Osmerus Mordax Research Articles

Habitat Selection of Predator and Prey: Atlantic Salmon and Rainbow Smelt Overlap, Based on Temperature and Dissolved Oxygen

Abstract We investigated the predator-prey interactions of two pelagic species, landlocked Atlantic salmon Salmo salar and rainbow smelt Osmerus mordax, in a large-lake ecosystem. Our goal was to determine the overlap of habitats selected, based on profiles of temperature and dissolved oxygen (DO). We used hydroacoustics to ascertain the seasonal habitat selection of rainbow smelt and gill nets to sample Atlantic salmon in the Inland Sea of Lake Champlain, Vermont. We identified patterns of smelt habitat selection by overlaying the acoustically determined vertical distributions of smelt onto profiles of water temperature and DO. To verify species composition of acoustical targets, we performed midwater trawls using a stepped-oblique method and found that rainbow smelt constituted 99.5% of trawl catches. Trawl catches and acoustic fish density were correlated, indicating that acoustic targets represented trawled fish. Atlantic salmon habitat selection was estimated from temperature and DO profiles taken at...

The freeze-avoidance response of smelt Osmerus mordax: initiation and subsequent suppression of glycerol, trimethylamine oxide and urea accumulation.

Smelt (Osmerus mordax) were maintained at either ambient water temperature or approximately 5 degrees C and various aspects of their freeze-avoidance response were examined from early winter until early spring. Plasma levels of glycerol, trimethylamine oxide (TMAO) and urea were elevated by December 15 and continued to increase in fish held in ambient conditions. In contrast, fish held under warm conditions exhibited decreased glycerol and urea content in plasma, muscle and liver. Plasma and liver TMAO levels also decreased in these fish while muscle TMAO did not vary from the initial values. The activity of liver enzymes involved with the production of glycerol did not differ significantly between groups and had decreased by the end of the study. Antifreeze protein (AFP) expression increased over the duration of the experiment. In January samples, AFP activity (thermal hysteresis) did not vary significantly between groups but mRNA levels were significantly lower in the smelt held at warm temperatures.

Comparison of liver enzymes in osmerid fishes: key differences between a glycerol accumulating species, rainbow smelt ( Osmerus mordax), and a species that does not accumulate glycerol, capelin ( Mallotus villosus)

Activities of enzymes associated with glycerol synthesis were compared in the liver of two osmerid fishes, the smelt ( Osmerus mordax), which can accumulate high (400 mM) levels of glycerol and capelin ( Mallotus villosus) that does not accumulate glycerol. Animals were sampled at approximately the same time of year and temperature thus negating potential seasonal effects. These species are closely related, reducing interpretative issues involving comparison between unrelated species. We found that key enzyme activities were elevated in the smelt relative to the non-glycerol accumulating capelin, namely enzymes involved with glycolysis (phosphofructose kinase-1 and aldolase), amino acid metabolism (aspartate aminotransferase and alanine aminotransferase), gluconeogenesis (phosphoenolpyruvate carboxykinase) and glycerol synthesis (glycerol-3-phosphate dehydrogenase). The enzyme profiles strongly support the hypothesis that smelt can synthesize glycerol by utilizing glycogen and amino acids as the carbon source and that they have increased capacity for metabolic flux through loci required for synthesis of the three carbon intermediate dihydroxyacetone phosphate and subsequently glycerol synthesis.

Structural and functional characterization of a C-type lectin-like antifreeze protein from rainbow smelt (Osmerus mordax).

