bluuebunny/crossref_metadata_2025 huggingface dataset:
Feeding and movement of Anguilla australis and A. reinhardtii in Macleods Morass, Victoria, Australia
Authors: Beumer J. P.
Published: August 2010

Feeding and movement of Anguitta australis Richardson, and A. reinhardtii Steindachner, were studied in Macleods Morass, Gippsland, Victoria from July 1975 to March 1977. Stomach fullness varied seasonally. Both species ingested a wide range of items with teleosts and insects forming the major group for A. australis and teleosts the major group for A. reinhardtii, which fed on a narrower range of items. No relationship between size of items ingested and size of eel was evident. Kendall rank correlation coefficients indicate that both intraspecific and interspecific differences in diets due to seasonal and size variations were usually insignificant.

Tagged eels were recaptured at the overall rate of 18·5 %; of 1051 eels released, a total of 194 eels was recaptured. Maximum linear distance travelled by two eels was 3715 m while maximum days at liberty was 643 days. Home range was in the order of 400m. No relationship between length of a tagged individual and days liberty or with distance moved was evident. Movement was closely related to fluctuations of water temperature with peaks being associated with feeding in the littoral zone of the Morass.
Young fish distribution in backwaters and main‐channel borders of the Kanawha River, West Virginia
Authors: Scott M. T. , Nielsen L. A.
Published: August 2010

Fish in the Kanawha River were collected with a 0.5‐m plankton net in main‐channel borders and in open areas of backwaters and with a 1‐m2 enclosed dropbox in shallow backwater habitats. Larval emerald shiners, Notropis atherinoides, were twice as dense, and gizzard shad, Dorosoma cepedianum, 2.5 times as dense in main‐channel borders as in backwaters; larval Lepomis spp. were 20 times as dense in backwaters as in main‐channel borders. Smaller Lepomis larvae used open‐water backwater areas primarily; larger larvae migrated to vegetated backwater habitats later in the summer. Backwaters appear crucial for the maintenance of nest‐building fish species in temperate rivers, just as floodplains are necessary for the maintenance of high species diversity in tropical rivers.
Subtleties and episodes in the early life of fishes
Authors: Houde E. D.
Published: August 2010

Fluctuations in the abundance of fishes may be caused by episodic mortalities or by more subtle variability in the daily growth and mortality rates of eggs and larvae. Survival response surfaces are used to illustrate the relative effects of episodic and subtle mortality during early life. It is the subtle variability associated with small changes in growth or mortality rates that may exert the greater effect on recruitment. Massive advective losses of eggs or larvae, failed egg production, and acute contaminant mortalities are examples of episodic events that may impact recruitment significantly but which need not be catastrophic. Stabilization of recruitments through density‐dependent growth rate variability in early life is demonstrated to be potentially important. Whether this mechanism actually is important in the sea remains to be determined.
Comparative study of early‐life survival variability of herring Clupea harengus, in the north‐eastern Atlantic
Authors: Heath M. , Richardson† K.
Published: August 2010

Variation in the survival of herring between the egg stage and the age of recruitment to the spawning population has been examined for seven Atlantic herring populations in northern European waters. The sources of the variation have been partitioned between density‐dependent and density‐independent factors. The magnitude of the density‐independent component was found to be related to the scale of the processes controlling the dispersion and distribution of larvae from the various populations. We conclude that the spawning strategies of some populations are adapted to oceanographic conditions to maximize the probability of a particular larval transport pattern, although no single model could account for all spawning strategies.
Identifying the spatial scale of density‐dependent interaction of predators with schooling fish in the southern Labrador Current
Authors: Schneider D. C.
Published: August 2010

Previous work along the coast of Newfoundland has shown that aggregative responses of puffins, Fraiercula arctica, and common guillemots, Uria aalge, to schooling fish, primarily capelin, Mallotus villosus, occur at spatial scales of 2‐6 km. The present work tests the hypothesis that coastal upwelling results in aggregation of capelin at this scale, and that the scale of interaction with predators can be predicted from wind‐driven coastal upwelling. An observational experiment in 1987 showed that a relatively simple physical model could be used to predict the spatial scale of upwelling, that schooling fish aggregate at this scale after upwelling, that aggregation of schooling fish at the scale of upwelling decays as upwelling relaxes, and that the spatial association of puffins and guillemots with schooling fish reaches a maximum at this scale. These results suggest that relatively simple physical theory can, in some cases, be used to identify the spatial scale of interaction of predators with prey.
Evidence for density‐dependent growth in North Sea gadoids
Authors: Bromley P. J.
Published: August 2010

The classical view on density‐dependent growth is that an increase in population density heightens intraspecific competition for food, leading to reduced food intake and depressed growth. This paper summarizes the analysis of English Groundfish Survey, International Young Fish Survey and ICES Roundfish Working Group data for evidence of density‐dependent growth of I‐ and II‐group cod, haddock and whiting in the North Sea.

Within Roundfish areas there was a negative relationship between growth and density in some instances, but it was small. However, there were persistent differences in both growth rate and density between Roundfish areas. In all cases, except for I‐group cod, there appeared to be a tendency for fish in low‐density areas to be larger than fish in high‐density areas; this might be due to feeding competition but other explanations are possible. The results urge caution in interpreting commercial catch data for evidence of density‐dependent growth, since changes in fishing effort in particular areas could significantly bias the conclusions.

