bluuebunny/crossref_metadata_2025 huggingface dataset:
Breeding sounds of male Padogobius nigricans with suggestions for further evolutionary study of vocal behaviour in gobioid fishes
Authors: Lugli M. , Torricelli P. , Pavan G. , Miller P. J.
Published: April 2005

The male Arno goby Padogobius nigricans courts ripe females by emitting sounds at a high rate, mainly from the nest hollow. Laboratory observations revealed that each sound is an almost pure tone wave showing marked amplitude modulation and decrease of frequency throughout its length. The mean tone frequency averaged 79.4 Hz and the sound duration averaged 327 ms. Both these sound parameters were significantly affected by the temperature of the water. Acoustic behaviour during sexual interactions was compared for tank‐confined males and males from a community group. The fact that acoustic activity of the male peaked when the female stayed motionless at the nest entrance suggested that the sound emitted by the male P. nigricans has a role as an advertising signal. Observation of spawning behaviour showed the emission of sounds by the male rapidly diminished and eventually ceased shortly after the beginning of oviposition. Thus, the male sound seems not to be a functional component of the spawning behaviour. Finally, data on vocal behaviour of this species were examined within a comparative framework, also taking into consideration phylogenetic relationships between Italian freshwater gobies.
Development of spinal deformities in Atlantic salmon and Arctic charr fed diets supplemented with oxytetracycline
Authors: Toften H. , Jobling M.
Published: April 2005

Some individuals within populations of Atlantic salmon Salmo salar and Arctic charr Salvelinus alpinus fed diets supplemented with oxytetracycline (OTC) developed spinal deformations. Possible differences in feed intake and growth of spinally deformed fish relative to fish without any deformities were investigated. Amongst Atlantic salmon, 17% of the fish fed OTC‐supplemented feed developed spinal fractures, whereas none of the fish receiving the basic feed did so. Despite deformation of the spinal column, the injured fish continued to feed and grow, but at lower rates than unaffected individuals. In contrast to Atlantic salmon, Arctic charr showed no signs of spinal fractures at any time during the 65‐day experiment.
The effect of emersion and handling on the nitrogen excretion rates of Clarias gariepinus
Authors: Buttle L. G. , Uglow R. F. , Cowx I. G.
Published: April 2005

African catfish Clarias gariepinus (x̃=119.9&30.6 g) were exposed to periods of emersion (5, 30, 60, 90 and 180 min) and the ammonia and nitrogen excretion rates measured following re‐immersion. Immediately following re‐immersion (0–30 min), the ammonia excretion and relative ammonia excretion was greatest for the 5‐min emersion gro up. Exposure to extended periods of emersion resulted in a decrease in total nitrogen excretion, notably ammonia excretion, although no significant changes were observed in the non‐ammonia component of C. gariepinus.
Spatial aspects of genetic differentiation of the European chub in the Rhone River basin
Authors: Guinand B. , Bouvet Y. , Brohon B.
Published: April 2005

Starch‐gel electrophoresis was used to examine genetic differentiation at four polymorphic loci in the European chub Leuciscus cephalus from 27 samples and three main areas of the Rhone River basin in France. The Upper Rhone samples appeared to be genetically distinct at locus PGM‐2* from the Lower Rhone and Saone‐Grosne samples according to the constant row total‐multiple correspondence analysis (CRT‐MCA), which allowed the estimation of multivariate Fst equivalents. No difference between Lower Rhone and Saone‐Grosne samples was revealed by the global analysis considering the three areas. However, distinct local analyses in the three areas showed that the spatial structure of genetic variability was dissimilar in these last two areas, suggesting a non‐equilibrium process under the influence of dams in the Lower Rhone, and isolation by distance in Saone system. Isolation by distance was also suggested for the Upper Rhone samples.
Juvenile recruitment, growth and maturation of Lipophrys pholis (Pisces: Blenniidae), from the west coast of Portugal
Authors: Faria C. , Almada V. C. , Gonçalves E. J.
Published: April 2005

Data on the juvenile recruitment, growth and size at maturation of Lipophrys pholis in Portuguese waters are compared with the information available on the biology of this species at higher latitudes. In Portugal, recruitment extends for a much longer period, young fish grow faster and sexual maturation is earlier than at higher latitudes. There is a delay of 2–3 months between the appearance of the first eggs on the shore and the recruitment of the first juveniles to the pools.
Length/weight relationships of fishes in a diverse tropical freshwater community, Sabah, Malaysia
Authors: Martin‐Smith K. M.
Published: April 2005

Length/weight relationships are described for 16 species of tropical freshwater fishes. Two important morphological groups are recognized (“flattened” and “heavy‐bodied”) along with two species of eel‐like fish. Common regression equations are given.
The bias associated with the dispersion of length at age in the estimation of growth and mortality parameters from uni‐modal length‐frequency data
Authors: Bowker D. W.
Published: April 2005

Values of M and M/K extracted from simulated uni‐modal length‐frequency data representing 28 fish stocks were biased. The bias exceeded 20% when the life span of the stock was <5 or >15 years.
Increased production of docosahexaenoic acid (22: 6 n‐3, DHA) in catfish nutritionally stressed by the feeding of oxidized oils and the modulatory effect of dietary α‐tocopheryl acetate
Authors: Baker R. T. M. , Davies S. J.
Published: April 2005

