bluuebunny/crossref_metadata_2025 huggingface dataset:
A stock survey technique using the time to capture individual fish on longlines
Authors: Somerton David A. , Kikkawa Bert S.
Published: August 2008

Longline catches per unit of effort (CPUE) from research surveys are often assumed to vary in proportion to fish abundance. This assumption, however, may be invalid if the abundance of the target species is high enough to saturate the gear or if the abundance of nontarget species is high enough to exclude the target species from capture. We examine a new approach to surveying fish populations with longlines that is based on time-to-capture data measured with small, fish-activated timing devices attached to every hook. A new measure of relative abundance, λ, is developed that is immune to the effects of gear saturation and interspecific competition for hooks. Two estimators of λ are compared by using capture-time data collected during summer 1987–1991 for pelagic armorhead (Pseudopentaceros wheeleri). Both estimators are shown to be unbiased if the underlying assumptions are true and fairly robust to the observed departures from these assumptions.
Historical versus recent levels of organochlorine contaminants in lamprey larvae of the St. Lawrence River basin, Québec
Authors: Renaud Claud B. , Kaiser Klaus L. E. , Comba Michael E.
Published: August 2008

This study shows that persistent organochlorine contaminants, including PCBs, reached higher concentrations in lamprey of the St. Lawrence River basin 40 years ago. A comparison was made of the concentrations of 22 organochlorine pesticides and 93 polychlorinated biphenyl (PCB) congeners in formalin-preserved lamprey ammocoetes collected between 1947–1950 and in 1990 in the St-François and Ste-Anne rivers, St. Lawrence River basin, Québec. Eight pesticides (β-BHC, α-Chlordane, γ-Chlordane, p,p′-DDD, o,p′-DDE, p,p′-DDE, p,p′-DDT, and Heptachlor) reached higher concentrations in the earlier period, with Mirex being the only pesticide found in higher concentrations in 1990. Seventeen PCB congeners (24(27), 28, 98(84), 101, 110(77), 128, 129, 141, 149, 151, 158, 174, 177, 180, 183, 187(182), and 198) had higher concentrations in the 1947–1950 period compared with 1990. A significant inverse relationship was found between the concentration of the various PCB congeners and sampling date. The concentrations of DDT have decreased significantly, while its metabolites, DDD and DDE, have increased significantly over the last 40 years.
Effects of late-season catch and release angling on anaerobic metabolism, acid–base status, survival, and gamete viability in wild Atlantic salmon (Salmo salar)
Authors: Booth Richard K. , Kieffer James D. , Tufts Bruce L. , Davidson Kevin , Bielak Alex T.
Published: August 2008

The effects of catch and release angling on muscle physiology, survival and gamete viability were examined in wild Atlantic salmon (Salmo salar), just prior to spawning. Lactate in the white muscle increased to 37.4 μmol∙g−1after angling and recovered within 4 h. Muscle pH decreased from 7.46 at rest to 6.80 following angling, but returned to resting levels within 2 h. White muscle concentrations of PCr, ATP, and glycogen were depleted by 74, 46, and 73%, respectively, following angling. ATP and PCr returned to resting levels within 2 h, but glycogen did not recover until 12 h. The absence of significant changes in blood glucose indicated that the stress response was minimal in salmon angled under these conditions (6 °C). There were also no mortalities among 20 salmon that were angled and transported to the hatchery. Multi-sea-winter (MSW) salmon (> 63 cm) required a longer period to angle to exhaustion than grilse (< 63 cm), but the physiological disturbance was less in MSW salmon. The survival of eggs from angled and nonangled salmon was 98 and 97%, respectively. Together, these results support the strategy of a late-season catch and release fishery for Atlantic salmon.
Choosing fisheries harvest policies: when does uncertainty matter?
Authors: Frederick Shane W. , Peterman Randall M.
Published: August 2008

Fisheries harvest policies are formulated under uncertainty because estimates of stock abundance and biological parameters are imprecise. However, allowable harvests are often based solely on point estimates of these quantities, essentially ignoring uncertainty. Some fishery scientists have advocated adjusting harvest levels downward to account for uncertainty, but few formal methods have been developed to determine how large these "uncertainty adjustments" should be. We describe an age-structured simulation model that explicitly incorporated uncertainty in parameters of the stock–recruitment relationship, errors in abundance estimates, and year-to-year variability in recruitment and calculated which uncertainty adjustment was optimal in terms of expected discounted yield. The optimal adjustment varied considerably, depending on the stock and harvest policy simulated. The increase in expected value from incorporating the adjustment into the harvest policy was usually small, except when we modeled a biological "threshold", where overharvests could lead to an irreversible stock collapse. Therefore, while our analysis suggests that basing harvest decisions solely on the best point estimates may often be an approximately optimal strategy, it also indicates that large adjustments may sometimes be appropriate. Consequently, fishery managers should avoid making arbitrary adjustments for uncertainty, and instead derive the optimal adjustment for each situation.
Wind-induced upwelling along the west coast of North America, 1899–1988
Authors: Hsieh William W. , Ware Daniel M. , Thomson Richard E.
Published: August 2008

