Search

We recently observed a reliable phenotypic difference in the inflammatory pain sensitivity of a congenic mouse strain compared to its background strain. By constructing and testing subcongenic strains combined with gene-expression assays, we provide evidence for the candidacy of the Yy1 gene - encoding the ubiquitously expressed and multifunctional Yin Yang 1 transcription factor - as responsible. To confirm this hypothesis, we used a Cre/lox strategy to produce mutant mice in which Yy1 expression was ablated in Nav 1.8-positive neurons of the dorsal root ganglion. These mutants also displayed reduced inflammatory pain sensitivity on the formalin test. Further testing of pain-related phenotypes in these mutants revealed robustly increased sensitivity to systemic and spinal (but not supraspinal) morphine analgesia, and greatly increased endogenous (swim stress-induced) opioid analgesia. None of the known biological roles of Yin Yang 1 were suggestive of such a phenotype, and thus a novel player in pain modulatory systems has been identified.

Atlantic salmon Salmo salar of U.S. hatchery origin were captured as postsmolts by surface trawling during spatial surveys in late May to mid-June in the northeastern Gulf of Maine in 2002 and 2003. Most marked and unmarked postsmolts were from the Penobscot River, but some were also from the Dennys and other rivers of the Gulf of Maine. The capture rate of stocked smolts was very low (≤0.01%), and it was highest for marked smolts from known rivers and proportional to numbers stocked. Marked postsmolts were caught 16–43 d after their release as smolts and 89–240 km from their river of origin. The rate of migration from different rivers differed and varied annually, and it accounted for some of the observed differences in capture rate. The weight of postsmolts from known rivers was greater than at smolt stocking and river exit, indicating early marine growth. The distribution of U.S. postsmolts from different rivers was similar, and they were often caught together, as were those from the same rive...

Existing microarray gene expression profiling studies of tonic/chronic pain were subjected to meta-analysis to identify genes found to be regulated by these pain states in multiple, independent experiments. Twenty studies published from 2002 to 2008 were identified, describing the statistically significant regulation of 2254 genes. Of those, a total of 79 genes were found to be statistically significant "hits" in 4 or more independent microarray experiments, corresponding to a conservative P

Atlantic salmon ( Salmo salar ) smolts of wild and hatchery origins (n = 522) were tagged with ultrasonic transmitters and monitored at successive arrays of submerged receivers during migration from five watersheds in three regions of the Bay of Fundy (BoF), Canada. Two of the regions had endangered inner BoF salmon populations. Migration success of postsmolts leaving the BoF varied widely among 13 groups monitored (3%−70%) and was influenced by behaviour and passage time. Region of origin was the key variable in habitat-specific survival models selected using the Akaike information criterion. Rearing origin, migration and release timing, and smolt size were important variables in some habitats. Estimated survival rates (overall and habitat specific) differed markedly among salmon populations of different regions. Mediocre estuarine survival of smolts (0.54) from the outer BoF region affected overall survival (0.66). Poor survival (0.21) in coastal areas of the distant inner BoF region and mediocre survival in other habitats resulted in low overall survival (0.06) that severely limited the potential for population recovery. Potential predators were abundant in habitats where survival was lowest. High survival of salmon from the intermediate inner BoF region in all habitats (0.81–0.93) was not responsible for their failure to return.

Hubley, P. B., Amiro, P. G., Gibson, A. J. F., Lacroix, G. L., and Redden, A. M. 2008. Survival and behaviour of migrating Atlantic salmon (Salmo salar L.) kelts in river, estuarine, and coastal habitat. – ICES Journal of Marine Science, 65: 1626–1634. The downstream migration of 30 Atlantic salmon (Salmo salar) kelts tagged with acoustic transmitters was monitored using 26 underwater receivers at eight locations from April to October 2006 in the LaHave River and Estuary. In all, 27 tags were detected as they left the coastal environment by the middle of May, 5 weeks after release, indicating a possible 90% kelt survival to coastal departure. Two missing tags and one dropped tag were assumed to be attributable to natural mortality in the estuary. Migration time from release to the outermost coastal receivers 24 km below the tide limit took an average of 14 d, but varied from 3 to 32 d. Some 40% of the kelts lingered and were active in the lower estuary. Five kelts monitored with depth transmitters migrated mostly at the surface in all habitats, with occasional brief descent to the bottom. A consecutive spawning salmon returned after 79 d outside the outermost array. The low rate of returns is consistent with the historical repeat spawning schedule for this river, and more precisely documents the temporal and spatial habitat use of migrating kelts.

Sex differences in the magnitude of response to thermal and tactile stimuli have been demonstrated in both clinical and animal studies. Females typically display lower threshold responses to painful stimuli as compared to males. We have previously observed sexually dimorphic expression of the growth factor, neuregulin 1 (NRG1) following L5 nerve root ligation (LR) in male and female rats. In the present study, we sought to determine which gonadal hormones were involved in regulating NRG1 expression following L5 nerve root ligation. We observed that expression of NRG1 mRNA and the neuregulin receptors, ErbB2 and ErbB4 in the lumbar spinal cord was facilitated by the presence of progesterone in female rats following L5 nerve root ligation. An increase in NRG1 protein and NRG1 immunoreactivity was also observed in the ipsilateral spinal cord of progesterone treated female rats as compared to ovariectomized female rats and male rats at day 14 following LR. NRG1 immunoreactivity was equally colocalized with either the astrocytic marker, GFAP, and with NeuN labeled neurons 14 days following L5 nerve root ligation. Intrathecal administration of recombinant NRG1-β1 protein significantly decreased the hindpaw tactile withdrawal threshold in male rats, ovariectomized female rats, and progesterone treated female rats. These results demonstrate a role for progesterone-dependent regulation of glial and/or neuronal neuregulin 1 in female rats in mediating sex differences in nociception. Furthermore, our results suggest that NRG1 may be involved in central sensitization during the maintenance phase, but not in the initiation of persistent pain in female rats.

Increasing evidence points to a role for spinal neuroimmune dysregulation (glial cell activation and cytokine expression) in the pathogenesis of chronic pain. Suppression of astrocytic and microglial activation with the methylxanthine derivative, propentofylline, pre-emptively attenuates the development of nerve injury-induced allodynia. Currently, we investigated the ability of systemic propentofylline to reverse existing, long-term allodynia after nerve injury--a clinically relevant paradigm. Rats received L5 spinal nerve transection or sham surgery and the development of mechanical allodynia was assessed daily for 2 weeks, at which time injured rats exhibited robust responses to non-noxious von Frey filaments. On days 14-27, rats received either saline or 101 mg/kg propentofylline by intraperitoneal (i.p.) injection. On day 28 or 42 (after a 14-day drug washout period), lumbar spinal cord sections were processed for assessment of astrocytic glial fibrillary acidic protein (GFAP) and microglial OX-42 (antibody against CR3/CD11b). Propentofylline treatment to nerve injured rats resulted in significant reversal of allodynia that lasted throughout the 14-day washout period. Spinal microglial activation was observed at days 28 and 42 post-injury at the protein level, in the absence of mRNA level changes. Less robust increases in GFAP immunoreactivity were observed at days 28 and 42 post-transection. Interestingly, propentofylline treatment suppressed microglial activation at both time points in this paradigm. Taken together, our results highlight the clinical potential of the glial modulating agent, propentofylline, for the treatment of neuropathic pain as well as a role for microglia in the long-term maintenance of allodynia.