Production of hepatic docosahexaenoic acid in juvenile Clarias gariepinus was significantly increased (P <0.05) by ingestion of rancid diets and this effect was modulated by dietary vitamin E. This has not been described previously in fish. Causal mechanisms are postulated.
Effect of temperature on the optimal substrate for β‐oxidation
Authors: Egginton S.
Published: April 2005

The enzyme carnitine palmitoyl tranferase (CPT) is able to use a range of fatty acids as substrates, with some variation in catalytic rate among tissue. The substrate giving maximal activity of the enzyme under optimal conditions (C16: 1) is similar in trout, salmon, goldfish, eel and tilapia. There is no evidence that thermal acclimation affects substrate preference for β‐oxidation.
Compensation in individual growth rates and its influence on lake trout population dynamics in the Michigan waters of Lake Superior
Authors: Ferreri C. P. , Taylor W. W.
Published: April 2005

The role of compensatory mechanisms in the population dynamics of lake trout in the Michigan waters of Lake Superior was explored during three time periods: the pre‐sea lamprey period, prior to 1950 when lake trout were at a relatively high abundance and the fishery was the primary source of lake trout mortality; the sea lamprey dominant period, from 1951 to 1961 when lake trout were at a very low abundance due to sea lamprey predation and overexploitation; and currently, from 1985 to 1993 when wild lake trout abundance was at a moderate level. The role of compensatory changes in growth and fecundity rates of lake trout in the Michigan waters of Lake Superior was evaluated using a life table approach. Individual growth and fecundity rates were calculated and compared between time periods. These rates were used to determine age‐specific fecundity which, along with age‐specific survival, were incorporated into a Leslie projection matrix to calculate the finite rate of population increase (λ). Individual growth rates and age‐specific fecundity rates changed in response to the different levels of lake trout abundance during each of the study periods. Lake trout during the sea lamprey dominant period, which experienced the lowest abundance and highest mortality levels, exhibited the fastest individual growth rates and the highest age‐specific fecundity. These high rates contributed to the relatively large compensatory scope exhibited by lake trout during the sea lamprey dominant period as compared to lake trout during the pre‐sea lamprey or the current periods which are associated with higher levels of abundance.
Presence of primary and secondary males in a population of the protogynous Synbranchus marmoratus
Authors: Lo Nostro F. L. , Guerrero G. A.
Published: April 2005

Synbranchus marmoratus, the ‘swamp eel’, is a protogynous diandric fish. The primary and secondary males can be distinguished from each other easily by differences in gonadal morphology. Primary males have lobular, unrestricted testes with central efferent ducts. The secondary male has a ‘lamellar’ testis, efferent ducts are present in the ventral region (new formation), lateral supports and it is covered by the former ovarian capsule. The length of primary male varies from 13 to 88 cm while secondary males range from 56 to 91 cm. Transitional individuals vary between 45 and 60 cm in length. The swamp eel population studied is composed of 80% primary males and 20% secondary males. Although gonadosomatic indices are always higher in primary males, they increase in secondary ones as the newly acquired stage progresses. The lamellar organization of the gonad of secondary males, the absence of this kind of testis in individuals smaller than 56 cm, and the presence of hermaphroditic fish, is evidence for protogyny in this species.
Muscle development in the tambaqui, an important Amazonian food fish
Authors: Vieira V. L. A. , Johnston I. A.
Published: April 2005

Eggs of the tambaqui Colossoma macropomum were incubated at 28 and 31) C. Somitogenesis started shortly after the formation of the neural plate and notochord. New somites were added at the rate of one every 13 min at 28) C and one every 11 min at 31) C. Myogenesis started in the most rostral myotomes at the 9‐somite stage and proceeded in a caudal direction. Mononuclear myotubes with the morphological characteristic of muscle pioneer cells were observed lateral to the notochord. The majority of myotubes were formed from the fusion of 3–6 spindle‐shaped myoblasts. Myofibril synthesis started soon after cell fusion at the periphery of myotubes. Close membrane contacts and ‘gap’‐type junctions were observed between myotubes, immature muscle fibres and at the inter‐somite boundary, suggesting that the cells were electrically coupled. Embryos exhibited rhythmic movements at the 20‐somite stage, and hatched at the 29–30‐somite stage 15–18 h post‐fertilisation (PFT) at 28° C and 11 h PFT at 31° C. Larvae hatched at a comparatively early stage of development prior to the completion of somitogenesis and the formation of eye pigment, pectoral fins and jaws. The myotomes comprised a single superficial layer of well‐differentiated muscle fibres which contained abundant mitochondria, overlying an inner core of myotubes (presumptive white muscle layer). Differentiation and growth during the larval stages was extremely rapid, and the juvenile stage was reached after little more than 6 days at 28° C.
Comparative study of reproductive biology in single‐ and multiple‐spawner cyprinid fish. I. Morphological and histological features
Authors: Rinchard J. , Kestemont P.
Published: April 2005