Alongshore geostrophic wind stresses (AWS) were used as an "index" of wind-induced coastal upwelling/downwelling for eight coastal stations from Baja California to Alaska for 1899–1988. For winters since around 1940, downwelling has intensified along Alaska and northern British Columbia, while upwelling has increased along Baja California. El Niño events induced strong winter coastal downwelling poleward of 40°N. During summer, upwelling has increased since around 1940 along southern British Columbia to Baja California, while from 1899 to 1940, upwelling declined along southern California to Baja California. Empirical orthogonal function analysis of the AWS showed that the first mode consisted of the AWS at the eight stations all varying in-phase, while the second mode had the northern four stations out-of-phase with the southern four stations. Off southern British Columbia, correlations between coastal sea level and AWS and between sea surface temperature and AWS were both strong during winter but insignificant during summer. In contrast, correlation between salinity and alongshore wind stress was insignificant during fall and winter, but strong during spring and moderate during summer. Summer AWS was positively correlated with both the fatness of sardine and the condition factor of herring off British Columbia.
Estimation of in-river fish passage using a combination of transect and stationary hydroacoustic sampling
Authors: Banneheka Sarath G. , Routledge Richard D. , Guthrie Ian C. , Woodey James C.
Published: August 2008

We describe a hydroacoustic technique that uses both transect and stationary sampling to estimate numbers of fish migrating in a river. The technique includes refinements and additions to one developed by the International Pacific Salmon Fisheries Commission to estimate sockeye (Oncorhynchus nerka) and pink salmon (Oncorhynchus gorbuscha) migrations in the Fraser River. The estimator is independent of the actual shape of the effective acoustic beam and the distribution of target strengths when the same hydroacoustic equipment and settings are used for both types of soundings. Thus, the method shares with the duration-in-beam method the advantages that equipment calibration requirements are minimal and that estimates remain valid when fish sizes vary over a wide range. We also provide formulae for the variance of the abundance estimate and illustrate the methods with example calculations of daily fish passage in the Fraser River at Mission, British Columbia. A correction procedure is proposed to compensate for bias arising from violation of the assumption that fish speed is negligible relative to boat speed.
Differences in otolith microstructure between hatchery-reared and wild Chinook salmon (Oncorhynchus tshawytscha)
Authors: Zhang Z. , Beamish R. J. , Riddell B. E.
Published: August 2008

Otolith microstructure exhibited some characteristic differences between hatchery-reared and wild chinook salmon (Oncorhynchus tshawytscha) from the Cowichan River. Daily growth increments that formed in the otoliths of the hatchery-reared chinook salmon after exogenous feeding were more regular in width and contrast than those in the otoliths of wild chinook salmon. In addition, otoliths from hatchery-reared individuals frequently produced a check when the fish were released from the hatchery. Eighty-nine percent of a sample of 67 chinook smolts that had been coded-wire tagged in hatcheries and later captured in the Strait of Georgia were correctly identified as originating from hatcheries based on otolith microstructure. These tagged fish originated from at least 17 different hatcheries, indicating that the method could be used to identify chinook salmon originating from other hatcheries.
Use of the lateral line in particulate feeding in the dark by juvenile alewife (Alosa pseudoharengus)
Authors: Janssen John , Jones Warren R. , Whang Audrey , Oshel Philip E.
Published: August 2008

The alewife (Alosa pseudoharengus) is an obligate planktivore which uses a variety of methods for capturing zooplankton. Alewife eat Mysis relicta, especially larger individuals, at night during a vertical migration by both predator and prey. We proposed and tested the hypothesis that alewife use the lateral line to sense prey and feed particulately (single prey at a time) in the dark. We used Daphnia magna and Artemia salina adults as prey. Prey densities were such that they did not elicit filter feeding. Observations using infrared video showed that alewife captured individual prey and bit at a vibrating inert bead. We concluded that under appropriate conditions, alewife were size selective and that streptomycin (which blocks the lateral line sensory cells) eliminated this feeding behavior.
Removal of algae by the zebra mussel (Dreissena polymorpha) population in western Lake Erie: a bioenergetics approach
Authors: Madenjian Charles P.
Published: August 2008

A bioenergetics model for growth of a zebra mussel (Dreissena polymorpha) individual was verified with observations on zebra mussel growth in western Lake Erie. The bioenergetics model was then applied to the zebra mussel population in the western basin of Lake Erie to estimate the removal of phytoplankton by mussels. According to the modeling results, the zebra mussel population consumed 5.0 million tonnes of phytoplankton, while 1.4 million tonnes of phytoplankton was deposited in pseudofeces from the mussels. Thus, a total of 6.4 ± 2.4 million tonnes of phytoplankton was removed from the water column by zebra mussel in western Lake Erie during 1990. Primary production was estimated to be 24.8 million tonnes; therefore, zebra mussel removed the equivalent of 26 ± 10% of the primary production for western Lake Erie.
Age determination and growth of orange roughy (Hoplostethus atlanticus): a comparison of annulus counts with radiometric ageing
Authors: Smith David C. , Robertson Simon G. , Fenton Gwen E. , Short Stephen A.
Published: August 2008

