bluuebunny/crossref_metadata_2025_split huggingface dataset:
Distribution, growth and transformation timing of larval Geotria australis in New Zealand
Authors: Tedd P. R. , Kelso J. R. M. 
Published: July 2006

AbstractLamprey, Geotria australis, are widely distributed in New Zealand and are common in streams and rivers of the west coast of both islands, the southern tip of the North Island, the Banks Peninsula and the southern coast of the South Island. In fresh water, lamprey are found in association with all substrate types but are most commonly (> 50% of the sample sites) found in association with finer gravels. There is insufficient evidence to determine any change in historically abundant adult spawning migrations. Spawning, back calculated from larval growth rates, probably occurs late November‐December, and emergence at 9.63 mm occurs in January. We estimate that, on average, ammocoetes grow 0.068 mm/day throughout the year, and metamorphose and emigrate to sea between January‐May, 3.5 years after spawning at 101 mm (SD = 6.7).
Instream size segregation and density of Geotria australis ammocoetes in two New Zealand streams
Authors: Kelso J. R. M. , Todd P. R. 
Published: July 2006

Abstract Geotria australis occurred almost to the upstream limit of detectable discharge in two New Zealand streams. The length, and consequently age, of larvae differed over the course of the stream and smallest animals ‐ presumed to be age 0 ‐ predominated upstream. Metamorphosing larvae (mean length 99.5 mm) typically occurred in downstream reaches, where flows were higher and substrate was coarser. We estimated that annual larval survival was 47% for age 0 to 1 and 77% for age 1 to 2. Differences in the relation between length and weight occurred both between years within a stream and between streams; thus, we assume growth is generally variable. The density of ammocoetes in New Zealand streams ranged from 0 to 104 m−2 and was significantly related to substrate type and depth in a multiple linear regression model. Because of the predictable nature of lamprey distribution and abundance, we believe it should be possible to estimate the absolute abundance of ammocoetes in a catchment with only a limited assessment of substrate properties.
A further assessment of trophic and spatial inter‐relations of galaxiids and salmonids in New Zealand
Authors: Glova G. J. , Sagar P. M. 
Published: July 2006

AbstractThe trophic and spatial inter‐relations between 2 small native fish (Galaxias vulgaris Stokell and G. paucispondylus Stokell, Galaxiidae) and juveniles of 2 introduced fish (Oncorhynchus tshawytscha Walbaum and Salmo trutta L., Salmonidae) were investigated in a New Zealand stream. Interspecific overlap in timing of feeding among these four fish species was greatest between pre‐dusk and pre‐dawn (1730‐0530). Aquatic invertebrates were consumed exclusively by all fish species except O. tshawytscha, which also preyed on Trichoptera imagos, particularly at night. Dietary similarities were least between galaxiids, moderate between galaxiids and salmonids, and greatest between salmonid species. Both galaxiid species were found primarily in riffles, with G. vulgaris occupying slightly deeper (≤0.3 m) and slower (0.5–0.8 m. s−1) waters than did G. paucispondylus (≤0.2 m deep and 0.7‐1.0 m. s−1 water velocity); salmonids were mostly in pools and runs, with O. tshawytscha occupying slightly slower (0.1‐0.2 m. s−1) and deeper (≤0.5 m) waters than those occupied by S. trutta (0.2–0.5 m. s−1 water velocity and ≤0.4 m deep). The interspecific differences in feeding and microdistribution presumably reduce interaction between sympatric populations of galaxiids and salmonids.
Winter movements of burbot (Lota lota) during an extreme drawdown in Bull Lake, Wyoming, USA
Authors: Bergersen E. P. , Cook M. F. , Baldes R. J. 
Published: July 2006

AbstractWinter movements of burbot (Lota lota) were monitored in Bull Lake, Wyoming during a record low water storage period in the winter of 1985–1986. Burbot with surgically implanted ultrasonic transmitters were commonly sedentary during the drawdown. The fish that did move were most active during dusk and at night in winter and during the day in spring. Burbot did not appear to occupy well defined home ranges or show discernible movement patterns. Movement into shallow water during winter was attributed to colder water temperatures and the onset of the spawning season. Burbot were always found associated with silt substrates during the drawdown. Aerial photographs of the exposed bottom revealed that virtually all suitable spawning and nursery habitat for burbot was eliminated by the 13.4‐m drawdown.
Digestion of larval American shad by cyprinids
Authors: Rottiers D. V. , Johnson J. H. 
Published: July 2006

