bluuebunny/crossref_metadata_2025 huggingface dataset:
Steroid hormone profiles and correlative gonadal histological changes during natural sex reversal of sobaity kept in tanks and sea‐cages
Authors: Lone K. P. , Ablani S. , Al‐Yaqout A.
Published: April 2005

The gonadosomatic index of sobaity Sparidentex hasta fits well with the natural spawning season of February‐March. At 12 and 24 months all the population matured as males. However, during this time, between April‐September intersex gonads were seen. From October of the third year of life, females were seen for the first time. These changes in the histology of the gonads were correlated with the hormonal profile. Testosterone showed no significant correlation with sex but 11‐ketotestosterone correlated very well with the mature male gonads and thus can be used for sexing. Oestradiol‐17β higher in sex reversed individuals (females) in the spawning season than in males. The sequence of events in the protandrous sex change of this fish during the first two spawning seasons is male → intersex → male. However, during the third spawning season (age 36–37 months) this sequence is male →intersex → male or female (10–17%).
Temperature, light intensity and plasma melatonin levels in juvenile Atlantic salmon
Authors: Porter M. J. R. , Duncan N. , Handeland S. O. , Stafansson S. O. , Bromage N. R.
Published: April 2005

Plasma melatonin synthesis in juvenile Atlantic salmon Salmo salar decreased with increasing light intensity. Melatonin profiles reflected accurately the photoperiod under which the salmon were maintained. Groups maintained at 12°C showed significantly higher (P < 0·01) levels of dark phase plasma melatonin compared with the groups maintained at 4°C.
Effects of temperature on developmental performance, survival and growth of sea lamprey embryos
Authors: Rodríguez‐Muñcoz R. , Nicieza A. G. , Braña F.
Published: April 2005

This study assesses the influence of thermal regime on the development, survival rates and early growth of embryos of sea lamprey Petromyzon marinus incubated at five constant temperatures (7, 11, 15, 19 and 23° C). The time from fertilization to 50% hatching and from hatching to 50% burrowing were inversely related to incubation temperature. All the embryos incubated at 7° C died at very early stages, while those maintained at 11° C did not attain the burrowing stage. Survival from fertilization to hatching was 61, 89, 91 and 89% at 11, 15, 19 and 23° C, decreasing to 58, 70 and 70% from hatching to burrowing at 15, 19 and 23° C, respectively. Larvae reared during the first 3 months of exogenous feeding in a common environment at constant 21° C, revealed maximum survival for an incubation temperature of 15° C (43% of burrowed larvae) decreasing strongly at 19° C (16%) and 23° C (one suvivor among 240 larvae). Body length at the burrowing stage was maximum for embryos incubated at 19° C, but body mass increased in the interval 15–23° C. Mean incubation temperatures experienced by 117 broods during the embryonic development in the source river were estimated in 15·3±2·30° C and 16·7±1·76° C (mean±1 s.d.) for the periods fertilization‐to‐hatching and hatching‐to burrowing, respectively.
Species‐specific attraction of migratory banded kokopu juveniles to adult pheromones
Authors: Baker C. F. , Montgomery J. C.
Published: April 2005

Juvenile migratory Galaxias fasciatus juveniles or whitebait were attracted to odours produced by adults. The attraction was dependent on concentration with an upstream movement and attraction to the odour chamber at intermediate level concentrations. At a high concentration the migratory response of whitebait was retarded with the majority of fish not moving upstream but remaining in the lower section of the apparatus. There was no response to odours from adults of other galaxiid species, the inanga G. maculatus or koaro G. brevipinnis at any concentration. These results demonstrate G. fasciatus whitebait have the ability to discriminate species‐specific pheromones during their migratory phase, providing evidence of a pheromonal attraction in migratory amphidromous fish which could possibly provide a basis for effective habitat selection.
Gastric evacuation of horse mackerel. II. The effects of different prey types on the evacuation model
Authors: Temming A. , Herrmann J.‐P
Published: April 2005

Gastric evacuation experiments were performed on horse mackerel Trachurus trachurus. Discrete meals of different sizes of krill Meganyctiphanes norvegicus, mysids Neomysis integer, brown shrimp Crangon crangon, and herring Clupea harengus were fed to test the effect of prey type on the gastric evacuation. A general evacuation model without meal size as a variable was fitted to the data on dry weights by means of non‐linear regression. With the exception of mysid evacuation the estimated parameters for curvature, predator weight effect, and temperature effect of the general evacuation model were very similar for all other food types and also confirmed the results obtained with smelt Osmerus eperlanus. In contrast the evacuation of mysids showed a strong exponential curvature, rather the effect of prey size than of prey type. The prey specific evacuation constants of the model revealed a linear relationship to the energy content. A general consumption model for field estimates is presented that can be used for prey types that have not yet been tested in the experiments, provided the energy content is known.
Fertilization dynamics in sockeye salmon and a comparison of sperm from alternative male phenotypes
Authors: Hoysak D. J. , Liley N. R.
Published: April 2005

