bluuebunny/crossref_metadata_2025 huggingface dataset:
Overwinter growth and survival of age-0 largemouth bass (Micropterus salmoides): revisiting the role of body size
Authors: Garvey James E , Wright Russell A , Stein Roy A
Published: April 2011

How large size affects overwinter growth and survival of age-0 fish may vary as a function of food, predation, and energetic condition. During two winters in Ohio, we assessed how these factors affected growth and survival of varying sizes of age-0 largemouth bass (Micropterus salmoides) by combining a field survey (N = 2 reservoirs) with multiscale experiments (reservoirs, ponds, outdoor pools). In our survey, more small (< 100 mm total length) individuals died by spring in one reservoir than in the other. Similarly, when we stocked two reservoirs with marked age-0 largemouth bass in fall, mortality of small individuals was higher in one system overwinter, potentially due to differences in predation intensity. In ponds during two winters, size-selective mortality of small largemouth bass occurred in only two of eight ponds, potentially as a function of cannibalism. Varying ration in pools (starved, 0.5× maintenance, or 1.5× maintenance) did not affect survival, even though starved individuals lost substantial wet weight and energy content. Only when predators were present did small individuals die at high rates, although energy depletion may have contributed to predatory mortality. To increase the probability of overwinter survival, managers should seek to improve first-summer growth, reduce winter predation, and increase winter forage.
Interactions among adult demography, spawning date, growth rate, predation, overwinter mortality, and the recruitment of largemouth bass in a northern lake
Authors: Post David M , Kitchell James F , Hodgson James R
Published: April 2011

Using 12 years of data, we evaluated the mechanisms controlling largemouth bass, Micropterus salmoides, recruitment in a lake near the northern extent of the largemouth bass range. We found that complex interactions among adult demographics, size-selective predation, and overwinter mortality regulate the number of largemouth bass surviving the first year of life. The largest recruitment events required at least a moderate number of adults, but a large number of adults was not sufficient to produce a large cohort of largemouth bass. Predation was controlled by the number of both adult and juvenile bass and was not strongly correlated with reproductive output. Overwinter mortality was size dependent, strongly affecting bass entering the winter at <50-60 mm in length, and likely the result of starvation. Predation and overwinter mortality interacted with spawning date and growth rate to produce variable but predictable patterns of first year survival. At high adult and juvenile densities, predation regulates first year survival. At low adult and juvenile densities, first year survival was regulated by adult demographics and interactions among spawning date, growth rates, and overwinter mortality. Although we can forecast coarse patterns of cohort survival, the survival of individual fish was more difficult to predict because length and age were not highly correlated.
The variability of the gustatory sensibility in salmonids, with special reference to strain differences in rainbow trout, Oncorhynchus mykiss
Authors: Hara Toshiaki J , Carolsfeld Joachim , Kitamura Shoji
Published: April 2011

To determine the functional variability of the gustatory system in salmonids, we examined electrical responses of the palatine nerve to amino acids in nine strains of rainbow trout (Oncorhynchus mykiss), four additional Oncorhynchus species, and two Salvelinus species. All species exhibited extreme sensitivity to L-proline. Besides the Pro receptors (interacting with L-proline, hydroxy-L-proline, and L-alanine), Phe (L-phenylalanine, L-leucine), AGP (L-α-amino-β-quanidinopropionic acid, betaine), and Arg receptors (L-arginine) were involved in amino acid detection. On the basis of the functional receptor types, the rainbow trout strains fell into two groups: (1) Kamloops, Manx, Mount Lassen, Sunndalsøra, Tagwerker, and Victoria and (2) Nisqually, Nikko, and steelhead. The former group originates primarily from inland waters, whereas the latter originates from coastal waters. Response patterns of other salmonid species were similar to those of group 2 rainbow trout. Response patterns did not change as a result of environmental conditions. We thus conclude that the functional variability of the gustatory system is not attributable to local environmental factors but rather may be genetic in origin. Similar variability may exist in responses to other chemicals, including toxicants, and we conclude that in studies employing salmonids it is important to identify the stock of fish in addition to the species.
Effect of ice formation on selection of habitats and winter distribution of post-young-of-the-year Atlantic salmon parr
Authors: Whalen Kevin G , Parrish Donna L , Mather Martha E
Published: April 2011

We determined how ice affects selection of habitats and distribution of post-young-of-the-year Atlantic salmon (Salmo salar) parr during winter. Night snorkeling surveys were completed between November and April to evaluate parr habitat use and movements. Systematic measurements of water depth and velocity were recorded during ice-free and [Formula: see text]55% iced conditions to quantify habitat availability. Ice formation altered the distribution and reduced the abundance of habitats commonly used by parr; differences between parr habitat use and habitat availability were greatest when ice was present. Edge ice formation resulted in the concentration of flows, and areas of high flow were formed in midchannel; few parr were observed in midchannel after ice had formed. Through the winter, most parr were found lateral to high flows on the ice edge boundary or in the post-ice period lateral to the stream midchannel. The correspondence of parr movements during winter to changes in the physical habitat associated with ice formation indicates that movements and redistributions may be important for survival in streams affected by ice.
Effect of winter food deprivation on growth and sexual maturity of Atlantic salmon (Salmo salar) in seawater
Authors: Duston J , Saunders R L
Published: April 2011

