bluuebunny/crossref_metadata_2025 huggingface dataset:
Experiments for the improved use of decapsulated Artemia cysts in intensive culture of African catfish larvae
Authors: Bardócz T. , Kovács É. , Radics F. , Sándor Zs.
Published: April 2005

Feeding dried and vitamin C enriched decapsulated Artemia cysts to African catfish larvae increased their growth rate significantly after 6 days over those fed only freshly decapulated cysts. Groups fed with Artemia nauplii had a significantly higher growth during the experiment, although this difference was not considerably important in practice. Tank colour had no influence on growth. Because of their lower price, the decapsulation of lower quality cysts can be an appropriate feed source in intensive cultures of African catfish larvae.
Egg size manipulation: a technique for investigating maternal effects on the hatching characteristics of herring
Authors: Morley S. A. , Batty R. S. , Geffen A. J. , Tytler P.
Published: April 2005

A technique was developed for manipulating egg size of recently fertilized Atlantic herring Clupea harengus embryos. Larvae hatching from eggs with reduced yolk volume were shorter than predicted for the volume of yolk removed. The reduction in both body and yolk mass of hatchlings was less than predicted, partly because larval yolk‐sac mass was unaffected by yolk removal.
Survival and sublethal responses of early life stages of pike exposed to low pH in artificial post‐mining lake water
Authors: Duis K. , Oberemm A.
Published: April 2005

The threshold pH for survival of early life stages of pike Esox lucius in post‐mining lakes was determined in a laboratory experiment using artificial water characterized by high concentrations of dissolved Ca, Al, Fe, Mn and SO2/4−. At pH 3·50–4·00, high mortality was observed before hatching. At pH 4·00 and 4·25, hatching rates were reduced compared with the controls (pH 7·40), and many embryos died in a partly hatched state. Hatching success of embryos exposed to pH levels of 4·50 or higher was not affected. However, at pH 5·00 many newly hatched embryos were deformed. Furthermore, pike exposed to pH 4·00–5·00 did not start feeding. At pH 4·75 and below, mortality increased to 100%, and at pH 5·00, only few eleutheroembryos which were in extremely poor condition survived to the end of the experiment. At pH 5·50, survival was in the same range as in the control group, but growth was reduced. Therefore, early life stages of pike are expected to survive in Lustian post‐mining lakes when a pH of 5·50 and above is reached and maintained.
Relationship between oocyte morphology and reproductive strategy in loricariid catfishes of the Paraná River, Brazil
Authors: Suzuki H. I. , Agostinho A. A. , Winemiller K. O.
Published: April 2005

Relationships between ovarian structure, oocyte structure/development, and parental care/life history strategies of six loricariid catfishes common in the upper Paraná River, Brazil were examined with analysis of catch data, relative gonad weight, histology, and microscopy. Three life history strategies were observed. Loricariichthys platymetopon, Loricariichthys sp. And Loricaria sp. produce several small clutches of large eggs over a protracted spawning period. Males of these species guard their eggs and larvae, which are transported as a mass on the ventral surface of the male's body. Hypostomus ternetzi and Megalancistrus aculeatus produce the largest mature eggs and the smallest clutches relative to adult mass. The spawning periods of these species are short, and males guard their broods in excavations. Rhinelepis aspera has high fecundity, high relative mass of mature gonads (both sexes), small mature eggs, and broadcast spawning with no parental care. This species migrates to spawn over firm substrates in channel areas during a contracted period. Mature oocytes of external bearers had the thickest zona radiata, followed by the egg scatterer, and cavity nesters. The thickness of the zona radiata probably is an adaptation to protect the developing egg from injury from abrasion. The zona granulosa appeared to be associated with production of secretions responsible for egg adhesion, and this layer was thickest in mature oocytes of the cavity nesting species, followed by the external bearers. All six species have wide distributions in the Paraná River, tributaries, floodplain lagoons, and the Itaipu Reservoir, but brood guarders tended to be most common in lentic habitats.
First record of the Norway goby in the Adriatic Sea
Authors: Stefanni S.
Published: April 2005

One male and four female Norway gobies Pomatoschistus norvegicus are reported from the Adriatic Sea.
Metabolic adjustments in the common carp during prolonged hypoxia
Authors: Zhou B. S. , Wu R. S. S. , Randall D. J. , Lam P. K. S. , Ip Y. K. , Chew S. F.
Published: April 2005

Biochemical and respiratory changes in the common carp Cyprinus carpio, were studied 6, 24, 96 and 168 h upon exposure to hypoxia (0·5 mgO2 l−1). Modification of kinetic properties of phosphofructokinase (PFK‐1), coupled with a decreased in PFK‐1 activities, were evident in muscle. No changes in kinetics and activities could be observed in muscle pyruvate kinase (PK) and lactate dehydrogenase (LDH). A decrease in muscle citrate synthase (CS) and an increase in muscle cytochrome c oxidase (CCO) were found. The common carp was able to maintain a constant level of muscle glycogen, muscle ATP, and liver CS throughout the 168‐h experimental period. Changes in activities of liver LDH and muscle CCO were observed only at 168 h, which indicates that common carp may switch to alternative metabolic pathway to deal with prolonged hypoxia. A severe decrease in liver glycogen was accompanied by increases in lactate levels in both the muscle and liver. Oxygen consumption rate was reduced under hypoxia, but resumed to normoxic levels within 2 h upon return to normoxic condition. Overall, these results indicate that carp adopt different strategies in an attempt to deal with short term and long term hypoxia in the natural environment.
A 27‐year study of brown trout population dynamics and exploitation in Lake Songsjøen, central Norway
Authors: Langeland A. , Pedersen T.
Published: April 2005