Sockeye salmon Oncorhynchus nerka sperm maintained high fertility for 10 s after being exposed to water but fertility dropped sharply after that. Eggs also showed limited longevity after being immersed in water, with a large drop in fertility occurring after 20 s of exposure to water. The association between eggs and sperm occurs very rapidly. 80% fertilization success was achieved with 5 s of sperm‐egg mixing and c. 25% was achieved with <0·5 s of sperm‐egg mixing. Sperm from different male age classes differed little in motility and did not differ at all in their propensity to fertilize eggs. The results have important implications for mate choice and sperm competition.
Biochemical characteristics of liver and brain monoamine oxidase from pacu
Authors: Salles C. , Souza R. H. S. , Salles J. B. , Cunha Bastos V. L. F. , Dias R. A. , Cunha Bastos J.
Published: April 2005

Monoamine oxidase (MAO) activity in the liver and brain of the pacu, Piaractus mesopotamicus was determined using a fluorescence assay with kynuramine as substrate. Apparent Michaelis constant values (20·33 μM for liver and 25·85 μM for brain) were similar in these tissues, but in terms of tissue protein MAO activity from liver was 4·5 times higher than from brain. The greater inhibitory effects of clorgyline than of deprenyl on MAO activity from liver and brain of this species suggest that pacu's MAO is a type A‐like enzyme.
A novel artificial habitat collection device for studying resettlement patterns in anguillid glass eels
Authors: Silberschneider V. , Pease B. C. , Booth D. J.
Published: April 2005

The number of glass eels Anguilla australis and A. reinhardtii caught in artificial habitat collectors, made from a PVC base and polyethylene split rope fibres, was related to the number of rope fibre tufts attached to each collector rather than collector area directly. Ageing of collectors in situ to promote algal growth enhanced the catch of glass eels. Glass eels entered the collectors at night primarily during the flood tide, and did not move into the collectors during daylight hours. Glass eel abundance increased with increasing distance from the freshwater drain located in the causeway. The artificial habitat collectors are effective for assessing relative numbers of resettling glass eels and may be useful for studying recruitment and settlement patterns of other anguillid eel species, as well as identifying areas and habitats within a catchment that provide important shelter for glass eels. Sampling glass eels can be carried out with maximum effect and minimum effort using compact, aged artificial habitat collectors on the night time flood tide when low tide coincides with dusk.
Negative effect of ayu on the growth of omnivorous pale chub in experimental pools
Authors: Katano O. , Aonuma Y.
Published: April 2005

The growth rate of pale chub Zacco platypus was negatively correlated with the number and biomass of ayu Plecoglossus altivelis in experiment pools regardless of their body weight. Both species were omnivorous, feeding upon both benthic algae and invertebrates; ayu fed principally upon algae whereas pale chub consumed invertebrates. Pale chub shifted their moving tactics from bottom moving to surface moving or sit‐and‐wait when they coexisted with numerous ayu, presumably due to occasional attack by ayu. It seems likely that the reduced pale chub growth rate was due to interspecific aggression and exploitation of benthic algae and invertebrates by ayu.
Associations between fish assemblages and environmental factors in nearshore habitats of a subtropical estuary
Authors: Kupschus S. , Tremain D.
Published: April 2005

Salinity and inlet distance were the most consistent indicators of species groupings among the 40 most abundant fish species in the Indian River Lagoon (IRL), Florida. In contrast to findings of other studies conducted on small juveniles and forage fishes in the IRL, this study suggested that distributions of the more mobile organisms are influenced more by physical conditions than by biological interactions. Consequently, environmentally‐corrected single‐species models will be more effective in assessing changes in stock abundance and habitat preferences of mobile species in the IRL. Because of the fluctuations in physical conditions in the IRL and other estuaries, it may be inappropriate to use biologically based methods that rely solely on species interactions to assess fish stocks in those systems.
Gastric evacuation of the redspotted catshark under laboratory conditions
Authors: Aedo G. , Arancibia H.
Published: April 2005

An exponential model provided the best description of the gastric evacuation of the redspotted catshark Schroederichthys chilensis and predicted that 98% of a single initial meal was evacuated in 73·9 h at 16·3°C, slower than that reported for other elasmobranchs.
Performance of stationary and portable passive transponder detection systems for monitoring of fish movements
Authors: Barbin Zydlewski G. , Haro A. , Whalen K. G. , McCormick S. D.
Published: April 2005

A stationary system for long‐range detection of PIT tags in fish was efficient under high water conditions in streams. A portable system was particularly effective for detecting habitat use by fish without recapture.
The evolution of electroreception and bioelectrogenesis in teleost fish: a phylogenetic perspective
Authors: Alves‐Gomes J. A.
Published: April 2005

According to current phylogenetic theory, both electroreceptors and electric organs evolved multiple times throughout the evolution of teleosts. Two basic types of electroreceptors have been described: ampullary and tuberous electroreceptors. Ampullary‐type electroreceptors appeared once in the common ancestor of the Siluriformes+Gymnotiformes (within the superorder Ostariophysi), and on two other occasions within the superorder Osteoglossomorpha: in the African Mormyriformes and in the African Notopteriformes. Tuberous receptors are assumed to have evolved three times; all within groups that already possessed ampullary receptors. With the exception of a single catfish species, for which studies are still lacking, all fish with tuberous electroreceptors also have an electric organ. Tuberous electroreceptors are found in the two unrelated electrogenic teleost lineages (orders Gymnotiformes and Mormyriformes) and in one non‐electrogenic South American catfish species (order Siluriformes). Electric organs evolved eight times independently among teleosts: five of them among the ostariophysans (once in the gymnotiform ancestor and in four siluriform lineages), once in the common ancestor of Mormyriformes, and in two uranoscopids. With the exception of two uranoscopid genera, for which no electroreceptive capabilities have been discovered so far, all electric organs evolved as an extension of a pre‐existing electroreceptive (ampullary) condition. It is suggested that plesiomorphic electric organ discharges (EODs) possessed a frequency spectrum that fully transgressed the tuning curve of ampullary receptors, i.e. a signal such as a long lasting monophasic pulse. Complex EOD waveforms appeared as a derived condition among electric fish. EODs are under constant evolutionary pressure to develop an ideal compromise between a function that enhances electrolocation and electrocommunication capabilities, and thereby ensures species identity through sexual and behavioural segregation, and minimizes the risk of predation.
Patterns of gametic investment by female stream‐and ocean‐type chinook salmon
Authors: Healey M. C.
Published: April 2005

