bluuebunny/crossref_metadata_2025 huggingface dataset:
Estimation of fish activity costs using underwater video cameras
Authors: Trudel M. , Boisclair D.
Published: April 2005

Swimming speed and activity costs of dace (Phoxinus eos × P. neogaeus) were estimated in the field using underwater video cameras. Activity costs were estimated by converting swimming speeds and the number of movements into swimming costs. Average swimming speed ranged from 6.7 to 12.2 cm.s−1 across 2 h periods and varied significantly among dates and time of day. The time spent swimming by dace ranged from 616 to 17 640 s 2 h−1. Activity costs per 2h period ranged from 2.1 to 4O.2J 2h−1 and were strongly correlated to the time spent swimming. Daily activity cost estimated using the cameras averaged 128.9J day−1 and was equivalent to 1.7 times the standard metabolic rate. Activity cost predicted using a bioenergetic model in conjunction with independent estimates of consumption and growth rates averaged 138.8J day−1. This study indicated that swimming characteristics and activity costs of dace varied significantly both within and among days. These analyses also indicated that equally valid activity costs for fish in the field can be estimated using video cameras and the difference between Consumption and growth rates.
Richness and diversity of helminth parasite communities in the common carp and in three more recently introduced carp species
Authors: Kennedy C. R. , Pojmanska T.
Published: April 2005

It can be predicted that common carp Cyprinus carpio, as an introduced species, would harbour poor helminth infra‐communities but that these would nevertheless be richer than those in three other species of carps introduced into Europe in recent decades. These predictions were tested by comparing the helminth infra‐communities of common carp, Ctenopharyngodon idella, Hypophthalmichthys molitrix and Aristichthys nobilis reared under similar conditions in a fish farm. Data were presented on species richness of total helminth infra‐communities, and on richness and diversity of gill, eye and intestinal infra‐communities separately. These confirmed that common carp helminth infra‐communities were poor and that they were no richer than those of the three other species of carp. This situation in the farm was considered to be representative of the situation in natural habitats in Europe. It is suggested that the poor infra‐communities in common carp reflect the facts that their helminth communities are composed mainly of specialists, that they are not readily susceptible to invasion by specialists of other fish hosts and that, as introduced species, they have not had sufficient time to acquire many generalist helminths from native species of fish. The difference in time between the introduction of common carp into Europe centuries ago and the introduction of the other three species of carps decades ago is not sufficient to produce any significant differences in the richness and diversity of their helminth infra‐communities.
The effects of species manipulation on growth and survival of an assemblage of juvenile estuarine fish
Authors: DUNSON W. A. , ROWE C. L.
Published: April 2005

Growth and survival of Cyprinodon variegatus, Fundulus heteroclitus, Menidia beryllina, and Lucania parva, held in combination with an omnivorous grass shrimp–Palaemonetes pugio, and a predatory diving beetle Tropisternus lateralis, were measured at 12–60% in outdoor static microcosms that simulate salt marsh ponds. We predicted that the low species richness of this abiotically harsh but highly productive habitat would lead to a high degree of interaction among species. The presence of the beetle had no effect on the fish or the shrimp. Removal of the shrimp similarly had no detectable effect on the fish. There was a trend in proportions of survival among three fish: C. variegatus>F. heteroclitus>M. beryllina. Survival of M. beryllina was greater when it was alone at low densities of its own species (333 v. 667 fish m −3), and less when it was paired with F. heteroclitus. Interactions with other species diminished the growth of M. beryllina. Survival of F. heteroclitus was greater when it was alone at low density (333 m −3), than when the same number were placed together with Menidia and Cyprinodon at a total fish density of 999 m −3. There were no effects of removal of other species on survival or growth of C. variegatus at either 12′5 or 24%. This study showed that a complex array of interactions occurred among six common members of a salt marsh food web, but the degree of interaction Was less than We predicted.
Trychophrya intermedia on the gills of rainbow trout acclimating to low ambient pH
Authors: Balm P. H. M. , Carrick T. R. , Coenen A. J. M. , POTTINGER† T. G.
Published: April 2005

Rainbow trout under low pH conditions acquire heavy infections with Trychophrya intermedia, not secondary to gill damage, which suggests that the parasite may have a primary effect on gill function in fish Under acid Conditions.
High incidence of Atlantic salmon × brown trout hybrids in a Lake District stream
Authors: Hartley S. E.
Published: April 2005

Hypervariable minisatellite DNA single‐locus profiling and mitochondrial DNA analysis revealed that 18.48% of juvenile Atlantic salmon Salmo salar in Troutbeck, a stream in the R. Leven catchment of the English Lake District, were hybrids between Atlantic salmon and brown trout S. trutta, and that hybridization was bidirectional.
Maturation patterns in female European eel: age and size at the silver eel stage
Authors: Svedaung H. , Neuman E. , Wickström H.
Published: April 2005

