bluuebunny/crossref_metadata_2025 huggingface dataset:
A karyotype analysis of the genus Dicentrarchus by different staining techniques
Authors: Sola L. , Bressanello S. , Rossi A. R. , Iaselli V. , Crosetti D. , Cataudella S.
Published: April 2005

This study presents a cytogenetic analysis of the genus Dicentrarchus, represented by two species, D. labrax and D. punctatus. The karyotypes are very similar, even after staining with different techniques. Both species show 48 subtelocentric and acrocentric chromosomes, gradually decreasing in size. One pair of small size chromosomes has heteropycnotic and heteromorphtc short arms of longer size. These short arms are C‐ and Ag‐positive, i.e. nucleolar organizer regions, NORs, are located there. Constitutive heterochromatin is also evident as a subcentromeric band on the long arms of a large chromosome pair. CMA3‐staining confirms the location and the heteromorphism of NORs. DAPI and quinacrine produce homogeneous staining of chromosomes. A review of cytogenetic studies on ‘serranid’ species is also presented.
Does the burbot, Lota lota, have rest years between normal spawning seasons?
Authors: Pulliainen E. , Korhonen K.
Published: April 2005

A large number of sterile burbot (Lota lota) have been recorded on the northern coast of the Bothnian Bay (29–93%) and in Lake Kemijärvi in northern Finland (44%). A suggested hypothesis is that the burbot needs one or more rest years between spawning seasons to restore the fat reserves in its liver. A comparison made here between the three burbot populations (brackish water, lake and river), did not confirm this hypothesis. The somatic condition index, liver index and intestine index of the normally‐spawning river burbot, in which the percentage of non‐spawning fish was 14%, were considerably lower than those in spawned or sterile coastal or lake burbot, so that poor nutrition state did not result in sterility or rest years.
Histo‐cytological study of the liver of the cabrilla sea bass, Serranus cabrilla (Teleostei, Serranidae), an available model for marine fish experimental studies
Authors: Gonzalez G. , Crespo S. , Brusle J.
Published: April 2005

Livers of juvenile cabrilla sea basses (Serranus cabrilla) were subjected to light and electron transmission microscopy following different periods of maintenance in an aquarium. Since this fish is easy to feed in captivity and the hepatic structure was found to be comparable at the four periods tested (0, 5, 10 and 20 days), both at the histological and ultrastructural level, the liver of S. cabrilla could be an available model for marine contamination experimental studies. As in other fish species, it is not possible to distinguish the portal lobules and the triads. The Melano‐Macrophage Centres contain tipofuscins, ceroids and haemosiderin, but they do not contain any melanin. The hepatocytes are arranged in cords (two cells thick), and, at the ultrastructural level, they show numerous microvilli in the perisinusoidal and canalicular areas. The hyaloplasm includes a considerable amount of glycogen and some lipid droplets are occasionally observed. Mitochondria, rough endoplasmic reticulum and the Golgi apparatus are relatively scarce.
Use of visual landmarks by young trout (Salmo trutta) during their diel downstream post‐emergence displacement in experimental channels
Authors: Bardonnet A.
Published: April 2005

The diel timing of displacement of emerging brown trout (Salmo trutta) was studied by trapping the alevins at the downstream end of three experimental channels. The presence of phosphorescent landmarks on the substrate delayed the catches during the first hours of complete darkness, but increased them during twilight. During daylight, the presence of the landmarks was associated with greatly increased numbers of free‐swimming fishes.
Recombinant genotypes in backcrosses of male Atlantic salmon × brown trout hybrids to female Atlantic salmon
Authors: Wilkins N. P. , Courtney H. P. , Curatolo A.
Published: April 2005

When male hybrids of Atlantic salmon × brown trout were backcrossed to female Atlantic salmon, approximately 1% of diploid progeny hatched. These were shown to exhibit recombinant genotypes when examined electrophoreticalty at five enzyme loci. This is the first confirmation of genie recombination in backcrosses of these species. Triploidization greatly increases the proportion of backcross progeny which hatch.
The influence of previous feeding regime on the compensatory growth response of maturing and immature Arctic charr, Salvelinus alpinus
Authors: Jobling M. , Jørgensen E. H. , Siikavuopio S. I.
Published: April 2005

Alternating periods of food deprivation with those of unlimited provision of food depressed the growth of Arctic charr, Salvelinus alpinus, below that of controls. Fish that were deprived of food and then fed on alternate weeks (1:1) were larger than those that were exposed to periods of 1 5‐ or 3‐week deprivation and feeding (1·5:1·5 or 3:3). On receiving excess food supplies following 24 weeks on the restricted feeding regimes the previously‐restricted fish grew more rapidly than the controls. The greatest compensatory growth was displayed after the 3:3 regime, followed by the 1·5:1·5 and then the 1:1 feeding regime. At the termination of the experiment there were no significant differences in body weight between fish fed according to the different regimes during the period that food restriction was imposed. Growth patterns of the immature males and females were similar, but mature males were significantly lighter than the immature fish by the end of the experiment. Both immature and maturing fish displayed a compensatory growth response on return to adequate feeding. Beginning food restriction in May did not influence the proportions of male fish (c. 60%) which were mature in the autumn.
Humoral immune response of carp Cyprinus carpio to Myxobolus artus (Myxozoa: Myxobolidae) infection
Authors: Furuta T. , Ogawa K. , Wakabayashi H.
Published: April 2005

The circulating antibody which reacted with sonicated spores of Myxobolus artus was detected in some naturally infected carp. However, some other fish had no detectable sign of infection, though they had the antibody. When carp were injected either with intact or sonicated spores, the antibody was not produced, while fish injected either with developing stages (presporogonic and sporoblast stages) of the parasite or sonicated spores with bovine serum albumin elicited the antibody production. The results of the injection experiments suggest that (1) developing stages have antigenicity to carp, and (2) spores have lost the antigenicity; sonicated spores are haptens, with which the antibody can react. In an indirect fluorescent antibody technique, sera positive for the antigen reacted with developing stages of the parasite, but not with the spore.

