bluuebunny/crossref_metadata_2025 huggingface dataset:
Relationship between abundance, growth, egg size and fecundity in a landlocked population of longfin smelt, Spirinchus thaleichthys
Authors: Chigbu P. , Sibley T. H.
Published: April 2005

Sixteen year‐classes of longfin smelt, Spirinchus thaleichthys, show a consistent pattern of alternating year‐class strength between even (strong) and odd (weak) years. A recent (1989) odd year‐class grew as well as, if not better than, the late 1960s odd year‐classes. However, fish in the even year‐classes (1988 and 1990) were significantly smaller in size then the 1966 and 1968 cohorts. Associated with this reduction in growth of the even year‐class fish is a decline in fecundity. Fecundity of the odd year‐classes of smelt was also smaller than in the early 1960s. Mean egg diameter and gonadosomatic index were not statistically different between 1988 and 1989 year‐classes but the relative fecundity was higher for the 1988 year‐class than for 1989, suggesting a higher reproductive investment in the even year‐class. Reduction in growth and associated reproductive traits is considered to result from a reduction in the abundance of mysids, a preferred prey species.
The effect of temperature on intracellular transport of asialo‐glycoproteins in rainbow trout liver
Authors: Løvhøiden N. C. , Gjøen T. , Berg T.
Published: April 2005

The intracellular pathway of a endocytosed glycoprotein has been studied in rainbow trout (Oncorhynchus mykiss) liver by means of differential and isopycnic gradient centrifugation. When 125I‐tyramine‐cellobiose‐labelled asialoorosomucoid was injected intravenously, the protein was removed rapidly from the blood by hepatic endocytosis. The tracer was localized initially in a small, slowly sedimenting organelle (endosome) and transferred to the denser lysosomes where degradation took place. This process took several hours at the acclimated temperature of 10 ° C. The transport could be accelerated markedly or retarded by transfer of fish to higher or lower temperatures respectively. The intracellular transport steps were more susceptible to changing temperature than the internalization process. In particular, the degradation was temperature sensitive. These results may have implications for the effects of changing temperature on immune function in fishes. The impairment of transport upon a rapid temperature decrease, will reduce the rate of antigen processing and presentation in these animals.
Orientation anomalies (reversal) of the four‐spotted megrim (Lepidorhombus boscii) in the Aegean Sea
Authors: Vassilopoulou V.
Published: April 2005

Reversal occurred in four out of 15 325 specimens (0·026%) of four‐spotted megrim Lepido‐rhombus bascii caught in the Aegean Sea.
Age determination of corvina reina (Cynoscion albus) in the Gulf of Nicoya, Costa Rica, based on examination and analysis of hyaline zones, morphology and microstructure of otoliths
Authors: Mug‐Villanueva M. , Gallucci V. F. , Lai Han‐Lin
Published: April 2005

This is the first age determination study for Cynoscion albus, a large tropical sciaenid, using otolith morphology and daily increment analysis. The practicality of both methods for age determination is illustrated by their consistent estimates of age and von Bertalanffy growth parameters. The daily increment analysis was used to validate the surface readings. An alternative, otolith morphometrics, is shown to hold promise for rapid prediction of fish age. Two multivariate linear regression models using gross otolith dimensions can estimate the age of C. albus to within 1 year. Growth parameter estimates are: from surface readings: L=127.5cm with K=0.12; from daily increment readings: L= 122.1 cm with K=0.17. Implications for the stock assessment of tropical fish using size instead of age are discussed.
Parasites of flatfish in relation to sewage sludge dumping
Authors: Siddall R. , Pike A. W. , McVicar A. H.
Published: April 2005

Variations in the occurrence of gastrointestinal metazoan parasites in flatfish were examined in relation to sewage sludge dumping at an ‘accumulating’ and two ‘dispersing’ dump sites in Scottish coastal waters. The gross disturbance of the benthic communities at the Garroch Head disposal site in the Firth of Clyde and absence of the intermediate hosts of particular parasites was not reflected in the parasite fauna of the long rough dab, Hippoglossoides platessoides. Results indicate that this flatfish host is highly mobile and intermixing within the population masked any localized effects of sludge dumping on parasite transmission at the dump site. The common dab, Limanda limanda, is considered to be relatively static at the St Abb's Head and Bell Rock disposal sites off the Firth of Forth where no evidence of effects of sewage sludge dumping on its metazoan parasite fauna was detected. This is consistent with the results of chemical and biological monitoring of the sites. The value of a parasite‐based index of the biological effects of sewage sludge dumping is discussed.
Comparative ecology of the African pike, Hepsetus odoe, and tigerfish, Hydrocynus forskahlii, in the Zambezi River floodplain
Authors: Winemiller Kirk O. , Kelso‐Winemiller Leslie C.
Published: April 2005

