bluuebunny/crossref_metadata_2025 huggingface dataset:
Chromosomal inheritance patterns of intergeneric hybrids of ictalurid catfishes: odd diploid numbers with equal parental contributions
Authors: Zhang Q. , Tiersch T. R.
Published: April 2005

Hybrid chromosomal compositions of channel catfishIctalurus punctatus× black bullheadAmeiurus melasand channel catfish × flathead catfishPylodictis olivariswere analysed by a computer‐based method. The karyotype of each hybrid was highly asymmetric, and the diploid numbers and arm numbers were intermediate to the parental types. The hybrid offspring of channel catfish × black bullhead possessed a diploid number of 59 chromosomes, with an arm number estimate of 87. The hybrid offspring of the channel catfish × flathead catfish cross possessed a diploid number of 57 chromosomes, also with an arm number estimate of 87. Nucleolus organizer regions (NORs) were located on a single pair of chromosomes with symmetric staining intensity in channel catfish and in black bullhead, and on a single pair of chromosomes with asymmetric staining intensity in flathead catfish. The channel catfish × black bullhead hybrid had two unpaired chromosomes that stained positively for NORs. The channel catfish × flathead catfish had three unpaired chromosomes that stained positively for NORs. Specific marker chromosomes were identified in each hybrid. There was no evidence of androgenesis, gynogenesis, polyploidy or aneuploidy in the hybrids. Results of this study, plus information reported previously, indicate that chromosomes of ictalurid catfishes are inherited stably in a haploid pattern with an equal contribution to the genomes of F1hybrids, even in intergeneric crosses involving divergent numbers of parental chromosomes.
Temporal patterns of resource partitioning among Cichla species in a Venezuelan blackwater river
Authors: Jepsen D. B. , Winemiller K. O. , Taphorn D. C.
Published: April 2005

In channel and floodplain habitats of the Cinaruco River, Venezuela, Cichla temensis was more abundant and larger than C. intermedia and C. orinocensis. Seasonal variation in hydrology influenced habitat use, spawning, and predator‐prey interactions. The three piscivores partitioned habitat, with C. intermedia showing a strong affinity for structured habitats in the main channel during all water level fluctuations. C. orinocensis was most abundant in shallow areas with submerged structure in lagoons and, to a lesser extent, in low velocity regions of the channel, and C. temensis occupied a wide range of lotic and lentic habitats. During the low‐water period, the feeding frequency and body condition of all three species declined, and this was related, in part, to preparation for spawning near the end of the low‐water season. The diet of C. intermedia was least similar to its two congeners during falling and rising water. C. orinocensis and C. temensis had lowest diet overlap during the low‐water conditions, the period when many individuals of these two species move into lagoons for nesting. Prey in stomachs were significantly larger during the falling‐water than the rising‐water period, and predation by Cichla and other large piscivores during the falling‐water period may have reduced the abundance of large prey, particularly Semaprochilodus kneri. These migratory detritivorous fish were important prey for C. temensis during the falling‐water period and probably contributed a substantial fraction of the annual energy intake for this species. Together, the three Cichla species consume a wide spectrum of prey from a diverse fish assemblage, but prey are subdivided based on habitat, prey type, and season.
On the life history of the lesser gurnard (Scorpaeniformes: Triglidae) inhabiting the Agulhas Bank, South Africa
Authors: Booth A. J.
Published: April 2005

Growth analysis based on sectioned sagittal otoliths revealed the lesser gurnard Chelidonichthys queketti on the Agulhas Bank to be relatively fast growing and long lived, with ages of up to 7 years being recorded. Total length at age (mm) was described best by the specialized von Bertalanffy growth model as LT=306·1 (1 − e0·53(t+0·18)). First approximations of total, natural and fishing mortality rates were determined at 0·73, 0·38 and 0·35 year−1 respectively. The adult population was male dominated with a sex ratio of 1 female: 1·2 males with the mean size of males and females being similar. The lesser gurnard is an iteroparous species with females maturing by the end of the first year of life (195 mm LT), thereafter spawning throughout the year with reproductive activity peaking over spring and late summer. The lesser gurnard appears to exhibit similar life‐history patterns to other triglid species in that it can be classified as a generalist. Generalistic life‐history characteristics such as a fast growth rate, early sexual maturity at a relatively large size, a non‐seasonal spawning pattern, feeding on a variety of prey organisms and the ability to inhabit various substrata could all contribute to it maintaining a high biomass on the Agulhas Bank.
Presence of dentition in the premaxilla of juvenile Mullus barbatus and M. surmuletus
Authors: Aguirre H.
Published: April 2005

The genus Mullus is usually described as lacking teeth in the premaxilla. Contrary to generic descriptions (based on adult specimens), the juveniles of M. barbatus and M. surmuletus have teeth in the premaxilla; however, the teeth are not visible in specimens >50 mm total length, because they are covered by lip tissue. The number of teeth decrease with juvenile growth and disappears after c. 100 mm total length is attained.
Distribution of four recently discovered galaxiid species in the Taieri River, New Zealand: the role of macrohabitat
Authors: Allibone R. M. , Townsend C. R.
Published: April 2005