From 1968–1984 (period I), a brown troutSalmo trutta, population in a 70‐ha oligotrophic lake in central Norway was exploited using larger mesh gill‐nets selectively removing the larger fish. From 1985–1994 (period II), intermediate sized fish were removed using smaller‐mesh sizes gill‐nets. Fishing mortality and CPUE were correlated positively with effort and numbers of fish >3 years old for period II. The gill‐net catchability was correlated negatively with spawner biomass and number of trout >3 years old. The significant positive correlation between natural mortality and stock biomass and spawning stock biomass indicated density‐dependent mortality. The significant correlation between spawning stock and recruitment described by the Ricker model, indicated density‐dependent recruitment of 1‐year‐old trout. The fishing regimes in the two periods affected the population dynamics and density differently. Selective removal of smaller fish permitted the larger fish to survive, and was beneficial in reducing fish density and maintaining stocks at low levels, consequently, achieving the expected increase in fish growth rates.
Giant males or dwarf females: what determines the extreme sexual size dimorphism in Lamprologus callipterus?
Authors: Schütz D. , Taborsky M.
Published: April 2005

In the Lake Tanganyika cichlid Lamprologus callipterus, males were >12 times heavier than females, the most extreme sexual size dimorphism in this direction among animals. L. callipterus males construct nests of empty snail shells in which the females breed. If the ancestors of L. callipterus were small cichlids, both sexes may have used shells for shelter. If the ancestors were larger, snail shells could not be used as shelters and would be important only for reproduction. In the field and the laboratory, females bred only in shells and the largest spawned in the largest shells. In the field, females chose larger shells than the average available in males' territories and did not copy the mate choice of other females. They never hid from predators in snail shells and they occurred commonly in areas without any potential shell shelters. In laboratory experiments females used shells only for reproduction and hardly for shelter. Therefore, it seems unlikely that L. callipterus descended from small shell‐brooding cichlids which used shells for shelter, but more likely that the ancestors were of large or intermediate size, and that female size is constrained by the sizes of snail shells, which appear to be optimal breeding substrata.
Size structure of benthic freshwater fish communities in relation to environmental gradients
Authors: Holmgren K. , Appelberg M.
Published: April 2005

The benthic fish communities of 161 Swedish lakes, sampled with multi‐mesh gillnets, were examined by direct gradient analyses with ten environmental factors. A geographic gradient, correlated with climatic factors and productivity, was most important for ordination of species optima. By contrast, the distribution of biomass in different size‐classes and trophic groups, was influenced more directly by local factors such as water quality (pH) and lake morphometry (area and maximum depth). The communities are not only structured at the species level, but also by size‐related allocation of resources, within and between coexisting species. This national survey confirmed patterns observed in previous local field studies, as well as experiments designed for testing mechanisms acting on size‐structured populations. However, it highlighted the need for more extensive studies on if and how large‐scale environmental variation affects the cues for size‐related ontogenetic niche shifts in facultative piscivores, because species such as perch Perca fluviatilis, brown trout Salmo trutta, and Arctic charr Salvelinus alpinus often dominate the benthic fish community.
Abundance, distribution, morphometrics, reproduction and diet of the Izak catshark
Authors: Richardson A. J. , Maharaj G. , Compagno L. J. V. , Leslie R. W. , Ebert D. A. , Gibbons M. J.
Published: April 2005

Holohalaelurus regani was caught in 38% of the 3314 bottom trawls conducted during routine demersal surveys o. the South African west and south coasts from 1986 to 1999. An index of biomass for H. regani has increased on the west coast, from 1606 t in 1986–1993 to 3012 t in 1994–1999, despite c. 130 t being taken annually as by–catch in the demersal fishery. On the south coast, there has also been an increase over the same period, from 793 to 1350 t. Females and juveniles were generally found in shallower water (<300 m) than males, suggesting an inshore nursery area. Male H. regani become mature at 450–500 mm LT, whereas females become mature at 400–450 mm LT. There is reproductive activity throughout the year and fecundity appears to be high. This species is a generalist feeder, with the diet comprising teleosts, crustaceans and cephalopods. H. regani also scavenges offal opportunistically. Its high fecundity, the relative protection of females and juveniles in shallow water that is rarely trawled, its opportunistic diet and its robust nature that may allow it to survive after it has been discarded, have enabled H. regani to increase in numbers, despite indirect fishing pressure.
Homing behaviour facilitates subtle genetic differentiation among river populations of Alosa sapidissima: microsatellites and mtDNA
Authors: Waters J. M. , Epifanio J. M. , Gunter T. , Brown B. L.
Published: April 2005

