bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamics of the Recovery of the Western Lake Erie Walleye (Stizostedion vitreum vitreum) Stock
Authors: Hatch Richard W. , Nepszy Stephen J. , Muth Kenneth M. , Baker Carl T.
Published: June 2008

After its 1957 collapse under intensive fishing and environmental stresses, the walleye (Stizostedion vitreum vitreum) stock of western Lake Erie remained low throughout the 1960s. A moratorium on both sport and commercial fishing, resulting from the 1970 discovery of mercury concentrations in walleye flesh, provided an opportunity for the development of an international interagency management plan. The quota management plan developed depended on sequential projection of the fishable stock on the basis of estimated annual recruitment and reports of total withdrawals from the stock. The fishery reopened gradually and quota management (including allocation among jurisdictions) was implemented in 1976. The stock, which had been gradually increasing as a result of relatively strong year-classes produced in 1970, 1972, and 1974, responded well to limited exploitation and produced a record year-class in 1977. Quotas were exceeded in 1978–80, but the stock continued to improve to the extent that the recommended rate of exploitation was increased in 1980 and again in 1981. As the population expanded, growth began to decline; the decline became apparent in young-of-the-year in the early 1970s and in older walleyes in the late 1970s. This trend toward progressively slower growth, which continued in the 1977 and subsequent year-classes, was accompanied by an increase in length at sexual maturity and a decrease in the percentage of female walleyes reaching sexual maturity at age III. As a net result of these changes, the proportion of mature females in the stock (an index of stock fecundity) decreased slightly during the interval 1975–84, while the estimated biomass of the standing stock rose from 9 000 to nearly 26 000 t. Both sport and commercial catches increased markedly after 1980 in Lake Erie's central basin.
Recent Changes in Lake Michigan's Fish Community and Their Probable Causes, With Emphasis on the Role of the Alewife (Alosa pseudoharengus)
Authors: Eck Gary W. , Wells Larue
Published: June 2008

Major changes in fish populations occurred in Lake Michigan between the early 1970s and 1984. The abundance of lake trout (Salvelinus namaycush) and several nonnative species of salmonines increased greatly as a result of intensive stocking. The exotic alewife (Alosa pseudoharengus), which had proliferated to extremely high levels of abundance in the mid-1960s, declined, particularly in the early 1980s. We believe that the sharp decline in alewives in the 1980s was caused primarily by poor recruitment during the colder than normal years of 1976–82. Several of Lake Michigan's endemic species of fish appeared to be adversely affected by alewives: bloater (Coregonus hoyi), lake herring (C. artedii), emerald shiner (Notropis atherinoides), yellow perch (Perca flavescens), and deepwater sculpin (Myoxocephalus thompsoni), and possibly spoonhead sculpin (Cottus ricei). All declined when alewives were abundant, and those that did not become rare, i.e. the bloater, perch, and deepwater sculpin recovered when alewives declined. We present evidence suggesting that the mechanism by which alewives affect native species is not by competition for food, as has often been hypothesized, and discuss the possibility that it is predation on early life stages. Despite the decreased availability of alewives in the early 1980s, salmonines continued to eat mainly alewives. The highly abundant alternate prey species were eaten only sparingly, but alewives still may have been abundant enough to meet the forage requirements of salmonines. Two new exotics, the pink salmon (Oncorhynchus gorbuscha) and threespine stickleback (Gasterosteus aculeatus), increased in abundance in the 1980s, and could become detrimental (particularly the salmon) to other species.
Ecosystem Science for the Great Lakes: Perspectives on Degradaiive and Rehabilitative Transformations
Authors: Steedman R. J. , Regier H. A.
Published: June 2008

Conventional approaches to ecological management presuppose the preeminence of normal natural processes in quasi-equilibrium state, in the presence of one or a few cultural stresses of light to moderate intensities. They also presuppose that the abiotic and biotic structural form of the ecosystem is relatively unaffected. In some parts of the Great Lakes, normal natural ecosystem processes have been overwhelmed by numerous intense cultural factors. Rehabilitation of such areas requires information and understanding of a type that is not central to conventional fisheries biology. We review and extend existing scientific approaches that contribute to an effective and relevant "ecosystem science," according to the criteria that they (1) incorporate spatial and structural models appropriate to an ecosystem perspective of the Great lakes basin, (2) incorporate functional attributes actually observed in stressed and culturally degraded aquatic ecosystems, and (3) provide information directly relevant to effective, informal, broadly based mechanisms of ecosystem rehabilitation and husbandry.
Evaluation of the Effects of Fish Community Structure on Observed Yields of Lake Trout (Salvelinus namaycush)
Authors: Goddard C. I. , Loftus D. H. , MacLean J. A. , Olver C. H. , Shuter B. J.
Published: June 2008