The ecology of sympatric African pike, Hepsetus odoe (Hepsetidae), and tiger fish, Hydrocynus forskahlii (Characidae), were compared during high (May‐August) and falling water (September‐December) conditions in the Upper Zambezi R. drainage of Zambia. Both species were common in the central and southern regions of the river and associated floodplain, and Hydrocynus was common in the northern region in swift flowing tributaries where Hepsetus was rare. Hepsetus inhabited vegetated environments of river backwaters, lagoons, and sluggish tributaries, whereas Hydrocynus occupied the open water of the main river channel almost exclusively. During the period of annual flooding, juveniles of both species coexist in flooded savanna regions. Size distributions of adult Hydrocynus and Hepsetus changed relatively little between high and low water conditions. Stomach contents analysis indicated that adult size classes of both species are almost entirely piscivorous, and both show diet shifts with changes in size. Only very small seasonal diet shifts were noted. Approximately 50% of the diet of Hepsetus consisted of haplochromine cichlid fishes, but also included large numbers of tilapine cichlids and mormyrids, Hydrocynus consumed primarily cichlid fishes, but also consumed large percentages of Hepsetus and small characid fishes. Small size classes of Hepsetus fed heavily on small machokid catfishes (Synadontis spp.) and later shifted to a diet of cichlids and mormyrids, and small Hydrocynus preyed heavily on Barbus spp. (Cyprinidae), small characids, and mormyrids. Ratios of prey length‐predator length averaged approximately 0·26 for Hydrocynus and nearly 0·40 for Hepsetus. The large potential for food resource competition appears not to be realized due to a very high degree of habitat partitioning between larger size classes of the two species. At the interface between river backwaters and channel habitats, Hydrocynus is a significant predator of Hepsetus, a factor that should further restrict the occurrence of the latter in open areas of the main channel.
Avoidance responses to low frequency sound in downstream migrating Atlantic salmon smolt, Salmo salar
Authors: Knudsen F. R. , Enger P. S. , Sand O.
Published: April 2005

The possibility of using intense sound as an acoustic barrier for downstream migrating smolt of the Atlantic salmon (Salmo salar) was studied by observing, the reactions of smolt to 10 and 150 Hz sounds in a small river. At the observation site the river branched into a main course and a minor channel, the latter rejoining the main stream after 30 m. The sound sources were positioned at the lower end of the channel. The number of smolt re‐entering the mam stream at the lower end of the channel was recorded during alternating periods with and without sound. Intense 150 Hz sound had no observable effects on the smolt, even at intensities 114 dB above the hearing threshold at this frequency. At intensities above 1.0. 10−2ms−2 the 10 Hz sound was an effective deterrent for the smolt, which turned and left the channel at the upstream branching point.
Changes in ovarian development and plasma levels of sex steroid hormones in the wild female Japanese sardine (Sardinops melanostictus) during the spawning period
Authors: Murayama T. , Shiraishi M. , Aoki I.
Published: April 2005

In order to clarify the spawning pattern of Japaneses sardine (Sardinops melanostictus) during the spawning period, changes in ovarian histology, frequency distributions of oocyte diameter and plasma levels of oestradiol‐17β (E2) and 17a,20β‐dihydroxy‐4‐pregnen‐3‐one (17a,20β‐diOH‐P) were examined in female fish captured in the region off Kyushu and Shikoku in Japan. With the development of the ovary, the gonadosomatic index (GSI) increased gradually and the size of oocytes became larger. When the GSI exceeded 13, the translucent hydrated eggs began to dominate and ovulation subsequently occurred. After ovulation, GSI decreased to less than 3. Post‐ovulatory follicles were found only in the lower GSI ranges and atretic oocytes were always observed in the ovary. Plasma E2 levels increased along with ovarian development but decreased after completion of yolk accumulation. On the other hand, 17a,20β‐diOH‐P showed the highest level just before and after ovulation. Ovarian histology and hormonal profiles suggest that the sardine spawns repeatedly during the spawning period. Based on the concentration of 17a,20β‐diOH‐P, the female Japanese sardine was estimated to ovulate before the middle of the night.
Experimental differences in mortality patterns between European minnows, Phoxinus phoxinus, infected with sympatric or allopatric trematodes,Diplostomum phoxini
Authors: Ballabeni Pierluigi
Published: April 2005

A factorial experiment was conducted to examine if the digenetic trematode parasiteDiplostomum phoxiniinfluences minnow growth and survival negatively and if different parasite populations differ in their effects on hosts. Juvenile full‐sibling minnows from a lake located at the northern edge of the Swiss Alps were infected experimentally withD. phoxinifrom either their own or another lake. When exposed to sympatric parasites, the minnows survived a low and a high infection dose more or less equally, but with allopatric parasites mortality increased with infection dose. Parasites did not reduce host growth and minnows exposed to a low infection dose grew quicker than either non‐infected ones or ones exposed to a high infection dose. Thus, the results show different patterns of pathogenicity between two parasite populations and suggest that (1) the observed differences are at least partially genetic and that (2) the co‐evolved, sympatric host‐parasite association has reached a degree of low pathogenicity. Differences between the findings presented here and those of a previously published study are discussed.
Nest site choice by the three‐spined stickleback, Gasterosteus aculeatus (form leiurus), in spring‐fed waters
Authors: Mori Seiichi
Published: April 2005

The nest site characteristics of the freshwater three‐spined stickleback, Gasterosteus aculeatus (form leiurus), were quantitatively investigated in springs and the main stream of the Yamayoke and the Tsuya River system, central Japan. Most nests (93·4%) were on a muddy or sandy substratum, at depths of 10–40 cm (84·3%), in water velocities less than 15 cm s−1 (76·2%) and in the temperature range of 14 to 16° C (82·7%), Spring‐fed localities provided more of these conditions than the main stream channel and hence contained more potential nesting areas. Thus, they were utilized by male sticklebacks both temporally (prolonged breeding season) and spatially (more nest sites).
Energetics and metabolic correlates of starvation in juvenile perch (Perca fluviatilis)
Authors: Mehner T. , Wieser W.
Published: April 2005