By identifying individual Atlantic salmon (Salmo salar) smolts (age 1+, mean weight 95 g), a tank study with four treatments (n = 175 fish per tank) indicated that maturation as grilse is associated with changes in somatic growth over many months, from July of the first summer in seawater onwards. The grilse rate in both sexes was associated with a relatively high condition factor from July onwards, but was independent of fork length. Food deprivation in either early winter (November-December, 8.2-4.1°C), late winter (February-April, 0.7-4.0°C), or both early and late winter (double deprived) reduced the female grilse rate (p < 0.01) to 4, 7, and 2% versus 18% in the control, whereas male grilse rate was reduced by a lesser degree (p > 0.05), 43, 39, and 33% versus 44% in the control. Mean condition factor among both maturing and immature fish decreased by a similar degree due to food deprivation but from spring onwards increased by a faster rate among incipient grilse. In a large experiment in four sea cages (each n = 3885 fish) using similar food deprivation treatments, the reduction in grilse rate was statistically significant in both sexes: among males, 28-36 versus 43% in the control; among females, 3-4 versus 6% in the control.
Predator foraging mode shifts affecting mortality of juvenile fishes during the subarctic spring bloom
Authors: Willette T M , Cooney R T , Hyer K
Published: April 2011

We examined some processes affecting foraging mode shifts among Pacific herring (Clupea pallasi) and walleye pollock (Theragra chalcogramma) during the spring bloom in Prince William Sound, Alaska. The duration of the bloom of the copepod Neocalanus was reduced when the surface layer became strongly stratified in May. Stronger surface layer stratification observed in 1995 and 1996 was associated with higher salinities below 50 m depth compared with 1994. Functional response models for Pacific herring and adult walleye pollock feeding on large calanoid copepods indicated that these predators began to switch to alternative prey as the mean biomass of large calanoid copepods declined below about 0.2 and 1.0 g/m3, respectively. Analysis of covariance indicated that Pacific herring and walleye pollock tended to switch from large calanoid copepods to nekton prey after the copepod bloom declined (p = 0.028). Mortality of pink salmon (Oncorhynchus gorbuscha) was negatively correlated with the duration of the copepod bloom during the juvenile life stage (p = 0.013), as well as with juvenile growth rate (p < 0.001), juvenile body weight at release (p < 0.001), and the number of juveniles released (p < 0.001). Our results indicate that bottom-up processes affecting the duration of the spring bloom and juvenile growth also modify top-down processes involving foraging mode shifts toward piscivory and mortality of juvenile fishes.
Periphyton biomass and community composition in rivers of different nutrient status
Authors: Chételat J , Pick F R , Morin A , Hamilton P B
Published: April 2011

Epilithic periphyton was investigated in riffle zones of 13 rivers in southern Ontario and western Quebec to describe how algal biomass and community composition vary with nutrient concentration and water velocity during summer. Algal biomass (milligrams chlorophyll a (Chl a) per square metre) was strongly correlated with total phosphorus concentration (r2 = 0.56, p < 0.001) and conductivity (r2 = 0.71, p < 0.001) of the overlying water but unrelated to water velocity over the range of 10-107 cm·s-1. Differences in periphyton Chl a were associated with changes in biomass of Chlorophyta (r2 = 0.51, p = 0.001) and Bacillariophyta (r2 = 0.64, p < 0.001) and were not related to Rhodophyta and Cyanophyta biomass (p > 0.10). The relative proportions of taxonomic divisions varied with total standing stock. Percent Chlorophyta biomass increased with periphyton Chl a and was the largest fraction at moderately eutrophic sites. Rhodophyta contributed the most biomass at sites with the lowest Chl a. Cladophora, Melosira, and Audouinella biomasses were positively correlated with total phosphorus concentration over the range of 6-82 µg·L-1 (r2 = 0.39-0.64, p < 0.005), and these genera were dominant at sites with the highest nutrient concentrations.
Relationship between chinook salmon (Oncorhynchus tshawytscha) redd densities and PHABSIM-predicted habitat in the Merced and Lower American rivers, California
Authors: Gallagher Sean P , Gard Mark F
Published: April 2011

An index of chinook salmon (Oncorhynchus tshawytscha) spawning habitat predicted using the physical habitat simulation system (PHABSIM) component of the instream flow incremental methodology was compared with redd densities and locations for sites in the Merced River, California, during 1996 and with redd numbers in sites in the Merced and Lower American rivers, California, from 1989 through 1996. Predicted weighted useable area (WUA) was significantly correlated with chinook salmon spawning density and location at five of seven sites in the Merced River. At the microhabitat level, in the Merced River during 1996, there was a significant relationship between chinook salmon redd location and predicted WUA. Cells with more WUA in the Merced River tended to have more redds. At the mesohabitat level, there was a significant relationship between redd density and predicted WUA in both rivers. Transect areas in the Merced River with higher predicted WUA had more redds. Sites with higher numbers of redds had more predicted WUA. Significant correlations between predicted WUA and spawning locations increase confidence in the use of PHABSIM modeling results for fisheries management in the Merced and Lower American rivers as well as in other rivers.
Multispecies spatial assessment models for the British Columbia groundfish trawl fishery
Authors: Walters Carl J , Bonfil Ramón
Published: April 2011