Significant but subtle differentiation was detected for both microsatellite DNA and mitochondrial DNA among four populations of American shad Alosa sapidissima. The data indicate that straying among rivers is sufficient to permit only marginal population differentiation in this species, but suggest that individual river populations should be managed as distinct stocks. Comparison of the Hudson and Columbia populations, the latter derived from the former over 100 years ago, revealed only a slight reduction in microsatellite DNA variation for the founded population but halving of mitochondrial DNA, consistent with the haploid maternal inheritance of the latter marker. The depleted and endangered James River (Virginia) population and two other Atlantic coast populations exhibited similar levels of microsatellite DNA variation, but mtDNA diversity in the James River was marginally lower than in other Atlantic populations, again consistent with the low effective population size of mtDNA.
Phenotypic variation between dimorphic males in corkwing wrasse
Authors: Uglem I. , Rosenqvist G. , Wasslavik H. S.
Published: April 2005

The age‐frequency distributions for sneaker males (individuals with female secondary sexual characters) and territorial males (individuals with typical male sexual characters) of corkwing wrasse Symphodus melops in a Swedish population did not differ. Otolith analysis revealed that sneaker males were smaller than their territorial male counterparts as juveniles, but there was no evidence of a clear‐cut threshold to determine the subsequent reproductive patterns. Thus, the expression of male morph in corkwing wrasse most likely is related to early growth pattern and the different morphs could be fixed for life. Adult sneaker males in general were smaller than territorial males of the same age. The relative gonad size and the abdomen in sneaker males were substantially enlarged compared with territorial males, but there was no difference in gonad water content between the two types of males. Sneaker males weighed less in relation to their length than territorial males. These results support theoretical sperm competition models which predict that the male morph with reduced attractiveness to females (i.e. sneakers) should invest more into spermatogenesis in order to achieve fertilization than the attractive male morph (i.e. territorial males).
Environmental influences on an exploited anadromous Arctic charr stock in Labrador
Authors: Power M. , Dempson J. B. , Power G. , Reist J. D.
Published: April 2005

Arctic charrSalvelinus alpinusat Nain, Labrador, were influenced by recent variability in measured environmental variables and able to mitigate partially the effects of past conditions in a single year. Weather conditions prevailing during the first winter and sea migration life‐stages also exerted significant influence on measured age and weight characteristics and are argued to play a role in determining the population dynamics of exploited stocks.
Annual cycle of energy allocation to growth and reproduction of yellow perch
Authors: Henderson B. A. , Trivedi T. , Collins N.
Published: April 2005

Growth (length, weight) of yellow perch Perca flavescens in western and west‐central Lake Erie began between June and July, possibly reaching asymptotic size by early winter. Energy density (kJ g−1) of somatic tissue increased markedly from June to September, then declined to low levels by the following spring. Consequently, energy mass (kJ) of somatic tissue increased to September and then declined slowly until March. Ovarian growth began in October, and the size of the ovaries was maximal in April, just before spawning in May. The energy density of ovaries, however, increased to a peak in December, and then declined. The increase in ovary size in the winter, therefore, resulted largely from an allocation of tissue of low energy density. Fecundity and gonad size were correlated with somatic and gonadal energy density. A bioenergetics model was used to describe the monthly allocations of energy to respiration, growth, excretion, and reproduction. Most direct reproductive costs (80%) were incurred from September to December, corresponding to the cycle in the activity of the liver. Energy acquired in the early summer may be critical for determining maturation, fecundity, and egg quality. From 1978 to 1990, <80% of the females from the western and west‐central basins of Lake Erie were classed as spent in July.
Larval growth and development of cultured Pacific bonito
Authors: McFarlane M.B. , Cripe D.J. , Thompson S.H.
Published: April 2005

A method is described for rearing the offspring of wild‐captured Pacific bonito. Six basic stages of post‐embryonic development were determined based on ontogenetic changes in morphology and behaviour. Each stage corresponded with a different food source preference, related to the development of new swimming and predatory behaviours. A controlled environment is required to study the processes underlying development of those behaviours adeptly performed by bonito and other scombrids, including high‐efficiency swimming and visually guided predation on other advanced species.
Re‐examination of the spermatozol ultrastructure of eels: observations of the external morphology of spermatozoa in three species
Authors: Okamura A. , Zhang H. , Tanaka S , Hore N. , Mikawa N. , Utoh T. , Oka H. P.
Published: April 2005

The nuleus of the spermatozoa in both Anguilla anguilla and A. japonica species is asymmetric on the longitudinal axis, being gently curved and elongated with a hook‐shaped superior end directed inside the crescent. A single spherical mitochondrion is located at the superoanterior portion of the nucleus. Nine striae extending from the basal portion of the flagellum run along the right side of nuclear surface. These are always oriented toward the mitochondrial portion and their ends are located on the mitochondrion. These features are seen not only in both Anguilla species but also in Muraenesox cinereus and in other species including other genera of Anguilliformes. It is suggested that these features be considered as common to Anguilliformes.
Temporal repeatability of relative standard metabolic rate in juvenile Atlantic salmon and its relation to life history variation
Authors: McCarthy I. D.
Published: April 2005