Antifreeze proteins (AFPs) are produced by several cold-water fish species. They depress physiological freezing temperatures by inhibiting growth of ice crystals and, in so doing, permit the survival of these fish in seawater cooler than their normal freezing temperatures. The type II AFP from rainbow smelt (Osmerus mordax), which is a member of the C-type lectin superfamily, was characterized in terms of its Ca2+-binding quaternary structure and the role of its single N-linked oligosaccharide. The protein core of the smelt AFP, shown through sequence homology to be a C-type lectin carbohydrate-recognition domain, was found to be protease resistant. Smelt AFP was also shown to bind Ca2+, as determined by ruthenium red staining and a conformational change on Ca2+ binding detected by intrinsic fluorescence. The N-linked oligosaccharide was found to have no effect on protease resistance, dimerization, or antifreeze activity. Thus its role, if any, in the antifreeze function of this protein remains unknown. Smelt AFP was also shown to be a true intermolecular dimer composed of two separate subunits. This dimerization did not require the presence of N-linked oligosaccharide or bound Ca2+. Smelt AFP dimerization has implications for the effective solution concentration and measurement of its activity. This finding may also lead to new interpretation of the mechanism of ice-growth inhibition by this AFP.

Using bioenergetics models to predict stable isotope ratios in fishes

To describe temporal dynamics of stable isotope ratios in fishes, we developed a bioenergetics-based model that links isotope ratios to growth, as influenced by fish size, temperature, diet, and prey quality. The model includes error terms for isotope ratios, diet proportions, and fractionation. The model accurately predicted temporal δ15N dynamics of lake trout (Salvelinus namaycush) in a diet-switch experiment but was less successful for δ13C, possibly because of variable fractionation. The model was then used in three heuristic applications. In a diet-validation scenario, a model derived from limited knowledge of rainbow smelt (Osmerus mordax) diet reasonably estimated δ13C and δ15N compared with a null model but inaccurately estimated prey consumption. In a scenario where adult lake trout briefly cannibalized stocked lake trout fingerlings, the detectability of a cannibalism-induced δ15N increase depended on predator size, duration of cannibalism, and sample size. In a scenario where seasonal isotopic variability occurred at the base of a food web, variation propagated to higher trophic levels depended on consumer size and diet. Our approach is most valuable when used to examine multiple diet combinations that produce observed stable isotope ratios; one can then identify the most reasonable diets through field tests or other observations.

Climate change and abundance cycles of two sympatric populations of smelt (Osmerus mordax) in the middle estuary of the St. Lawrence River, Canada

Commercial catches of two ecologically distinct sympatric smelt (Osmerus mordax) populations segregated along the two shores of the St. Lawrence middle estuary exhibited inverse patterns with periodicities on the order of 30 years. The influence of water level in the St. Lawrence River and air temperature, chosen to reflect variations in hydrology and climate, differed markedly between the two populations. Analyses revealed that both water level and temperature were generally positively related with north-shore smelt landings and negatively related with south-shore smelt landings. For both populations, a number of significant climatic factors contributing to variance in smelt landings were lagged by one to three years relative to the year of landings, indicating that climatic variables influenced smelt recruitment. The contrasting role of hydroclimatic variables in driving these abundance cycles is likely related to differential exploitation of estuarine habitats; the south-shore population is associated with shallow shoal habitat, whereas the north-shore population is associated with deep channel habitat. The responses of the two smelt populations also reflect the fundamental ecological differences existing between shoal and channel habitats, indicating that future climate change may differentially affect other populations or species that are segregated between these two habitats.

Initial Observations on Thiamine Hydrochloride Treatment of Eggs of Landlocked Fall Chinook Salmon

Abstract Eggs of landlocked fall chinook salmon Oncorhynchus tshawytscha from Lake Oahe, South Dakota, were treated with standing-bath thiamine hydrochloride at 250 and 1,000 mg/L beginning at water hardening (1 h) and continuing during transport (4 h). Biologically insignificant increases (1–2%) in embryo survival from eyed egg to hatch were observed for both of the thiamine treatment concentrations compared with nontreated controls, but no differences were observed in percent survival to the eyed stage, hatch, swim-up, or 28 d after swim-up. Egg thiamine concentrations ranged from 2.85 to 16.14 nmol/g of wet tissue in the control eggs. These results were probably influenced by unanticipated dietary shifts of adult salmon during an unusual year of very low availability of rainbow smelt Osmerus mordax. Neither thiamine hydrochloride treatment significantly elevated egg thiamine concentrations, but the detection of relatively small amounts of thiamine uptake was probably hindered by measurement variation. ...

