bluuebunny/crossref_metadata_2025 huggingface dataset:
Paralytic Shellfish Poison in Sea Scallops (Placopecten magellanicus) in the West Atlantic
Authors: Jamieson G. S. , Chandler R. A.
Published: April 2011

Levels of Gonyaulax excavata toxin in sea scallop (Placopecten magellanicus) tissues were monitored in eastern Canada on a monthly basis between 1977 and 1981. All tissues but the adductor muscle were found to be highly toxic in Bay of Fundy scallops, with negligible toxicity observed in scallops from Georges Bank, the outer Scotian Shelf, and Northumberland Strait scallops. Level of Bay of Fundy toxicity was much higher than previously observed (maximum digestive gland toxicity: 150 000 μg/100 g in March 1978), and recent average monthly toxicity for Bay of Fundy scallop roe ranged from 184 to 286 μg/100 g. Considerable fluctuation in toxicity can occur between adjacent months, and peak toxicities in sea scallops occur during fail and winter months. Scallop roe fisheries should be permitted to be established for scallops fished from the northern part of Georges Bank and Northumberland Strait. However, a closed zone for scallop roe should be established in the Bay of Fundy and adjacent Scotian Shelf.Key words: scallop, PSP, Gonyaulax, Placopecten, mollusk
Early Growth and Quality of Chum Salmon (Oncorhynchus keta) Produced in Keeper Channels and Gravel Incubators
Authors: Bams R. A.
Published: April 2011

Chum larvae were incubated in two types of incubation system — a pilot Japanese-style hatchery (JSH) and a set of deep-gravel incubators (box) — at two levels of flow and two, or three, levels of egg density. Following voluntary emergence, fish were reared in tanks on an OMP diet and their growth rates compared. Initially, fry from both systems were of the same average size, but the JSH fish emerged 6 d earlier than the box fish and at a stage of development 6 d less advanced. At the end of 8 wk, all JSH groups were significantly longer than the box groups; the most extreme groups averaged 63.4 and 59.2 mm, respectively. Not only had the JSH fish kept their 6-d lead in additional growth, but they also grew significantly faster (calculated average rates were 3.553 and 3.217 mm/wk in the above groups). A previous assessment of fry quality had rated the JSH fry inferior to the box fry on the basis of four criteria (efficiency of yolk conversion, size and stage of development at emergence, and time of emergence). In this test, however, JSH fry rated superior in terms of final size and rate of growth achieved during 8 wk following emergence. Difficulties with simplistic quality criteria and how such criteria relate to fitness are discussed.
Effects of Changes in pH on Transparency and Thermal Regimes of Lohi Lake, near Sudbury, Ontario
Authors: Yan Norman D.
Published: April 2011

Changes in Secchi transparency (depth) and thermal regimes accompanying experimental neutralization and subsequent re-acidification of Lohi Lake, near Sudbury, Ontario are described. Secchi depth was not correlated with chlorophyll concentrations, phytoplankton biomass or total phosphorus, but it was negatively correlated with pH. Secchi depth was positively correlated with thermocline depth, epilimnetic thickness, and hypolimnetic heating rates suggesting that acidification should result in deeper mixing zones and warmer hypolimnia in lakes. Several possible implications of changes in transparency and thermal regimes produced by acidification are presented.
Supply, Distribution, and Transport of Suspended Sediment in a Macrotidal Environment: Bristol Channel, U.K.
Authors: Collins Michael
Published: April 2011

Various independent sets of data are used to investigate near-surface suspended sediment concentrations. The data include satellite (LANDSAT) imagery, field verification and near-synoptic surveys of specific areas and integrated, longer-term, surveys of the Channel. The information is used to identify areas of high turbidity, which relate to tidal and wave resuspension of the mobile sediments within the Estuary and Channel system. Thematic maps produced from the satellite imagery are comparable directly with the survey results and are combined with them, through a radiance/loge concentration relationship. Derived estimates of material present within the waters of the Channel range from 4.5 × 106 t to 13.4 × 106 t. Fluvial contributions are estimated to be of the order of 1.6 × 106 t/yr. Other evidence is available for the supply of material from the Celtic Sea. Isopleths of suspended sediment concentration are used to infer residual water and fine-grained sediment transport directions; these are compared with a more general model, which includes observed and predicted near-bed sand transport directions.Key words: Bristol Channel, Severn Estuary, suspended sediment, satellite imagery, sediment budget, sediment transport, residual water movement
Dynamics of Coastal Fluid Muds in Low-, Moderate-, and High-Tide-Range Environments
Authors: Wells John T.
Published: April 2011

Field studies of intertidal and subtidal fluid muds in low-, moderate-, and high-tide-range environments have revealed several similarities in process-response behavior despite the wide range in tidal energy. Using data from Louisiana (tide range 0.5 m), Surinam (tide range 2.0 m), and South Korea (tide range 5–9 m), examples are given for the unifying characteristics of (1) extreme wave attenuation, (2) high suspended-sediment concentration, and (3) rapid migration and "shifting" of soft muds. The loss of incoming wave energy results in natural protection to shorelines that are fronted by fluid muds. The opportunity thus exists to predict areas of future progradation and erosion from knowledge of fluid mud behavior. Fluid muds can be easily resuspended by small waves, and the high concentrations of suspended sediments in regions of mudshoals suggest that net transport rates can be enormous even under relatively weak currents. In addition to serving as temporary and transitory storehouses for littoral sediments, intertidal mudflats and subtidal mudshoals can become "welded" to the shoreline and colonized by vegetation in a single season.Key words: fluid mud, fine-grained sediments, wave attenuation
Vertical Mixing and its Effects on Phytoplankton Growth in a Turbid Estuary
Authors: Uncles R. J. , Joint I. R.
Published: April 2011

