bluuebunny/crossref_metadata_2025 huggingface dataset:
Origin and Geography of the Fish Fauna of the Laurentian Great Lakes Basin
Authors: Bailey Reeve M. , Smith Gerald R.
Published: May 2008

The native fishes of the Great Lakes basin consist of 153 species, 64 genera, and 25 families. The total ichthyofaunal lists for the several lakes and (in parentheses) their tributary basins are as follows: Nipigon (and tributaries), 40; Superior, 53 (82); Michigan, 91 (135); Huron, 90 (112); St. Clair and Detroit River 108; Erie, 106 (125); Ontario, 95 (125). (These totals include 21 introduced species, most named species of ciscoes and chubs, and the blue pike (Stizostedion vitreum glaucum).)Several areas show notable within-species differentiation. Tributaries to Lake Ontario are part of a zone of secondary contact of a few small, nonmanaged, subspecies that entered the basin from both eastern and western glacial refugia. In the Great Lakes themselves, stocks of lake trout (Salvelinus namaycush), ciscoes, walleyes (Stizostedion vitreum vitreum), and a few nonmanaged species stem from differentiation within the basin or reflect interglacial events that occurred in Mississippi refugia.Species distribution patterns suggest colonization of the Great Lakes by 122 kinds solely from Mississippi basin refugia, 14 kinds only from Atlantic drainage refugia, and dual refugia for at least 18 kinds. Geological evidence provides some support for this interpretation. It is unlikely that any species colonized the Great Lakes from an Alaskan refuge in the past 14 000 yr.The ciscoes and chubs of the genus Coregonus include numerous genetically differentiated stocks, some of which may predate the opening of the Great Lakes in the past 14 000 yr. This conclusion is based on the occurrence in Lake Nipigon and Lake Superior of several forms that must have colonized prior to 9000 yr ago when the last access existed from Lake Superior to Lake Nipigon. At least four and perhaps up to eight forms of Great Lakes coregonines probably survived (or differentiated during) the last glaciation south of the ice in proglacial waters at the heads of major river systems. There is no evidence to support the hypothesized post-Wisconsinan dispersal of any of these forms from a northwestern refugium or their Pleistocene derivation by introgression with a Eurasian species.Despite the evidence for some long-standing genetic differentiation within Coregonus, morphological and biochemical characters fail to support the unequivocal recognition within the Great Lakes of more than one to four current biological species (apart from clupeaformis). The presently recognized species are groups of stocks whose position in the classification system is problematical. The named groups (two of which are extinct) included numerous stocks that were (or are) isolated by homing behavior specific to time and place. The lack of intrinsic reproductive isolation among forms increases their vulnerability to extinction because rare forms apparently hybridize with common forms spawning at adjacent times or places.Key words: biogeography, Coregonus, fish, Great Lakes, introduced fishes, Pleistocene, species, subspecies
Genetic Perspectives of the Identification and Conservation of Scandinavian Stocks of Fish
Authors: Ryman Nils , Ståhl Gunnar
Published: May 2008

Intraspecific planting and introduction of new species of fish has been much more restricted in northern Scandinavia than in many other parts of the world. Further, the general geography, with a large number of independent drainages and numerous impassable waterfalls, often prevented extensive spread of planted freshwater fish. Therefore, the genetic patterns observed among Scandinavian populations, e.g. their structure and the amount of distribution of genetic variation, may more accurately picture a natural situation than that reflected by stocks which have been influenced by a variety of fishery management activities. Natural populations of Scandinavian salmonids seem to be characterized by a more apparent subdivision than is usually observed, and multiple cases of genetically distinct sympatric demes have been identified within many species. Detailed electrophoretic analyses of natural populations have revealed the existence of previously unrecognized reproductive units exhibiting quite different ecological and morphological characteristics. At least in the brown trout (Salmo trutta), these units seem to have evolved independently, and there are no indications that they reflect the existence of two or more widespread sub- or sibling-species. In several cases attempts to preserve, in hatcheries, the genetic characteristics of endangered or unique remnant natural populations have proven unsuccessful; genetic changes and loss of genetic variability have occurred during the stocking. There is also strong evidence that planted hatchery fish have hybridized and drastically altered the genetic composition of valuable remnant natural populations. We discuss the ecological and fishery management implications of these findings and indicate some of the problems which we consider important to be addressed in future research.Key words: genetic characteristics, Scandinavian salmonids, sympatric demes, identification, conservation
Stocks of Atlantic Salmon (Salmo salar) in Britain and Ireland: Discreteness, and Current Management
Authors: Thorpe J. E. , Mitchell K. A.
Published: May 2008

