bluuebunny/crossref_metadata_2025 huggingface dataset:
Factors affecting the habitat selection of tench in a shallow eutrophic lake
Authors: Perrow M. R. , Jowitt A. J. D. , Johnsonf S. R.
Published: April 2005

The activity patterns and habitat selection of tench in a shallow eutrophic lake were determined by radio telemetry. Environmental variables, including prey availability, depth and vegetational composition were quantified in order to explain observed patterns of distribution. Tench were generally only active at night, foraging on benthic animal prey, particularly chironomid larvae. Feeding fish clearly selected for particular locations although only weak associations with depth and densities of preferred prey were found. In addition, it appears that fish spent a considerable time searching for prey and travelling relatively large distances in the process, with the result that only relatively few prey were ingested during the course of a night. During daylight, fish were almost completely inactive, resting together in favoured locations and displaying a strong association for the littoral emergent vascular plant, Typha angustifolia. This may be because Typha usually grows in relatively deep water and forms stands of relatively widely spaced stems, thus allowing such large fish to penetrate deeply into cover. Management of eutrophic waters to encourage tench should take this habitat preference into account.
The recruitment success of Vimba vimba transferred over a dam
Authors: Backiel T. , Bontemps S.
Published: April 2005

A commercially exploited cyprinid, Vimba vimba (L.), was caught just below the Wlocláwek dam during its upstream spawning migration in the Vistula R., Poland, in October and released l.5–2km above the dam, which was negotiated by very few fish. Recruitment indices originating from these transfers, which were carried out over 7 years, correlated well with respective contributions to the commercial catch over 10 years.
Patch exploitation by small gadoids: evidence for an asymmetric tidal effect
Authors: Hall S. J. , Tuck I. D. , Robertson M. R. , Basford D. J. , Heaney S. D.
Published: April 2005

The attraction of small gadoids to physically disturbed seabed patches was examined experimentally using a modified remote operated vehicle. Video observations were made of simulated disturbances to investigate the influence of tidal state, time of day and current speed on the pattern of exploitation. Fish were more likely to be present in disturbed patches, and when present, occurred in significantly greater numbers than in control areas. However, this response was dependent on tidal state, occurring only on rising tides.
Lake flies and the deep‐water demersal fish community of Lake Malawi
Authors: Allison E. H. , Irvine K. , Thompson A. B.
Published: April 2005

Larvae and pupae ofChaoborus edulismay be the most important food resource of some deep‐water demersal fish species in southern Lake Malawi.C. edulisfeed on crustacean zooplankton, which in turn feed on phytoplankton. Hence, demersal fish production is supported directly by planktonic primary production, rather than through a detrital food chain.
Allozyme and mtDNA divergence between Atlantic salmon populations in North Wales
Authors: O'Connell M. , Skibinski D. O. F. , Beardmore J. A.
Published: April 2005

Allozyme variation differentiates between Atlantic salmon Salmo salar populations in North Wales to a greater extent than mtDNA diversity.
Feeding strategy and growth of cyprinids in the littoral zone of Lake Balaton
Authors: Specziár A. , Tölg L. , Bíró P.
Published: April 2005

The growth, diet and feeding strategy of five phytophil or phytolithophil species of Cyprinidae from the littoral habitats of Lake Balaton were investigated by examining their scales and foregut contents. The relationships between the total anterior radii of scales and the standard lengths were represented best by a power function for white breamBlicca bjoerkna, and linear functions for common breamAbramis brama, roachRutilus rutilusand wild goldfishCarassius auratus gibelio, respectively. The backcalculated mean lengths for the first age groups of common bream, white bream and roach did not differ statistically from those obtained by direct observation on 0 group fish in late November 1995. Compared to other waters, common bream grows slowly, wild goldfish and roach rapidly, while the growth rate of white bream can be considered of medium speed in Lake Balaton. Common bream showed a generalized feeding pattern, consuming mainly chironomid larvae, detritus andCorophium curvispinun. Roach showed a clear shift between specialization forDreissenaand algae. Despite the dense population ofD. polymorphain the lake, the significance of the herbivorous adaptation of roach has not yet been made clear. Wild goldfish consumed mainly detritus but, in the open water region, it shifted to zooplankton. White bream preyed chiefly onD. polymorpha, but showed a mixed feeding pattern and utilized most of the available food resources. Carp had the most specialized feeding strategy and preyed mainly onD. polymorpha. According to the discriminant analysis, the five cyprinids exhibited significant food resource partitioning.
Cloning and sequencing of cDNAs of the β‐globin gene family in carp
Authors: Yoshizaki G. , Hirono I. , Aoki T. , Takashima F.
Published: April 2005