Using a hydrodynamical model, in conjunction with current meter observations, vertical eddy diffusivities, and associated vertical mixing time-scales are estimated for the Bristol Channel, U.K. In this shallow region, the mixing time-scale appears to be more useful than the commonly employed stratification parameter in assessing the potential for thermal stratification of the water column.Chlorophyll a concentrations in the Bristol Channel are observed to be vertically well-mixed throughout the year. This is shown to be a consequence of the short vertical mixing time-scales in comparison with phytoplankton generation times. These time-scales are of particular importance to phytoplankton in the region because the mixed depth is much greater than the depth of the euphotic zone. Photoinhibition is unlikely to occur in the rapidly mixing water column because phytoplankton cells experience high light conditions for only very short periods. In addition, the rapid mixing does not appear to allow time for photosynthetic adaptation of the phytoplankton population of the Bristol Channel.Key words: Bristol channel, phytoplankton growth, vertical mixing, vertical eddy viscosity
Tidal Current Speed and Production of Benthic Macrofauna in the Lower Bay of Fundy
Authors: Wildish D. J. , Peer D.
Published: April 2011

The benthic production of the lower Bay of Fundy, which has an area of 8620 km2, was estimated to be 166.7 × 104 t wet biomass in summer 1978, equivalent to an average benthic production of 193 g∙m−2∙yr−1. Over 88% of the production was by suspension feeders of which the horse mussel, Modiolus modiolus (Linnaeus, 1758), was by far the largest contributor.The geographic distribution of production of the major, soft-sediment, epi- and infaunal trophic groups in the lower Bay of Fundy was in general agreement with the hypothesis that tidal currents are a major determinant of benthic distribution and production in the lower Bay. Tidal currents control sediment dynamics, as well as settlement, growth, and feeding of benthic animals.Key words: benthos, benthic production, trophic groups, lower Bay of Fundy
Humic Acids Reduce Bioaccumulation of Some Polycyclic Aromatic Hydrocarbons
Authors: Leversee G. J. , Landrum P. F. , Giesy J. P. , Fannin T.
Published: April 2011

In laboratory studies, Daphnia magna were exposed for 6 h to five polycyclic aromatic hydrocarbons (PAH) (0.1–2.0 μg/L) in water with and without Aldrich® humics (2 mg DOC/L). Compared to results in nonhumic water, accumulation of PAH by Daphnia in water with humics was significantly reduced for benzo[a]pyrene (−25%) while it was increased for methylcholanthrene (+210%). Humics did not significantly alter Daphnia accumulation of anthracene, dibenzanthracene or dimethylbenzanthracene. In additional studies, humics reduced Daphnia accumulation of benzo[a]pyrene (B[a]P) over a range of B[a|P concentrations (1.1–5.4 μg/L) exceeding the reported limit for water solubility (1.1–1.2 μg/L). Humics consistently increased Daphnia accumulation of methylcholanthrene (MC) over a range of humic concentrations from 0.2 to 10.0 μg DOC/L. Particulates and DOC (10–12 mg TOC/L) occurring naturally in two South Carolina streams reduced Daphnia accumulation of B[a]P by 38–66%, with about 40% of the overall reduction attributable to DOC. We conclude that dissolved refractory organics may significantly affect bioavailability and environmental transport of some PAH in fresh waters.
Regulation of Zn2+ Uptake from the Gastrointestinal Tract of a Marine Teleost, the Winter Flounder (Pseudopleuronectes americanus)
Authors: Shears M. A. , Fletcher G. L.
Published: April 2011

The gastrointestinal uptake of Zn2+ was studied in winter flounder (Pseudopleuronectes americanus) using an in situ technique. The entire digestive tract was capable of absorbing Zn2+, with the uppermost portion of the intestine having the highest and the stomach the lowest capacity. A seasonal study revealed that the capacity of the digestive tract to absorb Zn2+ was greatest during the summer months. At least two steps appeared to be involved in the absorption process, the first a rapid accumulation of Zn2+ by the tissue, and the second a slower transfer into the body. The amount of Zn2+ absorbed increased with increasing loads of Zn2+ in the lumen; the transfer mechanism(s) was not saturated at the highest Zn2+ loads tested. Zn2+ uptake was inhibited in the presence of Cu2+, Cd2+, Co2+, Cr2+, Ni2+, Fe3+, Mn2+, and Hg2+. The capacity of the digestive tract to absorb Zn2+ was not affected by feeding the flounder a high-Zn2+ diet or by increasing body Zn2+ loads by intravenous injections. It is suggested that elimination mechanisms may play a greater role in maintaining Zn2+ homeostasis than controlling gastrointestinal uptake.
Projected Consequences of Dumping Sewage Sludge at a Deep Ocean Site near New York Bight
Authors: O'Connor Thomas P. , Okubo Akira , Champ Michael A. , Park P. Kilho
Published: April 2011

