bluuebunny/crossref_metadata_2025 huggingface dataset:
Ontogenetic Variation in the Multiple Hemoglobins of Arctic Charr, Salvelinus alpinus
Authors: Giles M. A. , Rystephanuk D. M.
Published: April 2011

Changes during development in the multiple hemoglobins of hatchery-reared Arctic charr, Salvelinus alpinus, that originated from an anadromous stock from Nauyuk Lake, Northwest Territories were examined by starch gel electrophoresis. A total of 10 anodic and 7 cathodic hemoglobins were expressed during the life cycle of the charr. Embryos and newly-hatched alevins exhibited 10 anodic and 3 cathodic components. Of these embryonic hemoglobins, 5 anodic components and possibly 1 cathodic component with similar electrophoretic mobility were observed in older fish. In free-swimming fry 3–4 new cathodic components were expressed. Two phenotypes (designated as 3-C or 5-C) were identified in postembryonic charr, distinguished by the presence of either 3 or 5 cathodic hemoglobins, respectively. In both phenotypes the proportion of cathodic hemoglobins increased progressively with age to a maximum of 22 and 18% of total hemoglobin in the 3-C and 5-C phenotypes, respectively.
Effect of Zooplankton Abundance and Body Size on Growth of Age-0 Yellow Perch (Perca flavescens) in Oneida Lake, New York, 1975–86
Authors: Mills Edward L. , Sherman Ruth , Robson Douglas S.
Published: April 2011

We examined an 11-yr (1975–86) field data set to determine whether annual differences in age-0 yellow perch (Perca flavescens) growth in weight were related to the abundance, size structure, and species composition of zooplankton in Oneida Lake, New York. A model for prediction of age-0 yellow perch weight was determined using a multiple regression technique; age-0 yellow perch wet weight (grams) was the dependent variable while age-0 yellow perch density, water temperature, calendar day, and cumulative biomass of both zooplankton taxonomic groups (daphnids, "other cladocerans," calanoids, cyclopoids, and nauplii) and zooplankton size classes (< 1.1 mm, 1.1–1.7 mm, and > 1.7 mm) were the independent variables. Analyses were based on an integrated approach where time was measured in cumulative temperature units and yellow perch weight was considered a function of the cumulative amount of food available. Below a cumulative temperature of 1350 °C∙d−1, none of the independent variables were related significantly (P < 0.05) to yellow perch weight. Beyond 1350 °C∙d−1 age-0 yellow perch weight was strongly correlated with the biomass of Daphnia and significant (P < 0.05) prey size variables shifted toward larger prey as fish grew. Our results indicate size- and species-based interactions between fish and zooplankton play an important role in regulating growth of age-0 fish.
Potential for Predicting Plankton Populations (and Fish Recruitment) from Environmental Data
Authors: Evans Geoffrey T. , Pepin Pierre
Published: April 2011

A model of annual plankton cycles, which responds to seasonal changes in light and mixed layer depth, was driven by a 26-yr series of observed mixed layer depths. Within the model, year-to-year changes in herbivore concentration are completely determined by year-to-year changes in mixed layer depth; but a correlational study of these two variables does not reveal the dependence, especially for spring herbivore concentrations. Fish recruitment, to the extent that it depends on the timely availability of planktonic food, may be difficult to relate to environmental observations. There are, however, some weak but long-lasting correlations which adult fish may be able to use as a cue for allocating reproductive effort.
Biennial Reproductive Cycle of Blue King Crab, Paralithodes platypus, at the Pribilof Island, Alaska and Comparison to a Congener, P. camtschatica
Authors: Jensen Gregory C. , Armstrong David A.
Published: April 2011

Pribilof Island blue king crab (BKC; Paralithodes platypus) were sampled by beam trawl in May and August of 1983 and April 1984 to determine timing of reproductive events. Biennial reproduction was found to be the result of slow ovarian growth in large, muciparous females, while smaller primiparous females are often able to spawn in two consecutive years. Mating and egg extrusion occur in late March to early May and eggs hatch in mid-April of the following year, consequently, the embryonic period and rate of development is approximately 12 mo, similar to that of its congener the red king crab (RKC; P. camtschatica). Comparison of the reproductive output of the two species revealed that despite the 2 yr ovarian cycle, BKC only produce 20–30% more dry egg mass at any carapace length than do RKC, a substantially smaller difference than previously calculated. One year after molt, females of both species are not significantly different in dry body weight over a size range of 100–140 mm carapace length, but RKC have produced about three times more dry ovarian weight than BKC of comparable size, suggesting that biennial reproduction in BKC may be the result of energetic limitations.
Effects of Temperature on the Oxidation of Fatty Acids, Acyl Carnitines, and Ketone Bodies by Mitochondria Isolated from the Liver of the Lake Charr,Salvelinus namaycush
Authors: Ballantyne J S. , Flannigan D. , White T. B.
Published: April 2011