Investment in fecundity and egg size is compared among two types of chinook salmonOncorhynchus tshawytscha: stream‐type, which undertake long, arduous oceanic and upstream migrations and often return to their natal rivers (where they do not feed)months before spawning, and ocean‐type, which undertake relatively short oceanic and upstream migrations and remain at sea feeding and accumulating energy until a few days or weeks before spawning. The coefficient of variation in egg size for both life‐history types was significantly less than variation in fecundity, reflecting the expected strong selection on egg size relative to egg number. Total investment in the gonad varied significantly among years in both life‐history types, apparently reflecting variation in oceanic feeding conditions. Stream‐type chinook were smaller in total body size and more than 1 year older than ocean‐type. Stream‐type also invested relatively less of their total body energy in eggs and produced smaller eggs than ocean‐type, reflecting the greater energetic cost of their longer migration and freshwater maintenance. These differences suggest that stream‐type chinook pay a considerable fitness penalty in reproductive output. This may be offset by the fact that stream‐type go to sea at larger size and migrate far offshore, thereby avoiding some of the mortality costs of oceanic migration.
Reproductive apparatus and male accessory structures in two batrachoid species (Teleostei, Batrachoididae)
Authors: Barni A. , Mazzoldi C. , Rasotto M. B.
Published: April 2005

The morphology of the genital apparatus of two batrachoid species, Opsanus tau and Porichthys notatus, was studied. The anatomical organization of the female reproductive apparatus is similar in both species but differences are observed in the rhythm of gametogenesis with individual oocyte production asynchronous in O. tau and group synchronous in P. notatus. The male reproductive apparatus is similarly organized in the two species, with both showing enlongated testes with an efferent duct system, two main testicular ducts, a common sperm duct, and a pair of multi‐channel accessory structures. The sperm transport system consisting of the efferent duct system, main testicular ducts, and sperm duct is more developed in P. notatus and only in this species does it secrete sialoglycoproteins. Male accessory organs also secrete sialoglycoprotein in both species, but they appear more developed in O. tau. Intraspecific variability in development of accessory structures and mucin secretion was also observed between the two male morphs of P. notatus. Type I males, which build nests and perform parental care to eggs and fry, have larger accessory organs and more abundant secretion than type II males, which adopt opportunistic spawning tactics. The possible role played by mucins as components of the seminal fluid, in both species, and their inter‐and intraspecific variability are discussed in the light of the reproductive biology and the presence of alternative male mating tactics.
Gonadal development and non‐functional protogyny in a coral‐reef damselfish, Dascyllus albisella Gill
Authors: Asoh K. , Yoshikawa T. , Kasuya M.
Published: April 2005

All gonads of the Hawaiian dascyllus Dascyllus albisella, irrespective of the final sex of individuals, developed an ovarian lumen and primary‐growth‐stage oocytes after an initially undifferentiated state. From this ovarian state or from more differentiated ovaries, some gonads redifferentiated into testes. None of 117 individuals examined had a gonad containing degenerating vitellogenic oocytes and proliferating spermatogenic tissue. Eleven individuals had gonads containing degenerating cortical‐alveolus‐stage oocytes and developing spermatogenic tissue. The size of these individuals overlapped with the female size range in which the majority of the females were still in the middle of the maturation process. They were absent from the larger size range where the majority of females had vitellogenic oocytes. This indicated that the transition toward maleness is likely to have occurred after the onset of cortical‐alveolus stage, but before final oocyte maturation and spawning as females. Therefore the protogynous pattern of gonadal development was non‐functional. There was no dimorphism in the sperm duct configuration, and all the testes were secondary testes reported for diandric, protogynous species with undelimited gonads. Very early development of an ovarian lumen appeared to have resulted in a secondary‐male configuration in all testes, although redifferentiation into males appeared to have occurred before sexual maturity and spawning as females.
Stomach analyses of Baltic salmon from 1959–1962 and 1994–1997: possible relations between diet and yolk‐sac‐fry mortality (M74)
Authors: Hansson S. , Karlsson L. , Ikonen E. , Christensen O. , Mitans A. , Uzars D. , Petersson E. , Ragnarsson B.
Published: April 2005