Shellfish aquaculture is an expanding industry in coastal British Columbia, Canada, and occurs in important wintering areas for surf scoters (Melanitta perspicillata) and white-winged scoters (M. fusca). We quantified habitat use by scoters in relation to natural environmental attributes and habitat modifications associated with shellfish aquaculture. We found that, despite the extensive clam and oyster farming in our study area, densities of wintering surf scoters and white-winged scoters were related primarily to natural environmental attributes, particularly intertidal area, clam density, and sediment type; shellfish aquaculture variables were generally poor predictors of bird densities. We conclude that current levels and forms of shellfish aquaculture in our study site were not an important determinant of scoter distribution and abundance, suggesting that winter scoter populations and the shellfish aquaculture industry may be mutually sustainable. We caution that intensification or further industrialization of shellfish aquaculture in British Columbia could eventually lead to detrimental effects if some threshold level of habitat modification is exceeded.

Considerable evidence indicates that there are sex-related differences in clinical and experimental pain sensitivity. In the present study, we sought to determine what genes were expressed in the spinal cord in a sexually dimorphic manner. We first analyzed global gene expression in the lumbar spinal cord of uninjured male and female rats using the Affymetrix RAE230A GeneChip® platform in order to identify genes that are selectively expressed in male and female rats at a basal level. We subsequently analyzed global gene expression in the lumbar spinal cord of male and female rats at two time points (7 days and 14 d) following a rodent model of lumbar radiculopathy (L5 nerve root ligation) in order to determine what genes were regulated in a sexually dimorphic manner following nerve root injury. We utilized a linear regression analysis method to identify genes that were significantly different from the corresponding sham surgical controls. The expression patterns of several genes of interest were subsequently confirmed using RT-PCR. Our findings demonstrate significant differences in lumbar spinal cord gene expression in both uninjured and injured (L5 nerve root ligation) male and female rats. Further confirmation of a subset of the genes identified Neuregulin 1 and its high affinity receptor, ErbB4, Tachykinin 1, and Metabotropic glutamate receptor 6 as female specific genes upregulated following L5 nerve root injury. These findings provide several target genes for further study that may elucidate the neurochemical mechanisms underlying sex differences in pain sensitivity and lead to improved treatments for chronic pain syndromes.

Reactive astrocytes display decreased glutamate transporters, such as GLT-1, and as a result synaptic glutamate clearance is impaired. In addition, these activated astrocytes are immunocompetent and release algesic mediators that can sensitize neurons in the spinal cord. Currently, we evaluated the effect of propentofylline (PPF), an experimental antiallodynic agent, on the phenotype and glutamate transporter expression of astrocytes. Primary astrocyte cultures, which represent an activated phenotype with a polygonal morphology and low GLT-1 expression, were treated for 3 or 7 days with 10, 100, or 1,000 μM PPF or dibutyryl-cAMP (db-cAMP), a known inducer of GLT-1 expression. PPF dose-dependently induced astrocytes to display a mature phenotype, with elongated processes and a stellate shape, as well as increased GLT-1 and GLAST immunoreactivity, similar to that seen with db-cAMP. Real time RT-PCR and Western blot analysis clearly demonstrated that PPF caused a potent dose-dependent induction of GLT-1 and GLAST mRNA and protein in these astrocytes. Importantly, the observed increase in glutamate transporters was found to have a functional effect, with significantly enhanced glutamate uptake in astrocytes treated with 100 or 1,000 μM PPF that was sensitive to dihydrokainate inhibition, suggesting it is GLT-1 mediated. Finally, the effect of PPF on lipopolysaccaride-induced chemokine release was investigated. Interestingly, PPF was able to dampen both MCP-1 (CCL2) and MIP-2 (CXCL2) release from astrocytes while db-cAMP significantly enhanced this chemokine expression. These findings suggest that PPF is capable of differentiating astrocytes to a homeostatic, mature phenotype, competent for glutamate clearance and distinct from that induced by db-cAMP. © 2006 Wiley-Liss, Inc.

The diagnosis of polycythemia vera (PV) is currently based on clinical and biological criteria defined either by the World Health Organization (WHO) or the Polycythemia Vera Study Group (PVSG).1, 2 Both of these classifications use clinical and biological markers organized in major and minor criteria, allowing to diagnose a PV when a define combination of major and minor criteria is present. Recently, a somatic point mutation of the tyrosine kinase JAK2 (JAK2 V617F) has been described in about 80% of PV patients as well as 30% of essential thrombocythemia (ET) and 50% of idiopathic myelofibrosis (IMF)3, 4, 5, 6 and several in vitro and in vivo experiments demonstrated that this mutation of JAK2 was the molecular event at the origin of PV.3 It was therefore tempting to use the detection of JAK2V617F as a diagnostic test for erythrocytosis. Such an attitude supposes the development of other techniques than sequencing, as this latter is time consuming and not always feasible in hematology laboratories. We thus compared sequencing with two techniques of real-time PCR-based mutation detection (one using the LightCycler® instrument, the other the Taqman® ABI Prism 7500), for the efficiency to detect the JAK2 V617F mutation in 119 samples from patients with suspicion of myeloproliferative disorder (MPD). The three techniques were equivalent in all samples but one, where sequencing failed to detect the mutation revealed by both LightCycler® and Taqman® technologies. To evaluate the sensitivity of these techniques, we tested serial dilutions of the homozygously mutated HEL cell line DNA in the nonmutated TF-1 cell line DNA, and serial dilutions of the genomic DNA from a patient homozygous for the JAK2 V617F mutation in normal DNA. Sequencing failed to detect the mutated allele under 5% of HEL cell line DNA diluted in TF-1 cell line DNA, and under 10% of the homozygously mutated patient's DNA diluted in normal DNA. The sensitivity of LightCycler® and Taqman® techniques were equivalent, slightly higher than sequencing, reaching 0.5–1% of HEL cell line DNA diluted in TF-1 cell line DNA (Figure 1), and 2–4% of a homozygously mutated patient's DNA diluted in normal DNA.

