Miramichi River Research Articles

Effects of environmental factors on ichthyoplankton communities in the Miramichi estuary, Gulf of St Lawrence

Ichthyoplankton in 20 taxa (17 identified to species, three to genus) representing 14 families were collected in 10 surveys of the Miramichi estuary between May and September 1992. The taxonomic composition was typical of other estuaries in the Gulf of St Lawrence and Gulf of Maine. Larvae of three anadromous species [rainbow smelt (Osmerus mordax), alewife (Alosa pseudoharengus) and blueback herring (Alosa aestivalis)] were several orders of magnitude more abundant than any other taxon. The upper estuary (Miramichi River and its tributaries) probably serves as a nursery ground for larvae of these species and others such as Atlantic tomcod (Microgadus tomcod). The species composition of the lower estuary (Miramichi Bay) was dominated by typically marine forms and probably serves as a nursery ground for winter flounder (Pleuronectes americanus), smooth flounder (Pleuronectes putnami). sculpin (Myoxocephalus sp ) and sand lance (Ammodytes sp) Of the environmental factors investigated, salinity was the most useful predictor of larval distribution in the estuary.

A Biomarker Approach to Assessing Xenobiotic Exposure in Atlantic Tomcod from the North American Atlantic Coast

We determined levels of hepatic cytochrome P4501A (CYP1A) mRNA, hepatic DNA adducts, and fluorescent aromatic compounds (FACs) in bile, a measure of exposure to polyaromatic hydrocarbons, in Atlantic tomcod from six river systems ranging from highly polluted to relatively pristine on the northeast North American coast (the Hudson River, New York; the St. Lawrence River, Quebec; the Miramichi River, New Brunswick; the Saco and Royal rivers, Maine; and the Margaree River, Nova Scotia). Hudson River tomcod showed the greatest response for all parameters, and tomcod from the Margaree River exhibited the least response. Tomcod from the Miramichi River exhibited marked induction of CYP1A mRNA but low levels of hepatic DNA adducts and biliary FACs, whereas fish from the St. Lawrence River showed no induction of CYP1A mRNA and moderately elevated levels of DNA adducts and biliary FACs. In tomcod from the Hudson and Miramichi rivers, the levels of CYP1A mRNA were 28 times and 14 times, respectively, as great as the levels in fish from the St. Lawrence, Saco/Royal, and Margaree rivers. Mean levels of DNA adducts varied from 120 nmol adducts/mol bases in Hudson River tomcod to < 3 nmol adducts/mol bases in fish from the Miramichi and Margaree rivers. Concentrations of FACs in the bile of tomcod from the Hudson and St. Lawrence rivers were 8 and 1.8 times, respectively, as great as the concentrations in tomcod from the Miramichi River and Margaree River. In tomcod from the Hudson River, all three biomarkers were markedly elevated; in the St. Lawrence River two biomarkers were elevated, in the Miramichi River one was elevated, but no biomarker was substantially elevated in fish from the Saco/Royal and Margaree rivers. Elevated levels of hepatic DNA adducts and biliary FACs in tomcod from the Hudson River suggest increased exposure to PAHs, consistent with previous studies.

Association between the Regulatory LocusPGM-1r* and Life-history Types of Juvenile Atlantic Salmon (Salmo salar)

We sampled three juvenile life-history types of Atlantic salmon (Salmo salar) from Western Arm Brook, Newfoundland, to test whether a regulatory gene variant PGM-1r*b is associated with accelerated life-history development. Seven nonmigratory parr populations from the Miramichi River, New Brunswick, and the Margaree River, Nova Scotia, were also sampled. Previous studies with rainbow trout (Oncorhynchus mykiss) indicate that the liver-specific regulatory gene variant PGM-1r*b is associated with faster embryonic and life-history development. We found no association between variation at PGM-1r* and body weight, fork length, gonadal development, and smolt age. However, the frequency of PGM-1r* was significantly higher in males than in females for combined life-history types from Western Arm Brook. These results suggest that PGM-1r* is sex linked or under strong sex-specific selection in this population. Furthermore, populations with higher frequencies of PGM-1r*b tended to have higher frequencies of precocious maturation in males.

