bluuebunny/crossref_metadata_2025 huggingface dataset:
Age and growth of the Pacific grenadier (Coryphaenoides acrolepis) with age estimate validation using an improved radiometric ageing technique
Authors: Andrews Allen H , Cailliet Gregor M , Coale Kenneth H
Published: April 2011

Current and historic longevity estimates for the Pacific grenadier (Coryphaenoides acrolepis) range from 6 to greater than 60 years. Age estimates in this study using growth increment counts in thin otolith sections indicate the Pacific grenadier is a long-lived fish. To validate this growth information, age was determined using the radioactive disequilibria of 210Pb and 226Ra in otolith cores from adult Pacific grenadier. Radiometric ages closely agreed with age estimates from counting growth increments, which confirms their annual periodicity. Radiometric results indicate the Pacific grenadier can live at least 55.8 years (-7.4, +10.1 years). Growth increment counts from large fish indicate longevity may approach 73 years. Because the Pacific grenadier is long-lived and matures late in life, it may be vulnerable to heavy fishing pressure. Therefore, conservation measures need to be taken to sustain this rapidly developing fishery.
The rich krill aggregation of the Saguenay - St. Lawrence Marine Park: hydroacoustic and geostatistical biomass estimates, structure, variability, and significance for whales
Authors: Simard Yvan , Lavoie Diane
Published: April 2011

The euphausiid aggregation at the head of the main channel of the estuary and Gulf of St. Lawrence was surveyed using 120- and 38-kHz hydroacoustics in the summers of 1994 and 1995. A systematic sampling grid covering an area of 1319 km2 was visited eight times. Fish echoes were separated from krill echoes using the difference in backscattering strength at the two frequencies. Global estimates were obtained from geostatistical methods for both total biomass and the fraction exceeding 5 g wet·m-3. The euphausiids were always exclusively composed of individuals of the oldest cohorts (2+) of the two species Thysanoessa raschi and Meganyctiphanes norvegica. Total biomass varied from 8 ± 2 to 96 ± 8 kt and cutoff biomass from 0 to 56 ± 6 kt. The two types of estimates were linearly related. Biomass was autocorrelated up to distances of 10-15 km. An anisotropic structure with radii of ~2 × 5 km, stretched along the channel axis, was discernible at a small scale. The particular size distribution of euphausiids and the large variations in the global estimates appear to be controlled by horizontal transport. The study area appears to be the richest krill aggregation site yet documented in the northwest Atlantic, with densities similar to the rich krill aggregation areas of the Antarctic. The krill aggregation is at the heart of this traditional whale feeding ground.
Predation risk breaks size-dependent dominance in juvenile coho salmon (Oncorhynchus kisutch) and provides growth opportunities for risk-prone individuals
Authors: Reinhardt Ulrich G
Published: April 2011

Groups of coho salmon (Oncorhynchus kisutch) fry in stream tanks formed size-determined dominance hierarchies, which were upheld through aggressive interactions and led to smaller fish occupying inferior feeding positions. Under simulated predation risk, the frequency of agonistic interactions was reduced, but more intensive aggressive behaviours were performed. This allowed small fish to gain access to better feeding positions. The effect of the predation threat on coho behaviour seemed to extend across a riffle into a second pool that served as a refuge. Smaller fry that chose to be in the exposed pool had greater growth rates than those that mainly occupied the refuge, while large fry that exposed themselves to predation did not grow better than their risk-avoiding counterparts. Differences in risk taking and growth among small coho fry in this experiment may support reports for Atlantic salmon (Salmo salar) of a split into different life history trajectories. The observations suggest that the presence of predators creates opportunities for the expression of alternative behavioural strategies that are absent under size-dependent dominance hierarchies.
Modeling data from double-tagging experiments to estimate heterogeneous rates of tag shedding in lake trout (Salvelinus namaycush)
Authors: Fabrizio Mary C , Nichols James D , Hines James E , Swanson Bruce L , Schram Stephen T
Published: April 2011

Data from mark-recapture studies are used to estimate population rates such as exploitation, survival, and growth. Many of these applications assume negligible tag loss, so tag shedding can be a significant problem. Various tag shedding models have been developed for use with data from double-tagging experiments, including models to estimate constant instantaneous rates, time-dependent rates, and type I and II shedding rates. In this study, we used conditional (on recaptures) multinomial models implemented using the program SURVIV (G.C. White. 1983. J. Wildl. Manage. 47: 716-728) to estimate tag shedding rates of lake trout (Salvelinus namaycush) and explore various potential sources of variation in these rates. We applied the models to data from several long-term double-tagging experiments with Lake Superior lake trout and estimated shedding rates for anchor tags in hatchery-reared and wild fish and for various tag types applied in these experiments. Estimates of annual tag retention rates for lake trout were fairly high (80-90%), but we found evidence (among wild fish only) that retention rates may be significantly lower in the first year due to type I losses. Annual retention rates for some tag types varied between male and female fish, but there was no consistent pattern across years. Our estimates of annual tag retention rates will be used in future studies of survival rates for these fish.
Effects of light, prey size, and turbidity on reaction distances of lake trout (Salvelinus namaycush) to salmonid prey
Authors: Vogel Jason L , Beauchamp David A
Published: April 2011