Atlantic salmon (Salmo salar) postsmolts surveyed by surface trawling in the Bay of Fundy and Gulf of Maine during 2001–2003 were aggregated in several areas in the Bay of Fundy and dispersed over a broader area in the Gulf of Maine. Postsmolt distribution reflected the major surface-current vectors and was independent of origin (wild vs. hatchery, inner vs. outer Bay of Fundy). Migration proceeded without disruption, and marked wild postsmolts from both the inner and outer Bay of Fundy were recaptured in the outer Bay of Fundy and the Gulf of Maine, where their distribution overlapped the commercial fishery for Atlantic herring (Clupea harengus). Marked postsmolts of wild origin were recaptured more frequently than those of hatchery origin but the overall density was low, and no schools of postsmolts were encountered that could offer protection from predators. Temperature and salinity in postsmolt habitat were favourable for growth and survival. Postsmolts were in excellent condition and had no bacterial or viral pathogens or salmon lice (Lepeophtheirus salmonis). They were feeding on pelagic prey (amphipods, euphausiids, and fish larvae) and the period of accelerated marine growth had started, indicating that environmental conditions and food supply were not limiting growth and survival.

The early marine migration of 55 Atlantic salmon post-smolts tagged with acoustic transmitters was automatically monitored using 13 to 25 km long arrays of receivers deployed inside the Bay of Fundy, a coastal system on the east coast of Canada. The survival of post-smolts from groups with short- and long-term transmitters in coastal habitat up to 10 km from the river was 92 to 100%, indicating a successful transition to salt water and departure. Migration for 68 to 77% of post-smolts followed a direct route and it was rapid (transit time usually

Acoustic telemetry was used to monitor the early marine migration of Atlantic salmon Salmo salar from two rivers of Passamaquoddy Bay, a coastal system with numerous Atlantic salmon farms and weirs for Atlantic herring Clupea harengus on the border of Canada and the United States. Monitoring at fixed sites, active tracking, and systematic searches for tagged fish were combined. The migration success of hatchery-reared (N = 96) and wild (N = 38) smolts out of the estuaries was high (range, 90–97%), and the overall success of postsmolts moving out of Passamaquoddy Bay and into the several passages leading to the Bay of Fundy was reasonable (range, 71–88%). Estuary transit times were usually rapid (

The origin of Atlantic salmon Salmo salar adult returns from the ocean to the Magaguadavic River, New Brunswick, was determined for the 1996 smolt cohort by using scale examination of the freshwater–seawater transition zone and a discriminant function analysis based on scale measurements depicting the first year of growth in freshwater. Adult returns consisted of 57% farmed fish that escaped from sea cages, 34% wild fish that were the progeny of naturally spawned fish, and 9% farmed fish that were demonstrated to have escaped from hatcheries into the river as juveniles—the first report of farmed hatchery escapees into freshwater returning as adults. The analysis determined that 20% of returns previously thought to be wild were in fact farmed salmon that had escaped into freshwater from hatcheries. By comparison, using the same analysis, we determined that 51% of smolts from the same cohort migrating out to sea 1 and 2 years earlier were farmed escapees from hatcheries. The difference in proportio...

We examined the movements of flightless Long-tailed Ducks (Clangula hyemalis) during the wing molt in the near-shore lagoons of the Beaufort Sea in Alaska. Estimates of site fidelity during the 21-day flightless period ranged from 1-100%, with considerable variation among locations and within locations among years. There was no effect of low-level experimental disturbance or an underwater seismic survey on site fidelity of molting Long-tailed Ducks. Birds molting along a relatively consistent habitat gradient were more likely to move than those molting in a fragmented habitat. While flocks of birds are consistently observed in the same locations, these data suggest considerable turnover within these aggregations. These results, in conjunction with other studies, suggest that forage is relatively uniformly distributed within lagoons. We conclude that habitat selection by molting Long-tailed Ducks is likely influenced by protection from wind and associated waves.

The effects of intraperitoneally implanted dummy acoustic transmitters on juvenile Atlantic salmon Salmo salar of comparable size to wild presmolts and smolts were examined in two laboratory experiments. In the first experiment, different-sized tags (24, 28, and 32 mm × 8-mm diameter) that mimicked acoustic transmitters suitable for long-term studies were assessed. There was 60% mortality (3 of 5 fish) with the 32-mm implant early in the 316-d study and 20% mortality (1 of 5 fish) with the 28-mm implant. All fish surviving with 28- and 32-mm implants eventually expelled their tags, compared with only 20% of fish (1 of 5) with the 24-mm implant. Tag expulsion was not a cause of death. After implantation, tags were first encapsulated in a thick membrane and then expelled between 142 and 217 d after surgery, exiting at a site where pressure of the tag on the abdominal wall was greatest. Growth of tagged fish was initially delayed and lagged that of control and sham-tagged fish, but survivors from th...

Large numbers of Long-tailed Ducks (Clangula hyemalis) (10 000 – 30 000) undergo a postnuptial wing molt along barrier islands of the Beaufort Sea, Alaska. To investigate the potential effects of underwater seismic activities on this species, we monitored the number and diving behavior of molting Long-tailed Ducks before, during, and after seismic activities in a seismic area and two control areas nearby between July and September 2001. Aerial surveys documented a decline in duck numbers in both seismic and control areas during the period of seismic activity. We used automated data-collection computers to monitor the presence and diving behavior of radio-equipped Long-tailed Ducks residing within 2.5 km of a series of computer setups located along the barrier islands and on the mainland. A statistical analysis based on a modified before–after control–impact approach found no difference in indices of site fidelity or diving intensity between the seismic area and two control areas. Thus, we found no effect of seismic activity on movements and diving behavior of molting Long-tailed Ducks. These results should be evaluated carefully, however, as logistical and ecological factors limited our ability to detect more subtle disturbance effects. We recommend additional studies on other bird species to fully understand the effects of underwater seismic testing.

A procedure was developed to identify whether the natal origin of juvenile Atlantic salmon Salmo salar in the Magaguadavic River, New Brunswick, was farmed or wild. Farmed juveniles enter this river as escapees from commercial hatcheries. The discriminant function was developed using measured scale characteristics for the first year of growth, as determined from samples of farmed and wild juvenile Atlantic salmon of known origin. Eight scale characteristics proved to be significant predictors of origin. In a jackknife cross-validation, the discriminant function was 90% accurate in predicting the origin of juvenile Atlantic salmon in the Magaguadavic River. The procedure was then applied to juvenile Atlantic salmon of unknown natal origin sampled from the Magaguadavic and neighboring Waweig and Digdequash rivers, which also support salmon hatcheries. Of the juvenile Atlantic salmon sampled in the Magaguadavic River in 1996, 1997, and 1998, 36, 59, and 43%, respectively, were estimated to be of far...

