The longnose dace (Rhinichthys cataractae (Valenciennes, 1842); Cyprinidae) is one of the most widespread freshwater fishes in North America, and across its range there have been several divergent forms described that are of uncertain taxonomic status. One of these forms, the Nooksack dace, is found in southwestern British Columbia and adjacent portions of western Washington, and is distinguished from longnose dace by a lower number of lateral-line scales. We sequenced a total of approximately 1400 base pairs (bp) of mitochondrial DNA (mtDNA) and noted that the longnose dace found west of the Continental Divide and Nooksack dace constituted reciprocally monophyletic clades that differed from each other by between 2% and 3% sequence divergence. Sequence analysis at two nuclear loci (the S7 ribosomal protein intron 1 (S7) and recombination activation gene 1 (RAG1)), however, showed no consistent difference between longnose dace and Nooksack dace and several alleles were shared between them. By contrast, consistent differences at both mtDNA and nuclear DNA loci were resolved between R. cataractae samples from east and west of the Continental Divide. The Nooksack dace does not appear to warrant separate taxonomic status from the longnose dace, but the mtDNA differences support its recognition as an important compo- nent of the evolutionary and biogeographic legacy of R. cataractae.

We investigated the evolution of male agonistic behaviour and nuptial coloration in populations of the threespine stickleback, Gasterosteus aculeatus, with either monomorphic red or monomorphic black coloration. Specifically, we examined the responses of males from the two population types to computer-generated animations of males with black, red, or dull grey throats on otherwise identically coloured bodies. Males varied greatly in their aggressive responses among individuals and among trials, and did not show statistically significant discrimination towards the differently coloured animations. These results, therefore, do not suggest a role for interactions among males in the evolution of divergent male nuptial coloration. In addition, these negative findings are consistent with other studies of stickleback from western North America, suggesting that geographic variation in agonistic colour discrimination may account, in part, for the discrepancies between the results of earlier studies. Given the diverse methods of studies on this topic, however, methodological differences may also have contributed to the inconsistent results.

The Umpqua and Millicoma dace are small cyprinid fishes endemic, respectively, to the Umpqua and Coos rivers on the central coast of Oregon. The origins and relationships of these dace are unclear; however, two hypotheses have been postulated that assume these dace had evolved from a longnose dace (Rhinichthys cataractae (Valenciennes, 1842)) like ancestor, but from different modes of origin. The direct origin hypothesis postulates that each of these dace originated directly, but independently, from a common ancestor. In contrast, the indirect origin hypothesis postulates that the Umpqua dace originated from a R. cataractae like ancestor and that the Millicoma dace evolved from the Umpqua dace. We used mitochondrial (cytochrome b and control region) sequences to test the two hypotheses. Our maximum likelihood analysis supports the indirect origin hypothesis and argues that together the Umpqua and Millicoma dace form a distinctive Oregon coastal clade within the R. cataractae species group. We also attempt to reconcile this result with the observation that the geographic distribution of the morphologically divergent Umpqua dace is sandwiched between the geographic ranges of the morphologically similar Millicoma dace and longnose dace.

Using gillnets and trap nets, we examined the spatial distribution, diel movements, and environmental tolerances of pygmy whitefish, Prosopium coulterii, in a small boreal lake in north-central British Columbia. Most gillnets were set below the thermocline but we also fished a shore net in the littoral zone. During the ice-free season (May to November) there was a strong diel onshore–offshore movement: during the day pygmy whitefish were offshore and below the thermocline (water temperatures of 4–6°C) but at night they were inshore and above the thermocline (water temperatures of 12–18°C). This onshore–offshore movement occurred close to the bottom and, regardless of where they were caught, most fish were <4 m off the bottom. Oxygen concentrations in most of the hypolimnion dropped to <5.0 mg l−1 in June and by late August to <1.0 mg l−1; indicating pygmy whitefish can tolerate low oxygen conditions. The catch of pygmy whitefish in gillnets set below the thermocline was highly skewed: 53% of the nets were empty, 37% caught 18 or less fish, and 10% caught 70% of the total catch (742 fish). Trap nets produced similarly skewed results: most trap net sets caught no pygmy whitefish but one set caught over 2,000 individuals. Our catch data suggest that in Dina Lake #1 some pygmy whitefish aggregate.