There was evidence of enhanced survival of small fish in good year‐classes; this would depress the mean size at age, thereby mimicking the effects of density‐dependent growth.
Field mortality estimates of anchovy larvae, Engraulis encrasicolus, in the western Mediterranean
Authors: Palomera I. , Lleonart J.
Published: August 2010

Eggs and larvae of anchovy were obtained from plankton collections made along the Catalan coast (north‐western Mediterranean) from 1983 to 1985 in order to determine spawning seasons and areas and other aspects of its life history. Previous studies have shown the existence of two main spawning areas, to the north and south of the Catalan coast, respectively. The northern one is characterized by a shorter spawning period related with the thermal cycle.

Mortality rates of larvae aged 4.9‐15 days were calculated from the peak spawning month (June) of the three years, separately by spawning areas. Data on abundance by length classes were adjusted for escape and net avoidance and for duration of growth through a size class as derived from otolith readings. Mortality rates ranged from 0.17 to 0.58. Mortality was higher in 1983 than in 1984 and 1985, coinciding with a high production of anchovy eggs in that year. Mortality at the northern spawning area was lower than at the southern one.
Long‐term variations of biotic and abiotic conditions in the ecosystem of the Barents Sea
Authors: Borisov V. M. , Elizarov A. A.
Published: August 2010

Synchronism of year‐class strength was noted for the majority of commercial fish in the Barents Sea. The reason for this is probably connected with a common factor, namely the intensity of water inflow which influences spawning efficiency, zooplankton food production, fish larval drift to the feeding grounds, and consequent survival of juvenile fish. Consequently, the established regular relationships of hydrological and weather processes in the ecosystem can serve as basis for long‐term fishing forecasts. The overall pattern of the Barents Sea water circulation, long‐term climatic changes in this region, and their effect on the fish stock reproduction are considered, using Arctic cod as an example.
The estimation of natural mortality in Irish Sea plaice, Pleuronectes platessa L., using tagging methods
Authors: Siddeek M. S. M.
Published: August 2010

This paper addresses the question as to whether natural mortality (M) can be estimated reliably in a heavily exploited fish population. Several methods, including a new opitimization technique based on Pope's cohort model, were used to estimate M from a large series of tagging experiments carried out on the Irish Sea plaice off North Wales and Ireland during the early 1960s, and off North Wales during 1979 and 1980. The assumptions underlying the new method were: (i) that the product of initial survival after tagging and the reporting rate of recaptures (SB) was constant for all experiments, and (ii) that the number of recoveries were log‐normally distributed. Simulations showed that the estimator was robust to errors in input data. The SB values were low (0.37) but were more precise than the estimates of natural mortality for both sexes. The annual M values were 0.17 and 0.11 with standard errors 0.06 and 0.08 for males and females, respectively. The estimate of M for mature males was low, indicating a low M for older fish. The less precise estimate of M for females because of the inadequate dataset, and the higher M values obtained by applying traditional methods to the same dataset, indicated that a value of 0.2 is more appropriate for both sexes. Suggestions are made for designing and analysing tagging experiments to estimate M.
Key fish species, northern fur seals, Callorhinus ursinus, and fisheries interactions involving walleye pollock, Theragra chalcogramma, in the eastern Bering Sea
Authors: Livingston P. A.
Published: August 2010

The recent decline of the northern fur seal population breeding on the Pribilof Islands has not yet been explained. This study estimates the amounts and sizes of walleye pollock (the fur seal's main prey) removed by predatory fish, fur seals and commercial fisheries in the main fur seal feeding area in the eastern Bering Sea during summer 1985. Fur seals relied primarily on age‐1 pollock during 1985, while predatory fish consumed pollock mainly of ages 0‐1. The fishery took pollock older than age‐3. This indicated no direct effect of fishery removal on fur seal prey abundance, at least during the study period. In the short term, the 1985 pollock fishery may have indirectly affected fur seal prey abundance in a positive manner by removing adult pollock that compete with fur seals for age‐1 pollock.
Modelling regional differences in ‘sealworm’, Pseudoterranova decipiens (Nematoda, Ascaridoidea), infections in some North Atlantic cod, Gadus morhua, stocks
Authors: des Clers S.
Published: August 2010

The ascaridoid nematode Pseudoterranova decipiens has a complex life‐cycle. Adult worms reproduce in the stomach of grey seals, Halichoerus grypus, and other pinnipeds, and the larvae are found encysted in the musculature of Atlantic cod, a common host. An increase in infection levels in Canadian, Icelandic and Norwegian cod stocks over the last decade has been attributed to recent increases in seal population numbers. A simple model is proposed for the accumulation of larval parasites in the fish through its food. The model describes how regional differences in fish growth can also explain some differences in infection levels.
Interspecific relationships between emerging Atlantic salmon, Salmo salar, and coho salmon, Oncorhynchus kisutch, juveniles
Authors: Beall E. , Heland M. , Marty C.
Published: August 2010

Interspecific relationships between Atlantic salmon and coho salmon were studied at early life stages in laboratory and semi‐natural stream channels. During emergence, the survival and dispersal patterns were similar for the two species in single or mixed populations. Survival of Atlantic salmon fry was reduced in the presence of older coho fry. However, no predation was observed. Microdistribution differed between the two species, with Atlantic salmon fry more numerous in riffles when coho were present.