A total blood cell cDNA library was constructed using a 3‐year‐old carp Cyprinus carpio. A β‐globin cDNA (CβG1) was identified from the library by the polymerase chain reaction using a β‐globin‐specific primer deduced from the carp β‐globin‐A amino acid sequence. Also, five additional types of β‐globin cDNAs (CβG2∼6) were isolated by colony hybridization using CβG1 as a probe. Sequence analysis revealed that these CβGs encoded 147 amino acids, and the deduced amino acid sequences showed high identity (89·1–95·2%) to previously reported carp β‐globin amino acid sequences. The nucleotide sequences of the CβGs were very similar (identity 96·0–99·6%) and the expression levels of CβG1∼6 were 28·6, 28·6, 21·4, 14·3, 3·6 and 3·6% of the total number of cloned CβGs, respectively. Although the complete amino acid sequence identities between the CβGs and the β‐globin of higher vertebrates were low, functionally important regions such as the α‐βcontact region and haem contact region were well conserved. These data showed that, as in higher vertebrates, the adult carp has a multiple β‐globin gene family (at least six members). However, transcripts encoding four types of peptides (CβG1 type, CβG2 and 3 type, CβG5 type, and CβG4 and 6 type) were expressed at relatively high levels, this being a unique character of the carp haemoglobin system.
Importance of ontogenetic habitat shifts to juvenile output and life history of Atlantic salmon in a large subarctic river: an approach based on analysis of scale characteristics
Authors: Erkinaro J. , Dempson J. B. , Julkunen M. , Niemelä E.
Published: April 2005

Juvenile and adult scale characteristics were used to compare two juvenile groups of Atlantic salmon in a large subarctic river in northern Scandinavia: individuals that have migrated from the main stem into small tributaries and those which remain in the main stem. Body size and scale measurements indicated enhanced growth in migratory parr as compared to their resident main stem counterparts. Analysis of adult salmon scale characteristics using maximum likelihood estimators revealed that 20% of the adults had been in the tributaries before the end of their second year of life, and more than 30% more had moved into the tributaries in the third year. Tributary fish matured at a smaller size and younger age (one‐sea‐winter salmon) than those rearing in the main stem which included a higher proportion of multi‐sea‐winter salmon. In addition, when smolt ages and ages at maturity were compared, older female smolts often resulted in smaller spawners and younger smolts, larger spawners. Small female spawners were more likely to survive to become repeat spawners.
The biosynthesis of docosahexaenoic acid [22:6(n‐3)] from linolenic acid in primary hepatocytes isolated from wild northern pike
Authors: Buzzi M. , Henderson R. J. , Sargent J. R.
Published: April 2005

Primary hepatocytes from wild northern pikeEsox luciuswere incubated with radiolabelled linolenic acid ([l‐14C]‐18:3(n‐3)) to assess their ability to synthesize docosahexaenoic acid [22:6(n‐3)]. The distribution of radioactivity in lipid classes and hepatocyte polyunsaturated fatty acids (PUFA) was measured over the time‐course of 24h. The majority of radioactivity from [l‐14C]‐18:3(n‐3) was recovered in hepatocyte triacylglycerols (TAG) and phosphatidylcholine (PC). The levels of radioactivity in TAG and in most of phospholipids, including PC, increased significantly over the incubation period. Radioactivity from [1‐14C]‐18:3(n‐3) was recovered in several hepatocyte PUFA, including 22:6(n‐3), and the Δ6 and Δ5‐desaturation products 18:4(n‐3) and 20:5(n‐3). The presence of radioactivity in C24(n‐3) PUFA may be evidence that the biosynthesis of 22:6(n‐3) in pike proceeds via a pathway independent of Δ4‐desaturation. Analysis by radio gas chromatography revealed that radiolabelled 24:6(n‐3) was present among the desaturation and elongation products of [l‐14C]‐18:3(n‐3). The results establish that, under thein vitroconditions employed, pike hepatocytes are able to convert linolenic acid to 20:5(n‐3) and 22:6(n‐3).
Ovarian weight as an index of fecundity, maturity, and spawning periodicity
Authors: Jons G. D. , Miranda L. E.
Published: April 2005

Ovarian weight and related indices such as gonadosomatic index were used to index fecundity, egg maturity, and spawning season in gizzard shad Dorosoma cepedianum. Individually, in simple regression, fecundity and mean egg volume each accounted for only about 50% of the variability in ovarian weight. Together, in multiple regression, fecundity and mean egg volume accounted for 86% of the variation in ovarian weight. The percentage of the variability in ovarian weight explained by each independent variable, while holding constant the value of the other independent variable (partial coefficient of determination), was 72% for fecundity and 78% for mean egg volume. Thus, ovarian weight of gizzard shad confounded information about fecundity and egg maturity and separately could not index them adequately. Attempts to remove the effect of fecundity, so that ovarian weight could serve as an index of maturity, and to remove the effect of egg size so that ovarian weight could serve as an index of fecundity, were unsuccessful. Nevertheless, seasonal oscillations of ovarian weight served as a crude indicator of population Spawning Season.
Comparative study of reproductive biology in single and multiple‐spawner cyprinid fish. II. Sex steroid and plasma protein phosphorus concentrations
Authors: Rinchard J. , Kestemont P. , Heine R.
Published: April 2005