Mitochondria isolated from the liver of the Lake Charr Salvelinus namaycush oxidize a wide range of acyl chain lengths of fatty acids and acyl carnitines at 1, 10, and 20 °C. For most carbon chain lengths the relative importance of carnitine-dependent fatty acid oxidation increases with increasing temperature due to greater thermal enhancement of carnitine-dependent oxidation. At low temperatures the rate of carnitine-independent fatty acid oxidation rivals that of carnitine-dependent oxidation. Therefore, acute temperature shifts during excursions above the thermocline would have important effects on the oxidation of dietary and depot lipids. Temperature does not substantially affect the chain length preference for fatty acid oxidation either in the presence or absence of carnitine, suggesting acclimation-induced changes in substrate specificity of fatty acid oxidation may not be necessary. The importance of β-hydroxybutyrate as an oxidative substrate increases at low temperatures relative to other substrates while acetoacetate oxidation is greater than that of β-hydroxybutyrate at 10 and 20 °C. Altered ketone body metabolism may play a role in regulating cholesterol levels to alter membrane fluidity.
Use of Lake Fossil Diatom Assemblages to Determine Historical Changes in Trophic Status
Authors: Agbeti M. , Dickman M.
Published: April 2011

Based on the composition of surface sediment diatom assemblages of 30 lakes a classification index for lake trophic status was developed. The lakes were selected to represent a continuum ranging from oligotrophic to eutrophic lake types. A trophic index quotient was derived. The log diatom inferred trophic index (D.I.T.I.) was regressed against the trophic status of the lakes as determined by the log total phosphorus (r = 0.84) and log chlorophyll-a (r = 0.91). Multiple regression analyses showed significant correlations between log D.I.T.I. and the log percentage abundances of oligotrophic, mesotrophic, and eutrophic species (r = 0.89). The abundance of the trophic indicator diatom species depends not only on total phosphorus and chlorophyll-a, but possibly on the interaction of these with other factors. Using this approach, past trophic changes were inferred for oligotrophic Barbara Lake and eutrophic Chemung Lake. The study suggested that Barbara Lake had retained its present day oligotrophic condition over the last 200 yr, whereas major trophic changes have occurred in Chemung Lake.
Impact of Methoxychlor on Selected Nontarget Organisms in a Riffle of the Souris River, Manitoba
Authors: Sebastien Robert J. , Brust Reinhart A. , Rosenberg David M.
Published: April 2011

The insecticide methoxychlor was applied at 300 μg∙L−1 for 15 min to a riffie on the Souris River, located about 18 km downstream from Souris, Manitoba. Physical, chemical, and biological variables were measured and aquatic insect community structure was monitored using drift, emergence trap, and artificial substrate samplers. All taxa monitored, irrespective of functional feeding group, drifted catastrophically for 4–24 h immediately following methoxychlor addition. Different species demonstrated varying abilities to recoionize artificial substrates following treatment. Species having a high propensity to drift naturally, recolonized most rapidly. Taxa that required the longest period to recoionize following methoxychlor treatment were generally univoltine, had a low propensity to drift, and a limited ability to disperse as adults. Impact of methoxychlor was influenced by the prevalent life-cycle stage of some species at the time of treatment. Catostomus commersoni fry and juvenile Orconectes virilis were more sensitive to methoxychlor than previous research on mature individuals has indicated. Invertebrate drift appeared to be more sensitive to pesticide treatment than benthic invertebrates on artificial substrates. Species richness and total numbers of drift were significantly reduced for at least 33 d following treatment, whereas richness and numbers on artificial substrates were significantly lower for only 4 and 8 d, respectively.
Controls on Dissolved Organic Carbon Concentrations in Streams, Southern Québec
Authors: Eckhardt B. W. , Moore T. R.
Published: April 2011

Dissolved organic carbon (DOC) concentrations were measured in streams draining 42 small (0.6–37.2 km2) catchments located in the Appalachian Uplands and St. Lawrence Lowlands. Weekly sampling from mid-April to late-November in four catchments containing < 1% wetland revealed DOC concentrations in streams averaging 3.5–7.2 mg∙L−1 with significant (r2 = 0.28–0.66, P < 0.01) positive relationships to discharge. In four catchments containing 15–69% wetland, average DOC concentrations in streams ranged from 14.5 to 40.0 mg∙L−1 and there was no significant relationship to discharge. Based on five sampling dates from May to November, DOC concentrations in streams draining the 42 catchments showed consistent relationships of varying strength (r2 = 0.26–0.67, P < 0.01) with the variable percent wetland in the catchment. Soil drainage rating, percent forest, mean catchment slope, and catchment area provided little improvement in the regression model. Separating the catchments into two regions (Uplands and Lowlands) improved the predictive power of the regression model for the upland catchments. The poor relationships between DOC and percent wetland in the lowland catchments are attributed to the dry summer during sampling and extensive modification of land use, such as the drainage of wetlands and agriculture. These results indicate that stream DOC concentrations may be predicted from easily-obtained catchment variables, such as percent wetland.
Whole Body Ions of Brook Trout (Salvelinus fontinalis) Alevins: Responses of Yolk-Sac and Swim-Up Stages to Water Acidity, Calcium, and Aluminum, and Recovery Effects
Authors: Wood C. M. , McDonald D. G. , Ingersoll C. G. , Mount D. R. , Johannsson O. E. , Landsberger S. , Bergman H. L.
Published: April 2011