The mechanism of the host immune response against M. artus is discussed in relation to a previous observation that the parasite sometimes underwent abnormal development, in which host encapsulation was imperfect or even lacking, probably leading to degeneration of pseudocysts before the completion of spore formation. It is plausible that the antibody was produced when pseudocysts which showed abnormal growth ruptured during their developing stages, resulting in exposure of the young parasite to the host immune system.
Salinity tolerance of freshwater acclimated, small‐sized Arctic charr, Salvelinus alpinus from northern Labrador
Authors: Dempson J. B.
Published: April 2005

Arctic charr, Salvelinus alpinus, less than 150 mm in size were frequently captured at sea in northern Labrador in areas where salinities of 30‰ or higher had been recorded. These captures were inconsistent with many earlier reports for other areas that indicated Arctic charr less than 150 mm in size were not found at sea. A series of salinity challenge tests was carried out in the field, using wild Ikarut River charr, and in the laboratory, using cultured Fraser River charr, to understand more about the potential fate of these small fish. The results of challenge tests with small Arctic charr (< 120 mm) indicated that at intermediate salinities (10–20‰), these fish can readily survive. In laboratory tests with salinities at 30‰, survival was size dependent and would suggest that in natural situations, small charr would require periodic access to fresh or brackish water to stay alive. The influence of water temperature on salinity tolerance may be important when fish are exposed to temperatures that are below 0° C.
Effect of salinity and temperature on the growth of yearling Arctic cisco (Coregonus autumnalis) of the Alaskan Beaufort Sea
Authors: Fechhelm R. G. , Fitzgerald P. S. , Bryan J. D. , Gallaway B. J.
Published: April 2005

The growth of 1‐year‐old Arctic cisco (Coregonus autumnalis) was monitored under laboratory conditions for fish acclimated to one of two temperatures (5 and 10° C) and one of five salinities (6, 12, 18,24, 30‰). Fish were maintained for 43 days at rations of 3% wet body weight per day at 5° C and 5% wet body weight per day at 10° C, with rations adjusted for weight gain every 7–12 days. Fish increased 9–11% in length and 55–71% in weight at 5° C, and 23–27% in length and 141–161% in weight at 10° C. Length and weight increased linearly over 43 days. There was a statistically significant effect of temperature on growth but no statistically significant effect of salinity. Higher growth rates at 10° C were partially attributable to significantly greater gross conversion efficiency at the higher temperature. Over the course of the experiment, the condition (weight per unit length) of all fish increased by 3·2 to 63·6% at 5° C and by 5·6 to 46·0% at 10° C. There was no discernible effect of salinity on condition at either temperature. These results demonstrate that, with salinity acclimation and high food ration, 1‐year‐old Arctic cisco can grow at equivalent rates across salinities ranging from 6 to 30‰. The ecological implications of the results are discussed.
Pheromone of male blue gourami and its effect on vitellogcnesis, steroidogenesis and gonadotropin cells in pituitary of the female
Authors: Degani G. , Schreibman M. P.
Published: April 2005

Female Trichogaster trichopterus were exposed to aquarium water in which males had built nests. Gonadotropin cells in the pituitary gland, and exovitellogenesis and steroidogenesis in the ovary were studied. In females in which the percentage of oocytes in vitellogenesis (%V) was low initially, it rose significantly in comparison with an unexposed control group. In females in which the %V was higher initially, it increased further, and in addition a significant percentage of oocytes reached maturation. Thin layer chromatography, using the precursors 3H‐pregnenolone and 14progesterone, revealed high yields of the steroids 17β‐estradiol (E2), 17α,20β‐dihydroxy‐4‐pregnen‐3‐one (17,20‐P), 5β‐pregane,3α,17α,20β‐triol (5β‐P‐triol) and 11‐ketotestosterone (11KT) in both experimental groups. Significant differences were found in E2, 17,20‐P and 5β‐P‐triol between the test and control groups. The immunoresponse of GtH‐producing cells in the pituitary of the females maintained in nest water was lower than in the control group, suggesting that the GtH was secreted from the cells, which would explain the vitellogenic and steroidogenic changes found in the ovary.
Superoxide dismutasc activity in lite skin of fish
Authors: Nakano T. , Sato M. , Takeuchi M.
Published: April 2005

Superoxide dismutase (SOD) activity in the skin of fish was observed to be higher in the dark than in the light parts. SOD activities in both parts were confirmed by visualisation of SOD activity on polyacrylamide gels. We suggest that the distribution of higher SOD in the dark parts of the skin might be related to melanization and to regulate of reactive oxygen species.
Presence of an oesophageal mucus plug at the time of emergence in grayling (Thymallus thymallus) and Atlantic salmon (Salmo salar)
Authors: Bardonnet A. , Gaudin P. , Grolet O. , Thorpe J. E.
Published: April 2005

