bluuebunny/crossref_metadata_2025 huggingface dataset:
The dispersion of sole, Solea solea and plaice, Plemonectes platessa within and away from a nursery ground in the Irish Sea
Authors: Rogers S. I.
Published: April 2005

Populations of sole and plaice were sampled on and around a nursery on the North Wales coast during May, July arid October 1989 and 1990, and the distribution of age‐groups described. Pre‐recruit sole were tagged and reieased on the same area during September 1988 to provide information on their larger scale movements. Juvenile sole remained on the nursery ground close inshore until after their first winter, whereas plaice of the same age—group became more widely dispersed. Both species were still associated with the coastal zone as 2‐groups, when they were vulnerable to capture by commercial trawls. The gradual movement of sole out of the nursery was almost complete by October of their third year. Sole tag returns were obtained mainly from the NE Irish Sea. and also from the E coast of Ireland. Only three of the 68 returns came from outside the Irish Sea, one from the SE Irish coast, one from Swansea Bay and another from the outer Bristol Channel. Published data indicated that plaice undergo more rapid and more extensive migrations within and away from the Irish Sea than sole of the same age‐group. Juvenile plaice and sole populations from nursery grounds throughout the NE Irish Sea would become mixed, and could contribute to any of the spawning populations in that area.
Can cost–benefit analysis explain fish distribution patterns?
Authors: Huntingford F. A.
Published: April 2005

This review describes some recent theoretical and empirical research into the way fish respond to spatial heterogeneity in their environment, and particularly to patchily distributed resources. The ways in which the need to acquire food interacts with other important requirements such as thermoregulation and predator avoidance to determine space use are considered, as are interactions with other members of the same species, viewed both as shoaling companions and as competitors. Recent developments in ideal free theory are discussed and the extent to which this formulation can explain how fish distribute themselves among feeding patches is examined. The implications of overtly aggressive interactions, in the form of dominance hierarchies and territorial systems, for distribution patterns in the laboratory and in the field are also reviewed. Finally the extent to which cost–benefit analysis can help to explain fish distribution patterns and the relative importance of behavioural processes compared to other determinants of the distribution of fish are considered.
Positioning behaviour in fish shoals: a cost–benefit analysis
Authors: Krause J.
Published: April 2005

Shoal position can have a strong influence on individual fitness. Individuals in front positions of shoals were observed to have higher feeding rates than individuals elsewhere. Manipulation of nutritional state showed that hungry individuals had a stronger preference for front positions and that the duration of food‐deprivation was positively correlated with the degree of the position preference. On the other hand, front positions (like other peripheral positions) probably incur costs in terms of increased predation risks. Experiments with Schreckstoff showed that frightened individuals seek the central part of the shoal. This suggests that individuals rotate their shoal positions according to the tradeoff between energy intake and predation risk.
Diurnal patterns in the spatial relationships between saithe, Pollachius virens, schooling in the wild
Authors: Smith G. W. , Glass C. W. , Johnstone A. D. F. , Mojsiewicz W. R.
Published: April 2005

Six saithe, length 35 to 43 cm, were tagged with acoustic transmitters and individuals tracked for between 9 and 508 h during May 1989. The tagged fish were members of a schooling group and during the study, pairs of tagged fish were tracked simultaneously for periods ranging from 9 to 139 h. These data have been used to investigate the spatial relationships between individuals schooling in the wild. Distances between individuals showed a distinct diel pattern. Tagged fish were generally closer together during the day, than either at night or the periods of dawn and dusk. Those circumstances under which pairs of tagged fish could be shown to school together were investigated by analysing the differences in their swimming directions. Schooling was generally evident during the hours of daylight, although the degree to which fish schooled varied between pairs. The degree to which the fish schooled was also dependent upon distance between the tagged individuals. Schooling could be demonstrated for saithe within 20 m of each other during the day and within 10 m in two out of three pairs at night.
Gonadal morphology of normal and sex‐reversed triploid and gynogenetic diploid coho salmon (Oncorhynchus kisutch)
Authors: Piferrer F. , Benfey T. J. , Donaldson E. M.
Published: April 2005

In this study, the gonadal morphology of untreated and sex‐reversed juvenile triploid and gynogenetic diploid coho salmon was compared with that of diploids. Testes of triploids were of the same size as those of diploids. Spermatogonia, however, were significantly bigger than those of diptoids in both diameter (P<0·001) and volume (P<0·01), suggesting that this characteristic can be a useful indicator of ploidy in the early stages of gonadal development. In females, induction of triploidy did not affect the lamellar structure of the ovaries but reduced their size considerably. Further, these ovaries had no oocytes. Treatment of triploids with oestrogen resulted in the feminization of genotypic males, which had ovaries similar to those found in tripioid females. However, gonads of triploid males partially sex‐re versed into females were identified by their enlargement, the presence of remnants of the male vascular system, and by the appearance of ovarian lacunae and germinal and somatic cells typical of triploid females, Induction of gynogenesis resulted in 100% females, of which 34% had ovaries of reduced size with areas devoid of oocytes. However, and contrary to what has been found in cyprinids, no male germ cells were observed in these ovaries. This discrepancy may reflect differences, in the mechanisms of sex determination between salmonids and cyprinids. Treatment of gynogenetics with androgen increased the number of fish with abnormal ovaries but also resulted in the production of phenotypic‐male gynogenetic diploids, of which 11% had testes indistinguishable from those of untreated control diploids.
High resolution analysis of swim path patterns of intact and olfaction‐deprived minnows (Phoxinus phoxinus) stimulated with food and potential predator odour
Authors: Essler H. , Kotrschal K.
Published: April 2005