The maturation pattern in the female European eel Anguilla anguilla was studied by investigating age and size patterns of silver eels in different aquatic environments in Sweden, covering limnic, brackish and marine waters. The results neither supported the hypothesis that there is a critical size or age when eels enter the silvery stage, nor that size and age at maturity are positively related. Age at maturity, however, was observed to be negatively related to growth rate in all localities, i.e. the female reproductive tactic apparently is to become sexually mature at the earliest possible opportunity. Furthermore, it was recognized that a significant amount of variation was due to habitat differences, since the female eel maturation pattern deviated systematically between sampling sites, as it did also when the effect of growth rate was eliminated. Thus, the ability of the female eel to adjust maturation to an optimal size and age can be questioned, because the panmictic nature of the eel means local adaptations are unlikely Growth rate dependent differences suggest that variations in maturation patterns between eel environments are linked more to the opportunity for nutrient accumulation than to other aspects of growth.
Genetic differentiation among Danish brown trout populations, as detected RFLP analysis of PCR amplified mitochondrial DNA segments
Authors: Hansen M. M. , Loeschcke V.
Published: April 2005

An initial screening with 18 restriction endonucleases of brown trout mitochondrial DNA from three regions of Denmark revealed no variation in the D‐loop while seven restriction endonucleases were found to detect variability in the NADH‐dehydrogenase 1 and/or 5/6 regions. Thirteen different haplotypes were observed, fewer in the Lake Hald populations than in the other samples, probably a result of nonexisting gene flow due to an impassable dam. No correlation was found between geography and the genetic relationships among haplotypes. Significant genetic differentiation was observed among the three main regions. Genetic differentiation among populations was much more pronounced in the Lake Hald than in the Bornholm region. The genetic relationships among populations of the Lake Hald region suggested by mtDNA data were not in accordance with allozyme data and the known history of the populations, while estimates of genetic differentiation and gene flow inferred by the two methods were in agreement. (c) 1996 The Fisheries Society of the British Isles
Pike and red swamp crayfish: a new case on predator‐prey relationship between aliens in central Spain
Authors: Elvira B. , Gnicola G. , Almodovar A.
Published: April 2005

Pike in the Ruidera Lakes (central Spain) chiefly ate the recently introduced crayfish Procambarus clarkii. It was the dominant prey in occurrence, number and biomass for every size class and season. Likewise, number (up to 27) and total weight of ingested crayfish were directly related with pike size. The principal prey fish were all introduced species (except the endangered Blennius fluviatilis), most native species having disappeared since pike were introduced in 1953. (c) 1996 The Fisheries Society of the British Isles
Blood rheology of Antarctic fishes: viscosity adaptations at very low temperatures
Authors: Egginton S.
Published: April 2005

Viscosity of whole blood and plasma from Antarctic fishes were compared over a temperature range of −1.5 to 5°C; human samples and water provided reference values. Blood viscosity of nototheniids was greater than that of the haemoglobinless icefish, reflecting differences in packed cell volume, being 5.27 v. 3.27 cP at 0°C for Notothenia coriiceps and Chaenocephalus aceratus, respectively. The reduction in MCHC, rather than haematocrit, in nototheniids suggests that selection pressure has not acted at the level of oxygen transport. However, icefish plasma viscosity was similar to human, but greater than that of Notothenia spp., suggesting that viscometric influences on cardiac afterload may be adaptive for the latter. Indeed, handling stress induced a significant increase in viscosity of both whole blood and plasma which may impair cardiovascular performance. Such a response was not observed in icefish, and in view of the large blood vessels it is unlikely that viscosity plays any significant role in limiting activity of this species.
Duration of synchronous cleavage cycles and rate of development at different temperatures in the Baltic herring
Authors: Saat T. , Veersalu A.
Published: April 2005

The duration of one synchronous cleavage cycle (τ0) in Clupea harengus membras at different temperatures (T) was given by: (logτ0)= 2.4349–0–0684T for T= 0.9–13°C, and (logτ0)= 1.61010–oooit for t= 13–18–7°C.
Electromyograms from radiotelemetry as indicators of reproductive activity in lake trout
Authors: Kaseloo P. A. , Weatherley A. H. , Ihssen P. E. , Anstey D. A. , Gare M. D.
Published: April 2005

One male and one female lake trout, Salvelinus namaycush, were held in a laboratory tank simulating a natural spawning environment. Their behaviour during their reproductive period was videotaped each day for 2 h at dusk. The fish activities were classified into seven types: resting, casual swimming, side‐thrusting, chase, chase‐nudge, body alignment, shuddering. As the reproductive period progressed the fish became more generally active with a marked increase in interactive behaviours such as pursuit of the female by the male (chasing, chasing‐nudging). Around spawning time, shuddering and body alignment activity reached apeak. Each fish was equipped with an internally implanted radiotelemetry package able to detect and transmit continuously over the course of each day signals that reflect production of the electromyograms (EMGs) that accompany fish axial muscle activity (high muscular activity gives low pulse interval times in milliseconds). The lowest EMG pulse intervals corresponded with what, from the video records, appeared to be the time of highest physical activity during the reproductive period–viz. that associated with spawning activity during dusk. Other times during the diel cycles over the reproductive period, except for times of roughly similar duration during early morning (which may also be reflections of spawning) showed considerably lower muscular activity. It is concluded that transmitted EMG records could probably be used as indicators of spawning activity of lake trout in at least some of those places in the field where they cannot normally be located by visual means.
Spatial and temporal distributions of salmonids in two ponds in Newfoundland, Canada
Authors: O'Connell M. F. , Dempson J. B.
Published: April 2005