Grayling (Thymallus thymallus) and salmon (salmo solar) Fry were trapped on emergence from development under gravel.The Oesophagus was completely blocked by mueus in 30% of the emergent grayling as compared to only 6.5% of the salmon
Effects of food density and temperature on feeding and growth of young inland silversides (Menidia beryllina)
Authors: Letcher B. H. , Bengtson D. A.
Published: April 2005

Food consumption and growth rates of 7–28‐day‐old Menidia beryllina were measured in response to natural ranges of temperature and prey availability. Feeding level, temperature and age all had significant effects on growth rate, although the effect of feeding level explained most of the variance. Feeding level also had a significant effect on gross growth efficiency, but temperature and age did not. Absolute growth rates (mg per day) increased dramatically with temperature, feeding level, and age. Variability in growth was greatest for fish feeding at the lowest feeding level. For a given fish weight, temperature had a positive effect on consumption rate, and maximum consumption (Cmax) of any treatment combination reached 75% body weight per day. Maximum growth rate was estimated at 24.6% body weight per day, and gross growth efficiency reached an estimated maximum of 0.375 at an ingestion rate of 25% body weight per day. Starved larvae lost on average 5.4% body weight per day and larvae required 6.4% body weight food consumption per day for maintenance. Multiple regressions of feeding level, temperature, and age/size on instantaneous growth rates indicated that increases in temperature increased maintenance requirements and required that fish consume a greater proportion of Cmax to attain maximum growth. Growth rates decreased with increases in temperature for fish eating a specific weight of food.
Is tilting behaviour at low swimming speeds unique to negatively buoyant fish? Observations on steelhead trout, Oncorhynchus mykiss, and bluegill, Lepomis macrochirus
Authors: Webb P. W.
Published: April 2005

When swimming at low speeds, steelhead trout and bluegill sunfish tilted the body at an angle to the mean swimming direction. Trout swam using continuous body/caudal fin undulation, with a positive (head‐up) tilt angle (0, degrees) that decreased with swimming speed (u, cm s−1) according to: 0=(164±96).u(−1.14±0.41) (regression coefficients; mean±2s.e.). Bluegill swimming gaits were more diverse and negative (head down) tilt angles were usual. Tilt angle was −3·0 ± 0.9° in pectoral fin swimming at speeds of approximately 0.2–1.7 body length s−1 (Ls−1; 3–24 cm s−1), −4.5 ±2.6° during pectoral fin plus body/caudal fin swimming at 1·2–1·7 L s−1 (17–24cm s−1), and −5.0± 1.0° during continuous body/caudal fin swimming at 1.6 and 2.5 L s−1 (22 and 35cm s−1). At higher speeds, bluegill used burst‐and‐coast swimming for which the tilt angle was 0.1±0.6°. These observations suggest that tilting is a general phenomenon of low speed swimming at which stabilizers lose their effectiveness. Tilting is interpreted as an active compensatory mechanism associated with increased drag and concomitant increased propulsor velocities to provide better stabilizing forces. Increased drag associated with trimming also explains the well‐known observation that the relationship between tail‐beat frequency and swimming speed does not pass through the origin. Energy dissipated because of the drag increases at low swimming speeds is presumably smaller than that which would occur with unstable swimming.
Genetic relationships of Brachygobius and related brackish Indo‐west Pacific and Australasian genera (Teleostei: Gobiidae)
Authors: McKay S. I.
Published: April 2005

Horizontal starch gel electrophoresis was employed to analyse genetic variation, at 19 isozyme loci, in six putatively related species of gobies (Brachygobius aggregatus, B. doriae, Pandaka lidwilli, Pseudogobius olorum, Pseudogobius sp. and Redigobius sp.), using seven other gobiine species as an outgroup. Allozyme data was analysed both cladistically and phenetically, all treatments confirming the monophyly of the group. Pandaka is confirmed as the sister genus to Brachygobius, these genera forming a crown group, with Redigobius and Pseudogobius forming successive sister groups. This scenario is in agreement with morphological hypotheses of phylogeny. However, this lineage appears to be relatively unrelated to other groups within the Gobiinae
Incidences of gross morphological disorders in barbel (Barbus barbus) in three rivers in southern England
Authors: Tyler C. R. , Everett S.
Published: April 2005

Incidences of gross morphological disorders in barbel (Barbus barbus) were investigated in three rivers in southern England. The water quality at the sites chosen for study on the Rivers Teme, Kennet and Lee were classified (according to the criteria of the National Water Council, 1978) as 1A, IB and 2, respectively. Generally, low levels of gross morphological abnormalities were seen in fish caught in the Teme and Kennet, although there were incidences of ocular disorders and extra barbules in 10 and 7%, respectively, of the Kennet fish. No tumours were found in barbel from the River Teme whereas there was a 2% incidence in the Kennet fish. In contrast barbel from the River Lee showed high levels of all the gross morphological disorders, especially haemorrhagic patches on the ventral surface (36%) and ocular disorders (72%). Tumours were seen in 25% of the barbel caught in the River Lee. The incidences of most of these gross morphological disorders did not appear to be age related. The possibility that these disorders were related to water quality is discussed.
On the diel rhythms in metabolism and activity of post‐hatching lesser spotted dogfish, Scyliorhinus canicula
Authors: Sims D. W. , Davies S. J. , Bone Q.
Published: April 2005