The physical features of 20 streams inhabited by four recently discovered species of allopatric, non‐migratory galaxiid fishes in the Taieri River, South Island, New Zealand were examined. Significant differences in particle size frequencies, combined waterfall frequency, channel depth variation and stream width: flood channel width ratios, indicated that Galaxias anomalus lived in low gradient shallow streams whereas G. depressiceps and G. eldoni occupied low to high gradient streams with more variability in depth. Climbing ability differed significantly among the species. Their allopatric patterns of distribution were, in part, the probable consequence of the abilities of G. depressiceps and G. eldoni to colonize areas that G. anomalus could not penetrate. Historical factors and reproductive biology of the four species are hypothesized also to be causal determinants of their current distributions.
How to quantify embryo survival in nest‐building fishes, exemplified with three‐spined sticklebacks
Authors: Kraak S. B. M. , Bakker T. C. M. , Mundwiler B.
Published: April 2005

Egg survival in manipulated nests of three‐spined sticklebacks Gasterosteus aculeatus in the field was not significantly different from that in unmanipulated nests.
Age estimation, growth, maturity and distribution of the roundnose grenadier from the Rockall trough
Authors: Kelly C. J. , Connolly P. L. , Bracken J. J.
Published: April 2005

This paper summarizes the history of commercial exploitation of roundnose grenadier Coryphaenoides rupestris in the North Atlantic. Length frequencies of C. rupestris in 1993, from 400 to 1200 m on the slopes of the Rockall trough indicate a reduction since the 1970s in the modal length of fish found at 700–1000 m. Ages ranged from 2 to 50 years for males and 2 to 60 years for females, with most between 10–38 years. Females attained a greater asymptotic pre‐anus length (L∞=19.5 cm) than males (L∞=15.5 cm) and had a greater weight for a given age (male W∞=761g, female W∞=1132g). This species may have a protracted spawning period. Using pre‐anus lengths, 50% of male fish were mature at 10 cm (ages 8–10) while 50% of female fish were mature at 12 cm (ages 9–11). At the greatest depths sampled the length frequency of fish was bimodal with a hiatus between 9 and 11 cm (ages 8–12). Highest catch rates occurred on the Donegal slope in September at a depth of 800–1000 m.
On the visual pigments of deep‐sea fish
Authors: Douglas R. H. , Partridge J. C.
Published: April 2005

The retinal visual pigments of 52 species of deep‐sea fish were measured by partial bleaching of detergent extracts. The retinae of 45 species contained only a single rhodopsin with maximum absorbance (λmax) at a wavelength between 474 and 490 nm, matching both the region of highest intensity downwelling sunlight and the maximum emission of most deep‐sea bioluminescence. Seven species were shown to have more than one visual pigment within their retinae and these had λmax values that generally fell outside the usual range. One of these, Bonapartia pedaliota, was particularly interesting as, unlike most such multipigment species, it had one rhodopsin and one porphyropsin pigment, apparently based on different opsins. The relative proportions of the visual pigments in the seven multipigment species are presented.
Respiratory gill surface of the serrasalmid fish, Piaractus mesopotamicus
Authors: Severi W. , Rantin F. T. , Fernandes M. N.
Published: April 2005

Gill element dimensions of pacu Piaractus mesopotamicus were estimated and correlated to body mass (W), according to the power equation Y=aWb. The filament number (b=0.154) and length (b=0.457) increased with body mass, markedly influencing the respiratory gill surface area (b=0.769). The high filament number and length, associated with a high secondary lamellae frequency (a=40.21), are typical of active fish species and may be an adaptation to its migratory movements during reproduction. The comparatively small dimensions of its secondary lamellae are found more commonly in less active species, and may be related to the environmental conditions prevailing in lentic environments, where the species is normally found most of the year. Such features, together with its ability to compensate for oxygen reduction by means of a high ventilatory volume, and the use of aquatic surface respiration (ASR), may account for its adaptative capacity to withstand hypoxic conditions, with a low respiratory energy cost.
Food and habitat of four Xenotilapia species (Teleostei, Cichlidae) in a sandy bay of northern Lake Tanganyika (Burundi)
Authors: Gysels E. , de Bisthoven L. Janssens , De Vos L. , Ollevier F.
Published: April 2005