Induction and clearance of cytochrome P4501A mRNA in Atlantic tomcod caged in bleached kraft mill effluent in the Miramichi River

Levels of cytochrome P4501A mRNA were measured in Atlantic tomcod caged in the effluents of a bleached kraft pulp and paper mill on the Miramichi River, NB, Canada and two sites downstream, and compared to levels in fish caged upstream of the mill and in unexposed laboratory-maintained tomcod. Additionally, the rate of clearance of CYP1A mRNA in tomcod exposed at the mill and transferred to clean water was compared to that observed in tomcod treated in the laboratory with a single dose of 2,3,7,8-TCDD (0.5 μg/kg). Levels of CYP1A mRNA in tomcod caged upriver of the mill were low and comparable to those observed in untreated laboratory control fish. Levels of CYP1A mRNA were elevated up to 11-fold in tomcod caged at the mill site and a gradient in levels of gene expression was seen at the two downstream sites. Tomcod i.p. injected with a single dose of 2,3,7,8-TCDD exhibited a profile of prolonged CYP1A mRNA induction of at least 25 days. Levels of CYP1A mRNA in tomcod caged at the mill site and transferred to clean water remained significantly induced for at least 3 days post-transfer. In combination, these results suggest that CYP1A mRNA was induced in caged tomcod by constituents of the mill's effluents and that the rates of clearance of CYP1A mRNA may provide additional information concerning the identity of environmental inducers.

Mitochondrial DNA Variation in Striped Bass (Morone saxatilis) from Canadian Rivers

Mitochondrial DNA(mtDNA)was analysed to determine the genetic relatedness of striped bass (Morone saxatilis) populations in tributaries to the Gulf of St. Lawrence and the Bay of Funday. Mitochondrial DNA genotype frequencies were compared with those of striped bass from the Shubenacadie River (Bay of Fundy) and the Miramichi and Tabusintac rivers (Gulf of St. Lawrence). These mtDNA genotype frequencies were compared with those of striped bass representative of the Atlantic coastal migratory stock originating in the Hudson River and Chesapeake Bay. Differences in the frequencies of mtDNA length variants permitted discrimination of the Shubenacadie River from the Miramichi River and Tabusintac River populations and all three Canadian populations from the U S. spawned costal migratory stock. No difference in the frequency of mtDNA length variants was observed between Tabusintac River and Miramichi River striped bass. Heteroplasmy for mtDNA length variants was observed in 35% of Gulf of St. Lawrence fish, the highest frequency observed in any striped bass population. These results highlight the genetic heterogeneity of these Canadian striped bass populations and their distinctiveness from U S. stocks. Future efforts to restore these depleted Canadian striped bass populations should consider the impact of stock transfer on endemic striped bass gene pools.

Les parasites de l'alose d'été (Alosa aestivalis) et du gaspareau (Alosa pseudoharengus) de la rivière Miramichi, Nouveau-Brunswick

The parasite fauna of blueback herring (Alosa aestivalis) and alewife (Alosa pseudoharengus) were examined to determine their usefulness as biological indicators in the differentiation of these two sympatric species. Thirteen parasite species were identified from 100 specimens each of blueback herring and alewife from the main estuary of the Miramichi River, New Brunswick, of which 11 and 8, respectively, represent new host records. Significant differences (p < 0.05) in the counts of Mazocraeoides sp., Diplostomum spathaceum (metacercaria), Derogenes varicus, Anisakis simplex (larvae), and Echinorhynchus gadi between alewives and blueback herring reflect differences of physiological and ecological order between these two host species.

Effects of prior exposure history on cytochrome P4501A mRNA induction by PCB congener 77 in atlantic Tomcod

Levels of P450IA mRNA in tomcod collected from the Miramichi River, Canda and the Hudson River, New York were measured by slot blot analyses after the fish had been depurated and i.p. injected with Aroclor 1254, PCB congener 77, or PCB congener 105. Elevated expression of P450IA mRNA was observed in congener 77-treated Miramichi tomcod, whereas no induction was seen in the Hudson River fish. Tomcod from both rivers were induced by injection with beta-naphthoflavone. These results suggest that the prior exposure history of the Hudson River tomcod may have affected their non-inducibility by treatment with PCB congener 77.

Effect of Sea-Age on the Reproductive Potential of Atlantic Salmon (Salmo salar) in Eastern Canada

Reproductive potential of Atlantic salmon (Salmo salar), defined as average eggs per fish in the spawning run, varied three-fold both within stocks over time and among stocks from different geographic areas. Eggs per spawner is a function of fecundity, sea-age, proportion of females, and female size; the latter three traits varied significantly among years for salmon in both the Miramichi and Restigouche Rivers, New Brunswick. Because all of the above traits are related to sea-age at maturity, eggs per spawner was significantly correlated with mean sea-age in both rivers (R2 = 0.88 and 0.61, respectively). Among 10 different populations in eastern Canada, reproductive potential was also correlated with sea-age; for mean sea-ages (MSA) ranging from 1.0 to 1.8 yr, reproductive potential (RP) was defined by the power regression: RP = 1831.26 MSA1.30 (R2 = 0.64 P < 0.05). Thus reproductive potential can be estimated for any population for which the sea-age composition of spawners is known. Assuming a target egg deposition rate of 2.4 × 104 eggs per hectare, required spawners varied inversely with reproductive potential among the 10 populations, from five spawners (MSA = 1.75 yr) to 16 spawners (MSA = 1.15 yr) per hectare.