AbstractCyprinids have pharyngeal teeth for grinding food before swallowing and a continuous gut with no discrete stomach. This digestive tract structure, as well as the feeding behavior traits shown by cyprinids, makes it difficult to identify and measure the amount of food consumed by these fishes. The relations among quantity of food in cyprinid gut, time after feeding and predator size were described by log‐linear multiple regression. The number of intact American shad (Alosa sapidissima (Wilson)) larvae eaten in laboratory experiments was estimated by extrapolating the regression for the amount of food in the gut over time for predators of various size. The numbers of larval American shad in guts of fish captured in the Juniata River, Pennsylvania, were not significantly different from those estimated with the equations derived from laboratory data. In view of their abundance in rivers and their potential digestion rate for larval fish, cyprinids can be expected to have a marked influence on reducing the numbers of larval American shad.
Timing of spawning in cultured and wild Atlantic salmon (Salmo salar) and brown trout (Salmo trutta) in the River Vosso, Norway
Authors: Lura H. , Sægrov H. 
Published: July 2006

AbstractSpawning time and size of wild and nonnative cultured female Atlantic salmon (Salmo salar L.) were studied in the River Vosso, Norway. Cultured immigrants were smaller, and peak spawning occurred 21 and 26 days earlier relative to wild salmon in 1991 and 1992, respectively. It was calculated that hatching and initial feeding of offspring of cultured females peaked 12 and 9 days earlier in spring 1992 and 19 and 8 days earlier in spring 1993 relative to offspring of wild females. Spawning time of the cultured salmon is similar to most Norwegian salmon populations and to cultured fish in other streams. In the River Vosso it also overlaps with that of brown trout (Salmo trutta L.), which may increase hybridization. The early time of breeding in nonnative fish indicates local adaptation in this trait in wild salmon. The consequences of early breeding of cultured fish are unpredictable in relation to spring temperatures but probably reduce their relative breeding success. The smaller size may also reduce the success of cultured females.
The effect of depth on the interaction between perch (Perca fluviatilis) and minnow (Phoxinus phoxinus)
Authors: Eklöv A. G. , Greenberg L. A. , Kristiansen H. 
Published: July 2006

AbstractWe tested the hypothesis that small fishes avoid piscivores by increasing their use of shallow water areas, thereby reducing the capture success of the piscivore. Experiments were conducted in 600‐1 aquaria, using perch (Perca fluviatilis) as the piscivore and minnow (Phoxinus phoxinus) as the prey. Two size classes of minnows, presented alone and together, were placed together with perch in aquaria with and without shallow water areas. The capture success of perch and use of depth by minnows changed as predicted by our hypothesis. In addition, we observed a decrease in the shoal size of minnows when perch were present. Perch selected large minnows over small minnows when both size classes were present, probably because large minnows were a more energetically profitable prey size.
The cost of early maturation on growth, body condition and somatic lipid content in a lake pumpkinseed (Lepomis gibbosus) population
Authors: Justus J. A. , Fox M. G. 
Published: July 2006