To clarify the dynamics and regulation of oogenesis in single‐ and multiple‐spawning cyprinid fish with group‐synchronous oocyte development, a multidisciplinary approach to their reproduction was undertaken using three species from the River Meuse (Belgium): the roachRutilus rutilusas a single spawner, and the bleakAlburnus alburnusand the white breamBlicca bjoerknaas multiple spawners. The gonadosomatic index (GSI) and histomorphometric changes (distribution of oocyte size, relative proportion of the various oocyte stages) in the ovary are compared. Different patterns of GSI and oocyte growth were observed both between the single‐ and multiple‐spawner fish and between the two multiple spawners. Maximum GSIs were higher in roach (21%) than in bleak and white bream (17.7 and 14.5%, respectively), and compared to the rapid decline of GSI in the roach population, the GSI of multiple spawners decreased progressively during the spawning season. In roach, a short gonadal quiescent period and an early onset of vitellogenesis was recorded from late summer onwards whereas, in bleak and white bream, exogenous vitellogenesis was not systematically observed before winter. A protracted spawning season and/or a low water temperature in autumn are hypothesized to explain this long period of gonadal quiescence. In bleak, during the spawning season, the oocytes recruited arose from the stock of endogenous vitellogenesis and attained the final maturation stage very rapidly. This recruitment occurred during the whole spawning season. In white bream, the differentiation of vitellogenic oocytes from smaller oocytes was completed before the onset of the spawning season. During the spawning period, the proportion of vitellogenic oocytes decreased progressively whereas the percentage of oocytes in the final maturation stage remained approximately constant.
Assessing seasonal changes in stock composition of Atlantic salmon catches in the Baltic Sea with genetic stock identification
Authors: Koljonen M.‐L. , McKinnell S.
Published: April 2005

The feasibility of using genetic stock identification to analyse seasonal changes in stock compositions of Atlantic salmon catches in the Baltic Sea was examined. The analysis employed seven variable allozyme loci from most of the potentially contributing stocks (16) from Finland and Sweden. Catch samples were collected from Finnish salmon fisheries in the eastern Bothnian Sea during the 1992 fishing season. Simulation studies were used to evaluate the feasibility of identifying Baltic salmon stocks with allozyme data. Special attention was paid to analysing the wild production of salmon stocks. Clear seasonal differences in stock composition were found. The estimates were compared with smolt production and Carlin‐tag data. The proportions of the Neva and Oulujoki river stocks could be estimated as individual stocks, whereas the contributions of the remaining stocks were estimated as four composite stock groups. One of the groups consisted of wild stocks from the rivers Kalixälven and Simojoki. Identification of this group, which could be used as an index of wild production in the catches, requires catch sample sizes >300 salmon if <15% error is required.
Ovarian development associated with first maturity in three Antarctic channichthyid species
Authors: Everson I. , Kock K.‐H. , Parkes G.
Published: April 2005

It has been known for some time that yolk deposition and final ovarian maturation were prolonged processes for many Antarctic fish. The adolescent phase in three species of channichthyid has been studied, based on an extensive series of samples over five seasons. Samples were obtained during a series of abundance estimation surveys on the shelf around South Georgia. Fish were measured, and sex and maturity stage determined from macroscopic examination of the gonads. It was found that for female Champsocephalus gunnari and Pseudochaenichthys georgianus the adolescent phase lasts <1 year but in Chaenocephalus aceratus it lasts for nearly 4 years.
Vertebral number in Ponto‐Caspian gobies: phylogenetic relevance
Authors: Simonović P. D. , Nikolić V. P. , Skora K. E.
Published: April 2005

Modern and fossil Atlanto‐Mediterranean Gobius spp., are distinguished from the derived Ponto‐Caspian genera Neogobius and Proterorhinus by 11 v. 12 precaudal and 17 v. 19 caudal vertebrae.
Dominance in demand‐feeding behaviour in Arctic charr and rainbow trout: the effect of stocking density
Authors: Alanärä A. , Brännäs E.
Published: April 2005

The effects of stocking density on the demand feeding behaviour of Arctic charr Salvelinus alpinus and rainbow trout Oncorhynchus mykiss were evaluated using demand feeders in combination with a monitoring system based on automatic passive integrated transponders. The proportion of total bites accounted for by top‐ranked charr and trout decreased from 87 to 15% and from 66 to 15%, respectively, when moving from the lowest to the highest densities, indicating that the ability of the highest‐ranked fish to monopolize the demand feeders was reduced at high densities. However, when the individuals were grouped into quartiles, based on their individual rank, both charr and trout ranked within the upper quartile accounted for the majority of bites independent of stocking density (87 and 72% of the total, respectively). Instead of there being a single dominant individual, as was the case under low density conditions, a small group of individuals dominated the actuation of the trigger at high densities. The two species responded differently to crowding, with the total daily bite activity of charr increasing linearly with increasing density, whereas the corresponding relationship was quadratic for rainbow trout, with a peak value at 24 to 36kg m−3.
Parasites and parental care in male upland bullies (Eleotridae)
Authors: Stott M. K. , Poulin R.
Published: April 2005