Creel and lake survey data from 87 Ontario lakes with self-sustaining lake trout (Salvelinus namaycush) populations were analysed to determine the effect of intrinsic factors, such as fish community structure, and extrinsic factors, such as angling-effort, on the observed yields of lake trout. Multiple regression analyses showed that angling-effort and lake area, in order of importance, explained almost 82% of the variation in annual catches. Analyses of covariance were used to test a variety of hypotheses about how community structure — the presence of forage, competitors, or alternate sports species — affected the catch of lake trout. No significant differences among groups were detected, which suggests that fish community structure has little or no effect on actual yield of lake trout. The difficulties inherent in using catch and effort data alone to evaluate the importance of factors affecting productivity (or potential yield) are discussed.
Economie Analysis of Fishery Rehabilitation Under Biological Uncertainty: A Conceptual Framework and Application
Authors: Milliman Scott R. , Bishop Richard C. , Johnson Barry L.
Published: June 2008

Using the commercial yellow perch (Perca flavescens) fishery of Green Bay, Lake Michigan, as an example, we outline a conceptual framework for estimating economic gains from fishery rehabilitation in the presence of biological uncertainty. Three steps underlie the framework: (a) identifying the key biological uncertainties which hamper forecasts of stock changes induced by rehabilitation efforts; (b) developing plausible "future biotic states" that encompass these uncertainties and their probabilities of occurrence; and (c) estimating the "expected value" of economic gains for commercial fishers from an ongoing rehabilitation plan across these future biotic states. Using this approach, the expected economic gains for commercial fishers from rehabilitation are found to be roughly zero for most plausible scenarios. Since sport gains under this rehabilitation plan are probably substantial, and other economic impacts (regulatory costs and final consumer effects) appear to be small, the analysis suggests that the overall economic gains from the plan are positive.
Use of a Mixed-Species Yield-per-Recruit Model to Explore the Consequences of Various Management Policies for the Oregon Flatfish Fishery
Authors: Pikitch Ellen K.
Published: June 2008

A mixed-species yield-per-recruit model is developed for a portion of the Oregon flatfish fishery. The model is applied to examine the effects of implementing various management policies on fishery yield in weight and revenues for Pacific Marine Fisheries Commission Area 2B. Three types of management policies are considered: maximization of output, efficiency-oriented, and a minimum trawl cod-end mesh size regulation with no restriction of effort. If an efficiency-oriented policy were adopted, the current minimum mesh size regulation of 114 mm would be optimal. However, if effort is left unrestricted, or if a maximization strategy were adopted, a larger mesh size would result in greater volume yields. Optimal mesh size is more sensitive to the management policy selected than it is to either variations in recruitment or to costs associated with fishing. If economic considerations become more important in formulating management policy, greater gains could be achieved by limiting effort than by altering mesh size regulations. However, as the management policy becomes less restrictive of effort, the influence of mesh size on fishery output increases.
Forecasting Forage Demand and Yield of Sterile Chinook Salmon (Oncorhynchus tshawytscha) in Lake Michigan
Authors: Kitchell James F. , Hewett Steven W.
Published: June 2008

We assessed the potential role of sterile chinook salmon (Oncorhynchus tshawytscha) as piscivores and as the focus of a new trophy fishery in Lake Michigan. An energetics model for standard (not sterilized) chinook salmon was modified to extend the life history for up to 10 yr of life in Lake Michigan. A stocking of sterile fish consumes about one and a half times as much forage as would an equivalent stocking of standard chinook salmon over their life span, yet actually contributes less to the fishery because it lacks components that would mature precociously. At current growth rates, fish of trophy size (22.7 kg) would begin to appear in the fishery about 5 yr after stocking. Approximately 0.3% of sterile chinook would appear in the trophy fishery. These unique fish offer important opportunities for socioeconomic and ecological research.
Prey Fish Dynamics and Salmonine Predator Growth in Lake Ontario, 1978–84
Authors: O'Gorman Robert , Bergstedt Roger A. , Eckert Thomas H.
Published: June 2008

The size of hatchery-reared brown trout (Salmo trutta) and coho salmon (Oncorhynchus kisutch), 1 yr after release in Lake Ontario, declined when the stocking of salmonines was increased between 1978 and 1984. The principal prey species, alewife (Alosa pseudoharengus) and rainbow smelt (Osmerus mordax), failed to show the expected, predator-induced downturn in abundance. Instead, rainbow smelt remained moderately abundant and alewives very abundant. During this period, alewife year-classes were small, survival of yearling alewives was poor, growth of young-of-the-year of both alewives and rainbow smelt was slow (growth of most older alewives ceased), and rainbow smelt numbers gradually increased (the much larger alewife population presumably buffered older rainbow smelt from predation by large piscivores). When adult alewife numbers were halved by a winter die-off, the subsequent year-class of alewives was large and growth of brown trout during their first year in the lake increased. This suggested a causal relation between abundance of young alewives and brown trout growth. In the first year coho salmon were at liberty, their growth was related to abundance of young-of-the-year alewives; in their second year it was related to the abundance of yearling alewives and the condition of adult alewives. We hypothesize that abundant adult alewives suppressed production of young-of-the-year fish (necessary prey for salmonines during their first year in the lake) through competition for limited zooplankton production, and thus impeded the transfer of energy from the lowest trophic level to young salmonine predators.
Predicting Great Lakes Fish Yields: Tools and Constraints
Authors: Lewis C. A. , Schupp D. H. , Taylor W. W. , Collins J. J. , Hatch R. W.
Published: June 2008