There was a strong correlation between the relative standard metabolic rate (rSMR) values of individual Atlantic salmon Salmo salar L. measured 5 and 22 weeks after first feeding in June and October respectively (Pearson's r=0·68, 26 d.f., P<0·001). However, this is a conservative estimate of repeatability as two separate regressions were used to calculate SMR in October due to the separation of the population into an upper modal group made up of early migrants and a lower modal group comprised of delayed migrants. SMR values in June and October were similar (paired t test, t=‐0·85, 27 d.f., P>0·05) when expressed as the percentage deviation from those predicted for a fish of that size based on the body mass/SMR relations in June or October indicating that relative standard metabolic rates were stable over time when food was not limiting. rSMR status was maintained in 19 of the 28 fish (i.e. 68%) between the two measures. rSMR status was correlated with life history strategy: salmon fry with a high SMR in June were more likely to become smolts during the autumn than those with a low SMR.
Vanneaugobius dollfusi Brownell, 1978 a rare fish new to the Adriatic Sea
Authors: Pallaoro A. , Kovačića M.
Published: April 2005

Two specimens of Vanneaugobius dollfusi found among ichthyological material of the Institute of Oceanography and Fisheries, Split and two specimens donated to the Natural History Museum Rijeka provide the first positive records of this species in the Adriatic Sea, and the second record ever for this species.
Biomass and distribution of herbivorous blennies in the southern Great Barrier Reef
Authors: Townsend K. A. , Tibbetts I. R.
Published: April 2005

At the small scale (<1 m2), a correlation between microhabitat availability and abundance of comb–toothed blennies was apparent at Heron Island. Investigation of medium scale (>20 m2) differences, showed that community structure and biomass of herbivorous blennies differed among the 14 geomorphological zones identified. Large scale differences (>10 km2), detected using comparisons between Heron, Lady Elliot and North West reefs, revealed that species composition and biomass, but not density, differed significantly. At Heron Reef, density and biomass of comb–toothed blennies exceeded published estimates for most groups of conspicuous herbivorous fish in equivalent zones. The influence of scale on interpretation of patterns of fish distribution and the role of inconspicuous grazers such as comb–toothed blennies, deserves closer attention.
Growth, diet and metabolism of common wolf–fish in the North Sea, a fast–growing population
Authors: Liao Y.‐Y. , Lucas M. C.
Published: April 2005

The von Bertalanffy growth parameters for common wolf–fish Anarhichas lupus in the North Sea were: male: L∞=111·2 cm, t0=–0·43 and K=0·12; and female: L∞=115·1 cm, t0=–0·39 and K=0·11, making this the fastest growing stock reported. Resting metabolic rates (RMR±S.E.) and maximum metabolic rates (MMR±S.E.) for six adult common wolf–fish (mean weight, 1·39 kg) at 5° C were 12·18±1·6 mg O2 kg–1 h–1 and 70·65±7·63 mg O2 kg–1 h–1 respectively, and at 10° C were 25·43±1·31 mg O2 kg–1 h–1 and 113·84±16·26 mg O2 kg–1 h–1. Absolute metabolic scope was 53% greater at 10° C than at 5° C. The diet was dominated by Decapoda (39% overall by relative occurrence), Bivalvia (20%) and Gastropoda (12%). Sea urchins, typically of low energy value, occupied only 7% of the diet. The fast growth probably resulted from summer temperatures approximating to the optimum for food processing and growth, but may have been influenced by diet, and reduced competition following high fishing intensity.
The structure and dimensions of redds and egg pockets of the endangered salmonid, Sakhalin taimen
Authors: Edo K. , Kawamula H. , Higashi S.
Published: April 2005

Each redd of the Sakhalin taimen Hucho perryi had a V–shaped pot that is specific to this species. The shape of each multiple–egg–pocket redd was a combination of one–egg–pocket redds, and the number of egg pockets in the redd could be estimated from the shape. False redds were small and did not have any V–shaped pots. The factors affecting redd size were examined numerically; consequently, numbers of egg pockets and eggs and female fork length were correlated significantly with tail length. Each egg pocket contained 11–920 eggs (mean: 546·7±95% CL 81·9) and the egg pocket depth was correlated significantly with female fork length. Mean number of redds per female was three, and the number of females could be estimated as one third of the redds.
Stocking impact and allozyme diversity in brown trout from Mediterranean southern France
Authors: Berrebi P. , Poteaux C. , Fissier M. , Cattaneo‐Berrebi G.
Published: April 2005

Analysis of trout from 13 stations on the Mediterranean slopes of the French Pyrenees by 31 presumptive enzyme loci demonstrated the major impact of restocking programmes. Although the annual introgression resulting from these introductions was small, the accumulation of genes of Atlantic origin has resulted in a change in allele frequencies. Genetic disequilibria within and between loci exist. Introgression by genes of domestic (hatchery) origin varied from 0 to 77% among stations. Natural Mediterranean populations show no detectable geographical structure. There was a direct relation between the degree of introgression and heterozygosity. However, restocking could not explain all of the observed genetic disequilibria.
Lipid and fatty acid composition of female gilthead seabream during their reproductive cycle: effects of a diet lacking n‐3 HUFA
Authors: Almansa E. , Martían M. V. , Cejas J. R. , Badí P. , Jerez S. , Lorenzo A.
Published: April 2005