Parental care of eggs by male upland bulliesGobiomorphus brevicepswas studied in the field and in the laboratory, with special emphasis on the effect of infection by trematode cysts. In the field, the proportion of old eggs in the nest affected the time taken by males to return to their nest after being chased away, but only in one year of the study. No effects of male size, male parasite load, number of eggs per nest or nest characteristics were observed. In the laboratory, heavily‐infected males spent more time fanning their eggs than lightly‐infected ones. Smaller males also tended to spend more time fanning than large males. Male size, parasite load and number of eggs per nest had no measurable effect on the aggressiveness of guarding males towards intruders, weight loss in males or egg incubation time. Parental investments did not vary as a function of age of the eggs. All males cannibalized some of their eggs, and there appeared to be a threshold brood size below which males consumed their entire brood. Overall, results were not consistent with those of studies on other fish species, and indicate that rules of investment in parental care may be different for fish inhabiting harsh, unpredictable environments.
The breeding season of Coryphoblennius galerita in Portuguese waters
Authors: Almada V. C. , Carreiro H. , Faria C. , Gonçalves E. J.
Published: April 2005

Coryphoblennius galerita at three sites on the Portuguese coast breeds from February/March to September/October.
Formation of year‐class strength in the bream population in the shallow eutrophic Lake Tjeukemeer
Authors: Mooij W. M. , Van Densen W. L. T. , Lammens E. H. R. R.
Published: April 2005

Formation of year‐class strength of breamAbramis brama, the most abundant fish in shallow eutrophic Lake Tjeukemeer, was studied during a 14‐year period. Although the size of the spawning stock of bream was rather stable during this period, analysis of length—frequency distributions indicates that it comprised only a few year‐classes. The strength of a year‐class was determined at a fork length of about 11 cm, at the end of the second summer. Mortality rates of fish larger than 11 cm were low (<50% year−1). As the number of fish at the end of the second summer was not correlated to the number of 0+ in the previous year, mortality rates during the second summer (ranging from 75.6 to 97.7% year−1) determine the final year‐class strength. These mortality rates were positively correlated to the year‐class strength of 2‐ to 4‐year‐old pikeperch. The abundance of this predator, therefore, is likely to be the most important factor controlling the year‐class strength of bream.
Sexual dimorphism in club cell distribution in the European minnow and immunocompetence signaling
Authors: Irving P. W.
Published: April 2005

Female minnows Phoxinus phoxinus have eight times as many club cells as males in their dorsal skin during the breeding season. The distribution of these cells is androgen sensitive and they may have an antipathogenic function. Since androgens also stimulate development of secondary sexual characters and depresses the immune system the putative role of nuptial coloration as a signal about immune function is discussed.
Seasonal variations in fat content and fatty acid composition of male and female coregonid‘ bondella’ from Lake Maggiore and landlocked shad from Lake Como (Northern Italy)
Authors: Luzzana U. , Serrini G. , Moretti V. M. , Grimaldi P. , Paleari M. A. , VALFRÈ F.
Published: April 2005

The Lake Maggiore bondella Coregonus macrophthalmus use perivisceral adipose tissue for gonadal development (with particular evidence in females), and muscle fat as an energy source. Females use mainly saturated fatty acids (SFA) for energy purposes, while males use monounsaturates (MUFA) also. During vitellogenesis, females can also mobilize fatty acid precursors of gonadal highly unsaturated fatty acids of the ω3 family from muscle tissue, but in both sexes specific retention of docosahexaenoic acid (DHA=22: 6ω3) in muscle is evident. Landlocked shad, unlike several freshwater fishes, can utilize the liver as well as body cavity and muscle as a fat reserve depot. The perivisceral fat stored during the feeding period appears to be utilized mainly for winter energy maintenance requirements. Lipid reserves from liver and muscle are also mobilized to meet the requirements resulting from gonadal development. In particular, females seem to use liver reserves, especially 18: 1ω9, more than males, to meet the demands of ovogenesis. In the muscle, SFA are used mainly for energy purposes. During gonadal development, specific muscular and hepatic ω3 highly unsaturated fatty acids (ω3 HUFA=20: 5 + 22: 5 + 22: 6) and ω6 HUFA (20: 4+22: 4+22: 5) retention is evident in both sexes, while fatty acid precursors of ω3 and ω6 HUFA are mobilized, especially from muscle tissue.
Effects of oestradiol—enriched diet and of feeding with porcine testicular tissue on macroscopic gonadal sex in European eels
Authors: Andersen D. , Boeutius I. , Larsen L. Olesen , Seidler P. Hjulmann
Published: April 2005

Oestradiol–enriched food (25 mg kg‐1 oestradiol) fed for 91 days to small eels (2 or 7 g) with undifferentiated gonads (UD) significantly favoured development of gonads with the macroscopic appearance of ovaries (♀‐gonads) during the next 8 months. Fifty‐four and 51% of control eels and 75 and 78% ofoestradiol‐treated eels developed ♀‐gonads. Minced porcine testicular tissue fed to 2‐g eels for up to 371 days had effects similar to oestradiol‐enriched food (68% with ♀‐gonads), whereas feeding for only 91 days had no effect during the next 8 months. Oestradiol‐enriched food was also fed to larger eels with already macroscopically differentiated gonads (30–70 g; 95% with ♀‐gonads, 5% with ♀‐gonads). After 27 days significantly more eels with a ♀‐gonad or with a mixture of ovary‐like and testis‐like regions in the gonads (♂+♀‐gonads) were found. After 96 days there were 44% with ♀‐gonads, 40% with ♂+♀‐gonads and 16% with ♀‐gonads. Oestradiol thus had a feminizing effect, not only on morphologically undifferentiated gonads but also on morphologically differentiated ♀‐gonads. The presence of sex steroid hormones or their precursors in porcine testicular tissue may also exert a feminizing influence. In all experiments the hormone‐fed groups showed a tendency (not significant) towards increased growth rate. In small eels early rapid growth and differentiation of ♀‐gonads were clearly correlated, both in hormone treated and in control eels. Otherwise no correlation was found between growth rate and gonadal sex.
Population level differences in aggressiveness and their relationship to food density in a stream salmonid (Salvelinus fontinalis)
Authors: Dunbrack R. L. , Clarke L. , Bassler C.
Published: April 2005