Coho juveniles had a pelagic and gregarious distribution, in contrast to the benthic behaviour of the Atlantic salmon. In laboratory streams, Atlantic salmon fry moved out or adopted a subordinate cryptic behaviour which allowed them to escape predation while negatively affecting their growth.
Long‐term changes in growth and age at maturity of mackerel, Scomber scombrus L., from the North Sea
Authors: Agnalt A.‐L.
Published: August 2010

Mean length and mean weight at age of Atlantic mackerel in the North Sea increased significantly between 1960 and 1979, then, decreased markedly during the 1980s. In contrast, median age at maturity decreased (c. 1‐1.5 years) from 1960. Median length at maturity remained stable until the 1980s, when it declined sharply. The significance of these changes is discussed in relation to variation in sea temperature, food availability and stock size. It is speculated that the changes during the 1980s resulted from immigration of western stock mackerel.
Hyperplasia and hypertrophy in the growth of skeletal muscle in juvenile Atlantic salmon, Salmo salar L.
Authors: Higgins P. J. , Thorpe J. E.
Published: August 2010

Both red and white muscle fibre numbers in juvenile Atlantic salmon increased gradually with fish length throughout the freshwater growth period. Mean fibre area increased as fish grew to 6.5 cm f.l., but thereafter was unrelated to fish length. Hyperplasia was most obvious when fish were growing fastest, and was the dominant growth process in fish over 6.5 cm f.l. Hypertrophy was most important when growth was slow, as in autumn and winter.

Mean white fibre area was significantly smaller in deep muscle than at medial and superficial sites. Total cross‐sectional area of red, white and total trunk muscle increased with fish length. The ratio of red: white cross‐sectional area increased with fish length to a plateau at about 10% after 6.5 cm f.l.
The histochemistry of muscle in juvenile Atlantic salmon, Salmo solar L.
Authors: Higgins P. J.
Published: August 2010

In fry, 1‐ and 2‐year old juvenile Atlantic salmon, relatively small superficial red muscle fibres staining well for glycogen and succinic dehydrogenase (SDH) but with little myofibrillar ATPase, were evident on either side of the lateral line, in June. Well differentiated relatively large white fibres contained lower concentrations of glycogen than the red fibres, higher ATPase and no SDH, except traces in the larger 1‐ and 2‐year‐olds. Intermediate size pink fibres, which were also intermediate between red and white fibres in their staining properties, occurred in a thin diffuse layer along the red‐white boundary, thickest at the apex near the vertebral column, and most evident in the younger fish.
Otolith increment widths and somatic growth rate: the presence of a time‐lag
Authors: Molony B. W. , Choat J. H.
Published: August 2010

Populations of the estuarine glass fish, Ambassis vachelli Richardson, were used to study the relationship between somatic growth and widths of daily increments in the sagittal otoliths. Variations in the somatic growth of A. vachelli were induced by a series of experimental feeding regimes which included feeding to satiation with two food sources and a starvation treatment. After 33 days of exposure to the experimental feeding regimes significant differences in the mean wet weight of individuals amongst the feeding treatments were recorded. Fishes subject to a starvation treatment showed a significant reduction in wet weight compared to the pretreatment population and the two experimental feeding regimes. No changes in lengths of fishes were recorded.

Validation techniques revealed that daily increments were laid down in the sagittal and asteriscal otoliths. Estimates of ring widths from samples of sagittal otoliths revealed significant treatment effects. The increments of fishes from the starvation treatment showed a significant decline in mean increment width relative to the feeding treatments. This difference was detected only after a 15 day period of experimental feeding. It is suggested that the gradual decline in increment width reflects the exhaustion of readily mobilized energy reserves.
Improved methods for working with fish chromosomes with a review of metaphase chromosome banding
Authors: Gold J. R. , Li Y. C. , Shipley N. S. , Powers P. K.
Published: August 2010

Improved methods for obtaining, preparing, and staining fish chromosomes are described. Included are procedures for resolving serial or G‐type bands. A brief review of various metaphase banding procedures and their use in fishes is also presented.
Lunar synchronization of spawning in cichlid fishes of the tribe Lamprologini in Lake Tanganyika
Authors: Nakai K. , Yanagisawa Y. , Sato T. , Niimura Y. , Gashagaza M. M.
Published: August 2010

Lunar synchronization of spawning was investigated for eight substrate brooding cichlid fishes belonging to the tribe Lamprologini. Their spawning activities all peaked during the second quarter of the lunar cycle. Comparison between their breeding styles and the degrees of spawning synchronization suggested that the nocturnal guarding‐efficiency of eggs, especially exposed ones, is improved by the maximal amount of moonlight during full moon and, in species whose young leave the breeding sites about 2 weeks after spawning, the survival of dispersing young is enhanced by the darkness of moonless nights.
Aspects of the ecology of bream, Abramis brama (L.), in a gravel pit lake and the effects of reducing the population density
Authors: Wright R. M.
Published: August 2010