The feeding ecology of four species of Xenotilapia (Teleostei, Cichlidae) from Lake Tanganyika was investigated by examining their intestine contents in three different habitats from two 24‐h catch cycles. The fish were caught in a sandy bay 4 km north‐west of Bujumbura (Burundi) during the dry season, from August until October 1993. Three different habitats were sampled: an area 600 m offshore at a depth of 15 m, a littoral zone near a reed bed (depth, 0–5 m), and an area near a sandy beach (depth, 5 m). The fish were most active in the early morning and at night, except for X. caudafasciata which was the most diurnal. X. ochrogenys was confined to the vicinity of the reeds, where few individuals of the other species were found, and prey comprised mainly ostracods, copepods and chironomid larvae (Tanytarsini). X. ornatipinnis and X. longispinis occurred in large numbers both at a depth of 15 m and near the sandy beach. X. ornatipinnis preyed mainly on copepods, oligochaetes, diatoms and chironomid larvae. X. longispinis had a wider range of temporal and spatial distribution compared with the other species and fed on copepods, ostracods and chironomid larvae (mainly Microchironomus spp.). X. caudafasciata (only caught at 15 m) fed mostly on profundal chironomid larvae (Tanypodinae and Microchironomus spp.). Trophic niche overlap between X. longispinis and X. caudafasciata appeared to be reduced through different activity patterns. Few intraspecific differences in food diet were found between sex and age groups.
Daily feeding rhythms in Atlantic salmon II: size‐related variation in feeding patterns of post‐smolts under constant environmental conditions
Authors: Kadri S. , Metcalfe N. B. , Huntingford F. A. , Thorpe J. E.
Published: April 2005

Previous studies of feeding rhythms in post‐smolt Atlantic salmon Salmo salar have produced variable results. Therefore, the present study was performed to clarify the source of these differences and to examine size‐related variation in daily feeding patterns. A small group of hatchery reared post‐smolts was kept in an indoor seawater tank under conditions of constant photoperiod and light intensity, and negligible diurnal variation in water temperature. Feeding responses were monitored by video camera throughout the day. The resultant feeding pattern for the population mirrored an earlier study, with the highest levels of feeding activity in the early morning and late evening. Differences between this and other studies may be due to variation in climate, season or life‐history stage. Daily feeding patterns were size‐dependent. The largest fish fed at a relatively constant level through the day, medium‐sized fish fed in a pattern similar to that described above for the population and small fish fed most at first and last light. These differences were due probably to the effect of competitive interactions upon fish of different sizes.
The role of temperature and cannibalism in interannual recruitment variation of bass in British waters
Authors: Henderson P. A. , Corps M.
Published: April 2005

Between‐year variation in bass Dicentrarchus labrax year‐class strength in southern British waters is investigated. Mean spring‐summer seawater temperature in the year of birth was significantly positively correlated with both the level of summer recruitment of the 0 + group to the estuarine nurseries and subsequent recruitment of III + fish to the adult population. Spectral analysis of the temperature‐compensated time series showed that a statistically significant proportion of the variation not attributable to temperature was periodic at 0–33 cycles year−1. Therefore, a simple, three‐parameter model, combining a linear relationship between temperature and abundance and a second‐order autoregressive model can be used to describe and predict variation in relative adult YCS. Bass remain for their first 3 years within their estuarine nursery areas. As I + fish were observed in Southampton water to cannibalize the 0 + group, it is suggested that strong year‐classes suppress recruitment for the next 2 years even if the temperature is suitable to promote a strong year‐class. Cyclic variation in recruitment caused by intraspecific interactions, particularly cannibalism, may be a feature of other marine fish that use estuaries as nursery areas.
Stock composition in North Atlantic populations of whiting using microsatellite markers
Authors: Rico C. , Ibrahim K. M. , Rico I. , Hewitt G. M.
Published: April 2005

A size‐selected library constructed from DNA of the whiting Merlangius merlangus was screened. From about 3200 recombinant clones, 43 microsatellite loci were detected. Thirteen were sequenced in full. Primers were designed from the sequence of the flanking regions for six loci and used to test the allelic variability at these loci using the polymerase chain reaction (PCR). In addition, five primer pairs developed for the stickleback and another seven for cod were tested. Only six primer pairs revealed at least three alleles per locus. The three useful loci Gmo2, Mmer‐UEAW01 and Mmer‐UEAW02, had 14–23 alleles per locus in 370 samples. Estimates of genetic structure (φ) were not statistically significant. However, estimates of genetic differentiation (Fst) were significantly different from zero. Heterogeneity χ2‐analysis of allele frequencies among populations suggested relatively low levels of differentiation among samples. Significantly different allele frequency distributions were found for Borgensfjord and northern and southern North Sea samples for at least one locus, and between the latter samples for Mmer‐UEAW02 and Gmo2. There were significant excesses of homozygotes in all samples, over expectation for randomly mating populations in Hardy‐Weinberg equilibrium. The estimated frequencies of null alleles were 14.3%, for Mmer‐UEAW01, 10.2% for Mmer‐UEAW02 and 11.6% for Gmo2. This result calls for a careful interpretation of the significance of these microsatellite data.
Radio‐transmitted electromyogram signals as indicators of physical activity in Atlantic salmon
Authors: ØKland F. , Finstad B. , McKinley R. S. , Thorstad E. B. , Booth R. K.
Published: April 2005