Ages of orange roughy (Hoplostethus atlanticus) determined by two methods (counting annuli on the surface of whole and in longitudinally sectioned otoliths) were similar up to maturity. Beyond maturity, age estimates from sectioned otoliths exceeded those from whole otoliths. Maximum recorded age was 125 years for an individual 41 cm standard length (SL), and age at maturity was estimated to be 25 years (30–32 cm SL). These are consistent with ages estimated previously by radiometric methods. Results demonstrated a two-stage linear relationship between otolith weight and age that confirmed the two-stage otolith mass growth model previously used in radiometric ageing. However, in the radiometric analyses the reduction in otolith growth was arbitrarily estimated at 45% of the immature rate whereas annuli data demonstrated a reduction after maturity to 62% of the immature rate. The new estimates of otolith mass growth rate were incorporated into the radiometric data and ages recalculated, which reduced age estimates for 38–40 cm SL fish from 77–149 to 59–101 years. The radiometric data were also recalculated using only the percentage reduction in otolith growth after maturity, giving the radiometric age of 125 ± 9 years for the oldest fish.
Relation of algal biovolume to chlorophyll a in selected lakes and wetlands in the north-central United States
Authors: LaBaugh James W.
Published: August 2008

Algal chlorophyll a is commonly used as a surrogate for algal biomass. Data from three lakes in western Nebraska, five wetlands in north-central North Dakota, and two lakes in north-central Minnesota represented a range in algal biovolume of over four orders of magnitude and a range in chlorophyll a from less than 1 to 380 mg∙m−3. Analysis of these data revealed that there was a linear relation, log10 algal biovolume = 5.99 + 0.09 chlorophyll a (r2 = 0.72), for cases in which median values of chlorophyll a for open-water periods were less than 20 mg∙m−3. There was no linear relation in cases in which median chlorophyll a concentrations were larger than 20 mg∙m−3 for open-water periods, an occurrence found only in shallow prairies lakes and wetlands for years in which light penetration was the least.
Population dynamics, growth, and production of the Asiatic clam,Corbicula fluminea, in a blackwater river
Authors: Stites David L. , Benke Arthur C. , Gillespie David M.
Published: August 2008

In a sixth-order blackwater river (Lower Coastal Plain of Georgia, USA), the average life span of Corbicula fluminea (Müller) was 3–4 years, with shell length reaching only 18–20 mm by the third year. Mean density was usually < 200/m2over a 43-month period, but > 1000/m2in population centers. Mean biomass (dry mass of soft tissue) was consistently 1–5 g/m2, but averaged 11 g/m2in population centers. Biomass growth rates of clams reared in situ were highest in late spring and were inversely related to clam mass. Production ranged from 0.18 g∙m−2∙year−1at a main-channel site to 3.2 in a backwater and averaged 1.2–1.7 for 2 consecutive years. In population centers, production reached 9–23 g∙m−2∙year−1. Production was highest in spring and fell to zero in winter when growth ceased. Annual production/biomass values were about 4–8 for first-year individuals, but ranged from 0.51 to 1.78 overall. Individual size, growth rates, and production all indicated that this blackwater river was a stressful environment for Corbicula, probably due to low alkalinity (< 30 mg/L as CaCO3). Unlike its effect in many other systems, the clam appears to play a minor role in the trophic dynamics of this river.
Responses of cytochrome P4501A in freshwater fish exposed to bleached kraft mill effluent in experimental stream channels
Authors: Bankey Laura A. , Veld Peter A. Van , Borton Dennis L. , LaFleur Larry , Stegeman John J.
Published: August 2008

Cytochrome P4501A induction was used to evaluate exposure of fish to bleached kraft mill effluent in experimental stream channels. Immunodetectable P4501A and associated ethoxyresorufin-O-deethylase (EROD) activity were elevated in largemouth bass (Micropterus salmoides) and channel catfish (Ictalurus punctatus) throughout 263 days of exposure to 8% and 4% effluent from a mill that used 70% chlorine dioxide substitution for chlorine in the pulp bleaching process. In largemouth bass, P4501A was elevated as high as 55-fold over control fish. Large temporal and species variations were observed in enzyme levels and activity. Levels of chlorinated organic compounds present in effluent also varied throughout exposures. However, there was no apparent relationship between P4501A and any of those compounds measured. P4501A and EROD in channel catfish declined to control levels within seven days after transfer of fish to clean water or after terminating introduction of effluent into the channels. In another exposure, induction was observed in largemouth bass at 4 and 12% effluent after the mill began using oxygen in the delignification process and 100% substitution of chlorine dioxide for chlorine.
Aerial exposure tolerance off zebra and quagga mussels (Bivalvia: Dreissenidae): implications for overland dispersal
Authors: Ricciardi Anthony , Serrouya Robert , Whoriskey Frederick G.
Published: August 2008

We examined the effects of ambient temperature (10, 20, and 30 °C) and relative humidity (10, 50, and 95% RH) on the aerial exposure tolerance of adult zebra mussel (Dreissena polymorpha) and quagga mussel (D. bugensis) collected from the St. Lawrence River. Survivorship of mussels in air significantly increased with increasing RH, decreasing temperature, and increasing mussel size. At 20 °C and 50% RH (early temperate summer conditions), large (21–28 mm) D. polymorpha survived more than 5 days exposure, whereas small (10–18 mm) D. polymorpha survived 1–3 days. Seventy-three percent of large D. polymorpha and 10% of small D. polymorpha survived 10 days exposure at conditions considered optimal for survivorship (10 °C and 95% RH). Survivorship of D. bugensis was tested at 20 °C and was 15–100% lower than that of D. polymorpha at all RH levels combined with exposures less than 5 days. Dreissena bugensis also suffered significantly higher percent weight losses because of desiccation than D. polymorpha. The differences in the desiccation tolerance of zebra and quagga mussels reflect their relative depth distribution in lakes. Our results suggest that, given temperate summer conditions, adult Dreissena may survive overland transport (e.g., on small trailered boats) to any location within 3–5 days' drive of infested waterbodies.
Upper thermal limits on the oceanic distribution of Pacific salmon (Oncorhynchus spp.) in the spring
Authors: Welch D. W. , Chigirinsky A. I. , Ishida Y.
Published: August 2008