Spatial and temporal distributions of salmonids were examined in Junction Pond, Northeast River, Placentia and Conne Pond, Conne River, Newfoundland using Lundgren multiple‐mesh experimental gillnets. Both ponds contain populations of Atlantic salmon and brook trout with Junction Pond also possessing brown trout and resident Arctic charr. For salmon parr there was a significant month effect in distribution of catch rates in both ponds, and in Junction Pond, there was a significant diel effect. There was also significant variation in catch rates by lentic zone. For brook trout, there was a significant lentic zone × month interaction in Junction Pond; in Conne Pond, the main effects lentic zone and month were significant. Highest benthic catch rates of Atlantic salmon parr occurred in the littoral zone of both ponds. Most captures of brook trout also occurred benthically in both ponds; similar to salmon parr, littoral zone catch rates were higher than those of the deeper benthic area in Conne Pond but the reverse was true for Junction Pond. For both salmon parr and brook trout, the deeper benthic area and the pelagic area were relatively important rearing habitats in each pond. The distribution of catches for brown trout (few in number relative to the other species) in Junction Pond was similar to that of brook trout while Arctic charr were found mainly pelagically. Within the benthic area, most Arctic charr were caught at depths beyond the littoral zone. There was a tendency for Altantic salmon parr and brook trout found in the deeper benthic area and the pelagic area to be significantly larger and older than those in littoral zone in each pond. Sizes of Arctic charr did not differ significantly among lentic zones.
Plectorhinchus mediterraneus from off north east Italy and Slovenia–the first records of fish of the family Haemulidae from the Adriatic Sea
Authors: Llpej L. , Spoto M. , Dulcic J.
Published: April 2005

The haemulid Plectorhinchus mediterraneus, previously unrecorded in the Adriatic Sea, has been found recently in the Gulf of Trieste, in Diga Rizzo, Italy, and near Piran, Slovenia.
Prey orientation in piscivorous brown trout
Authors: L'Abée‐Lund J. H. , Aass P. , Sægrov H.
Published: April 2005

Piscivorous brown trout Salmo trutta change their feeding behaviour depending on prey species, prey size and number of prey eaten. In trout which had eaten fish recently, most had one fish in their stomach, but up to 16 prey fish were found. Individuals of the small‐sized minnow Phoxinus phoxinus were swallowed chiefly tail first, whereas individuals of the larger Arctic charr Salvelinus alpinus were taken both head and tail first. The largest charr were swallowed head first. In stomachs containing more than one fish prey, prey orientation was likely to be mixed. For all three types of prey orientation (i.e. tail first, head first and mixed), significant and positive correlations existed between prey length and predator length. The maximum prey size eaten tail first or in mixed orientation was about 70–85% of the size of prey eaten head first, indicating morphological advantages in eating the prey head first.
Sex differences in the trade‐off between feeding and mating in the guppy
Authors: Griffiths S. W.
Published: April 2005

Male guppies Poecilia reticulata court almost continuously and often indulge in sneaky mating attempts. Female guppies, on the other hand, devote much of their time to foraging. This paper demonstrates that both sexes reduce their feeding rate in mixed‐sex groups relative to single sex ones and suggests that the decrease is less pronounced for females than for males. Thus males make feeding and mating decisions that are dependent on hunger while female foraging behaviour is constrained by sexual harassment. The observed sex differences in behaviour are a consequence of asymmetrical mating costs in males and females.
Morphological changes induced by acclimation to high pressure in the gill epithelium of the freshwater yellow eel
Authors: Dunel‐Erb S. , Sébert P. , Chevalier C. , Simon B. , Barthélémy L.
Published: April 2005

After acclimation either to high pressure (101 ATA) or to low temperature (9°C), the number of mucous cells within gill epithelium of freshwater eel Anguilla anguilla was significantly decreased and the density of chloride cells was significantly increased when compared to control fish (1 ATA, 19°C).
Population dynamics of Gila trout in the Gila River drainage of the south‐western United States
Authors: Propst D. L. , Stefferud J. A.
Published: April 2005

In some small, often unstable, streams of the Gila River drainage, New Mexico, Gila trout Oncorhynchus gilae populations fluctuated numerically seasonally and annually. Few differences were noted in length‐weight and size‐structure comparisons, but Fulton condition index varied significantly. Time of sample and time since disturbance (natural or human‐caused) were often associated with differences in condition. Other factors may include availability of prey, cannibalism, and reproductive condition. The repeatedly sampled McKnight Creek population illustrated the resilience of Gila trout populations to natural disturbances. A scouring flood in 1988 caused a >90% reduction in numbers, but, by 1992, population structure was not substantially different from that of other streams. Likewise, juvenile/adult ratio, density, and per cent large specimens (≥ 200 mm total length) of most other samples were within the ranges for the McKnight Creek population. Gila trout density (no. fish min−1 electrofishing) tended to increase with higher elevation and greater drainage density (stream km catchment−1 km−2) but decreased with larger catchments. Information gained in this study demonstrates that a variety of factors must be considered when evaluating the relative well‐being of Gila trout populations and illustrates the importance of larger, more hydrologically complex drainages to the long‐term survival of Gila trout populations.
Stocking success of Scottish Atlantic salmon in two Spanish rivers
Authors: Verspoor E. , De Garcia Leániz C.
Published: April 2005