AbstractWe investigated the implications of early maturation in a central Ontario population of pumpkinseed (Lepomis gibbosus) by comparing the growth trajectory, body condition, lipid to body weight ratio and past growth history of mature and immature females through the 1992 growing season. Pumpkinseeds were sampled from Beloporine Lake from May 28 to July 24 and on November 20, just prior to freeze‐up of the lake. Prior growth history and length at age were determined by backcalculation from scale annuli. Nearly all females age 3 and older had matured in 1992, so we focused on age 2 females (22% mature). Females that matured at age 2 were significantly larger at the end of their first year of life than those that did not mature at age 2, although there was no significant difference between groups in the prior year's growth rate. The mature age 2 females were significantly larger than immatures, at the beginning and end of their third growing season, but not during the June 2 ‐ July 19 breeding season. The condition factor of mature females was higher than that of immature females on all but one collection date. However, the mean somatic lipid‐to‐body weight ratio was higher in immature females on all sample dates and significantly higher over the grwing season. We conclude that the costs of early maturation include lack of length and weight gain during the breeding season, and loss of stored lipid. The latter may be associated with increased overwinter mortality.
Comparison of population dynamics of Atlantic salmon (Salmo salar) and brown trout (Salmo trutta) in a small tributary of the River Scorff (Brittany, France)
Authors: Baglinière J.‐L. , Prévost E. , Malsse G. 
Published: July 2006

AbstractThe population dynamics of Atlantic salmon (Salmo salar L.) and brown trout (Salmo trutta L.) were compared in a small tributary of the River Scorff (Brittany, France) from spawning time to the beginning of the third growing season. The spawning and fry emergence of the two species took place at approximately the same time. In the first autumn, the densityof 0+ juveniles and settling rate from the egg stage were much higher in trout than in salmon. The emigration rate from 0+ population was much higher in trout than in salmon. The size of resident and migrating fish was always smaller in salmon than in trout, whatever the age. The low level of salmon production in the brook, compared with trout, was the result of low survival from egg to 0+ stage in autumn, combined with the small proportion of juveniles migrating after the first growing season. This was not compensated by a high number of migrants the next year. The role of physical habitat, inter‐and intraspecific competition, predation and migration dependence on size and early sexual maturity is discussed. Indications are that small tributaries of the type studied are of great value for recruitment in trout but not very productive for juvenile salmon.
The influence of physical watercourse parameters on the degree of anadromy in different lake populations of Arctic charr (Salvelinus alpinus(L.)) in northern Norway
Authors: Kristoffersen K. 
Published: July 2006

AbstractThe influence of physical watercourse parameters on the degree of anadromy was studied in 15 lake populations of Arctic charr (Salvelinus alpinus(L.)) in northern Norway. The anadromy of the different populations was scored based on the following criteria; marine parasites. fish length and length at maturity. There were significant negative correlations between the anadromy scores and both the length of the outlet rivers of the different lakes and a migration barrier index for the different watercourses (combining migration distance and water velocity). It is hypothsized that these correlations were due to differences in energy expenditure for charr during upstream migration and/or differences in predation pressure on charr during river migration. Short rivers with relatively high water velocity seem to be the most preferable conditions for the anadromous life‐history strategy. There were no correlations between the degree of anadromy and mean river slope or minimum summer water discharge.
Behavioral interactions between black mudfish (Neochanna diversus Stokell, 1949: Galaxiidae) and mosquitofish (Gambusia affinis Baird & Girard, 1854)a
Authors: Barrier R. F. G. , Hicks B. J. 
Published: July 2006

AbstractThe behavior of black mudfish (Neochanna diversus Stokell, 1949: Galaxiidae) and mosquitofish (Gambusia affinis Baird & Girard, 1854: Poeciliidae) was investigated in laboratory tanks. Black mudfish are indigenous to northern New Zealand, and mosquitofish are introduced; both species are sympatric in wetlands in the Waikato region. By comparing position, feeding rates and aggressive behavior of both species, we found that black mudfish were increasingly able to compete with mosquitofish as they grew from fry to adults. Mosquitofish were more aggressive towards mudfish fry and juveniles than were these two life stages towards mosquitofish, but adult mudfish were aggressive towards mosquitofish. Both small (18–24 mm total length (TL)) and large mosquitofish (25–36 mm TL) showed high aggression towards mudfish fry (13–18 mm TL), and fry were eaten by large mosquitofish. However, 3 interspecific differences appear to allow coexistence of these two species. Firstly, mudfish reproduce in winter, whereas mosquitofish reproduce in summer, resulting in mudfish fry being present when mosquitofish are at their lowest abundance. Secondly, mudfish can survive in seasonally dry habitats by aestivation, while mosquitofish cannot. Thirdly, adult black mudfish are nocturnal, whereas mosquitofish are primarily diurnal.
Growth patterns of the otoliths of Stellifer rastrifer (Pisces: Sciaenidae) from the Sergipe River estuary (Sergipe, Brazil)
Authors: Morales‐Nin B. 
Published: July 2006