Surgical methods developed to implant EMG (electromyogram) transmitters in Atlantic salmon Salmo salar were tested to calibrate electromyograms from axial red musculature to swimming speed in a swim speed chamber, and to compare electromyograms of fish from two stocks (Lone and Imsa). Ten Lone and eight Imsa salmon were equipped with internal EMG transmitters. Surgical procedures were acceptable, with 100% survival of all implanted fish during the study. It was possible to calibrate EMG pulse intervals to swimming speed in 14 of the 18 salmon run in the swim speed chamber (r2= 0·35‐0·76 for individuals, 0·63 for pooled data). Individuals differed in their EMG resting levels (EMGs recorded at 0·5 ms−1), and so higher correlations were obtained between swimming speed and an activity index (EMG pulse intervals at different speeds/EMG resting levels) (pooled data, r2=0·75). The linear relationship between swimming speed and EMG pulse intervals differed significantly between the two stocks (P<0·05). This successful calibration of EMGs to swimming speed opens the possibility of calibrating EMGs to oxygen consumption and the measurement of the metabolic costs of activity in field experiments.
An electron microscope study of intrusions into alarm substance cells of the channel catfish
Authors: Chapman G. B. , Johnson E. G.
Published: April 2005

Thin and ultrathin sections of the epidermis of two channel catfish Ictalurus punctatus were studied in light and electron microscopes, respectively, to learn more about intrusions of entire other cell types into alarm substance cells, first noted in 1981. Several degrees of intrusion and several stages in the process of total intrusion are described: microvillus‐like projections, pseudopod‐like projections, telophase‐stage projections, total cell intrusion. In addition, several different cell types intrude: lymphocyte‐like cells, general epidermal cells, virus‐infected cells and other alarm substance cells. These findings indicate that the alarm substance cell is extraordinarily subject to invasion by other cell types. They suggest that its plasma membrane may have been modified so as to be somewhat less effective in preserving cell integrity (and thus more easily release its alarm pheromone on injury) than is the case with most other cell types or that the alarm substance acts as an attractant for other epidermal cells.
Surface ultrastructure of paddlefish eggs before and after fertilization
Authors: Linhart O. , Kudo S.
Published: April 2005

The surface ultrastructure of eggs of the paddlefish Polyodon spathula was investigated by scanning electron microscopy. Mature eggs of paddlefish possess four to 12 micropyles in the animal polar region. There are sperm entry sites in the egg surface under the micropyles which consist of tufts of microvilli. Five to nine sperm entry sites were observed on mature eggs. Probably, the number of sperm entry sites corresponds to the number of micropyles. In a few eggs, 1 min after fertilization the ball‐like enlarged top of a cytoplasmic process (probably a full‐grown fertilization cone) had reached the external aperture or the canal of several micropyles. In other micropyles of the same egg, a few smaller cytoplasmic processes or flocculent material were found in the micropylar canal. With one exception, no sperm tails were found there. The formation of the full‐grown cytoplasmic process is possibly initiated before the cortical reaction has started in an area of the animal hemisphere. Three, 10 and 20 min after fertilization, the uneven surface of the cortical cytoplasm in the animal polar region rose gently where microvilli were much less than the in other area and together with a secondary polar body at the latter stage. Taken together, paddlefish eggs may have sperm entry sites corresponding to the number of micropyles and respond to the stimulus of fertilization by forming a few cytoplasmic processes–fertilization cones (larger and smaller). Sperm penetration into the egg may be achieved at an earlier stage of fertilization (sperm‐egg contact), as inferred from the fact that a secondary polar body was formed at the 20‐min stage irrespective of the exceptional finding of the sperm tail.
Condition cycles in juvenile Pagrus auratus
Authors: Francis M. P.
Published: April 2005

Nutritional condition was measured in juvenile snapper Pagrus auratus (<200 mm fork length) using three indices: relative condition index (Ic), hepatosomatic index (IH) and digesto‐somatic index (ID). In a laboratory starvation experiment, all three indices declined substantially over a 24‐day period, but IH was most sensitive. In wild snapper Ic and IH showed no diel cycles. ID for 0+ snapper showed a strong diel cycle consistent with continuous feeding during daylight hours and lack of feeding during the night. ID for 1+ snapper showed no diel cycle. Subsequent analyses were restricted to daytime samples for IH and morning samples for ID to minimize the confounding effect of time of day. Ic, IH and ID were monitored at one site at approximately bi‐monthly intervals over a period of 3.25 years. All three indices varied significantly, but only ID and IH displayed seasonal cycles. ID peaked in late summer‐autumn and dropped to a minimum in winter, due to seasonal fluctuations in the feeding rate that probably reflected variations in metabolic and growth rates. IH peaked in autumn‐winter and declined to a minimum in summer, thus lagging 4–6 months behind ID. IH varied significantly among four sampling sites for all five combinations of sampling periods and year classes, whereas Ic varied significantly among sites for only one of the five combinations. The Kawau Bay site, which supported the highest density of snapper, had the highest IH for all except one of the combinations. This suggests that juvenile snapper aggregate selectively at sites that provide optimal feeding conditions. However, no relationship was found between IH and growth rate, indicating that better nutritional condition may not translate into faster growth.
Differential dispersal patterns of male and female masu salmon fry
Authors: Nagata M. , Irvine J. R.
Published: April 2005