Long‐term measurements of the diurnal pattern of oxygen consumption were conducted in fasting juvenile perch at 15 and at 20° C. In addition, dry body mass, protein and glycogen concentrations and the activity of two key enzymes of energy metabolism, phosphofructokinase and glutamate pyruvate transaminase, were monitored during the period of food deprivation. The average rate of oxygen consumption decreased during the starvation period, but the regular diurnal pattern of low rates in the dark and high rates in the light was upset by a break around days 7 to 8 at both temperatures. This break coincided with the exhaustion of the glycogen reserves in the muscles and in the liver, indicating that switching to a new energetic fuel was accompanied by a change in the pattern of swimming activity. Choice of the major energy source after exhaustion of the carbohydrate store was substantially influenced by water temperature. A negative correlation was found between the scope for spontaneous activity and the specific rate of oxygen consumption in the dark phase suggesting that the resting rate of metabolism responded more strongly to food deprivation than the rate of spontaneous activity in the light phase.
Effects of salinity fluctuation on routine metabolism of juvenile spot, Leiostomus xanthums
Authors: Moser M. L. , Miller J. M.
Published: April 2005

We subjected juvenile spot, Leiostomus xanthurus, to eight different salinity fluctuation schedules to evaluate the effects of magnitude, rate, mean, and direction of salinity changes on their routine metabolism. Routine respiration stabilized within 3 h after all salinity changes and no fish died. Very rapid rates of change and changes at low mean salinity elicited short‐term stress responses in 40–70 mm spot. Spot adapted more rapidly to increasing salinity changes than to decreasing changes, but the acclimation state of the fish apparently did not affect their salinity tolerance. Our results also indicated that spot undergo size‐dependent changes in sensitivity to salinity fluctuation which correspond to seasonal shifts in distribution.
Does specific dynamic action (SDA) regulate return of appetite in the lesser spotted dogfish, Scyliorhinus caniculcla?
Authors: Sims D. W. , Davies S. J.
Published: April 2005

Specific dynamic action (SDA) and the return of appetite (RA) were measured in juvenile (weight range 10·9–16·3 g) and adult (weight range 588·8–802·2 g) Scyliorhinus canicula by means of respirometry and re‐feeding trials respectively. Juvenile S. canicula consumed relatively more food than the adults at all times indicating faster rates of food processing in juvenile dogfish. At no time during the SDA effect was there any evidence that elevated levels of oxygen consumption completely prevented further food consumption in either adult or juvenile dogfish. The coefficient (DurationSDA/DurationRA) was similar for both adult (0·52) and juvenile (0·49) S. canicula suggesting that SDA metabolism was closely associated with the processes involved in appetite return.
The distribution of Cryptocotyle spp. metacercariae in the skin of caged Atlantic cod (Gadus morhua)
Authors: Lysne D. A. , Hemmingsen W. , Skorping A.
Published: April 2005

In caged Atlantic cod (>40cm), Cryptocotyle spp. metacereariae were concentrated on the dorsal surface, but relatively scarce on the fins. Behaviour and mechanical forces probably affect this distribution.
Population regulation of vendace (Coregonus albula) in Lake Pyhäjärvi, southwest Finland
Authors: Helminen Harri , Sarvala Jouko
Published: April 2005

Previous time series analysis on vendace population dynamics in Lake Pyhäjärvi, 1971–1990, revealed a 2‐year cycle in year‐class strength, implying powerful density‐dependent regulation. Here we have extended this analysis by using multiple regression models to test whether the recruitment series is influenced by density‐independent factors. We chose population size with a lag of 1 year as the density‐dependent factor; the density‐independent factors were the summer water temperature with a lag of 2 years (temperature sum for June, July and August, indicating the year‐class strength of predators) and the temperature‐derived length of the larval period of vendace. For the years 1972–1990 the coefficient of determination (r2) of this regression model was 0·77. We suggest that the basic mechanism producing a persistent 2‐year cycle of vendace in Lake Pyhäjärvi is the asymmetrical food competition between age groups. The abundance of predators in the lake and the warming of the water after the hatching of larvae in spring together determine the final year‐class strength of vendace.
Schooling preferences for familiar fish in the guppy, Poecilia reticulata
Authors: Magurran A. E. , Seghers B. H. , Shaw P. W. , Carvalho G. R.
Published: April 2005

Although schooling behaviour is an important antipredator response of guppies (Poecilia reticulata) in Trinidad it is not known whether fish elect to school with particular individuals. Familiarity is a simple mechanism that could lead to non‐random associations within schools. In this paper we test the idea that prior experience of particular individuals influences the choice of partners during schooling. We show (in a laboratory study) that female guppies prefer to associate with familiar individuals. However, we are unable to detect any schooling preference for unfamiliar females from the same population.
A behavioural study of hybridization between Barbus barbus and Barbus meridionalis
Authors: Poncin P. , Jeandarme J. , Berrebi P.
Published: April 2005