Abstract Stellifer rastrifer (Sciaenidae) from the Sergipe River (Brazil) sagittal otoliths show a microstructure that is common to many fish, with microincrements of growth made up of continuous and discontinuous units. The microincrements show thickness and structure variations, which apparently correspond with the rings seen at the macrostructural level.
Brook trout (Salvelinus fontinalis) population dynamics and mottled sculpin (Cottus bairdi) occurrence in relation to acidic episodes in streams
Authors: Carline R. F. , Gagen C. J. , Sharpe W. E. 
Published: July 2006

AbstractWe monitored water chemistry and populations of brook trout (Salvelinus fontinalis) and mottled sculpins (Cottus bairdi) in 5 streams and some tributaries to determine how the severity of acidic episodes (low pH and high Al) influenced density and distribution of these species. Among streams, Linn Run had the lowest pH (4.8) and highest concentrations of total dissolved Al (>400 μg‐l−1) during periods of high discharge. Densities of brook trout and mottled sculpins were low in Linn Run, but high in tributaries, where pH (6.5) and Al (30 μg‐l−1) remained well below lethal levels. Among the other streams, brook trout density was highest where the acidic episodes were least severe and the density of age‐0 brook trout was lowest when precipitation during the early months of the year was above normal. Immigration of brook trout from downstream areas maintained populations in the stream segments subjected to severe episodes. Mottled sculpins were not found in streams with severe episodes.
Observations on a foraging association between two freshwater stream fishes
Authors: Baker J. A. , Foster S. A. 
Published: July 2006

AbstractOn 3 occasions during summer 1977, small groups of a typically run‐ and pool‐dwelling minnow (blacktail shiner,Cyprinella venusta) were observed feeding in a shallow riffle on items dislodged by foraging northern hog suckers (Hypentelium nigricans). Although such nuclear‐attendant following behavior has been documented in marine systems and has been reported from some African freshwater lakes, descriptions from freshwater streams are rare. We describe the interaction and consider the probable development of the search behaviour of the blacktail shiners. We also explore the possible benefits of searching for hog suckers in small groups, as observed, rather than as individuals or in large groups. This feeding strategy may be an important mechanism of food acquisition for some individuals when usual resources are scarce.
Intra‐cohort cannibalism among larval stages of perch (Perca fluviatilis)
Authors: Brabrand A. 
Published: July 2006

AbstractCohorts of perch larvae, hatched within 24 h, developed into a bimodal body size distribution as early as 6 days after commencement of external food uptake. At this development stage, intra‐cohort cannibalism occurred among larval perch individuals of larval stage V (body size: 10.5±0.26 mm, 95% c. l.) on smaller siblings. In experimental trials the consumption rate (C: no. of prey/predator·hour) increased exponentially with size of predatory perch (L: mm) and at 21°C was expressed by the relationship log C=3.406·log L‐3.848 (n=10, r2=0.98, P<0.001). For predatory perch in larval stage V, consumption rate was reduced when Daphnia pulex were added, while not in later stages. Perch larvae experimentally forced to live as true piscivores without additional food items developed from stage V to stage IX (15.8±1.34 mm) within the same time as those fed on Daphnia alone, but with increased mortality.
Predation as a determinant of size structure in populations of crucian carp (Carassius carassius) and tench (Tinea tinea)
Authors: Brönmark C. , Paszkowski C. A. , Tonn W. M. , Hargeby A. 
Published: July 2006