The dynamics and regulation of oogenesis in single and multiple‐spawner cyprinid fish showing group‐synchronous oocyte development, was investigated in three species from the River Meuse (Belgium): the roach Rutilus rutilus as a single spawner, and the bleak Alburnus alburnus and the white bream Blicca bjoerkna as multiple spawners. This paper compares the seasonal profiles of sex steroids (oestradiol‐17β, testosterone and 17,20β‐dihydroxy‐4‐pregnen‐3‐one) and plasma alkali‐labile protein phosphorus. Different patterns of plasma oestradiol‐17β (E2) and plasma protein phosphorus (PPP) have been observed not only between the single and the multiple spawner fish, but also among the two multiple spawners. In roach, two increases of E2 levels were observed. The first occurred in September after a short gonadal quiescent period, and coincided with the increase of the PPP at the onset of exogenous vitellogenesis. The second took place in spring before the spawning season. The low PPP recorded during that period probably reflected its rapid incorporation by the oocytes. In both multiple spawners, highest values of PPP were recorded just before the spawning season. In white bream, the PPP declined progressively once the differentiation of exogenous vitellogenic oocytes was completed before the onset of the spawning season. In bleak, PPP levels remained high throughout the spawning season and corresponded to a sustained oocyte recruitment during the whole of this period. Regardless of the pattern of oocyte growth recruitment, the E2 concentrations were high in both multiple spawner species during the breeding season. In the three species, testosterone levels remained low regardless of the maturation stage (ranging from 0.6 to 13.4ng ml−1). Except for relatively high concentrations of 17,20βP in roach during final maturation and postspawning stages (20 and 28 ng ml−1, respectively), low levels of this steroid were measured in these cyprinids, and especially in the multiple spawner fish. The role of this progestogen as the maturation inducing Steroid is discussed.
Effects of age, sex and abundance on the bathymetric pattern of American plaice in the southern Gulf of St Lawrence
Authors: Swain D. P. , Morin R.
Published: April 2005

American plaiceHippoglossoides platessoidesdensity in September in the southern Gulf of St Lawrence was strongly related to depth, with peak densities at intermediate depths (70–90 m). Bathymetric pattern was similar for all ages of plaice (3–12 + year) and varied little among years. Densities were highest at similar depths for males and females, but depth distribution tended to be more spread out for females. Depth distribution was not significantly density dependent except for 10‐and 11‐year‐old males and for females aged 12 years and older. In the three significant cases, depth distribution tended to spread out as abundance increased. Water temperature and depth were closely linked in the southern Gulf, but plaice depth preferences could not be attributed solely to temperature selection.
Control of skeletal muscle fibres and adipose cells size in the flesh of rainbow trout
Authors: Fauconneau B. , Andre S. , Chmaitilly J. , Le Bail P.‐Y. , Krieg F. , Kaushik S. J.
Published: April 2005

The distributions of the diameters of skeletal muscle fibres and adipocytes were studied in rainbow trout. The cellularity of perivisceral adipose tissues and subcutaneous ventral and dorsal adipose tissues were characterized more specifically. In these tissues, a population of small adipocytes was distinguishable from larger adipocytes. The same was observed in white muscle. The effects of extrinsic factors (dietary lipid in two different thermal conditions) and intrinsic factors (strains in two different saline conditions, growth hormone) on the long‐term response of the cellularity of both muscle and adipose tissues were studied. The effects of thermal environment were tested on fish fed the same ration and the effects of saline environment on fish fed ad libitum. The mean size of white muscle fibres was relatively unaffected by the different treatments tested: genetic origin and dietary lipid in different environmental conditions. There were significant differences in growth rate due to genetic origin and saline environment. The possible involvement of hyperplasia in response to these different factors is discussed. Growth hormone supplementation enhanced the percentage of small diameter fibres indicating a role of this hormone in the control of muscle hyperplastic growth. The mean size of adipose cells was affected only slightly by the different treatments tested. An increase in adipose cell size with aging and lipid content was observed. The percentage of small adipocytes also increased with aging. Thus, it is proposed that the development of adipose tissues, and thus fat retention, both result from the recruitment of new adipocytes and from the increase in size of existing adipocytes. The hyperplastic process contributed significantly to the differences in fat retention due to different treatments tested (strains, thermal and saline environments). When partially substituting fish oils for corn oils in the diet, a large increase in the ventral adipose cell size was seen indicating a potential negative effect of n‐6 fatty acids on cell proliferation. Growth hormone treatment, on the contrary, induced a decrease in the size of perivisceral adipocytes. Thus, diet and hormonal status affect adipose cells size through two different metabolic pathways: lipogenesis and lipolysis respectively.
The benefits of uniparental versus biparental mouth brooding in Galilee St. Peter's fish
Authors: Balshine‐Earn S.
Published: April 2005

In Galilee St. Peter's fish Sarotherodon galilaeus the care system is naturally labile; biparental, male‐only and female‐only care all exist in one population. This unusual flexibility facilitates comparisons between the forms of care. The costs of parental care were considered in a previous study. Here, the benefits of parental care were quantified by observing wild fish, both held in pond enclosures and free‐swimming in Lake Kinneret, Israel. Parental care was shown to be essential for offspring survival in St. Peter's fish. The reproductive success of parents who shared incubation duties was nearly twice as high as that of parents caring alone. However, per brood (or mouth cavity) reproductive success was 20% higher for uniparental parents. Both sexes were equally capable and efficient in care; when both sexes cared, they each incubated a similar number of eggs and released a similar number of fry. The results are discussed in terms of the relationship between caring Strategies and clutch size.
Respiratory and acid‐base disturbances in rainbow trout blood during exposure to chloramine‐T under hypoxia and hyperoxia
Authors: Powell M. D. , Perry S. F.
Published: April 2005