Water pH, rather than Ca or Al, was the most important factor affecting whole body ions in yolk-sac or swim-up fry exposed to a matrix of pH (6.5–4.0), Ca (0.5–8 mg/L), and Al (0–1000 μg/L). Fry were raised from fertilization (day 0) in flowing soft water (pH = 6.5, Ca = 2 mg/L, Al = 0 μg/L), exposed to pH/Ca/Al on day 49 (yolk-sac, 2 d post-hatch) or day 70 (swim-up) for 21 d, and then allowed to recover a further 20 d. Yolk-sac fry were extremely resistant at [Formula: see text]; developmental effects, as indicated by body weight and Mg, were negligible. However whole body Na, Cl, K, and Ca were depressed by low pH, while water Ca was protective. Aluminum (37–111 μg/L) raised most ions above control values, while higher Al lowered them. Swim-up fry were more sensitive, showing pronounced developmental inhibition (lower weight, higher Mg) under adverse conditions; mortality continued during recovery. Low pH was again the dominant influence on body ions, water Ca was protective, while Al (12–111 μg/L) was only protective and not stimulatory. These effects persisted significantly; indeed responses in body Ca were larger after recovery than after the exposure itself, in the field, emergence from the redd into ambient acidic water is probably the critical stage. Water pH will be the principal determinant of whole body ions in alevins surviving this emergence, in contrast to fry exposed continuously from fertilization.
Epidermal Response to pH, Aluminum, and Calcium Exposure in Brook Trout (Salvelinus fontinalis) Fry
Authors: Ingersoll C. G. , Sanchez D. A. , Meyer J. S. , Gulley D. D. , Tietge J. E.
Published: April 2011

Eyed brook trout eggs were exposed to various combinations of pH (4.3–6.3), aluminum (0–1000 μg/L), and calcium (0.5 to 8.0 mg/L) for 40 d through hatching until the swim-up life stage. High resolution light microscopy, image analysis, and stereological techniques were used to quantitatively determine morphological changes in the epidermis of fry surviving this exposure. Exposure to increased acidity resulted in both mucous cell hypertrophy (increase in size) and hyperplasia (increase in number); exposure to low calcium resulted in mucous cell hyperplasia. Aluminum did not significantly affect mucous cell size or number. Epidermal thickness was not consistently affected by exposure to pH, aluminum, or calcium. The changes observed in epidermal mucous cells may be a compensatory mechanism used by brook trout fry to counter ionoregulatory stress resulting from extended exposure to acidic conditions.
Intra- and Interspecific Differences in the Response of Two Lentic Species of Leeches to Seasonal Hyperoxia
Authors: Davies Ronald W. , Gates T. E.
Published: April 2011

Intra- and interspecific differences in survivorship of Nephelopsis obscura and Erpobdella punctata exposed to hyperoxia (200 or 300%) at spring (5 °C) and summer (20 °C) water temperatures were examined in a flow-through system. In general, percent survival and time of 50% survival increased with leech size and decreased with higher temperature for both species. All size classes could survive the maximum recorded duration of hyperoxia in the spring, and we conclude that spring hyperoxia probably does not directly affect the ecological success or microhabitat distribution of either species. At 20 °C, medium and large E. punctata had much higher survivorship than N. obscura. As summer hyperoxia can last for 30 d, these differences could contribute to changes in numerical dominance. Intra- and interspecific differences in response to hyperoxia may also influence seasonal movements between different microhabitats of different size classes of N. obscura and E. punctata. We suggest that seasonal and annual variability in littoral hyperoxia regimes can differentially influence the survivorship, reproductive success, and microhabitat distribution of many macroinvertebrates.
Distribution and Phenotypic Correlates of Variation at Enzyme Coding Loci in Rainbow Trout (Oncorhynchus mykiss) from the Lower Laurentian Great Lakes
Authors: Ferguson Moira M. , Ihssen Peter E.
Published: April 2011

The distribution of variation at 37 enzyme coding loci was determined in six samples of rainbow trout (Oncorhynchus mykiss) from hatchery and natural sources. Significant heterogeneity in allele frequencies was detected among samples of Lower Laurentian Great Lakes rainbow trout. Geographical proximity was a poor predictor of genetic similarity among samples. The adaptive significance of two loci was examined in 16 experimental families. Rainbow trout homozygous for an allele at a phosphoglucomutase structural gene (Pgm1-s), which results in no detectable activity of phosphoglucomutase (PGM1) in all tissues where this locus is normally expressed (e.g. muscle), were larger than those heterozygous or homozygous for the active allele. However, no significant differences in asymmetry of four bilateral meristic traits were detected between fish with different PGM1 phenotypes. Rainbow trout with PGM1 in liver because of a regulatory gene, Pgm1-t(b), were marginally larger than those without the allele. These data suggest a correlation between biochemical genetic variation and phenotypic characteristics associated with fitness.
Are Cultured Stocks of Brown Trout (Salmo trutta) and Rainbow Trout (Oncorhynchus mykiss) Genetically Similar to Their Source Populations?
Authors: Ferguson Moira M. , Ihssen Peter E. , Hynes Julian D.
Published: April 2011

The Ontario Ministry of Natural Resources (OMNR) implemented a controlled breeding program in the early 1980's with the objective of culturing fish that are genetically representative of the source populations. We describe the OMNR brookstock management plan for brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss) and test its effectiveness by comparing the allozyme variation of the source fish collected from the Ganaraska River, Ontario to several descendant hatchery lines. Ancestral and descendant rainbow trout do not show significantly different allele frequencies. However, significant differences were detected in brown trout. The absence of several rare alleles in hatchery fish can be explained by sampling error rather than inappropriate propagation methods. Hatchery stocks of either species do not show reduced enzyme heterozygosity compared to wild fish suggesting that the OMNR hatchery system has been successful in retaining allelic variation during broodstock founding and propagation.
Fish Introductions in Canada: Provincial Views and Regulations
Authors: Leach J. H. , Lewis C. A.
Published: April 2011