In recent years, Baltic Sea salmon Salmo salar have suffered high larval mortality (M74) which can be cured by thiamine treatment. Analyses of long term mortality records (1928–1998) from two salmon hatcheries suggest that before the 1970s M74 did not occur, or was less frequent. This indicates that varying M74 did not cause the long‐term fluctuations of Baltic salmon catches in this period. The frequency of M74 has been correlated positively to the abundance of the salmon's primary prey, sprat Sprattus sprattus. Sprat, herring Clupea harengus and three‐spined stickleback Gasterosteus aculeatus dominated the diet in both the periods of study, 1959–1962 and 1994–1997. The mean size of consumed sprat was significantly smaller in 1994–1997 compared with 1959–1962. Herring and, to a lesser extent, three‐spined stickleback increased in the diet of salmon, while sprat appeared to constitute a smaller part of the diet in 1994–1997. The cause of M74 and the thiamine deficiency involved remains unknown, but is thought to be related to changes in thiamine or thiaminase content in forage fish, winter‐feeding of salmon or general changes in the pelagic food web, caused by overfishing or eutrophication.
Sexual dimorphism in morphometric characteristics of cocktail wrasse
Authors: Park I‐S. , Zhang C. I. , Lee Y‐D.
Published: April 2005

A closely associated set of characteristics was identified in adult cocktail wrasse Pteragogus aurigarius, collected in a coastal area on Cheju Island, Korea in 1993, which showed sexually dimorphic growth. Growth was positively allometric in males. Male cocktail wrasse possess larger first and second spinal rays in the dorsal fin than females resulting in pronounced sexual dimorphism. Such sexual dimorphism may reflect the outcome of sexual selection in this species.
Cardiovascular changes and physiological response during nitrite exposure in rainbow trout
Authors: Aggergaard S. , Jensen F. B.
Published: April 2005

Nitrite‐exposed (1 mM) rainbow trout Oncorhynchus mykiss fell into two distinct groups with regard to susceptibility and physiological response. Group 1 accumulated nitrite in plasma to a concentration of 2·9 mM within 24 h and died before 48 h. Group 2 survived for 96–144 h, and the accumulation of nitrite was slower, levelling off at a concentration c. 2·3 mM at 72 h. Methaemoglobin (metHb) formation was faster in group 1 than in group 2, but both groups had a metHb fraction c. 70% before dying. The extracellular electrolyte balance was perturbed significantly only in group 1, where plasma [Cl‐] decreased and plasma [K+] increased. Heart rate increased rapidly, more in group 1 than in group 2. The tachycardia occurred before any significant changes in metHb or [K+] had developed, suggesting that it was due to nitrite‐induced vasodilation, possibly via nitric oxide generated from nitrite, that was countered by an increased cardiac pumping to re‐establish blood pressure. Arterial blood pressure and pulse pressure were accordingly kept reasonably constant. Heart rate variability was significantly depressed in group 1. The ventilation rate was significantly increased after 9 h of nitrite exposure in group 1, while the ventilation in group 2 did not increase significantly before 21 h. The data reveal that nitrite has substantial influence on the cardio‐respiratory function in fishes.
Comparative performance of juvenile sea trout families in high and low feeding environments
Authors: Glover K. A. , Taggart J. B. , Skalla Ø. , Teale A. J.
Published: April 2005

Groups of eight full‐sibling wild sea trout Salmo trutta L. families, communally reared, exhibited highly significant differences in family representation in the largest 25 percentile within each tank at the end of the observation period (referred to as family performance). Despite these large differences in family performance within tanks, there were no significant differences in performances of families relative to each other between high and low feeding levels. These results are discussed in the context of domestication selection.
Cold adaptation suppresses the contractility of both atrial and ventricular muscle of the crucian carp heart
Authors: Tittu V. , Vornanen M.
Published: April 2005

Adaptation to low temperature in crucian carp Carasius carassius increases twitch duration both in atrial and ventricular muscle and the response is largely explained by a temperatureinduced reduction in myofibrillar ATPase activity. The prolonged twitch increases the refractoriness of both atrial and ventricular muscle, i.e. the optimal force development is achieved at longer diastolic intervals after acclimation to cold. The contractions of atrial and ventricular muscle are insensitive to 10 μ ryanodine, an inhibitor of SR release Ca2+ channel but sensitive to 20 μ verapamil, a blocker of L‐type Ca2+ channels. This suggests that E‐C‐coupling in the crucian carp heart is exclusively based on extracellular Ca2+ sources. The present findings indicate that cold‐acclimation slows the contraction kinetics of the crucian carp heart and thereby preconditions the cardiac muscle for a low energy supply during winter anoxic conditions.
First record of Pomphorhynchus laevis (Acanthocephala) in fishes from Northern Ireland
Authors: Evans D. W. , Matthews M. A. , McClintock C. A.
Published: April 2005

During the spring and summer of 1999, Pomphorhynchus laevis was recovered from rainbow trout Oncorhynchus mykiss raised in a Northern Ireland fish farm and from a European eel Anguilla anguilla from the Erne catchment, Ireland. These records appear to be independent of each other. They are the first reports of P. laevis from fish in Northern Ireland.
REGULAR PAPERS Unusual stable isotope fractionation patterns observed for fish host—parasite trophic relationships
Authors: Pinnegar J. K. , Campbell N. , Polunin N. V. C.
Published: April 2005