Rainbow trout Oncorhynchus mykiss were exposed acutely to chloramine‐T at a therapeutic concentration (9mg l−1) under moderately hypoxic (water P o2: l00 mmHg) or hyperoxic (water P o2: 430mmHg) conditions and arterial blood gas tensions (P ao2 and P aco2) and pH were monitored using an extracorporeal circulation. Hypoxia, alone, resulted in an increased ventilation frequency, a decrease in both arterial P co2 and P o2 and an increase in arterial pH. There was no effect of chloramine‐T exposure on the measured variables as compared with pre‐exposure (hypoxia baseline) values. Hyperoxia, alone, resulted in a decrease in ventilation frequency, an increase in arterial P co2 and Po2, and a decrease in arterial pH. Chloramine‐T exposure under these conditions caused a significant increase in ventilation frequency, but no significant effect on arterial blood gases or pH as compared with the hyperoxia baseline values. Despite the increase in ventilation caused by chloramine‐T during hyperoxia, there was no reduction in Pco2 or increase in Po2. Although these results were of little pathological significance, this study suggests that chloramine‐T, although stimulating ventilation, was impairing the diffusion of co2 across the gill probably by the secretion of branchial mucus and enhancing the gill boundary layer.
The response to capture and confinement stress of plasma cortisol, plasma sex steroids and vitellogenic oocytes in the marine teleost, red gurnard
Authors: Clearwater S. J. , Pankhurst N. W.
Published: April 2005

Reproductively active female red gurnard Chelidonichthys kumu were captured on long‐lines, and placed in confinement tanks for 24, 48, 72 and 96 h to examine the effect of capture and confinement on reproductive parameters (experiment I). Plasma cortisol at the time of capture was elevated to levels typical of stressed fish in other species (53–125 ng ml−1). Final plasma cortisol levels in red gurnard confined for any length of time were not significantly different from one another (ranging from 17 to 43 ng ml−1), indicating that fish were chronically stressed when held in captivity for up to 96 h after capture. When initial and final plasma cortisol levels were compared within confinement groups, cortisol decreased significantly after 24 and 96 h of confinement indicating that some acclimation to captivity may have occurred. In contrast, plasma 17β‐estradiol (E2) and testosterone (T) levels decreased significantly to levels comparable to those in post‐spawned fish, after any period of confinement, and remained low throughout the experiment. Another group of fish was captured and confined in the same manner as experiment I but subjected to repeated blood sampling every 24 h, until 96 h post‐capture. In these fish, plasma cortisol levels decreased significantly from 127 ng ml−1 after 24 h confinement and thereafter showed no change (25–45 ng ml−1). Plasma E2 decreased significantly after 72 h of confinement while plasma T showed no change from levels at capture. Increased amounts of follicular atresia were found in vitellogenic oocytes of fish confined for longer periods of time in experiment I, indicating that capture and confinement stress affect reproduction negatively in captive wild fish.
The seaward movement of Atlantic salmon smolts in the Usk estuary, Wales, as inferred from power station catches
Authors: Aprahamian M. W. , Jones G. O.
Published: April 2005

The greatest numbers of Atlantic salmon smolts were caught at Uskmouth power station during the day on the flood tide and the least on an ebbing night tide. Catch rates during the day on an ebb tide and at night on a flood tide represented an intermediate state. The results, together with tracking data, suggest that salmon smolts prefer to migrate seaward through the lower Usk estuary during the night Oncc an ebbing tide.
Comparison of two scanning electron microscope techniques for examining daily growth increments on fish otoliths
Authors: Waldron M. E. , Gerneke D. A.
Published: April 2005

With a secondary detector and a backscatter detector, total primary increment counts on the same otoliths were similar, but more samples could be counted using the backscatter detector and the percentage of unreadable area was consistently lower with this technique.
Shoaling and activity levels in Corydoras
Authors: Paxton C. G. M.
Published: April 2005

A laboratory‐based comparison was made of the activity levels, depth preferences and shoaling behaviour of two morphologically distinct species of congeneric catfish Corydoras pygmaeus and C. ambiacus. Contrary to information in the literature, no strong open‐water preferences were shown by C. pygmaeus. Unlike many shoaling fishes, both species were most active and highest in the water column at twilight, although the cohesiveness of their shoals declined. Unexpectedly, the larger species C. ambiacus formed more cohesive shoals than did C. pygmaeus.
A comparison of univariate and multivariate numerical and graphical techniques for determining inter‐ and intraspecific feeding relationships in estuarine fish
Authors: Marshall S. , Elliott M.
Published: April 2005

The advantages and disadvantages of various numerical and graphical techniques for the analysis of inter‐ and intraspecific feeding relationships of fishes were examined. All methods have been cited in the literature since 1988. The index of preponderance, the resultant index and graphical methods proposed by Costello and Tokeshi were used to illustrate the relative importance of prey species to an individual fish species with no differentiation between size classes. Inter‐ and intraspecific competition and niche overlap were determined from multivariate analysis [the ordination technique, detrended correspondence analysis, cluster analysis by the Bray‐Curtis equation, per cent overlap and two‐way indicator species analysis (TWINSPAN)]. The identity of the prey organisms are not lost in the comparisons, and the value of this is determined through comparison with techniques such as Shannon‐Wiener which obscure these data. The Shannon‐Wiener diversity index was combined with an analysis of ‘evenness’ to refine the technique further to assess niche breadth, as was the Levins index. The study shows that to give an estimate of competition within the community, it is important to assess the data with respect to seasonal and temporal patterns using multivariate analysis.
Oxygen consumption rates of tilapia in fresh water, sea water, and hypersaline sea water
Authors: Iwama G. K. , Takemura A. , Takano K.
Published: April 2005