A multispecies spatial model is proposed for evaluation of trawl management strategies and tested with data from British Columbia groundfish. Minimum stock sizes are estimated for 16 species using spatial catch per unit effort data; these data indicate that only small proportions of most stocks are exposed to fishing at any time and that exchange rates of fish between the grounds and other habitats are rapid. A gravity model for spatial effort allocation predicts substantial side effects of marine protected areas or discarding of particular species on nontarget species/grounds due to redistribution of fishing effort. Multispecies, multiground delay-difference models are used in conjunction with the gravity model for spatial effort distribution to predict long-term population responses to various regulatory strategies. This simulation suggests that species composition and spatial structure of the fishery are changing slowly due to reduction in abundance of long-lived species, but rapid collapses of target stocks are unlikely due to spatial redistribution of effort in response to local declines. We question whether quota management (individual vessel quotas) can be safely implemented due to extreme uncertainty about current stock sizes and suggest that a better strategy may be to simply denominate fishing rights as individual effort quotas while providing protection for sensitive stocks through carefully placed marine protected areas.
Invasion of Lake Ontario by the Ponto–Caspian predatory cladoceran Cercopagis pengoi
Authors: MacIsaac Hugh J , Grigorovich Igor A , Hoyle James A , Yan Norman D , Panov Vadim E
Published: April 2011

Cercopagis pengoi, a waterflea native to the Ponto-Caspian region, was discovered during 1998 in Lake Ontario. Individuals were found throughout the lake during summer snagged on sportfishing lines. The population included parthenogenetic (92%) and sexual (2%) females and males (6%). Cercopagis has a very long caudal appendage that is more than five times the body length and terminates in a distinctive loop. Females and males from Lake Ontario were significantly smaller than individuals from the Neva Estuary, Baltic Sea. In Eurasia, C. pengoi occurs in relatively warm fresh and brackish waters (0-14) at population densities usually <3000 individuals·m-3; mean and maximum population densities in Lake Ontario were 170 and 322 individuals·m-3, respectively. The presence of females with resting eggs indicates that Cercopagis will likely establish in Lake Ontario. As with other recently introduced invertebrates, Cercopagis likely was transported to the Great Lakes in ballast water from eastern Europe. The rapid influx of Ponto-Caspian species into the Great Lakes warrants further study including identification of source populations, mechanisms of dispersal, impacts on recipient ecosystems, and efficacy of ballast water exchange programs.
Implications of density-dependent juvenile growth for compensatory recruitment regulation of haddock
Authors: Marshall C Tara , Frank Kenneth T
Published: April 2011

Data from bottom trawl surveys conducted by Canada and the United States were used to describe temporal trends in the length of haddock ages 1-4 on the southwestern Scotian Shelf (SWSS) and Bay of Fundy. From 1970 to 1995, the length of juvenile (age-1) haddock on the SWSS was negatively correlated with the abundance of adults (age-4+). Within year-classes temporal trends in juvenile length persisted through to the adult stage such that year-classes that were small(large) at age-1 were small(large) at age-4. These two results were combined with the positive correlation observed between recruitment and the body size characteristics of haddock on the SWSS in a conceptual model of compensatory recruitment regulation. In the model high adult abundance decreases growth of juveniles leading to smaller-sized adults and subsequently lower recruitment. Conversely, low adult abundance results in increased growth of juveniles leading to larger adults and higher recruitment. Density-dependent growth of juveniles, combined with the positive correlation between recruitment and adult body size, constitutes a compensatory mechanism for adjusting future haddock recruitment according to present adult abundance.
Signals of climate trends and extreme events in the thermal stratification pattern of multibasin Lake Opeongo, Ontario
Authors: King Jacquelynne R , Shuter Brian J , Zimmerman Ann P
Published: April 2011

Previous empirical observations on thermocline response to warmer conditions have been contradictory. Given that a deepening thermocline was observed for a small lake (0.5 km2) and a shallowing thermocline was observed for a larger system (73.6 km2), these contradictions may be attributable to differences in lake size and the diminishing influence of water clarity on mixing depth. The four basin systems of Lake Opeongo, Ontario, Canada, range in size from 4.4 to 22.1 km2 and build an empirical suite of stratification responses to climate variation for a wide range of lake sizes. From 1958 to 1996, lake temperature profiles were taken in the four major basins of Lake Opeongo. Canonical correlation analyses linked earlier iceout dates, warm July-August air temperatures, and relatively high amounts of bright sunshine in July and August with warmer midsummer epilimnia and shallower midsummer thermoclines for all four basins. The occurrence of stratification patterns associated with warmer climatic conditions increased (r = 0.44, p < 0.01) in parallel with the recent (post-1965) global warming trend. Such patterns also tended to occur in El Niño years. Stratification conditions with cooler midsummer epilimnia and deeper thermoclines tended to occur in La Niña years and provided a pronounced signal in 1992, the year that experienced a global cooling effect due to the eruption of Mount Pinatubo.
Emigration of age-0 chinook salmon (Oncorhynchus tshawytscha) smolts from the upper South Umpqua River basin, Oregon, U.S.A.
Authors: Roper Brett B , Scarnecchia Dennis L
Published: April 2011