Most studies on visual foraging by fish have focused on reaction distances to invertebrate prey; however, these acuity-based results considerably overestimate reaction distances of piscivores to prey fish. In laboratory experiments, we quantified reaction distance of adult lake trout (Salvelinus namaycush) to rainbow trout (Oncorhynchus mykiss) and cutthroat trout (Oncorhynchus clarki) as a function of light (0.17-261 lx), prey size (55, 75, and 139 mm), and turbidity (0.09, 3.18, and 7.40 NTU). Reaction distances increased rapidly with increasing light from <25 cm at 0.17 lx to about 100 cm at a light threshold of 17.8 lx. Reaction distance declined as a decaying power function of turbidity. By constructing equations that describe the combined effects of light and turbidity on reaction distances, we can begin to model prey detection capabilities of piscivores at any depth at any time of day in natural environments.
Nocturnal habitat use of Atlantic salmon parr in winter
Authors: Whalen Kevin G , Parrish Donna L
Published: April 2011

We completed 22 night snorkeling surveys between November and March 1995-1997 to quantify Atlantic salmon (Salmo salar) parr habitat use relative to habitat availability in the Rock River, Vermont, U.S.A. On average, post-young-of-the-year (PYOY) parr selected greater water depths in winter than young-of-the-year (YOY) parr, whereas YOY and PYOY parr both selected water velocities ([Formula: see text]19 cm/s) that were significantly lower than random measurements (46 cm/s). Maturity of PYOY parr had no significant influence on habitat selection. The majority of YOY and PYOY parr at night were found in contact with the stream bottom resting on silt-sand or gravel substrates in velocity dead-zone habitats created by the stream edge or depositional habitats created by midstream rocks and boulders. The strong selection that nocturnal Atlantic salmon parr exhibit for low water velocity areas in winter indicates the importance of maintaining large instream cover that provides refuges from high flows. The similarity that YOY and PYOY parr exhibited in many elements of habitat selection suggests that both stages may be similarly susceptible to habitat limitations in winter.
Effects of an erroneous natural mortality rate on a simple age-structured stock assessment
Authors: Clark William G
Published: April 2011

The abundance of many stocks is estimated by fitting an age-structured model to catch-at-age and relative abundance data from the commercial fishery and scientific surveys. The natural mortality rate used in the model is usually estimated externally and its value is uncertain. An erroneous natural mortality rate will bias the stock size estimates obtained by fitting the model and will also bias the yield calculations that are done to choose a harvest rate and recommend quotas. This paper describes the general features of both effects by analyzing a simple age-structured model fitted to artificial data. It is shown that an erroneous natural mortality rate mainly affects the estimates of fishing mortality and hence abundance but not the estimates of age-specific selectivity. Errors in estimated abundance and target harvest rate are always in the same direction, with the result that, in the short term, extremely high exploitation rates can be recommended (unintentionally) in cases where the natural mortality rate is overestimated and historical exploitation rates in the catch-at-age data are low. A conservative (low) estimate of natural mortality can avoid that danger. Long-term yield under either an FMSY or F35% strategy is not very sensitive to error in natural mortality rate unless it is grossly underestimated.
Influence of salmon spawner densities on stream productivity in Southeast Alaska
Authors: Wipfli Mark S , Hudson John P , Chaloner Dominic T , Caouette John P
Published: April 2011

We conducted this study to determine the relationship between salmon spawner abundance and stream biofilm and benthic macroinvertebrate abundance in Southeast Alaska. Experiments took place in outdoor artificial and natural streams. Six pink salmon (Oncorhynchus gorbuscha) carcass treatments (0.00, 1.45, 2.90, 4.35, 5.80, and 7.25 kg wet mass) placed in artificial channels were subsampled repeatedly for biofilm ash-free dry mass (AFDM), chlorophyll a, and macroinvertebrates. In a small (nonanadromous) forest stream, we sampled benthos throughout a 66-m reach 17 days after distributing 60 carcasses along the lower half of that reach. All response variables significantly increased in response to carcass additions in both artificial and natural streams. Chlorophyll a continued to increase across all loading rates, while AFDM and total macroinvertebrate densities showed no further response to loading beyond the first treatment (1.45 kg) in artificial streams. In the natural stream, AFDM and chironomid densities continued increasing across loading levels. These results indicated that increased spawner densities increased lower trophic level abundance until a trophic capacity was reached. Salmon escapement goals should consider food web effects, especially on trophic levels that support juvenile salmonids, that ultimately affect freshwater salmon production.
Selection of an organic acid analogue of dissolved organic matter for use in toxicity testing
Authors: MacRae Russell K , Maest Ann S , Meyer Joseph S
Published: April 2011