The diel rhythms in metabolic rate (MR) and activity level (AL) were measured for single post‐hatching dogfish (weight range, 2.76–10.61 g) at 15° C by the indirect calorimetric method of rate of oxygen consumption (VO2) and by video‐observation respectively, over a period of 72 b. The mean VO2 increased from 62.0 (s.e. 2.9) mg O2 kg−1 h−1 in the daylight hours to 85.5 (s.e. 3.1) mg O2 kg−1 h−1 during the dark (light regíme, 12 h L: 12 h D). The simultaneous measurement of AL also showed mean night elevation from 0.6 (s.e. 0.2) min h−1 in the light phase to 14.5 (s.e. 1.6) min h−1 during the darkness. Bimodal nocturnal activity (BNA) was exhibited by the post‐hatching dogfish within the 12 h dark period, with VO2 increasing from 71.4 (s.e. 2.8) mg O2 kg−1 h−1 before 01.00 hours to 99.5 (s.e. 4.2) mg O2 kg−1 h−1 after 01.00 hours. Similarly, AL also increased from 8.9 (s.e. I.7)min h−1 before 01.00 hours to 21.1 (s.e. 2.8) min h−1 after 01.00 hours. The importance of the results presented to the natural behavioural ecology of the hatching dogfish are discussed.
Diel rhythm of emergence and of first displacement downstream in trout (Salmo trutta), Atlantic salmon (S. salar) and grayling (Thymallus thymallus)
Authors: Bardonnet A. , Gaudin P. , Thorpe J. E.
Published: April 2005

The diel rhythm of emergence from the gravel and displacement downstream has been studied in three salmonoid species: brown trout (Salmo trutta L.), Atlantic salmon (S. saiar L.) and grayling (Thymallus thymallus L.). Grayling emerged in the morning but delayed downstream displacement until the night, while the Salmo species emerged just before downstream displacement chiefly at night.
Community ecology of the parasites of adult spot, Leiostomus xanthurus, and Atlantic croaker, Micropogonias undulatus (Sciaenidae) in the Cape Hatteras region
Authors: Thoney D. A.
Published: April 2005

Twenty‐three species of metazoan parasites were recorded from adult spot and 26 from adult croaker. Of the 33 parasitic species found, 17 occurred in both spot and croaker. No significant differences in intensity of parasites occurred between sexes of either spot or croaker. All of the parasites had over‐dispersed, or clumped, distributions among hosts. Adult spot and croaker collected offshore had much greater species‐richness, diversity, and total number of individual parasites than juvenile fishes collected in adjoining estuaries during another study. The juvenile spot and croaker had less time to acquire parasites and inhabited less diverse and more confined habitats in inshore estuaries, which resulted in less diverse parasite communities than offshore fishes. The number of species and diversity of parasites in adult fish was greater in croaker than spot. However, when only gastrointestinal helminths were considered, spot had greater species‐richness as well as greater numbers of individual helminths, suggesting that they had a more diverse diet and that they fed on more infected intermediate hosts than croaker. In both adult spot and croaker the mean number of parasitic species was greater than those of freshwater fishes and fewer than those for birds and mammals. The total number of individual parasites was similar to that of freshwater fishes. The opportunistic diet and the migratory habits of both spot and croaker contribute to their diverse parasite faunas. Comparison of adult spot and croaker parasite faunas collected offshore indicated that their respective parasite component communities were distinct and that similar parasite infracommunity variability existed in both hosts and that their communities were not ‘random’ samples, but restricted subsets of the compound community. Although the parasite dominance hierarchy in adults of both species varied slightly between areas and seasons sampled, there appeared to be a predictable dominant species that was accompanied by subordinate, less predictable species. However, the variability in both relative intensities and presence‐absence of parasites within communities resulting from their diverse diets make them less predictable than those of other vertebrates with less diverse diets such as the lesser scaup duck and more like those of other marine fishes.
Differential utilization of storage lipids and storage proteins by Northwest Atlantic herring (Clupea harengus harengus)
Authors: Bradford R. G.
Published: April 2005

Utilization of storage lipids and storage proteins by non‐feeding north‐west Atlantic herring was assessed under conditions of: (1) concurrent gonad maturation and overwintering periods with differing rates of gonad development for males and females (spring‐spawncrs); (2) overwintering, reproductively dormant and spent males and females (autumn‐spawners); and (3) approximately equivalent rates of gonad development during late summer for males and females (autumn‐spawners). Storage lipids were depleted by all non‐feeding fish but storage proteins were depleted only by herring with measurable gonad development during the observation period independently of season (female spring‐spawners, maturing male and female autumn‐spawners). The analyses indicate that storage lipids sustain routine and active metabolism while storage proteins are utilized to develop gonad. Therefore, the relative investment into reproduction versus routine and active metabolism can be evaluated separately for non‐feeding herring using readily obtainable tissue proximate composition data.
The use of whole‐body sodium, potassium and calcium content to identify the nutrient status of first year salmon fry
Authors: Shackley P. E. , Talbot C. , Cowan A.
Published: April 2005