Whole animal oxygen consumption rates and plasma constituents were determined in the tilapia O. mossambicus, acclimated for 1 month in fresh water, sea water, and 1·6 × sea water. Oxygen consumption rates for the three water salinities were: 177·2 ± 16·86, 78·6 ± 2·32, and 195·4 ± 15·39 mg O2 kg−1 h−1 (means ± 1 s.e.), respectively. Plasma prolactin (tPRL188) concentration was significantly lower in 1·6 × sea water compared to fresh and sea water. There were no significant differences among mean plasma cortisol concentration and lysozyme activity. Ventilation was significantly higher in fish in sea water compared to the fish in fresh and 1·6 × sea water. The lowest oxygen consumption rates were found in fish acclimated to sea water. That salinity is probably closest to the brackish waters from which they were captured in the wild, and this agreement likely reflects the selection for optimal morphological and physiological characteristics to live in that environment.
The feeding response of diploid and triploid Atlantic salmon and brook trout
Authors: O'Keefe R. A. , Benfey T. J.
Published: April 2005

Pair and group experiments were conducted to determine whether differences exist in feeding success between juvenile diploid and triploid salmonids in a competitive situation. In the pair experiments, 22 pairs (one diploid and one triploid) of size‐matched Quebec‐strain brook trout Salvelinus fontinalis (7·2–46·3 g) were fed an unlimited number of pellets three times a day for 5 days. Dominance was assigned to the fish which ate the most pellets within each pair. In the group experiments, groups of three diploid and three triploid size‐matched fish were fed a restricted ration three times a day for 5 days. Hierarchical rank within the group was assigned based on the number of pellets consumed by each fish. The group experiment was repeated 10 times with Atlantic salmon Salmo salar (5·1–62·7 g), Quebec‐strain brook trout (11·8‐110·8 g), and large UNB‐strain brook trout (18·2–33·0 g), and 12 times with smaller UNB‐strain brook trout (0·6–2·0 g). A statistically significant difference in rank between ploidies was found only for the smaller UNB‐strain brook trout in the group experiments, with diploids dominant over triploids. This suggests that there may be a difference in competitive feeding success between diploid and triploid brook trout early in development, but that this difference diminishes as the fish grow.
Infection of Salmincola edwardsii (Copepoda: Lernaeopodidae) in an age‐structured population of Arctic charr—a long‐term study
Authors: Amundsen P.‐A. , Kristoffersen R. , Knudsen R. , Klemetsen A.
Published: April 2005

The parasite‐host relationships between Salmincola edwardsii (Copepoda: Lernaeopodidae) and Arctic charr Salvelinus alpinus were studied in lake Takvatn, northern Norway, over an 8‐year period. The infection levels were modest, with an overall prevalence of 16·1% and an abundance of 0·5 parasites fish−1. Most of the infected fish (54·1%) had only one parasite attached, whilst only 4·3% had more than 10. In general, parasite infection increased with increasing age, and hence size of the fish. The increase was modest up to age 7, whereafter a steep increment in parasite burdens occurred. Within each age class there was little effect of either fish size, gender, maturation or choice of macrohabitat upon parasite abundance. There was also little year‐to‐year variation in infection of the different age classes, indicating a high degree of stability of the parasite‐host interactions in this system. The infection levels exhibited seasonal changes, being lowest in early summer and highest during winter. The infection rates seemed to be related to seasonal and ontogenetic habitat shifts of the charr.
Annulus formation on scales and seasonal growth of the Central Amazonian anostomid Schizodon fasciatus
Authors: Fabré N. N. , Saint‐Paul U.
Published: April 2005

Annulus formation on the scales of the Central Amazonian anastomid fish Schizodon fasciatus was studied with respect to periodic variations in growth rates caused by seasonal inundation or associated biological processes. Monthly samples from fish markets were analysed with regard to marginal scale increment, feeding index, condition factor, gonadosomatic index, and body cavity fat content. There was a significant variation in all indices which was related to seasonal change in water level. Fat storage was related to energy requirements especially during gonad maturation. Fastest growth was observed during the period of falling water level. The formation of scale growth marks corresponded to the period of gonad maturation between January and February. The results indicate the formation of only one single growth mark on scales per year.
Control of bloom in a tropical lake: grazing efficiency of some herbivorous fishes
Authors: Datta (Saha) S. , Jana B. B.
Published: April 2005