The growth of bream, Abrumis brumu (L.), in a gravel pit lake was considered to be good in 1982/1983 (Lx=663cm, K=0.105). Theadult breampopulationwasdominated by the 1973and 1976 year‐classes. These year classes still formed most of the spawning population in 1987, but had grown very little (<2 cm) in the previous 5 years. In November 1987, 158 kg ha−1 of bream were removed from this lake and in I988 the remaining bream population showed an increase in growth (mean length by 2.7 cm and mean weight by 0.5 kg) and condition (1.87 in 1987 to 2.09 in 1988) in one growing season. This additional growth of an ageing stunted bream population is considered to be the result of an increased food supply after reducing the fish density.
The osmoregulatory ability of the invasive species sunbleak Leucaspius delineatus and topmouth gudgeon Pseudorasbora parva at elevated salinities, and their likely dispersal via brackish waters
Authors: Scott D. M. , Wilson R. W. , Brown J. A.
Published: August 2010

The European invasive species sunbleak Leucaspius delineatus and topmouth gudgeon Pseudorasbora parva, previously thought to be stenohaline freshwater fishes, were shown to tolerate salinities of 10·8 and 13·7 for up to 4 days. The increased plasma osmolality and ion concentrations, and decreased body water content, however, indicated that they are unable to hypo‐osmoregulate. Therefore there is limited potential for these species to disperse into new river systems via brackish waters with a salinity >13·7.
Influence of visual conditions on foraging and growth of juvenile fishes with dissimilar sensory physiology
Authors: Ljunggren L. , Sandström A.
Published: August 2010

The influence of turbidity on foraging and growth of young‐of‐the‐year (YOY) of two percid species with relatively dissimilar sensory physiology, perch Perca fluviatilis and pikeperch Sander lucioperca was tested. A littoral mysid, Neomysis integer, was used as prey. Functional response was investigated indoors at two levels of turbidity, 3 NTU (clear) and 25 NTU (turbid). Growth and consumption rate were studied both during day and night in outdoor experiments at similar turbidity levels. Pikeperch were not affected by turbid conditions in either of the experiments. Foraging of perch, on the other hand, was significantly negatively affected by higher turbidity in the functional response experiments and during the night‐time in the outdoor experiments. As opposed to pikeperch, consumption rates of perch decreased markedly during nights. Perch also grew more slowly in the treatments with turbid water. The dissimilar reactions of the two species indicate that sensory physiological adaptations and foraging behaviour are important factors that partly can explain disparate reactions of YOY fishes to the level of turbidity.
Recovery from acute, chronic and transport stress in the pot‐bellied seahorse Hippocampus abdominalis
Authors: Wright K. A. , Woods C. M. C. , Gray B. E. , Lokman P. M.
Published: August 2010

Recovery from acute and chronic stress in the pot‐bellied seahorse Hippocampus abdominalis under aquaculture conditions was investigated in this study to evaluate (a) whether these relatively slow and sedentary fish develop the ‘fight or flight’ response and (b) the impact of transportation stress on pot‐bellied seahorse physiology. Fish were exposed to either a control treatment, an acute stressor (air exposure for 60 s) or a chronic stressor (confinement or transportation). Plasma concentrations of cortisol, glucose and lactate did not increase in response to an acute stressor, suggesting that adrenergic activation was absent. In contrast, chronic stress initiated increases in cortisol (77 ng ml−1) and glucose (7 mM), which both returned to pre‐stress concentrations (4 ng ml−1, 4 mM respectively) within the subsequent 6 h. Recovery from chronic stress thus fitted the teleost paradigm, i.e. plasma levels of cortisol and glucose returned to pre‐stress values in c. 6 h during recovery from a chronic stressor. The seemingly rapid return to homeostasis suggests that special precautions, over and above normal procedures, may not be required for long‐distance transportation of pot‐bellied seahorses.
Freshwater adaptation during larval, juvenile and immature periods of starry flounder Platichthys stellatus, stone flounder Kareius bicoloratus and their reciprocal hybrids
Authors: Takeda Y. , Tanaka M.
Published: August 2010

The freshwater tolerance of starry flounder Platichthys stellatus, stone flounder Kareius bicoloratus and their reciprocal hybrids, produced by artificial insemination, were examined in the larval, juvenile and immature phases. Survival rate on being transferred to fresh water in the pre‐settlement phase was 0% in stone flounder and hybrids and 16·7% in starry flounder. This rate in the post‐settlement phase was elevated to >50% in starry flounder and hybrids but was still 0% in stone flounder and similarly in the immature period starry flounder and hybrids survived in fresh water, although stone flounder did not. The lamella chloride cells of the gill epithelium increased in starry flounder and hybrids in fresh water in all periods. Densities of lamella chloride cells increased from 1·6 ± 0·4 (mean ±s.e. number of cells per 1 mm filament) before the transferral (day 0) to 60·3 ± 6·2 on 14 days after the transfer to fresh water (day 14) in starry flounder in the immature period. These densities in hybrids were 0·6 ± 0·3 and 1·0 ± 0·3 on day 0, and, 35·3 ± 2·8 and 23·2 ± 4·6 on day 14, respectively. Stone flounder did not show a substantial change in chloride cell densities throughout the experimental period. These results suggest that low salinity tolerance was well developed in the settlement period in starry flounder and hybrids, and hybrids were also adapted to fresh water sufficiently regardless of the cross type.
Egg capsule morphology of Parascyllium variolatum (Duméril, 1853) (Chondrichthyes; Parascylliidae), with notes on oviposition rate in captivity
Authors: Caruso J. , Bor P. H. F.
Published: August 2010