Samples of fed and unfed hatchery reared Atlantic salmon fry and parr were analysed for body water and whole body Na, K and Ca content. From these body parameters it is possible to estimate the relative proportions of the skeletal mass, and intra‐ and extracellular spaces. These data can be applied to estimating the nutritional status of parr sampled at random from hatchery, and possibly from wild populations. When fish with a dry weight of about 25 and 70 mg were deprived of artificial food for 27 and 21 days, respectively, the Na/K ratio rose to 0.59 and 0.80 compared with 0.37 in the controls. With fish of about 475 mg in weight, percentage water content was a better indicator of undernourishment. The use of the K+: Ca2+ ratio to compare the amount of cellular material with the skeletal mass was a good indicator of nutritional depletion, especially in smaller fish.
The effect of sand and light on predation of juvenile plaice (Pleuronectes platessa) by fishes and crustaceans
Authors: Ansell A. D. , Gibson R. N.
Published: April 2005

Rates of predation on 0‐group plaice, Pleuronectes platessa. in aquaria were compared under four different combinations of conditions to test the hypothesis that the presence of sand in which they may bury affords a refuge from predators. The effect of light and darkness on predation rate was also examined, Two crustaceans, the shrimp, Crangon crangon, and the portunid crab, Liocarcinus holatus, and two fishes, cod, Gadus morhua, and pollack, Pollachius pollachius, were used as predators. Predaton rates were significantly higher in the dark for all predators except pollack. Predation rates in the absence of sand were signifcantly greater only for pollack. The results suggest that predation rates on plaice during their juvenile nursery stage on sandy beaches will be significantly greater during darkness than during the day. Burying in sand appears to provide only a partial refuge from predation, perhaps because natural predators have evolved effective methods of foraging for buried prey.
Biology of the black‐stripe minnow Galaxiella nigvostriata, including comparisons with the other two Galaxiella species
Authors: Pen L. J. , Gill H. S. , Humphries P. , Potter I. C.
Published: April 2005

The growth, age composition, reproductive biology and diet of Galaxiella nigrostriata in seasonal water bodies in south‐western Australia are described and compared with G. munda and G. pusilla. Like the other two Galaxiella species, G. nigrostriata has a 1 year life cycle. The mean length attained by female G. nigrostriata at sexual maturity is approximately 37 mm, compared with about 47 and 28 mm for G. munda and G. pusilla, respectively. Like G. munda, G. nigrostriata is a multiple spawner. Although all three Galaxiella species breed mainly in winter and early spring, spawning occurs earlier in G. nigrostriata than in the other two species. An early production of offspring enables the young females and males of this species to reach approximately 78 and 88%, respectively, of their ultimate body length by early summer. Such a prolonged period of early and relatively rapid growth is advantageous to G. nigrostriata, since this species lives in water bodies that often dry up during the summer and early autumn and thus cannot grow during this period. The gonads start to undergo rapid development in autumn, when the pools begin to fill with water following the onset of the seasonal rains. All three Galaxielta species are carnivores. Galaxiella nigrostriata mainly takes prey from the water column and the water surface, G. pusilla focuses on prey in the water column and benthos, and G. munda feeds widely on prey on the water surface, throughout the water column and from the benthos. The prevalence of small prey, such as cladocera and calanoid copepods, is greater in the diets of G. nigrostriata and G. pusilla than in that of G. munda.
Gonadosomatic index in Barbus longiceps, Capoeta damascina and their natural hybrid (Pisces, Cyprinidae), versus spermatozoan index in the parental males
Authors: Stoumboudi M. Th. , Villwock W. , Sela J. , Abraham M.
Published: April 2005

The yearly gonadal cycle of two Kinneret teleosts, Barbus longiceps and Capoeta damascina and of their hybrid, was assessed by measuring the gonadosomatic index (GSI) in both sexes, as well as the spermatozoan index (SPI) in the males. SPI was established through a computerized analysis system, using light microscopy images of histological preparations of the testes.

Barbus longiceps specimens had highest GSI in March, 6.31 for males and 1.40 for females. Capoela damascina had highest GS1 in January, 6.63 for males and 6.88 for females. In the male‐like hybrids, the highest GSI was 5.57 in February, and in female‐like hybrids 1.83 in March; no gametes were ever formed in hybrid gonads. The highest SPI appeared in B. longiceps in April, while in C. damascina the highest SPI was found in March. In both species, the highest SPI was attained several weeks after the highest GSI was observed. It is suggested that the peak of the breeding season of both species is actually represented by the highest SPI. In males, the decreasing GSI, which corresponds to the highest SPI, represents the loss of gonad weight, which is due to the elimination of the spermatid residual bodies, prior to spermiation. In the females the decreasing GSI is the result of ovulation, and characterizes the peak of spawning activity.
Movement and site fidelity in young brown trout Salmo trutta populations in a southern Irish stream
Authors: Bridcut E. E. , Giller P. S.
Published: April 2005