The null hypothesis that all Atlantic salmon (Salmo salar) in the North Atlantic belong to a common stock is shown to be untenable, on the grounds of differences between North American and European populations in transferrin gene frequencies, chromosome numbers, and numbers of circuli on scales. The further hierarchical breakdown of the European fraction into western, northern, and Baltic components is revealed through tagging data, which also shows distinctions within the western group, segregating into Icelandic, French, and British/Irish subpopulations. Within the latter, two groups are definable on the basis of differences in transferrin (Tf2) gene frequencies, the boreal and celtic races. Within the Celtic race, the populations of the neighboring rivers Bandon and Blackwater (Cork) have been shown to be distinct reproductively isolated stocks, on the basis of differences in gene frequencies in two enzymes (IDH-A, and AAT-A). Circumstantial evidence for the separate identity of 74 river stocks in Britain and Ireland, on the basis of differences in age structure at the smolt and adult stage, and size at return to the rivers, is supported by evidence from tagging experiments of a high incidence of homing to the native river, experimental evidence of the heritability of growth and developmental traits, and evidence from scale data of differences in specific growth rate of individual river populations during their 1st year at sea. Environmental pressures selecting for differences between river stocks are suggested by the significant positive correlation between river length and fish size at maturity. Differences in patterns of change in the commercial catch over the period 1952–76 indicate regional groups of river stocks within Scotland. The existence of such discrete stocks of Atlantic salmon implies the need for management on a stock-by-stock basis. Current national and international regulations do not achieve this goal.Key words: Atlantic salmon, transferrin gene frequencies, river stocks, management
Applications of the Stock Concept to Fish Populations in the USSR
Authors: Altukhov Yu. P. , Salmenkova E. A.
Published: May 2008

Genetic studies of several species of marine fish conducted for over 20 years are reviewed for their application to the problem of intraspecific differentiation of fish. Cyto-physiological, biochemical, and immunological methods were used. By each of these, two sizes of Black Sea horse mackerel (Trachurus mediterraneus) were shown to be sibling species and not local stocks. Similarly, North Atlantic redfish Sebastes marinus and S. mentella were found to be separate species, in agreement with known morphological and ecological differences. In Pacific salmon, genetic markers were used to distinguish planted chums from native stocks, and indicated that such populations are maximally adapted to their historic environment. Stock differences are less apparent in pinks, but are sufficient to suggest subpopulation structure. Genetic differences are found in adjacent generations in odd and even years. Subdivision was most pronounced in sockeye salmon (Oncorhynchus nerka). Spring sockeye spawning in streams were more subject to selection pressure than were summer stocks spawning in lakes. In Atlantic salmon (Salmo salar), spawning in rivers of northern European USSR, the majority showed genetic subdivision during the spawning run. North Sea herring (Clupea harengus) tested by hemagglutination reactions showed differences that coincided with ecological subdivision at spawning, for winter–spring oceanic, summer–autumn marine, and spring–summer coastal herring. Electrophoretic determinations supported these differences. In European anchovies (Engraulis encrasicholus), stocks were differentiated by blood groups, even in the absence of spatial isolation. All of these findings indicate that elementary fish populations play an important role in differentiation and integration of the species gene pool. Efficient management of fish stocks is based on preserving the hereditary heterogeneity of their populations.Key words: genetic markers, stock differences, immunological, biochemical, physiological, intraspecific differentiation
Atlantic Salmon (Salmo salar) Stocks and Management Implications in the Canadian Atlantic Provinces and New England, USA
Authors: Saunders Richard L.
Published: May 2008

This paper discusses the diversity of Atlantic salmon (Salmo salar) expressed as anatomical, physiological, and behavioral differences among stocks in the Atlantic Provinces of Canada and New England, USA. Evidence is reviewed for environmental and genetic influence on a number of stock-specific traits. Unique qualities of particular stocks are described. The loss of salmon from much of its former range is documented and discussed in relation to stock characteristics important in rehabilitation efforts. The mixed stock fisheries in Greenland and Newfoundland are considered from the point of view of interception. It is concluded that identification and management of specific stocks in the Greenland fishery are impracticable at present but that identification of North American components, using discriminant function analysis of scale growth patterns and smolt tagging, should be continued. In Newfoundland knowledge gained from tagging studies allows a significant degree of management of stocks from mainland Canada together with those from Newfoundland and Labrador. Since it is impracticable now to manage the fisheries off Greenland and Newfoundland and off the major Canadian Maritimes salmon-producing rivers—the Miramichi, Restigouche, and Saint John—in strict recognition of stocks, it is suggested that it may be possible to characterize an assemblage of like stocks from given areas and to identify and manage for these in large mixed-stock fisheries. Possible impacts of hatchery plantings are discussed in relation to prospects of success and effects on native stocks. It is concluded that we have the biological basis for evaluating likelihood of success and degree of danger to native stocks from extensive plantings of hatchery-reared juvenile salmon and that such evaluation should be conducted when embarking on projects involving use of hatchery-reared fish as part of a major salmon enhancement program in Atlantic Canada.Key words: genetics, environmental influence, rehabilitation, enhancement, interception, hatcheries, aquaculture
Biological Criteria for Definition of Species and Distinct Intraspecific Populations of Anadromous Salmonids Under the U.S. Endangered Species Act of 1973
Authors: Utter Fred M.
Published: May 2008