Coronary arteriosclerosis in Atlantic salmon. No regression of lesions after spawning.

The incidence and severity of coronary arteriosclerosis were studied in 209 wild and cultured Atlantic salmon (Salmo salar L.) during various stages of recovery of bodily condition after spawning. All recently spawned fish had lesions of moderate to extreme severity. The incidence of lesions for each fish was high (73% to 94% of all arterial cross-sections examined). The incidence and severity of lesions did not decrease during 5 months in a group of wild salmon reconditioned in the laboratory. Wild salmon that were examined in the spring angling fishery in the Miramichi River, New Brunswick, about 5 months after spawning had a high incidence (89%) of severe lesions, not significantly different from recently spawned salmon from the same and another river. A population of cultured salmon sampled at intervals from a sea cage during 9 months after spawning showed no evidence of lesion regression, but rather a continued increase in both incidence and severity during recovery of bodily condition and growth. Thus, in contrast with previous studies with steelhead trout and Atlantic salmon where the possibility of lesion regression has been suggested, our observations on a large number of Atlantic salmon from various sources gave no evidence of lesion regression. Coronary arteriosclerosis in Salmo salar appears to be a progressive condition, which continues during recovery of bodily condition and growth after spawning.

Influence of Seasonal River Discharge on Survival of Juvenile Atlantic Salmon Salmo Salar

The effects of winter and summer river discharge on the survival of eggs and underyearlings of Atlantic salmon (Salmo salar) were examined in six rivers of Newfoundland and New Burnswick where stock–recruitment relationships were available. There were positive relationships between either winter discharge or temperature and survival of underyearling salmon for five rivers. For all rivers combined, survival and winter discharge were related (P < 0.05). The hypothesis that summer discharge was unrelated to survival could not be rejected. However, there was evidence that summer discharge enhances survival in the Miramichi and Northwest Miramichi rivers of New Brunswick.

A Stock-Recruitment Relationship for Atlantic Salmon in the Miramichi River, New Brunswick

Abstract A stock-recruitment relationship for Atlantic salmon (Salmo salar in Miramichi River, New Brunswick, is described. Angling catches of kelts or black Atlantic salmon were used as an indication of spawning stock, and densities of small parr determined from electrofishing surveys were used as an index of recruitment. The linear correlation between the two variables indicated that the Miramichi River has received inadequate egg depositions in recent years (1969-1982).

Geochemkal Transport Through the Miramichi Estuary

A 2-yr seasonal study of the physical oceanography, geochemistry, and sedimentology of the Miramichi Estuary, New Brunswick, demonstrated that the overall system consists of two compartments: a drowned river, variable salt wedge estuary which is normally highly stratified, and the connected Inner Bay which is slightly stratified to well mixed. Freshwater inputs at the head of the estuary vary from 50 to 250 m3∙s−1 during summer and winter to high flows of 300 to 1700 m3∙s−1 during spring. Suspended particulate matter (SPM) and several labile trace metals including Fe, Mn, Zn, Cu, Pb, and Cd were analyzed to determine the total transport of potential contaminants within the system and into the Gulf of St. Lawrence. Wide variations in concentrations of SPM and labile metal by more than an order of magnitude are a function of freshwater input rates, tidal prism flushing characteristics, and geochemical interactions within the estuary. The transports for SPM, particulate metals, and labile metals were calculated using a tidal prism flushing model. Although 70% of the annual input of SPM (95 000 t) is exported from the estuarine system, about 60% of the total Fe (2000 t) is trapped in the estuarine bottom sediments. By contrast, 50% more Mn (200 t) is exported in combined particulate and labile forms than is brought into the estuary by the river. The source of this additional Mn is remobilization from fine-grained reduced bottom mud. The most important sink for Fe, Zn, Pb, and Cd appears to be the organic-rich bottom muds of the upper estuary. During spring flood periods, which last for an average of 39 d, about 85% of the annual supply of SPM enters the river estuary from the Miramichi River. Also during this time, 30–55% of the annual supply of labile metals Fe, Mn, Zn, and Cu enter the system. Much of this spring influx of SPM and metal is remobilized in the estuary over the rest of the year.