Using a limnocorral study, Microcystis grazing by silver carp, bighead and tilapia was examined in an eutrophic shallow lake permanently infested with a Microcystis bloom. Twelve fingerlings of each fish species were introduced into the limnocorrals placed in the lake, in triplicate, and their grazing effects were examined over a period until the limnocorral bloom declined substantially and remained unchanged. Introduction of fish, regardless of species, into the limnocorrals resulted in sharp reductions (60–93%) of the initial Microcystis population on day 3 or 7. Maximum gross and net clearance of Microcystis were by silver carp followed by bighead and tilapia. Short‐term high retention of Microcystis by tilapia indicated that the clearance effect did not last long due to a high rate of defaecation of undigested Microcystis. Nearly 6–180% nutrient enrichment of the limnocorrals was attributable to the defaecation of test fishes suggesting their ichthyoeutrophication potentials, which were in the following order: tilapia>bighead>silver carp. It is concluded that silver carp is most suitable for clearing Microcystis in the lake because of its minimal ichthyoeutrophication effect.
Unusual glycoconjugates in the oesophagus of a tilapine polyhybrid
Authors: Scocco P. , Accili D. , Menghi G. , Ceccarelli P.
Published: April 2005

The aim of this work is to elucidate the glycoconjugate composition of the secretory products of the oesophageal mucous cells in a tilapine polyhybrid. Lectin histochemistry gave evidence of the presence of β‐galactose, α‐N‐acetylgalactosamine and sialic acid residues in the terminal position. The majority of sialic acid belongs to short side chains; a few sialic acid residues are acetylated at the C7 and/or C8 and/or C9 level. The heterogeneity of the carbohydrate chains may mask potential receptor sites for micro‐organisms and hamper the formation of multiple bonds.
Prey selection by experienced and naive juvenile Atlantic salmon
Authors: Reiriz L. , Nicieza A. G. , Brañta F.
Published: April 2005

Both in foraging groups and in a sequential prey encounter context, learning had a visible effect on the pattern of selection for three live prey types (Ecdyonurus larvae, Hydropsyche larvae, and Gammarus) by juvenile Atlantic salmon Salmo salar. Compared to wild‐caught fish, naive, hatchery‐reared fish that had not been exposed to natural prey ate Hydropsyche larvae in a remarkably low proportion, and consumed a higher proportion of Gammarus. Ecdyonurus experienced a high and rather steady predation rate across the experience gradient, but after a short period of experience with live prey the consumption rate for Hydropsyche increased drastically, and that of Gammarus decreased, matching the selection pattern exhibited by wild fish. Individual fish offered prey in a sequential encounter context increased consumption rates of all the prey types as they gained experience, but the improvement was higher for the prey that were less consumed initially. Fish became more selective as they approached satiation, conforming to the prediction of optimal foraging theory that higher predator's energy requirements, as well as low food availability, result in reduced selectivity. The results also suggest that fish from distinct populations can differ in the degree of diet selectivity according to their energetic requirements for growth. The fast learning response of Atlantic salmon parr towards novel prey probably allows fish to maintain a high foraging efficiency when faced with frequent changes in the availability of different prey types.
Genetic structuring among Alaskan Pacific herring populations identified using microsatellite variation
Authors: O'Connell M. , Dillon M. C. , Wright J. M. , Bentzen P. , Merkouris S. , Seeb J.
Published: April 2005

Five highly variable microsatellite loci were used to investigate population structuring in Pacific herring Clupea pallasi collected from Kodiak Island, two sites in the Bering Sea and four sites within Prince William Sound, Alaska. All loci revealed high levels of variability with heterozygosity estimates ranging from 86 to 97% (mean heterozygosity: 89%). The variation was structured significantly among sites suggesting that the samples investigated were genetically distinct from each other. Genetic divergence was greatest between populations from the Bering Sea and those from Prince William Sound. The Kodiak Island and Point Chalmers samples appeared to be distinct from the Prince William Sound and Bering Sea populations. The observed genetic distance relationships among samples could be explained largely in terms of geographical separation.
Otolith growth and age estimation in the European hake
Authors: Morales‐Nin B. , Tores G. J. , Lombarte A. , Recasens L.
Published: April 2005

The internal sulcal rings in Merluccius merluccius otoliths cannot be considered as annuli. In the absence of a strong seasonal Zeitgeber, hake otoliths in the Mediterranean did not lay down an interpretable ring pattern that would be useful for age determination. A total of 484 sagittal otoliths from specimens ranging between 6 and 94 cm L T was studied in monthly samples from the Gulf of Lions in 1989–1990. Transverse, burnt otolith sections was analysed with an image analysis system using enhanced and filtered images and using a fast Fourier transform (FFT) function to avoid subjectivity in ring interpretation. The otolith radius‐fish length relationship showed allometric growth and sexual dimorphism. The ring pattern was consistent for the sulcal rings in both sexes. Changes in the marginal increment showed the formation of multiple sulcal rings, of both environmental and physiological origin. The ring pattern depended on the sex and sexual activity.
A study of trophic niche partitioning between larval populations of reproductively isolated whitefish (Coregonussp.) ecotypes
Authors: Chouinard A. , Bernatchez L.
Published: April 2005

The abundance, spatio‐temporal distribution, and feeding of larvae were compared from two reproductively isolated dwarf and normal ecotypes of whitefish (Coregonussp.) to test the hypothesis that larval ecotypes should reduce competition by using different resources. Contrary to a priori expectations, trophic niche partitioning between larval populations was much less pronounced than previously reported for the adult stages of fish ecotypes, presumably due to the lack of competition acting at this stage, and related to non‐limiting food resources. Because this study was conducted in a single year and a single lake, we cannot however, strictly rule out the possibility that resource‐based competition and resulting niche partitioning may occur at the larval stage in these species complexes. Nevertheless, this suggests for the first time, that resource‐based selection at the larval stage may be relatively unimportant compared to that occurring at older life‐history stages in driving the divergence and the development of reproductive isolation in sympatric fish ecotypes.
Behavioural responses of glass eels of Anguilla anguilla to non‐protein amino acids
Authors: Sola C. , Tongiorgi P.
Published: April 2005