Uncontaminated stream waters in the vicinity of a Co mine in Idaho were titrated with Cu to determine the Cu-binding characteristics of natural dissolved organic matter (DOM) and suspended particles. Nonlinear regressions of bound versus free Cu concentrations were consistent with a two-ligand model for DOM complexation of Cu, in which the conditional stability constants (log K) and complexation capacities (CC) were log K1 = 7.26, CC1 = 0.21 µmol Cu·mg dissolved organic carbon (DOC)-1 and log K2 = 5.13, CC2 = 2.89 µmol Cu·mg DOC-1. Copper-binding constants were similar in filtered (0.45 µm) and unfiltered water samples. Calcium, Mg, and Co did not compete appreciably with Cu for DOM complexation at concentrations present in site waters. Copper binding to amorphous iron oxide flocs also was not important at the Fe concentrations present in the stream waters. We selected a mixture of three organic acids, dipicolinic, oxalic, and malonic, to mimic the Cu-binding properties of this DOM. Geochemical models were developed to estimate Cu speciation and evaluate its bioavailability in companion fish toxicity tests using the DOM analogue (Marr et al. 1999. Can. J. Fish. Aquat. Sci. 56: 1471-1483).
Dimethylsulfoxide (DMSO) and related sulfur compounds in the Saguenay Fjord, Quebec
Authors: Lee P A , Haase R , de Mora S J , Chanut J -P , Gosselin M
Published: April 2011

The biogeochemical cycling of dimethylated sulfur compounds was investigated in the Saguenay Fjord during June 1996, just prior to the flooding in the catchment area. Dimethylated sulfur compounds, namely dimethylsulfide (DMS), dimethylsulfoniopropionate (DMSP), and dimethylsulfoxide (DMSO), were determined at six sites. In comparison with other coastal environments, including the Gulf of St. Lawrence, DMS (0-1.8 nmol·L-1, average <0.2 nmol·L-1) and DMSP (0-23 nmol·L-1, average <0.8 nmol·L-1) concentrations were relatively low because the brackish waters were poor in algal abundance and dominated by species not noted as major DMS and DMSP producers. Similarly, dissolved DMSO levels (<0.016 nmol·L-1) were low due to the limited availability of its DMS precursor and the shallow photic zone. Particulate DMSO was measured (0-110 nmol·L-1, average ~8 nmol·L-1) and occasionally exceeded particulate DMSP concentrations (0.016-140 nmol·L-1, average ~3.5 nmol·L-1). Given the low dissolved DMSO concentrations, the presence of particulate DMSO provides evidence for its direct biosynthesis by phytoplankton.
A biophysical model of the interaction between vertical migration of crustacean zooplankton and circulation in the Lower St. Lawrence Estuary
Authors: Zakardjian Bruno A , Runge Jeffrey A , Plourde Stephane , Gratton Yves
Published: April 2011

As an essential step in modeling the influence of circulation on the population dynamics of marine planktonic copepods, we define a simple formulation of swimming behavior that can be used in both Eulerian and Lagrangian models. This formulation forces aggregation of the population toward a preferential depth and can be stage specific and time varying, thus allowing description of either diurnal or seasonal vertical migration. We use the formulation to examine the interaction between the circulation and vertical distribution in controlling horizontal distribution of the common planktonic copepod Calanus finmarchicus in the Lower St. Lawrence Estuary, Canada. We first introduce diel migration into a simple one-dimensional model and then into a model of residual two-dimensional circulation patterns representative of conditions encountered in the Lower St. Lawrence Estuary. Results from the latter indicate that interactions between circulation and stage-specific swimming behaviors are the main mechanisms for aggregation of planktonic crustaceans at the head of the Laurentian Channel and highlight the implications of flushing of the surface-dwelling young stages for the population dynamics of C. finmarchicus in the Lower St. Lawrence Estuary.
Combined phylogenetic analysis of ribosomal ITS1 sequences and new chromosome data supports three subgroups of Dolly Varden char (Salvelinus malma)
Authors: Phillips Ruth B , Gudex Linda I , Westrich Kathleen M , DeCicco Alfred
Published: April 2011

A phylogenetic analysis of the subspecies of Salvelinus malma (Dolly Varden char) was done using DNA sequences from the first internal transcribed spacer (ITS1) of the ribosomal DNA (rDNA). Sequences were obtained from the northern S. malma malma from the Noatak River, Alaska, and the Kamchatka River, Russia; from the southern North American form S. malma lordi from the Fox River, Kenai peninsula, and Auke Bay near Juneau, Alaska; and from the southern Asian form S. malma krascheninnikovi from Belaya River in Sakhalin Island, Russia. These sequences were combined with others from Salvelinus alpinus (Arctic char) from several locations in the North Pacific and Europe and analyzed using maximum parsimony and neighbor joining algorithms with Salvelinus namaycush (lake trout) as an outgroup. The resulting trees had two well-supported groups: S. m. malma and S. m. krascheninnikovi in one group and S. m. lordi and various populations of S. alpinus in the other. Salvelinus m. malma and S. m. krascheninnikovi were sister taxa, and S. m. lordi was most closely related to S. alpinus from Northwest Territories (S. a. erythrinus). New chromosome data from S. m. malma from northwestern Alaska supported the three named subspecies because S. m. malma from both Alaska and Russia have 2n = 78 compared with 2n = 82 for the two southern forms and the location of the nuclear organizer regions (NORs) was different in each of the three subspecies.
Fertilization biology of the abalone Haliotis laevigata: laboratory and field studies
Authors: Babcock Russ , Keesing John
Published: April 2011