Retention ofBythotrephesSpines in the Stomachs of Eastern Lake Erie Rainbow Smelt

Abstract The exotic cladoceran Bythotrephes longimanus is an important food resource for eastern Lake Erie rainbow smelt Osmerus mordax. Bythotrephes possesses a long, chitinous caudal spine that is generally used to quantify its presence in fish diet studies despite concerns that it may be retained within fish stomachs longer than other prey items. We investigated spine retention in rainbow smelt collected in the eastern basin of Lake Erie in June (day and night), July (night), and October (night) of 1998 and 1999. To assess differential retention of Bythotrephes spines in rainbow smelt stomachs, we compared counts of Bythotrephes caudal spines to direct counts of Bythotrephes bodies or mandible pairs. Retention of caudal spines was evident in yearling and older (age-1+) rainbow smelt caught during the day in June as well as in age-1+ fish caught at night in July and October and in young-of-year fish captured at night in October. Smelt stomach fullness decreased with time after sunset, indicating lower n...

Resolution of population structure in a species with high gene flow: microsatellite variation in the eulachon (Osmeridae: Thaleichthys pacificus )

Five microsatellite loci were used to examine genetic variation within and among putative populations of the eulachon, Thaleichthys pacificus (Pisces: Osmeridae), over the entire range of the species. A previous mitochondrial DNA study, while revealing a high degree of genetic variation within the species, did not resolve the level of population sub-division expected for this anadromous fish. Two microsatellite loci were developed from eulachon DNA and, in addition to three microsatellite loci from the rainbow smelt, Osmerus mordax, were employed as a class of "higher resolution" markers in an attempt to further resolve the population structure of eulachon. The level of genetic variation observed at these loci was surprisingly low (heterozygosity ranged from 4% to 64%; number of alleles ranged from three to ten; maximum size range of alleles was 16 base pairs), yet revealed the greater power of microsatellites over mitochondrial DNA for resolving population sub-division within eulachon. More pairwise population comparisons were significant with the microsatellite data, and the microsatellite F ST value was twice the value observed with mtDNA (mtDNA F ST=0.023; microsatellite F ST=0.045). Despite this greater sensitivity, it was difficult to define distinct demographic units in eulachon, a species which is currently the focus of conservation concern. Eulachon highlight the challenges of examining population structure in species with inferred high gene flow.

Species-level and community-level data analyses reveal spatial differences and temporal change in the crustacean zooplankton of a large Canadian lake (Lake Simcoe, Ontario)

Consensus-building univariate and multivariate data analyses were used to identify patterns in space and time over seven years among 12 sampling stations in a 720 km2 hardwater Canadian lake (Lake Simcoe, Ontario, Canada). There were 15 copepods and 26 cladoceran species identified in samples collected throughout the May-October periods of 1986-1992 from Lake Simcoe. Eleven crustacean zooplankters accounted for 88% of the total average density of all recorded species in the lake. Most of these (the main exceptions being Eubosmina coregoni and Daphnia pulicaria) are ubiquitous taxa with wide environmental tolerances. Multivariate analyses of these data identified spatial differences and a temporal trend in community composition. The use of Cao et al.’s (1997a) "CY-dissimilarity" measure combined with Ward's Linkage clustering algorithm and non-metric multidimensional scaling ordination resulted in several clearly defined groups of sampling units (SUs), which apparently were separated predominantly on the basis of variables related to space (sampling station) and time (year). The 7-year record suggested several lines of evidence for trends in community structure. Averaged over all stations, the yearly intra-station dissimilarities steadily increased 78% by 1992. The greatest rates of increase in yearly intra-station dissimilarity with 1986 baselines were found for the deeper sampling stations. These whole community-level trends were the net results of a many different patterns of change identified in species-level analyses. Such patterns included increasing densities over the 7-year period of Daphnia longiremis and Diaphanosoma birgei and declining densities of Daphnia pulicaria. Many other taxa showed highest values in the middle years of the study. Community-level temporal trends were least evident at sampling locations in the shallower and warmer Cook’s Bay, despite clear trends in several individual species. A significantly greater representation by large-bodied zooplankton species in the latter years of the study was consistent with declining stocks of rainbow smelt (Osmerus mordax) and lake herring (Coregonus artedii), suggesting the associated relaxation of predation pressure as a possible cause. Several species indicative of eutrophic states (Acanthocyclops vernalis, Chydorus sphaericus and Bosmina longirostris) were common in the samples. The scarcity of the calanoid Senecella calanoides and the absence of another classic oligotrophic indicator calanoid, Limnocalanus macrurus in the Lake Simcoe samples suggests impairment of their deep, cold-water habitat and is consistent with the modelled historical loss of hypolimnetic dissolved oxygen in Lake Simcoe.