A previous analysis of proportions of stocked and wild Atlantic salmon among angled fish in the Rivers Asón and Nansa in northern Spain based on the analysis of MEP‐2* genotypes is extended. The results reinforce the initial conclusion that returns of stocked Scottish salmon are significantly lower than returns for wild fish.
Cyto‐histological examination of post‐vitellogenesis and final oocyte maturation in captive‐reared striped bass
Authors: Mylonas C. C. , Woods L. C. , Zohar Y.
Published: April 2005

The ovarian development of captive‐reared, striped bass Morone saxatilis was examined during a 10‐week period encompassing the spawning season. Vitellogenic oocytes in March had a mean diameter of 838 ± 18 μm and did not grow significantly thereafter. Except from one non‐hormone‐treated fish, all females failed to undergo final oocyte maturation (FOM) and their ovaries became atretic with the onset of high spring temperatures. A clearing fixative was found useful in identifying early stages of atresia, evident by the absence of the germinal vesicle (GV). Final oocyte maturation of fish treated with gonadotropin‐releasing hormone agonist (GnRHa) consisted of two phases. Early FOM lasted from 1 to 3 weeks, and was associated with lipid‐droplet coalescence, and displacement of the GV and yolk globules to the peripheral cytoplasm. Late FOM lasted <24h, and consisted of yolk‐globule coalescence and GV breakdown (GVBD). Ovulated eggs had completely coalesced lipid and yolk masses, with cortical alveoli lined against the cell wall. Both phases of FOM were associated with significant increases in oocyte diameter. Striped bass oocytes showed important morphological differences compared to oocytes of other members of the Moronidae family, in terms of percentage lipid content, chorion thickness and degree of hydration after ovulation.
Rainbow trout responses to water temperature and dissolved oxygen stress in two southern California stream pools
Authors: Matthews K. R. , Berg N. H.
Published: April 2005

Habitat use by rainbow trout Oncorhynchus mykiss is described for a southern California stream where the summer water temperatures typically exceed the lethal limits for trout (>25°C). During August 1994, water temperature, dissolved oxygen (DO), and trout distribution were monitored in two adjacent pools in Sespe Creek, Ventura County, where summer water temperature reached 28.9° C. Water temperature was an important factor in trout distribution in the two pools. During 1–11 August 1994, water temperatures in pool 1 ranged from 21.5°C at the bottom (4.1 m) to 28.9° C at the surface. After 5 August, trout were no longer found in this pool, suggesting that trout had moved out of the high temperature water or died. In the adjacent, shallower (1.5m) pool 2, surface water temperatures were as high as 27.9° C, but temperatures on the bottom remained cooler (17.5–21° C) than pool 1, presumably due to groundwater seeps. Consistent aggregations of trout were observed in pool 2 throughout the study period. During the day when water temperature was highest, most trout were found in a region of the pool with the lowest water temperature (mean=18.3° C). Conversely, regions with the highest water temperatures had the fewest trout during the day. The seeps may have introduced water with low dissolved oxygen into pool 2, as the DO in many locations on the bottom ranged from <1 mg 1−1 to 5 mg 1−1 over 24 h, while the surface DO ranged from 4.1 to 10.0mg 1−1. Lowest DO occurred from 2400 to 0600 hours. During August, water temperature and DO were positively related. Thus, rainbow trout faced a trade‐off between the relatively cool water temperature with low, possibly lethal levels of DO (e.g. 1.7 to 3.4 mg 1−1 in region 3), and lethally high water temperature but high DO. Seeps may serve as important thermal refugia for trout, and an increased understanding of their role as potential critical refugia in Southern California is necessary.
Cardio‐respiratory function in carp exposed to environmental nitrite
Authors: Williams E. M. , Nelson J. A. , Heisler N.
Published: April 2005

Continuous monitoring of heart rate, breathing episodes and blood pressure showed that the cardio‐respiratory response of carp exposed to nitrite (water concentration, 1 mmol l−1) changes with length of exposure. The animals developed a severe methaemoglobinaemia over the first 24 h of nitrite exposure. The minor changes in plasma HCO3− and lactate concentration, suggest that the observed hyperventilatory response was sufficient to maintain aerobic metabolism throughout most of the body during this time. During the second 24‐h period, the rate of breathing increased further and short periods of bradycardia and hypotension were seen. Over this latter period, the animals increased their use of anaerobic metabolism as illustrated by the mean 48 h blood lactate concentration of 4.8mmol 1−1, a greater than 10‐fold increase over pre‐exposure values. The increase in blood lactate was accompanied by the predicted metabolic acidosis, however, an alkalosis of respiratory origin and buffering combined to keep the plasma pH absolutely stable throughout the study. This study shows that as the blood oxygen supply is reduced through the development of methaemoglobinaemia, cardio‐respiratory compensation by the carp is probably adequate to maintain tissue oxygenation for short periods of nitrite exposure. However, as nitrite exposure proceeds past 24 h, the animals progress into a positive feedback cycle where the high cost of additional ventilation rapidly accelerates their oxygen deficit which cannot be repaid, because <25% of their haemoglobin is available for oxygen binding. Additionally, our data demonstrate a circadian rhythm of physiological response to nitrite and contradict the hypothesis that catecholamine release promotes CO2 retention in water breathing animals.
Habitat, reproductive biology and size composition of Parequula melbournensis, a gerreid with a temperate distribution
Authors: Sarre G. A. , Hyndes G. A. , Potter I. C.
Published: April 2005