Canonical correlation analysis (CCA) can quantitatively partition historical and ecological information from morphometric data where these features are otherwise confounded. CCA is applied to sample site locality morphometric data and corresponding sample site locality coordinate data for bull trout. Two vectors result. The first accounts for the maximum morphometric variation correlated to geographic information specified by the locality coordinates. The second represents the remaining less correlated variation. For biogeography, the first vector generates historical hypotheses for Pleistocene glacial refugia and for post-Wisconsinan glacial recolonization patterns and phylogeographic relationships. The second vector infers hypotheses for broad ecological patterns. The historical biogeographic patterns for bull trout suggest recolonization from either two or three glacial refugia and emphasize within-species biodiversity in western North America. These patterns from the Chehalis and Columbia refugia are largely concordant with other analyses based on molecular genetics. The morphometric analysis also suggests the additional possibility of a Nahanni and (or) Bering refugium. The ecological patterns suggest the importance and extent of anadromy and migration within these historical groups and how this may have affected postglacial recolonization, present distributions, and life histories.

We compared courtship behaviour of male threespine sticklebacks (Gasterosteus aculeatus) from an 'old' hybrid zone (OldHZ) and 'new' hybrid zones (NewHZ) in southwest British Columbia. High frequencies of phenotypically-intermediate forms occurred in each HZ, between the low-plated freshwater (FW) and high-plated marine (MAR) forms. The OldHZ was formed early in the present post-glacial period and probably has existed for thousands of years. The 'new' HZ (NewHZ) is a system of drainage ditches built in the late nineteenth century. In the laboratory, we quantified and compared courtship behaviour (zigzags, bites, creeping through, fanning) of males from each HZ. We compared these results with those from a previous study that quantified courtship of FW and MAR males. In general, courtship of male from the NewHZ was intermediate between the FW and MAR forms, but zigzag courtship of males from the OldHZ was the significantly less vigorous. In general, other courtship behaviour (biting, fanning, gluing, crawling through and the first response) of hybrid zones males was intermediate between FW and MAR males. Within each HZ, courtship differences were not related to phenotype (lateral plates) or size of males or females. The reduced zigzag courtship of OldHZ males is consistent with the hypothesis that change in courtship behaviour of hybrid phenotypes is evidence of the development of premating isolating mechanisms between the FW and MAR forms. There is no evidence, however, of any form of hybrid inviability although we did suspect that we had less success getting OldHZ males to build nests in our laboratory tanks. Without firm evidence of some form of hybrid inviability, the conclusion that male courtship could serve as an isolating mechanism remains speculative.

The Salish sucker is a distinctive longnose sucker found in southwestern British Columbia (the lower Fraser Valley) and western Washington. Although there is some overlap, Principal Component Analysis indicates that Salish suckers differ in their morphometry from other northwestern North American longnose suckers (i.e., those in Bering Sea, upper Mackenzie, Fraser and Columbia drainage systems). We also investigated variation in the mitochondrial DNA genome of Catostomus catostomus by sequencing PCR-amplified fragments from two genes: a 360 bp region of the cytochrome b gene and a 510 bp region of the NADH subunit 2 (ND2) gene. These data suggest that British Columbia was colonized postglacially by longnose suckers from three sources: the Bering, Great Plains, and Pacific refugia. We found no diagnostic haplotypes in either the Fraser (excluding a few lower Fraser tributaries) or Columbia River systems. These drainages contain a mixture of typical western North American haplotypes. In contrast, Salish suckers possess unique haplotypes that distinguish them from all other northwestern long-nose suckers. Thus, both the morphometric and molecular data indicate that Salish suckers have diverged from typical northwestern longnose suckers. Our molecular data also hint at divergence between "western" and "eastern" North American longnose suckers; however, the sample sizes are too small to be certain, Although both "typical" western longnose suckers and Salish suckers occur in the Fraser system, they are separated by about 60 km of unobstructed river, and there is no evidence of gene-flow between the two forms. Thus, we conclude that the Salish sucker constitutes an evolutionarily significant unit within the longnose sucker genome and as such warrants protection in both British Columbia and Washington State.