In female sea bream Sparus aurata fed a control diet (C), ovarian levels of neutral lipids (NL) and polar lipids (PL) remained constant between November and March, while a decrease in NL content was observed in liver and muscle. In the same period, liver PL content increased, while no changes were observed in muscle. Between March and June ovarian NL and PL showed a strong decrease, while NL remained constant in liver and muscle. When fish were fed a diet lacking in n‐3 highly unsaturated fatty acids, n‐3 HUFA (D), the pattern observed was similar to that found in the fish fed diet C, with the exception of liver NL, which increased between March and June. In general, the changes in fatty acid content, in both groups of fish, were highly influenced by the diet given to the broodstock, although these effects were greater on ovarian NL and PL than on liver and muscle lipids. Despite the fact that gilthead seabream females continue feeding during the spawning season, they probably make use of their liver and muscle reserves during the gonadal maturation process. Furthermore, the fatty acid composition of the broodstock diet was reflected in the body composition, especially in the ovaries.
Body temperature and seawater adaptation in farmed Atlantic salmon and rainbow trout during prolonged chilling
Authors: Rørvik K‐A. , Skjervold P. O. , Fjæra S. O. , Mørkøre T. , Steien S. H.
Published: April 2005

The core temperature of the rainbow trout Oncorhynchus mykiss (3·5 kg) dropped to 1·0° C during the first 6 h of chilling at 0·5° C, remained stable until 24 h, and dropped significantly to 0·7° C after 39 h. Blood plasma osmolality increased and muscle moisture content decreased gradually with increasing chilling time. After 39 h of chilling, the rainbow trout experienced 40 mosmol l‐1 higher blood plasma osmolality and 2·8% less muscle moisture content compared with initial values. In the Atlantic salmon Salmo salar (5·3 kg), core temperature dropped to 1·3° C and blood plasma osmolality increased significantly during the first 6 h of chilling at 0·5° C, but remained relatively stable throughout the rest of the experimental period. After 39 h of chilling, the salmon experienced 20 mosmol l‐1 higher blood plasma osmolality and 0·5% less muscle moisture content compared with initial values. In rainbow trout muscle moisture content was inversely related to blood plasma osmolality indicating reduced seawater adaptation with increasing hours of chilling. No such relationship was observed in the Atlantic salmon. Hence, changes in plasma osmolality and muscle moisture in the Atlantic salmon do not indicate osmoregulatory failure since the new levels, once established, were maintained throughout the chilling time.
Isolation of a Loma salmonae variant: biological characteristics and host range
Authors: Sánchez J. G. , Speare D. J. , Markham R. J. F. , Jones S. R. M.
Published: April 2005

A Salvelinus‐infecting variant of Loma salmonae, derived from naturally‐infected Chinook salmon Oncorhynchus tshawytscha by serial passage through brook trout Salvelinus fontinalis, has been isolated and amplified. Loma salmonae SV (Salvelinus‐variant) has a high preference for species of Salvelinus (brook trout and Arctic charrS. alpinus) and low virulence and preference for species of Oncorhynchus (rainbow trout O. mykiss, Chinook salmon, cohoSalmon O. kisutch) or Salmo (Atlantic salmonSalmo salar). Although this variant of L. salmonae was different from the original, the differences do not justify describing it as a new species, although definitive determination is pending.
Oxygen consumption of East Siberian cod: no support for the metabolic cold adaptation theory
Authors: Jordan A. Drud , Jungersen M. , Steffensen J. F.
Published: April 2005

Standard metabolic rate (Rs) at 2°C of eight East Siberian cod Arctogadus borisovi, caught in West Greenland, body mass of 601.5 ± 147.6 g (mean ± s.D.), was 40.9 ± 5.9 mg O2 kg‐1 h‐1 and 59.0 ± 6.6mg O2 kg‐1 h‐1 when extrapolated to a standardized 100 g fish. Rs was compared with three other Gadidae, to test the theory of metabolic cold adaptation (MCA). There was no evidence of MCA in the family.
Juvenile fishes in macrophyte beds: influence of food resources, habitat structure and body size
Authors: Grenouillet G. , Pont D.
Published: April 2005

Mean juvenile fish abundance and fish frequency in a large lowland river during low discharge largely differed among the unvegetated and three morphologically contrasted macrophyte habitats. Single separate models revealed that juvenile fish distribution was largely influenced by trophic variables. With the exception of Leuciscus cephalus, which responded mainly to physical variables (depth and substratum), multiple regression models emphasized the importance of trophic variables for fish distribution. For Blicca bjoerkna, L. cephalus and Lepomis gibbosus, habitat shifts with respect to prey size were apparent; small juvenile fishes mainly responded to small zooplankton abundance, whereas large individuals were more influenced by the abundance of large zooplankton. Whatever the species, predictions from multiple regression models were always better for large individuals. Small juvenile fishes appeared to be less affected by the habitat variables measured, and exhibited more uniform spatial distribution. The relative importance of trophic resources and habitat physical structure among macrophyte types for fish‐habitat relationships is discussed, and the necessity of quantifying habitat structural complexity is emphasized.
Intraspecific aggression in rosyside dace, a drift‐feeding stream cyprinid
Authors: Rincón P. A. , Grossman G. D.
Published: April 2005