Trophic relationships between four taxa of fish parasite (Cestoda, Nematoda, Isopoda, Copepoda) and their hosts (Gasterosteus aculeatus, Merlangius merlangus, Boops boops, Platichthys flesus) were investigated using stable isotopes of carbon and nitrogen. δ15N differences between parasite and host were unlike those conventionally observed among consumers and their diets. In no case were parasites enriched in 15N with respect to the host organism; endoparasites were significantly and consistently depleted. In no case were parasites enriched in 15N with respect to the host organism; endoparasites were significantly and consistently depleted.
Impacts of egg and larval size on survival and growth of Atlantic cod under different feeding conditions
Authors: Zhao Y. , Chen Y. , Brown J. A.
Published: April 2005

Large eggs (1·38 mm) of Atlantic cod reared in the laboratory produced large larvae. However, large larvae had low survival rates. Results also indicated that the first few days' of growth of cod larvae mainly resulted in an increase in mass. Exogenous feeding tended to result in faster growth than endogenous feeding. In the delayed feeding groups (larvae not fed until 67 degree‐days), larvae from large eggs grew faster than those from small eggs (1·28 mm) after feeding commenced, while there was no significant difference in growth rate within feeding groups. Compensatory growth was detected in the delayed feeding groups.
Does the time spent near a male predict female mate choice in a Malawian cichlid?
Authors: Ccouldridge V.C.K. , Alexander G. J.
Published: April 2005

Gravid female Malawian Pseudotropheus cichlids spent significantly more time with males that they subsequently chose as mates, indicating that time spent near a male is a valid and accurate method of measuring female preference. Furthermore, females preferred to mate with males that had longer pelvic fins and a larger number of eggspots on their anal fins. In some instances, females chose to mate with both of the males with which they were presented, possibly because they were unable to discriminate between them.
Fourth specimen of the deep benthopelagic ophidiid fish, Apagesoma delosommatus (Hureau, Staiger & Nielsen, 1979)
Authors: Merrett N. R. , Nielsen J. G.
Published: April 2005

A fourth capture and third extant specimen of the ophidiid, Apagesoma delosommatus, is reported from tropical eastern North Atlantic continental rise waters. Its morphometric and meristic characters are compared with the holotype and paratype and its left sagitta is illustrated.
Oocyte development and maturity classification of swordfish from the north‐western Atlantic
Authors: Arocha F.
Published: April 2005

Swordfish Xiphias gladius are multiple spawners with asynchronous oocyte development, which results in an indeterminate fecundity pattern. The dynamics of oocyte maturation is typified by seven bootstrapped oocyte distributions that represent the maturation process, and aids in the identification of ovaries with hydrated oocytes that have not spawned. Because of the difficulties in obtaining adequate samples for fecundity estimates in swordfish, the classification of the maturation process becomes very useful when methods for identifying ovulated or post‐spawning females, such as histology, are restricted or unavailable.
In vitro cardiac performance in triploid brown trout at two acclimation temperatures
Authors: Mercier C. , Axelsson M. , Imbert N. , Claireaux G. , Lefrançois C. , Altimiras J. , Farrell A. P.
Published: April 2005

The maximum values for heart rate (fH), stroke volume (VH), cardiac output (Q) and myocardial power output, measured in vitro with a perfused heart preparation, as well as the isometric force‐frequency relationship for atrial and ventricular muscle strips, in triploid brown trout Salmo trutta were all comparable with established information for diploid rainbow trout Oncorhynchus mykiss. Therefore, it was concluded that triploidy is not associated with a major deficiency in maximum cardiac performance. However, a heightened sensitivity to ryanodine was discovered, which indicated an enhanced role for the sarcoplasmic reticulum in excitation‐contraction coupling in these triploid fish. It is suspected that the enhanced role of the ryanodine receptor may be a cellular compensation related to larger cardiac myocytes. It was also clearly established that there was a plateau in maximum cardiac performance between 14 and 18° C and this plateau might be a contributing factor to the reduced factorial aerobic scope and increased fish mortality observed at 18° C.
Reconstructing the lengths of juvenile Atlantic salmon from atlas bones: estimating the parr to smolt ratio from regression analyses revisited
Authors: Middlemas S. J. , Armstrong J. D.
Published: April 2005

Analyses of regressions of atlas bone width against fish length (mixed regressions) of Atlantic salmon Salmo salar can be used to infer the parr:smolt ratio of the source populations. Analyses of mixed regressions have been used to infer that, contrary to previous reports, sawbill ducks Mergus spp. eat only a few smolts. Here a Monte Carlo simulation model is presented which quantifies the effect of variation in the smolt:parr ratio on the form of the mixed regression. Based on published mixed regressions, the model predicts 95% CI of 1–36% and 1–42% smolts in diets of sawbill ducks, which are broadly consistent with results of earlier studies. However, other large inconsistencies still exist between results of previous studies and these are briefly discussed.
Male variation in mating success after female numbers are reduced
Authors: Cleveland L. , Itzkowitz M. , Haley M.
Published: April 2005

A significant decline was found in the quantity of eggs that polygynous male beaugregory damselfish Stegastes leucosticus received after reducing the number of available females, which indicated that a significant number of females was removed from the experimental community. The operational sex ratio (OSR) hypothesis, which presumes that a sex becomes increasingly more selective as the number of alternative mates increases, was not supported as the variance in male mating success was unchanged after the females were removed. The relative mating success among males was also unchanged. That is, male ranks remained relatively the same (pre‐test and post‐test) after the removal of females. The large variance in male mating success within this species may be a function of polymorphic mate preferences exhibited by females that may be based on male location.
Individual‐level analysis of early life history traits in hatchery‐reared lake trout
Authors: Pakkasmaa S. , Jones M.
Published: April 2005