A combination of laboratory and field experiments with the commercial abalone species Haliotis laevigata showed that fertilization may be a limiting factor in some exploited populations when distances separating spawning individuals are too large. The effects of gamete age, gamete concentration, and gamete contact time in the laboratory were used to model fertilization success in situ and compared with experimental fertilization rates in the field. Highest fertilization rates in vitro (80%) were found for sperm concentrations in the range of 1 × 104 to 1 × 106·mL-1. Fertilization rates of 48 ± 1.7% (95% CI) were measured at separation distances of 2 m and dropped to 2.8 ± 0.7% (95% CI) at 16 m downstream, agreeing closely with rates predicted by the model. Recruitment failures reported for South Australian populations of H. laevigata have occurred when densities fell below ca.0.3 animals·m-2, or mean nearest-neighbor distances between 1 and 2 m. This density corresponds well to critical nearest-neighbor distances for fertilization success. Stocks at higher densities are predicted to have higher fertilization rates (ca.90%) such that fertilization success is not a factor limiting recruitment.
An individual-based model of pigment flux in lakes: implications for organic biogeochemistry and paleoecology
Authors: Cuddington K , Leavitt P R
Published: April 2011

Vertical fluxes of pigments are used in limnology to monitor phytoplankton abundance, herbivore grazing, ecosystem efficiency, and historical changes in production. However, significant pigment degradation can occur during algal sedimentation. We used an individual-based model of pigment flux to quantify the relative importance of production and degradation as controls of pigment sedimentation. Pigment deposition increased with production, sinking rate, and phytoplankton depth and declined as lake depth and the depth of oxygen penetration increased. Unexpectedly, pigment sedimentation rate was not sensitive to variation in photooxidation rates, even though bleaching accounted for the second greatest amount of pigment loss. Digestion by zooplankton caused the most pigment degradation, but grazing increased pigment deposition when digestive losses were less than those due to oxidation of pigments in ungrazed cells. The model suggests that algal production may be underestimated in sedimentation studies that do not consider variability in water column depth. Further, comparisons with paleoecological analyses suggest that some inferred increases in production during lake ontogeny may arise from changes in regulation of pigment fluxes rather than from increased algal production.
Percentage land use in the watershed determines the water and sediment quality of 22 marshes in the Great Lakes basin
Authors: Crosbie Barb , Chow-Fraser Patricia
Published: April 2011

Data from 22 Ontario marshes were used to test the hypothesis that distribution of forested, agricultural, and urban land in the watershed determines the water and sediment quality of Great Lakes wetlands. The first three components of the principal components analysis explained 82% of the overall variation. PC1 ordinated wetlands along a trophic gradient; species richness of submergent vegetation decreased with PC1 scores. PC2 reflected the content of inorganic solids and phosphorus in sediment and the ionic strength of the water. Both PC1 and PC2 scores were positively correlated with percent agricultural land, whereas PC1 scores were negatively correlated with forested land. Correlation between PC1 and agricultural land improved when best-management practices were considered. Accounting for common carp (Cyprinus carpio) disturbance did not confound the relationship between land use and water quality. PC3, driven by soluble reactive phosphorus and nitrate nitrogen concentration in the water, was not correlated with land use. Concentrations of polycyclic aromatic hydrocarbons and Metolachlor were correlated with urban and agricultural land, respectively, and may be useful as land use surrogates. Watershed management favouring the retention of forested land, or creation of buffer strips to trap agricultural runoff in the drainage basin, should help maintain aquatic plant diversity in coastal wetlands.
Managing the decline of Pacific salmon: metapopulation theory and artificial recolonization as ecological mitigation
Authors: Young Kyle A
Published: April 2011

Pacific salmon (Oncorhynchus spp.) in the Pacific Northwest of North America have suffered regional declines and local extinctions primarily because of freshwater habitat destruction and overexploitation by fisheries. Management efforts to reverse this trend have correctly focused on habitat restoration and enhancement and stricter regulation of fisheries. Metapopulation theory and the ecology of the genus suggest that the addition of management efforts that artificially increase the rate of colonization of presently unoccupied habitats may promote the recovery and persistence of Pacific salmon in an ecologically realistic way. Such programs are conceptually and operationally different from traditional stock transfer and enhancement programs, which aimed to maintain a harvestable surplus of salmon in the face of habitat destruction and overfishing. I argue that artificial recolonization programs should be viewed as ecological mitigation, aimed at hastening the return of natural demographic and evolutionary processes, and hope here to promote an open discussion of their merits and risks as such.
Spawn date dependent survival and growth in the early life stages ofHypoptychus dybowskii(Gasterosteiformes)
Authors: Narimatsu Yoji , Munehara Hiroyuki
Published: April 2011