Populations of brown trout Salmo trutta were monitored at a number of sites within a single stream, using an individual marking technique and recapturing uniquely marked fish repeatedly over a period of 12 months. Individual 1 + and 2 + resident brown trout in the Glenfinish River were found to consist of stationary and mobile component populations. The latter population consisted of a number of individuals observed moving mostly in an upstream direction, within a range of 0.03–2.24 km. On a large spatial scale, individuals in the stationary component population exhibited some degree of home site fidelity within the stream, over a period of 3–4 months, after which the fish tended to move from the site. Within sites, fidelity to either riffle or pool habitats, mostly the latter, was apparent in a proportion of the population. On a smaller scale, fidelity to the exact position with respect to boulders in the stream was also evident in a number of individuals. Home range size was calculated amongst these individuals, with ranges of up to 20 m recorded.
Grazing rates on toxic and non‐toxic strains of cyanobacteria byHypophthalmichthys molitrixandOreochromis niloticus
Authors: Beveridge M. C. M. , Baird D. J. , Rahmatullah S. M. , Lawton L. A. , Beattie K. A. , Codd G. A.
Published: April 2005

The tilapiaOreochromis niloticusand the silver carpHypophthalmichthys molitrixwere exposed to toxic and non‐toxic strains of the cyanobacteriumMicrocystis aeruginosain order to determine if cells of the toxic strain were ingested and, if not, by what mechanism they were excluded. Enumeration of cyanobacterial particles before and after exposure to fish showed that there were no significant differences (P<0.05) at the end of the trial between the toxic treatment and the control consisting of toxicM. aeruginosawith no fish. Fish exposed to the non‐toxic strain increased opercular beat rate, elevating the volumes of water and food material passed over the gills whereas those that were held in the toxic strain did not. Of the cyanobacterial toxins (microcystins) presented to the fish, most were in the cyanobacterial cells, toxin levels in the water being below the level of detectability (<250 ng l−1), The ability of the fish to differentiate between toxic and non‐toxic cyanobacterial strains may thus be determined by very low levels of extracellular microcystins or/and other features which distinguish toxic from non‐toxicM. aeruginosastrains, such as cell surface components.
Genetic relationships among the shads (Alosa) revealed by mitochondrial DNA analysis
Authors: Bentzen P. , Leggett W. C. , Brown G. G.
Published: April 2005

We surveyed restriction site differences in mitochondrial DNA. (mtDNA) among five species of shad (Alosa) from North America and Europe. Allis shad, Alosa alosa and twaite shad, Alosa fallax shared two divergent genotype groups, suggesting that the two forms are either a single species, or are distinct species that have hybridized. Phenetic and cladistic analyses of the relationships among the mitochondrial genotypes defined two groups of shad, corresponding to the subgenera, Alosa and Pomolobus. The mean estimated sequence divergence between the mtDNAs of these two groups of shad was 6.5%. Taken in conjunction with fossil data, this divergence estimate suggests that the rate of mtDNA divergence between the two subgenera has been almost 10‐fold lower than the ‘conventional’ clock calibration for mtDNA.
Peculiarities in the organization of testis of Ophidian sp. (Pisces Teleostei). Evidence for two types of spermatogenesis in teleost fish
Authors: Mattei X. , Siau Y. , Thiaw O. T. , Thiam D.
Published: April 2005

The walls of lobules in the testis of Ophidion sp. are composed of Scrtoli cells and young germinal cells (spermatogonia and spermatocytes). Spermatocytes are linked by cytoplasmic bridges. The associations of Sertoli cells and spermatocytes constitute true cysts. Meiosis takes place in the cysts. When meiosis is complete, cysts open. Spermatids are released into the lumen of the lobules and the cyloplasmic bridges break down. Spermiogenesis occurs in the lumen. Spermatids at various levels of spermiogenesis are then mixed with ripe spermatozoa. In teleosts we thus recognize two types of spermatogenesis: a cystic type where spermatogenesis is completed within cysts, and leads to synchronous development of germ‐cells; and a semi‐cystic type, where spermatogenesis occurs partly outside cysts. This may produce asynchronous spermatogenesis.
Whale shark observations off Kuwait's coast in 1992
Authors: Bishop J. M. , Abdul‐Ghaffar A.‐R.
Published: April 2005

Three well‐documented accounts of whale sharks, Rhiniodon typus, in Kuwait's coastal waters represent the first report of this species in the area since 1968.
Genetic variation in Lake Erie yellow perch (Percaflavescem) demonstrated by mitochondrial DNA analysis
Authors: Billington N.
Published: April 2005

Restriction fragment length polymorphism analysis of yellow perch (Perca flavescens) mitochondrial DNA from a Lake Erie population revealed seven variants in 22 fish (nucleon diversity 0.481). These fish were collected from an area where previous studies using allozymes had failed to reveal any genetic variation.
Optic cyst in a cyprinid teleost
Authors: Nag T. C. , Bhattacharjee J.
Published: April 2005

Retinal herniation, leading to the formation of a small optic cyst in the choroid, is reported for the first time in a fish (Acrossocheilus hexagonolepis). The herniation resulted in the disorientation of photoreceptors and the displacement of the choroid gland towards the suprachoroid.
Gill X‐cell lesions in American plaice (Hippoglossoides platessoides) concurrent with lymphocystis infection
Authors: MacLean S. A. , Despres‐Patanjo L. I.
Published: April 2005

This paper documents the first report of concurrent infections of lymphocystis lesions and X‐cells and the varied associations between multiple, clustered or single lymphocystis lesions and X‐cells in a NW Atlantic pleuronectid.
Genetic polymorphism of adenosine deaminase (ADA; E.C. 3.5.4.4.) in allis shad, Alosa alosa and twaite shad, Alosa fallax
Authors: Alexandrino P. J. , Sousa C. , Pereira A. , Ferrand N.
Published: April 2005