The egg capsule of Parascyllium variolatum is described for the first time, based on 57 eggs laid by three captive fish over a 167 day study period at Melbourne Aquarium. The egg capsule is bulbous, bearing two elongated horns. An indistinct or rudimentary third horn may be present. Aprons present; fibres present; small lateral fringes present. Notes on oviposition rates are also discussed and were shown to vary from 12 to 39 days with one or two eggs being deposited each time.
An assessment of de‐calcification procedures for δ13C and δ15N analysis of yellow perch, walleye and Atlantic salmon scales
Authors: Sinnatamby R. N. , Bowman J. E. , Dempson J. B. , Power M.
Published: August 2010

The scales of three species of fishes, yellow perch Perca flavescens, walleye Sander vitreus and Atlantic salmon Salmo salar, were acidified and the isotopic signatures were compared to non‐acidified scales from the same fishes. No significant acidification effects on either carbon or nitrogen isotope signatures were found. Results contrast with earlier literature findings noting significant acidification effects and suggest acidification tests be undertaken before scales are used for temporal reconstruction of fish food web positions.
Apparent semi‐lunar spawning rhythmicity in a brackish cardinalfish
Authors: Pisingan R. S. , Takemura A.
Published: August 2010

The purpose of the present study was to examine the lunar‐related spawning rhythmicity of the amboina cardinalfish Apogon amboinensis, which is a euryhaline species inhabiting mangrove creeks in the Indo‐Pacific area. During the reproductive season, the gonado‐somatic index increased towards and peaked within a week of the first and last quarter moon. Histological observations of the ovaries also showed development of yolk‐laden oocytes towards the first and last quarter moon; postovulatory follicles, an indicator of spawning, appeared around these lunar phases. Fish with immature oocytes in the ovary were also collected in the same lunar phases, suggesting that at least two fish populations with different oocyte development stages exist at any given time. The levels of two steroid hormones secreted from the ovarian pieces into a culture medium with human chorionic gonadotropin were measured using enzyme‐linked immunosorbent assay (ELISA). The level of oestradiol‐17β increased around the new and full moon periods. On the other hand, 17α,20β‐dihydroxy‐4‐pregnen‐3‐one levels increased around the first and last quarter moon, suggesting that the fish are actively undergoing vitellogenesis and final oocyte maturation around the respective lunar phase. These results suggest that with the 1 month ovarian development process, A. amboinensis exhibits a semi‐lunar spawning pattern with peaks around the first and last quarter moon. When A. amboinensis were reared under laboratory conditions without the tidal stimuli, mouth‐brooding was initiated in 13 of 20 males within a week of the first and last quarter moon. The possibility of a lunar‐related endogenous rhythm in A. amboinensis is discussed.
A long‐term study of population characteristics and downstream migrations of the European eel Anguilla anguilla (L.) and the effects of a migration barrier in the Girnock Burn, north‐east Scotland
Authors: Chadwick S. , Knights B. , Thorley J. L. , Bark A.
Published: August 2010

Downstream migrations and population characteristics of eels Anguilla anguilla were studied between 1967–1982 and 2002–2005 using a fish trap and electrofishing in the Girnock Burn, a small oligotrophic upland sub‐catchment of the River Dee, north‐east Scotland, 70 km from the tidal limit. In limited mark‐recapture studies, 9% of eels were recaptured up to three times and 97% of all recaptures were made at the same electrofishing site. The recaptured eels had a low mean growth rate of c. 13 mm year−1. Smaller eels appeared to show preferences for shallower habitats with small boulder and gravel–sand substrata. Trap catches exhibited seasonal modes in total length at 140–180 mm in late spring, and 320–340 mm in early autumn, probably relating to water temperatures and discharges. From other studies, it is inferred that the spring mode comprised sexually undifferentiated nomadic eels and the autumn mode differentiated males beginning their spawning migration. Large female eels were rare. The fish trap appears to have formed a major barrier to upstream migration since its construction in 1966. In‐stream density has decreased significantly since then from 16 to three eels 100 m−2, biomass from 260 to 78 g 100 m−2 and emigrants from 700 to 100 individuals year−1. Emigrants have comprised c. 5% of the standing stock year−1 since the 1970s. The proportion of larger differentiated eels in the Girnock Burn has, however, remained relatively constant and escapement has been c. 100–200 (probably male) eels year−1 since the late 1960s. Evidence, including that from other northerly British rivers, is reviewed to assess the possible impacts of Europe‐wide declines in glass eel recruitment since the 1980s. It is recommended that the data series be maintained, plus further sex determination and ageing studies. Installation of an upstream trap to capture immigrants and studies of recolonization are proposed.
Stable isotope records from otoliths as tracers of fish migration in a mangrove system
Authors: Huxham M. , Kimani E. , Newton J. , Augley J.
Published: August 2010