Modeling Suspended Sediment Dynamics of the Miramichi Estuary, New Brunswick, Canada

Polynomial models were used to estimate the annual transport of suspended sediment in an estuary with a variable salt-wedge. The models are empirical, based on water flux measurements and SPM concentration, and these are shown to be a function of the tidal oscillations and river discharge.The Miramichi River discharge varies from about 50 m3∙s−1 in January to 1700 m3∙s−1 in April. Diurnal inequality in the semidiurnal tides and variation in river discharge produces a continual inequality in the suspended sediment (SPM) transports for individual flood and ebb tides. Consequently, the models rely on integrating observations for each flood and ebb cycle. Empirical data indicate that semidiurnal tidal transport generally varies from 30 to 300 t in either ebb or flood direction. However, an order of magnitude increase can occur when the ebb tide couples with high runoff (i.e. 3300 t during a single ebb cycle in May 1976). A two-layer model gives a small (20%) increase in the residual sediment transport compared to a one-layer model. The 1976 net transport was calculated as −100 000 t (seaward). Sedimentation rates estimated from core samples agree with model estimates.Key words: Modeling, suspended sediment, SPM, transport, Miramichi, estuary

River discharge, sedimentation, and benthic environmental variations in Miramichi Inner Bay, New Brunswick

Sequential studies of benthonic foraminifera in the Miramichi estuary, New Brunswick over a 12 year period indicate that a "transitional" foraminiferal assemblage, which defines a zone of interaction of river and open bay environmental factors, has developed in Miramichi Inner Bay since 1964. Abundance variations of the transitional foraminiferal indicator species Ammotium cassis relative to Miliammina fusca (upper estuarine indicator) and Elphidium excavatum forma clavata (marginal marine indicator) in short cores suggest that the regional extent of this transitional thanatotope in the western part of Miramichi Inner Bay has varied considerably during the past 80–100 years. These changes appear to be related to total annual river discharge variations, competence of the Miramichi River system, and. possibly, changes in the tidal circulation pattern of bay water. Tidal circulation may have been altered by the location and cross-sectional area of several channels that occur between the barrier islands on the seaward side of the bay.

Emergence, population densities, and growth of salmon and trout fry in two New Brunswick streams

Postemergent downstream dispersal of Atlantic salmon fry (Salmo salar) was monitored using drift samplers during spring 1978 in two Miramichi River, N.B., tributaries. Catch rates of salmon fry peaked during the 2nd and 3rd weeks of June in both streams, coinciding with peak emergence of the salmon from the gravel. Very few trout fry (Salvelinus fontinalis) were captured in the drift nets, but electrofishing results indicated trout emergence preceded salmon by about 3 weeks.The earlier emergence of the trout gave them an early growth advantage over the salmon, so that trout fry were usually larger than salmon fry inhabiting the same stream areas. Early growth rates of both salmon and trout were quite varied among four stream sites during 2 years when growth was monitored; growth differences were discussed in relation to stream temperatures and density-dependent growth. Salmon fry were more abundant than trout fry at most sites in both years.

Growth, biomass, and production of juvenile Atlantic salmon (Salmo salar L.) in two Miramichi River, New Brunswick, tributary streams

The production rate of juvenile Atlantic salmon (Salmo salar) was estimated at four sites in two tributary streams of the Miramichi River, New Brunswick, during the period September 1976 to October 1978. Annual production ranged between 0.27 and 5.12 g∙m−2∙year−1. Growth was largely restricted to a 4-month period in early summer. Among the four sites, age 0+ salmon attained a mean weight of between 0.95 and 3.50 g by the end of their first growing season (September) and densities in July ranged between 0.3 and 3.1 fry∙m−2∙Age 1+ parr grew to mean weights between 4.95 and 12.45 g by September, and June–July densities ranged between 0.03 and 0.6 parr∙m−2. Marking information indicated that most parr remained in the study sites from July to September, but larger proportions of migrant parr were recorded in October. Production during summer was directly and positively related to initial population densities. Production rates at these sites were lower than most other recorded values for juvenile Atlantic salmon. Biomass of salmon may have been below the carrying capacity of the environment at all four sites.

Evidence of Adaptive Polygenic Variation Between Two Populations of Atlantic Salmon (Salmo salar) Native to Tributaries of the S. W. Miramichi River, N.B.