Projections are made of the distribution of and biological response to New York/New Jersey sewage sludges if they are slowly discharged from barges at a deepwater location in annual volumes of 7 × 106 m3. We have used available information on sludge composition, dispersion of barge-dumped wastes, flow through the dumpsite, sewage sludge settling under quiescent conditions, rates of horizontal dispersion in the deep sea, chemical composition of open ocean water, ambient mass fluxes to the seafloor, sediment characteristics, bioturbation rates, and biological responses to sludge and its components. Within a 20-m surface mixed layer between the dumpsite and the Gulf Stream a chemical signal of dumping may be evident in iron, lead, zinc, chromium, and PCB concentrations. Water column contamination would appear to be less than necessary to affect planktonic organisms or fish. Seafloor contamination would be due primarily to sludge particles falling at 10−2 cm∙s−1 or faster. Allowing for bioturbation, the major sediment contaminants, PCB s and PAHs, could reach concentrations at the sediment surface of 0.2 and 0.3 μg∙g−1, respectively, after 100 yr. Concentrations of that order in shallow ocean benthic systems are not obviously related to altered benthic life. The strength of these projections would be increased with better understanding in many areas, especially on the effect of natural and barge-induced turbulence on particle flocculation and on rates of horizontal dispersion in the deep ocean. If sludge is dumped, the water column should be studied for chemical evidence of sludge and response of open ocean plankton. Arrays of sediment traps could be deployed to quantify the rate and areal extent of the settling sludge flux.
Accumulation of Cadmium and Polychlorinated Biphenyls by Mytilus edulis Transplanted from Pristine Water into Pollution Gradients
Authors: Kock W. C. de
Published: April 2011

Monitoring of bioavailable Cd and polychlorinated biphenyls (PCB) is technically feasible by transplanting mussels, Mytilus edulis, from a population with low contaminant levels into polluted waters elsewhere. This procedure improves resolution power between sites of investigation by minimizing population variance at the start of exposure experiments. In the current investigation, random samples (100 animals each) of similar-sized individuals (length class 4.0–5.0 cm) derived from a sublittoral Atlantic stock (western Ireland) were simultaneously exposed to selected locations in Dutch estuarine and marine waters. Although approximately equal yearly amounts of Cd (~50 t) reach the sea by way of the Scheldt and the Rhine–Meuse systems, accumulated Cd levels in M. edulis in the eastern part of the western Scheldt Estuary were clearly elevated after 60 d of exposure, whereas levels in mussels under Rhine–Meuse influence were not greatly enhanced. The literature suggests that this is partly due to different geochemical processes. Cadmium accumulation in M. edulis is a slow process in the field, and plateau levels are not reached after 60 d. Polychlorinated biphenyls probably reach plateau values within 2–3 mo. The data show clear bioavailable PCB gradients as a result of fluvial input into Dutch coastal waters both by the Scheldt and the Rhine–Meuse systems. Contrary to data for Cd, a conservative estuarine mixing behavior is suggested. Also unlike data for Cd, winter levels in M. edulis were higher by a factor of 2 as compared with summer values, both on the basis of ash-free dry weights and total lipids. Offshore PCB concentrations in transplanted mussels remained low but after 60 d were elevated above initial Atlantic levels.
Use of a Bacterial Bioluminescence Assay to Assess Toxicity of Contaminated Marine Sediments
Authors: Schiewe Michael H. , Hawk Eric G. , Actor David I. , Krahn Margaret M.
Published: April 2011

A bacterial bioluminescence assay was evaluated for assessing the toxicity of contaminated marine sediments. Preliminary assays established the feasibility of testing methanol–dichloromethane sediment extracts and demonstrated the advantages of solvent-exchanging the extracts into ethanol before testing. Bioluminescence assays were then conducted on extracts of 18 marine sediments varying in nature and degree of chemical contamination. Statistical analyses revealed significant associations between acute toxicity expressed as a 15-min EC50 (the concentration of extract causing a 50% reduction in bioluminescence after a 15-min exposure) and concentrations of sums of measured aromatic hydrocarbons, naphthalenes, and chlorinated hydrocarbons. We conclude that the bioluminescence assay is useful as a rapid method of comparing and ranking the toxicity of organic extracts of contaminated sediments.
Aggregative Response of Common Mergansers (Mergus merganser): Predicting Flock Size and Abundance on Vancouver Island Salmon Streams
Authors: Wood C. C.
Published: April 2011

The abundance of common mergansers (Mergus merganser) was monitored on four salmon-producing streams on the east coast of Vancouver Island, B.C., during the spring and summer of 1980–83. Overall, merganser abundance declined steadily from March through June but increased following recruitment of juvenile birds. Mergansers congregated on streams where juvenile salmonid migrations were enhanced by hatcheries or spawning channels. Movement between streams was evident from inverse trends in abundance on three adjacent streams differing in juvenile salmonid production. At least 8 of 12 mergansers resighted after being marked and released on the Big Qualicum River visited other nearby streams. Flock-size distributions predicted by an equilibrium arrival–departure model were consistent with those observed during May–mid-june, but not those during late June. Social interactions and reduced flight activity appeared to influence dispersion to a greater extent during late June to August so that assumptions of the model were violated. A similar model was used to predict aggregation patterns on hatchery streams from observed relationships between fish availability and frequencies of arrival and departure. The aggregation model provides a parsimonious explanation of merganser aggregation patterns during March–June and is a potentially useful tool for designing fish release schedules to minimize predation by mergansers.
Adjuvant-Dependent Immunity and the Agglutinin Response of Fishes Against Aeromonas salmonicida, Cause of Furunculosis
Authors: Cipriano Rocco C. , Pyle Stephen W.
Published: April 2011