Behavioural experiments using artificial and natural stream channels were undertaken to determine whether there were differences in dispersal between newly emerged male and female masu salmon. Eyed eggs from a cross with wild spawners were planted in the middle pool of an artificial channel. After emergence, more males than females moved into an upstream trap, while fewer males moved downstream. In a natural stream, eyed eggs were marked with alizarin complexone to distinguish them from naturally spawned eggs and these were planted into artificial redds. More newly emerged male fry remained at the planted site than female fry. In contrast, more females moved downstream than males. These results imply that differences in dispersal patterns between male and female masu salmon fry are genetically controlled.
The improved incorporation of polyunsaturated fatty acids and changes in liver structure in larval gilthead seabream fed on microdiets
Authors: Salhi M. , Izquierdo M. S. , Hernandez‐Cruz C. M. , Socorro J. , Fernandez‐Palacios H.
Published: April 2005

Two feeding experiments were conducted to evaluate the suitability of two commercial microdiets as a complementary food for the rearing of larval gilthead seabream Sparus aurata. The effect of these diets on growth, survival and total lipid composition, as well as the histological structure of the liver were examined. The results of the first trial highlighted water quality as an important factor for the survival of microdiet‐fed larvae. An increase in water flow rate improved larval survival despite a reduction in live food supply. An effect of tank design on larval growth and survival was observed also and seems to be related with the light level inside the tanks; wider light grey tanks gave better results than narrower black ones. Microdiet feeding significantly improved larval growth and increased hepatocyte diameter and presence of PAS positive vacuoles suggesting an increased glycogen storage in comparison with that of larvae fed live prey only. Artificial diets provided the larvae with a higher amount of lipids and polyunsaturated fatty acids of the n‐3 series, resulting in a higher DHA content in the total lipid of the larvae fed on microdiets.
Population genetic structure of the catadromous Australian bass from throughout its range
Authors: Jerry D. R.
Published: April 2005

One hatchery‐derived impoundment and nine wild riverine populations of the catadromous percoid Australian bass Macquaria novemaculeata were examined at six polymorphic allozyme loci to reveal population genetic structure. Subtle genetic differences among many populations indicated that fish did not interact as a panmictic unit, but rather conformed to an isolation by distance pattern of population structure. The hatchery‐derived Glenbawn Dam sample differed from the riverine populations in both average heterozygosity and number of polymorphic loci, demonstrating the need for caution in supplementation programs to rehabilitate wild riverine populations.
Reproductive characteristics of the male herring in the northern Baltic Sea
Authors: Rajasilta M. , Paranko J. , Laine P. T.
Published: April 2005

The gonad weight and gonadosomatic index of the male Baltic herring Clupea harengus membras L., were highest at the beginning of the reproductive season (April/May), the values decreasing towards the end of it (July/August) during 1988–1991. The decline could not be explained by fish size but may have been due to fish condition. A high individual variation was typical for both gonad weights and gonadosomatic indices in fish of the same size and maturity stage. The mean density of sperm cells was significantly higher in June (34·9 × 109 ml−1) than in July (19·2 × 109 ml−1, Mann‐Whitney U= 17; P<0·05), the variation among the males being high in both groups. Electron microscope analysis showed a severe disruption of the mitochondrial elements in males spawning at 22°C.
Social dominance, prior residence and the acquisition of profitable feeding sites in juvenile Atlantic salmon
Authors: Huntigford F. A. , de Leaniz C. Garica
Published: April 2005

Twelve groups of 10 Atlantic salmon Salmo salar parr were screened for dominance in small tanks with a single localized food source using a serial removal method and the top, middle and bottom two fish in each group were classified as high, medium and low social status, respectively. These 72 ranked fish were weighed and formed into four groups or waves, each consisting of six fish of each status category. The fish were given dye marks according to status and wave and were then introduced into an artificial stream in four waves over a 12‐day period. Patterns of settlement/emigration were recorded over a 2‐month period, at the end of which the fish were removed from the stream, identified and reweighed, and daily specific growth rates calculated. Fifty‐one fish established feeding stations in the flume, the remainder emigrating via a downstream trap. The average growth rate over the 2‐month period was 0·87% day−1. Probability of settlement and growth rates following settlement were significantly higher in fish from the earlier waves. In contrast, salmon that were dominant in the initial trial were less likely than subordinate fish to settle in the experimental stream and showed lower postsettlement growth rates. The possibility that fish have individually consistent behavioural profiles that promote success in different competitive environments is discussed with reference to published literature for other groups. A small‐scale trial at the end of the main experiment confirmed the prior residence effect and demonstrated that 1 day was sufficient for such an effect to be evident.
Ecomorphological individual variation in a population of Haplochromis nyererei from the Tanzanian part of Lake Victoria
Authors: Fermon Y. , Cibert C.
Published: April 2005

Intraspecific morphological variation among a population of Haplochromis nyererei (Teleostei, Cichlidae) from Lake Victoria was investigated. Three main groups of variables were used: general shape, outline of the head, and trophic group (intestinal length, stomach contents, teeth and jaw shape, lower jaw length and width). Fishes were arranged into four groups: G1, large males with a prominent bump on the head, a thickset body and anatomical structures related to a strictly insectivorous diet; G2, large males lacking a bump on the head but more or less thickset and showing anatomical structures related to omnivorous feeding habits, though favouring insects; G3, males and a few females with a slight bump on the head, a slender body shape and showing anatomical structures related primarily to a herbivorous tendency; and G4, females and a few small males without a bump on the head, a slender body and showing anatomical structures related to an omnivore with herbivorous tendencies. Several hypotheses related to behaviour are presented partly to explain the intraspecific variation observed. Differences between individuals could arise as a result about the establishment of dominance and territory in males.
Microvideography of gas bladder inflation in larval walleye
Authors: Rieger P. W. , Summerfelt R. C.
Published: April 2005