Breeding experiments were conducted to test the hypothesis that spatial homeostasis in growth and proximate composition and geographic variation in body morphology and timing of migration in juvenile Atlantic salmon (Salmo salar) have an adaptive basis. The populations studied were Rocky Brook and Sabbies River, tributaries of the Southwest Miramichi River, New Brunswick. Growth rates and proximate composition were very similar in the two populations under hatchery conditions. Genetic contributions to homeostasis in these traits were largely additive. The phenotypic expression of migratory behavior and the genetic control of timing were not quantifiable. A genetic basis to interpopulation variation in body morphology was demonstrated. Progeny from Rocky Brook which exhibits higher flows had more fusiform bodies and longer fins than progeny from Sabbies River when reared under identical conditions. Heritable variation in morphology and a demonstrated directional selection for greater fin size in high velocity environments support the hypothesis that these traits are adaptive. Adaptive polygenic variation between local populations stresses the need to delineate stocks on a functional basis so that species can be managed without significant loss of fitness and/or depletion of genetic variation in natural populations.Key words: quantitative genetics, heritability, adaptation, morphology, growth, proximate composition, migration, Atlantic salmon, interdemic variation, directional selection

Evidence of an Adaptive Basis for Geographic Variation in Body Morphology and Time of Downstream Migration of Juvenile Atlantic Salmon (Salmo salar)

Differences in growth rate, proximate composition, body morphology, and time of downstream migration between two populations inhabiting tributaries of the Miramichi River, New Brunswick, that differed in distance from the head of tide, temperature, and flow velocity were studied. Rocky Brook, located 132.6 km above the head of tide, had lower temperatures and higher average flow velocities than Sabbies River, located 42.5 km above tide. Growth rate and proximate composition were similar between populations, but body morphology and time of downstream migration differed significantly between populations. Individuals from Rocky Brook had more fusiform bodies and larger paired fins than their counterparts in Sabbies River. Rocky Brook fish also left the tributary in the fall rather than in the spring as was the case in Sabbies River. The generality of the flow regime–body morphology relationship observed was tested and confirmed by predicting differences in morphology of juvenile salmon in other rivers based on a knowledge of their flow regimes. It is suggested that early migration by the Rocky Brook fish is related to the higher energetic costs of overwintering in that stream. We hypothesize that the phenotypic similarity in growth rate and proximate composition and geographic variation in body morphology and timing of migration have an adaptive basis.Key words: geographic variation, polygenic traits, population biology, Atlantic salmon, morphology, migration, proximate composition, growth, adaptation

Aeromonas salmonicida in Atlantic salmon (Salmo salar): Occurrence of Specific Agglutinins to Three Bacterial Pathogens

In July 1975 the first confirmed isolation of Aeromonas salmonicida in the Canadian Atlantic region was made from victims of an epizootic among adult Atlantic salmon (Salmo salar) in the Restigouche River of northeastern New Brunswick. In studies on the sera from spawned Atlantic salmon broodstock from the Restigouche, Miramichi, and Margaree rivers, agglutinins to the ubiquitous A. hydrophila and the kidney disease (K.D.) corynebacterium were found in all three populations sampled; however, agglutinins to Aeromonas salmonicida were found only in salmon from the Restigouche River. When given an intraperitoneal injection of A. salmonicida cells alone or emulsified in Freund's complete adjuvant, a high percentage of Atlantic salmon parr produced antibodies against the immunogen, indicating that as yearlings the entire population was capable of an immune response to A. salmonicida. It is suggested that serological tests can provide a nondestructive means of obtaining presumptive evidence of contact between specific pathogens and individuals of a salmon population. Key words: Aeromonas salmonicida, A. hydrophila, K.D. bacterium, agglutinins, Atlantic salmon

Platyhelminth parasites of muskrats (Ondatra zibethica) in New Brunswick

During the summers of 1975 and 1976, 35 muskrats were examined for parasitic helminths. Twelve species of platyhelminths were recovered, including nine species of Digenea and three species of Cestoda. Muskrats collected from the streams and backwaters of the Miramichi River area harboured nine species of parasites compared with seven species recovered from both the Magaguadavic Lake area and the St. John River area, and five species recovered from muskrats on the Jolicure marshes. Quinqueserialis quinqueserialis showed the highest incidence of infection in all muskrats examined. Nudacotyle novicia and Echinoparyphium sp. showed the highest intensities of infection. Opisthorchis tonkae and Andrya macrocephala are recorded from muskrats in Canada for the first time. A possible explanation is given for the absence of Echinostoma revolutum in muskrats from marsh habitats.