Prediction of yield is a critical component of fisheries management. The development of sound yield prediction methodology and the application of the results of yield prediction are central to the evolution of strategies to achieve stated goals for Great Lakes fisheries and to the measurement of progress toward those goals. Despite general availability of species yield models, yield prediction for many Great Lakes fisheries has been poor due to the instability of the fish communities and the inadequacy of available data. A host of biological, institutional, and societal factors constrain both the development of sound predictions and their application to management. Improved predictive capability requires increased stability of Great Lakes fisheries through rehabilitation of well-integrated communities, improvement of data collection, data standardization and information-sharing mechanisms, and further development of the methodology for yield prediction. Most important is the creation of a better-informed public that will in turn establish the political will to do what is required.
A Review of Methods for Prediction of Potential Fish Production with Application to the Great Lakes and Lake Winnipeg
Authors: Leach J. H. , Dickie L. M. , Shuter B. J. , Borgmann U. , Hyman J. , Lysack W.
Published: June 2008

Methods for estimating fish production in aquatic ecosystems range from simple empirically derived estimators, such as morphoedaphic indices, to complex ecosystem simulation models. As first-order estimators, the former are attractive to managers because they are simple and relatively inexpensive to apply and interpret. Application of the latter group has been limited because many of the data inputs are difficult and expensive to obtain. Between these extremes are several models, such as the biomass–size spectrum model, that provide useful information for moderate expenditures of time and effort. Existing and new methods are reviewed in the light of production theory and several are applied to Great Lakes and Lake Winnipeg data. Eight empirical models derived from limnological variables were selected from the literature and used to estimate potential fish yield for the Great Lakes and Lake Winnipeg. The models predicted a fairly narrow range of potential yields, but when compared with historic yields, none was consistent for all lakes. The best overall empirically derived estimator of potential yield in the Great Lakes was the morphoedaphic index. Potential fish production estimated from invertebrate production with Borgmann's biomass – size spectrum model was considerably greater than historic yields or the yield estimates from the empirical models. In a third approach, we calculated life history parameters for "small" and "large" fish in the Great Lakes and combined these with Borgmann's production model, empirical information on population production/biomass ratios from the literature, and classical population dynamics theory to estimate potential production and optimum sustained yield for each group. Historic sustained yield, as a percentage of optimum sustained yield, varied from a low of 6 for "small" Lake Ontario fish to 100 for "large" Lake Erie fish.
Soft-Bodied Zooplankton Predators and Competitors of Larval Herring (Clupea harengus pallasi) at Herring Spawning Grounds in British Columbia
Authors: Purcell Jennifer E.
Published: June 2008

The soft-bodied zooplankton predators and the microzooplankton foods of herring larvae were collected at 28 herring spawning grounds in British Columbia in April 1984, when herring larvae (Clupea harengus pallasi) hatched. The same predator species were found throughout coastal B.C., but total densities varied over three orders of magnitude. Barkley Sound had the highest densities, and bays in northern B.C. and the Strait of Georgia had higher densities than open shorelines in both regions. Eight of 18 species of soft-bodied predators contained herring larvae. The hydromedusan Aequorea victoria was the most important predator, and consumed 0.4% of the herring larvae∙d−1 in Fanny Bay, and 12.5, 3.9, and 0%∙d−1 over three consecutive days in Kulleet Bay as larval densities decreased. Herring larvae ate copepod nauplii (84.4%) and other microzooplankton. Densities of these prey varied between 0.8 and 37∙L−1 among 21 locations sampled. Only three species of hydromedusae showed extensive dietary overlap (90–100%) with larval herring. Soft-bodied predators consumed < 1%∙d−1 of the microzooplankton in 17 locations, and could have affected densities in only one of the 21 locations. The ratios of microzooplankton to predator densities varied over 1000-fold, suggesting great differences in the chances for herring larval survival among various locations.
Conversion and Partitioning of Radio-Labelled Mercury Chloride in Aquatic Model Systems
Authors: Regnell Olof
Published: June 2008

Conversion and partitioning of radio-labelled inorganic mercury (203HgCl2) was studied in freshwater model systems composed of sediment and water, or water alone, incubated for up to 10 d. The mercury fractions studied were total 203Hg and methyl 203Hg in water and sediment, respectively, and volatilized 203Hg in the gas phase. Water samples were filtered to obtain values for dissolved total 203Hg and methyl 203Hg, respectively. Methylated 203Hg was detected in all systems. Most of the methyl-203Hg was bound to the sediments. Net methyl 203Hg production in a system with reduced sediment was an order of magnitude greater than in the other systems. Volatilization of 203Hg was most rapid in the systems without sediment, while no volatilization took place in sterilized systems.
Variation in Agonistic Behavior between Newly Emerged Juveniles from Hatchery and Wild Populations of Coho Salmon, Oncorhynchus kisutch
Authors: Swain D. P. , Riddell B. E.
Published: June 2008