The effects of spawn date on survival and growth during the embryonic, larval, and juvenile stages of a coastal fish, Hypoptychus dybowskii (Gasterosteiformes), were examined. Monitoring of embryos using SCUBA showed that the embryonic period decreased as the season progressed and the hatching rate was lowest for the early-spawn cohort (EC). Analysis of otolith daily growth increments indicated that EC larvae had much lower survival and growth rates than larvae of middle-spawn (MC) and late-spawn cohorts (LC), but there were no large differences in either rate among juveniles of the three cohorts. EC suffered the highest mortality rates in the embryonic and larval stages; these high rates were linked with slow development and growth, probably caused by below-optimum water temperatures. EC fish grew over a longer period and reached larger body size than MC and LC fish. These results suggest that intraannual variations in growth pattern and survival rate in the embryonic and larval stages were caused by spawn date differences, which favored the LC in the study year, but the EC might have a size-dependent advantage in survivorship and reproductive success during the postjuvenile stages.
Concentrations of strontium in the pectoral fin rays of the white sturgeon (Acipenser transmontanus) by laser ablation sampling - inductively coupled plasma - mass spectrometry as an indicator of marine migrations
Authors: Veinott Geoff , Northcote Tom , Rosenau Marvin , Evans R Douglas
Published: April 2011

Laser ablation sampling - inductively coupled plasma - mass spectrometry (LAS-ICP-MS) was an effective technique for the comparison of relative Sr concentrations in the opaque growth zones (annuli) in the fin rays of white sturgeon (Acipenser transmontanus). Three of 29 Fraser River white sturgeon (10.3% of the sample) showed significantly higher Sr fin ray concentrations in at least one annulus compared with the remainder of the fin ray, and this was interpreted as evidence of marine migrations. Eleven other individual fish had significantly higher mean Sr concentrations in their first 15 annuli compared with annuli 16-30 but lower than the concentrations of the three putative diadromous fish, and this was interpreted as evidence of time spent in the estuary. Eight Fraser River fish greater than 15 years old showed no significant increase in fin ray Sr concentations in the first 15 annuli, and Sr concentrations remained below 350 ppm throughout their lives. These individuals were considered likely to have spent most of their lives in a freshwater environment. Based on the evidence in this study, it is probable that the majority of white sturgeon in the lower Fraser River are not diadromous, but many spend extended periods of time in the Fraser River estuary as juveniles.
Planktivory by the predacious cladoceranBythotrephes longimanus: effects on zooplankton size structure and abundance
Authors: Wahlström Eva , Westman Erika
Published: April 2011

In order to study density-dependent effects of invertebrate planktivory, four different densities of Bythotrephes longimanus were inoculated into mesocosm enclosures with a mixed zooplankton community. Changes in size structure and abundance of zooplankton and phytoplankton communities were recorded over a period of 3 weeks. High densities of Bythotrephes were able to reduce total zooplankton abundance, which was mainly due to a decrease in the density of the relatively large species Holopedium gibberum. The density of the smaller species Bosmina longirostris was also reduced with increasing densities of Bythotrephes, whereas rotifer abundance remained largely unaffected. The mean size of Holopedium increased with increasing densities of Bythotrephes. Despite the decrease in total zooplankton biomass in high-Bythotrephes treatments, no effect of Bythotrephes density on primary producers was observed. Our experiment shows that predacious cladocerans may reduce macrozooplankton biomass, large as well as small species. Predation from invertebrate planktivores results in a zooplankton community consisting of larger individuals. Comparing our experimental densities with densities of Bythotrephes found in natural systems suggests that invertebrate planktivores may influence size structure and abundance of zooplankton communities even in lakes with planktivorous fish.
Potential effects of maternal factors on spawning stock–recruitment relationships under varying fishing pressure
Authors: Scott Beth , Marteinsdottir Gudrun , Wright Peter
Published: April 2011

The use of spawning stock biomass as a direct measure of reproductive potential may not be valid because of age- or size-specific differences in fecundity and the effect of maternal size and condition on offspring viability. In this study, we examine the potential significance of these effects using modelled Atlantic cod (Gadus morhua) populations. We quantify how changes in the age composition of the spawning stock, due to a range of fishing pressures and under different stock-recruitment relationships, could influence the reproductive output. Quantitative comparisons were made between a "standard" population where all age-classes only suffer natural instantaneous mortality (M = 0.2) and populations that suffer increasing levels of fishing pressure (F = 0.0-1.0). The results of the modelling exercise suggests that if the effects of the loss of more fecund older/larger individuals in the population are not considered, the number of potential recruits produced by populations under higher levels of fishing mortality could be overestimated by as much as 60%. When age/size-related maternal effects on egg viability are also considered, the amount of potential recruits can be overestimated by a further 10% in the heavily exploited populations.
Elemental distribution within polymorphic inconnu (Stenodus leucichthys) otoliths is affected by crystal structure
Authors: Brown Randy , Severin Kenneth P
Published: April 2011

The chemistry and crystal structure of sagittal otoliths from inconnu (Stenodus leucichthys) were examined optically, with an electron microprobe, a scanning electron microscope, and with X-ray diffraction techniques. The distributions of strontium (Sr), sodium (Na), potassium (K), and calcium (Ca) were determined with line scans and area maps of thin, transverse otolith sections. Regions depleted in Sr, Na, and K were found to be discordant with optical annuli and were optically distinct from other regions of the otoliths. These patterns of trace element depletion cannot be explained by models of otolith growth that are based on ionic composition of endolymph fluids as the sole control of otolith composition. Electron micrographs showed the depleted regions of the otoliths to be of a different crystal structure than other regions of the otoliths. X-ray diffraction analyses revealed the presence of vaterite in otoliths with depleted regions, while otoliths without depleted regions showed no evidence of vaterite. The depleted areas may be composed of vaterite, and the crystal structure of vaterite may prevent certain trace elements from incorporating in the otolith. Scientists using fish otolith chemistry to infer environmental conditions or life history should be aware that elemental abundance within otoliths may be affected by other processes as well.
Nitrogen-phosphorus relationship in high mountain lakes: effects of the size of catchment basins
Authors: Morales-Baquero Rafael , Carrillo Presentación , Reche Isabel , Sánchez-Castillo Pedro
Published: April 2011