High‐resolution microvideograph observations supported the hypothesis that first filling of the gas bladder of larval walleye Stizostedion vitreum is accomplished by the fish penetrating the air‐water interface to gulp air, then transmitting a swallowed air bubble through the gut and the pneumatic duct to the gas bladder. The snout of the larva penetrated the water surface with extension of most of the mouth into the air for only 1.5 s. An air bubble (c. 100 μm) in the foregut was broken up into progressively smaller bubbles (10–15 μm), presumably by the combined effect of surfactant derived from the gall bladder and mechanical (peristaltic) action of the gut. These smaller bubbles seemed to be aligned in the pneumatic duct before being forced to the gas bladder by pressures generated from peristalsis.
Growth and feed utilization by F4human growth hormone transgenic carp fed diets with different protein levels
Authors: Fu C. , Cui Y. , Hung S. S. O. , Zhu Z.
Published: April 2005

The F4generation of human growth hormone (hGH) transgenic red common carpCyprinus carpiohad significantly higher growth rates than the non‐transgenic controls. Protein and energy intakes were significantly higher in the transgenic carp than in the controls fed the 20% protein diet, but were not different between the two strains fed diets with 30 and 40% protein. Faecal protein loss, as a proportion of protein intake, was significantly lower in the transgenics than in the controls fed diets with 20 and 30% protein, but was not different between the two strains fed diet with 40% protein. Faecal energy loss, as a proportion of energy intake, was significantly lower in the transgenics than in the controls fed diet with 20% protein, but was not different between the two strains fed diets with 30 and 40% protein. Recovered protein, as a proportion of protein intake, was significantly higher in the transgenics than in the controls fed all diets, whereas recovered energy was significantly higher in the transgenic fish fed the 40% protein diet. For fish fed each diet, the transgenics had significantly higher body contents of dry matter and protein, but lower contents of lipid than the controls. It was concluded that transgenics were more efficient in utilizing dietary protein than the controls. At a lower dietary protein level, transgenics achieved higher growth rates mainly by increasing feed intake; at higher levels of dietary protein, transgenics achieved higher growth rates mainly through a higher energy conversion efficiency.
Cutaneous taste buds in cod
Authors: Harvey R. , Batty R. S.
Published: April 2005

The distribution of cutaneous taste buds was determined quantitatively in larvae, juveniles and young adults of cod, using scanning electron microscopy. Changes in these distributions associated with development were followed in laboratory reared fish. Taste buds were first seen on the snout and lips of cod at a total length of 8 mm, and on the barbel at a length of 22 mm. The highest taste bud densities were seen at a length of around 90 mm, and subsequently declined on the barbel and pelvic fins with further growth. In these late 0‐group fish, mean taste bud densities over much of the head, e.g. throat, dentary and sides of the snout were <100 mm−2. On the tip of the snout and the lips, mean densities were in the region of 350–400 mm−2, while on projecting parts of the fish, especially the barbel, anterior naris flap and extremities of the fins, spot densities occasionally exceeded 1000 mm−2 at some sites. Mean taste bud diameter increased rapidly from 2.23μ± 0.35 μm (S.D.) at a length of 22 mm to 7.19 ± 0.23 μm at 90 mm length, with a much slower increase to about 8 μm associated with a further doubling in body length. These changes indicate a phase of rapid proliferation and growth in size of cutaneous taste buds in the period preceding the adoption of a benthic habit in their first summer. The presence of high taste bud densities on the barbel and pelvic fins in particular appears to correlate with the known feeding behaviour of cod.
Improved primer sequences for the mitochondrial ND1, ND3/4 and ND5/6 segments in salmonid fishes: application to RFLP analysis of Atlantic salmon
Authors: Nielsen E. E. , Hansen M. M. , Mensberg K.‐L. D.
Published: April 2005

New specific primers for the mtDNA segments ND1, ND3/4 and ND5/6 designed from the rainbow trout sequence, improved PCR amplification for salmonid fishes. RFLP analysis revealed restriction site variation for all three segments in Atlantic salmon. Eleven haplotypes were detected in a screening of 30 individuals from four European populations.
The olfactory system of a cichlid fish responds to steroidal compounds
Authors: Robison R. R. , Fernald R. D. , Stacey N. E.
Published: April 2005

Electro‐olfactogram (EOG) responses to a diverse range of steroid hormones were recorded in he African cichlid Haplochromis burtoni. Olfactory receptor responsiveness was sensitive to the attachment sites of sulphate and glucuronide groups.
Diel variation in habitat use by planktivores in field enclosure experiments: the effect of submerged macrophytes and predation
Authors: Jacobsen L. , Berg S.
Published: April 2005