The umbrella legislation governing introductions of fish and fish products to the provinces and territories of Canada is the Fisheries Act of Canada which provides for the making of regulations concerning coastal and inland fisheries. Specific jurisidiction over introductions for fish health reasons is included in the Fish Health Protection Regulations under the Fisheries Act. Most of the jurisdictions have enacted fishery regulations under the federal Fisheries Act which control movement of fish into their territories and between water bodies within their boundaries. Some jurisdictions have additional broad natural resources legislation which includes provision for regulating movement of introduced species. Specific policies concerning introduction issues have been developed in some jurisdictions and are being considered in others. Legislation and compliance efforts to prevent unwanted introductions have not been particularly effective. Recent attention, particularly in the Great Lakes basin, has focused on ballast water introductions with potential for considerable economic and ecologic damage (e.g. Gymnocephalus cernuus, Dreissena polymorpha). Neither federal nor provincial legislation appears to have sufficient scope to prevent or control this class of introductions.
Steringophorus Odhner, 1905 (Digenea: Fellodistomidae) in deep-sea fishes from the northeastern Atlantic, with the description of Steringophorus margolisi n.sp.
Authors: Bray Rodney A.
Published: April 2011

Steringophorus margolisi n.sp., described from the ophidiid Spectrunculus grandis, is distinguished by its elongate vitelline fields and long caeca. Steringophorus (=Occultacetabulum) dorsolineatum (Reimer, 1985) n.comb. is described from the chlorophthalmid Bathypterois dubius. It is suggested that the genus Occultacetabulum is synonymous with Steringophorus, and evidence is presented to show that the withdrawal of the ventral sucker into the body is a temporary condition. Steringophorus thulini Bray and Gibson, 1980 is partly redescribed from the macrourids Coryphaenoides (Chalinura) mediterraneus, C. (Chal.) brevibarbis, C. (Chal.) leptolepis, C. (Chal.) profundicolus, and Trachyrincus murrayi. Steringophorus blackeri Bray, 1973 is reported from the alepocephalid Xenodermichthys copei.
Experimental infection of fish with larval sealworm, Pseudotertanova decipiens (Nematoda, Anisakinae), transmitted by amphipods
Authors: McClelland G.
Published: April 2011

Larval sealworm (Pseudoterranova decipiens, (Krabbe 1878)) were transmitted sequentially through copepods and amphipods to 12 phylogenetically diverse fish species. Although P. decipiens in amphipods were 0.82–7.08 mm long, only those ≥1.41 mm were infective to fish. Sealworm transmitted at 15 °C migrated to the musculature within 6 h in mummichog (Fundulus heteroclitus) and 12 h in rainbow smelt (Osmerus mordax) but were confined to the bolus in an Atlantic cod (Gadus morhua) stomach at 24 h. All sealworm in smelt, but only 12% of those in cod, occupied the musculature after 7 days. Death of 15 mummichog and a grubby (Myoxocephalus aenaeus) 10–20 days after exposure apparently resulted from damage to the brain, heart, aorta, liver, or spleen by feeding and migrating nematodes. Whereas 100% of the sealworm in grubby and 86–88% of those in mummichog and winter flounder (Pleuronectes americanus) were dead and encapsulated in host connective tissue after 56 days, all P. decipiens in smelt were viable and unencapsulated. With length increasing linearly at 0.421 mm day−1, sealworm larvae reached 27.29 (23.60–30.70) mm after 56 days in smelt at 15 °C. However, P. decipiens, which escaped the host tissue response in mummichog and flounder, were only 10.14 (6.00–21.80) and 12.42 (9.53–14.40) mm in length, respectively.
Rediscovery in Japan and host association of Salmincola carpionis (Copepoda: Lernaeopodidae), a parasite of wild and reared freshwater salmonids
Authors: Nagasawa Kazuya , Yamamoto Masamichi , Sakurai Yasunori , Kumagai Akira
Published: April 2011

The parasitic copepod Salmincola carpionis (Krøyer, 1837) was rediscovered in Japan, where this parasite occurred on species of the genus Salvelinus (whitespotted char, S. leucomaenis; brook trout, S. fontinalis; their natural hybrid; Dolly Varden, S. malma; Miyabe char, S. malma miyabei) and rarely on rainbow trout (Oncorhynchus mykiss). The copepods were found on salmonids from a river in central Honshu and on those reared at an aquarium and a fisheries experimental station in northern Honshu. The preferred attachment site was the buccal cavity but at high intensities copepods were a little more frequently found on other parts. Prevalence and mean intensity of infection increased with increased size and age of the fish. At a constant water temperature, there were no seasonal changes in prevalence or mean intensity of infection, which may have resulted from continuous egg production by the copepods. The copepods that were previously described as Salmincola faleulata (Wilson, 1908) and later identified as S. californiensis (Dana, 1852) from kokanee (O. nerka) from Hokkaido, Japan, are assigned to S. carpionis.
Parasites of the hakesMerluccius australisandM.hubbsiin the waters around the Falkland Islands, southern Chile, and Argentina, with an assessment of their potential value as biological tags
Authors: MacKenzie K. , Longshaw M.
Published: April 2011