The validity of most recognized species of salmonids under the biological species concept is supported by evidence from diverse sources. However, the specific status of a number of recently diverged populations remains uncertain. In the United States, it is particularly important to consider the possibility of unrecognized reproductively isolated populations for protection under the U.S. Endangered Species Act of 1973 (ESA).Innate life history differences among species as well as numerous uncertainties within species preclude the use of a generalized model based on homing as the sole or primary means of defining discrete population segments of anadromous salmonid species. A process involving successive samplings, analyses, and syntheses of data from populations of a particular area is suggested. A major requirement of this process is reliable genetic data. The capability for the detection of allelic proteins by electrophoretic methods has provided a major tool for identifying and measuring genetic differences among populations and species. These data are necessary, but often insufficient for identifying most population segments and must be complemented by other biological and life history data as well as by historical and geological information. Provisional classifications of threatened or endangered populations on the basis of incomplete data may be necessary in many instances, but final classifications should depend on complete sets of data.Transplanted and hatchery populations complicate the identification and management of anadromous salmonid populations under the ESA. Some evidence is cited that indicates a potential or actual adverse genetic effect of hatchery or transplanted fish on some native populations, and current studies designed to measure such effects are mentioned. The technical and economical feasibility for measuring these effects suggest that such measurements should be a requisite for new or extended transplantation and hatchery operations.Further data are needed to determine whether or not threatened or endangered species and populations can be artificially perpetuated and still retain the capability to adapt to wild environments upon reintroduction to native habitats. This capability apparently exists in some domesticated strains of rainbow trout (Salmo gairdneri). However, large differences exist in the intrinsic levels of genetic variation between most domesticated populations of rainbow trout and many threatened or endangered natural populations of salmonids.Key words: criteria, intraspecific, anadromous salmonid populations, genetic data
The Stock Concept and its Application to British Columbia Salmon Fisheries
Authors: McDonald J.
Published: May 2008

The application of the stock concept to the management of British Columbia salmon fisheries is examined in an historical context. Early recognition of the distinctiveness of runs proceeding to different rivers led to the management principle that stocks should be harvested at a rate commensurate with their abundance level and their particular reproduction rate. Past and current work has been directed largely to applying this principle and included stock identification and estimates of abundance (catch and escapement) and of age composition. However, the application of the stock concept to management has been fraught with difficulties mainly because of the large number of stocks involved, the increasing catching power of the fishing fleet, and its displacement into fishing areas where stocks are mixed extensively. Some options for future management strategies are considered, but prospects for the maintenance of all but the most productive stocks seem dim.Key words: Pacific salmon, stock concept, management, fisheries, stock–recruitment relationship
Significance of the Stock Concept in Artificial Propagation of Salmonids in Alaska
Authors: Helle John H.
Published: May 2008

Hatcheries could make a significant contribution to the enhancement of salmonid fisheries if application of this technology is based on principles of the stock concept. Evidence for the stock concept is reviewed and discussed in relation to transplantation of stocks, mating procedures, maintenance of genetic diversity, different methods of artificial propagation, and location of artificial propagation facilities. A strategy is developed for management of both wild and artificially propagated stocks.Key words: hatcheries, salmon, stock concept, genetics, artificial propagation
Survival, Growth, Spawning Distribution, and Movements of Introduced and Native Lake Trout (Salvelinus namaycush) in Two Inland Ontario Lakes
Authors: MaClean J. A. , Evans D. O. , Martin N. V. , DesJardine R. L.
Published: May 2008

This paper attempts to develop a biological basis for the management of stocks of lake trout (Salvelinus namaycush). Recent studies of the influence of genetic differences on the survival of planted stocks of trout and of the spatial distribution and movements of lake trout populations are reported. The genetic origin of planted lake trout influenced their survival in four Ontario lakes, whereas water hardness of the rearing hatchery had little effect. Survival also appeared to be influenced by the status of the native population but growth rates of native and introduced trout were similar. Age of first maturity appeared to differ between stocks in Lake Simcoe. Studies with both numbered and sonic tags in Lake Opeongo suggested that lake trout do not home to their natal shoal. Differences in total distances travelled were observed between sexes, but both males and females moved between shoals at spawning time. In Lake Simcoe, planted trout dispersed widely, colonizing spawning shoals up to 30 km from release sites, and no differences between stocks in time of spawning could be detected despite apparent differences in the home lakes. Temperature influenced spawning time and accounted for most of the timing variation between two allopatric lake trout stocks.Key words: lake trout, native, introduced, survival, growth rate, spawning distribution, movement, homing
Performance of Indigenous, Exotic, and Hybrid Strains of Brook Trout (Salvelinus fontinalis) in Waters of the Adirondack Mountains, New York
Authors: Webster Dwight A. , Flick William A.
Published: May 2008

Eleven year-classes of wild, domestic, and wild × domestic hybrid strains of brook trout (Salvelinus fontinalis) were stocked in a 0.19-ha Adirondack pond. Comparative survival and growth were assessed upon drainage in early fall. Rearing native wild strains to maturity in a hatchery, or domestic strains in a natural environment, did not consistently or materially affect survival of progeny, suggesting that superior performance of wild strains was largely inherent. Interstrain hybrids of wild × domestic showed survivals equivalent to the wild parents, but hybrids of two Canadian strains gave evidence of heterosis in both survival and net yield. Supplementary observations in other waters also indicated that one strain (Assinica) may be less adaptable to Adirondack conditions than the other (Temiscamie).Key words: brook trout, wild trout, domesticated trout, interstrain hybrid trout, survival, growth, heterosis, hybrid vigor
Native Lake Trout (Salvelinus namaycush) Stocks in the Canadian Waters of Lake Superior Prior to 1955
Authors: Goodier John L.
Published: May 2008