We analyzed the changes in epilimnetic total nitrogen (TN), total phosphorus (TP), dissolved inorganic nitrogen (DIN), and soluble reactive phosphorus (SRP) in 31 small high-mountain lakes in the Sierra Nevada (Spain) during an annual cycle, just after the spring thaw, and in the middle of the growing season. Chlorophyll a, TN, and TP increased, whereas the TN:TP ratio fell substantially between the two periods, reaching values generally between 25 and 10 (by weight). On the contrary, DIN, SRP, and DIN:SRP ratios were similar for both periods in each lake. DIN:SRP ratios generally ranged from 5 to 20 (by weight). This ratio was low in the lakes with small catchment areas and increased progressively with catchment basin size. A regression analysis for the smallest catchments showed that chlorophyll a concentrations were not accounted for by variability in TP concentration. The results obtained are discussed in relation to the influence of episodes of Saharan dust, rich in P, reaching the Southern Mediterranean area.
Food consumption and growth in maturing Atlantic salmon (Salmo salar)
Authors: Stead Selina M , Houlihan Dominic F , McLay H Anne , Johnstone Ray
Published: April 2011

Circulating levels of the steroid hormones 11-ketotestosterone (11-KT) and 17β-estradiol (E2), voluntary food intake, and growth performance were measured in individual Atlantic salmon (Salmo salar) over the year preceding their maturation as grilse. 11-KT and E2 were measured by radioimmunoassay, and X-radiography was used to measure food consumption rates. Two phases of sexual maturation were identified: the early phase (October 1992 - April 1993) was characterized by slowly rising steroid hormone levels concomitant with relatively high rates of food consumption and growth, and in the late phase (May-October 1993), steroid hormone levels increased more rapidly and growth rates decreased in association with inappetence. Significant linear relationships were observed between food consumption and specific growth rates of fish throughout the study (ANCOVA, p < 0.05). Slopes and intercepts of regressions were similar for fish during early maturation, while a lower intercept and steeper slope (ANCOVA, p < 0.05) was observed during the later stages of maturation. In November, January, February, and April, fish in which steroid hormone levels were elevated were significantly heavier than those in which hormone levels were basal. There were no significant differences in specific growth rates (except in February), food consumption, or weight-specific food conversion ratio (except in August and October) associated with maturation status.
The reappearance of spawning Atlantic herring (Clupea harengus) on Aberdeen Bank (North Sea) in 1983 and its relationship to environmental conditions
Authors: Corten Ad
Published: April 2011

Evidence is presented in support of the hypothesis that the reappearance of spawning Atlantic herring (Clupea harengus) on Aberdeen Bank in 1983, after an absence of 16 years, was related to an increased Atlantic inflow in the area. Two Atlantic copepod species, Metridia lucens and Candacia armata, showed a simultaneous increase in the years when spawning herring returned to Aberdeen Bank. During the late 1960s, both species declined at the time when the spawning population on Aberdeen Bank disappeared. Earlier work has demonstrated that an increased Atlantic inflow results in a southward displacement of plankton concentrations and feeding herring in the northwestern North Sea. I hypothesize that such a southern distribution of the herring stock, caused indirectly by the increased Atlantic inflow, influenced recruit spawners to choose the nearby Aberdeen Bank as their spawning ground in 1983. Fluctuations of the spawning populations in the northern North Sea during earlier decades are explained by switches of recruitment between the northern and southern population, as a result of variations in latitudinal distribution of the recruiting year-class.
Crue éclair de juillet 1996 dans la région du Saguenay (Québec). 1. Impacts sur la colonne d'eau de la baie des Ha! Ha! et du fjord du Saguenay
Authors: Pelletier Émilien , Mostajir Behzad , Roy Suzanne , Gosselin Michel , Gratton Yves , Chanut Jean-Pierre , Belzile Claude , Demers Serge , Thibault Delphine
Published: April 2011

A flash flood, which occurred in July 1996 in the Saguenay area (Quebec), transported millions of tons of sediment to the upstream section of the Saguenay Fjord and the Baie des Ha! Ha! in a few days. This first article reports the physical, chemical, and biological observations obtained for the water column in September 1996 and August 1997 and attempts to define indicators that can adequately characterize the effects of the flood on the water column. The chemical composition, the abundance, and the distribution of suspended particles clearly show the influence of the flood on the composition of particles in the water column of the bay and the fjord 2 months and even 1 year after the flood. However, biological indicators such as the abundance and the distribution of phytoplankton and zooplankton species determined in September 1996 are only slightly different between the Bay and the Fjord and show little difference with preflood data. The zooplankton physiological state appears to be a very good indicator of the health of the whole pelagic ecosystem.
Isotopic composition of otoliths as a chemical tracer in population identification of sockeye salmon (Oncorhynchus nerka)
Authors: Gao Y W , Beamish R J
Published: April 2011