The hypothesis that stream salmonids from habitats with low food density will be more aggressive than conspecifics from habitats with higher food density was tested through behavioural observations of wild‐caught young‐of‐the‐year brook charr Salvelinus fontinalis in aquaria. Standing stocks of benthic invertebrates in a high food density habitat were more than double those in a low density habitat and charr from the latter were significantly smaller than those from the former. Charr from the low food density habitat were significantly more aggressive, as indicated by nipping attempts within pairs, than were those from the high food density habitat. Both populations were genetically isolated and food density differences seemed to be related to persistent features of their habitats. This suggests that the observed behavioural differences may have both genotypic and phenotypic Components
Field activity of lake trout during the reproductive period monitored by electromyogram radiotelemetry
Authors: Weatherley A. H. , Kaseloo P. A. , Gare M. D. , Gunndr J. M. , Llpicnik B.
Published: April 2005

Many lake trout Salvelinus namaycush spawn in shallow areas along windswept shores. However, precise determination of time and location of spawning is limited by its nocturnal occurrence, and possibly by some postulated, but unproven, spawning in deep water by certain populations. In White Pine Lake, Ontario, a well‐studied experimental lake, lake trout spawn in two shallow locations where some direct observation is possible. Radiotelemetry apparatus was used in 1991 to obtain records of the electromyograms (EMGs) produced by muscle activity in one adult male and one adult female lake trout, captured from the lake before their reproductive period and returned to the lake at the beginning of the spawning period. Both fish survived, though only the male was detected as active over the main spawning site, where it showed evening EMG activity patterns indicating considerable activity. At other times of day, when not located over the spawning site, but present elsewhere in the lake, the male's EMG (i.e. muscle) values were considerably reduced. At the cessation of the spawning period, the transmitter‐equipped male's EMG record showed no further pattern indicative of high activity during what had formerly been the daily spawning period. The female was tracked as she moved around the lake, but based on both her location and level of EMG activity, is thought not to have spawned. In 1992, a second male was captured, equipped with a transmitter and released again. This fish failed to show spawning activity but, as with the 1991 female, moved fairly considerable distances in the lake. In one instance, in a swim of short duration (6 min), well away from the spawning grounds, this fish displayed EMG activity levels resembling those of the high activity of spawning. The results obtained appear to demonstrate that EMG telemetry could be used to assess the level of muscular activity occurring in lake trout, especially in relation to reproductive behaviour, and when they cannot be directly observed.
Chromosome complements of Gobionellus microdon and Eleotris picta collected in Mexico
Authors: Uribe‐Alcocer M. , Dfíz‐Jaimes P.
Published: April 2005

The karyotype of Gobionellus microdon has a diploid number of 2N = 56 and a fundamental number of FN = 66 with a chromosome formula of 4M + 6sm+46st,a. Eleotris picta has 52
A field observation on the influence of aggressive behaviour on mating success in the European grayling
Authors: Poncin P.
Published: April 2005

The biggest male grayling present on a spawning area was strongly territorial and developed more aggressive behaviours than smaller males. However, its spawning frequency was similar to that of Smaller males.
Geographical and temporal mitochondrial DNA variability in populations of pink salmon
Authors: vl. Brykov A. , Polyakova N. , Skurikhina L. A. , Kukhlevsky A. D.
Published: April 2005

Pink salmon Oncorhynchus gorbuscha from odd and even year generations in rivers of Sakhalin Island, Kuril Island, Kamchatka Peninsula, and Alaska were investigated with five informative restriction endonucleases for mtDNA variation. The odd and even generations from the same rivers of South Sakhalin differed greatly. The time of divergence between the two broodlines was estimated at 0.9‐1.1 Myr. The variability of mtDNA in odd year generations was higher than in even year generations and may have been due to‘ founder’ and/or‘ bottleneck’ effects. The differences among river populations within the Sakhalin region in 1991‐1993 were not significant and this confirms the highly migratory nature of pink compared with other Pacific salmon. The mtDNA samples revealed statistically significant differences between regions. The northern populations (Kamchatka, Alaska) were less diverse in number and frequency of haplotypes than the southern populations (Sakhalin). This suggests that pink salmon originated in the Sakhalin‐Kuril region and that a founder effect during the spread of this species may have restricted the mtDNA variability in other regions.
Spawning migrations in landlocked Atlantic salmon: time series modelling of river discharge and water temperature effects
Authors: Trépanier S. , Rodríguez M. A. , Magnan P.
Published: April 2005