The decline of Lake Superior lake trout (Salvelinus namaycush) stocks after the sea lamprey (Petromyzon marinus) population explosion of the 1950s was both dramatic and decisive. Few native stocks remain to permit scientific data collection. However, interviews with old-time commercial fishermen suggest that there had existed many discrete or semi-discrete stocks within the lake. Historical documents in the form of government correspondence and reports, explorers' accounts, and Hudson's Bay Fur Co. records yield further evidence.Possible stocks are distinguished on the basis of anatomical features (including weight, body shape, and coloration) and behavioral differences (including seasonal movements and spawning habits). The relevance of these criteria for stock identification is discussed.Fishermen distinguished four general categories of S. namaycush: leans, fats or siscowets, half-breeds, and humpers or paperbellies. In addition, different "breeds" or forms of lean trout were commonly recognized. Often a form was known by a name referring to its most distinctive feature: blacks, redfins, yellowfins, grays, salmon-trout, red trout, moss trout, sand trout, and racers. These varieties are discussed and local spawning habits, grounds, and movements are summarized with maps, tables, and text. At least 200 former spawning grounds are identified, including 20 rivers which were once characterized by September runs of lake trout. Spawning locations for the deep-water, nonlean trout variants (paperbellies, half-breeds, and siscowets) are less easily discovered. Approximately 35 fishing grounds are noted, with spawning reported at 4 of these. Consideration is given to the possible existence of phenotypically distinct stocks of siscowet.Key words: lake trout, Salvelinus namaycush; stocks, anatomical features, behavioral differences
Life History and Timing of Migrations and Spawning Behavior of Rainbow Trout (Salmo gairdneri) Populations of the Great Lakes
Authors: Biette R. M. , Dodge D. P. , Hassinger R. L. , Stauffer T. M.
Published: May 2008

Rainbow trout (Salmo gairdneri) populations of the Great Lakes showed a great variability in timing of spawning migrations and life histories. This variability was examined to determine if rainbow trout populations of the Great Lakes are comprised of discrete stocks. Differences in timing of migration and spawning indicated that at least one spawning population may be distinctive and that others may be in progressive stages towards emergence of discrete stocks. The innate ability of this species to adapt to different environmental conditions, together with its ability to 'home,' provide rainbow trout in the Great Lakes with the potential to develop discrete stocks. The management of this species that allows for the development of this potential is emphasized.Key words: rainbow trout. Great Lakes, stocks, migrations, spawning, life histories, homing
Lake Whitefish (Coregonus clupeaformis) Stocks of the Ontario Waters of Lake Huron
Authors: Casselman J. M. , Collins J. J. , Grossman E. J. , Ihssen P. E. , Spangler G. R.
Published: May 2008

Historical and contemporary data on lake whitefish (Coregonus clupeaformis) from the Ontario waters of Lake Huron were examined for evidence of stocks with the objective of defining population boundaries. We delineated the spatial distribution of five stocks from tag–recapture data and the general location of six additional stocks on the basis of population parameters such as growth rate, age structure, and abundance trends.Samples of fish collected (summer and fall) from 5 of the 11 potential stocks were evaluated on the basis of 11 morphometric and 7 meristic characters. We also examined osseometric features such as shape of scales and otoliths, and electrophoretic characteristics at 32 loci associated with 12 enzyme systems.The summer and fall samples for each group were generally not significantly different. For the phenotypes examined electrophoretically, each stock was in Hardy–Weinberg equilibrium; 12 of the 32 loci considered were polymorphic and 4 of the 10 possible genetic distances differed significantly from zero.The Inner Basin stock was distinctly different from all other stocks. The Blind River stock was also found to be different by osseometrics, but not by morphometrics or electrophoresis. Osseometrics separated the stocks by basin of origin. Two stocks, Outer Basin and Burnt Island, appeared to be the most similar and could be separated from each other only on the basis of growth rate and tagging data. These two stocks are adjacent to each other in the main basin of Lake Huron, along the south shore of Manitoulin Island.Whitefish stocks of Lake Huron represent groups of fish that differ phenotypically and genotypically in varying degrees, are spatially separated, and behave as cohesive units. We conclude that they should be regarded as functional units for management purposes.Key words: lake whitefish, Coregonus clupeaformis, Lake Huron, stocks, tag–recapture data, population structure, morphometrics, meristics, osseometrics, scale and otolith shape, starch gel electrophoresis, biochemical genetic variation
A Wild Salmon, Trout, and Char Watch: An International Strategy for Salmonid Conservation
Authors: Maitland P. S. , Regier H. A. , Power G. , Nilsson N. A.
Published: May 2008