We compared agonistic behavior of newly emerged coho salmon (Oncorhynchus kisutch) between hatchery and wild populations using mirror image stimulation tests. We used hatchery populations from two different regions of Vancouver Island B.C., each matched with a wild population from its region. In both comparisons, hatchery juveniles were more aggressive than wild juveniles. Rates of aggressive display increased with time since emergence for both hatchery and wild fish, as did the differences in behavior between the two types. By the sixth day of observation (13 d postemergence), the overall effect of fish type was highly significant for all aggressive behaviours. Since the individuals compared were reared from eggs under identical conditions, these differences are presumably genetic. Comparisons involved relatively few families from each population. However, because heritability was moderate to low within populations, and variance between population types exceeded variance among families within populations, these results indicate real differences at the population level. These results may have important implications for programs to rebuild wild populations using hatchery transplants and for selective breeding programs to develop domestic stocks of coho.
Experimental Harvesting of Cyclic Stocks in the Face of Alternative Recruitment Hypotheses
Authors: Parma Ana M. , Deriso Richard B.
Published: June 2008

Cyclic fluctuations in year-class abundance have been recorded for several fish populations. Historical patterns are generally consistent with several hypotheses about underlying mechanisms, which involve (a) strong density dependence or (b) environmental forcing. Optimal harvesting policies differ depending on which hypothesis is deemed true. Not only does the harvesting policy affect the amount of catch taken, but it can strongly affect our ability to discriminate between alternative hypotheses. Fully-adaptive feedback policies, which explicitly account for the information content of harvest controls, were computed with dynamic progamming for some model prototypes of the problem. Results indicate that deliberate experimentation with escapement levels, oriented to reduce the uncertainty, may be worthwhile under some conditions. In most cases, however, optimal passive policies (in which learning occurs passively) were a good approximation to actively adaptive policies. The optimal passive controls for maximizing a risk-neutral objective, such as total catch, were generally very informative. Although passive and active controls markedly differed in some cases, expected discounted yields under the two types of policies were very similar (differences less than 2%). The extreme risk-averse presciption of managing a stock according to the more pessimistic recruitment model may lead to considerable yield losses.
A Critical Review of Recent Freshwater Periphyton Field Methods
Authors: Aloi Jane E.
Published: June 2008

I review recently published research (1970–89) on freshwater periphyton, with emphasis on epilithon and epiphyton. Brushing syringe-samplers are recommended for sampling epilithon, due to their Sow cost, ease of use, and effective removal of periphyton from firm substrates. Methods for removing epiphyton include scraping, agitation, and chemical methods, and the choice of methods is influenced by morphology of the macrophyte. Artificial substrates for periphyton colonization (glass slides, styrofoam, clay tiles, and nutrient diffusing substrates) are also evaluated. Although the use of artificial substrates may decrease substrate heterogeneity and allow more complex experimental designs in studies of benthic herbivory, differences between the natural and artificial substrates may affect population size or behavior of herbivores. Methods for measuring primary productivity of periphyton (O2and14C methods) and recent advances in microelectrode technology that allow microscale measurements of productivity and several other parameters are discussed including key references for novice users. General recommendations include: (1) sampling periphyton on naturally occurring substrates rather than artificial substrates when measuring biomass, primary productivity or species composition; (2) using artificial substrates when experimental design dictates, but not ignoring their limitations; and (3) including accurate descriptions of methods to allow future comparisons between studies in different systems.
Aspects of the Energy Metabolism of Lake Sturgeon,Acipenser fulvescens, with Special Emphasis on Lipid and Ketone Body Metabolism
Authors: Singer Thomas D. , Mahadevappa Vhundi G. , Ballantyne James S.
Published: June 2008

Key enzymes in several metabolic pathways in five tissues were measured in a primitive osteichthyan, the lake sturgeon (Acipenser fulvescens). Levels of nonesterified fatty acids (NEFAs) were measured in the plasma as an indicator of fatty acid mobilization and differential utilization of individual NEFAs as substrates for lipid oxidation. The metabolism of lake sturgeon differs from that of most teleosts studied; it has detectable levels of beta-hydroxy-butyrate dehydrogenase in all tissues, possibly a primitive metabolic feature of vertebrates, subsequently lost in the teleosts. Based on HOAD and CPT activities lipid oxidation in extrahepatic tissues of sturgeon is intermediate between elasmobranch and teleost models. Sturgeon plasma NEFA concentrations are clearly higher than those detected in any elasmobranch, indicating that the acipenserid chondrosteans may be among the first jawed fish to mobilize and transport NEFAs. Oleic acid (18:1,n9) which amounts to 45% of total NEFA content of the plasma may be a preferred substrate of carnitine dependent oxidation. High levels of long chain fatty acid in the plasma may represent a high turnover of eicosanoid precursors. The low levels of LDH in the anoxia tolerant sturgeon may indicate that alternative anaerobic end products, perhaps ethanol, are used to survive under anoxic conditions.
A Multivariate Maturity Model with a Comparative Analysis of Three Lingcod (Ophiodon elongatus) Stocks
Authors: Richards Laura J. , Schnute Jon T. , Hand Claudia M.
Published: June 2008