The importance of submerged macrophytes and predation risk for habitat use by 0+ perch (Perca fluviatilis) and 0+ roach (Rutilus rutilus) was investigated in triplicate 78‐m2 field enclosures with and without macrophytes in the middle. During three experimental runs, habitat use by fish were monitored every 6 h with Breder traps. Each period included 2 days of fish monitoring before stocking with piscivorous perch, and 2 days after. Predation risk significantly changed habitat use by 0+ perch in the morning, midday and evening, but not at night. By comparing with the unvegetated controls, we found a refuging effect of macrophytes in the morning. Under predation risk there was significant diel variation in habitat use by 0+ perch, suggesting a migration from the open water habitat at night into the macrophytes in the morning. Roach continued to use open water even after predators were stocked, but responded like perch by reducing overall activity.
Maturation of male age‐0 Atlantic salmon following a massive, localized flood
Authors: Letcher B. H. , Terrick T. D.
Published: April 2005

Maturation of male age‐0 Atlantic salmon Salmo salar parr in New England, U.S.A. streams is rare (˜5%), but age‐0 parr maturation was high (74%) by autumn in the Sawmill River following a massive, localized flood. Maturation was low in two other study streams (3, 7%) in the same year as the flood, and in the Sawmill River (6%) and the other rivers (5%) in the subsequent year, suggesting that high maturation rates were related to the flood. The high age‐0 maturation rates appear to have been the result of greater growth opportunity following the flood. Masses of fish in October were two‐fold greater in the Sawmill River (13·2 g) than in the other rivers (6·5, 6·9 g). Mechanisms contributing to the fast growth may include community reorganization following the flood and water temperature differences among rivers. The flood caused an age‐0 year‐class failure for brook trout Salvelinus fontinalis and brown trout Salmo trutta and a large reduction (69%) in the number of salmon compared to the other rivers, possibly reducing competition or agonistic interactions among remaining fish. Average water temperatures were slightly warmer in the Sawmill River (17·0° C) than in the other rivers (15·5, 14·9° C). By influencing community structure and growth of remaining fish, it appears that a strong environmental disturbance can also alter the direction and timing of life histories in Atlantic salmon.
Is the distribution, growth and survival of juvenile salmonids sex biased? Negative results for coho salmon in an experimental stream channel
Authors: Dittman A. H. , Quinn T. P. , Volk E. C.
Published: April 2005

There were no sex‐related differences in spatial distribution, abundance or growth of juvenile coho salmon Oncorhynchus kisutch from two full‐sibling families after 75 days rearing in an outdoor stream channel. These findings are not consistent with recent reports that aggressiveness and spatial distribution differ between males and females in juveniles of other streamdwelling salmonid species.
Phylogeny of five Prosopium species with comparisons with other Coregonine fishes based on isozyme electrophoresis*
Authors: Vuorinen J. A. , Bodaly R. A. , Reist J. D. , Luczynski M.
Published: April 2005

Phylogenetic relationships of Prosopium gemmifer, P. spilonotus, P. williamsoni, P. cylindraceum and P. coulteri species were determined based on variation at 37 allozyme loci, and compared with Stenodus and nine species of Coregonus. Of the three genera, Prosopium was the most distinct with Nei genetic distances to Coregonus of D=0·55—1·05 and to Stenodus of D=0·58—0·92. Stenodus and Coregonus were closely related but grouped as sister taxa with a mean genetic distance of 0·31 (range 0·22—0·40). These results agree with the degree of morphological differentiation among the genera as well as with observations concerning hybridization, e.g. many Coregonus species hybridize with Stenodus, but no natural hybrids are known between Prosopium and other coregonines. Within Prosopium, P. coulteri was the most divergent species branching out at D=0·51 from the others and followed by P. cylindraceum at D=0·28. The three remaining species are closely related. Among them P. williamsoni joins P. gemmifer and P. spilonotus at 0·04, and the distance between the two Bear Lake endemics is only 0·004. The distance between P. cylindraceum and the remaining Prosopium species is similar to distances between Stenodus and Coregonus. The small genetic distance between P. spilonotus and P. gemmifer suggests their recent divergence. Even though no fixed differences were found between them, diVerent alleles were present at two loci at large enough frequencies to indicate reproductive isolation. This confirms that P. gemmifer and P. spilonotus are good biological species as indicated by their distinct morphology and ecology.
Gross and histological observations of ovarian development and related condition changes in American plaice
Authors: Maddock D. M. , Burton M. P. M.
Published: April 2005