The reproductive behaviour of two species of barbel (Barbus barbus and Barbus meridionalis) was investigated by means of aquarium experiments in several matings of six combinations. The reproductive behaviour of the two species appears to be similar and hybridizations were observed, showing that no complete behavioural barrier blocks the mating of the two species.
Distribution patterns of palatal taste buds and their responses to amino acids in salmonids
Authors: Hara Toshiaki J. , Kitada Yasuyuki , Evans Robert E.
Published: April 2005

The distribution pattern of the palatal taste buds and their electrical response characteristics to amino acids were studied in five salmonid species: Arctic grayling (Thymallus arcticus), lake whitefish (Coregonus clupeaformis), Atlantic salmon (Salmo salar), brown trout (Salmo trutta), and kokanee (Oncorhynchus nerka). In these fish the most dense taste bud populations were found on ridges in tine area around the palatine teeth. With the exception of lake whitefish, the ridges adjacent to the teeth on the head and shaft of the prevomer were also dense in taste buds, which appear to be largely responsible for amino acid detection. All species, except for lake whitefish, responded well to l‐proline (l‐Pro) and l‐α‐amino‐β‐guanidinopropionic acid (l‐AGPA), with thresholds at 10−8‐10−7 and 10−5‐10−4 M, respectively. These species also responded to varying degrees to hydroxy‐l‐proline (l‐Hpr) and l‐alanine (l‐Ala), believed to be agonists for l‐Pro receptors. In addition, kokanee detected l‐phenylalanine, l‐leucine and betaine. Of six lake whitefish examined, only one specimen responded to l‐Pro, l‐AGPA and l‐arginine. We concluded that in these five salmonid species l‐Pro and l‐AGPA receptors play a major role in amino acid gustation, and further proposed a hypothesis that salmonids may have initially evolved these two gustatory receptors. With phylogenetic advancement, they gained greater response capabilities by (1) acquiring new receptor types, and (2) by losing the specificity of existing receptors.
Scanning electron microscopic analysis of annulus microstructure in otolith of European eel, Anguilla anguilla
Authors: Tzeng W. N. , Wu H. F. , Wlckström H.
Published: April 2005

To validate the yearly periodicity of annulus formation in the otolith of the eel, the structure of annuli in otoliths of the European eel, Anguilla anguilla, stocked for 7 and 12 years in Lake Ommen on the east coast of southern Sweden, was examined. The population was stocked from elvers imported both from France (Bay of Biscay) in April 1979 and England (River Severn) in March–April 1984. The microstructure of an annulus consisted of single, double and/or composite tings depending on the location in the otolith. The counts of annuli in otoliths of these eels were approximately consistent with the expected age. However, supernumerary false annuli and/or annulus underestimation frequently occurred. The methodology for annulus discrimination with light and scanning electron microscopes is described.
Abnormal dorsal light response in teleost fish after intraocular injection of 6‐hydroxydopamine
Authors: McCormack C. A. , McDonnell M. T.
Published: April 2005

Following unilateral intraocular injection with 6‐hydroxydopamine to the right eye, Midas cichlids displayed an acute abnormal dorsal light response, in favour of the right eye. This condition was reversed immediately by dopamine or dopamine receptor agonists delivered by intraocular injection but this recovery was not sustained, Retinal dopamine production reappeared gradually from day 30 post‐6‐hydroxydopamine treatment, and coincided with the fish beginning to adopt a normal dorsal light reaction. Dopamine production recovered completely at day 45 post‐6‐hydroxydopamine injection and coincided with complete recovery of the normal dorsal light reaction. These observations suggest a role for intraocular dopamine in maintenance of the visual part of the normal dorsal light reaction.
Susceptibility of Atlantic herring and plaice larvae to predation by juvenile cod and herring at two constant temperatures
Authors: Fuiman L. A. , Batty R. S.
Published: April 2005

Predation encounters were staged in the laboratory to compare prey responsiveness, predator error rate, and predator capture success for juvenile cod Gadus morhua (a suction feeder) and herring Clupea harengus (a biting predator) preying on herring and plaice Pleuronectes platessa larvae. Trials were conducted at near natural temperature extremes for the larvae (8 and 13°C) to assess the importance of water temperature to the interaction. Herring larvae were significantly more responsive to attacks by herring than were plaice larvae (5·7 vs 0′0%). The two prey species were equally responsive to attacks by cod (2–6 vs 10%). Cod caught 91% of herring larvae attacked and juvenile herring caught 87%. Cod were successful in 96% of attacks on plaice, but juvenile herring caught significantly fewer (83%) plaice larvae. For each predator species, capture success did not vary significantly with prey species. Overall capture success for herring was significantly lower than that for cod. Responsiveness of herring larvae to attacks by juvenile herring increased with temperature, but predator error rate and capture success were not altered by water temperature.
Comparative internal morphology of deep‐sea eels, with particular emphasis on gonads and gut structure
Authors: Flshelson L.
Published: April 2005

Anatomic and cytological studies of some 110 species of deep‐sea eels of among others the families Congridae, Colocongridae, Heterenchelyidae, Synaphobranchidae, Nettastomatidae, Nemichthyidae, Serrivomeridae, revealed a very high diversity in the visceral organs, especially gonads, guts and kidneys and their relation to the anal opening.