The ability of black mudfish (Neochanna diversus Stokell) to withstand hypoxia and drought was examined by observing an isolated population near Hamilton, New Zealand over the course of a year (September 1988-November 1989). In addition, a series of experiments were performed to determine what dissolved oxygen levels trigger air-breathing in the black mudfish, and the length of time this species can survive out of water in a humid environment. Air-breathing behaviour in black mudfish involves rising to the surface, gulping an air bubble and holding the bubble in the buccal cavity while the fish continues gill ventilation. Water in the study drain started to become hypoxic in mid November and by early December oxygen levels were <3.0 mg litre(-1) on the surface and <1.0 mg litre(-1) near the bottom (15 cm deep). In the laboratory, at water temperatures ranging from 20 to 22 degrees C, none of the 20 test fish gulped air from the surface until oxygen levels dropped below 2.5 mg litre(-1); c. 45% of the animals began air-gulping at oxygen levels between 2.0 and 2.5 mg litre(-1) and, at oxygen levels below 1.0 mg litre(-1), 100% of the test fish gulped air from the surface. Over a similar temperature range, animals were kept on damp moss for 10 weeks (the drought duration in the drain was 132 days). Under these conditions, test animals lost weight steadily: adults lost 17-24%, and young-of-the-year 30-45%, of their initial weight. On re-immersion, all adults recovered; however, two young-of-the-year fish died. Within 4 h of re-immersion, the surviving fish increased their body weight by 6-12%, but within 24 h they returned to their pre-immersion weight. The mechanisms involved in drought resistance in black mudfish (and their relevance to conservation and habitat preservation) are discussed. A possible option for the restoration, and maintenance, of mudfish in habitats formerly occupied by this species complex is to provide appropriate drought shelters while maintaining a regime of seasonal drought to remove competitors.

We measured survival of bull trout (Salvelinus confluentus) embryos to the alevin stage in areas selected and not selected by females for spawning. In this study we tested the hypotheses that (1) females are utilizing habitats influenced by discharging groundwater and that (2) there is a reproductive advantage to spawning at these selected sites. Embryo survival was assessed by placing fertilized eggs in capsules that could be retrieved once they were placed in selected and nonselected locations. The survival rate was significantly higher (88.6 vs. 76.1%) and less variable in the selected area, but alevin lengths did not differ significantly between areas. The selected areas were, on average, locations of groundwater discharge and higher water temperatures over the incubation period, while nonselected locations were in areas of surface-water recharge and lower water temperatures. The results suggest that appropriate reproductive habitats which offer the best incubation environments may be limited in bull trout systems, and that site selection by females may increase fitness and be critical for population viability.

Species pairs of threespine stickleback, Gasterosteus aculeatus, co-exist in several lakes in the Strait of Georgia, southwestern British Columbia. One species, ‘benthics’ is robust-bodied and is morphologically and behaviourally specialized for benthivory. The other species, ‘limnetics’ is specialized for planktivory in open-water habitats of the lakes. We examined mitochondrial DNA restriction site variation in benthic and limnetic sticklebacks as well as in solitary freshwater, anadromous (sea-run), and marine populations to test: (i) if benthic and limnetic pairs have evolved only once or multiple times (parallel evolution) and (ii) if the species have evolved sympatrically, or allopatrically from ‘double invasions’ of lakes by ancestral anadromous/marine sticklebacks. Stickleback mtDNA comprised a single clade with a low (mean = 0.40%) degree of sequence divergence among the 77 haplotypes resolved. Most nucleotide diversity (97%) was found within (rather than among) populations of anadromous/marine sticklebacks whereas most diversity (77%) was found among populations in freshwater sticklebacks. Significant differences in haplotype frequencies were found between benthics and limnetics in three of the four species pair lakes examined, but in all cases the pairs within lakes were characterized by unique assemblages of closely related haplotypes. Hierarchical clustering of divergence estimates suggested that comparable species from different lakes have originated independently in all lakes because in no case did comparable species from different lakes cluster together. Divergent species within lakes tended to be more closely related to one another than to species in other lakes and there were two cases were benthics and limnetics within a particular lake were monophyletic. In two of the four two-species lakes, limnetics were less divergent from putative ancestral anadromous/marine stickleback as predicted by the double invasion hypothesis, but in the two other lakes benthics were less divergent. Our data argue strongly that the species pairs have evolved independently in each lake were they now co-exist. Further, in two lakes our data are consistent with the species having evolved by sympatric divergence, but allopatric divergence followed by introgression of mtDNA that has obscured ancestral relationships cannot be discounted completely. Finally, despite remaining uncertainty about the geography of speciation, the species appear to have evolved in the face of gene flow arguing that natural selection acting on trophic ecology has been a major component of ecological speciation in sticklebacks.

This datasheet on Catostomus catostomus covers Identity, Distribution.

Skistodiaptomus oregonensis vertical migration in Kennedy Lake and Paxton Lake may be an adaptation to avoid predation by threespine stickleback (Gasterosteus aculeatus). In Kennedy Lake, juvenile sockeye salmon (Oncorhynchus nerka) and the mysid Neomysis mercedis are also predators that potentially drive the vertical migration. A corollary of the hypothesis that predation selects for vertical migration is that the extent and timing of the vertical migration decreases predation risk. This corollary is tested for each of the potential predators. Laboratory experiments indicate that stickleback feeding rate decreases below 1.6 µE ·s-1 ·m-2. In Kennedy and Paxton lakes, S. oregonensis occupied depths below this light intensity during the day. Furthermore, as S. oregonensis ascended at dusk and descended at dawn, they remained within light intensities that reduced stickleback predation rate. In Kennedy Lake, hydroacoustic data coupled with information in the literature on feeding behaviour of juvenile sockeye indicate that this species move to surface waters to feed before sunrise and after sunset. Vertically migrating S. oregonensis are near the surface during the twilight feeding periods of juvenile sockeye. The timing of S. oregonensis vertical migration also does not reduce the time it is in contact with the predator N. mercedis.