In this paper we develop a multivariate analysis of length and age at maturity that includes the univariate maturity model of Schnute and Richards (1990, Can. J. Fish. Aquat. Sci. 47: 24–40) as a special case. In addition, we address the problem of drawing meaningful conclusions from large data sets oriented to fish maturity, and we present statistical tests of such conclusions. We illustrate our approach with comparisons among male and female lingcod (Ophiodon elongatus) from three stocks along the coast of British Columbia, Canada. From the univariate analysis, we demonstrate that male lingcod mature at a smaller size than female lingcod, and that for each sex, size at maturity increases with latitude. From the multivariate analysis, we determine that length and age together provide a better prediction of lingcod maturation than either variate considered alone. The multivariate model is applicable to any situation for which one or more positive variates is asymptotically related to a probability measure in the range (0, 1).
Effects of Discharge and Substrate Stability on Density and Species Composition of Stream Insects
Authors: Cobb D. G. , Galloway T. D. , Flannagan J. F.
Published: June 2008

Effects of discharge/substrate stability relationships on the abundance, diversity, and distribution of aquatic insects were studied from 1986 to 1988 in three reaches of a small stream in the Manitoba escarpment. Substrate stability (percentage of streambed paving material at incipient motion) ranged from 80 to 20% at bankfull discharge. Eleven taxa of mayflies, 15 taxa of caddisflies, and 10 taxa of stoneflies were collected. All but a few taxa were present at all stations. Benthic insect densities were negatively correlated with increasing discharge and substrate particle movement at all stations. Regression models describing insect density in terms of substrate stability usually accounted for more variation than models describing density in terms of discharge. Insect density decreased up to 94% at the most unstable stream reach following summer and autumn spates when 8 and 12%, respectively, of the streambed paving material was at incipient motion wheres no reduction occurred in a stable riffle constructed nearby. Most insect species were highly resilient; densities and diversities returned to prespate levels during periods of low flow. Temporal and spatial aspects of substrate stability should be considered in stream insect studies, particularly in relation to disturbance.
Optimal Harvesting Policy for Chub Mackerel (Scomber japonicus) in Japan under a Fluctuating Environment
Authors: Matsuda Hiroyuki , Kishida Tatsu , Kidachi Takashi
Published: June 2008

Temporal fluctuation in the reproduction rates of chub mackerel (Scomber japonicus) was estimated for the period 1971–86, when stock abundance of chub mackerel varied from a high to low level. To estimate the effect of various harvesting policies on stock conservation and the long-term catch, six harvesting policies were considered: (1) actual catch data during 1975–88, (2) 1/3 constant rate of exploitation, (3) low maximal catch amount, (4) 1/5 constant rate of exploitation, (5) prohibition of fishing when the stock is rare, and (6) constant-escapement policy. Using the data of reproduction rates during 1975–85, the final stock abundance at 1988 and the total catch amount during 1975–88 under each harvesting policy are calculated. We concluded that harvesting policies (4), (5), and (6) were effective for the stock conservation and that policies (2), (5), and (6) were effective for increasing the total catch.
A Reliable Tag–Recapture Technique For Estimating Turbine Passage Survival: Application to Young-of-the-Year American Shad (Alosa sapidissima)
Authors: Heisey Paul G. , Mathur Dilip , Rineer Ted
Published: June 2008

A new technique (HI-Z Turb'N Tag, U.S. Patent No. 4,970,988) for estimating turbine passage survival was applied to juvenile American shad (Alosa sapidissima) under three operating conditions at a hydroelectric project. Fish are fitted externally with the Turb'N tag and introduced into turbine penstocks. The Turb'N Tag inflates after turbine passage and buoys fish to the surface for recapture and examination; after removal of tags, fish are held to assess long-term effects. Almost all (96%) test (299) and control (300) fish were recovered; average recovery time was less than 9 min. The overall short-term (1 h) survival of test fish, adjusted for control, was 97%; 24- and 48-h survivals were 98 and 94%, respectively. The 48-h survival of test fish was 98–100% for mixed flow and Kaplan turbines and 66.8% for the mixed flow unit in the vented mode. Acute control mortality was negligible (< 5%). Our technique offers several significant advantages over traditional net recapture methods: applicable to wide range of species and size; allows predetermination of statistically valid sample size, level of significance, and power of the test to determine need for mitigation measures; and estimation of cumulative effects of multiple turbine exposure.
Validation Studies of Daily Increment Formation for Larval and Juvenile Summer Flounder, Paralichthys dentatus
Authors: Szedlmayer Stephen T. , Able Kenneth W.
Published: June 2008

The increment deposition rate in sagittal otoliths of larval and juvenile summer flounder, Paralichthys dentatus, was influenced by growth rate. Larvae of known age showed less-than-daily increment deposition during slow growth (0.1 mm∙d−1), but increment deposition appeared daily after the growth rate increased to 0.4 mm∙d−1. There was no significant difference between counts from larval otoliths made by either scanning electron microscopy or light microscopy. Juveniles collected in the field that were tetracycline marked and held in the laboratory at elevated temperatures (≈15 °C) showed significantly faster growth rates (0.3 mm∙d−1) and daily increment depositon rates compared with growth rates (−0.03 mm∙d−1) and less-than-daily increment deposition rates at ambient temperature (1–11 °C). Tetracycline-marked juveniles, held in cages in a subtidal creek, also showed daily increment deposition. Scale circuli were not deposited daily in the juveniles examined. It appears that daily aging of the youngest P. dentatus larvae is problematic, but after settlement in estuarine nursery areas, increment formation occurs daily.
Mitochondrial DNA Diversity among Lake Superior and Inland Lake Ciscoes (Coregonus artediandC.hoyi)
Authors: Snyder Thomas P. , Larsen Robert D. , Bowen Stephen H.
Published: June 2008