The ovaries of various species were either monocyclic, producing eggs periodically, or polycyclic with frequent egg production. Some testes showed synchronous and others asynchronous sperm production. In some of the families, such as Heterenchelyidae, all the gonads are situated post‐anally, in the tail, whereas in Congridae the extent of penetration varies in the different genera, indicating that this family is an artificial one. As some gonads of a few species were found to harbour gametes of the two sexes, the possible occurrence of hermaphroditism is discussed. Melanization of gut was observed in numerous species produced by the penetration of pigmented tissue between the muscle layers of the gut wall or between these and the gut epithelium, this differing between various taxa and in young and adult specimens. The melanization of gut or parts of gut prevent slight (emitted by the swallowed bioluminescent prey) from being seen outside, and in this way protects the eel from predation. Pigmentation also occurs in the kidneys and other explanations for melanization are therefore discussed. In numerous species the gut, kidney and gas chamber partially penetrate into the tail, and as with the gonads, these characters can also be used on eel taxonomy.
A simplified sampling procedure for field estimation of food consumption of Arctic charr Salvelinus alpinus using gillnets
Authors: Amundsen P.‐A.
Published: April 2005

A study carried out with Arctic charr demonstrated that gastric evacuation terminates when fish are caught in gillnets. This allows the sampling procedure for field estimation of food consumption to be simplified.
Parasites of freshwater resident and anadromous Arctic charr (Salvelinus alpinus) in Greenland
Authors: Due T. T. , Curtis M. A.
Published: April 2005

Twenty‐one metazoan parasite species were found in Arctic charr at three coastal sites in west Greenland, includingNeascussp. and the nematodePseudoterranova decipiens, new records for Arctic charr. Twelve species are new records for Arctic charr in Greenland. The quantitative composition of the parasite communities varied, but the freshwater species (Diphyllobothrium ditremwn, Eubothriutn salvelini, Proteocephalus longicollis, Crepidostotnutn farianis) were usually numerically dominant, even in anadromous fish. The absence from Greenland of Mysidacea, Amphipoda, Ephemeroptera and Odonata excludes parasites requiring such organisms as intermediate hosts, including the cestodeCyathocephalus truncatus, nematodes of the genusCystidicola, and freshwater acanthocephalans.
Estimating the success of natural spawning of salmonids in streams
Authors: Rubin J.‐F.
Published: April 2005

A new method is described to estimate the survival of salmonids in streams from fertilization of the eggs to the emergence of the fry. The method is compared to other techniques generally used to estimate the egg‐to‐fry survival: fry traps, excavation of redds, construction of artificial redds and laboratory experiments. Especially designed boxes filled with substratum and freshly fertilized eggs are buried in the stream bed. Survival is determined at three different embryological development stages: eyed stage, hatching and emergence. Boxes are planted inside the stream bed using a special injector, so that substratum alterations are minimal around the boxes. This method was tested successfully in two different studies, one in Switzerland on the brown trout, the other one in Sweden on the sea trout.
A hierarchical response to differences in ration size in the reproductive performance of female three‐spined sticklebacks
Authors: Fletcher D. A. , Wootton R. J.
Published: April 2005

The response of female three‐spined sticklebacks (Gasterosteus aculeatus) to differences in food ration during the breeding season was quantified for several variables related to reproductive performance. The measured protein and lipid contents (mg g−1) of eggs were unaffected by ration. Egg size increased with an increase in both ration and female size, but the proportional increase in egg size was much smaller than the proportional increase in ration. The best predictor of mean batch (clutch) fecundity and weight was female size. There was a small but significant increase in batch fecundity with ration, but the increase was not directly proportional to the increase in ration. The rate of spawning, total breeding season fecundity and total weight of eggs spawned over the breeding season were sensitive to ration with breeding season fecundity and weight increasing in direct proportion to ration. Thus, in female sticklebacks, there is a hierarchy of sensitivity to ration in the response of variables related to reproduction.
Genetic variation of vertebral fusion patterns in coho salmon
Authors: Campbell W. B.
Published: April 2005

The distribution of vertebral fusions along the spinal column differed significantly among crosses from two hatchery stocks of coho salmon, indicating a genetic basis for this character.
Free—living fathead minnows rapidly learn to recognize pike as predators
Authors: Chivers D. P. , Smith R. J. F.
Published: April 2005

Individuals from a natural population of approximately 20 000 fathead minnows from a pike–free pond did not respond with appropriate anti–predator behaviour upon encountering pike odour in laboratory tests. However, 14 days after 10 pike were stocked into the pond, minnows had acquired recognition of pike odour. Laboratory studies have indicated several possible mechanisms for acquiring predator recognition in fathead minnows. This study indicates that these, or similar processes, can produce major changes in predator recognition in the wild.
Sexual development and sexuality in the Nassau grouper
Authors: Sadovy Y. , Colin P. L.
Published: April 2005

Hermaphroditic sexual patterns are widespread among teleosts and are especially characteristic of certain perciform families. Among the most diverse groups of hermaphroditic species are the groupers, hamlets and sea basses of the family Serranidae. Like other groupers, the epinepheline serranid, Epinephelus striatus, the Nassau grouper, has long been assumed to exhibit monandric protogyny (a form of hermaphroditism in which all males derive from adult females by sex change). Histological and demographic data, however, indicate that the sexual pattern of this species is not monandric, and that, unlike other group species, the juveniles pass through a bisexual stage of gonadal development. Sexuality in the Nassau grouper is essentially gonochoristic, with potential for sex change. The combination of bisexuality and gonochorism is previously undescribed in the serranids.
Gastric evacuation in little skate
Authors: Nelson G. A. , Ross M. R.
Published: April 2005