Interactions between Young-of-the-Year Exotic Rainbow Smelt and Native Yellow Perch in a Northern Temperate Lake

Yellow perch Perca flavescens recruitment in Crystal Lake, Vilas County, Wisconsin, has declined since the exotic rainbow smelt Osmerus mordax increased in abundance. The yellow perch population is in decline because of low juvenile survival. However, diet analyses indicate that predation by adult smelt does not appear to be the cause. We investigated interactions between age-0 yellow perch and age-0 rainbow smelt by comparing changes in abundance and distributions, maximum mouth gapes, and the amount and type of prey eaten. During 1995 and 1996, age-0 smelt and perch hatched at similar times, had similar spatial distributions, and preferred similar prey. Diet overlap exceeded 45% on all sampling dates during the spring and summer of 1995 and 1996 and exceeded 60% on all but the first and last sampling dates in 1996. Two species of Diaptomus were the preferred prey of both smelt and perch, although smelt ate more of the larger size-classes than did perch throughout 1996. Consumption by smelt may have led to a decline in Diaptomus during the early summer of 1996. Estimates of temperature, hatch date, and growth derived from a long-term data set were used as input for bioenergetics simulations that estimated the proportion of maximum attainable consumption realized by the average age-0 perch in each year, when they occurred, between 1981 and 1996. During 1995 and 1996, years where age-0 smelt and perch were documented together, the proportion of maximum attainable consumption was significantly below that of any successful year-class observed during the long-term record. Age-0 perch did not survive in measurable numbers through the entire summer in either 1995 or 1996. Exploitation competition between age-0 perch and smelt may reduce the likelihood of strong year-classes of yellow perch when year-classes of rainbow smelt occur.

The Fish Assemblage of a Newfoundland Estuary: Diel, Monthly and Annual Variation

Twice monthly sampling over two 16 month periods at a shallow site on Newfoundland's east coast showed the fish assemblage to be dominated by four taxa (Gasterosteus aculeatus, G. wheatlandi, Osmerus mordax, Gadus spp.) that accounted for 96% of the individuals collected. Of the 16479 fish measured, 65% were adults based on the estimated size of first spawning. The fish assemblage was dominated (86%) by species with demersal eggs, several of which spawn at the same shallow sites used by juveniles as nursery sites. Coastal spawning and demersal eggs maintain offspring in coastal nursery areas where survival is thought to be increased. Number of species and number of fish were both correlated with water temperature being highest from mid-summer to early autumn and lowest in winter. Temperature, time of spawning, and movements of juveniles and adults facilitated grouping species into five assemblages based on seasonal abundance: seasonal periodic species (summer and winter), regular species, regular species collected in all seasons except winter, and occasional (rare) species. At the diel scale, two consistent species groupings were observed: species that showed no significant difference between day and night and species caught primarily at night. Number of night species exceeded day species by a factor of two. No seine-caught species in shallow water exhibited significantly higher catches during the day. Observations by SCUBA divers indicated some species were more abundant during day time at slightly deeper depths. This observation in conjunction with day and night seining in shallower water, suggests these species aggregate in deeper water during day and move to shallow waters at night.