Trawling was carried out over sandy substrates in the shallow (5–15m) and deeper (20–35m) waters of four regions along 250 km of the lower west coast of Australia, during seven consecutive seasons. This yielded 32 752 individuals of the gerreid Parequula melbournensis, which constituted c. 42% of the total number of fish. Densities of P. melbournensis were greatest in the most southern region, reaching a seasonal maximum of 835 fish ha−1: at one site in that region. Since P. melbournensis is restricted largely to the southern coastline of Australia, it has a temperate rather than subtropical or tropical distribution and thus is not a typical gerreid. Furthermore, unlike most other gerreids, it does not spend part of its life cycle in either estuaries or nearshore marine waters. The maximum total length of P. melbournensis was 175 mm, with the length at maturity (L50) being 115 mm in females and 121 mm in males. No clear monthly trends were exhibited by gonadosomatic indices, the prevalence of mature ovaries and the oocyte size‐frequency distributions of female P. melbournensis, and no clear and consistent modes were observed in length‐frequency data for this species. These strong indications that spawning occurs throughout the year were substantiated by the occurrence of post‐ovulatory follicles in the ovaries of large fish in all months but August, and by the presence in that month of advanced yolk granule oocytes in some ovaries, which implies that spawning was imminent. The spawning of P. melbournensis throughout the year contrasts with the far more restricted spawning periods recorded for other teleosts in the same temperate Australian waters. In this respect, P. melbournensis exhibits the characteristics of the essentially tropical family to which it belongs. Annuli, which could be detected on the otoliths of c. 40% of fish, suggest that the majority of P. melbournensis Were <3 years old.
Temperature and efficiency of development during endogenous feeding in herring embryos and yolk‐sac larvae
Authors: Overnell J.
Published: April 2005

Oxygen uptakes, dry weights and energy contents of herring Clupea harengus were measured periodically from the time of egg fertilization to the end of the yolk‐sac stage (without added food). Temperature of incubation (3·5–17° C) had little effect on efficiency of conversion of egg reserves to body material.
Small male mating advantage and reversed size dimorphism in poeciliid fishes
Authors: Bisazza A. , Pilastro A.
Published: April 2005

Despite interspecific differences in the absolute efficiency rate of copulatory thrusting in Poecilia reticulata, Phalloceros caudimaculatus, Heterandria formosa, Girardinus falcatus and Gambusia holbrooki small males had a significant advantage. These differences are discussed in the light of the interspecific differences in morphology and sexual behaviour. The results of the present study offer an alternative explanation for the pronounced reversed size dimorphism observed in this family of fishes. The greater efficiency of small males in achieving matings when females are unreceptive might also explain why genetically small males are maintained in natural populations of many poeciliids, in spite of the large size advantage in both intrasexual competition and female choice.
Homing movements of displaced stream‐dwelling brown trout
Authors: Armstrong J. D. , Herbert N. A.
Published: April 2005

In April and May of 1993, 12 of 14 brown trout (202–288 mm), tagged with radio transmitters and displaced over 800–3600 m in a natural river system, returned to the areas from which they were captured. Homing was generally directed and rapid (up to 1·22 body lengths s−1 against the flow). Homing commenced within 65 min of displacement for four of five trout displaced downstream, and within 4 days for those displaced above the confluence of a home tributary burn with the main stem of the river.
Density‐dependent growth and sexual maturity of silver hake in the north‐west Atlantic
Authors: Helser T. E. , Almeida F. P.
Published: April 2005

Stock abundance was the most important predictor of sexual maturation of age 2 and 3 silver hake in the north‐west Atlantic between 1973–1990. Growth at ages 1 and 2 in the southern stock was significantly and negatively correlated with stock abundance (r2>0.56, P<0.01). Sexual maturity may be mediated through competition and growth during the first and second years of life. In the northern stock, growth and stock abundance was not significantly correlated (P>0.05). Here, increased sexual maturity at ages 2 and 3 during 1973–1990 may have occurred without increased somatic growth, already near its maximum, due to the relatively cooler water temperatures of the Gulf of Maine. Logistic regression models indicated that maturation is dependent on age, stock density and an age‐density interaction.
Sex differences in resource utilization by the peacock blenny
Authors: Gonçlalves E. J. , Almada V. C.
Published: April 2005

This paper presents data on the seasonal variation of gonadosomatic, hepatosomatic and feeding indices in nesting males, females and female‐like males of the blenniid fish Salaria pavo. Eviscerated condition factors, female fecundity and feeding rates are also presented. The results are consistent with the hypothesis that females maximize their feeding rates during reproduction, converting food into eggs through repeated spawning. Nesting males feed at a very low rate during the breeding season. It is argued that one major component of the reproductive costs in these males is the reduction of feeding opportunities. Female‐like males present lower reproductive costs, which probably reflects the compromise between fertilizing some eggs and growing.
The critical swimming velocity of diploid and triploid brook trout
Authors: Stillwell E. J. , Benfey T. J.
Published: April 2005