The effects of prey type and prey preparation on the mathematical forms and rates describing gastric evacuation in little skate Raja erinacea were examined. Linear and square–root models best described the gastric evacuation of whole, thin–shelled krill Meganyctiphanes norvegica, clam feet/muscle Spisula solidissima/Placopecten magellanicus, polychaetes Glycera spp. and sand lance Ammodytes dubius. Evacuation of krill and clams was faster than polychaetes and sand lance. A logistic model best described the evacuation data of thick–shelled benthic shrimp Crangon septemspinosa/Palaemonetes spp. Cut polychaetes Nereis spp. were digested at an exponential rate and were evacuated faster than would be predicted based upon comparison with live polychaetes and previously published evacuation–temperature relationships. The results of this study suggest that a single equation does not describe the evacuation process for all prey, and that whole prey should be used if laboratory–derived rates of gastric evacuation are to reflect what might occur in wild fishes.
Retention of visible implant tags by juvenile brown trout
Authors: Niva T.
Published: April 2005

The retention and readability of visible implant (VI) tags were evaluated in juvenile brown trout. The tags were implanted in the adipose eyelid tissue posterior to the left eye, in a total of 6697 fish in 18 groups. During the first year, tag retention increased with tagging experience, from 58 to 64% in 3–summer–old fish and from 86 to 96% in 4–summer–old fish. The effect of fish size at tagging on tag loss was clear in the 3–summer–old groups in 1991 (ANOVA, P= 0.00001). Tag retention in 3–year–old and 4–summer–old fish in 1992 and 1993 varied from 96 to 99% and the handling of the fish after tagging affected retention significantly (t–test, P= 0.0002), the average being 98.7% for those transposed by submerging and 96.5% in those transposed by dropping. After inspection the fish were released into a natural environment. On recapture after 6 months or more the red tags (faded almost to white) and yellow tags (originally close to white) were difficult to distinguish. No infection or tissue damage was found after either inspection or stocking.
Growth and differentiation of epidermal cells from the rainbow trout established as explants and maintained in various media
Authors: Mothersill C. , Lyng F. , Lyons M. , Cottell D.
Published: April 2005

Growth and a number of differentiated characteristics of cultured epidermal cells from the rainbow trout Oncorhynchus mykiss were compared using two commercially available serum–free media, a dermal substrate/serum free kit and a serum–containing medium which had been previously optimized for epidermal cell culture. Each medium supported short term growth over 15 days. Only the medium supplied for dermal substrate culture supported longer growth periods. This medium was supplied for use with a collagen/stromal substrate but gave good cultures even without the substrate. Differentiation, measured by examining mucous cells, cytokeratins, epidermal growth factor receptor, gap junction status and ultrastructure showed that serum–free media gave quantitatively and qualitatively superior expression and short term retention of differentiation over serum–containing medium. Epithelial cell growth with expression of differentiated characteristics can be maintained in primary culture in serum–free medium for at least as long as in serum–containing medium. This provides a useful technique for use when serum presence in medium is undesirable or proves toxic to the specialized cell type under investigation.
Sexual dimorphism and allometry of external morphology in Oreochromis mossambicus
Authors: Oliveira R. F. , Almada V. C.
Published: April 2005

Sexual dimorphism in growth of conventional morphometric characters was investigated in juveniles and young adults (size range: 31 to 91 mm) of Oreochromis mossambicus. A closely associated set of traits was identified that shows sexually dimorphic growth, which was positively allometric in the males. These traits correspond to two different morphological complexes: jaw structure and anal/dorsal fins. The best sex discriminators among this set of traits were premaxilla width, anal fin height and snout length. These findings may be explained in terms of intra– and inter–sexual selection acting together and favouring males with strong and large mouths and high dorsal and anal fins, traits that are important in agonistic displays (jaw and fins), fighting and nest digging (jaw).
The gill filament muscles in two loricariid fish (genus Hypostomus and Rhinelepis)
Authors: Fernandes M. N. , Perna S. A. , Santos C. T. C. , Severi W.
Published: April 2005

The adductor muscles in the gills of loricariid fish of genus Hypostomus and Rhinelepis are restricted to the distal end of the interbranchial septum. These muscles in Hypostomus comprise longitudinal and oblique striated muscle fibres.
Effects of daily management stress on haematology and blood rheology of the gilthead seabream
Authors: PagÉes T. , Gómez E. , Súñer O. , Viscor G. , Tort L.
Published: April 2005

Haematological and haemorheological responses against a moderate management stress, applied for 2 weeks, have been studied in the gilthead seabream (Sparus aurata). The stress application leads to a significant reduction in circulating erythrocytes, which caused decreased blood viscosity. Although erythrocyte osmotic fragility showed a trend inversely related to the duration of management stress, no significant change in cell dimensions, aggregation and deformation indices was observed. Consequently, the decrease in oxygen transport capacity attributable to haematocrit reduction, is not compensated by a qualitative change in the microrheological behaviour of erythrocytes, since the blood viscosity decreases as a direct result of the decline in red blood cell number.
Cryopreservation of the milt of the northern pike
Authors: Babiak I. , Glogowski J. , Luczynski M. J. , Kucharczyk D. , Luczynski M.
Published: April 2005