Adjuvant-dependent immunity resulted in agglutinin activity against Aeromonas salmonicida in sera of convalescent fishes. Rainbow trout (Salmo gairdneri), brown trout (Salmo salar), and brook trout (Salvelinus fontinalis) that had recovered from natural furunculosis produced serum agglutinin antibodies predominately against a specific chromatographic fraction (EcF1) of the bacterium's extracellular product. EcF1 was resolved by ion-exchange chromatography from DEAE SephadexA-25. When EcF1 was emulsified in Freund's incomplete adjuvant and injected intraperitoneally, brook trout were protected against experimental challenge; brook trout vaccinated with EcF1 only were not protected against furunculosis. EcF1, examined by immunodiffusion tests, SDS – polyacrylamide gel electrophoresis, and Western blot immunoassays, shared certain properties with bacterial endotoxin. EcF1 and endotoxin preparations both contained immunoreactive lipopolysaccharides which indicated that adjuvant-dependent immunity to A. salmonicida is related to endotoxin.
Distribution and Characteristics of Herring Spawning Grounds and Description of Spawning Behavior
Authors: Haegele C. W. , Schweigert J. F.
Published: April 2011

Pacific herring (Clupea harengus pallasi) are winter–spring spawners which exhibit a south to north latitudinal dine in spawning time. In the eastern Pacific, major spawning populations are concentrated near San Francisco, in Puget Sound, and along the coasts of British Columbia and southeastern Alaska. In the Bering Sea, herring spawn in Alaska and along the Kamchatka Peninsula. In the western Pacific, herring spawn in the Sea of Okhotsk and the Japan Sea. Atlantic herring (Clupea harengus harengus) consist of both winter–spring and summer–autumn spawning groups characterized in the northeast Atlantic by oceanic, shelf, and coastal populations. The oceanic group are large migratory fish spawning off the coasts of Norway and Iceland. The shelf group includes the various locally migratory North Sea populations adjacent to the British Isles. The coastal groups consist of smaller fish restricted to the Baltic and White seas. In the northwest Atlantic, spawning occurs from northern Labrador to Virginia with spring spawners predominating in the north and fall spawners in the south. Herring typically congregate near their spawning grounds for several weeks to months prior to spawning. Temperature is one of the factors that determine when spawning occurs. The Atlantic herring exhibits sexual dimorphism in the spawning act with only the female interacting with the spawning substrate. Both sexes of the Pacific herring make physical contact with the substrate on which the adhesive eggs are deposited. Spawning grounds are located in high-energy environments, either nearshore for spring spawners or in tidally active areas for fall spawners. Spawn is deposited on marine vegetation or on bottom substrate, such as gravel, which is free from silting. The eggs are tolerant to temperatures in the range of 5–14 °C and salinities in the range of 3–33‰. Egg mortality results mostly from suffocation due to high egg densities and silting, predation, and, in intertidal spawn, from stresses imposed by exposure to air and from egg loss by wave action.
Management of Pacific Herring (Clupea harengus pallasi) in the Eastern Pacific Ocean
Authors: Trumble Robert J. , Humphreys Robert D.
Published: April 2011

Pacific herring (Clupea harengus pallasi) fishery management in the eastern Pacific Ocean is under jurisdiction of the federal governments of the United States and Canada and the states of Alaska, Washington, Oregon, and California. In Canada, the Department of Fisheries and Oceans is responsible for all Canadian marine fisheries. United States fisheries management is a federal responsibility in waters beyond 5.6 km (3 nautical miles), provided that a Fishery Management Plan is in effect. As no such plan currently exists for herring in the eastern Pacific, individual states manage offshore waters as well as territorial waters. The dominant product from herring fishing on the west coasts of the United States and Canada is "sac-roe," or mature egg skeins, which are used as a caviar product. Other uses include human food, king crab and other commercial bait, bait for recreational fishermen, herring spawn-on-kelp, and animal food. In-season and post-season standing stock estimates are based on direct observation or measurement. Quotas are based directly on standing stock estimates, using one of two philosophies. The first, used mainly in Canada, sets a spawning escapement goal designed to maximize average larval production, and allows harvest of all herring in excess of this goal. The second sets a harvest in proportion to the standing stock, to allow spawning escapement to fluctuate cyclically as in an unfished population. Serious management problems are caused by the large catching capacity of the herring fleets and by the short time period during which satisfactory roe maturity occurs before spawning. Fishing is often limited to several hours or several days, primarily to maintain catches within quota limits, and secondarily to prevent overloading processing facilities. An equitable allocation of the harvest among various users is difficult, compounding management problems.
Lakeward Migrations by Juvenile Atlantic Salmon, Salmo salar
Authors: Hutchings Jeffrey A.
Published: April 2011