AbstractPredation is an important structuring force in many fish assemblages and may have large, direct lethal effects on prey fish populations but also may affect growth rate and survival indirectly through shifts in behavioral patterns. Some species appear more sensitive to predation and earlier studies in a limited set of Finnish ponds suggests that crucian carp (Carassius carassius) is very sensitive to predation, which results in changes in population size‐structure and density. In this study we tested the effect of piscivore presence or absence on crucian carp populations by using data from a large number (>600) of Swedish lakes across a wide geographical area and ranging in size from small ponds to large lakes (0.02–4400 ha). We also included a second species, tench (Tinea tinea), in our analyses. The population size structures of crucian carp and tench were clearly related to the presence or absence of piscivores. In lakes and ponds without piscivores. populations were dominated by small‐bodied individuals. When piscivores were present, populations consisted almost exclusively of large individuals. Densities of crucian carp and tench were much higher in ponds and lakes without piscivores. There were no differences in size structure or relative abundance when catches from electrofishing were compared with gill net catches, suggesting that our results are not an effect of a behavioral shift in the presence of piscivores.
Longevity of longfinned eels Anguilla dieffenbachii in a New Zealand high country lake
Authors: Jellyman D. J. 
Published: July 2006

AbstractA sample of 146 longfinned eels (Anguilla dieffenbachii), ranging in length from 231–1203 mm, was collected from Lake Rotoiti, Nelson Lakes National Park, New Zealand. Otoliths (n= 114) of eels were difficult to read, mainly due to the considerable age (maximum age 106 years). Growth rate was slow and linear, averaging 9 mm. year−1. These are the slowest growth rate and maximum age from any study of Anguilla spp. to date. Lakes within National Parks provide the largest commercially unfished waters within New Zealand and hence provide reserve breeding stocks of longfinned eels; however, the average generation time of 93 years for female eels from Lake Rotoiti implies that stock management should be conservative.
Effects of season, maturity, and sex on lipid class dynamics in largemouth bass (Micropterus salmoides Lacepede)
Authors: Brown M. L. , Murphy B. R. 
Published: July 2006

AbstractAbstract Factors that can influence changes in lipid class concentrations in specific tissues have not been reported for largemouth bass Micropterus salmoides. We investigated patterns of lipid composition by measuring seasonal levels of total lipid and major lipid classes in the muscle and liver tissues of juvenile and adult largemouth bass and gonad tissue of adults. Fish were collected in December, February, April and July to correspond with key stages of the sexual cycle. Total lipid concentrations were substantially greater in hepatic (32.8 [female] to 56.6 [male] mg. g−1) and gonadal tissues (34.4 [F] to 204.0 [M] mg. g−1) than in muscle (7. 5 [F] to 11.4 [M] mg. g−1). Muscle lipid concentrations in juveniles were significantly higher (10.9 [F] and 11.4 [M] mg. g−1) in summer than in winter in adult muscle tissue (8.6 [F] and 9.4 [MI mg. g−1). A 44% increase in ovary lipid was observed from preparatory to prespawn stages, followed by a 78% decline after the spawn. Additionally, seasonal hepatic lipid concentrations were substantially higher in juveniles. Concentrations of lipid classes (free cholesterol [C], triacylglycerol [TAG], free‐fatty acids [FFA], esterified cholesterol [CE] and phospholipid [PL]) of all tissue types varied significantly among season, sex, and maturity categories. Changes with all lipid classes in the ovary coincided with those occurring in total ovarian lipid. Mobilization and transport of TAG and PL from the liver to the ovary appeared to occur during gametogenesis. All class concentrations in juveniles were invariably higher in liver than in muscle, but seasonally variable among hepatic and gonad tissues of adults. Juvenile males showed slightly greater hepatic C concentrations than other groups. Muscle and hepatic C were generally higher in juveniles.
Density of juvenile brown trout and Atlantic salmon in natural and man‐made riverine habitats
Authors: L'Abée‐Lund J. H. , Heggberget T. G. 
Published: July 2006

AbstractThe density of juvenile brown trout (Sulmo trutta L.) and Atlantic salmon (Salmo salar L.) was significantly higher along river bank areas protected against erosion than along natural river banks in the River Gaula, Central Norway. A habitat shift appeared in Atlantic salmon, and a behavioural shift was demonstrated by brown trout from August October. The effect of habitat on densities of juvenile salmonids should be taken into account as mitigation measures on eroded river banks and when assessing fish production in rivers.