DISTRIBUTIONS OF LAKE FISHES OF THE NORTHEAST USA — III. SALMONIDAE AND ASSOCIATED COLDWATER SPECIES

We present distributional maps and discuss native status for fish species characteristic of coldwater lakes, sampled from 203 randomly selected lakes in the northeastern USA (New England, New York, New Jersey). Eleven coldwater fish species from four families (Salmonidae, Osmeridae, Gadidae, Cottidae) were collected during the summers of 1991 to 1996 by the Environmental Monitoring and Assessment Program (EMAP). The most widespread species were brook trout and rainbow smelt, collected at 23% and 18% of the sampled lakes, respectively. Stocked (put-and-take) rainbow trout occurred at 10% of the lakes, while the remaining fish species (brown trout, landlocked Atlantic salmon, lake trout, Arctic char, lake whitefish, cisco, burbot, slimy sculpin) were collected at less than 6% of the lakes. We also provide comparative data on physical (surface area, depth, elevation), chemical (pH and total phosphorus), and watershed characteristics of the lakes where these species were collected.

Cloning of glycerol-3-phosphate dehydrogenase cDNAs from two fish species and effect of temperature on enzyme expression in rainbow smelt ( Osmerus mordax)

Rainbow smelt ( Osmerus mordax) can accumulate extreme levels of glycerol in their blood during winter. Low temperatures are required for glycerol accumulation in smelt blood and the enzyme glycerol-3-phosphate dehydrogenase (GPDH) has been suggested to play a role in glycerol production/concentration in this species. In the present study, cDNA sequences encoding glycerol-3-phosphate dehydrogenase (GPDH) from rainbow smelt and Atlantic salmon ( Salmo salar) were cloned. The encoded GPDH protein sequences were very similar to one another (88% identity). Using RT-PCR, GPDH mRNA was detected in skin, gill, heart, head kidney, brain and liver from both salmon and smelt obtained in December. However, GPDH was not detected in salmon intestine and spleen or in smelt intestine. Examination of GPDH expression in smelt liver during February by Northern blotting revealed temperature regulation. Elevation of the temperature resulted in a significant decrease in liver GPDH transcript level. Serum glycerol levels decreased concomitantly. These findings suggest a role for GPDH in the accumulation of glycerol in smelt at low temperatures.

Environmental Influences on Landlocked Fall Chinook Salmon Reproductive Characteristics

Abstract From 1988 to 1998, we evaluated relationships among several environmental and biological variables and the fecundity, egg size, and embryo survival to the eyed stage of landlocked fall chinook salmon Oncorhynchus tshawytscha from Lake Oahe, South Dakota. The environmental variables recorded in Lake Oahe included monthly and total yearly inflows and outflows, end-of-month elevations, yearly mean end-of-month elevations, and 13°C and 15°C habitat volumes. Biological variables included gill-net catch per unit effort (CPUE) of lake herring Coregonus artedi, rainbow smelt Osmerus mordax, and chinook salmon (for age-0, age-1 and older, and all fish); chinook salmon age-1 mean relative weight; and rainbow smelt abundance in both the 13°C and 15°C habitat volumes. Chinook salmon fecundity was significantly related to rainbow smelt CPUE (r = 0.841) and chinook salmon CPUE (r = 0.853). Fecundity was also significantly related to mean relative weight of age-1 and older salmon collected in gill nets the year...

Climate change and abundance cycles of two sympatric populations of smelt (<i>Osmerus mordax</i>) in the middle estuary of the St. Lawrence River, Canada

Climate change and abundance cycles of two sympatric populations of smelt (<i>Osmerus mordax</i>) in the middle estuary of the St. Lawrence River, Canada

Some characteristics of freezing avoidance in two osmerids, rainbow smelt and capelin