The ratios of stable isotopes 18O:16O and 13C:12C were measured in otolith carbon taken from nine species of fishes caught within mangroves and on the reef at Gazi Bay, Kenya. Before analysis, otoliths were divided into ‘larval’‘post‐larval’ and ‘adult’ sections using a drill. Fishes were putatively classified as ‘mangrove residents’‘offshore residents’ or ‘migrants’ on the basis of information from the literature, and depending on where they were caught (mangroves only, offshore only or both mangroves and offshore) in the present study. Eight of the species exhibited an increase in otolith 13C:12C with age, but this was significant only in the two migrant species Lethrinus harak and Lutjanus fulviflammus. There were no consistent patterns in 18O:16O with age, or between migrants and non‐migrants. These results suggest that comparing absolute values of otolith oxygen and carbon isotope signatures between fish species is not a useful way of determining migration patterns at this site, because of species‐specific differences in carbon metabolism and insufficiently steep gradients in temperature and salinity. Changes in carbon isotope signatures between life stages within a species, however, do hold promise as migration tracers.
Longer flumes increase critical swimming speeds by increasing burst–glide swimming duration in carp Cyprinus carpio, L.
Authors: Tudorache C. , Viaenen P. , Blust R. , De Boeck G.
Published: August 2010

Carp Cyprinus carpio altered the repertoire of swimming behaviour with increased flume length. While the transition speed from steady to burst–coast swimming was unaffected by flume length, fish reached higher critical swimming speed (Ucrit), consequently swimming for longer periods of time in burst–coast mode and hence performing more work before becoming fatigued. Analysis of swimming behaviour of burst–coast swimming revealed an increase in duration and a decrease in distance of forward burst movements with increasing water speeds. Frequency was unaffected by water speed. Overall, longer flumes increased Ucrit by allowing for less restricted burst–coast swimming behaviour.
Cloning of FSH‐β, LH‐β and glycoprotein hormone α subunits in pejerrey Odontesthes bonariensis (Valenciennes): expression profile and relationship with GnRH expression and plasma sex steroid levels in male fish
Authors: Miranda L. A. , Strüssmann C. A. , Guilgur L. G. , Strobl‐Mazzulla P. H. , Somoza G. M.
Published: August 2010

Three cDNAs encoding pejerrey Odontesthes bonariensis follicle stimulating hormone‐β (FSH‐β), luteinizing hormone‐β (LH‐β) and glycoprotein‐α (GPH‐α) subunits were cloned and characterized. Gene expression of these subunits was analysed by real‐time polymerase chain reaction (PCR) and compared with the brain gene expression of endogenous gonadotropin‐releasing hormones (GnRHs): Pacific salmon GnRH (GnRH‐III), pejerrey GnRH (GnRH‐I) and chicken GnRH‐II (GnRH‐II) and plasma sex steroid levels in adult males. The nucleotide sequences of the FSH‐β, LH‐β and GPH‐α subunits are 466, 558 and 677 base pairs long, encoding for mature peptides of 102, 118 and 98 amino acids respectively. Maturing males had high expression of FSH‐β and GPH‐α subunits, and intermediate levels of LH‐β when compared with running ripe and spent stages. These animals had the lowest plasma testosterone (T) and 11‐ketosterone (11‐KT) values as well as low expression of sGnRH, cGnRH‐II and pjGnRH. Running ripe males had the lowest expression of FSH‐β and the highest expression of LH‐β and GPH‐α subunits, and of the three GnRH genes. At this stage, the highest values of T and 11‐KT were observed. Spent males showed low expression of the three gonadotropin (GtH) subunits, sGnRH, pjGnRH and low levels of T. At this stage, 11‐KT levels and cGnRH‐II expression showed a tendency to decrease but the values were not statistically significant (P < 0·05) to running ripe stage. The present results would suggest that T and 11‐KT modulate the expression of the FSH subunits. The expression of the anterior brain GnRH variants, sGnRH and pjGnRH is correlated with LH‐β expression and reinforce the importance of the forebrain GnRH variants on the regulation of pituitary function.
Correlation between boldness and body mass in natural populations of the poeciliid Brachyrhaphis episcopi
Authors: Brown C. , Jones F. , Braithwaite V. A.
Published: August 2010

The boldness of individual Brachyrhaphis episcopi, collected from regions of high and low predation, was investigated using two independent assays: (1) the time to emerge from cover and (2) the propensity to leave shoal mates and investigate a novel object. A strong correlation between the two assays was revealed such that fish that emerged from shelter sooner were also more likely to approach a novel object. This is indicative of a boldness personality axis acting across both behavioural contexts. Fish from high‐predation areas were bolder than those from low‐predation areas and males were bolder than females. A significant correlation between body mass, standard length (LS) and boldness score was also found. In general, bold fish had a greater body mass at a given LS than shy fish. These results suggest that personality traits are strongly influenced by population‐specific ecological variables and may have fitness consequences in wild populations.
Effects of surgically implanted transmitters on anguilliform fishes: lessons from lamprey
Authors: Moser M. L. , Ogden D. A. , Sandford B. P.
Published: August 2010