Samples of Merluccius australis (113 fish) and of M. hubbsi (195 fish) were collected from 16 positions on the Falklands and Argentine shelves and 1 off southern Chile. Twenty-eight fungal, protozoan, and metazoan parasite taxa, of which 19 were identified to the species level, and cysts of unknown etiology, were found. These included one new species of myxosporean protozoan found in both host species, three species that are new to both species of hake, three species not previously reported from M. australis, and one not previously reported from M. hubbsi. The most promising biological tags for stock identification, where long life spans are important, are an unidentified fungus; the protozoans Alatospora merluccii Kalavati, Longshaw and MacKenzie, 1995, Goussia sp., Kudoa rosenbuschi (Gelormini, 1944), Microsporidium ovoideum (Thélohan, 1895), Myxidium baueri Kovaleva and Gaevskaya, 1982, and Myxoproteus meridianalis Evdokimova, 1977; the metacestodes Grillotia sp. and Hepatoxylon trichiuri (Holten, 1802); and the parasitic copepod Trifur tortuosus Wilson, 1917. The adult digenean Elytrophalloides oatesi (Leiper and Atkinson, 1914) showed some potential as a tag for following seasonal migrations of hake.
Stock composition and movement of gemfish, Rexea solandri, as indicated by parasites
Authors: Sewell Kim B. , Lester Robert J.G.
Published: April 2011

The parasite fauna of gemfish, Rexea solandri, from seven areas off southern Australia, was examined for evidence of isolated gemfish populations. Canonical multivariate analyses of data on larval nematodes (Anisakis spp. and Terranova sp.), cestode plerocercoids (Hepatoxylon trichiuri and Nybelinia sp.), acanthocephalans (Rhadinorhynchus sp. and Corynosoma sp.), and a hemiuroid digenean from a total of 763 gemfish showed that the parasite faunas of fish from eastern Australia were similar except for a sample taken off New South Wales at the end of the spawning season whose affinities are unknown. Fish from South Australia had similar parasite faunas to those collected from eastern Australia, suggesting that fish from the eastern and western Bass Strait belong to the same stock. Fish collected from the Great Australian Bight were distinct from the southern and eastern fish. Differences in parasite fauna were detected between samples taken within the spawning season and those taken from the same locations outside the spawning season, presumably a result of the spawning migration.
Comparison of different models to predict the in situ embryonic developmental rate of fish, with special reference to white sucker (Catostomus commersoni)
Authors: Hamel P , Magnan P , East P , Lapointe M , Laurendeau P
Published: April 2011

We performed laboratory incubations of white sucker (Catostomus commersoni) eggs to determine (i) the incubation time to organogenesis, eyed egg, hatching, and swim-up phases at eight different temperatures (8.5-21.2°C), and (ii) the best model to describe the relationship between these incubation times and temperature. Seven models (degree-day, power-law, B e lehrádek's equation, quadratic equation, first- and second-order exponentials, and a thermodynamic model) all gave comparable and highly significant fits to our data (R2 > 0.90). We thus compared the in situ and predicted incubation times by (i) the degree-day model, because of its simplicity, and (ii) the thermodynamic model, because of its theoretical foundation. The degree-day model was at least as accurate as the thermodynamic model (overall mean difference between predicted and observed incubation times of 1.4 ± 1.0 and 1.2 ± 1.2 days for the thermodynamic and degree-day models, respectively). Given its high accuracy and simplicity of use, we conclude that the degree-day model should be used to predict the incubation times of white sucker. We also observed a synchronization of hatching in situ that suggested an influence of photoperiod in addition to that of water temperature.
Species and size differences in the digestion of otoliths and beaks: implications for estimates of pinniped diet composition
Authors: Tollit D J , Steward M J , Thompson P M , Pierce G J , Santos M B , Hughes S
Published: April 2011

We examined the digestion of hard remains of between one and four different size ranges of nine key North Sea prey taxa fed to seven captive harbour seals (Phoca vitulina). Percentage length reduction (mean 27.5%) and recovery rates (mean 42%) of experimental otoliths varied between species and were positively correlated to fish size and otolith robustness (mass/length). Mean length reduction of egested otoliths increased systematically with increasing size of ingested whiting and sandeel otoliths (p < 0.001), indicating that the size of larger fish may be underestimated. Intraspecific variation in otolith digestion was high (CV = 0.48-1.30), and to control for the artificial conditions of a captive study, external morphological features of otoliths were used to grade the degree of digestion and provide grade-specific correction factors. Bootstrap simulations were used to estimate 95% confidence intervals around correction factors and when partitioned indicated that calculation errors were in general less important than resampling errors. The application of species-, size-, and grade-specific correction factors progressively improved reconstructed estimates of prey biomass fed. As a consequence, estimates of prey size and diet composition require otoliths from faeces to be graded and more complex correction factors applied.
Influences of temperature upon the postexercise physiology of Atlantic salmon(Salmo salar)
Authors: Wilkie M P , Brobbel M A , Davidson K G , Forsyth L , Tufts B L
Published: April 2011