Seven published extenders, three thawing media and two thawing temperatures were tested in order to determine their suitability for cryopreservation of northern pike (Esox lucius L.) sperm. Sperm motility during successive steps of cryopreservation was evaluated. Erdahl and Graham's extender with the addition of egg yolk proved to be the most efficient (maximum hatching rate of 74.5%) when semen was thawed in 120 mm NaCl solution warmed up to 30° C. No correlations between motility of sperm (diluted in extenders or diluted in extenders and then activated with thawing solution) and the subsequent hatching success were observed. The relationship between motility of thawed sperm and its fertilization ability was considerable, but correlation was not significant. Spermatozoa frozen in some extenders were frequently motile after thawing but they were not able to fertilize the eggs, this resulted in a poor hatching rate. Depending on the extender, the addition of yolk induced either positive or detrimental effects on fertilization success.
Scaling of oxygen consumption of Lake Magadi tilapia, a fish living at 37°C
Authors: Franklin C. E. , Johnston I. A. , Crockford T. , Kamunde C.
Published: April 2005

Rates of oxygen consumption were measured in the geothermal, hot spring fish, Oreochromis alcalicus grahami by stopped flow respirometry. At 37° C, routine oxygen consumption followed the allometric relationship: V o2=0.738 M0.75, where V o2 is ml O2 h −1 and M is body mass (g). This represents a routine metabolic rate for a 10 g fish at 37° C of 0.415 ml O2 g−1 h −1 (16.4 μmol O2 g −1 h −1). Acutely increasing the temperature from 37 to 42° C significantly elevated the rate of O2 consumption from 0.739 to 0.970 ml O2 g −1 h −1 (Q10=l.72). In the field, O. a. grahami was observed to be ‘gulping’ air from the surface of the water especially in hot springs that exceeded 40° C. O. a. grahami may utilize aerial respiration when O2 requirements are high.
Adaptation of the tetrazolium reduction test for the measurement of the electron transport system (ETS) activity during embryonic development of medaka
Authors: G.‐Toth Laszlo , Szabo Marianne , Webb Dennis J.
Published: April 2005

The quantitative electron transport system (ETS)‐assay based on tetrazolium reduction has been adapted for determining the terminal ETS activity during embryonic development of the subtropical teleost fish Oryzias latipes, medaka. Homogenization with a glass potter for 1–2 min was required for the complete extraction of the ETS. Additional sonication and centrifugation had a degradatory effect on the ETS activity. The main substrate of the ETS of fish embryos was NADH. NADPH also donated electrons for the ETS but with much less intensity. The impacts of the NADH and the NADPH on the enzyme activity was not additive. Succinate was ineffective as a substrate for the ETS. NADH (1.7 mM) and NADPH (0.25 mM) in combination with 0.8 mM of the artificial electron acceptor, 2‐(p‐iodophenyl)‐3‐(p‐nitrophenyl)‐5‐phenyl tetrazolium chloride (INT), ensured a Vmax for the ETS if the reaction mixture contained 400 μg wet weight egg ml−1 of cell‐free homogenate. The pH‐optimum of the ETS was between pH 8.0 and 8.6. The enzyme reaction at 24°C was linear during 40 min incubation. The ETS activity increased exponentially during embryonic development. The assay could be a useful tool for detecting the effect of pollutants on the development of the respiratory enzyme system in fish during embryogenesis.
Gill carbohydrate metabolism of rainbow trout is modified during gradual adaptation to sea water
Authors: Soengas J. L. , Barciela P. , Aldegunde M. , Andrés D.
Published: April 2005

The levels of glycogen and glucose, and the activities of several key enzymes of glycogenolysis, glycolysis and the pentose phosphate shunt were assessed in gills of rainbow trout of two sizes (97.03 ± 3.03 g and 165.69 ± 5.01 g) during gradual transfer to sea water (0, 9, 18 and 28 ppt). The results indicated changes, mainly size‐independent, in carbohydrate metabolism of gills during gradual adaptation to sea water. Glucose availability in gills increased as a result of both higher glycogenolysis and greater supply of exogeneous glucose. This glucose was mainly used for increased glycolysis, providing the ATP needed to perform the hypo‐osmoregulatory work occurring in gills during adaptation to sea water.
Effects of prey density and short term food deprivation on the growth and survival of American shad larvae
Authors: Johnson J. H. , Dropkin D. S.
Published: April 2005

Growth and survival of 16‐and 18‐day‐old American larvae (Alosa sapidissima) increased with prey density (0, 500, and 1000 Artemia l−1), though differences were not always significant. Significant differences were not observed in growth parameters and survival for larvae fed 500 v. 1000 Artemia 1−1 in laboratory experiments. Food deprivation for as little as 2 days had significant effects on survival but growth effects were not detectable until 4 days of starvation. These findings have application to the Susquehanna River where c. 11 million 2.5‐week‐old shad larvae are released annually as part of a basin wide effort to restore the species. Larvae released at upriver sites where food may be limiting would drift for 2–3 days to reach reservoirs with higher prey densities. Based on these laboratory findings, survival of shad may be reduced significantly if larvae do not feed prior to reaching reservoir environments.
Genetics of whitefish and vendace in England and Wales
Authors: Beaumont A. R. , Bray J. , Murphy J. M. , Winfield I. J.
Published: April 2005