River discharge and water temperature are frequently cited as controlling the upstream migration of adult salmonids to their spawning areas. The results of earlier studies on the effect of these environmental factors were examined. The statistical methods employed in some of these studies failed to consider the serial correlation often found in migration time series. To assess the effects of discharge and temperature on the migratory activity of the landlocked Atlantic salmon (ouananiche, Salmo salar), 12 years of data on spawning migrations in the Mistassini R., Quebec, Canada, were analysed and the results obtained by ordinary least squares regression and time series regression were compared. In six of the 12 years, upstream migratory movement was related negatively to changes in river flow, suggesting that fish favour falling water phases for ascent. Water temperature appeared to have little effect on migratory movement. The mean body size of migrating fish decreased significantly throughout the summer; early migrants were on average 11.4% larger (mean fork length 522mm) than late migrants (469 mm). Larger, 3‐lake‐year salmon migrated 7.2 days earlier than 2‐lake‐year salmon. Because the residuals from ordinary regression exhibited strong autocorrelation, time series regression was more appropriate than ordinary regression for the analysis of migration time Series.
Distribution of aromatic l‐amino acid decarboxylase in tissues of skipjack tuna using l‐DOPA as the substrate
Authors: Nagai T. , Hamada M. , Kai N. , Tanoue Y. , Nagayama F.
Published: April 2005

Aromatic L‐amino acid decarboxylase activity was measured in brain, heart, intestine, kidney, liver, muscle, pyloric caeca, spleen and stomach of skipjack, using L‐3,4–dihydroxyphenylalanine as the substrate. Aromatic L‐amino acid decarboxylase activity was found to be present in all of the organs studied. The highest activity was found in the intestine (1774 μmol min −1 g−1 wet wt of tissue). The liver showed the lowest activity (48.7 umol min −1 g −1).
Overlapping sensitivities of brook trout and brown trout to putative hormonal pheromones
Authors: Essington T. E. , Sorensen P. W.
Published: April 2005

The olfactory systems of brook and brown trout were equally sensitive to prostaglandin F2a and its derivatives, suggesting that these species have similar sex pheromone systems. This may explain partially hybridization behaviour observed between these species.
A review of the biology and ecology of the whale shark
Authors: Colman J. G.
Published: April 2005

The information available on the biology and ecology of the whale shark is reviewed, and is updated from material published since 1986. Research work carried out on the seasonal aggregation of whale sharks at the Ningaloo Reef in Western Australia is summarized. Future research studies on whale sharks in the Ningaloo Marine Park are discussed in the context of management of sustainable whale shark interaction tourism.
The effect of acidification on oogenesis of rainbow trout during sex differentiation
Authors: Zelennikov O. V.
Published: April 2005

Rainbow trout larvae were kept in acid water from 16 to 55 days after hatching. Initially, the acid environment stimulated a significant increase of gametes in the gonads of females at all developmental stages, but after longer exposure the stimulation was replaced by inhibition of gonadal development in the treated fish. In some fish, gamete reserves increased, while in others there was increased growth and maturation of late‐generation oocytes.
On cloacal gestation in angel sharks from southern Brazil
Authors: Sunyem P. S. , Vooren C. M.
Published: April 2005

The anatomy of the reproductive organs of the gravid female angel sharks Squatina Guggenheim and S. occulta was studied in specimens obtained by bottom trawling off southern Brazil from 1980 to 1992. Gestation of the species is lecithotrophic, lasts 11 months and is synchronized at the population level. The ovulation and onset of gestation occur in summer (January–February) and parturition takes place in spring (November‐December). The gestation of Squatina has two phases: uterine gestation during the first 4 months and cloacal gestation during the last 6 months. The transition between these phases occurs in the 5th month (May). During uterine gestation the uteri are turgid, distended longitudinally and transversally, and constricted at both ends. Embryos develop within the closed uteri. During cloacal gestation the dome‐shaped uteri are contracted longitudinally and are constricted near the nidamental gland. At the posterior end, they are distended transversally to form a wide opening into the cloaca. The cloaca is distended longitudinally and transversally. The embryos complete their development within the single, heart‐shaped, uterine‐cloacal chamber, that is open to the exterior through the cloacal Vent.
Female rainbow trout urine contains a pheromone which causes a rapid rise in plasma 17,20β‐dihydroxy‐4‐pregnen‐3‐one levels and milt amounts in males
Authors: Vermeirssen E. L. M. , Scott A. P. , Liley N. R.
Published: April 2005

Previous studies have shown that spermiating male rainbow trout respond to the presence of female urine in the water with significant increases in plasma levels of gonadotrophin II, 17,20β‐dihydroxy‐4‐pregnen‐3‐one (17,20β‐P) and testosterone. The present results show that males only need a single brief exposure to female urine in order to respond; levels of 17,20β‐P rise significantly within 1 h of exposure, and peak between 3 and 4 h. Also, milt amounts increase significantly following exposure of males to female urine. Levels of 17,20β‐P are also related positively to the amount of female urine to which the males are exposed. Furthermore, when live females are placed, out of physical and visual contact, in the same tank as males, levels of 17,20β‐P rise in the same way as in males which are exposed to female urine. However, if females are fitted with urinary catheters (which drain the urine outside the tank), males respond more slowly. These results indicate that urine is the main source of the male ‘priming’ pheromone.
Ciliated epithelium in the developing digestive tract of the larva of the Atlantic halibut, and comparison with that of the cod
Authors: Morrison C. M. , Martell D. J. , Leggiadro C.
Published: April 2005