Atlantic salmon (Salmo salar) were acclimated and exhaustively exercised at 12, 18, or 23°C to determine how temperature influences the magnitude of postexercise physiological disturbances. At each temperature, exercise led to decreased white muscle ATP and phosphocreatine concentrations. Phosphocreatine was rapidly restored within 1 h at each temperature whereas ATP restoration took 1-4 h at 18 and 23°C, but considerably longer at 12°C. Exercise-induced depletions of white muscle glycogen were accompanied by elevations in muscle lactate, which contributed to 0.6 unit decreases in white muscle intracellular pH (pHi) at each temperature. Compared with rates of recovery in warmer water, glycogen resynthesis, lactate catabolism, and pHicorrection were slower at 12°C. White muscle REDOX state estimates suggested that slower postexercise recovery at 12°C was not due to oxygen delivery limitations. Marked postexercise elevations in plasma osmolality and lactate concentration were also observed and in each case correction of the disturbance took longer at 12°C. Paradoxically, significant mortality (30%) was observed only at 23°C. We conclude that while warmer water facilitates postexercise recovery of white muscle metabolic and acid-base status in Atlantic salmon, extremely high temperatures may make them more vulnerable to delayed postexercise mortality.
Seasonal changes in habitat use and preference by juvenile brown trout, Salmo trutta, in a northern boreal river
Authors: Maki-Petäys A , Muotka T , Huusko A , Tikkanen P , Kreivi P
Published: April 2011

By means of electrofishing, we examined seasonal and size-class variation in habitat preference by juvenile brown trout (Salmo trutta) in a third-order river in northern Finland. Larger trout preferred deeper stream areas than young-of-the-year fish. At the onset of winter, all trout size-classes moved into shallower water, but this mainly reflected seasonal variation in habitat availability. In winter, trout preferred slowly flowing stream areas, whereas in other seasons the mean water velocities used by trout parallelled habitat availability. In summer and autumn, age-0 fish favoured stream areas with large amounts of aquatic vegetation to provide cover. The largest trout (16-22 cm) occupied habitats with little cover throughout the year, and in winter, all trout avoided areas with high instream cover. In summer, all size-classes preferred small substrates, whereas in winter, areas with cobble-boulder substrates were preferred, especially by trout larger than 10 cm. Wintering trout often shelter among the interstitial spaces of coarse substrates, and to facilitate the survival of juvenile trout through winter, stream management programmes need to ensure that such particles are abundantly available in trout wintering areas.
The influence of temperature and food chain length on plankton predatorprey dynamics
Authors: Beisner B E , McCauley E , Wrona F J
Published: April 2011

With recent predictions for global climate warming, the question arises as to how changes in temperature influence the dynamics of populations in natural communities. We investigated the effect of temperature (18 and 25°C) on the stability of a common freshwater predator-prey system consisting ofDaphnia pulex and phytoplankton in different types of mesocosm communities. The plant-herbivore dynamics were examined in the presence and absence of the predator Mesostoma ehrenbergii to simulate food chains of two or three trophic levels, and in the presence or absence of competing zooplankton. The predator-prey system was destabilized at the higher temperature in all types of communities, and D. pulex extinction always occurred. This result was unaffected by simplification of the community but was enhanced by the addition of the carnivore. Mechanisms are proposed for the observed results including (i) the direct effect of temperature on vital rate parameters describing the D. pulex - algal interaction and (ii) a shift in algal community structure to less edible species following suppression by the herbivore at the higher temperature. Some implications of temperature increases expected under current global warming scenarios in pond systems are discussed.
Indirect effects of lake acidification on Chaoborus population dynamics: the role of food limitation and predation
Authors: Fischer J M , Frost T M
Published: April 2011

A twofold increase in Chaoborus punctipennis abundance following experimental acidification of one basin of Little Rock Lake, Wisconsin, provided an opportunity to examine the hypotheses that C. punctipennis dynamics were regulated by (i) food resources for instars I and II, (ii) fish predation on instars III and IV, and (iii) invertebrate predation on instars I and II. Neither food limitation nor fish predation appeared to be important constraints on C. punctipennis abundance. Although rotifer biomass increased significantly during the acidification, C. punctipennis did not respond in a consistent manner to variation in food availability. Bioenergetics estimates of C. punctipennis consumption by rock bass (Ambloplites rupestris), the most acid-sensitive fish species, were small compared with C. punctipennis production. In contrast, invertebrate predation appeared to be an important constraint on C. punctipennis abundance. Chaoborus punctipennis abundance increased dramatically when abundance of the predator Mesocyclops edax declined to near zero. Comparison of M. edax predation rates and first instar production suggested that M. edax could exert strong predation pressure on C. punctipennis Thus, invertebrate predation may create a juvenile bottleneck for populations of small-bodied Chaoborus species in moderately productive acidified lakes.
Mitochondrial DNA restriction site variation within and among five populations of Alaskan coho salmon (Oncorhynchus kisutch)
Authors: Carney B L , Gray A K , Gharrett A J
Published: April 2011