Proportion of loci polymorphic (P) and mean heterozygosity per locus (Hexp) were P= 0.130 and Hexp= 0.096 for C. albula from the English Lake District and P= 0.217 and Hexp= 0.046 for C. lavaretus from the English Lake District and Llyn Tegid, Wales in 1991–2. Significant deviation from the Hardy‐Weinberg model was observed at the superoxide dismutase (sSOD*) locus in C. albula from Bassenthwaite Lake. This could have been due to chance, to the Wahlund effect or to selection. Genetic distances between the two species were consistent with their taxonomy and genetic differentiation was much greater for the C. lavaretus populations than for the two geographically close C. albula stocks. Llyn Tegid C. lavaretus showed unique alleles at two loci and conservation of fish in this lake is therefore of great importance. Red Tarn C. lavaretus differed most from other Lake District populations probably due to founder effects from early stocking events and/or from selection due to the high altitude of this lake.
Observations on egg‐laying in the thornback ray
Authors: Ellis J. R. , Shackley S. E.
Published: April 2005

The egg‐laying sequence of Raja clavata from aquarium observations, has been found to consist of a 2‐day cycle and to last less than 7 weeks. The mean body length, disc width, and weight of the newly‐hatched rays were 118, 75 mm and 8.92 g respectively and the sex ratio was 1: 1.
Record of a larval Parataeniophorus brevis from Hawaii
Authors: Herrera G. A. , Lavenberg R. J.
Published: April 2005

A 7.2 mm notochordal‐length larva of Parataeniophorus brevis is described and illustrated from the fifth and the smallest specimen, collected near Hawaii. This larva is compared to all other described species of the family Mirapinnatidae, and is unique in having the unpaired fin rays developing in the finfold. The three species of Parataeniophorus can be distinguished on the basis of the number of dorsal‐fin and anal‐fin rays: bertelseni, 18–20 and 16–18; brevis, 13–16 and 13–15; gulosus 28–33 and 23–29, respectively.
Testicular development and serum sex steroid profiles during the annual sexual cycle of the male sturgeon hybrid the bester
Authors: Amiri B. Mojazi , Maebayashi M. , Adachi S. , Yamauchi K.
Published: April 2005

Testicular development in the adult male F1 sturgeon hybrid, the bester (Huso huso L. female x Acipenser ruthenus L. male), was examined monthly in relation to serum sex steroid levels. Spermatogenesis lasted for 1 year, with meiosis generally starting in September and spermiogenesis in November, although there was considerable variation in testicular developmental stages between fish sampled monthly. Testicular development continued, slowly, during the winter months until April. Fish did not exhibit spontaneous spermiation, and phagocytotic activity of Sertoli cells became prominent from May onwards. Androgen levels increased during Spermatogenesis and remained high throughout the pre‐spermiation period. In the degeneration stage, 11‐ketotestosterone concentrations declined to low levels, while testoster‐ one levels remained high. The serum concentration of 17,20β‐dihydroxy‐4‐pregnen‐3‐one was low throughout the reproductive cycle. Based on these results, it is suggested that the time appropriate for induction of final maturation would be from November–December to April when the testes are in the late stage of development.
Variation at enzyme coding loci and correlates of fitness in rainbow trout: a cohort analysis
Authors: Ferguson M. M.
Published: April 2005

An association between heterozygosity at six to nine enzyme coding loci and correlates of fitness (survival, age at first maturation) was tested in two cohorts of rainbow trout Oncorhynchus mykiss reared in the laboratory. A subsample offish from the first cohort was reared together for 3 years. There, fish sampled as embryos, juveniles and adults did not differ significantly in multilocus heterozygosity (MLH, numbers of heterozygous loci per fish). However, fish that died during a period of high natural mortality had significantly greater MLH than those sampled before as hatched embryos and later as adults. The number of homozygotes and heterozygotes at three loci differed significantly among different aged fish but in different directions. Allele counts at two of these loci also differed among samples. In a second cohort, the heterozygosity of fish that died during the period of high natural mortality was compared with that of healthy fish collected at the same time; no significant differences in MLH or allele frequencies were detected. Taken together, the lower MLH of the natural mortalities as well as single locus effects observed in the first cohort might be explained by the differential survival of fish with particular genotypes leading to changes in heterozygosity of the entire cohort over time rather than heterozygosity per se. Age of first maturation and heterozygosity (MLH and single locus) were not associated in males but were marginally so in females. Time of ovulation within the spawning season was not associated with the MLH of females.
RNA‐DNA ratios in white muscle tissue biopsies reflect recent growth rates of adult brown trout
Authors: Grant G. C.
Published: April 2005

Recently developed fluorescence techniques were used to quantify RNA‐DNA ratios in white epaxial muscle tissue biopsies taken from live adult brown trout. RNA‐DNA ratios from small biopsies (4–24 mg wet weight) were measured concurrently with growth over 5 weeks in two groups of brown trout fed different rations, 5% BW day– 1 (reference) and 1% BW week– 1(treatment). Reduced rations had significant effects on RNA‐DNA ratios in muscle tissue biopsies. The treatment group had significantly lower mean RNA–DNA ratios than the reference group after the first week. After 5 weeks of treatment the mean RNA–DNA ratios of the treatment and reference groups were 1–98 and 4–31, respectively. RNA‐DNA ratios from muscle tissue biopsies reflected recent growth rates in the two groups of fish. This technique allows a biochemical measurement of growth rates in adult fish without mortality.