The largest increase in gonadosomatic index of American plaice Hippoglossoides platessoides occurred between January and February. Hepatosomatic index was lowest in the spawning season, suggesting cessation of feeding activity during spawning, but rose immediately in July when condition factor recovered from its low spawning level. Increases in white muscle water content during the spawning season suggests protein depletion. Conservation of some white muscle fibres is suspected, but no regular pattern in area conserved was found. Gonad development was advanced in December and in April some gonads were showing evidence of spawning. Ovaries from spawning females showed hydration patterns and histological detail consistent with batch or serial spawning strategy. Evidence of recent spawning activity, including the presence of postovulatory follicles, was found in ovaries that also contained oocytes undergoing exogenous vitellogenesis. Oocyte size frequency distributions show a gap in size between cortical alveoli and vitellogenic oocytes prior to spawning which does not exist during the spawning season. This may represent the ability of plaice to push oocytes through vitellogenesis from a previtellogenic condition during the spawning period. The increased white muscle moisture during June and July may reflect the use of muscle protein to bring oocytes through vitellogenesis for the current spawning season.
Maternal and interannual comparison of the ovulatory periodicity, egg production and egg quality of the batch‐spawning yellowtail flounder
Authors: Manning A. J. , Crim L. W.
Published: April 2005

Estimates of the ovulatory periodicity of yellowtail flounder indicate that a 1‐day interval, which predominated over all other intervals, may characterize regular ovulation patterns. Females produced a mean number of 14–22 batches in 1994 and 1995, respectively. Batch fecundities usually remained within a range of 10 000–60 000 eggs. Mean egg production increased from 549 756 eggs per female in 1994 to 1 186 881 eggs in 1995. Mean fertilization rates rose interannually from 38 to 57%, while hatching rates, tested in 1994, had a mean of 63%. Maternal variation in egg production and egg quality was large and independent of size differences among females. Some females had disrupted ovulation patterns which affected the realization of potential fecundity contained within the prespawning ovary. High interbatch variation in egg quality was not related to progressive decreases in egg diameter and dry weight over time. Batches with high survival rates appeared at random within a female's duration of ovulation.
A quantitative study of morphological and histological changes in the skeleton of Salmo salar during its anadromous migration
Authors: Kacem A. , Meunier F. J. , Baglinière J. L.
Published: April 2005

A quantitative study of morphological and histological changes in the skeleton (cranial bones and vertebrae) of adult Atlantic salmon Salmo salar during its anadromous migration was performed in order to specify various aspects of its skeletal biology in relationship to this migration. At the beginning of the ascent, there was no morphological difference in the cranial bones between males and females. As the spawning season approached, males showed marked secondary sexual characters particularly allometric breeding growth of some bones of the skull. The histological analysis of the vertebral bone tissue along the vertebral axis showed that bone compacity and number of trabeculae vary depending on their localization on the vertebral axis. Moreover, bone compacity decreased significantly with the sexual maturation of the fish whereas the number of trabeculae grew in both sexes. Thus, the vertebrae (like scales) represent an important source of calcium and other elements during anadromous migration in Atlantic salmon.
Predicting fluctuations in the size of newly emerged sea‐trout fry in a Lake District stream
Authors: Elliott J. M. , Hurley M. A.
Published: April 2005

The objective was to predict interannual fluctuations in the size of sea‐trout fry when they emerged from the redd, using models developed from field data for 70 excavated redds (≥three per year), and from experimental data on egg and alevin development at 30 constant temperatures in the laboratory (range 1·5—10·5) C with 100 naturally fertilized eggs at each temperature). Egg weight increased with female length and also with the number of eggs laid in a redd, both relationships being well described by a power function. Early spawners were the largest females laying the largest and most numerous eggs, whilst late spawners were the smallest females laying the smallest and least numerous eggs, with middle spawners being intermediate between these two extremes. Mean values for egg weight and number of eggs per redd were obtained for these three groups. The numbers of early, middle and late spawners for each year of a 30‐year study and the mean values from the excavated redds were used to estimate weighted means for the number of eggs per unit area and egg weight. Mean values varied considerably between years (30‐year ranges: 518–7964 eggs per 60 m2; 112–138 mg wet weight). In the laboratory, mean weights of newly hatched alevins and newly emerged fry were both related positively to mean egg weights. Alevin and fry mean weights were independent of the number of days required for 50% of the eggs to hatch or fry to emerge. Models described in a previous paper formed the basis of those used to predict fry weights over the emergence period. Model predictions were validated by field data for the whole emergence period in 8 years (1967–1971, 1974, 1975, 1980), and by pre‐fry weights on single dates in 21 years (1967–1987). As pre‐fry densities on these single dates were very similar to egg densities for the same year class, mortality in the egg and alevin stages was very low. The chief objective was therefore fulfilled, and the extent of interannual fluctuations for the 30‐year study showed some variation in mean fry weight (30‐year ranges: 153–193 mg for both the whole emergence period and the date on which 50% of fry emerged) but a progressive decrease in fry weight through the emergence period. Possible reasons for this variation are discussed, and it is concluded that the size of the female spawners is the dominant factor.
Effect of female size on fecundity and egg size in white‐spotted charr: comparison between sea‐run and resident forms
Authors: Morita K. , Takashima Y.
Published: April 2005

The relationships between fecundity, egg size and female size of sea‐run form were compared with resident form, using white‐spotted charr,Salvelinus leucomaenis. Both fecundity and egg size increase with female size. However, the relationship between egg size and female size differed significantly between the resident and sea‐run forms. Egg sizes of sea‐run and resident were similar even though sea‐run fish were much larger. ? 1998 The Fisheries Society of the British Isles