Two rotating smolt traps were used through 4 consecutive years to monitor emigrations of age-0 chinook salmon (Oncorhynchus tshawytscha) from two watersheds of the upper South Umpqua River basin, Oregon, U.S.A. The number of wild smolts moving past the mainstem South Umpqua River trap ranged from 26 455 in 1991 to less than 5000 in 1993. The number of wild smolts passing the Jackson Creek trap ranged from 13 345 in 1991 to 0 in 1993. Higher numbers of wild smolts were significantly (P = 0.003) correlated with higher numbers of prespawning adults counted in index reaches the preceding year. Timing of emigration of smolts was found to be significantly related to stream temperature (P < 0.05) and phase of the lunar cycle (P < 0.05) but not related to changes in discharge (P > 0.05). Median emigration dates, which varied over 9 weeks, were earlier when spring water temperatures were higher. On average, two thirds of yearly smolt runs occurred when the moon was either waning or new, even though these moon phases were present only about half of the time. Significantly (P < 0.05) more fish than expected emigrated past both traps when day length was increasing.
Application of an ion-exchange separation technique and thermal ionization mass spectrometry to 226Ra determination in otoliths for radiometric age determination of long-lived fishes
Authors: Andrews Allen H , Coale Kenneth H , Nowicki Jocelyn L , Lundstrom Craig , Palacz Zenon , Burton Erica J , Cailliet Gregor M
Published: April 2011

To improve the accuracy and precision of radiometric age determination using 210Pb:226Ra disequilibria in otoliths of fishes, a technique was developed incorporating an ion-exchange procedure followed by isotope-dilution thermal ionization mass spectrometry (TIMS) to determine 226Ra. This technique counts ionized radium atoms directly; therefore, the uncertainty of the technique is superior to conventional radio-decay dependent techniques. Calcium and barium are major components of the otolith matrix that can interfere with TIMS analysis of radium. To remove these interferants, an ion-exchange separation procedure was developed. This procedure was tested by applying it to otolith samples from three fish species in three separate radiometric ageing studies. The resultant separations and TIMS determinations indicate that the procedure efficiently separates radium from calcium and barium. Measured 226Ra activities for each species were similar to previous radiometric ageing studies, with the exception of one sample. When results were compared with traditional 226Ra determination techniques, radon emanation and α-spectrometry, the separation procedure with isotope-dilution TIMS had significant advantages. Samples over three times smaller than attempted in other studies were processed with decreased uncertainty and processing time.
Estimation of tag reporting rates in agestructured multicomponent fisheries where one component has observers
Authors: Hearn William S , Polacheck Thomas , Pollock Kenneth H , Whitelaw Wade
Published: April 2011

For many tagging experiments, it is vital that fishers find and report all tags to scientists. If not, the tag reporting rate needs to be estimated so that fishing and natural mortality rates can be estimated. One way to estimate this rate is to have one fishery component (e.g., with observers) report every tag found from all fish that it catches. If the numbers of fish caught by all fishery components are also known and the tagged fish are mixed with the population (or subpopulation) being harvested, then one can estimate the reporting rate of underreporting fishery components. This procedure can fail if data are pooled over ages. We obtain maximum likelihood estimators for the reporting rate for each age and (or) each fishery component. We show how to estimate reporting rates if mixing of tagged and untagged fish occurs with some delay. We also obtain overall age-dependent reporting rates, which combine reporting rates from all components of the fishery. Our likelihood is part of an integrated likelihood that allows estimation of age-dependent fishing and natural mortalities in addition to the reporting rates. Our procedures are illustrated with some southern bluefin tuna (Thunnus maccoyii) tagging data.
2,2',4,4',5,5'- and 3,3',4,4',5,5'-Hexachlorobiphenyl pretreatments alter the biliary excretion of a challenge dose of 7,12-[3H]dimethylbenz[a]anthracene in rainbow trout (Oncorhynchus mykiss)
Authors: Foster Eugene P , Curtis Lawrence R
Published: April 2011

This study compared disposition of a polycyclic aromatic hydrocarbon (PAH) in rainbow trout after di-ortho and non-ortho polychlorinated biphenyl (PCH) pretreatments. Four weeks after intraperitoneal (i.p.) injection with 50 or 250 µg of the di-ortho 2,2',4,4',5,5'-hexachlorobiphenyl (2HxCB)·g-1 or 5 or 25 µg of the non-ortho 3,3',4,4',5,5'-hexachlorobiphenyl (3HxCB)·g-1, rainbow trout were i.p. injected with 10 nmol [3H]7,12-dimethylbenz[a]anthracene (DMBA)·g-1. Livers and gallbladders were removed 16 h later. Biliary excretion of [3H]DMBA decreased after i.p. injection of 2HxCB or 3HxCB. In a second experiment, rainbow trout were fed 60 or 220 ng 2HxCB·g fish-1·day-1 or 1.9 or 7.8 ng 3HxCB·g fish-1·day-1 for 4, 8, or 12 weeks. Fish were then i.p. injected with 10 nmol [3H]DMBA·g fish-1. Liver, bile, mesenteric fat, stomach, muscle, kidney, and plasma were sampled 16 h later. Fish fed 220 ng 2HxCB·g fish-1·day-1 for 4 weeks and 60 or 220 ng 2HxCB·g fish-1·day-1 for 8 weeks had greater biliary concentrations of [3H]DMBA than controls. Biliary [3H]DMBA increased for fish fed 7.8 ng 3HxCB·g fish-1·day-1 for 4 weeks. Thus, feeding both di-ortho and non-ortho PCBs transiently stimulated [3H]DMBA biliary excretion. Growth and survival data indicated no overt toxicity of the PCB doses used here via either exposure route. High i.p. doses that inhibited biliary excretion of [3H]DMBA were probably less environmentally relevant than the dietary doses fed here.
Microsatellite evolution in sunfish (Centrarchidae)
Authors: Neff Bryan D , Fu Peng , Gross Mart R
Published: April 2011