We developed a model that simulates the effects of changes in sulphate (SO42-) deposition on the chemistry of naturally organic-rich streams, linked this chemical model to a model of Atlantic salmon (Salmo salar) production (Korman et al. 1994. Can. J. Fish. Aquat. Sci. 51: 662-680), and assessed its performance on three acidified streams in southwest Nova Scotia. The chemical model closely tracked current chemistry by estimating the charge density required for charge balance on each sampling date. Calculated charge densities were generally low (1-3 µequiv./mg dissolved organic carbon (DOC)), inversely related to DOC, and positively related to pH. Predictions of minimum pH and salmon smolt output were relatively insensitive to the assumed F-factor (watershed neutralization of deposited acidity) in the parameter range most likely for the three streams. The model permits rapid impact assessment of acid deposition scenarios with a modest amount of input data (acid-neutralizing capacity, pH, SO42-, and DOC, ideally sampled weekly) while retaining natural cycles and processes.

Cultured Atlantic salmon (Salvo s&r) that escaped from sea cages and migrated into the Magaguadavic River, New Brunswick, often showed no external signs of sexual maturation over the period 1992-1996. The sequential changes in plasma testosterone (T), 1 I-ketotestosterone (1 I-KT), and 17l.Gestradiol (E2) were determined in escaped cultured salmon in 19941996 and in wild Atlantic salmon in 1996 to evaluate reproductive status before, during, and after the spawning period. T in males and females, 1 I-KT in males, and E2 in females increased from basal levels in summer to peak values just before spawning in late autumn in all wild salmon. In contrast, there was an absence of change in gonadal steroids from basal levels either during or after the spawning period in the majority (85%) of escaped cultured salmon, indicating that these fish would not spawn later during the year of entry into fresh water. However, 11% of cultured fish were males with steroid profiles that showed a maturation synchronous with that of wild females, indicating that some interbreeding could occur. In 1996, almost half of these cultured males were precociously mature post-smelts. 0 1997 International Council for the Exploration of the Sea

High numbers of non-maturing, cultured Atlantic salmon that escaped after one winter in sea-cages ascended into fresh water in the Magaguadavic River, New Brunswick. Acoustic telemetry was used to investigate the movements and behaviour of 14 of these fish in the river over the natural spawning period. Four of the fish remained in deep, slow areas within 1 km of the dam, five moved less than 10 km upstream, and five moved no further than 17.5 km. They then remained at these sites for the rest of the study. Thus, all fish failed to reach the known spawning areas located further upstream. It is presumed that the limited movement of the cultured fish was related to their failure to sexually mature. Why these non-maturing salmon entered fresh water remains unanswered, but their residence in the river could have ecological implications.

The origin of Atlantic salmon (Salmo salar) in the smolt migration from the Magaguadavic River, New Brunswick, was examined to assess the importance of losses of juveniles from hatcheries and the potentialimpact on the wild stock. Three hatcheries that produce over two million smolts annually for the aquaculture industry are located along the river. Smolts were sampled at the mouth of the river over a 1-month period. Two methods were used to determine their origin: (1) external appearance of fins and size at a given age, and (2) a discriminant function analysis comparing number of circuli in the first year on scales and back-calculated length at age 1 to those of fish of known wild and hatchery origins. The two methods indicated that 23.4-39.6% of smolts were of wild origin, 9.4% were hatchery releases, and 51.0-67.2% were juvenile escapees. The fin and size method predicted that more smolts in the run were of escaped hatchery origin than classified by the discriminant function analysis. Many of these were large 1-year-old smolts. Smolts of hatchery origin were significantly larger than wild smolts and could benefit from increased early marine survival. This study indicates that the potential impact of juvenile salmon that escape or are accidentally released in rivers has probably been underestimated.

Application of crushed limestone on the bed of an acidic brook enhanced Atlantic salmon (Salmo salar) spawning habitat, and the mitigation strategy resulted in improvements in the survival of juvenile Atlantic salmon and brook trout (Salvelinus fontinalis). There was a small, lasting increase in pH in the limed section of the brook and downstream over 8 yr. Limestone was replenished once after 4 yr because of washouts during floods; otherwise, requirements for maintenance were low. After liming, Atlantic salmon consistently dug most redds in the limed section, but this preference was possibly related to physical enhancement of spawning areas rather than to high pH. Liming resulted in a twofold increase in the number of occasions where more than a few juvenile Atlantic salmon survived severe acidic episodes in the brook. Brook trout were tolerant of lower pH episodes than juvenile salmon but, like salmon, they also responded to changes in minimum pH as a result of liming. Densities of age–0 salmon and brook trout were related to seasonal and interannual variability in pH, but they were always greater in the limed section than in the unlimed, control section upstream, especially at times when the difference in pH between sections was the largest. Resume : L’application de calcaire concasse dans le lit d’un ruisseau acide a ameliore l’habitat de reproduction du saumon atlantique (Salmo salar), et la strategie de compensation a fait beaucoup pour la survie des juveniles du saumon atlantique et de l’omble de fontaine (Salvelinus fontinalis). On a constate une augmentation legere mais durable du pH dans la section chaulee du ruisseau ainsi qu’en aval pendant huit ans. Il a fallu rajouter du calcaire une fois apres quatre ans pour reconstituer celui qui avait ete entraine par les crues; ceci mis a part, les besoins d’entretien ont ete minimes. Apres le chaulage, le saumon atlantique a regulierement creuse la plupart de ses nids de fraye dans la section chaulee, mais cette preference dependait peut-etre plus de l’amelioration physique des frayeres que du pH eleve. Le chaulage a multiplie par deux les cas ou un nombre non negligeable de saumons atlantiques juveniles ont survecu a de graves episodes d’acidite dans le ruisseau. L’omble de fontaine a mieux tolere les episodes de pH plus faible que le saumon juvenile, mais comme le saumon, il a egalement reagi aux changements du seuil minimal de pH apportes par le chaulage. La densite du saumon et de l’omble de fontaine d’âge zero etait tributaire de la variabilite saisonniere et interranuelle du pH, mais elle etait toujours plus forte dans la section chaulee que dans la section temoin non chaulee situee en amont, surtout aux moments ou la difference de pH entre les sections etait la plus grande. [Traduit par la Redaction]

The movements of 24 hatchery-reared Atlantic salmon Salmo salar smolts, with miniature acoustic transmitters (pingers) implanted surgically, were determined after release in the coastal waters of Passamaquoddy Bay (mean tide range 6 m), New Brunswick, Canada, to describe the first stages of seaward migration. Automated pinger detection at fixed sites, and pinger location and tracking by boat were used. Post-smolts left the release area rapidly, and the majority moved to open waters of the bay within several tidal cycles. Initially, post-smolts moved with a seaward orientation on ebb tides and held positions on flood tides. Their movements into open waters were diurnal, and the timing corresponded with the state of the tide during which they moved through a narrow channel. Post-smolts moved preferentially through this passageway with the aid of the tidal stream. Successful movements out through the channel occurred during ebb tides and any movements back in were during flood tides. Ground speed of fish moving through the channel was 4·2 body lengths s−1 and faster than the tidal stream velocities in the channel. The relative velocity of fish swimming through the channel was 2 body lengths s−1. Post-smolt movement was indicative of active, directed swimming with a reliance on ebb-tide transport for migration through a coastal area with strong tidal currents. Some post-smolts moved seaward directly with no apparent period of acclimation for the transfer to the marine environment, whereas others delayed their departure. These differences in behaviour were probably related to asynchrony in smolting when fish were released.