A genetic polymorphism of adenosine deaminase (ADA), is described for the first time in European shad species, Alosa alosa and Alosa fallax. Significant heterogeneity in gene frequencies was found, both between species and within species.
Latitudinal clines in life‐history variables of anadromous brown trout in Europe
Authors: Jonsson B. , L'Abée‐Lund J. H.
Published: April 2005

Based on published data, we reviewed clinal variations in life‐history characteristics of anadromous brown trout Salmo trutta from 102 European rivers at latitudes between 54 and 70° N. Growth rate in fresh water, mean smolt age, mean sea age at first sexual maturity, proportion of repeal spawners among adults, longevity, and length of adult life span exhibited latitudinal clines. Brown trout grew faster in fresh water, smolted and matured younger, lived fewer years but spawned more times in the south than in the north. The life‐history traits studied were often correlated. Longevity, smolt age and sea age at maturity were negatively and smolt length and proportion of repeat spawners among adults were positively correlated with growth rate in fresh water. Longevity was positively correlated with smolt age and sea age at maturity. The latter also increased with increasing smolt age. None of these significant correlations among life history variables, except for those between smolt age and parr growth and proportion of repeat spawners and parr growth, are latitudinal effects. We do not know to what extent the latitudinal variation in life–history traits reflects phenotypic plasticity and to what extent it is caused by inherited differences among populations.
Seasonal distribution and duration of the planktonic stage of Dover sole, Solea solea, larvae in the Bay of Biscay: an hypothesis
Authors: Amara R. , Lagardere F. , Desaunay Y.
Published: April 2005

The possibility of deriving a prediction about the effect of seasonal variations in the duration of the planktonic larval phase on the dispersal of larval Dover sole was investigated. During six cruises, from February to May 1992, the distribution of sole larvae was studied along a 100‐km transect, from the offshore spawning grounds to the coastal nurseries of the Bay of Biscay (France). Samples (n= 189) were collected with a suprabenthic sampler, and vertical profiles of water temperature and salinity were recorded simultaneously. Counts of otolith increments of larval stage 4b (onset of metamorphosis) were used to estimate the duration of the planktonic life. Duration of the larval phase decreases by about 15 days (37%) with water temperature increase (between 8° in February and 11.2° C in May). Sole larvae occur from the coastal area to 100 km offshore. Within the same cruise, no difference in the duration of the planktonic life was observed between the larvae caught in the onshore and the offshore area. In spite of seasonal differences in abundance, the extent and the shape of the larval distributions during the period of study suggest that the seasonal variations in the duration of the planktonic life did not affect the larval distribution.
The genetic structure and microdistribution of shoals of Phoxinus phoxinus, the European minnow
Authors: Naish K.‐A. , Carvalho G. R. , Pitcher T. J.
Published: April 2005

Efficient foraging and a reduction in predation risk have been proposed as reasons for shoal formation. Some behaviours in cyprinid shoals are at first sight altruistic (e.g. predator inspection behaviour, reactions to alarm substance), such that kin selection may have been involved in their evolution. If shoaling behaviour does evolve through kin selection, then genetic differentiation is expected to be greater between shoals than within shoals. Such a hypothesis was tested here by examining shoal integrity and the relatedness of individuals within and between shoals in the European minnow, Phoxinus phoxinus, using nuclear and mitochondrial DNA markers. The breeding structure of 13 minnow shoals collected from Dorset and North Wales, U.K., was examined using allozymes. Genetic affinity within and between shoals was tested using mitochondrial DNA and multi‐locus DNA fingerprinting. Shoals consisted of a random assortment of allozyme genotypes, shoal members did not share the same maternal mtDNA lineages and DNA fingerprint profiles were as varied within shoals as between them. The data indicate that it is unlikely that kin selection occurs in P. phoxinus and there is no apparent relationship between shoaling behaviour and genotype distribution in this species.
Distribution of mitochondrial DNA variation in lake sturgeon (Adpenser fulvescens) from the Moose River basin, Ontario, Canada
Authors: Ferguson M. M. , Bernatchez L. , Gatt M. , Konkle B. R. , Lee S. , Malott M. L. , McKinley R. S.
Published: April 2005

We analysed mitochondrial DNA (mtDNA) variation of lake sturgeon (Adpenser fulvescens) from the Moose River basin. Our objective was to address various proximate and ultimate factors which may influence the distribution of lake sturgeon mtDNA haplotype lineages in this watershed. The lake sturgeon sampled were characterized by only two mtDNA hapiotypes based on a restriction fragment length polymorphism analysis with 40 restriction endonucleases and direct sequencing of 275 nucleotides in the mtDNA control region. We detected no heterogeneity in the mtDNA haplotype frequencies of lake sturgeon captured from different sites within rivers including those separated by major hydroelectric installations. However, lake sturgeon from one tributary had significantly different haplotype frequencies than those from other tributaries suggesting that they composed a discrete genetic stock. These results suggest that gene flow among most sites is significant and is an important factor affecting the distribution of mtDNA variation in this species. The genetic structuring and diversity are discussed in relation to lake sturgeon management and conservation.
Variability in the distribution and abundance of stream salmonids, and the associated use of habitat models
Authors: Milner N. J. , Wyatt R. J. , Scott M. D.
Published: April 2005