Atlantic salmon parr, Salmo salar, undertook lakeward migrations from outlet streams in the Wings Brook system, eastern Newfoundland. Lakeward movement occurred from May through November, intensifying over a 6- to 8-wk period during spring. Parr remained in the lakes where they either matured (usually males) or smoltified (predominantly females) before returning to the streams. Mature parr emigrated from the lakes during autumn whereas smolts entered the streams during spring. Lakes provided conditions for increased parr growth and survival to the smolt stage relative to the riverine environment, and appeared to represent important overwintering habitat. Smolt production occurred almost entirely within the lakes. Parr movement into lakes could not be explained by physical environmental factors. Lakeward migrations appear to have an adaptive basis and can be explained as an evolutionarily stable reproductive tactic.
Independent Distributions of Fish Larvae and Their Prey: Natural Paradox or Sampling Artifact?
Authors: Frank Kenneth T.
Published: April 2011

Several recent studies have concluded that larval fish distributions are independent of the abundance and distribution of their prey. All of these studies used coarse-mesh (> 250 μm) nets, incapable of retaining the edible zooplankton for fish larvae, to provide quantitative estimates of the larval food resource. The assumption that zooplankton captured by coarse-mesh nets provided a reliable index of the edible zooplankton for fish larvae was tested and unsupported by the analysis of several independent data sets. In the waters off southwestern Nova Scotia the biomass of edible zooplankton for young larval fish was highly concentrated in the nearshore region, progressively lower levels were evident offshore on the shelf, and the mesoscale distributional pattern did not accurately reflect the total zooplankton biomass retained by a 333-μm-mesh net. Independent spatial distributions of discrete size groups of zooplankton are characteristics similar to zooplankton distributions reported for other geographic regions. A more logical explanation for the reports of "paradoxical" distributions of fish larvae and their prey is to be found in the inefficiency and bias in the sampling methods used to evaluate the larval food resource. Failure to properly evaluate the larval food resource has led to inappropriate testing of some longstanding hypotheses in fisheries biology.
Effects of Constant Day Length on Sexual Maturation and Growth of Atlantic Salmon (Salmo salar) Parr
Authors: Saunders R. L. , Henderson E. B.
Published: April 2011

Atlantic salmon (Salmo salar) were reared for 6 mo from first feeding under four photoperiod regimes: LD 12:12, LD 16:8, LD 24:0, and simulated natural (LDN). Water temperature followed seasonal changes but was adjusted so as not to exceed 16 °C in summer or to fall below 6 °C in winter. Growth rates were highest in the LD 24:0 group during the first 3 mo; subsequently, the LD 16:8 fish grew faster than all others. Length–frequency distributions were skewed towards smaller sized fish in January. Sexually mature males were mainly in the lower halves of the length–frequency distributions; females and immature males were distributed throughout. The incidence of mature males was highest in the LDN group (67% of males) but reached high levels (44–58%) in the other groups.
Evidence of Selection for Vertebral Number of Fry in PeamouthMylocheilus caurinus
Authors: Swain D. P.
Published: April 2011

Laboratory-reared peamouth fry (Mylocheilus caurinus) were exposed to predation by pumpkinseed (Lepomis gibbosus) or smallmouth bass (Micropterus dolomieui) both before and after vertebrae were developed (i.e. countable) in fry. Vertebral counts of survivors were compared with those of unexposed controls (after further laboratory rearing when experiments were conducted before vertebrae were countable). Predation was selective for vertebral number only in experiments at the larger sizes when vertebrae were well developed in fry. Selection for vertebral number did not vary between temperature (15 or 25 °C) nor between cover (presence or absence) treatments and was not attributable to selection for prey length. Vertebral counts of wild fry were monitored in Holden Lake, British Columbia, between May 14 and July 1, 1984. Differences in vertebral number between age or length classes of fry in the lake that were not attributable to variation in the vertebral counts of fry entering the lake indicated selection for vertebral number of fry over a narrow range of lengths (9.3–10.6 mm). Selection favoured a low number (44) at small lengths and a high number (45) at greater lengths in this range.
Recent Changes in the Phytoplankton of the Bay of Quinte, Lake Ontario: the Relative Importance of Fish, Nutrients, and Other Factors
Authors: Nicholls K. H. , Hurley D. A.
Published: April 2011

A 50% reduction in phosphorus loading to the upper Bay of Quinte (Lake Ontario) from municipal sources in 1977 was followed by a major decline in phytoplankton biomass in 1978. However, by 1984–85, biomasses again approached those of the pre-phosphorus control period, despite continued low phosphorus loadings. No major shifts in phytoplankton composition occurred; domination by the diatoms Melosira and Stephanodiscus spp. and the blue-green algae Anabaena and Aphanizomenon spp. has continued. Highly significant positive correlation coefficients (r = 0.92–0.98) were found for phytoplankton — fish relationships during both the pre- and postphosphorus removal periods which coincided with pre- and postdie-off periods of white perch (Morone americana) and alewife (Alosa pseudoharengus). For the entire 16-yr period of data collection, a multiple regression model fitting upper bay phytoplankton biomass (with an adjusted R2 of 0.83) was developed with five input variables. White perch biomass alone explained more than 50% of the variance in the model. It is hypothesized that trophic interactions among other biotic components in the Bay of Quinte may be very important in controlling phytoplankton biomass.
Changes in the Body Composition with Age of Goldeye, Hiodon alosoides
Authors: Craig J. F. , Smiley K. , Babaluk J. A.
Published: April 2011