Microhabitat use by brook trout Salvelinus fontinalis and juvenile Atlantic salmon Salmo salar in a small acidic brook was examined in response to the acidification episodes typical of rivers of southwest Nova Scotia in the fall, and to a longitudinal pH gradient related to liming. Several microhabitat variables were measured for age-0 and age-1 and older fish of both species. Some of the measurements were made relative to the fish's focal point (height of the fish above the bottom) and included water depth and focal elevation, focal water velocity, focal water pH and temperature, and bed material grain size. The presence of a small, longitudinal pH gradient ( 1 pH unit; final pH

From mid-July through September, 10 000 to 30 000 Long-tailed Ducks (Clangula hyemalis) use the lagoon systems of the central Beaufort Sea for remigial molt. Little is known about their foraging behavior and patterns of habitat use during this flightless period. We used radio transmitters to track male Long-tailed Ducks through the molt period from 2000 to 2002 in three lagoons: one adjacent to industrial oil field development and activity and two in areas without industrial activity. We found that an index to time spent foraging generally increased through the molt period. Foraging, habitat use, and home range size showed similar patterns, but those patterns were highly variable among lagoons and across years. Even with continuous daylight during the study period, birds tended to use offshore areas during the day for feeding and roosted in protected nearshore waters at night. We suspect that variability in behaviors associated with foraging, habitat use, and home range size are likely influenced by availability of invertebrate prey. Proximity to oil field activity did not appear to affect foraging behaviors of molting Long-tailed Ducks.

We developed an age-structured simulation model incorporating pH-dependent mortality to assess impacts of acidification on Atlantic salmon (Salmo salar) populations at the reach and river system level. Applied to the LaHave River, Nova Scotia, acidic reaches (mean annual pH 4.6–5.1) were predicted to have 0–15% of the annual smoit production and 0–31% of the maiden spawner production compared with circumneutral reaches (pH ≥ 5.6) and increased juvenile growth due to lower parr densities. The benefit of increased growth (earlier age of smoltification and increased early marine survival) was not sufficient to outweigh impacts of higher freshwater juvenile mortality. Simulated removal of acidic conditions resulted in a 41% increase in recruits, but only after several decades following complete chemical recovery. Circumneutral reaches were predicted to be 4–12 times more efficient at producing smolts and 3–7 times more efficient at producing adults from hatchery fingerlings compared with acidic reaches. To maintain current target egg deposition rates of 240 eggs/100 m2, circumneutral reaches could withstand grilse exploitation rates of up to 65%, while acidic reaches, even without harvesting mortality, could not maintain this level. Fisheries management strategies need to account for variability in freshwater production both within and between river systems.

The effect of citrate as organic acid anions (A−) on the accumulation of aluminum (Al) on gills of Atlantic salmon (Salmo salar) fry was examined in acidic media. Treatments with (Al−A−) = +10, 0, and −10 μeq/1([Al] = 0, 10, 20, 30, 40, 50, 60 μeq/1 and [citric acid] = 0, 10, 20, 50 μeq/1) were used. Depuration of gills loaded with Al (10 μeq/l) was also examined in the presence of citric acid (0, 10, 20, 40 μeq/l). Elimination of Al from gills was a much more rapid process (

This study was undertaken to investigate the nature and microheterogeneity of the carbohydrate moiety of the Fc epsilon receptors of RBL-CA10 and RBL-CA10.7 cells. Treatment using the glycosylation processing inhibitors, castanospermine (CN), 1-deoxymannojirimycin (DMJ), and swainsonine (SW) resulted in a decrease of the relative molecular mass (M(r)) of both the alpha-chain of the high affinity receptor for IgE, Fc epsilon RI(alpha), and the low affinity receptor for IgE, Fc epsilon RL. Exposure to DMJ had the greatest effect on the M(r), while CN seemed to lead to a decreased cell surface expression of Fc epsilon RI. Both receptors are largely resistant to endoglycosidase H as their M(r) decreased only by approximately 2 kDa. These results suggest that both receptors are composed primarily of complex oligosaccharides with a single high mannose, N-glycosylated site. Both Fc epsilon receptors become endoglycosidase H sensitive if first exposed to DMJ which indicates that the carbohydrate composition is indeed altered by this processing inhibitor presumably by blocking the formation of complex structures. When the Fc epsilon receptors were reduced and hydrolyzed by N-glycanase, the M(r) values for Fc epsilon RI(alpha) and Fc epsilon RL decreased to approximately 28 and 34-38 kDa respectively. In the case of Fc epsilon RI(alpha), this implies the presence of only a small amount of O-linked oligosaccharides.

It is widely appreciated that there is significant inter-individual variability in pain sensitivity, yet only a handful of contributing genetic variants have been identified. Computational genetic mapping and quantitative trait locus analysis suggested that variation within the gene coding for the beta3 subunit of the Na+,K+-ATPase pump (Atp1b3) contributes to inter-strain differences in the early phase formalin pain behavior. Significant strain differences in Atp1b3 gene expression, beta3 protein expression, and biophysical properties of the Na+,K+ pump in dorsal root ganglia neurons from resistant (A/J) and sensitive (C57BL/6J) mouse strains supported the genetic prediction. Furthermore, in vivo siRNA knockdown of the beta3 subunit produced strain-specific changes in the early phase pain response, completely rescuing the strain difference. These findings indicate that the beta3 subunit of the Na+,K+-ATPase is a novel determinant of nociceptive sensitivity and further supports the notion that pain variability genes can have very selective effects on individual pain modalities.

An increasing amount of evidence indicates that there are significant sex differences in clinical and experimental pain sensitivity in men and women. While it is now clear that the endogenous sex steroids are involved in mediating these sex differences, the cellular and molecular mechanisms that underlie their effects on nociceptive sensitivity remain elusive. Recent studies have shown that sex steroids are potent regulators of gene expression in glial cells, particularly astrocytes. This review specifically highlights some of the evidence of sex steroid regulation of growth factor expression. Growth factors have been shown to be potent pro-nociceptive mediators in rodents. Thus, regulation of their expression by sex steroids may be a general mechanism by which sex steroids exert their effect on pain sensitivity. One such mechanism, the progesterone specific regulation of the growth factor, neuregulin-1, following nerve root injury in the rat, is described in detail. Neuregulin-1 expression is increased in spinal cord astrocytes only in female rats with circulating progesterone. Neuregulin-1 has also been shown to produce transient tactile allodynia when delivered intrathecally in rats. Our understanding of growth factor regulation by sex steroids promises to open up new avenues of investigation into the mechanisms that drive sex differences in pain sensitivity.