The effective management of salmonid fisheries requires that the factors influencing variation in the abundance of stream populations are understood. The use of habitat models to explain the spatial component of population variance offers potential for management, but has not previously been set in the context of long term variation in population abundance because of the lack of suitable data sets. This paper examines contributions of spatial and temporal factors lo fish density variance using a 10‐year data set from five tributaries of the River Conwy, North Wales. Recently developed habitat models were applied to the data to test their ability to explain nominal spatial variance. Spatial variance accounted for between 21 and 62% of the overall variance of salmonid abundance, and habitat models explained up to 95% of the spatial variance component. Synchrony in population variation amongst sites within and between tributaries is described, and some of the factors that may influence this are discussed.
The consequences of habitat occupation and habitat overlap of the introduced tilapia Oreochromis mossambicus and indigenous fish species for fishery management in a Sri Lankan reservoir
Authors: Pet J. S. , Piet G. J.
Published: April 2005

Habitat occupation and habitat overlap of the introduced tilapia Oreochromis mossambicus and co‐occurring indigenous fish species were studied in a shallow lowland reservoir in Sri Lanka. Results were used to discuss the possible existence of empty habitats in reservoirs and the position of the introduced O. mossambicus in the fish community. Predictions were made of the effects of a subsidiary small‐meshed gillnet fishery for indigenous minor cyprinids on the yield of tilapia. The zooplanktivorous halfbeak Hyporamphus gaimardi, an indigenous invader from brackish water estuaries and lagoons, has successfully colonized the pelagic habitat in this reservoir. The habitat of the introduced O. mossambicus overlapped significantly with those of the indigenous minor cyprinids. Only the smallest size classes of O. mossambicus (below 45 mm) arc spatially segregated from these cyprinids. Spatial distribution patterns are influenced by the rainy seasons which trigger an inshore movement of O. mossambicus and several other species around November and May. Barbus spp, (Cyprinidae) need riverine habitats for spawning, but for all other species the available habitats within the reservoir are suitable to complete their full life cycle. Exploitation of Barbus spp. with gillnets with a mesh size of 30‐mm stretched mesh is predicted to have considerable detrimental effects on the existing fishery for O. mossambicus. However, a gillnet fishery with 15‐mm stretched mesh to exploit Amblypharyngodon melettinus, Rasbora daniconius and H. gaimardi in the open water zone is expected to be successful without harming the existing fishery for O, mossambicus or the populations of Barbus spp.
Temporal and spatial variation in the species composition of trawl samples from a demersal fish community
Authors: Albert O. T. , Bergstad O. A.
Published: April 2005

The temporal variation in species and size structure of the demersal fish community of a 70–150m deep open coastal locality of SW Norway was studied by multivariate analysis of bottom trawl data both from surveys and from fixed locations sampled repeatedly through 48‐h periods. The trawl data were related to echo recordings from individual tows made during the 48‐h experiments, Between‐site variation was greater than short‐term variation at single sites. Short‐term variation was largely cyclical, diel variation, involving several species. Catches of the numerically dominating species, Sebastes viviparus and Trisopterus esmarki, did not follow any diel patterns. Acoustical recordings suggested that these species undertook diel vertical migrations largely within the lower 5 m of the water column. This corresponds to the vertical opening of the trawl.
An analysis of the distribution of fish species in a large prairie lake
Authors: Craig J. F. , Babaluk J. A.
Published: April 2005

The distribution of fishes in Dauphin Lake, a large, shallow, turbid, prairie lake in west‐central Manitoba, was examined using gillnets. Catch per unit effort was used to assess differences in distribution thai may be attributed lo year, season, lake zone (inshore, offshore), substratum, water depth, water temperature, turbidity and presence of other fish species. Although 13 species were caught, only the distributions of the six most abundant was analysed. Variation in number of species caught was attributed mainly to lake zone, water depth and water temperature. White sucker (Catastomus commersoni) distribution can be explained by zone and temperature. Shorthead redhorse (Moxostoma macrolepidotum) catches were related to depth and temperature. Cisco (Coregonus artedii) catches varied with year, zone and temperature. Variances in northern pike (Esox Indus) distribution reflected year and zone. Walleye (Stizostedkm vitreum) varied with year, depth and temperature and differences in the catches of yellow perch (Pertaflurescens) were attributed to year, depth, temperature and turbidity. They were also positively correlated to the numbers of northern pike caught.
Do small riverine fish move inshore at night?
Authors: Copp G. H. , Jurajda P.
Published: April 2005

We tested the hypothesis that numbers of small fish increase along river banks with decreasing light levels. Fish were sampled every 3h over a 24‐h period (30–31 August 1992) along two adjacent stretches of bank (one shallow sand, one steep boulder) on the R. Morava near Breelav, Czech Republic. The size of fish was significantly greater along the boulder bank than along the sand bank. Numbers of fish along the steep boulder bank did not increase with decreasing light levels, except in Rhodeus sericeus and perch Perca fluviatilis, which were significantly more abundant at night. Along the shallow sand bank, all species increased in number at night, most significantly so. As light levels decreased, numbers of whitefin gudgeon Gobio albipinnatus and roach Rutilus rutilus decreased along the boulder bank, as their numbers increased along the sand bank, suggesting a dusk migration to the sand bank to avoid predation. This assumption was corroborated by the significantly higher number of potentially piscivorous fishes (P. ftuviatilis and chub Leuciscus cephalus≥ 80 mm) along the boulder bank during the night.