Winter‐acclimatised rainbow smelt Osmerus mordax have elevated levels of glycerol and trimethylamine oxide (TMAO), and a protein antifreeze, all of which are lost in summer. No seasonal differences were found in glycerol‐3‐P‐dehydrogenase, glycerol‐3‐phosphatase and glutamate dehydrogenase, which are involved in the synthesis of glycerol or its precursors. Although glycerol production requires NADH, no large seasonal differences were found in the activities of glucose‐6‐P‐dehydrogenase and 6‐phosphogluconate dehydrogenase (pentose phosphate pathway), malate dehydrogenase and aspartate aminotransferase (malate‐aspartate shuttle) or in the NAD : NADH ratio. Thus, other regulatory mechanisms must be involved. Capelin Mallotus villosus collected from mid water in the Barents Sea in September (water temperatures +0·4 to −1·6°C) had only negligible amounts of glycerol, and no protein antifreeze, although serum TMAO levels (44 mm) were unusually high for a teleost. Capelin appear to avoid freezing largely by avoiding water layers with temperatures below their body freezing point, and by occasional supercooling.

Some characteristics of freezing avoidance in two osmerids, rainbow smelt and capelin

Some characteristics of freezing avoidance in two osmerids, rainbow smelt and capelin

Sustainability of the Lake Superior Fish Community: Interactions in a Food Web Context

The restoration and rehabilitation of the native fish communities is a long-term goal for the Laurentian Great Lakes. In Lake Superior, the ongoing restoration of the native lake trout populations is now regarded as one of the major success stories in fisheries management. However, populations of the deepwater morphotype (siscowet lake trout) have increased much more substantially than those of the nearshore morphotype (lean lake trout), and the ecosystem now contains an assemblage of exotic species such as sea lamprey, rainbow smelt, and Pacific salmon (chinook, coho, and steelhead). Those species play an important role in defining the constraints and opportunities for ecosystem management. We combined an equilibrium mass balance model (Ecopath) with a dynamic food web model (Ecosim) to evaluate the ecological consequences of future alternative management strategies and the interaction of two different sets of life history characteristics for fishes at the top of the food web. Relatively rapid turnover rates occur among the exotic forage fish, rainbow smelt, and its primary predators, exotic Pacific salmonids. Slower turnover rates occur among the native lake trout and burbot and their primary prey—lake herring, smelt, deepwater cisco, and sculpins. The abundance of forage fish is a key constraint for all salmonids in Lake Superior. Smelt and Mysis play a prominent role in sustaining the current trophic structure. Competition between the native lake trout and the exotic salmonids is asymmetric. Reductions in the salmon population yield only a modest benefit for the stocks of lake trout, whereas increased fishing of lake trout produces substantial potential increases in the yields of Pacific salmon to recreational fisheries. The deepwater or siscowet morphotype of lake trout has become very abundant. Although it plays a major role in the structure of the food web it offers little potential for the restoration of a valuable commercial or recreational fishery. Even if a combination of strong management actions is implemented, the populations of lean (nearshore) lake trout cannot be restored to pre-fishery and pre-lamprey levels. Thus, management strategy must accept the ecological constraints due in part to the presence of exotics and choose alternatives that sustain public interest in the resources while continuing the gradual progress toward restoration.

Shifts in Depth Distributions of Alewives, Rainbow Smelt, and Age-2 Lake Trout in Southern Lake Ontario following Establishment of Dreissenids

Abstract In the mid-1990s, biologists conducting assessments of fish stocks in Lake Ontario reported finding alewives Alosa pseudoharengus, rainbow smelt Osmerus mordax, and juvenile lake trout Salvelinus namaycush at greater depths than in the mid-1980s. To determine if depth distributions shifted coincident with the early 1990s colonization of Lake Ontario by exotic Dreissena mussels, we calculated mean depth of capture for each of the three species during trawl surveys conducted annually during 1978–1997 and examined the means for significant deviations from established patterns. We found that mean capture depth of alewives, rainbow smelt, and age-2 lake trout shifted deeper during the build up of the dreissenid population in Lake Ontario but that timing of the shift varied among seasons and species. Depth shifts occurred first for rainbow smelt and age-2 lake trout in June 1991. In 1992, alewives shifted deeper in June followed by age-2 lake trout in July–August. Finally, in 1993 and 1994, the distrib...