This paper elaborates an international strategy to register and monitor stocks of wild salmon, trout, and char through the Holarctic region. The urgent need for such a watch has been emphasized by the increasingly international nature of environmental pollution and stress (e.g. acid precipitation), and the fact that several local 'watch-like' schemes have recently arisen independently in different countries. The main objective of a watch is to foster the conservation of distinct species and stocks of wild salmonids and their habitats by an international program of monitoring and information exchange. At intervals a global wild salmonid status report would be produced for public release. The watch would be developed through an international network of interested parties and organized by a steering committee, probably set up within an existing international organization.Key words: wild salmon, trout, char, watch, worldwide strategy, stock conservation
Cost of Sustained and Burst Swimming to Juvenile Coho Salmon (Oncorhynchus kisutch)
Authors: Puckett K. J. , Dill L. M.
Published: May 2008

The relationship between oxygen consumption rate (milligrams per kilogram per hour) and sustained swimming speed (calculated from tailbeat frequency) was determined for 1.2-g juvenile coho salmon (Oncorhynchus kisutch) at 15 °C. The data are best described by the following equation: log oxygen consumption rate = 2.2 + 0.13 (body lengths-s−1). This relationship is very similar to that extrapolated for sockeye salmon (O. nerka) of the same size, thus potentially enabling researchers to utilize the extensive sockeye data base to predict metabolic rates of coho. The oxygen consumption rate during burst swimming (9 body lengths∙s−1) was also determined. The burst swimming metabolic rate (38 000 mgO2∙kg−1∙h−1) is nearly 40 times greater than the maximum sustained swimming metabolic rate.
Changes in Elemental Composition of Hatchery-Reared Rainbow Trout,Salmo gairdneri, Associated with Growth and Reproduction
Authors: Shearer Karl D.
Published: May 2008

By examining a group of rainbow trout (Salmo gairdneri) over their life cycle (ova to 1500 g), 1 found that their elemental composition was determined by fish size, stage of life cycle (prefeeding, juvenile, post-juvenile), and reproductive state. Fish were fed practical diets and were reared under hatchery conditions. Whole body elemental concentrations of Ca, Cu, Fe, K, Mg, Mn, Na, P, Sr, and Zn were size dependent prior to sexual maturity. Rates of elemental accumulation in relation to weight gain were higher in juveniles than in adult fish. Reduced somatic concentrations of Mn, Fe, and Zn were observed during gonad maturation in female but not in male trout. Tissue concentrations of some elements remained constant over the duration of the study, while others increased or decreased linearly with increasing fish size. Tables and equations 1 present will enable the normal tissue and whole body elemental composition of rainbow trout at any size to be determined. My results indicate that body burden or wet weight concentration are better indicators of elemental status than dry weight concentration and that comparison of elemental levels between treatment groups in dietary experiments should be made on the basis of a standard-sized fish or by comparing the rates of elemental deposition with growth.
Importance to Mussels of the Benthic Boundary Layer
Authors: Wildish D. J. , Kristmanson D. D.
Published: May 2008

We examined whether populations of the blue mussel Mytilus edulis (Linnaeus, 1758) and horse mussel Modiolus modiolus (Linnaeus, 1758) could, by their feeding activities, deplete the sestonic food supply. The experiments were conducted in a 5-m-long by 50-cm-wide flume in which a turbulent boundary layer flow was created. The seston concentration was measured both as ATP content and numbers of bacteria by acridine orange staining technique on separate subsamples of seawater. Sampling locations were at the flume inlet and at a point 3.6 m downstream (outlet). Four of the five replicated experiments with blue mussels had significant ATP–seston depletion but no reduction in bacterial numbers at the outlet sampling location. Of three replicated experiments with horse mussels, two had significant ATP–seston depletion and all three had significantly fewer bacterial numbers at the outlet sampling location. We consider that these results provide direct evidence in support of the hypothesis that seawater hydrodynamic factors may be critical in determining the food supply available to suspension-feeding animals. Our results confirm circumstantial evidence on this point obtained from field observations by previous investigators. Experimental verification of seston depletion is a necessary, but not sufficient, step in establishing that suspension-feeding animals may be food limited as required by the trophic group mutual exclusion hypothesis.
Phosphorus Flux through Epilimnetic Zooplankton from Lake Ontario: Relationship with Body Size and Significance to Phytoplankton
Authors: Taylor W. D.
Published: May 2008

The flux of phosphate through epilimnetic zooplankton from Lake Ontario was measured by adding 32PO4 into whole lakewater, monitoring its accumulation by zooplankton over 48 h, and then measuring its release when animals were returned to unlabelled lake water. Phosphorus uptake was calculated as the sum of accumulation and release rates. The 10 species examined ranged in size from 36-μm Codonella cratera to 1-mm Daphnia retrocurva. Phosphorus uptake rates of herbivorous zooplankton ranged about 200-fold and increased with body size both within and among species, although not proportionally. Among species, there was a pronounced allometry, with smaller species having much higher rates per unit size. This allometry is similar to that described for other metabolic parameters and body size. There was no tendency for smaller species to release a greater fraction of the label they took up. These results suggest that the biomass of zooplankton consuming a given phytoplankton production will be much smaller if small zooplankton dominate, and therefore, this phosphorus sink will be much smaller. Further, the flow of phosphorus to higher trophic levels may be reduced. The result of changing the zooplankton size-distribution may be to change the amount of spring total phosphorus available to summer phytoplankton.
Growth Histories of Larval Redfish (Sebastes spp.) on an Offshore Atlantic Fishing Bank Determined by Otolith Increment Analysis
Authors: Penney Randy W. , Evans Geoffrey T.
Published: May 2008

