex interaction among confounding variables such as pH, hardness. conductivity, and multi-metal mixtures.

The impact of methoxychlor exposure on aquatic insects inhabiting artificial substrates was monitored at three downstream sites relative to an upstream untreated site of the North Saskatchewan River. Treatment impact was studied for selected species of Simuliidae (Diptera), Perlodidae (Plecoptera), Hydropsychidae (Trichoptera), Baetidae and Heptageniidae (Ephemeroptera). At sites subjected to methoxychlor exposure which were 21, 38, and 107 km from injection, population changes varied depending on species and distance from the injection point. Although populations of some species were not significantly affected by treatment at any downstream site (P > 0·0.5), others were significantly reduced at one or more of the sites (P < 0·5 − P < 0·01). Nymphs of Stenonema terminatum (Walsh) and Baetis tricaudatus Dodds (Ephemeroptera) apparently recolonized after dislodgement due to methoxychlor exposure. Species are categorized on the basis of their responses to methoxychlor treatment. Factors which probably caused different treatment impacts among species are discussed.

Insects are particularly suited for use in environmental impact assessment (e.i.a.) because of their high species diversity, ubiquitous occurrence, and importance in the functioning of natural ecosystems. Examples are given of the use of insects in the predictive phase of e.i.a., in the monitoring and assessment phase, and in the much rarer instance of an e.i.a. that includes both of these phases. The importance of working at the species level to understanding the results of e.i.a. is emphasized.

Drift of aquatic insects was compared at three sites downstream (21, 38, and 107 km) from methoxychlor treatment (0.3 mg. L−1 for 15 min) of the North Saskatchewan River, relative to an upstream untreated site. Species of Diptera (Simuliidae), Ephemeroptera (Baetidae, Heptageniidae, Ephemerellidae, Ametropodidae, Metretopodidae, and Tricorythidae), Plecoptera (Perlodidae and Chloroperlidae), Trichoptera (Hydropsychidae and Hydroptilidae), and Hemiptera (Corixidae) were studied. Drift responses differed depending on species, distance from the injection site, and time after methoxychlor injection. Exposure to methoxychlor initiated catastrophic drift of aquatic insects at all downstream sites. Of 22 species compared before treatment and following methoxychlor injection, post-treatment drift of 17, 21, and 13 species significantly exceeded pre-treatment drift at the km 21, 38, and 107 sites, respectively. Methoxychlor treatment initiated or increased drift of several normally non-drifting species. Similar drift patterns were observed among closely related taxa during the catastrophic phase. For all species studied, comparisons of 24-h drift densities between days preceding and following the catastrophic phase of treatment indicated significant post-treatment drift density increases or decreases at one or more of the downstream sites, but not at the untreated site. Species were classified according to their drift responses to methoxychlor treatment. Factors that may have caused different drift responses among species are discussed.

Eight species of Chironomidae (Diptera), including Cricotopus sp. nr. tremulus, Tvetenia vitracies (Saether), Nanocladius (s.s.) cf. rectinervis (Kieffer), Nanocladius branchicolus Saether, Nanocladius (s.s.) cf. spiniplenus Saether, Paratanytarsus confusus Palmen, Polypedilum (s.s.) convictum (Walker), and Rheotanytarsus sp., are reported for the first time in phoretic association with nymphs of Pteronarcys dorsata (Say) (Plecoptera: Pteronarcyidae). The stoneflies and associated chironomids were found in rivers of central and northern Saskatchewan. Rheotanytarsus sp. and P. convictum were the most common ectosymbionts on P. dorsata. Phoretic larvae were found most frequently attached to the host’s metathorax. Pteronarcys dorsata nymphs may be ideal hosts for phoretic inhabitants because of their abundance, large size, and detrivorous habit.

Acanthomola pubescens, a new genus and species of Heptageniidae (Ephemeroptera), is described from larvae collected in Saskatchewan and Alberta. Acanthomola superficially resembles Bleptus, Epeorus, and Raptoheptagenia, but differs from these genera, and all other heptageniids, in the structure of the mandibles and maxillae. The molar area of the mandible is greatly reduced and bears only a few stout spines. The crown of the maxillary galea-lacinia is rounded and lacks setae near the apex. The apical segment of the maxillary palpus is long, slender, and bare. Generic and specific descriptions of the larva of A. pubescens, gen. nov., sp. no v., are given, along with biological notes. Acanthomola appears to be a very primitive heptageniid, related to Bleptus, Epeorus, and Ironodes. It is probably most closely related to Spinadis.

Crop failures are a frequent phenomenon of saskatoon berries, Amelanchier alnifolia Nutt., in Saskatchewan. The curculionid beetle Tachypterellus quadrigibbus Say is shown to have a pronounced effect on the relation and quality of fruit produced. Its feeding and reproductive habits on the berries are proposed as a major cause of crop failures.

Fifteen species of stoneflies (Plecoptera) were collected in the Lake Athabasca region of northern Saskatchewan. Capnia nearctica Banks is reported for the first time from Saskatchewan, and collection records of Isogenoides frontalis (Newman), Nemoura rickeri Jewett, and Paracapnia angulata Hanson represent significant range extensions. All species collected from lotic habitats have biogeographical affinities with streams from the Southern Boreal Ecoregion, but some species collected from Lake Athabasca have biogeographical affinities with the Southern Boreal Ecoregion and others have affinities with the Tundra.

The previously undescribed adult male and female ofAnaletris eximiaEdmunds are treated. Additional features of nymphs are illustrated. In the Saskatchewan River system the species is found in areas unaffected by reservoirs; nymphs develop in May?, June, and July; adults emerge in late July. Nymphs are carnivorous (chironomids were the main food item in field collected specimens), live in backwaters adjacent to the main river current, and are morphologically adapted to life on an unstable silty substrate. Invasion of the Saskatchewan system was apparently via Missouri tributaries from the Colorado system. It occurred in recent times in the latter but apparently not the former. Because of habitat destruction, the species is considered endangered.

A key to species for adults and figures of the three North AmericanCinygmaare presented. New distribution records are given; the range ofC.lyriformisMcDunnough is extended to Alaska and the genus in the Palearctic is discussed. Nymphs are undescribed except forC.integrum(Eaton). The life history of the latter is given for Oregon. Nymphs of all size classes are present throughout the year but adult emergence is restricted to mid May to mid July. Nymphs apparently are restricted to a submerged wood habitat.

Baetis bundyi new species is described from nymphs which were collected from tundra ponds in the central Canadian arctic (62.45 N., 94.27 W.). Based on measurements of a series of nymphs the eggs must hatch in early July and adults emerge in August. A table is presented for separating this species from other known arctic Baetis.

Adult males were reared from larvae of the type previously associated withAnepeorus. These adult males key to and fit the description ofHeptagenia cruentataWalsh. Because the larvae are very different from those of otherHeptageniaspecies, a new genus,Raptoheptagenia, is proposed forcruentata. Adult males ofRaptoheptageniadiffer from those ofHeptageniain the anastomosis of two or more crossveins in the stigmatic area of the forewing, and in the subequal lengths of the foretarsus and tibia.