Passage success of adult Pacific lamprey Lampetra tridentata at a large, hydropower dam was negatively correlated with the size of surgically implanted transmitters. This comparatively large field study (>800 fish) found effects that were not detectable in the laboratory.
Rate of energy depletion and overwintering mortality of juvenile walleye pollock in cold water
Authors: Kooka K. , Yamamura O. , Andoh T.
Published: August 2010

The winter energy deficit and mortality of juvenile walleye pollock at extremely cold temperature were examined by field observations and laboratory experiments. In the Doto area, along the northern coast of Japan, juvenile walleye pollock resided on the continental shelf despite extremely cold temperatures (mean 0·4° C) during the latter half of winter (March to April). Measurements of the rate of energy depletion (equivalent to the routine metabolic rate) revealed that juvenile walleye pollock consumed 37% less energy at 0·5° C than at 2·0° C, suggesting an energetic benefit of residence in cold water (<1·0° C) over the shelf during winter. Prior to the starvation experiments, temperatures and ration level in the holding tanks were adjusted to create two different body condition groups of fish. Under the thermal condition of the latter half of winter (0·5° C), fish with a mean condition factor of 0·6 and 0·5 suffered 19·1 and 74·5% mortality, respectively, at the end of the experiments (after 56 days). The residual analysis of total body energy demonstrated that the cause of mortality was mainly associated with the depletion of energy reserves. When a logistic regression model for mortality derived from the experiments was applied to wild fish collected in March, the estimated overwintering mortality in 2004 and 2005 was 25·4 and <2·3%, respectively, assuming no feeding during the winter. Considering that juvenile walleye pollock feed during winter as shown in previous studies, intense overwintering mortality induced by energy depletion is improbable during the latter half of winter in the Doto area.
Growth differences between naturally recruited and stocked European eel Anguilla anguilla from different habitats in Lithuania
Authors: Lin Y.‐J. , Ložys L. , Shiao J.‐C. , Iizuka Y. , Tzeng W.‐N.
Published: August 2010

European eels Anguilla anguilla from freshwater lakes in Lithuania had slower growth rates and lower backcalculated total lengths (LT) than those from lagoons and coastal waters, but no significant differences were found among fish with different migratory histories or between naturally recruited and stocked fish except a higher LT at age of stocked European eels at ages 5 to 8 years. The asymptotic LT did not differ among habitats or migratory histories, but the stocked eels in the lakes had smaller K (coefficient from the von Bertalanffy growth function) than did the both naturally recruited and stocked eels in the lagoon and coastal waters. The growth rate of European eels in Lithuania might be influenced mainly by different habitats rather than different migratory histories and stocking. The lower LT at age of naturally recruited fish at ages 5–8 years compared to stocked fish might result from the extra energy costs entailed in migration from the Atlantic and across the Baltic Sea.
Seasonal change in the gastric evacuation rate of rainbow trout feeding on natural prey
Authors: Kawaguchi Y. , Miyasaka H. , Genkai‐Kato M. , Taniguchi Y. , Nakano S.
Published: August 2010

Seasonal changes in the gastric evacuation rate (R) and gut contents of a wild population of rainbow trout Oncorhynchus mykiss feeding on natural prey at four water temperatures (2, 7, 9 and 12° C) were measured. The R and mass of the gut contents increased with water temperature, and prey items changed seasonally. These results suggest that the R of fish feeding on natural food depends primarily on water temperature, with their consumed prey being a secondary factor.
Non‐direct homing behaviours by adult Chinook salmon in a large, multi‐stock river system
Authors: Keefer M. L. , Caudill C. C. , Peery C. A. , Boggs C. T.
Published: August 2010

Two non‐direct homing behaviours, overshoot of natal tributaries and temporary non‐natal tributary use, were evaluated for 5150 radio‐tagged spring–summer Chinook salmon Oncorhynchus tshawytscha from 40 populations in the large Columbia River system. Over 7 years, 2–44% (mean = 15%) of individuals within each group temporarily entered presumed non‐natal tributaries. In addition, many Chinook salmon from lower river tributaries initially travelled 3 to >250 km upstream in the main‐stem river beyond confluences with presumed natal tributaries before returning to the natal sites (‘overshoot’). Both overshoot and temporary tributary use behaviours declined exponentially with increasing distance from the natal tributary. Non‐direct homing also increased later in the season as water temperatures rose and was associated with hatchery origin in some cases. The behaviours may reflect a mix of active searching for olfactory cues from natal sites, behavioural thermoregulation and orientation challenges in a large‐river migration corridor transformed by dams and reservoirs. While anadromous salmonid homing is generally accurate and precise, these results indicate that route finding can be non‐direct, potentially increasing energetic costs and harvest risks during migration.
Size‐assortative nest preference in a paternal brooding blenny Rhabdoblennius ellipes (Jordan & Starks)
Authors: Takegaki T. , Matsumoto Y. , Tawa A. , Miyano T. , Natsukari Y.
Published: August 2010