Pacific salmon are normally thought to be distributed throughout the Subarctic Pacific, an area where they form the dominant fish fauna. We use a series of generalized additive models to show that salmon exhibit a sharp step-function response to temperature in the oceanic eastern north Pacific in spring. The critical temperature defining the southern boundary varied by species: 10.4 °C for pink and chum salmon, 9.4 °C for coho salmon, and 8.9 °C for sockeye salmon. These thermal limits occur well to the north of the southern boundary of the Transition Zone, at widely separated geographic positions within the Subarctic Domain, and at temperatures much lower than the lethal upper limit for each species. The sharp decline in abundance with temperature, and the remarkably low temperatures at which the response occurs, suggests that thermal barriers form an effective limit to the offshore distribution of salmon in spring, and can limit the distribution of Pacific salmon to a relatively small area of the Subarctic Pacific. The strength of this response is presumably the direct result of strong evolutionary selection. Future temperature changes in the North Pacific could therefore have a direct impact on the production dynamics of Pacific salmon.
Homing behavior and vertical movements of four species of Pacific salmon (Oncorhynchus spp.) in the central Bering Sea
Authors: Ogura Miki , Ishida Yukimasa
Published: August 2008

Four sockeye salmon (Oncorhynchus nerka), two chum salmon (O. keta), three pink salmon (O. gorbuscha), and four Chinook salmon (O. tshawytscha) with depth-sensing ultrasonic transmitters were tracked in the central Bering Sea to examine migration in the open sea. Ground speeds of maturing sockeye, chum, and pink salmon were at 0.54–0.66 m/s (0.88–1.17 fork lengths/s). Chinook salmon, probably immature fish, moved more slowly (0.34 m/s). Maturing individuals moved in particular directions and maintained their ground speeds and directions during day and night. The results also suggested that salmon had a compass orientation ability functioning without celestial information. Sockeye, chum, and pink salmon showed strong surface preferences but chinook salmon swam deeper (30–35 m) than did the other species.
Spawning energetics of Arctic cod (Boreogadus saida) in relation to seasonal development of the ovary and plasma sex steroid levels
Authors: Hop Haakon , Trudeau Vance L. , Graham Mark
Published: August 2008

Gonadal development in Arctic cod starts in August in high Arctic Canada. Male gonads develop at a faster rate than female gonads initially, and reach maximum size about two months prior to females. Under laboratory conditions (at 1.0 °C), female Arctic cod became ripe and started to spawn in mid-February, which concurred with field observations. Ripe gonad weight increased with body size; mean gonadosomatic index (GSI) of ripe females was 47.7%, and potential fecundity averaged 26 500 eggs. At the time when ripe females started to spawn, some females were still unripe (GSI = 20.2%). Their eggs were not hydrated, and these fish had significantly higher levels of sex steroids (estradiol, 11-ketotestosterone, and testosterone) in their blood than ripe fish. Arctic cod are repeat spawners, at least under laboratory conditions, in spite of the large amount of energy allocated to reproduction (306 kJ lost from liver and muscle during gonadal development and 125 kJ as eggs during spawning). A high energy investment into reproduction, for a fish that matures at an early age, may be balanced against high predation rates on this species during the open-water season in the Canadian high Arctic.
Impacts of zebra mussel on walleye (Stizostedion vitreum) reproduction in western Lake Erie
Authors: Fitzsimons J. D. , Leach J. H. , Nepszy S. J. , Cairns V. W.
Published: August 2008

A walleye spawning shoal (Sunken Chicken Reef) in western Lake Erie was sampled during the spring of 1990 and 1991 to assess the abundance of the zebra mussel Dreissena polymorpha and to determine its impact on walleye reproduction. Mussel abundance ranged from 76 500/m2 at 1.5 m depth to 344 300/m2 at 4.5 m depth at the shoal (1990). Despite the almost total coverage of spawning beds walleye continued to spawn at the shoal, with no apparent effect of the mussels on egg deposition, egg viability, and interstitial dissolved oxygen. Although preinvasion data for walleye egg deposition are not comparable to data from this study, deposition appears adequate based on good indices of recruitment of young-of-the-year walleye derived from resource agency trawling during 1990 and 1991. Thus there appears to have been no adverse impacts of zebra mussel on walleye reproduction in western Lake Erie during 1990 and 1991.
Seasonal variation in water chemistry over a bog-rich fen gradient in Continental Western Canada
Authors: Vitt Dale H. , Bayley Suzanne E. , Jin Tai-Long
Published: August 2008