Individual rosyside dace Clinostomus funduloides in a semi‐natural, artificial stream displayed substantial differences in their aggressiveness and could be classified as: (1) non‐aggressive (NA, 18 of 30 rosyside dace), (2) moderately aggressive (MA, 9 of 30) and (3) highly aggressive (HA, 3 of 30). Rosyside dace groups, however, did not exhibit linear dominance hierarchies and fish size was only weakly correlated with the number of aggressive acts performed per individual. Small rosyside dace (<56 mm LF) were always non‐aggressive, but larger fish were present in all three aggression classes. The difference in size between the contestants was significantly, although not very strongly, correlated with the probability of winning an agonistic interaction (r 2=0·39). Aggressive rosyside dace may have ultimately gained higher fitness than less aggressive ones. HA individuals occupied the upstream‐most position within foraging groups significantly more often than other rosyside dace. This location should be the most profitable one because its occupant will be the first to encounter prey. HA rosyside dace also occupied significantly higher focal velocities that were closer to energetic optima than MA and NA ones. They also had greater foraging rates and were less solitary than less aggressive fish, but these differences only were significant at the P=0·066 and P=0·081 level, respectively. Finally, HA fish performed significantly more aggressive acts and feedings backwards than other individuals. Despite these differences, the effects of intraspecific aggression in rosyside dace appeared less substantial than those that have been observed in stream salmonids.
Cadmium delays growth hormone expression during rainbow trout development
Authors: Jones I. , Kille P. , Sweeney G.
Published: April 2005

Growth hormone (GH) mRNAs were first detected in rainbow trout Oncorhynchus mykiss during organogenesis (stage 29) within a control group while GH expression in cadmium exposed embryos was not detected until a later organogenic period (stage 31). GH transcripts were subsequently detected at all further developmental stages analysed within both treatment groups. These included hatching (stage 32), larval development (stages 33, 34, 35 and 36) and first feeding (stage 37). These results confirm that the GH axis is functional during early rainbow trout development and demonstrate an in vivo endocrine disrupting capacity at the molecular level for cadmium in teleosts. This is of particular relevance to freshwater habitats as heavy metal induced endocrine disruption may be a contributing factor in the decline of salmonid populations.
Association between growth, body condition and anti‐predator behaviour in maturing and immature brown trout parr
Authors: Dannewit J. , Petersson E.
Published: April 2005

In spring there were significant differences between maturing and immature brown trout Salmo trutta in anti‐predator behaviour to pike and heron models when all behaviours were combined in multivariate analysis. However, the time until the trout visited the patch in the experimental tray where predators attacked was the only variable that alone significantly differed between maturity groups; following transfer between the rearing tank and the experimental tray, maturing fish visited this patch sooner. The difference in anti‐predator behaviour coincided with differences developing between the groups in both growth rate and condition factor. Maturing fish showed higher growth rates and exceeded immature fish in condition factor from spring onwards. In a summer experiment, no differences in anti‐predator behaviour were observed between maturing and immature fish. It is concluded that increased risk‐taking to facilitate higher food intake is probably the behavioural mechanism responsible for the comparatively greater increases in growth and body condition observed among maturing fish in spring.
Inheritance of caudal peduncle banding in the spike‐tailed paradisefish
Authors: Frankel J. S.
Published: April 2005

Segregation patterns observed in the progenies from 13 different crosses of the spike‐tailed paradisefish Pseudosphromenus cupanus support the hypothesis that caudal peduncle banding is controlled by a major effect gene exhibiting the classical monohybrid Mendelian pattern of inheritance.
The photoreceptor system in the retinae of two dogfishes, Scyliorhinus canicula and Galeus melastomus: possible relationship with depth distribution and predatory lifestyle
Authors: Bozzanao A. , Murgia R. , Vallerga S. , Hirano J. , Archer S.
Published: April 2005

The small spotted dogfish Scyliorhinus canicula and the blackmouth dogfish Galeus melastomus, whose depth distributions overlap in the upper part of the slope (c. 500 m depth), where they have access to the same prey community, have well‐developed eyes and a pure‐rod retina with a single layer of photoreceptors. Interspecific differences in rod outer segment length (LROS) within retinal regions were found. In the periphery and the retinal centre G. melastomus showed a LROS 24 and 30% longer, respectively, than S. canicula and, therefore, a potential for increased sensitivity. In both species longer LROS were always found in correspondence with the retinal centre where the ganglion cell topography formed a horizontal meridian that allowed for better discrimination of the horizon in the visual field. In this area LROS reached 53·4±4·1μm in S. canicula and 77·1±10·5μm in G. melastomus against 46·3±4·2μm and 61·1±10·1μm in the retinal periphery. No significant differences were recorded in LROS and rod density during growth. In both species, a rapid increase of theoretical visual acuity was found to be related to an increase in fish LT and lens size. Visual acuity ranged between 1·7 and 3 cycles degree‐1 in S. canicula and 2·4 and 4·2 in G. melastomus. The G. melastomus rod visual pigment showed the characteristic spectral adaptation to vision in deep‐water (λmax of 481 nm), but was also well placed to detect the bioluminescence of some of its main prey species. In S. canicula the visual pigment absorption (λmax of 496 nm) was more typical of shallow water living fishes. The opsin sequences of the two visual pigments are discussed and key amino acid sites were identified where sequence changes could be responsible for the spectral absorption differences between the two species. The possible relationship between LROS, visual acuity, visual pigment absorption, depth distribution and feeding behaviour are discussed.
Gut morphology and function inAtherinops affinis(Teleostei: Atherinopsidae), a stomachless omnivore feeding on macroalgae
Authors: Logothetis E. A. , Horn M. H. , Dickson K. A.
Published: April 2005