Mitochondrial DNA (mtDNA) from three Gulf of Alaska and two Bering Sea populations of coho salmon (Oncorhynchus kisutch) was assayed with 21 restriction endonucleases. A restriction site map was constructed for 15 enzymes that recognized hexanucleotide sequences and aligned to the rainbow trout (Oncorhynchus mykiss) gene map using the restriction map and known coho salmon sequences. The restriction site map and gene order of the coho salmon mtDNA genome are consistent with those of rainbow trout. Variation was observed for six enzymes at 10 sites that resulted in eight haplotypes. Variability and divergence observed exceeded those previously observed for allozyme loci in coho salmon. When variability that occurred only in single individuals was eliminated, two haplotypes that differed by four restriction sites remained. Variation at these sites was confirmed from polymerase chain reaction (PCR) amplified fragments. Bering Sea populations exhibited more variation than Gulf of Alaska populations. Explanations for the differences include more recent colonization by or smaller sizes of Gulf of Alaska populations.
Predator avoidance ability of juvenile chinook salmon (Oncorhynchus tshawytscha) subjected to sublethal exposures of gas-supersaturated water
Authors: Mesa M G , Warren J J
Published: April 2011

To assess the effects of gas bubble trauma (GBT) on the predator avoidance ability of juvenile chinook salmon (Oncorhynchus tshawytscha), we created groups of fish that differed in prevalence and severity of gas emboli in their lateral lines, fins, and gills by exposing them to 112% total dissolved gas (TDG) for 13 days, 120% TDG for 8 h, or 130% TDG for 3.5 h. We subjected exposed and unexposed control fish simultaneously to predation by northern squawfish (Ptychocheilus oregonensis) in water of normal gas saturation in 6, 18, and 10 tests using prey exposed to 112, 120, and 130% TDG, respectively. Only fish exposed to 130% TDG showed a significant increase in vulnerability to predation. The signs of GBT exhibited by fish sampled just prior to predator exposure were generally more severe in fish exposed to 130% TDG, which had the most extensive occlusion of the lateral line and gill filaments with gas emboli. Fish exposed to 112% TDG had the most severe signs of GBT in the fins. Our results suggest that fish showing GBT signs similar to those of our fish exposed to 130% TDG, regardless of their precise exposure history, may be more vulnerable to predation.
A reappraisal of the ocean migration patterns of Fraser River sockeye salmon (Oncorhynchus nerka) by individual-based modelling
Authors: Walter E E , Scandol J P , Healey M C
Published: April 2011

Although sockeye salmon (Oncorhynchus nerka) spend 1-4 years in the ocean and accumulate 99% of adult body weight during this period, their migratory patterns in the Northeast Pacific are not yet well understood. A model of ocean migration based on conjecture from limited catch and tagging data has influenced work in sockeye ecology for the past 20 years. To evaluate this model, we constructed a spatially explicit individual-based model that used ocean surface currents and simple behavioural rules to simulate migration patterns for sockeye from the Fraser River system. We explored several modelled behaviours, including random swimming and swimming with a directional bias during some months. The simulations begin at the time when juveniles leave inside coastal waters and end when return migration begins (a few months before river reentry). We determined that simple undirected swimming for most of the ocean phase (except the first 4 months when smolts are near the coast) provided results that challenged the prevailing model but did not require complex assumptions. The migration patterns generated by these rules compare well both qualitatively and quantitatively with the existing empirical data on British Columbia sockeye distribution and migrations in the ocean.
Bacterial productivity and protistan bacterivory in coastal and offshore communities of Lake Erie
Authors: Hwang S -J , Heath R T
Published: April 2011

The importance of protists as bacterivores in a coastal community and an offshore community of Lake Erie was compared during the summer of 1994. Bacterial density, cell size, and empirical conversion factors for bacterial productivity were highly variable at both sites and greater at the coastal site (P < 0.01). Bacterial productivity at the coastal site was 25-50 times higher than at the offshore site. Bacterivory was estimated in situ by fluorescently labeled native bacteria. Per-cell grazing rate and filtering rate for each taxon were routinely determined. Heterotrophic nanoflagellates (HNAN) were the most important protistan bacterivores at the offshore site, while HNAN and ciliates were similarly dominant bacterivores at the coastal site. Mixotrophic bacterivory was important only at the offshore site where Dinobryon was the dominant bacterivore. Bacterial carbon flux through protists was higher at the coastal site by an order of magnitude. Offshore protists grazed virtually the entire bacterial production, while coastal protists usually grazed less than half of the bacterial production. These results suggest that coastal and offshore sites differed fundamentally in the significance of protists to carbon flux through the microbial loop to higher trophic levels.
Scale-dependent variations in the precision of larval fish abundance estimates: a study of Sebastes sp. on Flemish Cap
Authors: Pepin P , Anderson J T
Published: April 2011

We test the assumptions of synopticity over a 6-d sampling period and homogeneity within a 40 times 40 km stratum by investigating the effect of sampling scale, or station spacing, on the precision (i.e., variance) of abundance estimates of larval redfish (Sebastes sp.). We contrast the results obtained for larval redfish with observations of scale-dependent variability in temperature, salinity, chlorophyll, and zooplankton, which have been shown to be interrelated in other systems. In contrast with previous studies, our results show that the patterns of variance in temperature, salinity, chlorophyll, and zooplankton are not scale dependent. Although the assumption of synopticity cannot be rejected, our results show that the variance in abundance of larval redfish is scale dependent and that it is much greater than the variances of the other variables considered. The contrasting pattern may be due to differences in the relative importance of physical and biological processes during the very early life history of marine fish. We suggest that sampling programs must be preceded by pilot studies designed to determine the effort required to obtain the most precise estimates of abundance given the limitations caused by the underlying sampling variability and the influence of physical processes.
Within-population variability in egg characteristics of walleye (Stizostedion vitreum) and white sucker (Catostomus commersoni)
Authors: Johnston T A
Published: April 2011