Glial−neuronal interactions are crucial processes in neuromodulation and synaptic plasticity. The neuregulin 1 family of growth and differentiation factors have been implicated as bidirectional signaling molecules that are involved in mediating some of these interactions. We have shown previously that neuregulin 1 expression is regulated by the gonadal hormones progesterone and 17β-estradiol in the CNS, which might represent a novel, indirect mechanism of the neuromodulatory actions of these gonadal hormones. In the present study, we sought to determine the effects of progesterone and 17β-estradiol on neuregulin 1 expression in rat cortical astrocytes and neurons in vitro. We observed that progesterone increased the expression of neuregulin 1 mRNA and protein in a dose-dependent manner in cultured astrocytes, which was blocked by the progesterone receptor antagonist RU-486. In contrast, 17β-estradiol did not increase either neuregulin 1 mRNA or protein in astrocytes. We observed no effect of either progesterone or 17β-estradiol on neuregulin 1 mRNA and protein in rat cortical neurons in vitro. Finally, we observed that treatment of cortical neurons with recombinant NRG1-β1 caused PSD-95 to localize in puncta similar to that observed following treatment with astrocyte-conditioned medium. These results demonstrate that progesterone regulates neuregulin 1 expression, principally in astrocytes. This might represent a novel mechanism of progesterone-mediated modulation of neurotransmission through the regulation of astrocyte-derived neuregulin 1.

We have previously shown that the atypical methylxanthine, propentofylline, reduces mechanical allodynia after peripheral nerve transection in a rodent model of neuropathy. In the present study, we sought to determine whether propentofylline-induced glial modulation alters spinal glutamate transporters, glutamate transporter-1 (GLT-1) and glutamate-aspartate transporter (GLAST) in vivo, which may contribute to reduced behavioral hypersensitivity after nerve injury. In order to specifically examine the expression of the spinal glutamate transporters, a novel line of double transgenic GLT-1-enhanced green fluorescent protein (eGFP)/GLAST-Discosoma Red (DsRed) promoter mice was used. Adult mice received propentofylline (10 mg/kg) or saline via i.p. injection starting 1 h prior to L5-spinal nerve transection and then daily for 12 days. Mice receiving saline exhibited punctate expression of both eGFP (GLT-1 promoter activation) and DsRed (GLAST promoter activation) in the dorsal horn of the spinal cord, which was decreased ipsilateral to nerve injury on day 12. Propentofylline administration reinstated promoter activation on the injured side as evidenced by an equal number of eGFP (GLT-1) and DsRed (GLAST) puncta in both dorsal horns. As demonstrated in previous studies, propentofylline induced a concomitant reversal of L5 spinal nerve transection-induced expression of glial fibrillary acidic protein (GFAP). The ability of propentofylline to alter glial glutamate transporters highlights the importance of controlling aberrant glial activation in neuropathic pain and suggests one possible mechanism for the anti-allodynic action of this drug.

Sex differences in the magnitude of response to thermal and tactile stimuli have been demonstrated in both clinical and animal studies. Female rats typically display lower thresholds to painful stimuli and display more robust responses following nerve injury as compared with males. There is a body of evidence implicating the sex hormones in mediating this sex difference. In the present study, we sought to determine which gonadal hormones were involved in mediating the observed female hypersensitivity in female rats both prior to and following experimental nerve root injury using a chronic hormone replacement paradigm. Female rats were ovariectomized and hormone pellets containing 17β-estradiol, progesterone (P), 17β-estradiol+progesterone or placebo were implanted s.c. Our results demonstrate that only the group of female rats that received progesterone alone maintained the hypersensitive phenotype following ovariectomy, compared with gonadally intact male rats. This result was observed both in response to thermal stimuli in non-injured female rats and to thermal and tactile stimuli following L5 nerve root ligation, a model of low back pain associated with lumbar radiculopathy. Postmortem analysis of serum gonadal hormone concentrations demonstrates that the hormonal manipulations were successful and the exogenous hormones were similar to physiological levels observed in the sham-ovariectomized controls. Taken together, these results demonstrate the critical role for progesterone in mediating enhanced female tactile and thermal hypersensitivity following L5 nerve root ligation.

Glial cells function in maintenance of homeostasis as well as in pathophysiology. In this study, we determined the time course of spinal glial cell activation during the development of morphine analgesic tolerance in an L5 spinal nerve transection rodent model of neuropathic pain. We also sought to assess whether the method of morphine administration affected neuroimmune activation at the levels of transcription and translation. Rats received L5 spinal nerve transection or no surgery on day 0. On day 6 post-transection, osmotic minipumps were implanted to deliver saline or morphine s.c. (1 or 10 mg/kg) or i.t. (5 or 20 nmol/h). Mechanical allodynia developed immediately after spinal nerve transection; this hypersensitivity was reversed with both low- and high-dose morphine by either route. Tolerance to antiallodynia developed after 3 days of i.t. morphine and after 6 days of s.c. morphine, indicating hastened tolerance following i.t. delivery. Analysis of mRNA revealed that s.c. morphine treatment did not lead to increases in glial activation markers. In contrast, i.t. morphine caused a biphasic alteration in glial fibrillary acidic protein (GFAP) and integrin alpha M mRNA. Protein levels for GFAP were elevated after s.c. and i.t. administration of morphine; however, induction was further enhanced in the latter group. Here, we show for the first time that there is differential recruitment of transcriptional and translational mechanisms of glial activation by systemic and i.t. morphine. Furthermore, we suggest that enhanced neuroimmune activation after i.t. dosing contributes to the hastened development of analgesic tolerance seen in these animals.

Considerable evidence exists for sex differences in human pain sensitivity. Women typically report a higher incidence of various painful conditions and report that the conditions are more painful when compared to men. In the present study, we sought to determine whether sex differences in pain sensitivity are observed using a lumbar radiculopathy model of low back pain in the rat and whether removal or alteration of gonadal hormones at specific timepoints can modulate these sex differences. Pubertal and adult male and female Sprague-Dawley rats were castrated 2 or 6 weeks prior to L5 nerve root injury to determine the activational hormonal effects. In a separate study, neonatal male and female Sprague-Dawley rats were either castrated or injected with testosterone, respectively, on postnatal day one to determine the organizational effects of gonadal hormones on L5 nerve root injury-induced behavioral hypersensitivity. Our results demonstrate that there was a statistically significant sex difference in the magnitude of mechanical allodynia and thermal hyperalgesia following experimentally induced radiculopathy in the rat: females demonstrated decreased thresholds to tactile and thermal stimuli as compared to males. Furthermore, the enhanced female hypersensitivity was reversed in pubertal and adult animals ovariectomized 6 weeks, but not 2 weeks prior to L5 nerve root injury. Our results demonstrate that the activational effects of gonadal hormones mediate the enhanced female tactile and thermal hypersensitivity following L5 nerve root injury. These results suggest that manipulation of gonadal hormones may be a potential source for novel therapies for chronic pain in women.