The marine silversideAtherinops affinishas a short, simple gut and no obvious stomach or physical mechanisms for breaking down algal cells even though its diet in many estuarine habitats is primarily green macroalgae. Silverside from the Upper Newport Bay estuary in southern California had: (1) assimilation efficiencies from a green algal diet of 54% (total organic material), 74% (carbon), 84% (nitrogen), 89% (protein) and 81% (energy), values typical for marine herbivorous fishes; (2) an alkaline gut and no pepsin activity, thus confirming that the fish lacks a stomach; (3) relatively high amylase activity and low trypsin and lipase activities, a digestive enzyme profile expected in a fish consuming a high‐carbohydrate, low‐protein and low‐lipid diet. The fish appears to be capable of functional herbivory and can be classified tentatively as a type III herbivore based on its possible use of pharyngeal jaws for lysis of algal cells.
Anti‐Predator behaviour of naïve compared experienced juvenile roach
Authors: Jachner A.
Published: April 2005

Juvenile roach Rutilus rutilus without any previous contact with predatory fishes reacted to the presence of alarm substances more intensively than fish with previous experience. Among several types of behavioural response observed, some, such as hiding, were not registered in experienced fish. The most pronounced difference between the two juvenile fish categories was manifested in feeding. Naïve fish used more time for feeding than experienced ones. The experiment showed that alarm substance originating from small and young and medium roach induced a stronger reaction than the substance extracted from large and oldéê fish.
BRIEF COMMUNICATIONS Persistence times of four amphipod species in the stomachs of brown trout
Authors: MacNeil C. , Elwood R. W. , Dick J. T. A.
Published: April 2005

Four amphipod species fed to brown trout Salmo trutta persisted in an easily identifiable form in trout stomachs for similar lengths of time. The data also allowed estimation of the maximum length of time ingested amphipods could persist in an identifiable form in brown trout stomachs at different temperatures. The data are thus useful in assessment of fish feeding patterns on amphipod assemblages in the laboratory and field.
Evidence of freshwater feeding by adult salmon in the Tana River, northern Norway
Authors: Johansen M.
Published: April 2005

In the River Laksjohka, a tributary of the Tana River (northern Norway), stomachs from 45 out of 133 adult Atlantic salmon Salmo salar contained food items of terrestrial and freshwater origin. In the neighbouring River Maskejohka, none of 18 sampled stomachs contained any food items.
The uptake of foreign ferritin by macrophages in the spleen, trunk kidney and liver of platy
Authors: Leknes I. L.
Published: April 2005

Melano‐macrophage centres in the spleen and liver of platy Xiphophorus maculatus contain iron and may recycle iron compounds. The sinusoidal tissue in the platy spleen and trunk kidney can take up much foreign ferritin, and may clear the circulation for waste and foreign macromolecules and particles.
Organ differentiation in newly hatched common wolffish
Authors: Falk‐Petersen I. B. , Hansen T. K.
Published: April 2005

Wolffish Anarhichas lupus (Anarhichadidae) hatch from large demersal eggs (c. 5–6 mm) after a long incubation period (c. 800–1000 degree days) at 20–25 mm LT with a juvenile appearance: a small yolk sac, pigmented but partly transparent skin densely supplied with mucous cells, well developed body musculature and a cartilaginous skeleton. The results of histomorphological studies illustrate the apparent functionality of tissues and organs at hatching. The mucosa of the oral cavity and various parts of the digestive channel are well differentiated and the cellular characteristics are described within each region. A stomach with gastric glands is established before hatching. The pancreas has well developed endo‐ and exocrine tissue and the hepatocytes are vacuolized. The kidney tissue has numerous tubuli and haematopoietic tissue in the bilobed head region. The spleen, thymus and thyroid glands also appear mature. Cones are dominant in the visual cell layer of the retina.
Ultrastructure of spermatogenic cells and spermatozoa in Hoplias malabaricus (Teleostei, Characiformes, Erythrinidae)
Authors: Quagio‐Grassiotto I. , Negrão J. N. C. , Carvalho E. D. , Foresti F.
Published: April 2005

The differentiation of spermatids in Hoplias malabaricus is characterized by chromatin compaction, flagellum development, nuclear rotation, nuclear fossa formation, and excess cytoplasm elimination. In the resulting spermatozoon, the head is round and the nucleus contains chromatin compacted in thick filaments, peripherically arranged, to a central electron‐lucent area. The acrosome is absent. The nuclear fossa is eccentric but not pronounced. The proximal centriole penetrates it and is oblique to the flagellum. The long midpiece has several converging elongate vesicles, forming membranous hoops in the initial segment of the flagellum, but has no cytoplasmic channel. The mitochondria are elongate and branched or C‐shaped and located around the initial segment of the axoneme. The lateral flagellum does not show lateral projections. The ultrastructural characteristics of H.malabaricus spermatozoa are similar to the Cypriniformes.
The growth history of anadromous white‐spotted charr in northern Japan: a comparison between river and sea life
Authors: Morita K.
Published: April 2005