The benefits and costs of vertical migration behaviour of the freshwater lacustrine copepod, Skistodiaptomus oregonensis, is explored through the study of two migrating and two nonmigrating populations. The association of vertical migration with the presence of pelagic threespine stickleback (Gasterosteus aculeatus) is consistent with the hypothesis that the adaptive benefit of vertical migration by S. oregonensis is avoidance of predatory stickleback. The hypothesis of avoidance of juvenile sockeye salmon (Oncorhynchus nerka) predation is not supported. Skistodiaptomus oregonensis do not migrate in the lake with the highest juvenile sockeye abundance but do migrate in the lake where juvenile sockeye are absent. A foraging efficiency hypothesis does not explain migration behaviour; neither food abundance nor food distribution distinguish lakes where S. oregonensis migrate from lakes where they do not migrate. Neither a bioenergetic efficiency hypothesis nor a thermal advantage hypothesis explain migration behaviour; temperature structures are similar in all four lakes examined. Vertical migration appears to be the result of a trade-off between predator avoidance and resource acquisition. Phytoplankton food is less concentrated in the deep habitat where S. oregonensis reside during the day. Furthermore, migrators contain less phytoplankton food in their guts than nonmigrators.

We observed the behaviour of juvenile steelhead trout (Oncorhynchus mykiss) in two rivers in British Columbia, Canada, to determine the importance of invertebrate drift abundance, intruder pressure. and body size of territory holders as correlates of territory size. Territory size increased with increasing fish size, but fish smaller than 5 cm had relatively large territories for their body size, in comparison to fish that were larger than 5 cm in length. After statistically controlling for the effect of body size, territory size was inversely related to the abundance of drifting invertebrates. Territory size was not related to the number of intrusions observed on a territory per hour, but was inversely related to local fish density, a second measure of intruder pressure. Steelhead trout appear to defend territory areas that are most similar in size to juvenile Atlantic salmon. This study provides evidence that stream-dwelling salmonids scale territory size to body size in a manner that allows them to capture a maximum daily ration of food on their territories.

We measured day and night microhabitat preferences of age-1 juvenile bull trout Salvelinus confluentus in an artificial stream channel in early spring, and observed a significant diel shift in both microhabitat use and preference. Microhabitat variables examined were water depth, stream bottom water velocity, overhead cover, and substrate. Fish showed a stronger preference for cover during the day than at night, and generally preferred the deeper and faster areas in the channel at night compared to the daytime. The results are of importance in determining how juvenile bull trout use cover, and they suggest that maintaining or increasing rearing capacity and survival of juveniles is related to ensuring that adequate amounts of large, coarse rock substrate remain in streams. Our observations also suggest that daytime snorkeling counts of juvenile bull trout may provide inaccurate estimates of abundance because of the juvenile's extensive use of cover during the day.

The Nooksack Dace (Rhinichthys sp.) is a morphologically distinctive form derived from the common, widely distributed Longnose Dace, Rhinichthys cataractae. Like the Salish Sucker (Catostomus sp.), it is a component of the Chehalis fauna. This fauna survived the last glaciation in the ice-free area west of the Cascade Mountains and north of the Columbia drainage system. In Canada, the Nooksack Dace is confined to four small streams tributary to the Nooksack River in the Abbotsford, Aldergrove and Clearbrook areas of the lower Fraser Valley, southwestern British Columbia. The adult habitat is riffles, typically with water velocities close to 0.25 m-sec and a loose, coarse gravel substrate. Young-of-the-year inhabit shallow margins at the tail-ends of pools with mud/sand substrates. and typically recruit to the adult habitat after one year. Although the Nooksack Dace is still moderately common, suitable habitat is deteriorating rapidly through explosive urbanization and gravel extraction in the headwaters of the streams. In western Washington state, the Nooksack Dace is widespread and in no immediate danger but, in Canada, given its restricted distribution and deteriorating habitat it is endangered.