Crushed limestone (200 tonnes) was spread in bars on the bed of an acidic brook (mean pH 5·0) in Nova Scotia, Canada. A seasonally variable but significant increase in pH of running water resulted, and a longitudinal pH gradient over the limed section extended to the mouth of the brook. The effectiveness persisted after 3 years, during which pH downstream of the limestone increased an average of 0·4 pH units (range

Along the central Beaufort Sea, Pacific Common Eiders (Somateria mollissima v-nigra) nest on unvegetated, barrier islands; often near nesting Glaucous Gulls (Larus hyperboreus). Nest-site choice likely reflects a strategy of predator avoidance: nesting on islands to avoid mammalian predators and near territorial gulls to avoid other avian predators. We observed a nesting colony of Common Eiders from first nest initiation through nesting termination on Egg Island near Prudhoe Bay, Alaska (2002 – 2003). Resident gulls depredated many eider nests, mostly during initiation. All nests failed when an Arctic Fox (Alopex lagopus) visited the island and flushed hens from their nests, exposing the eggs to depredation by the fox and gulls (resident and non-resident). Common Eiders actively defended nests from gulls, but not from foxes. Likely all three species (i.e., eiders, gulls, and foxes) ultimately achieved negligible benefit from their nest-site selection or predatory activity: (a) island nesting provided no safety from mammalian predators for eiders or gulls, (b) for Common Eiders, nesting near gulls increased egg loss, (c) for Glaucous Gulls, nesting near colonial eiders may have reduced nest success by attracting the fox, and (d) for Arctic Foxes, the depredation was of questionable value, as most eggs were cached and probably not recoverable (due to damage from fall storms). Thus, the predator-prey interactions we observed appear to be a case where little or no fitness advantage was realized by any of the species involved.

Barrow's Goldeneyes (Bucephala islandica) and Surf Scoters (Melanitta perspicillata) were observed on four separate occasions, by three different observers, foraging on Bay Mussels (Mytilus trossulus) above the water surface. This unique foraging behaviour could be attributed to diurnal spring tides and reduced lower intertidal mussel abundance.

Molt-4 rho(0) (Molt-4 0) cells are a pyruvate and pyrimidine auxtophic cell line derived from Molt-4 cells, a T-cell lymphoblastic leukemia cell line. The ρ0 mutant cells were generated by continuous long-term (28 day) incubation of Molt-4 wild-type (Molt-4 WT) cells in ethidium bromide (50ng/ml) supplemented with uridine and pyruvate. The absence of mitochondrial DNA (mtDNA) in the Molt-4 ρ0 cells has been confirmed by Southern analysis and PCR. The objective of these experiments was to determine the effects on nuclear gene expression of deleting mtDNA in this cell line compared to the wild-type control. RNA was purified from both cell lines using Qiagen RNeasy columns. The methods for generation of fragmented biotin-labeled cDNA, hybridization to Affymetrix human genome U133A gene chips, washes, streptavidin phycoerythrin staining, and scanning were per the Affymetrix protocol. Microarray data was then analyzed using the software program GeneTraffic and genes that were expressed ≥ or ≤ H4 fold compared to the Molt-4 WT were identified. Confirmation of expression is ongoing via RT-PCR and Western-blot analysis. Data analysis suggested that, in Molt-4 ρ0 cells, 16 gene probes were up regulated and 6 were down regulated compared to Molt-4 WT. The majority of up-regulated genes in the Molt-4 ρ0 cells identified are critical to stress-induced survival pathways and included VEGF, FGFR1, ATF5 and SCL7A11 while down regulated gene expression appeared to be related to inhibition of differentiation (CD2, DNTT) or inhibition of apoptosis (EIF5A). Molt-4 ρ0 cells appear to attempt to survive via up regulation of stress-induced survival gene transcription while down regulating transcription of differentiation and apoptotic genes. Confirmation of our results via RT-PCR and Western-blot analysis is ongoing and will be presented. Clinical Pharmacology & Therapeutics (2004) 75, P17–P17; doi: 10.1016/j.clpt.2003.11.064

Toxicity of different pH levels to Atlantic salmon (Salmo salar) parr held in floating pens for 54 d was assessed in four acidic streams of Atlantic Canada during the autumnal episode of increasing acidity. All parr died in the two streams where pH levels decreased below pH 4.7. Mortality was related to the rate of pH change and to parr size. Plasma sodium and chloride concentrations decreased by about 50–70 mmol∙L−1in parr of these two streams, and the rate of electrolyte loss was related to the rate and severity of pH change. In the other two streams, pH levels were never lower than pH 4.8 and no fish died. Plasma sodium and chloride concentrations in these parr decreased by 20–30 mmol∙L−1, but only after 30 d of exposure. Increased hematocrit, increased respiratory–cough response, and decreased feeding response, especially for parr in the most acidic streams, were also the result of stress apparently related to decreasing pH levels. Concentrations of labile aluminum were usually less than 10% of total dissolved aluminum and always less than 50 μg∙L−1in the four streams. Accumulation of aluminum in the gills of parr was not a significant factor in the lethal effects observed, which were more likely due to low pH.

The expression of leghaemoglobin genes in effective and ineffective (unable to fix nitrogen) root nodules of soybean developed by Rhizobium japonicum strains 61A76, 61A24 and SM5 was measured by using a cDNA probe or a cloned leghaemoglobin sequence and in vitro translation of Lb-mRNA. Hybridization of the poly(A)-containing nodule polysomal RNA from 3-week-old nodules with a kinetically purified Lb-cDNA or with plasmid (pLbl) containing a leghaemoglobin sequence showed that Lb-mRNA is present in ineffective nodules formed by strains SM5 and 61A24 at reduced levels. Of the two major classes of electrophoretically distinguishable leghaemoglobins in soybean, LbS was not synthesized in 3-week-old strain 61A24-induced nodules while both sorts of leghaemoglobin were synthesized and accumulated in ineffective nodules formed by strain SM5 of Rhizobium. Ineffective nodules formed by strain 61A24 are green inside and do not appear to accumulate leghaemoglobin as measured by the haemochromogen assay, although low levels of apoleghaemoglobin were detected using leghaemoglobin antibodies. SM5-induced nodules were found to have about half as much as leghaemoglobin of the of effective (61A76-induced) nodules. This study demonstrates that while the appearance of leghaemoglobin is independent of nitrogenase activity in bacteroids, its synthesis is influenced to different degrees both by a mutation (SM5) and incompatibility (61A24) of Rhizobium. The primary regulation appears to be at the level of transcription or processing of mRNA since ineffective nodules contain Lb-mRNA approximately in proportion to the amount of apoleghaemoglobin present in these nodules.