Two regions of ciliated epithelium are described in the digestive tract of the halibut larva. The anterior region, present by 5 days post‐hatch and still present at 25 days post‐hatch, probably moves water through the branchial openings into the oesophagus and on to the midgut until the mouth forms at about 29 days post‐hatch. A ciliated region was present also in the occluded posterior hindgut, which joins the excretory duct to form a common duct to the exterior. This posterior ciliated region may help to circulate water in the mid‐ and hindgut until the anus opens directly to the exterior, at about 25 days post‐hatch.
Polarizing analysis of the crimped collagen ligament of the maxillary barbel in Parauchenipterus galeatus, and the functional implications
Authors: Royero R. , Neville A. C.
Published: April 2005

A polarizing analysis of the crimped collagen ligament in the maxillary barbel of the catfish Parauchenipterus galeatus showed clearly that the maxillo‐mandibular ligament of this species is formed by two types of collagen fibres. The first is composed of uncrimped, and the second of crimped collagen fibres. An anatomical examination of the muscular and osteological components which act in the movement of the barbel revealed that abduction of the barbel is performed by the extensor tentaculi muscle and the mechanism of adduction by muscular relaxation of the extensor tentaculi combined with release of the stored elastic energy of the maxillo‐mandibular ligament. This ligament has rubber properties and because of this can store energy during abduction (first stage of the cycle of barbel movement). The stored energy is released when the action of the extensor tentaculi muscle ceases. The second half of the locomotory cycle is to return the maxilla to its original position by the antagonistic action of the ligament. The crimping of the ligament permits the take up of slack, allowing greater extension, with less chance of snapping. The connective tissue between the hyomandibular and the maxilla may assist the adduction of the barbel.
Effects of carp serum on the growth of goldfish fin cells in early passage
Authors: Hashimoto H. , Toyohara H. , Yokoyama Y. , Sakaguchi M. , Ozato K. , Wakamatsu Y.
Published: April 2005

The culture medium supplemented with carp serum and fetal bovine serum (FBS) promoted cell growth significantly and induced morphological change of goldfish fin cells in early passage as compared to the medium containing FBS alone. However, these effects were not observed in RBCF‐1, a cell line established from the goldfish fin. The sensitivity of the cells in early passage to carp serum suggests the following possibilities: (1) cells in early passage retain the ability to respond to growth‐promoting factors specifically included in carp serum; and (2) this ability is lost during the process of long‐term culture and/or long‐term culture in FBS eliminates cell groups showing high dependency of cell growth on carp serum.
Evaluation of a variable angle scanning method to estimate relative abundance and distribution of fish using a single‐beam echosounder in shallow lakes
Authors: Gauthier S. , Boisclair D. , Legendre P.
Published: April 2005

The validity of a hydroacoustic procedure was assessed using a combination of horizontal and vertical scanning to map the distribution of targets and to estimate target density in a shallow lake. Three distribution patterns were created using 37–50 artificial targets (metal hex nuts) anchored at known positions. Real and acoustic maps were qualitatively similar. Aggregation indices estimated by hydroacoustics were within 15% of the real values. Target density ranged from 1 to 8 targets per 100 m−3. Estimated target densities were within one target of the real values for 88% of our observations. The variable angle approach was used also to monitor daily and seasonal variations in fish distribution and relative abundance outside the littoral zone. Dace Phoxinus eos × P. neogaeus appeared to use the littoral as a refuge during the day and to migrate to the pelagic zone at dusk. The movements of dace outside the littoral zone were limited to the months of June‐August. The variable angle acoustic approach can be useful to estimate fish distribution and relative abundance in shallow lakes.
The foraging ecology of two pairs of congeneric demersal fish species: importance of morphological characteristics in prey selection
Authors: Labropoulou M. , Eleftheriou A.
Published: April 2005

The feeding habits of two sympatric species pairs of demersal fish (Mullus barbatus‐Mullus surmuletus, Serranus cabrilla‐Serranus hepatus) which occupy the shallow coastal area (25–30 m) in Iraklion Bay were investigated from samples collected on a monthly basis (August 1990 to August 1992). Stomach content analyses revealed that all of them were carnivores, feeding mainly on benthic invertebrates, and that each species consumed a narrow range of prey species with no significant dietary overlap. The morphology of their feeding apparatus was compared to examine the effect of any morphological differences on food selection and resource partitioning between the fish species. The species could be distinguished on the basis of the size of their mouth gape, the number of gill rakers and the length of their intestine. This study shows that each species pair follows a different strategy segregating along food niche dimensions. In particular, M. barbatus and M. surmuletus segregate their feeding niche consuming different prey taxa with similar sizes whereas S. cabrilla and S. hepatus differ considerably with respect to the degree to which prey species contribute to their diets coupled with differences in mean prey sizes.
Insect predation on pike fry
Authors: Le Louarn H. , Cloarec A.
Published: April 2005