Surface and subsurface (0.5, 1.0, and 1.5 m depths) water was sampled weekly in 1989 and biweekly in 1990 during the ice-free season along a bog-rich fen gradient in central Alberta. Acidity–alkalinity were most closely related to peatland type and were the most useful parameters for characterizing peatlands. Potassium, nitrogen, and phosphorus concentrations were more related to season, year, or peatland–year interactions and cannot be used to categorize the bog–fen gradient. Hydrogen ion, ammonium, alkalinity, and corrected conductivity were relatively constant throughout the ice-free season, while total metal ions (Al, Fe, Mn, and Zn), base cations (Ca2+, Mg2+, Na+, K+), nitrate, and components of phosphorus fluctuated seasonally. Nitrate remained constant with depth in all peatland types, whereas ammonium increased with depth. Relationships of surface water chemistry to pH for all sites showed three patterns: a positive and highly significant correlation with little seasonal variation within peatland types (base cations, alkalinity, and corrected conductivity); less significant correlation with strong seasonal variation within peatland types (N and P); and a general negative and highly significant correlation with some seasonal variation in peatland types (metals and S). Water temperatures increased along the bog-rich fen gradient.
Effects of water chemistry and temperature on radiocesium dynamics in rainbow trout,Oncorhynchus mykiss
Authors: Cocchio L. A. , Beamish F. W. H. , Rodgers D. W.
Published: August 2008

We determined the effects of temperature (8 and 16 °C) and water concentrations of potassium (0.01–3.4 mmol/L), sodium (0.4–3.0 mmol/L), and calcium (0.3–2.9 mmol/L) on the dynamics of137Cs in rainbow trout (Oncorhynchus mykiss). Trout were fed food labelled with137Cs, and137Cs retention was monitored by whole body gamma counting (70 d). Assimilation of137Cs did not vary significantly over the range of concentrations of K+, Na+, and Ca2+employed, with an average value of 65 ± 3% (mean ± SE). The elimination of137Cs was significantly affected by K+, with the elimination rate constant of trout held at the highest K+concentration (0.021 ± 0.001 d−1at K+of 3.4 mmol/L) roughly double that observed in trout at lower K+(0.011 ± 0.001 d−1at K+≤ 0.3 mmol/L). Elimination of137Cs was also significantly affected by temperature, with the increase in elimination rate over the range of 8 and 16 °C corresponding to a Q10of ≈1.7. Although the effect of K+on accumulation of137Cs in trout was statistically significant, this effect, by itself, can explain only a small fraction of the broad range of137Cs concentration ratios reported for wild fish.
Predator avoidance in naive and experienced juvenile chinook and coho salmon
Authors: Healey M. C. , Reinhardt U.
Published: August 2008

We compared the vulnerability of naive and experienced coho and chinook salmon to predation by rainbow trout and related these findings to observations of the specific behaviour of each species during an encounter with the predator. Naive chinook were significantly less vulnerable to capture than naive coho in an open field encounter but there was no difference in capture rate of experienced coho and chinook. In videotaped encounters we found that coho and chinook behaved in significantly different ways when attacked by the predator, both when naive and when experienced. Our results suggest that predator avoidance strategies are highly species specific, that both species adjusted their behaviour after experience with the predator, and that the behavioural changes adopted by coho improved their ability to avoid the predator in an open field but those adopted by chinook did not. Considerable recent research has explored the willingness of different species, sexes, or life stages to risk exposure to a predator to obtain some reward (usually food). Our results further suggest that published experiments that purport to demonstrate differences in risk taking among types of prey may, instead, demonstrate differences in predator avoidance capability.
Differences in the onset of salinity tolerance between juvenile chinook salmon from two coastal Oregon river systems
Authors: Kreeger Karen Young
Published: August 2008

Trask River juvenile chinook salmon (Oncorhynchus tshawytscha) rear in an estuarine environment, whereas Rogue River juveniles rear in a riverine environment, suggesting these populations differ in the ontogeny of smolting physiology. To study differences in the onset of salinity tolerance between these populations, I reared individuals from the Trask and Rogue rivers (Oregon) in a common environment and monitored changes in their physiology throughout their first 5–6 months. Trask fish were able to tolerate oceanic salinities at a smaller size and younger age than Rogue juveniles. Fifty days post-first feeding and at < 2 g 65% of Trask juveniles survived in 32 ppt compared with 40% of Rogue juveniles. Trask juveniles also maintained their water balance in 32 ppt seawater relative to freshwater at 50 days post-first feeding compared with 80 days for Rogue juveniles. Plasma sodium concentration indicated that both populations did not competently osmoregulate until approximately 108 days post-first feeding. Although the minimum size and age of salinity tolerance depended on which indicator of tolerance was chosen for study, physiological parameters suggested interpopulational differences in the timing of the onset of salinity tolerance.
Critical examination of stable isotope analysis as a means for tracing carbon pathways in stream ecosystems
Authors: France Robert
Published: August 2008