We describe 10 microsatellite loci from bluegill (Lepomis macrochirus) and discuss their evolution within the Centrarchidae. All of the loci exhibit Mendelian inheritance and are unlinked. While six loci are conserved within the Centrarchidae (found also in pumpkinseed (Lepomis gibbosus) and largemouth bass (Micropterus salmoides)), four have origins outside the family and two predate it by 65-150 million years. The persistence of these loci in fish may be due to a slow rate of sequence divergence within their flanking sequences, estimated at 0.14-0.83% per million years. We examine the number of alleles, heterozygosity, range, modes, and the frequency of the most common allele and find that a two-phased model (TPM) or an infinite alleles-model (IAM) best describes the results, while a stepwise mutation model (SMM) is rejected. Therefore, population differentiation analyses utilizing these microsatellite loci should consider parameters based on the IAM (e.g., FST) and not the SMM.
Densities of juvenile brown trout (Salmo trutta) in two subarctic rivers: assessing the predictive capability of habitat preference indices
Authors: Mäki-Petäys Aki , Muotka Timo , Huusko Ari
Published: April 2011

We examined the applicability of habitat preference indices for predicting density variations of age-0 brown trout (Salmo trutta) in two rivers in northern Finland. Trout densities in these rivers were monitored for 7 or 8 years. Habitat suitability for trout fry was assessed using summer and winter preference curves for water velocity, depth, and substrate. Substrate suitability indices based on summer preference curves explained 21-74% of the among-site variation in trout densities. The negative effect of high discharge on trout abundance was best predicted by the composite depth × substrate index. Sites with the highest "apparent survival" (density of age-1 trout in year t versus density of age-0 trout in year t - 1) produced high indices when winter substrate curves for age-0 trout were used, indicating high immigration rates to these sites. Our study shows that when preference indices are used for predictive purposes, the mechanisms underlying habitat "bottlenecks" must be known. In boreal areas, winter presents a bottleneck period for juvenile salmonids, and we stress the importance of using winter habitat curves when habitat hydraulic models are applied to areas with severe winter conditions.
Role of copepod-dominated meiofauna in the nitrification process of a cold marine mesocosm
Authors: Parent Serge , Morin Antoine
Published: April 2011

Large populations of copepod-dominated meiofauna are found in the sand filters of the St. Lawrence marine mesocosm at the Montreal Biodome. Experiments were conducted in heterotrophic microcosms to quantify how populations of micro- and meiofaunal organisms affect ammonia oxidation (nitrition) and nitrite oxidation (nitration) using apparent nitrition rate (ANiR) and apparent nitration rate (ANaR) as proxies. ANiR and ANaR were not related to ciliate density. Meiofauna had no effect on ANiR, but a significant relationship between ANaR and meiofaunal biomass was observed, which varied with the particulate organic nitrogen (PON) content of the sediment. The relationship was negative at low PON and positive at high PON. These results suggest a direct negative action by predation on nitrifying bacteria and an indirect positive action by reducing competitors through grazing of heterotroph bacteria. The negative effect of 1 g meiofauna·m-2 at low PON (-20% of ANaR0, i.e., ANaR without meiofauna) is much smaller than its positive effect at high PON (+172 to +571% of ANaR0). Copepod-dominated meiofaunal biomasses less than 0.16 g·m-2 increase two to five times the nitrification rate in heterotrophic habitats rich in PON.
Intraspecific gastropod shell strength variation among north temperate lakes
Authors: Lewis David Bruce , Magnuson John J
Published: April 2011

Defensive morphological traits may vary intraspecifically. Freshwater snail shells are conspicuous defensive structures. In north-central Wisconsin, we investigate whether among-lake differences in shell strength relate to water chemistry or predator abundance and whether shell strength is inducible owing to predation risk from crayfish. Amnicola limosa shells were stronger in lakes with abundant crayfish predators. An experiment and a general understanding of prosobranch evolution suggest that this may result from selection rather than induction. The experiment indicated a weakening of shells of slow-growing A. limosa in the presence of crayfish. This may have resulted from resource depression caused by a strong behavioral response that reduced feeding time. Physa skinneri shell strength was correlated with lake calcium concentrations, and a weak trend with calcium was apparent for Helisoma anceps. Decreased P. skinneri shell strength in low-calcium lakes may result from retention of scarce calcium by the body at the expense of allocation to the shell. Populations of H. anceps differed in rates of shell strength increase with body size, suggesting that rates of shell strength accumulation with ontogeny vary among populations. Shell strength increased more rapidly in lakes with abundant predators than in lakes with few predators.
Effects of iron limitation and aquatic humic substances on the growth ofMicrocystis aeruginosa
Authors: Imai Akio , Fukushima Takehiko , Matsushige Kazuo
Published: April 2011