In a factorial crossing experiment with individually reared lake trout Salvelinus namaycush eggs. genetic effects explained only a little of the total phenotypic variance in hatching time and alevin size, whereas environmental and maternal effects explained a much larger proportion of variation. Larger eggs produced larger hatchlings, but survival was independent of egg size.
Occurrence of an adult Atlantic salmon in the River Rhône, France
Authors: BagliniÈre J. L. , Tabet Aoul K. , Menella J. Y.
Published: April 2005

A large salmonid was caught in the commercial fisheries in the River Rhône (Mediterranean basin, France). Using morphological criteria and DNA analysis, the fish has been identified as an adult Atlantic Salmon Salmo salar.
The occurrence of Ranzania laevis off the Island of Gran Canaria, the Canary Islands, related to sea warming
Authors: Castro J. J. , Ramos A. G.
Published: April 2005

Catches of the slender sunfish Ranzania laevis were reported off the coastline of the island of Gran Canaria, the Canary Islands, Spain in May‐June 2001, apparently associated with a sudden west‐east warming process of the sea surface in the central Atlantic.
Fluctuating asymmetries and reproductive success in the peacock blenny
Authors: Gonçalves D. M. , Simões P. C. , Chumbinho A. C. , Correia M. J. , Fagundes T. , Oliveira R. F.
Published: April 2005

In an investigation of the relationship between reproductive success and fluctuating asymmetry (FA) in the peacock blenny Salaria pavo, FA was measured in four bilaterally paired characters in successful and unsuccessful males during the breeding season. Reproductive success among successful males was assessed by calculating the number of eggs the males were defending. Absolute FA values relative to trait size were high for all characters and it is suggested that this could be a consequence of sub‐optimal environmental conditions. Two of the traits presented higher absolute FA values suggesting a lower canalization during ontogeny. No difference in FA between successful and unsuccessful males was found and no relationship between FA and number of eggs among the successful males occurred for any of the measured traits. A composite index of FA, that should better reflect overall developmental competence, was also unrelated to reproductive success. These results indicate that FA is not associated with reproductive success among males of S. pavo. Successful males were larger than unsuccessful males and a strong positive correlation was detected between the body length of the parental males and the number of eggs they had in the nest, even when controlling for the internal nest area. Body size may give males a reproductive advantage by being preferred by females and by having an advantage in male‐male competition for nests of higher quality.
Biology of a seahorse species, Hippocampus comes in the central Philippines
Authors: Perante N. C. , Pajaro M. G. , Meeuwig J. J. , Vincent A. C. J.
Published: April 2005

Based on 16 months of field observations on tagged seahorses Hippocampus comes in the Philippines, adults were found to be nocturnal, to maintain small home ranges, and to live mostly among corals. Prolonged pair associations suggested that H. comes, like many other seahorse species, were probably monogamous, a conclusion consistent with their low density and sparse distribution. Site and mate fidelity suggest that H. comes populations may fare poorly under current high levels of exploitation.
Density‐dependent predation and implications for stock enhancement with Japanese flounder
Authors: Kellison G. T. , Eggleston D. B. , Tanaka M.
Published: April 2005

In laboratory predation trials kinsen‐gani crab Matuta lunaris rarely preyed on hatchery‐reared (HR) Japanese flounder Paralichthys olivaceus, even at extremely elevated prey densities (c. 90 fish m−2), but fed readily on sacrificed Japanese founder. This suggests that under similar conditions in the wild predator‐prey interactions between kinsen‐gani and juvenile Japanese flounder are likely to be weak. Larger Japanese flounder readily cannibalized smaller conspecifics, suggesting that within‐release group cannibalism may contribute considerably to post‐release mortality of HR Japanese flounder when sufficient size variation exists within groups of released fish. Kinsen‐gani presence had no effect on within‐release group cannibalism rates of large Japanese flounder on small Japanese flounder. Within‐release group cannibalism rates were significantly affected by densities of smaller (prey) fish, implying that the number of fish released (and thus post‐release densities) in stock enhancement programmes may significantly affect post‐release mortality rates. The probability of within‐release group cannibalism increased rapidly as the cannibal‐to‐prey size ratio exceeded 1.6, suggesting that minimizing size variation of released HR individuals will reduce post‐release cannibalism rates. These results have implications for Japanese flounder stock enhancement release strategies, and may be applicable to other finfish stock enhancement programmes.
Factors affecting migrations of burbot
Authors: Slavík O. , Bartoš L.
Published: April 2005

In autumn, burbot Lota lota migrations through a fish ladder in the regulated Ohře River, Czech Republic, were stimulated by an increase in discharge and a decrease in water temperature but the number of burbot in the ladder was significantly lower when compared with other seasons. The maximum number of burbot in the ladder was recorded in spring when discharge decreased. A sudden decrease in water level caused burbot to leave the refuges in the riverbanks that they had occupied during high winter discharges. The results indicate that the relatively low short‐term variability of physical conditions represented by the modified discharge regime can induce a stronger response in fish migrations even in comparison with typical reproductive migrations of these species.
Isozyme variation among four species of the catfish genus Clarias
Authors: Na‐Nakorn U. , Sodsuk P. , Wongrat P. , Janekitkarn S. , Bartley D. M.
Published: April 2005