Existing data conflict as to the capability of stable isotope analysis (SIA) for distinguishing carbon pathways in stream ecosystems. I compiled 803 published measurements of δ13C for allochthonous litter and both lotic attached algae and consumers to search for general patterns that transcend individual studies. Half of the fishes and 30% of the invertebrates exhibited δ13C values outside the range that could be ascribed to allochthonous litter. The enormous variability in attached algal δ13C from −40 to −20‰ (mean ± SD = −29 ± 4) completely enveloped that observed for terrestrial leaf litter (mean = −28 ± 1‰). Therefore, for 50% of the fishes and 70% of the invertebrates it was impossible to discriminate between allochthonous and autochthonous carbon dependency. Faunal δ13C did not change in any quantitatively predictable manner with removal of riparian trees. Three conclusions are possible from this secondary analysis: (1) autotrophic pathways within forested headwaters are much more important to lotic foodwebs than would be suggested by their particulate inputs alone; (2) the great variability in attached algal δ13C may often preclude use of SIA for identifying carbon pathways in stream ecosystems; thus (3) the utility of carbon SIA in understanding anthropogenic alterations to the carbon budget of streams is presently minimal.
Androgenetic diploids of rainbow trout (Oncorhynchus mykiss) produced by fused sperm
Authors: Araki Kazuo , Shinma Hisako , Nagoya Hiroyuki , Nakayama Ichiro , Onozato Hiroshi
Published: August 2008

Androgenesis is a technique that produces individuals with all of their chromosomes from male parents. It can be useful in generating homozygous lines of fish, and in the recovery of species from cryopreserved sperm. We produced androgenetic diploids by using fused sperm to fertilize eggs. Eggs of albino "Yellow" rainbow trout (Oncorhynchus mykiss) were exposed to 60Co γ-ray irradiation to inactivate the maternally-derived nuclear DNA, and were then fertilized with wild-type rainbow trout sperm fused using an artificial seminal plasma containing 85 mM CaCl2. Embryos that reached the hatching stage (average 0.11%) were pigmented. The nuclear DNA content of cells from newly hatched fry was the same as the DNA content of erythrocyte nuclei of normal diploids.
Phytoplankton primary production of three temporary northern prairie wetlands
Authors: Robarts Richard D. , Arts Michael T. , Donald David B.
Published: August 2008

Measurements of phytoplankton primary production in three temporary Alberta ponds indicate a huge potential carbon and energy source for higher trophic levels associated with these systems. The ponds had high levels of NO3-N (maximum 1.6 mg∙L−1) and PO4-P (maximum 3.6 mg∙L−1). Water temperature varied by as much as 15 °C over the diel cycle, while primary production peaked in mid-afternoon. Production rates ranged from 0.6 to 400 mg C∙m−3∙T−1 and were strongly correlated (r = 0.9) with phytoplankton density. Total annual production for the ponds varied from 187 to 3311 kg C. These annual production values are low relative to prairie lakes; however, the number of small temporary ponds is about three orders of magnitude greater than lakes making phytoplankton production of these small water bodies a potentially important source of energy in prairie food webs.
Variation in geographic stock area, catchability, and natural mortality of ocean shrimp (Pandalus jordani): some new evidence for a trophic interaction with Pacific hake (Merluccius productus)
Authors: Hannah Robert W.
Published: August 2008

Interannual variation in geographic stock area, catchability, and natural mortality of age 2 ocean shrimp (Pandalus jordani) was investigated for the years 1980–1990, using commercial catch and logbook data. Stock area changed gradually from 1980–1990, but showed wide variation, demonstrating that an assumption of constant catchability is not valid for ocean shrimp. Stock area was positively correlated with total catch, suggesting that stock area increases roughly in proportion to shrimp abundance. The time series of fishing effort and effort per unit stock area were quite different, showing that fishing effort probably gives incorrect information on time trends in ocean shrimp fishing mortality. Natural mortality rates varied widely over the study period also and were positively correlated with the abundance of age 2+ Pacific hake (Merluccius productus), a known shrimp predator. The best correlations were between natural mortality rates and the number of age 2–7 Pacific hake. Hake abundance indices that included only age 3+ fish were not significantly correlated with shrimp natural mortality rates, suggesting that if a trophic interaction exists between these two species, it may be influenced by hake recruitment events.
Distribution of phytobenthos in the Yakima River basin, Washington, in relation to geology, land use and other environmental factors
Authors: Leland Harry V.
Published: August 2008

Benthic-algal distributions in the Yakima River, Washington, basin were, examined in relation to geology, land use, water chemistry, and stream habitat using indicator-species classification (TWINSPAN) and canonical correspondence analysis (CCA). Algal assemblages identified by TWINSPAN were each associated with a narrow range of water-quality conditions. In the Cascade geologic province, where timber harvest and grazing are the dominant land uses, differences in community structure (CCA site scores) and concentrations of major ions (Ca and Mg) and nutrients (solute P, SiO2and inorganic N) varied with dominant rock type of the basin. In agricultural areas of the Columbia Plateau province, differences in phytobenthos structure were based primarily on the degree of enrichment of dissolved solids, inorganic N, and solute P from irrigation-return flows and subsurface drainage. Habitat characteristics strongly correlated with community structure included reach altitude, turbidity, substratum embeddedness (Columbia Plateau), large woody-debris density (Cascade Range), and composition and density of the riparian vegetation. Algal biomass (AFDM) correlated with composition and density of the riparian vegetation but not with measured chemical-constituent concentrations. Nitrogen limitation in streams of the Cascade Range favored nitrogen-fixing blue-green algae and diatoms with endosymbiotic blue-greens, whereas nitrogen heterotrophs were abundant in agricultural areas of the Columbia Plateau.
Adaptive variation in palp and gill size of the zebra mussel (Dreissena polymorpha) and Asian clam (Corbicula fluminea)
Authors: Payne Barry S. , Miller Andrew C. , Hubertz Erica D. , Lei Jin
Published: August 2008