No significant difference was found in the critical swimming velocity of diploid and triploid brook trout Salvelinus fontinalis, suggesting that the triploid state is not associated with a reduced aerobic capacity.
A non‐invasive morphometric technique for estimating cestode plerocercoid burden in small freshwater fish
Authors: Barber I.
Published: April 2005

A non‐invasive morphometric technique is presented which can be used to predict the infection status and the proportion of infected fish weight contributed by parasite tissue in three‐spined sticklebacks Gasterosteus aculeatus infected with plerocercoids of Schistocephalus solidus (Cestoda: Pseudophyllidea)
Strontium in scales verifies that sympatric sea‐run and stream‐resident brown trout can be distinguished by coloration
Authors: Eek D. , Bohlin T.
Published: April 2005

The strontium content in scales of exceptionally large resident‐coloured individual brown trout in a small stream was not higher than in smaller residents and well below the Sr content of scales from sympatric sea migrants. Therefore, it is concluded that adult migrants and stream residents can be distinguished safely by their coloration.
Khawia sinensis (Cestoda: Caryophyllidea)—;an indicator of legislative failure to protect freshwater habitats in the British Isles?
Authors: Yeomans W. E. , Chubb J. C. , Sweeting R. A.
Published: April 2005

Khawia sinensis is an easily identified carp tapeworm first recorded in the British Isles in 1986. The range of the parasite has extended greatly, despite legal prohibition of the introduction and movement of infected fish. Using the spread of K. sinensis as a model, it is concluded that regulation resulting from this legislation cannot be reliable because there is no total ban of imports of potentially infected fishes, nor an effective procedure for preventing translocation of infected hosts.
Genetic divergence at the synaptophysin (Syp I) locus among Norwegian coastal and north‐east Arctic populations of Atlantic cod
Authors: Fevolden S. E. , Pogson G. H.
Published: April 2005

Several nuclear RFLP loci have been discovered recently that exhibit extensive allele frequency variation among Norwegian coastal and north‐east Arctic populations of Atlantic cod Gadus morhua. One of these polymorphisms was detected by hybridizing an anonymous cDNA clone (GM798) against genomic DNA digested with the restriction enzyme DraI. This cDNA clone has now been sequenced and identified as synaptophysin (Syp I), an integral synaptic vesicle membrane protein. Primers were constructed that amplify an intron of the Syp I gene that is polymorphic for the DraI site, thus making it possible to use a PCR‐based assay to score the polymorphism. A total of 965 individuals sampled from the Barents Sea, coastal areas and fjords in northern Norway have been analysed for this polymorphism. The results confirm that highly significant differences exist between NE Arctic and coastal cod at the Syp I locus. A cluster analysis revealed a deep split between coastal and Arctic populations and hierarchical F‐statistics indicated that about 40% of the total variation was attributable to differences between Arctic and coastal groups. The temporal stability of allele frequencies was assessed by comparing Syp I allele frequencies among samples of juveniles (0 group) captured at specific locations in fjords in consecutive years and among samples of adults and juveniles collected from the same fjord. Samples of juveniles collected in 1994 and 1995 in Malangen were genetically indistinguishable whereas juveniles sampled from Dønnesfjord and Ullsfjorden over the same 2‐year period exhibited significant differences. Adults and 0‐group individuals collected from the same fjord were found to be genetically indistinguishable in Malangen, but not in Balsfjorden. In addition to detecting large differences among Arctic and coastal groups, the Syp I locus suggests that genetic heterogeneity exists among resident populations of cod in different fjords and that gene flow among populations throughout northern Norway may be considerably lower than previously believed.
Acoustic behaviour of Abudefduf luridus
Authors: Santiago J. A. , Castro J. J.
Published: April 2005

Adult males Abudefduf luridus produced sounds during aggressive interactions, although not all aggressive interactions were associated with sounds. Such sounds were always related to characteristic swimming movements during an aggressive display or territorial defence. The sound was a combination of several sonic pulses, with most energy concentrated towards the low end of the spectrum (from <50 to 800 Hz), and was most frequently groups of two pulses. Analysis of the pulse structure suggested that these sounds are produced by muscles acting on the swimbladder. However, the mechanism of sound production has yet to be demonstrated. Sounds were emitted throughout the 24‐h period with increased activity at sunrise and sunset.
Photomicrographic atlas of Atlantic herring embryonic development
Authors: Hill J. , Johnston I. A.
Published: April 2005

The development of the Atlantic herring is related to a staging series intended to provide a standard background for studies of herring embryonic development. The series is based on herring embryos from the Isle of Man (Irish Sea) stock reared at 8°C. The stages are named rather than numbered in order to simplify usage and the series has been sub‐divided into five periods: zygote and cleavage, blastula, gastrula, segmentation, and organogenesis.
Minnows become nocturnal at low temperatures
Authors: Greenwood M. F. D. , Metcalfe N. B.
Published: April 2005