Glass eels reacted chemotactically towards five non‐protein constitutional amino acids, D‐glutamine, D‐asparagine, D‐glutamic acid, D‐alanine and β‐alanine, dissolved in fresh water or salt water, with behavioural thresholds ranging from 10‐9 M for the most effective (D‐ and β;‐alanine) to 10‐7 M for the other three. With the exception of D‐asparagine in fresh water and D‐alanine at concentrations ≥10‐7 M, these amino acids were strong attractants. The results are compared with previous findings on the respective L‐isomers. The non‐protein amino acids may influence behaviour in the search for food and the recognition of conspecifics.
Age, growth, and reproductive biology of the blackbelly rosefish from the Carolinas, U.S.A.
Authors: White D. B. , Wyanski D. M. , Sedberry G. R.
Published: April 2005

Otoliths and gonads of blackbelly rosefish Helicolenus dactylopterus dactylopterus were collected from the commercial fishery off the Carolinas in 1994–1997. Opaque bands on transverse sections of otoliths were determined to be annuli by analysis of marginal increments. Opaque zone formation occurs between July and January. Ages ranged from 7 to 30 years. Blackbelly rosefish have intraovarian gestation. Fertilization is internal, as free spermatozoa were found primarily in resting ovaries from July through early December with peak occurrence in September through November. There was a delay of 1–3 months before fertilization, as oocyte development did not begin until December. Occurrence during January through April of early‐celled embryos, the most advanced stage observed, and postovulatory follicles indicated that oocyte development was rapid. Egg development occurs in a clear gelatinous matrix secreted into the ovarian cavity. The reproductive mode is a zygoparous form of oviparity, intermediate between oviparity and viviparity. Population sex ratio departed markedly from 1: 1 for most length intervals. Males were more abundant at lengths >250 mm LT and the overall male: female ratio was 1 : 0·60.
Serine proteinase inhibitors of seminal plasma of teleost fish: distribution of activity, electrophoretic profiles and relation to proteinase inhibitors of blood
Authors: Ciereszko A. , Piros B. , Dabrowski K. , Kucharczyk D. , ŁUczyński M. J. , Dobosz S. , Glogowski J.
Published: April 2005

Anti‐proteinase activity has been found in seminal plasma of eight teleost fish species: brown trout, rainbow trout, brook trout, lake whitefish, bream, northern pike, Danube salmon and burbot. This activity correlated with seminal plasma protein and sperm concentrations. Using a mammalian (bovine) trypsin for detecting proteinase inhibitors it was found for the first time that there are species‐specific electrophoretic profiles of anti‐proteinase activity. One to three bands could be identified by this method. However, additional proteinase inhibitors could be identified by using fish (cod) trypsin. These inhibitors were detected in seminal plasma of salmonids and coregonids and have a slow migration rate. Fast‐migrating proteinase inhibitors were present in rainbow, brown and brook trout, northern pike, whitefish and burbot. These inhibitors could be detected in brook and brown trout by using either trypsins. However, they were detected only with bovine trypsin in rainbow trout, northern pike, whitefish and burbot. These results suggest that multiple forms of serine proteinase inhibitors exist in seminal plasma of teleost fish and they differ in their affinity toward serine proteinases. Seminal plasma serine proteinase inhibitors of rainbow trout migrated during electrophoresis similarly to blood plasma proteinase inhibitors, and suggests that the two inhibitors may be similar or the same. Anti‐proteinase specific activity was similar in blood and seminal plasma. Proteinase inhibitors of fish seminal plasma seem to be an important part of sperm physiology, possibly related to protection of spermatozoa. Staining for detection of serine proteinase inhibitors also allowed detection of presence of nonspecific esterase in seminal plasma of most species.
Body composition and energy allocation in life‐history stages of brown trout
Authors: Jonsson N. , Jonsson B.
Published: April 2005

Energy contents of immature parr and smolts, and mature resident and anadromous brown troutSalmo truttasampled from a small stream in southern Norway were estimated from lipid, protein and carbohydrate concentrations. In immatures the lipid concentrations were highest in parr in the autumn. Mean lipid concentrations increased significantly with age in parr sampled in autumn (1·3% in age 0+ to 3·4% in age 3+), whereas they did not in smolts. The lipid concentrations of parr in spring were not significantly different from those of similarly aged smolts. By contrast, the relative water content (%) decreased with age in parr in the autumn and increased with age in smolts, mean values being slightly higher in smolts (78%) than in parr (77%). Protein and carbohydrate concentrations did not vary with age in the immature fish, mean protein concentrations being 18·0, 17·5 and 16·8% in parr in the autumn and spring, and in smolts, respectively. In residents, the concentrations of lipids were lower and of water higher, in age group 1 than in older fish, whereas there was no significant variation with age amongst anadromous trout. The energy concentration of 2+ smolts (349 kJ 100 g‐1) was similar to that of 0+ parr in the autumn. Mean somatic energy density in autumn was 1·1 times higher in freshwater residents than in parr at age 1+ (407 and 387 kJ 100 g‐1) and marginally different at age 2+ (462 and 426 kJ 100 g‐1, respectively). The energy contents per unit mass of residents were 1·3–1·6 times that of similar aged smolts. Mean somatic energy density of anadromous trout (504 kJ 100 g‐1) was higher than that of residents (455 kJ 100 g‐1). Somatic energy, lipid and protein concentrations were correlated highly with water contents of all life stages, age and sex groups.
Parasitism, oddity and the mechanism of shoal choice
Authors: Barber I. , Downey L. C. , Braithwaite V. A.
Published: April 2005