Mitocondrial DNA (mtDNA) of ciscoes from Lake Superior and seven inland lakes in Michigan and New York were analyzed for restriction fragment length polymorphism using 11 informative restriction endonucleases. Five of the 11 enzymes revealed restriction site or size polymorphism among fish. Maximum sequence divergence between mtDNA haplotypes was low (p = 0.006), indicating a maximum divergence time of 300 000 yr. Coregonus artedi and C. hoyi share mtDNA haplotype arrays indicating a more recent divergence. No unique haplotypes exist to separate C. artedi and C. hoyi from single collections, although their arrays of haplotypes are significantly different in frequencies. The lack of qualitative differentiation between C. artedi and C. hoyi noted for mtDNA parallels that previously noted for allozymes and morphology. Introgression between C. artedi and C. hoyi seems unlikely as the cause for this low amount of differentiation because a 100-base pair insertion haplotype present in Lake Superior and inland lake C. artedi is absent in C. hoyi.
Temporal and Spatial Distribution of the Harmful Diatoms Chaetoceros concavicornis and Chaetoceros convolutus along the British Columbia Coast
Authors: Albright L. J. , Johnson S. , Yousif A.
Published: June 2008

The harmful phytoplankters Chaetoceros concavicornis and Chaetoceros convolutus are normal components of the phytoplankton assemblage along the British Columbia coast. During 1988, these diatoms occurred at their highest concentrations in the spring and fall from the Strait of Georgia to Queen Charlotte Strait. North of Queen Charlotte Strait, the maximal concentrations appeared to be delayed until summer. The greatest concentrations occurred in the waters of the Strait of Georgia and its contiguous bays and inlets, especially Jervis Inlet, where concentrations of C. concavicornis and C. convolutus which could be harmful to salmon occurred during the spring and fall of 1988. Lesser concentrations occurred in coastal seawaters north of the Strait of Georgia. These phytoplankters were absent, or were present in only minor concentrations, in inlets with low-salinity waters such as Holberg Inlet and Indian Arm. Harmful Chaetoceros cells were restricted to seawaters greater than approximately 17‰ salinity. Vertically and horizontally well-mixed waters, such as those of Johnstone Strait, also appeared to restrict the presence of these cells. The greatest concentrations of these diatoms occurred during the spring and fall in relatively stratified coastal seawater with salinities between 26 and 34‰.
Genetic Population Structure of American Plaice (Hippoglossoides platessoides) from the Gulf of St. Lawrence, Canada
Authors: Stott Wendylee , Ferguson Moira M. , Tallman Ross F.
Published: June 2008

The genetic population structure of American plaice (Hippoglossoides platessoides) was examined with an electrophoretic analysis of the products of 40 protein-coding loci and with restriction fragment length polymorphisms in mitochondrial DNA. Samples of American plaice collected in the same year from six sites within the Gulf of St. Lawrence showed little heterogeneity in allele frequencies at eight loci. Furthermore, few significant differences in allele frequencies were detected among American plaice collected over three different years from the same site. Also, fish collected from the Grand Banks of Newfoundland showed little genetic differentiation from the Gulf fish. Of the 25 restriction endonucleases used to search for restriction fragment length polymorphisms, only Hind III and Pvu II gave variable fragment patterns. Most fish had the same haplotype and three other haplotypes were represented by two fish at most from each site. American plaice in the Gulf of St. Lawrence appear to be a single, randomly mating population. Large effective population size and high rates of gene flow may account for the observed lack of genetic population subdivision.
Life History of Juvenile Ocean-type Chinook Salmon (Oncorhynchus tshawytscha) in the Situk River, Alaska
Authors: Johnson S. W. , Thedinga J. F. , Koski K. V.
Published: June 2008

Distribution, abundance, habitat preference, migration and residence timing, seawater tolerance, and size were determined for juvenile ocean-type (age 0) chinook salmon (Oncorhynchus tshawytscha) in the Situk River, Alaska. Chinook primarily occupied main-stem habitats (channel edges in spring, pools and willow edges in summer). Peak chinook densities in the upper and lower main stem were 96 and 76 fish/100 m2, respectively. Chinook migrated downstream in two phases: a spring dispersal of emergent fry and a summer migration. Chinook marked in the upper river in late June and early July were recaptured 20 km downstream in the lower river in late July. Marked chinook resided in the lower river up to 34 d. Mean fork length of chinook in the lower river increased from 40 mm in May to 80 mm in early August. By late August, chinook had emigrated from the lower river at a size of approximately 80 mm. Fish this size were seawater tolerant and had the physical appearance of smolts. Ocean-type chinook in the Situk River are unique because in most Alaskan streams, chinook are stream-type (rear in freshwater at least 1 yr).
Numerical Definition of Groundfish Assemblages Caught Off the Coasts of Oregon and Washington Using Commercial Fishing Strategies
Authors: Rogers Jean Beyer , Pikitch Ellen K.
Published: June 2008