Significant interpopulation differences occur in palp to gill area ratios of two nonindigenous species of freshwater bivalves in North America, Dreissena polymorpha and Corbicula fluminea. Larger palps (both species) and smaller gills (C. fluminea) occur in individuals from habitats characterized by a relatively high suspended solids concentration. The extremely brief evolutionary history of both species in North America is strong evidence that these differences in palp to gill area ratios are ecophenotypic.
Distinct modulation of the endothelin-1 pathway iniNOS−/−andeNOS−/−miceThis article is one of a selection of papers published in the special issue (part 2 of 2) on Forefronts in Endothelin.
Authors: Labonté Julie , Brochu Isabelle , Simard Elie , D’Orléans-Juste Pedro
Published: August 2008

We hypothesized that constitutive endothelial NO synthase (eNOS) and inducible NO synthase (iNOS) have opposite effects on the regulation of endothelin and its receptors. We therefore sought to determine whether deletions of iNOS or eNOS genes in mice modulate pressor responses to endothelin and the expression of ETAand ETBreceptors in a similar fashion. Despite unchanged baseline hemodynamic parameters, anesthetized iNOS−/−mice displayed reduced pressor responses to endothelin-1, but not to that of IRL-1620, a selective ETBagonist. Protein content of cardiac ETAreceptors was reduced in iNOS−/−mice compared with wild-type mice, but that of ETBreceptors was unchanged. Anesthetized eNOS−/−mice presented a hypertensive state, accompanied by an enhanced pressor response to intravenous endothelin-1, whereas the pressor response to IRL-1620 was reduced. Protein levels were also found to be increased for ETAreceptors, but reduced for ETBreceptors, in cardiac tissues of eNOS−/−mice. In conscious animals, both strains responded equally to the hypotensive effect of an ETAantagonist, ABT-627, whereas orally administered A-192621, an ETBantagonist, increased MAP to a greater extent in eNOS−/−than in wild-type mice. Furthermore, significant levels of immunoreactive endothelin were found in mesenteric arteries in eNOS−/−but not in iNOS−/−or wild-type congeners. Our study shows that repression of iNOS or eNOS has differential effects on endothelin-1 and its receptors. We have also shown that the heart is the main organ in which iNOS or eNOS repression induces important alterations in protein content of endothelin receptors in adult mice.
Sustained Ca2+signaling and delayed internalization associated with endothelin receptor heterodimers linked through a PDZ fingerThis article is one of a selection of papers published in the special issue (part 2 of 2) on Forefronts in Endothelin.
Authors: Evans Nathan J. , Walker Jeffery W.
Published: August 2008

G protein-coupled receptors (GPCRs), including endothelin receptor A (ETA) and B (ETB), may form dimers or higher-order oligomers that profoundly influence signaling. Here we examined a PDZ finger motif within the C-terminus of ETAand its role in heterodimerization with ETB, and in homodimerization with itself, when expressed in HEK293 cells. Receptor dimerization was monitored by (i) fluorescence resonance energy transfer (FRET) between cyan fluorescent protein (CFP) (FRET donor) and tetracysteine/FlAsH (FRET acceptor) fused to the C-termini of ET receptors, and (ii) coimmunoprecipitation of ET receptors after mild detergent solubilization. Mutations in a PDZ finger motif at threonine403/serine404 eliminated FRET and reduced coimmunoprecipitation of heterodimers and homodimers. Functional consequences were evaluated by measuring mobilization of intracellular Ca2+and internalization of receptors in response to a 10 nmol/L ET-1 challenge. PDZ mutations converted a sustained Ca2+signal mediated by ETA:ETBheterodimers into a transient response, similar to that observed for homodimers or monomers. Heterodimers containing PDZ mutations were seen to internalize in a similar time domain (approximately 5 min) to the transient Ca2+elevation and with similar kinetics to internalization of ETAhomodimers or monomers. Without the PDZ mutations, heterodimers did not internalize over 15 min, suggesting the intriguing possibility that sustained Ca2+signaling was a consequence (at least in part) of delayed internalization. The results are consistent with structural models of ETA-receptor dimerization that place threonine403/serine404 of the PDZ finger motif at the interaction interface between heterodimers and homodimers. Sustained Ca2+signaling and delayed endocytosis of ETA:ETBheterodimers argues strongly for a unique dimer interface that impacts transmembrane signaling and internalization.
Endothelin: 20 years from discovery to therapyThis article is one of a selection of papers published in the special issue (part 2 of 2) on Forefronts in Endothelin.
Authors: Barton Matthias , Yanagisawa Masashi
Published: August 2008