Juveniles of several species of salmonid become almost exclusively nocturnal in winter. Their diel activity schedule is determined mainly by temperature, with the fish seeking shelter increasingly during the day as the temperature drops. Through controlled laboratory experiments, it is demonstrated that a comparable response is found in another stream‐dwelling species, the minnow Phoxinus phoxinus. Daytime observations showed that fish were found hiding in refuges on only 20% of occasions at 13.2° C but on over 75% of occasions at 6.6° C. In contrast, the minnows remained in the water column and used the refuges rarely at night irrespective of water temperature. As a consequence their activity became increasingly nocturnal as temperature dropped. It is suggested that this may be an adaptation to avoid diurnal predators.
Survival and emergence pattern of sea trout fry in substrata of different compositions
Authors: Rubin J.‐F.
Published: April 2005

The emergence of the sea trout Salmo trutta fry of Gotland, Sweden, was studied in the laboratory. The main limiting factor for survival up to hatching was the interstitial oxygen concentration, which depends on the gravel permeability, therefore on the substratum granulometry. Fry emergence was possible in substrata in which the geometric mean particle diameter (dg) was >15 mm and in substrata in which dg was <6 mm. In the substrata of low dg, emergence took place earlier than in the other ones. As a consequence the fry were smaller and their yolk sac only partially resorbed. In an unfavourable environment, fry started to emerge as soon as they reacted positively to light, about 2 weeks after hatching.
Sequence length and variation in the mitochondrial control region of two freshwater gobiid fishes belonging to Rhinogobius (Teleostei: Gobioidei)
Authors: Chen I‐S. , Hsu C.‐H. , Hui C.‐F. , Shao K.‐T. , Miller P. J. , Fang L.‐S.
Published: April 2005

The control region (D‐loop) of mitochondrial DNA (mtDNA) was amplified and sequenced for eight samples of the rhinogobies Rhinogobius maculafasciatus and R. giurinus from Taiwan and southern China. The control regions of both species are of 841–842 bp; the length of these sequences being the most compact among all known sequences in teleost fishes. Three conserved sequence blocks (CSB) were observed. The full D‐loop and tRNA Phe gene sequences were determined and compared with other fishes. The interspecific sequence divergence between the two species is 11.3–11.7%; and the intraspecific variation in R. guirinus 0.8–1.8%. Results suggest that the control region of Rhinogobius is informative for phylogenetic reconstruction at both intraspecific and interspecific levels in this gobiid genus.
Movement of adult Atlantic salmon in the Usk estuary, Wales
Authors: Aprahamian M. W. , Jones G. O. , Gough P. J.
Published: April 2005

A total of 56 salmon was tagged in the Usk estuary using combined acoustic and radio tags. Those fish migrating within the estuary oscillated with the tide over c. 10 km, being towards the seaward end at low water and moving upstream on the flood tide. Fish migrating through the estuary moved upstream on the flood tide and stemmed displacement downstream during the ebb. These findings, together with information on the hydrodynamics of the estuary, indicate that the fish utilize tidal currents to migrate passively in their preferred direction.
Hypoxia tolerance in Atlantic cod
Authors: Plante S. , Chabot D. , Dutil J.‐D.
Published: April 2005

Oxygen saturation levels that killed 50 and 5% of cod Gadus morhua over 96 h averaged 21·2 and 27·7%, respectively. No fish survived at 10% saturation and only a few survived at 16% saturation, whereas no mortality occurred at 34 and 40% oxygen saturation. Since metabolic rate and oxygen consumption increase with increasing temperature, we hypothesized that cod would be less tolerant to hypoxic conditions at 6 than at 2° C. However, temperature (2 and 6° C) had no measurable impact on cod survival. Small (mean & S.D.; 45·2 ± 4·2 cm) and large (57·5 ± 3·8 cm) cod had the same tolerance to hypoxia. At the end of the experiments, hypoxia had a significant effect on blood haematocrit, mean cellular haemoglobin content, liver lactate, plasma glucose and plasma lactate, but accounted for only a small fraction (< 10%) of the variation, except for plasma lactate which exhibited a strong response with concentrations increasing progressively with decreasing levels of oxygen saturation. Temperature had a significant effect on most variates in normoxia and hypoxia. Variates also affected by oxygen level showed significant interactions between oxygen and size or temperature effects. However, these interactions accounted for only a small proportion of the variation. Physiological parameters indicated that extending the duration of our tests beyond 96 h would not have changed our estimates of the lethal thresholds. Hypoxic conditions are a permanent feature of the deep waters of the Gulf of St Lawrence. This study shows that a significant portion of the benthic habitats in the Gulf are uninhabitable for cod which would be expected to avoid waters below 28% oxygen saturation.
Alimentary tract helminths of four pleuronectid flatfish in relation to host phylogeny and ecology
Authors: Lile N. K.
Published: April 2005

Eighteen species of helminths were analysed in relation to host–parasite specificity and the effect of host ecological preferences on the establishment of the parasite fauna in the alimentary tract of four pleuronectid flatfish, flounder Pleuronectes flesus, witch flounder Glyptocephalus cynoglossus, American plaice Hippoglossoides platessoides, and Atlantic halibut Hippoglossus hippoglossus in northern Norway. Thirteen species were generalists and the diversity of the parasite faunas decreased with increasing depths inhabited by the host. Similarities were greatest between the parasite faunas of flounder and American plaice and least between flounder and witch flounder. Host ecology, rather than phylogenetic relationships of these hosts, mainly influences the composition and diversity of the parasite communities of flatfishes in northern Norway.
A description of rodlet cells from the alimentary canal of Anguilla anguilla and their relationship with parasitic helminths
Authors: Dezfuli B. S. , Capuano S. , Manera M.
Published: April 2005