McPhail, J. D., and J. S. Baxter. 1996. A review of bull trout (Salvelinus confluentus) life-history and habitat use in relation to compensation and improvement opportunities. Fisheries Management Report No. 104, 35 p. The bull trout (Salvelinus confluentus) is a char endemic to western North America. It has had a confused taxonomic history, and its specific distinction from the Dolly Varden (Salvelinus malma) is still in doubt. In the areas where the two nominal species overlap there is evidence of hybridization and even introgression. This taxonomic problem has management implications, and will only be solved by studies in the areas of geographic overlap. The bull trout spawns in the fall (September to October) in flowing water. The threshold spawning temperature is around 9°C. Courtship and spawning behaviour are similar to other char. The female chooses the deposition site and digs the redd. The degree of sexual dimorphism varies among populations, but in most populations males develop bright spawning colours and a kype, while females are less colorful. The eggs are about 5-6 mm in diameter and optimal incubation temperature ranges from 2 to 4°C. In the wild, fry emerge approximately 220 days after egg deposition. Newly emerged fry are secretive and hide in the gravel along stream edges, and in side channels. Juveniles are found mainly in pools, but also in riffles and runs. They maintain focal sites near the bottom and are strongly associated with instream cover, especially overhead cover. Juveniles feed primarily on aquatic insects taken from the bottom or from drift. As they grow, their diet shifts to fish, and most adults (except for stream residents) are piscivores. Like many char, the bull trout occurs as a number of life-history forms. The stream-resident form lives out its life in small headwater streams. It is often dwarfed and reaches sexual maturity at a small size, and sometimes at an early age. The fluvial form lives as an adult in large rivers but spawns in small tributary streams. It often attains a large size, reaches sexual maturity at about five, and undergoes long migrations between mainstem rivers and small tributary spawning streams. The lacustrine-adfluvial form has a similar life-history. It spawns in tributary streams but lives as an adult in lakes. It grows to a large size, usually reaches sexual maturity in about its fifth year, and often makes long migrations between lakes and spawning streams. A fourth possible life-history type is anadromy. The evidence for the existence of anadromous bull trout is still slim, but in the Puget Sound-Strait of Georgia region they probably occur. There has been no formal attempt to document the life-history of anadromous bull trout. The evidence for homing in migratory bull trout is equivocal, and some populations probably home with great fidelity while others show a high rate of straying. The genetic structuring of bull trout populations suggest that many populations have been through genetic "bottlenecks". Genetic variability within populations is low, but genetic differences among populations often are marked. This, along with striking inter-population differences in nuptial colouration and sexual dimorphism, suggest the existence of distinct stocks. Adult and juvenile densities are often low, and the species is sensitive to environmental degradation and over-fishing. Human activities that create migration barriers, increase siltation, and increase variation in natural temperature and flow regimes within streams, are particularly harmful. Bull trout do not do well in competition with introduced salmonids, and there is evidence that introduced lake trout have replaced bull trout in a number of lakes. Bull trout are declining in numbers throughout their range, especially at the southern edges of their distribution where a number of populations have become extinct. Unfortunately, opportunities for enhancement are limited, and the major hope for restoring bull trout numbers lies with regulation (e.g., closures, gear restrictions and harvest limits) and public education.

We conducted an experiment to assess the change in foraging efficiency resulting from diet-induced morphological and behavioural plasticity in a species of freshwater, threespine stickleback (Gasterosteus sp.). Different degrees of morphological and behavioural change were induced using two prey items commonly found in the diet of this species, allowing us to estimate the relative importance of each type of plasticity. The purpose of the experiment was twofold. First, earlier work had suggested that diet variability might be an important factor in the evolution of trophic morphological plasticity in sticklebacks. The present results extend this work by revealing the adaptive significance of morphological plasticity. The current experiment also qualitatively assessed the compatibility of the time scale of morphological change with that of the natural resource variability experienced by this species. The results indicate that diet-induced plasticity improves foraging efficiency continuously for up to 72 days of prey exposure. This is probably due in part to plasticity of the external trophic morphology but our results also suggest a complex interplay between morphology and behaviour. The time scale appears to be matched to that of natural diet variability although it is possible that some traits exhibit non-labile plasticity. Our discussion highlights the important distinction between conditions favouring the evolution of labile versus non-labile plasticity. The second objective of the experiment was to determine the relative importance of morphological and behavioural plasticity. Few studies have attempted to quantify the adaptive significance of morphological plasticity and no study to our knowledge has separated the effects of morphological and behavioural plasticity. Our experiment reveals that both behavioural and morphological plasticity are important and it also suggests a dichotomy between the two: behavioural plasticity predominately affects searching efficiency whereas morphological plasticity predominately affects handling efficiency.