Larval redfish, Sebastes spp., were collected for growth analysis on Flemish Cap, an offshore bank approximately 400–500 km east of insular Newfoundland, Canada. There is evidence that larval redfish form one sagittal growth increment daily, starting the day of extrusion from the mother. Length increases linearly with both age and sagittal radius. The mean daily growth rate was 0.16 mm/d in 1980 and 0.11 mm/d in 1981. Length at extrusion varied with date of extrusion in both years. Individual growth histories, inferred from measurements of sagittal radii, varied considerably with age and extrusion date. Larvae typically grew slowly for 10–15 d after extrusion and then rapidly for 60–70 d before slowing as they entered the pelagic juvenile stage.
Influence of Temperature and Current Speed on the Swimming Capacity of Lake Whitefish (Coregonus clupeaformis) and Cisco (C.artedii)
Authors: Bernatchez Louis , Dodson Julian J.
Published: May 2008

We tested the influence of temperature and water velocity on metabolic rate and swimming performance of lake whitefish (Coregonus clupeaformis) and Cisco (C. artedii) using respirometry techniques. Tests were conducted at 5, 12, and 17 °C (speed range 20–102 cm∙s−1) for fake whitefish and at 12 °C (speed range 20–63 cm∙s−1) for cisco. Fish lengths ranged from 10 to 39 cm (TL). The net aerobic cost of swimming, obtained by subtracting standard from total oxygen consumption, was twice as high for cisco as that for lake whitefish at any swimming speed. However, the standard metabolic rate of lake whitefish was almost the double that of cisco acclimated to the same temperature. Values of metabolic scope for activity coupled with the net cost of swimming showed that coregonines were not good performers compared with most salmonids. The active metabolic rate, scope for activity, and critical swimming speed for lake whitefish were maximal at 12 °C and minimal at 5 °C. Swimming endurance of lake whitefish decreased logarithmically with swimming speed and was reduced at low temperature, the distance traversed at any given swimming speed being minimal at 5 °C. Our results support the hypothesis that the combined effect of high water velocities and low ambient temperature on coregonines' metabolism and swimming performance may be a more important factor than specific spawning temperature in the timing of the early reproductive migration of anadromous coregonines in the Eastmain River, James Bay.
Response of Biological Acoustic Backscattering to Ships' Lights
Authors: Sameoto D. , Cochrane N. A. , Herman A. W.
Published: May 2008

The response of zooplankton (copepods and euphausiids) and micronekton (myctophids) to ships' lights was quantitatively assessed in terms of the acoustic backscattering from these organisms under controlled sea surface illumination. Two frequencies, 51 and 198 kHz, were utilized. No acoustic response to light on stations off the edge of the Nova Scotia continental shelf was found but a strong response on the shelf was observed. The response at both frequencies consisted of a nearly instantaneous drop in volume back-scattering strength by as much as 20 dB in the top 60 m. Biological sampling tentatively suggested that the organisms responsible were euphausiids and that a sudden geometric reorientation when the light was turned on resulted in a drop in their target strength.
Frequency of Increment Formation on Sagittae of North Pacific Albacore (Thunnus alalunga)
Authors: Laurs R. M. , Nishimoto R. , Wetherall J. A.
Published: May 2008

An examination of sagittae from 116 albacore (Thunnus alalunga) caught in the North Pacific, injected with tetracycline, tagged, released, and subsequently recaptured in sport and commercial fisheries showed that detectable increments are formed on these otoliths at an average rate of 0.954 per day. We take this as a confirmation of daily increment formation in North Pacific albacore sagittae. The slight departure of observed mean increment counts from the expected rate of one per day may be due to an occasional interruption of otolith growth, or to a systematic bias in detecting daily increments or interpreting otolith microstructure. The estimated rate of detectable increment formation applies explicitly to albacore of fork lengths between about 50 and 100 cm. If the same rate holds for fish smaller than 50 cm, as is likely, most albacore taken in sport or commercial catches can be aged accurately by applying our methods and expanding the increment count by 5%.
Effects of Increases in Freshwater Temperature on Loss of Smolt Characteristics in Atlantic Salmon (Salmo salar)
Authors: Duston J. , Saunders R. L. , Knox D. E.
Published: May 2008