The feasibility of stable oxygen and carbon isotope ratio (δ18O and δ13C) analyses in sagittal otoliths of sockeye salmon (Oncorhynchus nerka) was tested by analyzing the seasonal and annual otolith zones of 44 samples collected from different localities in the northeast Pacific coast. The δ18O and δ13C values of these otoliths ranged from -14.23 to +1.62 and from -15.18 to -3.17, respectively. The δ18O variations can be divided into two stages from freshwater (-14.2 to -2.5) to marine (-2.5 to +1.6) that were consistent with the life history of sockeye salmon from juvenile to adult stages. The transition occurred after age 1, during which the timing of seaward migration of smolts was different. The marine component of the isotope variation in sockeye salmon otoliths (ages > 2) was uniform but showed a consistent and strong shift towards oceanic changes around 1996. Thus, δ18O and δ13C values of otoliths can be potentially used as a chemical tracer in population identification, and their marine portions can be used in the study of ocean environmental changes.
First observations of tumor-like abnormalities (exophytic lesions) on Lake Michigan zooplankton
Authors: Omair M , Vanderploeg Henry A , Jude David J , Fahnenstiel Gary L
Published: April 2011

Tumor-like abnormalities (exophytic lesions) were found on a variety of planktonic calanoid copepods and cladocerans (Diaptomus spp., Epischura lacustris, Limnocalanus macrurus, Polyphemus pediculus, Diaphanosoma sp., and Daphnia galeata mendotae) collected from inshore (3-m depth contour) and offshore (100- to 110-m depth contours) stations of eastern Lake Michigan. The abnormalities, which were quite large relative to animal size and variable in shape, are documented in photographs. Abnormality incidences among species ranged between 0 and 72%. Predatory species of calanoids and cladocerans had higher incidences of tumors than herbivorous species. The abnormalities on some copepods were very similar to cysts described for calanoid copepods in Lago Maggiore, Italy, which like Lake Michigan is undergoing oligotrophication. The recent appearance of the lesions in Europe and North America may indicate an emerging global phenomenon that has a common cause.
An experimental study on variations in stable carbon and nitrogen isotope fractionation during growth of Mysis mixta and Neomysis integer
Authors: Gorokhova Elena , Hansson Sture
Published: April 2011

The trophic isotope fractionation of mysids, in response to a change in the isotopic composition in their diet, was examined in the laboratory. Field-caught Mysis mixta and Neomysis integer had similar δ13C values, ranging between -23.1 and -21.5. They also had similar δ15N values, and for both species, this value increased with body size. Experimental starvation did not change the isotopic composition. To test for metabolic fractionation of isotopes, the mysids were fed different diets, newly hatched Artemia and detrital Enteromorpha. The isotopic composition was monitored in abdominal muscle tissue, exoskeleton, and feces over 12 weeks. The δ13C composition in muscle tissue had not reached an isotopic equilibrium with the diet at the end of the experiment, while the exoskeleton came into equilibrium with the food in 2-3 weeks. Muscle was enriched in 15N relatively to the food, +3.6 for Artemia and +2.7 for Enteromorpha. The isotopic composition in muscle, exuviae, and feces may form a basis for diet reconstruction of mysids. The feces δ13C and δ15N values mirror the diet over the last few hours, exuviae δ13C values represent nutrients metabolized 2-3 weeks ago, and muscle tissue integrates the isotopic signal over a relatively long period.
Effects of preservatives and acidification on the stable isotope ratios (15N:14N, 13C:12C) of two species of marine animals
Authors: Bosley Keith L , Wainright Sam C
Published: April 2011

When animal tissues are prepared for stable isotope ratio analysis, they may or may not be treated with acid prior to analysis to remove carbonates and are loaded into tin or silver weigh boats for quantitative combustion. The effects of these methodological variations are poorly known. The effects of various preservation methods on isotopic compositions are also poorly known. We tested the effects of four preservation methods, (i) formalin, (ii) formalin followed by a transfer to ethanol (formalin/EtOH), (iii) saturated mercuric chloride solution, and (iv) freezing/freeze-drying, on the carbon and nitrogen isotopic composition of the muscle tissue of juvenile winter flounder (Pleuronectes americanus) and the tails (including exoskeleton) of mud shrimp (Crangon septemspinosa). Freezing and freeze-drying were the only preservation methods that did not affect stable isotope ratios of carbon and nitrogen. Formalin, formalin/EtOH, and saturated mercuric chloride solution produced significant increases in δ15N values (0.5-1.4) and decreases in δ13C values (0.6-2.3) compared with frozen samples. There was also an increase in the variability of δ15N and (or) δ13C values. We also tested the effects of acidification by comparing samples that were acidified either by fuming with concentrated HCl or by the direct application of 1 N HCl containing 1.0% platinum chloride (a combustion catalyst) to unacidified samples. Neither concentrated HCl fumes nor HCl/platinum chloride had a significant effect on the δ15N or δ13C values of either species compared with unacidified samples. Therefore, acidification may be unnecessary in the preparation of some marine animals. Finally, we compared the effects of two types of sample boats: tin and silver. We found no significant effect of boat material on the δ15N or δ13C values of either species.
Influence of waterborne cations on zinc uptake and toxicity in rainbow trout,Oncorhynchus mykiss
Authors: Alsop Derek H , Wood Chris M
Published: April 2011