Aquatic humic substances (AHSs) from the eutrophic Lake Kasumigaura, Japan, significantly inhibited the growth of Microcystis aeruginosa at a concentration level similar to that found in the lake. AHSs were isolated and quantified using XAD-8 resin. The effects of these isolated AHSs on the growth of M. aeruginosa cultures were evaluated in a chemically defined medium. The production of siderophores, iron-specific complexing agents, of M. aeruginosa under iron limitation was also examined. Fulvic acid (the lower molecular size fraction of the AHSs) accounted for more than 85% of AHSs in Lake Kasumigaura. Under iron limitation, M. aeruginosa produced hydroxamate-type siderophores; however, they were not effective in enabling substantial recovery of growth. Microcystis aeruginosa growth was significantly inhibited when fulvic acid was 2 mg dry weight·L-1, similar to the concentration in the lake, even when siderophores were produced. Growth inhibition was probably due to a deficiency of iron caused by iron complexation with the fulvic acid. It was suggested that AHSs play an important role in formation and disappearance of M. aeruginosa blooms in eutrophic lakes.
Stable nitrogen and carbon isotopic composition of seston and sediment in two Adirondack lakes
Authors: Owen J S , Mitchell M J , Michener R H
Published: April 2011

Values of δ15N and δ13C natural abundance in seston were compared in two Adirondack lakes that differed with respect to water column NO3-concentration. Seston δ15N values in Arbutus Lake averaged 2.5 ± 0.18 (mean ± SE) and 2.7 ± 0.15 at 2 and 6 m depth, respectively. NO3-concentrations in Arbutus Lake were generally low (range 0-13 µM) with greatly decreased concentrations during the summer; temporal changes in seston δ15N values and water column NO3-concentrations were inversely correlated. NO3-concentrations in Dart's Lake were higher (range 12.9- 22.4 µM) and the magnitude of the decreased summer NO3-concentration lower. Seston δ15N values in Dart's Lake averaged 1.3 ± 0.12 and 1.1 ± 0.07 at depths of 6 and 14 m, respectively. There was no significant correlation between seston δ15N values and water column NO3-concentration in Dart's Lake. Average seston δ13C values in Arbutus Lake and Dart's Lake were -29.8 and -28.7, respectively. More information about the distribution of stable isotopes for a wide variety of freshwater systems is needed to increase our understanding of the patterns observed in this study.
Multivariate regression relationships between ocean conditions and early marine survival of coho salmon (Oncorhynchus kisutch)
Authors: Ryding Kristen E , Skalski John R
Published: April 2011

Washington State hatcheries have released coded wire tagged coho salmon (Oncorhynchus kisutch) since the early 1970s and have recorded data on the number and ages of adult returns. From these data, we isolated marine survival from release to age 2 using a multinomial model incorporating the multivariate structure of the age-at-return data. Only hatcheries on or near the coast were used in the analysis in order to isolate marine effects. Using models to explore linear and curvilinear relationships, early marine survival was regressed against environmental covariates of sea surface temperature (SST), coastal upwelling, and the date of spring transitions. With hatcheries serving as replicates, curvilinear relationships were found between survival and both June SST and the date of spring transition. Maximum survival occurred for a June SST of 13.45°C and for a spring transition date around April 2. The regression results support the idea of optimal environmental conditions for coho salmon survival and may help fisheries managers better understand the dynamics of early marine survival of salmonids.
Migration strategies of young fishes under temporal constraints: the effect of size-dependent overwinter mortality
Authors: Schindler Daniel E
Published: April 2011

Habitat selection by fishes involves balancing the benefits of foraging opportunities and the risk of predation. Size-dependent overwinter mortality imposes a time constraint on behavioral programs of juvenile fishes: individuals must achieve a sufficient size by the end of the growing season to survive. I developed a dynamic optimization model to evaluate how severity of size-dependent overwinter mortality alters habitat use by minnows. The littoral zone was the safest habitat with respect to predation. In lakes where zooplankton exhibit diel vertical migration, fish migrate to the pelagic at night and return to the littoral during the day to maximize foraging rates. Model results demonstrated that size-dependent overwinter mortality should lead to development of more pronounced predation risk-taking by fishes in lakes with severe winters. Individuals are predicted to initiate diel littoral-pelagic migrations at smaller sizes as winter severity increases or as hatch date within a season increases. This analysis suggests that the time constraint imposed by size-selective overwinter mortality has important consequences for life history strategies of juvenile fishes. The effects of time constraints on behavior are expected to be especially important near the high latitudinal limits of a species' geographic distribution.
Freshwater habitat of Atlantic salmon (Salmo salar)
Authors: Bardonnet Agnès , Baglinière Jean-Luc
Published: April 2011