Native Thai species of Clarias catfishes and one species introduced from Africa can be easily distinguished by horizontal starch gel electrophoresis of allozymes. An undescribed species of Clarias was collected from Thailand and found to possess several fixed allelic differences from the Clarias previously studied.
Evidence for phylogeographically informative sequence variation in the mitochondrial control region of Atlantic brown trout
Authors: Cortey M. , García‐Marín J‐L.
Published: April 2005

Complete sequencing of the mitochondrial control region was undertaken among brown trout Salmo trutta from North Atlantic areas where previous studies, based on smaller mtDNA fragments, failed to detect any phylogeographic signal. Comparison of sequences suggests that brown trout in the Iberian Peninsula and Scandinavia belong to largely divergent evolutionary units.
The interhepatocytic macrophages and pale‐grey cells in brown trout liver ontogenesis
Authors: Resende A. D. , Rocha E. , Monteiro R. A. F. , Rodrigues P.
Published: April 2005

Pale‐grey cells appeared in the livers of healthy and non‐stressed brown trout Salmo trutta 3 weeks post‐hatching whereas interhepatocytic macrophages appeared at 5 months. Cells with intermediate morphological characteristics between those of pale‐grey cells and macrophages were identified in all ages studies. Cell ultrastructure supported the idea that pale‐grey cells probably belonged to the macrophage lineage, being eventual precursors of the active phagocytes residing amongst hepatocytes.
Skin‐type antifreeze protein expression in integumental cells of larval winter flounder
Authors: Murray H. M. , Hew C. L. , Fletcher G. L.
Published: April 2005

Wholemount in situ hybridization using an antisense riboprobe complementary to a winter flounder Pleuronectes americanus skin‐type antifreeze protein mRNA (WFp9) and immuno histochemistry using polyclonal antibodies to the corresponding protein detected cells expressing this gene in larval winter flounder integument. Immunohistochemistry revealed two distinct populations of cells. One population extended laterally along the length of the fish and was detectable using in situ hybridization. Staining in these cells declined following yolk‐sac absorption suggesting that expression was only important here during early larval development. The polyclonal antibody for skin‐type antifreeze protein also reacted with another population of cells scattered throughout the integument. These cells stained with alcian blue suggesting that they were integumental mucous cells. In situ hybridization using the above probe was not able to detect the corresponding transcript within the same cells. This suggests that another gene may be involved in the production of a similar protein in this case. These data suggest that two distinct populations of cells within the larval integument are involved in skin‐type antifreeze protein expression and possibly involve the activity of at least two different genes.
Structure of the skin of an air‐breathing mudskipper, Periophthalmus magnuspinnatus
Authors: Park J. Y.
Published: April 2005

The epidermis of the mudskipper Periophthalmus magnuspinnatus consisted of three layers: the outermost layer, middle layer and stratum germinativum. Extensive vascular capillary networks were present near the superficial layer of epidermis and outermost layer. The diffusion distance between the vascular capillaries and the surface of epidermis was c. 1.5 ± 0.9μm. The middle layer consisted of small or voluminous cells swollen by epidermal cells. Due to the swollen cells, the thickness of the epidermis increased and the epidermis appeared web‐like. The swollen cells contained tonofilaments, lucent contents and desmosomes. Fine blood capillaries were also discernible in this layer. Well‐developed lymphatic spaces containing lymphocytes existed in the stratum germinativum. Numerous blood capillaries were present under the basement membrane. The dermis consisted of a stratum laxum and stratum compactum, and there was a definite area with acid mucopolysaccharides and a small scale in the stratum laxum. The skin had an epidermal pigment cell, dendritic melanophores (‐cytes) containing melanin granules within their cytoplasm, and two kinds of dermal pigment cells, melanophores and colourless pigments containing reflecting platelets.
Changes in chloride secretion rate and vascular perfusion in the rectal gland of the European lesser‐spotted dogfish in response to environmental and hormonal stimuli
Authors: Anderson W. G. , Good J. P. , Hazon N.
Published: April 2005

Chloride secretion rates of rectal glands taken from the European lesser‐spotted dogfish Scyliorhinus canicula adapting to 70% and 120% sea water (SW) were significantly greater and less than, respectively, those in the control 100% SW group. C‐type natriuretic peptide (CNP) significantly increased chloride secretion rates above basal values in 100% SW although angiotenisn II (ANG II) had no effect. Perfusion of the secretory epithelia in rectal glands from 70% SW lesser‐spotted dogfish was significantly higher than in rectal glands from 100% and 120% SW lesser‐spotted dogfish. Perfusion of rectal glands with ANG II had no effect on perfusion of the secretory epithelia, although CNP perfusion induced significantly greater perfusion of the secretory epithelia than all other treatments. It remains to be determined if a reduction in environmental salinity induces an increase in plasma concentration of CNP and hence an increase in rectal gland activity.
Seasonal aggregations of Canadian east coast pollock as inferred from the commercial fishery and hydroacoustic observations
Authors: Neilson J. D. , Annis L. , Perley P. , Clay A. , Croft C. , O'Connor M.
Published: April 2005