Male goldeye, Hiodon alosoides, grew faster, matured earlier, and had a shorter lifespan than females as did exploited compared with unexploited populations. Instantaneous growth rates of the body organs and tissues were usually higher in the male than in the female. The proportion of fat to the total constituents in the muscle, liver, gut, and carcase of female and the gut and carcase of male goldeye declined with age while that in the ovary increased. The proportion of protein in the body tissues and organs of both sexes remained approximately constant with age. Ash content increased in the carcase of older females and males. Glycogen concentration in the liver varied extensively and was considered as indicator of stress and unrelated to aging processes. Between the ages of 10 and 16 yr the energy content of the female soma increased by 44% whereas the energy content of the ovary increased by 121%. The ovary selected essential fatty acids at the expense of the soma.
Sea Growth and Time of Migration of Anadromous Arctic Char (Salvelinus alpinus) from the Vardnes River, in Northern Norway
Authors: Berg Ole Kristian , Berg Magnus
Published: April 2011

The annual seaward migration of Arctic char (Salvelinus alpinus) from the Vardnes River, northern Norway usually takes place early in summer, between the end of May and the beginning of June. A period of very fast growth was recorded immediately following the entry of char into the sea. Mean daily growth rates of both small and large char decreased with increasing length of time spent at sea, particularly after the end of June. Almost no further increase in length took place in the sea after the beginning of July. Sea temperature was low during this early growth period, rising to above 10 °C during the period when sea char growth declined. Char appeared to be especially well adapted to low temperatures, since their growth rate during this early period was from two to four times faster than that recorded for sympatric sea trout (Salmo trutta). The results support the hypothesis that sea temperature may be one of the factors that control the southern distribution of anadromous Arctic char.
Identification of Spring- and Autumn-Spawning Herring (Clupea harengus harengus) using Maturity Stages Assigned from a Gonadosomatic Index Model
Authors: McQuinn Ian H.
Published: April 2011

A model is developed to identify the spawning type of individual herring (Clupea harengus harengus) from the sympatric spring and autumn spawning stocks in the southern Gulf of St. Lawrence (NAFO Division 4T). The maturity stage is assigned from a gonadosomatic index model using discriminant analysis and the spawning type is determined from the maturity stage and the month of capture according to a detailed description of the annual maturity cycle of each type. The model is shown to be objective, quantitative, and precise. Greater than 97% overall agreement was achieved between the spawning type classification of individuals by histological means and by the model, significantly improving the identification accuracy compared with a macroscopic maturity stage key. The model also has the advantages of (1) identifying the spawning type directly by determining the "season of spawning" rather than the "season spawned" as is inferred from indirect evidence such as otolith characteristics or meristic data, (2) requiring easily obtained, quantifiable data, and (3) enabling the rapid treatment of a large number of specimens.
Nitrogen Fixation by Epilithic Periphyton in Small Arctic Lakes in Response to Experimental Nitrogen and Phosphorus Fertilization
Authors: Bergmann Martin A. , Welch Harold E.
Published: April 2011

Epilithic periphyton played a moderate role in the nitrogen budget of four small arctic lakes located at Saqvaqjuac, N.W.T. The acetylene reduction technique used to estimate nitrogen fixation indicated that periphyton in 0–2 m water depth were capable of fixing up to 0.86 mg N∙m−2∙h−1 during the period of active nitrogen fixation from July to September 1981. Far Lake was fertilized with Phosphorus for 3 yr and had a higher rate of fixation than did a P- and N-fertilized lake or a control lake, in agreement with similar studies on temperate and subarctic lakes. A numerical model based on incoming light was used to perdict the amount of nitrogen fixed in each study lake throughout the season. The calculated contribution of periphyton to the overall N budget for 1981 was 5% for the P- and N-fertilized lake, 16% for the control lake and 28% for the P-only fertilized lake.
Chromosomal and Mitochondrial DNA Characterization of a Population of Dwarf Cisco (Coregonus artedii) in Minnesota
Authors: Shields Barbara A. , Guise Kevin S. , Underhill James C.
Published: April 2011

This study compared the chromosome complement and mitochondrial DNA profile of a population of dwarf cisco in Ten Mile Lake, Cass County, Minnesota, to two populations of normal-sized Coregonus artedii in order to determine if the dwarf fish were conspecific with C. artedii. Chromosomal analysis revealed a diploid chromosome number (2n = 80) the same as reported for C. artedii. Mitochondrial DNA (mtDNA) analysis revealed unexpected levels of intrapopulational diversity in each study population, with the dwarf fish displaying the highest level of mtDNA diversity. Heteroplasmy, restriction site polymorphisms, and three size variants were documented. Each population was characterized by a unique profile of mtDNA clonal types, yet interpopulational comparisons revealed more similarities between the dwarf fish in Ten Mile Lake and the two normal populations than between the populations of normal-sized fish. Based on these data, the dwarf fish of Ten Mile Lake should be considered conspecific with Coregonus artedii.
Aluminum and Acid Toxicity to Two Strains of Brook Trout (Salvelinus fontinalis)
Authors: Ingersoll C G. , Gulley D. D. , Mount D. R. , Mueller M. E. , Fernandez J. D. , Hockett J. R. , Bergman H. L.
Published: April 2011