The effects of waterborne cations on65Zn uptake, Zn toxicity, and relationships with Ca uptake were examined in juvenile rainbow trout, Oncorhynchus mykiss, in soft water. Whole-body Zn uptake (waterborne [Zn] = 100 μg·L-1= 1.5 μM) was greatly reduced by a variety of cations. This reduction was directly related to the concentration of positive charges, regardless of which ion carried that charge. Thus, 1.0 mM Na+, K+, NH4+, and N-methyl-D-glucamine+and 0.5 mM Mg2+(divalent) reduced Zn uptake to a similar extent (approx. 50%), indicating a relatively nonspecific competition for anionic sites on the gill. Ca2+was an exception and was more potent at reducing Zn uptake, likely because only Ca2+would also compete for absorption. Although Na+and Mg2+were able to markedly reduce Zn uptake, they had no effect on Zn toxicity (measured with 96-h LC50tests), a result paralleled by their inability to restore Ca2+uptake that was inhibited by Zn. In contrast, Ca2+reduced Zn toxicity and restored Ca2+uptake. These results partially dissociate Zn uptake from Zn toxicity, implicate disturbed Ca2+uptake as the toxic mechanism, and have profound implications for water quality criteria where Ca2+and Mg2+(the two "hardness" cations) are traditionally considered to be equally protective.
Relationship among adult body length, abundance, and ocean temperature for British Columbia and Alaska sockeye salmon (Oncorhynchus nerka), 1967–1997
Authors: Pyper Brian J , Peterman Randall M
Published: April 2011

Body length of adult Pacific sockeye salmon (Oncorhynchus nerka) has decreased significantly in recent years. We used 69 time series of age-specific body-length data (1967-1997) for 30 sockeye salmon stocks from southern British Columbia to western Alaska to test hypotheses about the effects of oceanographic conditions and competition on growth rate of sockeye salmon. Using principal components analysis (PCA), we constructed a single time series (PC1) that represented the dominant pattern of variability in length-at-age shared among these stocks. Taking into account time trends and autocorrelation in residuals, we found that increases in total Gulf of Alaska sockeye abundance and increases in sea-surface temperature (SST) across the Gulf of Alaska were significantly associated with reduced adult body length. Abundance and SST together accounted for 71% of the variability in PC1. Although researchers have documented increases in both abundance of sockeye salmon and their food in the northeastern Pacific Ocean over the last few decades, it is possible that increased food was more than offset by increased sockeye abundance, leading to greater competition and reduced body size.
Metallothionein-like proteins in Macoma balthica: effects of metal exposure and natural factors
Authors: Mouneyrac C , Geffard A , Amiard J C , Amiard-Triquet C
Published: April 2011

Biological processes involved in the tolerance acquired by populations chronically exposed to metal pollution in the environment were examined in baltic clams (Macoma balthica) originating from both industrialized and clean areas and in clams exposed experimentally to metals. It has been shown previously that clams surviving Ag and Hg exposure at LT50 did not protect themselves by accumulating smaller amounts of metals than clams that failed to survive, so attention was focussed on the physicochemical forms of storage of the accumulated metals. Silver was found to be predominantly bound to insoluble forms and Cd and Hg to soluble forms. In both controls and contaminated clams, a metallothionein-like protein (MTLP) has been shown to be present, the concentrations of which did not depend on the geographical origin of the clams. The significant relationship between metal and MTLP concentrations shown in the baltic clams suggests that the induction of this protein could provide a useful tool for the biomonitoring of metal pollution. The influence of natural factors (season, weight), however, must be taken into account when interpreting such data.
An investigation into iron-stimulated phytoplankton productivity in epipelagic Lake Erie during thermal stratification using trace metal clean techniques
Authors: Twiss Michael R , Auclair Jean-Christian , Charlton Murray N
Published: April 2011

We tested the hypothesis that phytoplankton productivity in pelagic Lake Erie is limited by low Fe bioavailability during the period of thermal stratification. Iron enrichment (20 and 200 nM Fe) of water sampled from the eastern basin surface water (5 m depth) in July 1996 revealed a dramatic 180 and 30% increase in the standing crop of the picoplankton (0.2-2 µm) and nanoplankton (2-20 µm) size fractions, respectively. Light-saturated rates of photosynthesis for picoplankton increased 2.8 times that of the controls within 24 h. In contrast, simultaneous P and Fe enrichment experiments carried out in July 1997 and August 1998 with water samples from three pelagic stations revealed that P enrichment alone stimulated phytoplankton growth, although at several stations, phytoplankton yield was greater in combined P- and Fe-amended experiments relative to P-enriched treatments. Periodogram analysis of meteorological buoy wave height data and heat budgets calculated from thermal profiles in the eastern basin revealed important interyear differences in precruise conditioning of the epilimnion. Low-frequency, turbulent mixing events that characterized the 30-day precruise period in the years 1997 and 1998 relative to 1996 may have prevented Fe-stressed conditions in the phytoplankton community studied in 1997 and 1998.