This perspective summarizes our knowledge of the freshwater habitat of Atlantic salmon (Salmo salar). The article is organized by life stage and identifies areas where more research is needed. For example, little is known of the kelt and presmolt life stages despite their importance in stock maintenance. We also believe that further investigation is required to assess the relevance of variables currently used to characterize habitat and that more attention should be focussed on adult and embryo-larva habitat requirements. We also discuss the fact that the majority of research is directed at habitat at the micro (i.e., immediate area around the fish) and macro scales (area of the geomorphological unit), while the influence of habitat at higher spatial scales should also be considered.
Exposure to ultraviolet radiation in aquatic ecosystems: estimates of mixing rate in Lake Ontario and the St. Lawrence River
Authors: Scully Norman M , Vincent Warwick F , Lean David RS
Published: April 2011

Vertical eddy diffusion coefficients (Kz) were determined for the surface waters at several sites in Lake Ontario and along the Upper St. Lawrence River using the water column distribution patterns of hydrogen peroxide. Values of Kzranged from 0.45 × 10-3to 23 × 10-3m2·s-1in Lake Ontario and from 0.75 × 10-3to 2.1 × 10-3m2·s-1along the St. Lawrence River. The residence time for bacterioplankton and phytoplankton in the surface waters was then determined from the Kzvalues and incorporated into a spectral model to determine the continuous biologically effective exposure to ultraviolet radiation (E*UVR). The values of E*UVRfor stations where the temperature fine structure profiles indicated near-surface warming (diurnal thermocline formation) were higher (149.1 J·m-2) than at stations with isothermal surface waters (3.0 J·m-2). Model calculations for two contrasting bays of a lake underscored the dominant role of diurnal thermocline formation in increasing the duration of exposure to continuous damaging ultraviolet radiation exposure. The E*UVRvalue for the near-surface bacterioplankton in a humic stained bay was higher (219.2 J·m-2) than in a larger bay with lower concentrations of chromophoric dissolved organic matter (47.83 J·m-2).
Stock-recruitment relationships for life cycles that exhibit concurrent density dependence
Authors: Bjorkstedt Eric P
Published: April 2011

This study provides theoretical stock-recruitment relationships for life cycles in which multiple, density-dependent mechanisms stemming from different periods during the life cycle act concurrently on a single demographic transition. Using graphical examples and analytical derivations, it is demonstrated that overcompensatory density dependence emerges from such life cycles despite the initial assumption that density-dependent mechanisms follow simple compensatory Beverton-Holt dynamics. These results indicate that concurrent demographic effects of temporally distinct density-dependent mechanisms provide a biologically plausible basis for empirically derived, three-parameter stock-recruitment models. This theory is inspired by, and may be most applicable to, spawner-recruit relationships in anadromous salmonids but may also inform analysis of stock and recruitment data for other taxa that putatively compete for both food and spawning space. Application of this theory will require the estimation of additional parameters from stock-recruitment data. Such parameters, however, have clear biological meaning and, at least theoretically, are accessible to empirical measurement. Stock-recruitment relationships analogous to those presented here may therefore facilitate the construction of models that incorporate independent empirical data and environmental covariates for populations that are currently better described by phenomenological equations and represent an important step towards models that incorporate spatial structure in populations.
Gene-centromere mapping of 312 loci in pink salmon by half-tetrad analysis
Authors: Lindner K R , Seeb J E , Habicht C , Knudsen K L , Kretschmer E , Reedy D J , Spruell P , Allendorf F W
Published: April 2011

We estimated recombination rates between 312 loci and their centromeres in gynogenetic diploid pink salmon (Oncorhynchus gorbuscha) that we produced by initiating development with irradiated sperm and blocking the maternal second meiotic division. Amplified fragment length polymorphisms (AFLPs) were significantly more centromeric than loci identified by three other techniques (allozymes, microsatellites, and PCR using primer sequences from interspersed nuclear elements). The near absence of AFLPs in distal regions could limit their utility in constructing linkage maps. A large proportion of loci had frequency of second division segregation (y) values approaching 1.0, indicating near complete crossover interference on many chromosome arms. As predicted from models of chromosomal evolution in salmonids based upon results with allozyme loci, all duplicated microsatellite loci that shared alleles (isoloci) had y values of nearly 1.0.Key words: meiosis, AFLP, microsatellites, isoloci, Oncorhynchus gorbuscha.
Maximum likelihood vs. minimum chi-square-A general comparison with applications to the estimation of recombination fractions in two-point linkage analysis
Authors: Hühn M
Published: April 2011

Some relationships between the estimates of recombination fraction in two-point linkage analysis obtained by maximum likelihood, minimum chi-square, and general least squares are derived. These theoretical results are based on an approximation for the multinomial distribution. Applications (theoretical and experimental) with RFLP (restriction fragment length polymorphism) markers for a segregating F2 population are given. The minimum chi-square estimate is slightly larger than the maximum likelihood estimate. For applications, however, both estimates must be considered to be approximately equal. The least squares estimates are slightly different (larger or smaller) from these estimates.Key words: linkage analysis, recombination fraction, maximum likelihood, minimum chi-square, general least squares.
Nucleotypic effects without nuclei: Genome size and erythrocyte size in mammals
Authors: Gregory T Ryan
Published: April 2011