Rodlet cells in intestinal epithelia of infected and uninfected European eels Anguilla anguilla from brackish and fresh water were studied by light and electron microscopy. Deropristis inflata (Trematoda) was found in eels from brackish water, whereas eels from fresh water were infected with Acanthocephalus clavula (Acanthocephala). In a comparison between uninfected and infected eels from brackish water, a higher number of rodlet cells was recorded in the intestinal epithelia of infected fish. Evidence is presented that rodlet cells secrete their contents in a holocrine manner into the lumen of the eel intestine. The occurrence of organelles within the mature rodlet cell was rare. ? 1998 The Fisheries Society of the British Isles
Chromosomal and morphological abnormalities caused by oocyte ageing in Silurus glanis
Authors: Váarkonyi E. , Bercséanyi M. , Ozouf‐Costaz C. , Billard R.
Published: April 2005

The effects of ageing oocytes for 6 h before fertilization in the European catfish Silurus glanis are compared with the same experiment under normal conditions (stripping and fertilization immediately after ovulation). Fertilization rate and hatching rate are lower in the aged groups, while the percentages of malformed larvae and chromosomal abnormalities are significantly higher. Several kinds of abnormalities are described in detail.
Genetic implications of hatchery rearing in Atlantic salmon: effects of rearing environment on genetic composition
Authors: Crozier W. W.
Published: April 2005

In an experiment to investigate genetic consequences of hatchery rearing in salmon, allozyme variation at five polymorphic loci was examined in Atlantic salmon of known initial genetic composition, which were reared throughout freshwater life in the hatchery or stocked into the wild as swim‐up fry. The genetic composition of the juveniles in the hatchery remained homogeneous from fertilization up to stocking, and from stocking to 2+ in the wild, however, those remaining at the hatchery developed genetic differences among smolting and nonsmolting 1+ parr. These differences were attributed to conditions leading to early smolting at 1+ among the hatchery fish, with 1+ smolts diverging from the gene pool from which they were derived, whereas those stocked into the wild did not smolt until a year later and retained the original genetic composition. The results are discussed in relation to hatchery rearing of salmon and implications for the use of reared fish in stocking and enhancement programmes.
Effects of long‐term exercise on survival, homing and straying of released Atlantic salmon smolts
Authors: Tkilbrei O. T. , Holm M.
Published: April 2005

Atlantic salmon 1+ pre‐smolts were exercised under low (LE) or moderate (ME) water current velocities prior to release. The flow regimes had a minor effect on freshwater growth and did not affect total Carlin‐tag recaptures significantly, but the LE adults strayed more frequently and the ME salmon homed more successfully to the release site.
Correlation among dominance status, metabolic rate and otolith size in masu salmon
Authors: Yamamoto T. , Ueda H. , Higashi S.
Published: April 2005

In spatial competition between individuals, neither fish sex nor body mass affected dominance status in masu salmon Oncorhynchus masou . In contrast, resting metabolic rate (MR) was significantly correlated with dominance status, indicating that a high metabolic rate can increase the dominance rank of juvenile salmon. Whole animal growth rate was significantly correlated with MR, but not with initial body weight. This suggests that the body size of masu salmon is not a cause, but rather a consequence, of dominance status which is closely related to MR. The increment width between otolith daily rings was also significantly correlated with MR. Thus, the size of the Otolith may indicate the degree of MR.
Calcium metabolism and osmoregulation during sexual maturation of river running Atlantic salmon
Authors: Persson P. , Sundell K. , Björnsson B. Th. , Lundqvist H.
Published: April 2005

As Atlantic salmon return from the ocean to undertake the anadromous spawning migration up the river of origin, profound changes in calcium metabolism and osmoregulation take place. Using tartrate resistant acid phosphatase as a marker, scale osteoclast activity was found to increase throughout sexual maturation and spawning migration. Thus, the participation of osteoclasts in the elevated scale resorption observed during this phase is established. As calcium was simultaneously accumulated in the female gonads, it is proposed that the scales are resorbed in order to provide calcium for the growing ovaries. Plasma oestradiol‐17β levels were elevated in females during sexual maturation, and had decreased at the time of spawning. Plasma testosterone levels were similar in males and females during the first part of the upriver migration, but had increased in males and decreased in females at spawning. In addition to the role of these sex steroids in the gonadal growth, their possible involvement in the increased scale resorption during this phase is discussed. Plasma growth hormone and thyroxine levels were elevated in both sexes at spawning, with the triiodothyronine/thyroxine (T3/T4) ratio declining sharply, indicating possible roles for these hormones in the maturational process. The relatively low gill Na+, K+‐ATPase activity of salmon caught in the estuary implies that the fish had already adapted to a hypoosmotic environment. During the upriver migration, the gill Na+, K+‐ATPase activity decreased further, indicating that the hypoosmoregulatory ability was suppressed further during sexual maturation and spawning migration.