Two-year-old (2+) Atlantic salmon (Salmo salar) raised under ambient temperature and simulated natural photoperiod (45°N) completed smolting between February and May, exhibiting significant increases in gill Na+, K+-ATPase activity and salinity tolerance (96 h, 37.5 ppt) but no significant changes in plasma osmolality. On May 2 the smolts were divided into four groups (each n = 80) and subjected to a rapid (2–3 h) increase in temperature from ambient (5 °C) to 10, 13, or 16 °C or remained ambient (control) which rose to 12 °C by the end of the experiment on June 5. In the 10, 13, and 16 °C groups, mean gill Na+, K+-ATPase activity (micromoles inorganic phosphorus per milligram protein per hour) declined significantly from 6.6 units on May 2 to 4.3, 3.6, and 2.3 units, respectively, on May 23. In the control group, Na+, K+-ATPase activity showed no significant changes during the study. Plasma osmolality was maintained in all groups between 290 and 304 mosmol∙kg−1. Salinity tolerance tests revealed a significant decline in survival in the 16 °C group from May 2 and in the 10 °C, 13 °C, and control groups from May 13, but no significant differences were observed among the three groups. The results support the hypothesis that increases in freshwater temperature accelerate the loss of hypoosmoregulatory capacity.
Long-Term and Short-Term Arsenate Toxicity to Freshwater Phytoplankton and Periphyton in Limnocorrals
Authors: Wängberg Sten-Åke , Heyman Ulf , Blanck Hans
Published: May 2008

A short-term photosynthesis test employing phytoplankton or periphyton communities was a good predictor of the concentration of arsenate that affected these microalgal communities under long-term arsenate exposure in limnocorrals. Arsenate stress changed the structure of the communities to a more tolerant species composition which was consistent with the concept of pollution-induced community tolerance (PICT). The results involving phytoplankton and periphyton in a phosphorus-limited forest lake corroborated earlier findings from the marine environment. Microalgae from the lake were, however, about one order of magnitude more sensitive than the marine communities, probably because these algal communities primarily were limited by phosphorus instead of nitrogen. The observed arsenate toxicity indicated that the natural background of arsenic may already be a structuring factor for the microalgal communities in several freshwater environments.
Stream Ecosystem Recovery Following a Catastrophic Debris Flow
Authors: Lamberti Gary A. , Gregory Stanley V. , Ashkenas Linda R. , Wildman Randall C. , Moore Kelly M. S.
Published: May 2008

We studied recovery processes for 3 yr in Quartz Creek (Cascade Mountains, Oregon), a third-order stream catastrophically impacted by a February 1986 debris flow for which both predisturbance data and an upstream control reach were available. The debris flow altered channel geomorphology and destroyed riparian vegetation for 500 m, resulting in a reach with short, disordered channel units, low hydraulic retention, and an open canopy. High irradiance levels and reduced grazing by macroinvertebrates contributed to rapid accrual of benthic algae in the disturbed reach, which formed the bioenergetic basis for ecosystem recovery. Macroinvertebrates (mostly herbivores) recovered to upstream densities and taxonomic richness within 1 yr, although effects on community structure persisted into the second year. Cutthroat trout (Oncorhynchus clarki) populations were locally decimated by the disturbance, but by the following year, recruitment of young-of-the-year trout into the reach exceeded that of the upstream reach and populations had recovered to predisturbance densities. Despite the general rapid recovery of the biota within the disturbed reaches, most populations showed broad temporal fluctuations in abundance, suggesting that ecosystem stability was diminished by the debris flow. Long-term monitoring of Quartz Creek may yield additional insight into the role of episodic disturbance in stream ecosystems.
Salinity Tolerance and Osmoregulation in the Nemertean Pseudocarcinonemertes homari, an Egg Predator of American Lobster, Homarus americanus
Authors: Charmantier G. , Charmantier-Daures M. , Waddy S. L. , Aiken D. E.
Published: May 2008

The salinity tolerance and osmoregulation of Pseudocarcinonemertes homari were determined to develop a method for elimination of this nemertean from egg masses of American lobster, Homarus americanus. The lower and upper lethal salinities (LS50) for nemerteans are 11 and 45‰ at 7 °C and 19 and 37‰ at 14.5 °C. Immersion in freshwater was lethal in 4 min or less, depending on temperature. The nemerteans hyperosmoconformed over the range 10–1600 mosm∙kg−1. Lobster eggs (eye index [Formula: see text]) survived for 2–8 h when immersed in freshwater. Ovigerous lobster were not affected by a 5-min immersion in freshwater and were able to withstand at least 30 min if only the abdomen was immersed. Lobster eggs hatched and larvae developed normally up to at least stage IV, even after a 30-min freshwater immersion. These results suggest that nemerteans could be eliminated from American lobster by immersing their abdomen and attached eggs in freshwater for 5 min and immersing the entire lobster for an additional 5 min.
Downstream Effects of Mine Effluent on an Intermontane Riparian System
Authors: Moore Johnnie N. , Luoma Samuel N. , Peters Donald
Published: May 2008

Metal concentrations were determined in benthic biota, fish livers, water, and fine-grained sediment through 215 km of an intermontane river system (Blackfoot River, Montana, USA) affected by headwater inputs of acid-mine effluent. Solute and particulate contaminants decreased rapidly downstream from headwater sources, but some extended through an extensive marsh system. Particulate contaminants penetrated through the marsh system, effectively resulting in food web contamination downstream of the marshes. Metals differed in their bioavailability within and below the marsh system. Cadmium was most consistently accumulated in the food web, and the general order of downstream mobilization of bioavailable metals appears to be Cd, Zn > Cu > As, Ni. Depauperate benthic communities and reduced fish populations occurred coincident with the sediment contamination.
Arginine Vasotocin, an Osmoregulatory Hormone, as a Potential Indicator of Acid Stress in Fish
Authors: Hontela A. , Rasmussen J. B. , Ko D. , Lederis K. , Chevalier G.
Published: May 2008