Since its identification as an endothelial cell-derived vasoconstrictor peptide in 1988, endothelin-1, the predominant member of the endothelin peptide family, has received considerable interest in basic medical science and in clinical medicine, which is reflected by more than 20 000 scientific publications on endothelin research in the past 20 years. The story of endothelin is unique as the gene sequences of endothelin receptors and the first receptor antagonists became available within only 4 years of the identification of the peptide sequence.The first clinical study in patients with congestive heart failure was published only 3 years thereafter. Yet, despite convincing experimental evidence of a pathogenetic role for endothelin in development, cell function, and disease, many initial clinical studies on endothelin antagonism were negative. In many of these studies, study designs or patient selection were inadequate. Today, for diseases such as pulmonary hypertension, endothelin antagonist treatment has become reality in clinical medicine, and ongoing clinical studies are evaluating additional indications, such as renal disease and cancer. Twenty years after the discovery of endothelin, its inhibitors have finally arrived in the clinical arena and are now providing us with new options to treat disease and prolong the lives of patients. Possible future indications include resistant arterial hypertension, proteinuric renal disease, cancer, and connective tissue diseases.
Lysosomotropic drugs inhibit maturation of transforming growth factor-β
Authors: Basque Julie , Martel Marc , Leduc Richard , Cantin André M.
Published: August 2008

Transforming growth factor-β (TGFβ) is synthesized as a precursor protein, pro-TGFβ, that must be cleaved by a furin-like proteinase before it becomes biologically active. We hypothesized that alkalinization of the trans-Golgi network (TGN)/endosome system may suppress pro-TGFβ processing and decrease TGFβ secretion. This hypothesis was tested in human A549 alveolar epithelial and T98G glioblastoma cell lines and in C57BL/6 mice. Inhibition of furin-like activity with decanoyl-RVKR chloromethylketone suppressed pro-TGFβ processing, thereby significantly reducing the levels of secreted TGFβ. Brefeldin A, bafilomycin A1, ammonium chloride, and monensin also prevented pro-TGFβ processing. The alkalinizing lysosomotropic drugs chloroquine, hydroxychloroquine, amodiaquine, and azithromycin had a similar effect on the overall production of mature bioactive TGFβ. Reduced levels of secreted TGFβ were also associated with a decrease in Smad2 signaling. Mice treated with chloroquine showed a decrease in bronchoalveolar lavage fluid TGFβ. We conclude that alkalinizing lysosomotropic drugs inhibit pro-TGFβ processing.
Acetylcholine evokes an InsP3R1-dependent transient Ca2+signal in rat duodenum myocytes
Authors: Fritz Nicolas , Dabertrand Fabrice , Mironneau Jean , Macrez Nathalie , Morel Jean-Luc
Published: August 2008

In smooth muscle myocytes, agonist-activated release of calcium ions (Ca2+) stored in the sarcoplasmic reticulum (SR) occurs via different but overlapping transduction pathways. Hence, to fully study how SR Ca2+channels are activated, the simultaneous activation of different Ca2+signals should be separated. In rat duodenum myocytes, we have previously characterized that acetylcholine (ACh) induces Ca2+oscillations by binding to its M2muscarinic receptor and activating the ryanodine receptor subtype 2. Here, we show that ACh simultaneously evokes a Ca2+signal dependent on activation of inositol 1,4,5-trisphosphate (InsP3) receptor subtype 1. A pharmacologic approach, the use of antisense oligonucleotides directed against InsP3R1, and the expression of a specific biosensor derived from green-fluorescent protein coupled to the pleckstrin homology domain of phospholipase C, suggested that the InsP3R1-dependent Ca2+signal is transient and due to a transient synthesis of InsP3via M3muscarinic receptor. Moreover, we suggest that both M2and M3signalling pathways are modulating phosphatidylinositol 4,5-bisphosphate and InsP3concentration, thus describing closely interacting pathways activated by ACh in duodenum myocytes.
Phylogenetic Approaches to the Study of Extinction
Authors: Purvis Andy
Published: August 2008

Species extinction is both a key process throughout the history of life and a pressing concern in the conservation of present-day biodiversity. These two facets have largely been studied by separate communities using different approaches. This article illustrates with examples some of the ways that considering the evolutionary relationships among species—phylogenies—has helped the study of both past and present species extinction. The focus is on three topics: extinction rates and severities, phylogenetic nonrandomness of extinction, and the testing of hypotheses relating extinction-proneness to attributes of organisms or species. Phylogenetic and taxic approaches to extinction have not fully fused, largely because of the difficulties of relating discrete taxa to the underlying continuity of phylogeny. Phylogeny must be considered in comparative tests of hypotheses about extinction, but care must be taken to avoid overcorrecting for phylogenetic nonindependence among taxa.
Recent Advances in Understanding Integrative Control of Potassium Homeostasis
Authors: Youn Jang H. , McDonough Alicia A.
Published: August 2008

The potassium homeostatic system is very tightly regulated. Recent studies have shed light on the sensing and molecular mechanisms responsible for this tight control. In addition to classic feedback regulation mediated by a rise in extracellular fluid (ECF) [K+], there is evidence for a feedforward mechanism: Dietary K+ intake is sensed in the gut, and an unidentified gut factor is activated to stimulate renal K+ excretion. This pathway may explain renal and extrarenal responses to altered K+ intake that occur independently of changes in ECF [K+]. Mechanisms for conserving ECF K+ during fasting or K+ deprivation have been described: Kidney NADPH oxidase activation initiates a cascade that provokes the retraction of K+ channels from the cell membrane, and muscle becomes resistant to insulin stimulation of cellular K+ uptake. How these mechanisms are triggered by K+ deprivation remains unclear. Cellular AMP kinase–dependent protein kinase activity provokes the acute transfer of K+ from the ECF to the ICF, which may be important in exercise or ischemia. These recent advances may shed light on the beneficial effects of a high-K+ diet for the cardiovascular system.