Numerical definition of species caught together by the groundfish trawl fishery operating off the Oregon and Washington coasts during 1985–87 indicated six major assemblages of species. Observers on commercial vessels recorded data allowing estimation of the weights of commercially important species caught in each tow. Assemblages were selected based on consistencies in three types of analysis of the species weights: detrended correspondence ordination, two-way indicator species clustering, and Bray–Curtis group average clustering. Two of the assemblages were dominated by a single species, one consisting largely of smooth pink shrimp (Pandalus jordani) and the other primarily of widow rockfish (Sebastes entomelas). The other assemblages identified were a deepwater rockfish assemblage, a deepwater Dover sole assemblage, a nearshore mixed-species assemblage, and a bottom rockfish assemblage. These assemblages of commercially cooccurring species may be treated as units in developing mixed-species management plans. The deepwater rockfish assemblage we identify has not been previously described.
Mitochondrial DNA Diversity in Jackass Morwong (Nemadactylus macropterus: Teleostei) from Australian and New Zealand Waters
Authors: Grewe Peter M. , Smolenski Adam J. , Ward Robert D.
Published: June 2008

The jackass morwong (Nemadactylus macropterus), a commercially valuable marine fish in the Australian–New Zealand region, was surveyed for genetic variation as part of a larger project aimed at clarifying its stock structure. Mitochondrial DNA variation in 166 jackass morwong from seven southern Australian localities was examined using nine restriction enzymes. The 28 haplotypes identified gave an overall nucleon diversity of 0.671. Mean nucleotide diversity per sample was 0.458%, with a (corrected) nucleotide divergence among samples of 0.001%. There was no significant spatial patterning. Five hundred individuals from eight southern Australian localities and one New Zealand locality were examined using three restriction enzymes detecting polymorphic cut sites. The 33 haplotypes identified gave an overall nucleon diversity of 0.635. Mean nucleotide diversity per sample was 1.247%, with a (corrected) nucleotide divergence among samples of 0.002%. No differentiation was detected among the Australian localities. The New Zealand sample showed weak but significant divergence from the Australian samples. These results were similar to those from a concurrent allozyme analysis, and we conclude that there is appreciable nuclear and mitochondrial DNA gene flow among Australian localities, while the Tasman Sea separating Australia from New Zealand acts as a partial barrier.
Littoral Fish Communities in Southern Quebec Lakes: Relationships with Limnological and Prey Resource Variables
Authors: Pierce Clay L. , Rasmussen Joseph B. , Leggett William C.
Published: June 2008

We assessed species richness, biomass, and community type of littoral fish in 10 southern Quebec lakes in relation to several limnological and prey resource variables. Lake, yearly, and seasonal variation in biomass was evaluated by quantitative, replicated seining. Species richness averaged 12.8 in our lakes, and 24 species were collected overall. Total littoral fish biomass averaged 13.5 g∙m−2overall and varied significantly among lakes (range 6.1–26.9 g∙m−2) and between early and late summer. Yellow perch (Perca flavescens), golden shiner (Notemigonus crysoleucas), and pumpkinseed (Lepomis gibbosus) occurred in all lakes and were the most abundant species overall, averaging 57% of the total fish biomass. Principal component ordination of littoral fish communities showed little evidence for aggregation of community types. Species richness was positively correlated with lake surface area (r2 = 0.62), as has been shown in other studies. Total fish biomass was positively correlated with biomass of chironomids (r2 = 0.57), which constituted 24% of the littoral invertebrate biomass in our lakes and are important prey of many fish species. We found no significant correlation between total fish biomass and total invertebrate biomass or between biomass of any of the dominant fish species and limnological or prey variables.
Feasibility of increased biogas production from the co-digestion of agricultural, municipal, and agro-industrial wastes in rural communities
Authors: McDonald Tanya , Achari Gopal , Abiola Abimbola
Published: June 2008

In rural communities, such as Olds, Alberta (population 7248) energy may be produced through anaerobic co-digestion of municipal, agricultural, and agro-industrial wastes. An inventory within a 20 km radius of Olds revealed that 291 000 tonnes of wet organic waste are generated annually (96.8% manure) with an electrical potential of 42 GWh (1 GWh = 106 kWh). Analysis of feedlot, hog, dairy and poultry manure, offal, food, grass, and biosolids identified the potential for waste blending to optimize solids content, nutrient balance, and pH level. In laboratory tests, biogas yield increased from 0.382 m3/kg volatile solid (VS) for feedlot manure alone to 0.513, 0.517, and 0.500 m3/kg VS with co-digestion of 30% hog manure, 15% offal, and 30% offal, respectively. Methane content of biogas increased from 75.8% in feedlot manure digestion to 78.8, 79.5, and 80.9% with co-digestion of 30% hog manure, 15% offal, and 30% offal, respectively.
Heterogeneous modeling of an anaerobic sequencing batch biofilm reactor (ASBBR)
Authors: Cabrera Padilla Rebeca Yndira , Miqueleto Ana Paula , Zaiat Marcelo , Kwong Wu Hong
Published: June 2008