Brook trout (Salvelinus fontinalis) exposed for 1 wk to pH 5.6 (sublethal acidity) exhibited higher forebrain and pituitary arginine vasotocin (AVT) levels and lower plasma Na+ levels than fish exposed to pH 6.7 (control). Addition of 300 μg total Al/L to water at pH 5.6 did not augment the effect on either the plasma Na+ or the AVT levels. Exposure to demineralized water for 1 wk lowered the plasma Na+ and increased AVT in the forebrain but had no effect on pituitary AVT. The increased AVT levels could be used as early warning indicators of sublethal acid stress in the brook trout. Such indicators, used in wild fish, might become important tools in management of trout lakes in areas threatened by acidification.
Habitat Partitioning and Contaminant Exposure in Cyprinids
Authors: Hebert Craig E. , Haffner G. D.
Published: May 2008

Four species of forage fish from the Huron–Erie corridor — Labidesthes sicculus, a surface feeder; Notropis atherinoides, a facultative surface feeder; Notropis hudsonius, a facultative benthivore; and Pimephales notatus, a benthivore — were found to have significantly different levels of organochlorine contaminants with high 1-octanol/water partition coefficients (Kow). Chemical levels were greatest in P. notatus, reflecting its greater exposure to contaminated sediments. The interspecific differences observed indicate that habitat partitioning is a major factor regulating contaminant levels in these forage fish species. These interspecific differences in contaminant levels have important implications for fugacity models which would predict that these differences should not exist. Although chemical and physiological parameters may determine which contaminants have the potential to bioaccumulate, it is the regulation of exposure through ecological processes that will determine the degree to which that potential is realized.
Range Detection of Targets using Hydroacoustics in the Laboratory
Authors: Patrick P. H. , Sim B. , Hunt G.
Published: May 2008

Investigations were conducted in the laboratory on the accuracy in terms of range resolution of a commercial sonar system (420 kHz) in detecting underwater targets. Accurate range resolution of fish is necessary for reliable estimates of numbers and for detecting the presence and behaviour of fish near the bottom. Results indicated that the existing sounder was limited in target separation below 25 cm at a transmitted pulse of 0.1 ms under laboratory conditions. Modifications to equipment resulted in an improved range resolution (to approximately 10 cm) of targets in both vertical and horizontal tank experiments.
Comparing Polynomial and von Bertalanffy Growth Functions for Fitting Tag–Recapture Data
Authors: Hearn William S. , Leigh George M.
Published: May 2008

The properties of polynomial and von Bertalanffy growth functions are compared for analysing data from tag–recapture experiments in which fish are recaptured once. For the quadratic and von Bertalanffy growth functions, explicit formulae are obtained for the expected growth increment in terms of length-at-release, time-at-liberty, and the function parameters. If the least-squares fitting technique is used the von Bertalanffy function fits tag–recapture data with no more bias (probably less) than any other growth function, including polynomial growth functions. A bias-reduction technique for fitting the von Bertalanffy growth function to tag–recapture data is not applicable to other growth functions. We conclude that, apart from the straight line, the von Bertalanffy growth function is the one with the most desirable mathematical and statistical properties for fitting to tag–recapture data. The matter of the function that best characterises the way a specific fish species grows can be adequately addressed only by analyses of multiple measurements of individual fish.
Effects of Intermittent Chloramine-T Exposure on Growth, Serum Biochemistry, and Fin Condition of Juvenile Rainbow Trout (Oncorhynchus mykiss)
Authors: Powell Mark D. , Speare David J. , MacNair Neil
Published: May 2008

Chloramine-T is a commonly used therapeutic agent for the treatment of bacterial gill and skin diseases in the intensive aquaculture of salmonids; however, little is known about its effects on healthy fish. Juvenile rainbow trout (Oncorhynchus mykiss) were exposed weekly to 5, 10, and 20 mg active chloramine-T ingredient∙L−1 in a 20-tank replicate flow-through facility. Control fish were treated with tank water only. Growth parameters and haematocrits were taken twice weekly and serum biochemistry was measured on termination of the experiment. Absolute growth rates were suppressed but only statistically significantly in fish treated with 20 mg chloramine-T∙L−1 compared with controls. Fish exposed to 10 and 20 mg chloramine-T∙L−1 showed significant predisposition to an erosive dermatitis of the caudal fin which appeared to be caused by opportunistic pathogens of the genus Pseudomonas spp. and Flavobacter spp. Haematocrits decreased in controls and ail treatments. A significant concentration-dependent decrease in plasma sodium and chloride was observed. Plasma glucose levels did not vary and were similar to those reported for unstressed trout. We recommend that care be taken when using chloramine-T prophylactically and that concentrations of less than 10 mg∙L−1 be used.