Field and laboratory studies were conducted to clarify the processes contributing to the size‐assortative nest use by males of a paternal brooding blenny Rhabdoblennius ellipes. The use of natural and artificial nests by males in the field was highly size‐assortative; males used smaller nests even when larger nests were available. Aquarium nest choice experiments without a competitive male strongly suggested that the size‐assortative nest use by males is not the result of male–male competition for larger nests, but male preference for size‐matched nests. Males were likely to choose nests on the basis of the nest entrance size rather than nest length and volume, suggesting that the size‐assortative nest preference in this species is an adaptation to predation pressure against eggs and resident males.
The characteristics of invasive fishes: what has been learned so far?
Authors: García‐Berthou E.
Published: August 2010

Invasive species are increasingly recognized as one of the main threats to biodiversity and both an urgent need and a unique tool for ecological research. Although attempts to identify future invasive species are not new to ecology, rigorous quantitative analyses emanate mostly from the last decade. In 2001, quantitative studies dealing with the distinguishing ecological features of invasive species were reviewed but no papers on fish species were identified. Subsequently, several quantitative studies have addressed this issue for freshwater fishes, including those that have focused on California, Colorado, the Great Lakes of North America and the Iberian Peninsula. In the present paper, 12 such studies are reviewed and compared with regard to their conclusions and methodology. The issues of different invasion stages and comparison strategies, propagule pressure, information‐theoretic analyses v. sequential techniques, use of phylogenetic comparative methods and spatial scale are discussed. Non‐native fish transport and release are the least investigated although taxonomy and human interests seem key in these first initial stages. Establishment success, which has received more study, seems more multi‐factorial, context‐dependent and more mediated by species‐specific life‐history traits. The dispersal and impact phases are less understood, although the comparison of traits (and taxonomy) between native and invasive species and particularly its variability holds promise. The lack of data on propagule pressure and the use of sequential techniques for observational data sets with many intercorrelated variables could affect the conclusions of previous studies. Research on the dispersal, impact and particularly transport and introduction phases should be prioritized rather than establishment. All the studies identified were at temperate latitudes in the northern hemisphere; studies in other regions and comparison of different regions and multiple scales are lacking.
From introduction to fishery dominance: the initial impacts of the invasive carp Cyprinus carpio in Lake Naivasha, Kenya, 1999 to 2006
Authors: Britton J. R. , Boar R. R. , Grey J. , Foster J. , Lugonzo J. , Harper D. M.
Published: August 2010

Following the accidental introduction of the carp Cyprinus carpio into Lake Naivasha during 1999, a sustainable population became rapidly established and in early 2004 became the principal species exploited in the commercial fishery. Over 9000 kg of carp were harvested from the lake between October 2005 and 2006, when fish were captured between fork lengths (LF) 200 and 800 mm (>8 kg). Diet of carp <100 mm LF was dominated by zooplankton, >100 mm LF there was a shift to benthic macro‐invertebrates, with these carp feeding principally upon food resources previously unexploited by the fish community. Contrary to predictions and despite the increasing carp abundance, there has been macrophyte regeneration in littoral areas since 2004. There have been substantial increases in areal cover, with coverage in 2006 at levels not observed since the late 1980s, and significant increases in species richness. Possible reasons for this, and the significance of this carp introduction, are discussed.
Can sunbleak Leucaspius delineatus or topmouth gudgeon Pseudorasbora parva disperse through saline waters?
Authors: Scott D. M. , Wilson R. W. , Brown J. A.
Published: August 2010

In order to determine the potential for the invasive fishes sunbleak Leucaspius delineatus and topmouth gudgeon Pseudorasbora parva to disperse through saline waters their behaviour and physiology were investigated during exposure to salinities of 10·0 and 12·5. Increased salinity caused an increase in whole body cortisol in both species, but sunbleak and topmouth gudgeon showed very different metabolic and behavioural responses to the salinity stress. Sunbleak displayed increased swimming activity in brackish water, which may be important for dispersal through saline waters in the wild, although there were increased metabolic costs associated with this behaviour. Conversely, topmouth gudgeon showed a reduction in both swimming activity and metabolic rate in brackish waters. A pronounced depression in food intake (70–80%) was shown by both species during the salinity exposures. Both sunbleak and topmouth gudgeon, however, showed a full recovery of food intake within 24 h following return to fresh water. Despite the fact that exposure to saline waters is stressful, and affects both physiology and behaviour, rapid recovery of appetite after return to fresh water suggests that short‐term use of brackish waters is a feasible dispersal route for sunbleak and topmouth gudgeon in the wild.
Is genetic variability so important? Non‐native salmonids in South America
Authors: Valiente A. G. , Juanes F. , Nuñez P. , Garcia‐Vazquez E.
Published: August 2010

Three salmonid species introduced in Patagonian national parks in Argentine have experienced different degrees of expansion. Atlantic salmon Salmo salar is restricted to a few river‐lake systems and its populations have been declining over recent years. Both rainbow Oncorhynchus mykiss and brown trout Salmo trutta populations have expanded from their introduction sites and now occupy a wide range of freshwater ecosystems. Genetic variation at the same neutral markers (microsatellite loci) was examined for different populations of the three species acclimatized to the same areas, and compared with that of native populations. Founder effects denoted as reduced variability and great differentiation with respect to the native populations were detected. Significant reduction in variability has not been an obstacle for successful adaptation of rainbow and brown trout, indicating that genetic variability per se cannot be claimed as the reason for their different outcomes in the new habitats.