Two strains of 1 yr-old brook trout were exposed to 14 combinations of pH, aluminum, and calcium during a 28-d experiment. Survival, weight, and gill histology of both strains were affected similarly by pH, aluminum, and calcium exposure. Survival was reduced at inorganic monomeric aluminum concentrations (IA1) of 29 μg/L at pH 5.2 and [Formula: see text] at pH 4.4 and 4.8. Fish weight was reduced with exposure to pH below 4.8 or aluminum concentrations [Formula: see text]. The gills sampled from fish exposed to low pH exhibited lifting of the outer epithelium and hypertrophy (increase in size) of chloride and epithelial cells. The response of gills sampled from fish exposed to low pH and elevated aluminum was more pronounced relative to the low pH exposure alone. In addition to the effects observed in the low pH exposed fish, the gills from fish exposed to both acid and aluminum exhibited vacuolation and degeneration of epithelial and chloride cells and the presence of dense cells. Finally, fish confined in PVC tubes designed to mimic in situ field exposure procedures were more sensitive to the toxic effects of acid and aluminum compared to free-swimming fish. Caution must be taken when extrapolating safe field levels from in situ exposures of caged fish.
A Hydroacoustic Study of the Pelagic Spawning Behavior of Whitefish (Coregonus lavaretus) in Lake Constance
Authors: Eckmann Reiner
Published: April 2011

The horizontal and vertical distribution patterns of pelagic spawning whitefish (Coregonus lavaretus) were studied by echosounding from the end of the growing season (early November) until after spawning (late January). During early November, whitefish inhabited similar depths during day and night, but during spawning displayed vertical migrations of up to 50 m amplitude: whitefish ascended at dusk and descended at dawn. At the end of the spawning season, vertical migrations ceased. Juveniles took part in the daily migrations, but only sexually mature specimens invaded the uppermost 10 m of water, while maturing and juvenile individuals and spent females stayed deeper during the night. This vertical distribution pattern is interpreted as a means to increase encounter probability among mature specimens. Diel vertical migration of the entire population is suggested to be an aid to avoid cannibalism on freshly spawned eggs during settling to the lake bottom. Total fish density estimates increased during upward migration and decreased during downward migration; this may be the result of differences in target strength caused by both reduced swimbladder volume and positive tilt while in deep waters. Highly reproducible abundance estimates were obtained during night when whitefish were evenly distributed at the top of their vertical range.
Hypolimnetic O2Consumption, Denitrification, and Methanogenesis in a Thermally Stratified Lake
Authors: Bédard Charles , Knowles Roger
Published: April 2011

Hypolimnetic O2consumption, methanogenesis, and denitrification were estimated from concentration changes in O2, CH4, and nitrogen oxides (NO3−, NO2−, N2O), respectively, in the eastern basin of Lake St. George, Ontario, during thermal stratification from 1980 to 1984. NH4+accumulated in the hypolimnion throughout the period of stratification and provided an overall measure of organic matter mineralization. Anaerobic metabolism, particularly methanogenesis, predominated because anoxia was total within less than 2 mo of spring water column turnover and nitrogen oxides were always completely depleted before fall turnover. The time of onset and rate of NO3−, depletion varied considerably between years and were not always directly correlated with O2concentration. It was estimated that, on average, O2consumption, denitrification, and methanogenesïs accounted for approximately 80% of hypolimnetic organic C mineralization in the periods surveyed.
Mating and Multiple Clutches in Australian Boeckella and Calamoecia (Copepoda: Calanoida)
Authors: Maly Edward J.
Published: April 2011

Experiments were performed with Australian centropagid calanoid copepods of Boeckella and Calamoecia to test the hypotheses that species in these genera are capable of producing multiple clutches with one insemination and that successful mating occurs at all stages of the female's ovigerous cycle. The second hypothesis was also tested by an examination of natural populations; spermatophore placement on gravid and nongravid females was scored. Both hypotheses were confirmed. Egg development times and patterns of resting egg hatching were examined under laboratory conditions for up to 100 d. These characteristics and patterns of egg development and resting egg production may result from selection for highly variable and unpredictable environments that existed in Australia before human intervention.
Bias Associated with Using the Eggers Model for Estimating Fish Daily Ration
Authors: Hayward Robert S.
Published: April 2011

Estimates of yellow perch (Perca flavescens) daily ration derived from Eggers' model were compared with those based on the Elliott–Persson model and a 3-h within-day sampling interval. Correcting for the bias in Eggers estimates associated with food weight differences at the start and finish of estimation periods significantly reduced discrepancies between the two when Eggers estimates were also based on a 3-h sampling interval. As sampling interval was increased to 6 and 12 h for Eggers estimates, a positive bias related to variability about [Formula: see text] emerged and inflated exponentially with increasing ration levels. A third bias (typically positive) may be introduced when [Formula: see text] in Eggers' model is computed without regard to the skewness that often exits in distribution of food weights among fishes within a single collection. Use of the median or a normalizing transformation will avert this. While each bias alone can have an important effect on daily ration estimates, the possibility of accentuated bias from multiple sources also exists. Two of the potential biases are easily managed, but caution is advised when Eggers' approach is used to estimate daily rations based on expanded sampling intervals.
Importance of Latitude and Organic Color on Phytoplankton Primary Productivity in Florida Lakes
Authors: Beaver John R. , Crisman Thomas L.
Published: April 2011