The objective of this study was to estimate the first-order intrinsic kinetic constant (k1) and the liquid-phase mass transfer coefficient (kc) in a bench-scale anaerobic sequencing batch biofilm reactor (ASBBR) fed with glucose. A dynamic heterogeneous mathematical model, considering two phases (liquid and solid), was developed through mass balances in the liquid and solid phases. The model was adjusted to experimental data obtained from the ASBBR applied for the treatment of glucose-based synthetic wastewater with approximately 500 mg L–1 of glucose, operating in 8 h batch cycles, at 30 °C and 300 rpm. The values of the parameters obtained were 0.8911 min–1 for k1 and 0.7644 cm min–1 for kc. The model was validated utilizing the estimated parameters with data obtained from the ASBBR operating in 3 h batch cycles, with a good representation of the experimental behavior. The solid-phase mass transfer flux was found to be the limiting step of the overall glucose conversion rate.
Trace metal analysis of atmospheric particulate matter: A comparison of personal and ambient samplers
Authors: Majestic Brian J. , Schauer James J. , Shafer Martin M. , Fine Philip M. , Singh Manisha , Sioutas Constantinos
Published: June 2008

This study compared the size-resolved trace metal concentrations from a standard ambient sampler to those of three commercial personal samplers. Trace metals data from each personal sampler were also inter-compared. Co-located “fixed site” samples were collected in two urban sites in the United States using three types of personal samplers (BGI PM2.5 cyclone, URG PM2.5 cyclone, and Sioutas™ personal cascade impactor sampler [PCIS]) and one standard ambient sampler fitted with a PM2.5 cyclone. This experimental design enabled direct evaluation of the relative performance of the personal samplers. Results of mass measurements showed good agreement between the standard equipment and personal samplers;; however, trace metal comparisons (measured by ICP–MS) showed reproducible concentration biases among personal samplers. These biases can be summarized as BGI < URG < PCIS (0.27 ± 0.08, 0.72 ± 0.08, and 1.32 ± 0.34 relative to the ambient sampler). Elements exhibiting larger variation between personal samplers were associated with higher mass fractions in the coarse fraction, suggesting the PM2.5 size-cut a potential cause of this deviation.
Formation of silica grout curtains and containments in mineralized groundwater
Authors: Elektorowicz M. , Hesnawi R. , Ayadat T. , Chifrina R.
Published: June 2008

An experimental investigation was conducted to evaluate the performance (as reflected by changes in permeability) of grouted soil specimens subjected to waters of various chemistry (mineralized groundwater) under a gradient of approximately 18. The specimens were composed of pure silica sand and clayey silty sand injected with one of two types of sodium silicate grout (sodium silicate + ethyl acetate-formamide, and sodium silicate + calcium chloride). The grouted specimens were tested in an environment that simulated different waters (distilled, freshwater, and saltwater). This work investigated the effects of curing time, environment, grout contents, and groundwater quality on the behaviour of silicate-grouted specimens, and analysed curtain formation mechanism. The test results showed that sodium silicate with ethyl acetate-formamide (SA) exhibited an increase in permeability when subjected to both freshwater and saltwater. Sodium silicate with calcium chloride (SC), however, maintained permeability properties when subjected to both freshwater and saltwater. The SC grouted specimens are less vulnerable to the action of groundwater than specimens grouted with SA. Furthermore, an empirical correlation relating the permeability of ungrouted and grouted specimens under different conditions was suggested. The correlation includes new defined parameters such as curing effect factor (α) and curtain vulnerability factor (κ).
Black liquor and alkaline shocks in a multiple stage biological treatment plant
Authors: Sandberg Maria , Holby Ola
Published: June 2008

To find the impact that alkaline and black liquor spills have on multiple stage biological treatment plants, trials were made in a MultiBio lab-scale treatment plant. It was shown that the concentration of black liquor was diluted between the multiple stages. The initial bacterial stages were inhibited by high concentration of black liquor but recovered when the concentration decreased. Low pH in the feed contaminated with black liquor gave less inhibition than high pH. In a MultiBio treatment plant the active sludge stages, which are sensitive to toxic spills, are placed after the fast growing bacterial stages and are therefore protected. During normal conditions the activated sludge stages receive low concentrations of biodegradable COD. During the trials extra COD in the form of diluted black liquor induced the COD reduction. To evaluate the results, measured concentrations were compared with a computer model.
Application of carbon dioxide stripping for struvite crystallization — I: Development of a carbon dioxide stripper model to predict CO2 removal and pH changes
Authors: Fattah K.P. , Zhang Y. , Mavinic D.S. , Koch F.A.
Published: June 2008

This research investigated the feasibility of stripping CO2 from the digester supernatant to raise the pH, thereby reducing the caustic chemical usage. In this study, a cascade CO2 stripper was first designed and tested, with three different synthetic solutions in a struvite recovery, crystal reactor: (1) tap water saturated with CO2, (2) NaHCO3 solution saturated with CO2, and (3) NaHCO3 + NH4Cl solution saturated with CO2. It was found that the removal efficiency of the CO2 stripper was dependant on several parameters, such as the characteristics of the influent, including total alkalinity, temperature, and initial concentration of dissolved CO2 gas, influent flow rate, effluent recycle rate, aeration rate, and baffle numbers in the stripper. Based on the performance of the stripper on the three synthetic solutions, a CO2 stripping model was developed using these parameters. This model was subsequently tested in a pilot-scale facility, to predict the amount of CO2 removal possible.