Anadromous white‐spotted charrSalvelinus leucomaenisin a natural river in northern Japan migrated to the sea mainly at age 3+ years. Sea‐run charr grew faster than parr, particularly as first time migrants. Sea‐run charr repeated seaward migration up to three times; the observed maximum age was 5+ years old. The likelihood ratio test identified significant differences in asymptotic size and individual growth variability between parr and sea‐run charr. Sea‐run charr had an asymptotic size (L∞) twice as large as parr, while the growth parameter (K) was similar between sea‐run and parr. Growth variability was higher for parr than for sea‐run charr.
Estimates of survival of stream‐dwelling brown trout using
Authors: Olsen E. M. , Vollestad L. A.
Published: April 2005

Estimated monthly apparent survival of stream‐dwelling brown trout Salmo trutta in south‐east Norway was higher in winter than in summer, and lower in Alpine bullhead Cottus poecilopus sites than in allopatric sites. Apparent survival denotes true survival x local site fidelity. Emigration may also explain differences in apparent survival. All brown trout included in this Study were at least 1 year old.
The relationship between the exotic predators Micropterus salmoides and Serranochromis robustus and native stream fishes in Zimbabwe
Authors: Gratwicke B. , Marshall B. E.
Published: April 2005

Samples of fish were collected from 42 stations in streams around Harare, Zimbabwe. The total abundance of fish was lower by 50% or more at stations where the exotic predators Micropterus salmoides and Serranochromis robustus were present compared with stations where they were absent. The greatest differences in density occurred among small Barbus species, whose populations were 86% lower (S. robustus alone) and 99% lower (M. salmoides alone). Populations of small rock and sand catlets were less dense when S. robustus, but not M. salmoides, was present probably because the latter did not enter the riffles where the catlets live. These predators apparently did not affect densities of certain other species in the system that were either cryptic, bottom‐dwelling forms or too large. Low Barbus diversity and abundance in streams containing exotic predators is of concern because this group of fluvial fishes is threatened throughout southern Africa by dam‐building, pollution, and other factors.
Comparative growth performance of diploid and triploid European sea bass over the first four spawning seasons
Authors: Felip A. , Piferrer F. , Zanuy S. , Carrillo M.
Published: April 2005

During their 3–4 first years of life, triploid sea bass Dicentrarchus labrax grew in a similar fashion to diploids in fork length but more slowly than diploids (P<0·05) in body weight, even when the diploids reached full sexual maturity. However, from 48–53 months of age triploids exhibited non‐significantly higher instantaneous growth rates, and thus when fish were 4 years or older, differences in weight with diploids were no longer apparent, suggesting that triploidy could be of benefit in the culture of large (>1 kg) sea bass. The condition factor was reduced in both ploidies during the spawning season which took place in winter when the temperature was low. These observations suggest that any growth advantage in triploids, which were functionally sterile, may be offset by unfavourable environmental conditions. Thus, the potential gain of triploid fish, because they do not direct energy to gonadal growth, could not overcome the effects of low temperature on somatic growth, which coincided with the spawning season. This suggests that the low growth of this species during winter is more a consequence of low temperature than of the energetic cost associated with reproduction. On the other hand, the lower hepatosomatic index in triploid females in contrast to diploid females might be indicative of the lack of gonadal oestradiol‐mediated hepatic synthesis of vitellogenin. Also, erythrocyte and haematocrit measurements showed an increased nuclear and cellular volume in triploids, but with similar cell numbers to those of diploids, respectively.
Application of otolith analyses to investigate broad size distributions of young yellow perch in temperate lakes
Authors: Fitzgerald D. G. , Dale A. R. , Thomas M. V. , Sale P. F.
Published: April 2005

Otolith analyses were used to back‐calculate young‐of‐the‐year (YOY) yellow perch Perca flavescens hatch‐date estimates to interpret broad length distributions observed within a small Great Lake, Lake St. Clair, and a small inland lake, Lake Opinicon, during 1998. For the Great Lake, the earliest observed hatch date occurred 2 weeks after suitable water temperatures and latest hatch dates occurred the same week temperatures were considered too warm for spawning. For the inland lake, the earliest hatch date occurred 4 weeks after suitable water temperatures and the latest hatch dates occurred 2 weeks after the water temperatures were considered too warm for spawning. It is inferred that spawning in each lake had a duration of >9 weeks. This suggests that natural perch populations can protract their spawning season opportunistically under the appropriate environmental cues. During 1998, these cues involved a shortened winter, earlier spring, and slow warming to typical summer temperatures, caused by the El Niño‐Southern Oscillation. Time of YOY hatch determined the absolute opportunity for growth and resulted in a match or mismatch with optimal foraging conditions and contributed to the development of the observed YOY length distributions.
A revised synonymy of Telmatochromis temporalis (Teleostei, Cichlidae) from Lake Tanganyika (East Africa)
Authors: Hanssens M. , Snoeks J.
Published: April 2005

The taxonomic status of the nominal species Telmatochromis temporalis, T. lestradei, T. burgeoni and Julidochromis macrolepis has been reviewed. The synonymy of T. lestradei with T. temporalis is confirmed. A comparison of Telmatochromis burgeoni with Telmatochromis temporalis revealed no significant differences either. Hence T. burgeoni is considered synonymous with T. temporalis. Examination of the type of Julidochromis macrolepis showed it to be conspecific with Telmatochromis dhonti and not with T. temporalis, as had been suggested.