Data from an otter trawler fleet fishing on the Scotian Shelf combined with year‐round hydroacoustic data indicated that the locations of aggregations of pollock Pollachius virens did not change appreciably from month to month. The proportion of pollock mass compared with total catch mass in individual trawl catches, however, tended to be higher from September to February. The period of highest catch rates was shown to be the December to January period. This period coincided with the period when pollock had the least affinity with the seabed based on information from hydroacoustic observations, a behavioural consideration for acoustic survey design. Based on these observations, it was concluded that the optimal time to conduct an acoustic survey was during the December to January period.
Seasonal and interannual variation in fish assemblages of northern temperate rocky subtidal habitats
Authors: Magill S. H. , Sayer M. D. J.
Published: April 2005

Fish assemblages on two inshore rocky subtidal sites on the west coast of Scotland, were studied using diver visual surveys on a monthly basis between September 1995 and December 1999. A total of 17 689 fishes and 26 species were recorded from the two sites, Saulmore Point (056°27′N; 005°24′W) near Oban and Davy's Rock (055°46′N; 004°53′W) on the Isle of Great Cumbrae. The gobiid Thorogobius eppiphiatus, dominated the Saulmore Point site; six fish species accounted for >93% of total abundance at that site. At Davy's Rock four species contributed at least 93% of total fish abundance, and the dominant species was the labrid Ctenolabrus rupestris. Total abundance of the dominant species displayed a clear seasonal trend, and this was significantly related to recorded daily average seawater temperature. A maximum abundance of 4.9 fishes m−2 was recorded in November 1998 at Davy's Rock and 2.5 fishes m−2 at Saulmore Point in October 1998. Multivariate analysis indicated a degree of variation in assemblage structure between winter and summer at both sites. A number of species showed some degree of interannual variation, in particular the gobiid Gobiusculus flavescens whose abundance increased by over 300 times over a 5 month period in 1998. Correlation analysis showed that variation in annual winter seawater temperature could act as an indicator of interannual variation in abundance of some of the dominant species utilizing rocky subtidal habitats.
Olfactory sensitivity of the Mozambique tilapia to conspecific odours
Authors: Frade P. , Hubbard P. C. , Barata E. N. , Canario A. V. M.
Published: April 2005

Electro‐olfactogram (EOG) recordings from female Mozambique tilapia Oreochromis mossambicus gave large responses (up to 45 mV) to water previously occupied by sexually active males. Male body‐fluids also elicited very strong olfactory responses with thresholds of detection of c. 1: 106.9 (bile), 1: 105.2 (urine) and 1: 104.9 (faeces). Considering the likely rates of release of these fluids, it is the urine that provides the strongest olfactory stimulus for females. Crude fractionation of the male water and body‐fluids implicated: (a) sulphated compounds, possibly steroids, as the most potent odorant in the urine (and water previously occupied by males), and (b) bile acids in the faeces and bile. Although the olfactory system of Mozambique tilapia was found to be sensitive to a range of amino acids and bile acids, steroids present in Mozambique tilapia plasma and steroids known to act as pheromones in other species elicited negligible responses. Although the present study clearly suggests that chemical communication might be important in Mozambique tilapia, the exact chemical identity of the compounds involved, and their biological functions, remain to be elucidated.
Seasonal changes in androgen levels in stream‐ and hatchery‐reared Atlantic salmon parr and their relationship to smolting
Authors: Shrimpton J. M. , McCormick S. D.
Published: April 2005

In stream‐reared Atlantic salmon Salmo salar, plasma androgens were significantly greater in mature male parr than immature males and females in October, but had declined by January and did not differ significantly from immature fish throughout the spring. Immature fish in March were significantly larger and had greater gill Na+, K+‐ATPase activity than their previously mature counterparts. Bimodal growth distribution was seen in hatchery‐reared Atlantic salmon and a proportion of the male fish in the lower mode matured. Plasma testosterone (T) and 11‐ketotestosterone (11‐KT) were significantly elevated from September to December in mature male (1+ year) parr. In January, plasma androgens had declined in mature males and did not differ significantly from immature fish. By May all the hatchery fish were large enough to smolt and a proportion of the previously mature males had increased gill Na+, K+‐ATPase activity. Therefore elevated androgens in the previous autumn do not prevent smolting. Parr with higher plasma T and 11‐KT in April and May, that are presumably beginning to mature, had lower gill Na+, K+‐ATPase activity, indicating that future maturation and associated increases in androgens may inhibit smolting.
Genetic tagging to determine passive integrated transponder tag loss in lemon sharks
Authors: Feldheim K. A. , Gruber S. H. , de Marignac J. R. C. , Ashley M. V.
Published: April 2005

Multilocus genotypes using nine DNA microsatellite loci provided an effective and permanent individual identification mark for lemon sharks Negaprion brevirostris, the first example of genetic tagging for any elasmobranch species. The double‐tagging provided by micro‐satellites afforded a means to determine passive integrated transponder (PIT) tag shed rate in lemon sharks. Of 388 sharks that were recaptured, 47 (12.1%) had shed their PIT tag.
Extensive search does not identify genomic sex markers in Tetraodon nigroviridis
Authors: Li Y. , Hill J. A. , Yue G. H. , Chen F. , Orban L.
Published: April 2005

Three methods used for comparing genomic DNA did not detect a sex‐specific genomic marker in the green spotted pufferfish Tetraodon nigroviridis.