Previously reported haploid genome sizes (C-values) and erythrocyte sizes (measured as mean dry diameters) were compared for 67 species of mammals representing 31 families and 16 orders. Measurements on erythrocytes of four species of bats were also included in the study. Erythrocyte size was significantly positively correlated with genome size at each of the specific, generic, familial, and ordinal levels, with the relationship becoming much stronger following the exclusion of the order Artiodactyla, a group unique among mammals in terms of red blood cell morphology. Physiologically, these results are relevant in light of the known relationship between C-value and mass-corrected metabolic rate in homeotherms. In evolutionary terms, they provide insights into the constraints on genome expansion among mammals and are therefore of interest in attempts to solve the long-standing C-value enigma (also known as the C-value paradox).Key words: cell size, C-value paradox, DNA content, evolution, genome size.
A genetic map of cucumber composed of RAPDs, RFLPs, AFLPs, and loci conditioning resistance to papaya ringspot and zucchini yellow mosaic viruses
Authors: Park Young Hoon , Sensoy Suat , Wye Crispin , Antonise Rudie , Peleman Johan , Havey Michael J
Published: April 2011

The watermelon strain of papaya ringspot virus (PRSV-W) and zucchini yellow mosaic virus (ZYMV) are potyviruses that cause significant disease losses in cucumber. Resistances have been identified primarily in exotic germplasm that require transfer to elite cultivated backgrounds. To select more efficiently for virus resistances, we identified molecular markers tightly linked to PRSV-W and ZYMV resistances in cucumber. We generated F6recombinant inbred lines (RILs) from a cross between Cucumis sativus L. 'Straight 8' and a line from 'Taichung Mou Gua', TMG1 (susceptible and resistant, respectively, to both viruses), and studied the segregations of amplified fragment length polymorphism (AFLP) markers, randomly amplified polymorphic DNAs (RAPDs), restriction fragment length polymorphisms (RFLPs), and resistances to PRSV-W and ZYMV. A 353-point map of cucumber was generated, delineating 12 linkage groups at LOD 3.5. Linkage arrangements among RFLPs were consistent with previously published maps; however linkages among RAPDs in our map did not agree with a previously published map. Resistances to PRSV-W and ZYMV were tightly linked (2.2 cM) and mapped to the end of one linkage group. One AFLP cosegregated with resistance to ZYMV.Key words: amplified fragment length polymorphism, randomly amplified polymorphic DNA, restriction fragment length polymorphism, virus resistance.
Physical localization of single-copy sequences on pachytene chromosomes in maize (Zea maysL.) by chromosome in situ suppression hybridization
Authors: Sadder Monther T , Ponelies Norbert , Born Ute , Weber Gerd
Published: April 2011

A new approach for locating single-copy DNA sequences on pachytene chromosomes of maize (Zea mays L.) was developed. A cosmid clone with homologous sequences to a molecular marker (umc105a) linked to a quantitative trait locus (QTL) for resistance against sugarcane borer (SCB) was physically mapped by fluorescence in situ hybridization (FISH) to the short arm of chromosome 9. The marker umc105a was genetically placed in the centromeric region. To suppress signals generated by maize repetitive DNA, competitive in situ suppression (CISS) hybridization was necessary to obtain specific signals from umc105a. A centromere specific DNA probe (CentC) was used in a double-labeling technique as a reference marker. Fluorescence signals generated by umc105a cosmid and CentC were specific and highly reproducible. Thus the single-copy DNA sequence of umc105a was physically localized on the short arm of chromosome 9 near the telomere. This is the first report of physical localization of single-copy DNA sequence by CISS hybridization to a maize pachytene chromosome.Key words: fluorescence in situ hybridization, maize, pachytene chromosome, single-copy sequence, CISS hybridization.
Genomic in situ hybridization analysis of a trigenomic hybrid involvingSolanumandLycopersiconspecies
Authors: Haider Ali S N , Huigen Dirk Jan , Ramanna M S , Jacobsen Evert , Visser Richard GF
Published: April 2011

A 4x potato (+) tomato fusion hybrid (2n = 4x = 48) was successfully backcrossed with a diploid Lycopersicon pennellii (2n = 2x = 24). Genomic in situ hybridization (GISH) on somatic and meiotic chromosomes confirmed that the progenies were triploids (2n = 3x = 36) and possessed three different genomes: potato, tomato, and L. pennellii. Therefore, they have been called trigenomic hybrids. Total genomic probes of both Lycopersicon species were found to hybridize mutually, whereas the potato genome was clearly differentiated. During metaphase I, bivalents were formed predominantly between tomato and L. pennellii chromosomes and the univalents of potato chromosomes were most common. Trivalents in all cases included homoeologous chromosomes of potato, tomato, and L. pennellii. However, the triploids were totally sterile as determined from extensive crossing. On chromosome doubling of triploids by shoot regeneration from callus, hexaploids (2n = 6x = 72) were obtained. Despite exhibiting clear allohexaploid behaviour by forming 36 bivalents at meiosis, these were also completely sterile like their triploid counterparts. In spite of this drawback, the prospects of chromosome pairing between potato L. pennellii and Solanum genomes does open the possibilities for bringing the two genera close.Key words: trigenomic triploids, GISH, bridge species, potato (+) tomato fusion hybrids.