Ecological and toxicological data from field studies on acidic rivers of Nova Scotia were examined to review the effects of low pH on Atlantic salmon (Salmo salar) populations in waters rich in organic acids where noexchangeable forms of Al dominate at all times. There were no survival of salmon past the dry stage at pH 4.9. Annual production of juvenile salmon and potential yield of smolts were lower at pH 4.7 to 5.4 than at pH 5.6 to 6.3 because of reduced densities attributable to the high mortality of fry at pH ≤5.0. However, acidity episodes to pH

Atlantic salmon (Salmo salar) smolts migrating from two acidic rivers (pH 4.9 and 5.2) had high hematocrit levels (> 50%) and low plasma [Cl−] (−1). The hematocrit level was 10% higher and plasma [Na+] was 17% lower in smolts of the more acidic of the two rivers. Salmon parr in rivers of mean pH 5.0, 5.4, and 6.0 over a 7-month period had high hematocrit levels (> 40%) and low plasma [Cl−] (−1). Plasma [Na+] and [Cl] were both slightly less (~ 5%) and plasma [K+] was higher (> 1.5 times) in parr from the river of pH 5.0 than in those from the other two rivers. Atlantic salmon smolts were more sensitive to low pH (plasma [Na+] 14% less, [Cl] 17% less, and hematocrit level 37% higher) than parr, and parr of the 0+ age-class were more sensitive (plasma [Na+] 9% less) than 1+ parr. Prespawning white suckers (Catostomus commersoni) and alewives (Alosa pseudoharengus) migrating in a river at pH 4.9 had high hematocrit levels and low plasma [Cl−], and alewives (hematocrit, 66%; plasma [Cl], 65 mequiv. L−1) were more severely affected than suckers (hematocrit, 42%; plasma [Cl−], 91 mequiv. L−1). Plasma [Ca2+] in females of both species was not greatly elevated relative to males (female/male [Ca2+] = 1.21 in suckers and 1.14 in alewives), suggesting a possible impairment of calcium metabolism associated with ovarian development. The physiological effects observed in fish inhabiting soft waters (external [Ca2+] −1) at pH levels of about 5.0 generally correlated well with the laboratory "models" of acid exposure in soft water.

The occurrence, density, and age-class structure of endemic fish species were compared over a period of 24 months in three Nova Scotia streams of differing pH. The absence of acid-sensitive species and very low densities of fish characterized the stream with a pH range of 4.5–5.0. Fish densities were lower in the stream with a pH range of 4.7–5.4 than in the stream with a pH range of 5.6–6.3. Juvenile salmon and cyprinids were the most abundant species in the least acidic stream. Their densities were considerably lower in the stream with pH levels of 4.7–5.4, and the young age-classes of the cyprinid species were rare or absent. Both salmon and cyprinids were absent in the most acidic stream. In contrast, American eels were most abundant in the two streams with pH levels less than 5.5, and they accounted for an increasingly large proportion of the fish biomass at the lowest pH levels. White sucker was the most abundant species at the lowest pH levels, but its contribution to biomass was unimportant because of the absence of most age-classes older than 0+. Several other species found in the most acidic stream were not very abundant, and old age-classes were usually absent for most of these. The observed distributional patterns were considered to be mostly pH related.

Mortality of Atlantic salmon alevins in solutions containing Al and dissolved organic anions (both synthetic and natural) was correlated with Al accumulation in alevin tissues. Both mortality and accumulation could be related to the concentration differences between Al and organic anions. Mortality and body accumulation of Al both increased dramatically as total Al concentrations increasingly exceeded organic anion concentrations. Alevin growth and yolk utilization were both less rapid at inorganic monomeric Al concentrations exceeding 2 μM (50 μg L-1). The acidic fractions of dissolved organic matter (DOM) are more effective in protecting alevins against Al toxicity than are the neutral and basic fractions. Ambient inorganic monomeric Al is probably not toxic to salmon alevins in acidic Nova Scotian streams, even during snow-melt.

Densities, growth, and production of juvenile Atlantic salmon (Salmo salar) were estimated at sites in two acidic rivers of different pH, the Westfield and North rivers, in Nova Scotia, Canada, from 1982 to 1984. Annual production was significantly lower in the more acidic Westfield River (−2∙yr−1 at pH 4.7–5.4) than in the North River (1.4 g∙m−2∙yr−1 at pH 5.6–6.3). Low production rates in the more acidic river were attributable to the lower densities and poorer survival of juveniles at the lower pH levels. Low densities of parr in the more acidic river were a function of the high initial mortality of postemergent fry, and the mortality of parr during periods of pH minima such as over winter. Marking and recapture information and trapping at a weir for counting migrating fishes indicated that there was little emigration of parr other than in the spring when some movements occurred preceding and during smoltification. Average potential yield of 2-yr smolts was 0.8 smolt/100 m2 in the Westfield River and in the range of 2.7–6.6 smolts/100 m2 at higher pH levels in the North River. Growth was not limiting to production at the lower pH levels. After the first winter, 1-yr-old parr were much larger at the lower pH than they were at less acidic pH levels, the faster growth possibly resulting from the lower density of parr at the lowest pH. A temperature-related biphasic growth of 1-yr-old parr with periods of maximum growth in spring and autumn was recorded. Reduced production, a result of deleterious effects of low pH on survival and density in the Westfield River was probably sufficient to prevent the continued maintenance of a naturally produced salmon population in that river, whereas production at higher pH levels in the North River was comparable to that in near-neutral waters of other areas.

Eggs of Atlantic salmon (Salmo salar) were incubated in spawning areas of five streams of mean pH 4.6–6.5. Hatching success (36.6–88.7%) for eggs planted after fertilization in the natural substrate of four acidic streams was highly correlated with the pH (4.5–5.0) of interstitial water, and the LL50 was about pH 4.7. Dissolved oxygen concentrations (>6.0 mg∙L−1) in the interstitial water in these streams were probably not limiting to embryos before hatching. In a near-neutral stream (pH 6.5), the comparatively lower hatching success (5.6–77.0%) was significantly correlated with minimum dissolved oxygen concentration (1.4–9.2 mg∙L−1) in the interstitial water, and the mean survival of embryos was very low (16.2%) at oxygen concentrations −1. Conditions in the substrate where eggs were incubated until hatching were representative of those in natural salmon redds. In one of the acidic streams (pH 4.8), dissolved oxygen concentrations in the interstitial water were low (2.0–7.6 mg∙L−1) after the hatch, and the emergence of salmon fry from natural redds was minimal, which indicated a low survival of alevins. Estimates of critical pH levels for salmon embryos differ between the laboratory and field approach and are probably site specific because survival in acid waters is determined by acidity, related chemical factors, and changes in water quality within the redd environment.