I examined variation in egg characteristics among individual females of sympatrically spawning walleye (Stizostedion vitreum) and white sucker (Catostomus commersoni) from Lake Manitoba. White sucker produced eggs of greater dry mass and energy content than walleye. Walleye egg dry mass varied between years and was positively related to both female length and age. The relationship between white sucker egg dry mass and female length varied between years. Egg energy density did not vary with respect to female length in either species. Egg energy density varied between years for walleye but not white sucker. Hatching success of walleye eggs was positively related to female age and negatively related to female length adjusted for age. Length and dry mass of walleye larvae at hatch increased with egg dry mass. Results suggest that the quality of eggs produced by walleye and white sucker populations may vary with the size and age structure of the populations and among spawning years.
Responses of skin mucous cells to aluminium exposure at low pH in Atlantic salmon (Salmo salar) smolts
Authors: Berntssen MHG , Kroglund F , Rosseland B O , Wendelaar Bonga S E
Published: April 2011

Atlantic salmon (Salmo salar) smolts were exposed for 80 h to seven water qualities: pH 5.6 with 31 and 46 µg labile Al · L-1, pH 6.0 with 18 and 24 µg labile Al · L-1, and pH 6.2 with 12 and 18 µg labile Al · L-1and control water at pH 6.8 and <10 µg labile Al · L-1. The three groups with the highest concentrations of labile Al (31 and 46 µg labile Al · L-1at pH 5.6 and 24 µg labile Al · L-1at pH 6.0) suffered high mortalities and showed a disturbance in osmoregulation and a massive secretion of mucus, as seen from a decrease in number of skin mucous cells. Furthermore, an increase in skin mucous cells containing acidic mucosubstances was observed. The loss of plasma chloride and skin mucous cells showed a significant linear correlation (R2= 0.68, p < 0.001). The increased secretion of mucus on skin and gills and the increase in acidity of mucosubstances are consistent with their prior presumed defensive role in binding of Al.
Identification of the toxic agent in metal-contaminated sediments from Manitouwadge Lake, Ontario, using toxicityaccumulation relationships in Hyalella azteca
Authors: Borgmann U , Norwood W P
Published: April 2011

Toxicity of sediments from Manitouwadge Lake, Ontario, to Hyalella correlated closely with bioaccumulation of zinc but not copper. Bioaccumulation in 1-week exposures was sufficient to infer chronic zinc toxicity. Close similarity between toxicity-accumulation relationships from Manitouwadge Lake and those obtained from zinc-spiked Hamilton Harbour sediments indicate that toxicity is due to zinc itself and not some other chemical that correlates with zinc in sediments. Sediment concentrations of zinc, on the other hand, are unreliable indicators of effects; toxicity was not highest in sediments from the most contaminated site. Copper accumulation was insufficient to cause short-term (1-week) toxicity. Chronic copper toxicity cannot be predicted from bioaccumulation, but the absence of a significant growth reduction, which is specific to copper, strongly suggests that the contribution of copper to chronic toxicity was minimal. Body concentrations of zinc and copper in wild animals from contaminated lakes (in contrast to laboratory animals exposed to sediments from those lakes) are not reliable indicators of metal toxicity, either because these amphipods have adapted to contaminated conditions or because they survive in selected microhabitats with reduced metal availability.
Relating swimming performance of lake sturgeon, Acipenser fulvescens, to fishway design
Authors: Peake S , Beamish F WH , McKinley R S , Scruton D A , Katopodis C
Published: April 2011

Fishways have traditionally been designed to provide safe passage for jumping fish and only recently have nonjumping species been considered. Concern over dwindling populations of lake sturgeon, Acipenser fulvescens, has focused attention on fishway designs that accommodate its swimming abilities. The objective of this study was to derive a model that relates swimming endurance of lake sturgeon to length and flow characteristics of fishways. Endurance at sustained and prolonged swimming speeds (those maintainable for more than 20 s) increased with water temperature but was independent of temperature at higher burst speeds. Endurance increased with total length at all swimming velocities. Swimming performance of lake sturgeon, relative to body length, is inferior to that of most salmonids, particularly at burst speeds. Fishway designers need to consider swimming ability, space requirements, and behavior of lake sturgeon to ensure that they can ascend potential migratory obstacles safely.
Is scientific inquiry incompatible with government information control?
Authors: Hutchings J A , Walters C , Haedrich R L
Published: April 2011

Government-administered science in Canada, and its potential for bureaucratic and political interference, merits examination in the wake of the biological and socioeconomic catastrophes associated with recent fishery collapses. We cite specific research on Atlantic cod (Gadus morhua) and Pacific salmon (Oncorhynchus spp.) habitat to illustrate how nonscience influences can interfere with the dissemination of scientific information and the conduct of science in the Canadian Department of Fisheries and Oceans. The present framework for linking fisheries science with fisheries management has permitted, intentionally or unintentionally, a suppression of scientific uncertainty and a failure to document comprehensively legitimate differences in scientific opinion. We suggest that the conservation of natural resources is not facilitated by science integrated within a political body. The formation of a politically independent organization of fisheries scientists, or some such reorganization of the link between scientific research and the management of natural resources, merits serious and open debate.