Laboratory tests evaluated the predatory impact of the macroinvertebrates Erythromma najas larvae (Odonata, Zygoptera: Coenagrionidae), Notonecta glauca (Heteroptera: Notonectidae), Ilyocoris cimicoides (Heteroptera: Naucoridae), Libellula depressa larvae (Odonata, Anisoptera: Libellulidae), Dytiscus marginalis larvae (Coleoptera: Dytiscidae) and Anax imperator larvae (Odonata, Anisoptera: Aeshnidae) on 3‐, 12‐, 21‐ and 30‐day‐old pike fry Esox lucius. All these insect predators captured and ate pike fry during the test, although the numbers killed varied among species. Dytiscus marginalis, Anax imperator and Notonecta glauca were the most Voracious predators.
Effects of a flow‐gauging weir on the migratory behaviour of adult barbel, a riverine cyprinid
Authors: Lucas M. C. , Frear P. A.
Published: April 2005

Barbel Barbus barbus exhibited substantial movements in the River Nidd between March and July 1994, with some individuals moving nearly 20 km upstream, although there was considerable individual variation. Most upstream movement occurred during May. Fifteen of the 23 fish tracked attempted to pass the weir, and of these six were successful. Barbel tended to approach the weir around dusk and dawn, reflecting observed patterns of localized activity, or at night, but crossed the weir only at night. Those fish which crossed the weir moved substantial distances upstream to spawn, while those that were unsuccessful moved down‐stream. The weir delayed the net upstream progress of all adult barbel. Successful traversal was not closely related to flow or water temperature conditions. The study emphasizes the impact of relatively minor obstructions on the natural migrations of barbel.
Predator attack motivation influences the inspection behaviour of European minnows
Authors: Murphy K. E. , Pitcher T. J.
Published: April 2005

Predator inspection behaviour at different levels of attack motivation (attack status of the predator) was investigated in European minnows Phoxinus phoxinus from a population sympatric with pike Esox lucius, during controlled laboratory experiments. Shoals of minnows performed more predator inspections and formed larger inspection group sizes shortly after an attack by a pike. After inspection, minnows returned to the safety of the main shoal, regardless of predator motivation. Minnows which inspected last‐before and first‐after a strike by a pike modified their behaviour after inspection; they reduced feeding, increased shoaling, flicked their dorsal and pectoral fins and skittered. This behaviour signified alarm and appeared to reflect the severity of the threat posed by the predator at the time of inspection. Fish that had inspected when the pike displayed low attack motivation did not modify their behaviour after inspection to reflect alarm. Information concerning the attack motivation of the predator is probably transferred passively throughout the shoal by changed inspector behaviour and by inspection rate. These data demonstrate that: (1) minnows modified their behaviour after inspection to reflect a predator's attack motivation; and (2) minnows which inspected immediately before a strike appeared to anticipate the future attack and modified their behaviour accordingly.
First record of Ligula intestinalis from stone loach
Authors: Bean C. W. , Kirkwood R. C.
Published: April 2005

The cestode Ligula intestinalis was recorded for the first time from stone loach Barbatula barbatulus. Details regarding their site of capture and intensity of infection are provided.
The relationships between anadromy, sex ratio and parr growth of Arctic charr in a lake in North Norway
Authors: Rikardsen A. H. , Svenning M.‐A. , Klemetsen A.
Published: April 2005

Relationships between the degree of anadromy, sex ratio and parr growth of Arctic charr Salvelinus alpinus were investigated in Lake Storvatn in Hammerfest town, by estimating the densities of resident and anadromous charr in the lake, and by comparing the smolt characteristics of fish captured in the outlet river with those of fish of the same age in the lake. About two‐thirds of the charr older than 5 years were anadromous. The sex ratio of smolts was approximately 1 : 1 and the frequency of mature male parr in the lake was low. As females tended to dominate the mature portion of the anadromous population, there was probably a relatively higher mortality among sea‐run male smolts. The youngest smolts (3+ and 4+) were probably recruited from fast‐growing parr in the littoral zone, while older smolts (>4+) may have been recruited from all habitats in the lake.
Preferences for familiar fish do not vary with predation risk in the European minnow
Authors: Griffiths S. W.
Published: April 2005

In the near‐natural conditions of a fluvarium in the River Frome, U.K., European minnows Phoxinus phoxinus displayed schooling preferences for familiar conspecifics. Schools were composed of 75% familiar fish. The minnows in this river co‐occur with many piscivores, the most notable being the pike Esox Iucius. The preference for familiar shoalmates was not increased by the threat of predatory attack from a model pike, despite the antipredator benefits afforded to individual members of schools of familiar fish.
Thermal resistance and upper lethal temperatures of underyearling Lake Inari Arctic charr
Authors: Lyytikäinen T. , Koskela J. , Rissanen I.
Published: April 2005

Underyearling Arctic charr were acclimated to six temperatures between 6 and 21·5°C and thermal tolerance and resistance were tested after an acclimation period of at least 2 weeks. Resistance times were influenced by acclimation temperature and the highest upper incipient lethal temperature was 23–24°C. An upper limit for cultivation of Lake Inari charr is suggested to be 21°C which is the intercept of the function which represents the upper limit of the thermal tolerance zone.