A characterization of primary productivity patterns in subtropical Florida lakes along increasing gradients of both dissolved organic color and phytoplankton biomass is presented. Volumetric expression of gross primary productivity was more strongly correlated with chlorophyll a and nutrient concentrations than was areal expression. Primary production in clearwater (<75 Pt units) lakes was more predictable than colored (>75 Pt units) lakes. Areal production in Florida lakes was intermediate to the tropical and temperate regions, although volumetric productivity during the vegetative season (May–September) was not significantly different from temperate zone lakes for the same period. Predictive abilities of empirical equations describing primary productivity in Florida lakes are improved by distinguishing colored and clear lakes.
Impacts of Fish Introductions in Tropical Asia and America
Authors: Fernando C. H.
Published: April 2011

Biotas are constantly being reshaped by invasions. Introduction is now an added route to invaders. Impacts must be viewed against the background of massive changes in type, extent and quality of freshwater habits globally and in that freshwater fishes are almost living fossils. Also, old lakes and lacustrine fishes are highly restricted geographically. Lakes are young while rivers are old. Riverine, marsh and pond fishes are not well adapted to lacustrine conditions now widespread due to reservoir construction. Some Clupeidae and Cichlidae are lacustrine-adapted and highly productive. They have therefore made major impacts on fish yields in lakes and reservoirs. In tropical Asia and America, there have been a series of overlapping waves offish introductions during the past 150 years, culminating tin the tilapias from Africa. These fishes now dominate capture and culture fisheries in many countries. Fish introductions are a fait accompli and will continue. They must be realistically assessed and carefully monitored. Contrary to some predictions, introductions have not caused severe damage to indigenous species except when piscivores were used. Yields of indigenous fishes have apparently been enhanced in some instances. Parasites pose a serious threat and only an effective quarantine will ensure their exclusion.
Mitochondrial DNA Diversity in Fishes and its Implications for Introductions
Authors: Billington Neil , Hebert Paul D. N.
Published: April 2011

Patterns of mitochondrial DNA (mtDNA) variation have now been examined in more than 40 fish species. This work has established that mitochondrial genomes of fish show constrained size variation, but that genomes of closely related species often vary in size, suggesting that counterbalancing deletions and insertions act to stabilize genome size. Gene order and composition are also stable, but nucleotide sequences show rapid divergence. Populations of most fish species contain a few common mtDNA haplotypes and a spectrum of their rare mutational derivatives. The extent of genetic divergence among dominant haplotypes seems linked to environmental conditions with greater divergence in freshwater than marine species, especially those occupying unglaciated localities. Haplotype frequencies ordinarily show considerable local divergence, largely as a result of stochastic shifts associated with population founding events. Such divergence provides a basis for both the discrimination of local stocks and for the recognition of major genetic discontinuities reflecting past episodes of gene pool fragmentation. Analysis of hatchery stocks has often revealed their mtDNA divergence, but in most cases stocks are fixed for haplotypes which are also common in wild populations. There is, however, the opportunity to develop brood-stocks marked with rare haplotypes, permitting their recognition in nature over many generations.
Genetic interactions Between Hatchery and Wild Salmonids: Lessons from the Pacific Northwest
Authors: Waples Robin S.
Published: April 2011

The potential for genetic interactions between hatchery and wild populations of salmonids in northwestern North America has increased considerably in recent decades. Efforts to mitigate severe losses to many wild stocks caused by overfishing, destruction of habitat, and blockage of migratory routes have focussed on boosting artificial production in public hatcheries. Opportunities for genetic interactions between hatchery and wild fish will increase if efforts to supplement wild production with hatchery-reared fish continue. Concerns center on three issues: (1) direct genetic effects (caused by hybridization and introgression); (2) indirect genetic effects (principally due to altered selection regimes or reductions in population size caused by competition, predation, disease, or other factors); and (3) genetic changes to hatchery stocks (through selection, drift, or stock transfers), which magnify the consequences of hybridization with wild fish. Strategies for minimizing these genetic risks and monitoring the consequences of various management options are discussed, and some important areas for future research are identified.
Loss of Exploited, Indigenous Populations of Lake Trout,Salvelinus namaycush, by Stocking of Non-Native Stocks
Authors: Evans David O. , Willox Campbell C.
Published: April 2011

A deterministic, age-structured population model was developed to explore the combined effects of exploitation and stocking of hatchery-reared lake trout on native lake trout populations. Stocking of non-native lake trout at moderate to high exploitation rates caused loss of the recipient population, even when the stocked fish did not reproduce or interbreed with the native fish. If hatchery fish reproduce, their progeny mask the loss of the wild stock. At exploitation and stocking rates typical of lake trout populations in Ontario, the wild stock was replaced by the hatchery stock in a few generations. Native stocks having weak recruitment are least resistant to displacement by hatchery stocks and are also the most likely to be subjected to stocking. Evidence from several field studies in Ontario generally provided support for our stock displacement hypothesis and modelling results. Extensive stocking of a few domesticated hatchery stocks has the potential to reduce genetic heterogeneity through loss of locally adapted stocks of lake trout. We suggest that emphasis should be placed on protecting the genetic integrity of the remaining self-sustaining wild stocks, and that a moratorium be considered on supplementation stocking of these populations, especially with non-native hatchery-reared stocks.