When choosing between shoals differing in Schistocephalus solidus infection status, uninfected test sticklebacks Gasterosteus aculeatus showed a preference for joining uninfected conspecifics when shoal sizes were equal, but reversed this preference when the relative size of the infected shoal was increased by a factor of 3. When given a choice between a shoal composed of size‐matched minnows Phoxinus phoxinus and a shoal composed of the same number of all uninfected or all S. solidus‐infected sticklebacks, test fish always preferred the sticklebacks, regardless of their infection status, over the minnow shoal. These observations suggest that species, parasite status and shoal size are all of importance when fish decide which shoal to join.
Taxonomy of the deep‐sea eel genus, Histiobranchus (Synaphobranchidae, Anguilliformes), with notes on the ecology of H. bathybius in the eastern North Atlantic
Authors: Karmovskaya E. S. , Merrett N. R.
Published: April 2005

The eel genus Histiobranchus Gill occurs benthopelagically over the continental rise and abyss of the World Ocean, primarily beneath temperate and subpolar surface waters. Its generic status within the subfamily Synaphobranchinae is confirmed by comparison of the structure and topography of its cephalic sensory system and skeletal features with Synaphobranchus. At least three species of Histiobranchus are recognized: H. bathybius (panoceanic), H. bruuni (Tasman Sea and waters south‐east of New Zealand) and H. australis (two geographical forms; South Atlantic and south‐western Indian Ocean, and South Indo‐West Pacific Oceans). Collections totalling 319 specimens of H. bathybius from the eastern North Atlantic (1790–5440 m depth) yielded a size range of 99–1370 mm total length (LT), with no apparent sexual dimorphism. Length–frequency distributions indicate a mode of juvenile fish at around 100–200 mm LT and a further two around 600–700 and 1300–1400 mm LT among adults. Generally smaller fish occur in shallower regions, although the size range is broad over the whole depth range. No apparent trend occurs in the size distribution with latitude over the range 17–54) N. Females outnumber males (1 male : 1·7 females) and both sexes are largely distinguishable from 300 mm LT. Ripening eggs occur in females from both adult length modes, with running ripe and spent females of very different size indicating iteroparity.
Postspawning movements and habitat selection of dace in the River Frome, Dorset, southern England
Authors: Clough S. , Garner P. , Deans D. , Ladle M.
Published: April 2005

Recently spent adult dace Leuciscus leuciscus were captured from a known spawning site, radio‐tagged and released. Post‐release movements were monitored, and the habitat characteristics of the areas selected were recorded. Visual observations and electrofishing showed that all radio‐tagged fish were associated with other, untagged, adult dace. After spawning, dace occupied slow‐flowing shaded sites out of the main river channel. Within these areas, the fish were situated in the deepest and slowest‐flowing positions available. Possible reasons for the observed postspawning behaviour and habitat selection are discussed. ? 1998 The Fisheries Society of the British Isles
Salinity effects on oxygen consumption, gill Na+, K+‐ATPase and ion regulation in juvenile coho salmon
Authors: Morgan J. D. , Iwama G. K.
Published: April 2005

The metabolic response of juvenile coho salmon Oncorhynchus kisutch to different salinities was examined, using whole‐animal oxygen consumption rates and gill Na+, K+‐ATPase activities as indicators of osmoregulatory energetics. Coho salmon smolts were acclimated to fresh water (FW), isosmotic salinity (ISO, 10‰) and sea water (SW, 28‰) and were sampled for up to 6 weeks for plasma levels of cortisol, glucose and ions (Na+, K+, Cl−), gill Na+, K+‐ATPase activity and oxygen consumption rates. Following an initial adjustment period, plasma constituents in SW fish returned to near‐FW values, indicating that the fish were acclimated to SW by day 21. Gill Na+, K+‐ATPase activities on days 21 and 42 were lowest in ISO, higher in FW and highest in SW. This result is consistent with the idea that less energy would be required to maintain ion balance in an isosmotic environment, where the ionic gradients between extracellular fluid and water would be minimal. Oxygen consumption rates of swimming fish (1 body length s−1), however, did not differ significantly between the three test salinities after 6 weeks. The results of this study suggest that the metabolic response of juvenile salmonids to changes in salinity is dependent on life‐history stage (e.g. fry v. smolt), and that oxygen consumption rates do not necessarily reflect osmoregulatory costs.
The RAPD technique fails to detect a male‐specific genetic marker in Atlantic salmon
Authors: McGowan C. , Davidson W. S.
Published: April 2005

The RAPD technique failed to detect a male‐specific genetic marker in Atlantic salmon Salmo salar.