The effects of different regimes of chemo‐stimulation on the swim path in minnows (Phoxinus phoxinus) before and after olfactory deprivation were recorded by aid of a sensitive video‐based motion analysis system (DOTFINDER 6cp, JVP). Time series of x‐y co‐ordinates were taken at 2·5 Hz from colour‐marked individuals. From these co‐ordinates, nine swim path parameters representing velocities, angles and inter‐individual distances were calculated. Each experiment consisted of the application of a water control followed by stimulation with food extract, or body mucus dilutions of rainbow trout (Oncorhynchus mykiss) a potential predator. These procedures were replicated with the same individuals before and after removal of their olfactory epithelium. Compared to the controls, only food stimulation of intact fish resulted in significant changes of single parameters. Food‐stimulated intact fish swam faster, less steadily, used more of the area and kept wider inter‐individual distances than controls. No significant changes of single swim path parameters occurred between controls and experimentals in all other treatments. Cluster‐analysis however, provided a fair separation of controls (stimulus=water) and experimental (stimulated by food or predator odour) individuals in intact fish, but failed to separate controls and experimentals in olfaction‐deprived fish. Distance travelled, median velocity and total acea use were the most discriminating parameters.
The development of schooling behaviour in Atlantic herring Clupea harengus
Authors: Gallego A. , Heath M. R.
Published: April 2005

The timing of the development of schooling behaviour in Atlantic herring Clupea harengus and the quantitative and qualitative evolution of such behaviour in the larval and post‐metamorphic stages were investigated with a simulation model and experimental observations of laboratory‐reared fish. Herring larvae started to develop schooling behaviour between the lengths of 35 and 40 mm. This coincided with the beginning of metamorphosis, characterized by ontogenetic changes which require a switch to a different antipredator strategy from that employed by early larvae, while providing the sensory and anatomical mechanisms necessary for the formation of schools. Schooling behaviour was established at the end of metamorphosis (50–55 mm) and its characteristics continued to evolve throughout the early juvenile stage. A critical period in terms of vulnerability to predation is expected between the end of the larval and beginning of the juvenile stages, before schooling behaviour is fully developed. The implications of some of the results for the methodology of future studies are also discussed.
Reproductive disturbance in a roach (Rutilus rutilus) population affected by cooling water discharge
Authors: Luksiene Dalia , Sandström Olof
Published: April 2005

To analyse a recruitment failure in a roach (Rutilus rutilus) population exposed to cooling water from a Swedish nuclear power plant, histopathological examinations were made on female gonads. Several disorders were documented, corresponding to effects previously seen in Lithuanian, Moldavian and Russian heated waters, The relative gonad size (GSI) was generally lower in the exposed population. Oocyte degeneration was observed in about 50% of the females, potentially seriously reducing their reproductive capacity. The gameto‐ and gonadogeneses also were clearly affected and generally occurred at a faster rate. Sexual maturity was earlier and was accompanied by an increased occurrence of asynchionic gonad and oocyte growth. A normal gonad development should pass through different stages, coupled to the seasons, and the difference between individuals in a population should be small. However, in some exposed fish, the sequence of seasonal development was disturbed and a simultaneous, intensive, growth of sex cells in different stages of development could be seen. An increase of variation in gonad development both within, as well as between, fish thus was documented. Conclusively, the histopathological analysis provided evidence that the observed recruitment deficit could be related to gonad failure.
Experimental test of environmental factors influencing the seaward migration of European silver eels
Authors: Vøllestad L. A. , Jonsson B. , Hvidsten N.‐A. , Næesje T. F.
Published: April 2005

In this study we test which environmental factors are influencing the migratory behaviour of seaward migrating silver European eets Anguilla anguilla in a Norwegian river. We test this by transplanting tagged silver eels upriver after catching them in a trap at the outlet of the river. We did this at four fixed dates (fixed day lengths) during 5 years. Over 74% of the variation in time from release to subsequent recapture could be accounted for by variation in time at release, water discharge at release, and moon phase at release (in decreasing order of importance). The number of days to median day of recapture of each batch decreased as the season progressed and decreased with increasing water discharge. Water temperature did not explain any of the remaining variation in the model, even if there was a significant correlation between water temperature at release and median day at recapture of each batch (in simple linear regression model). Recapture rate during the same migration season varied strongly with water temperature, but at most 33% of the variation could be explained by this factor. It was aiso evident that the recapture rate increased when the number of downward migrating untagged silver eels was high. Day length (i.e. time at release) did not explain any of the remaining variation in recapture rate.
Age and growth of eels Anguilla japonica in a Chinese river
Authors: Guan Ruizhang , Wang Xuehong , Ke Guozhen
Published: April 2005

Age and growth of Anguilla japonica sampled from the Qiulu River in southern China were studied. Mean body lengths and weights of the eels at each age were back‐calculated from their otoliths. The growth parameters for the von Bertalanffy function gave L∞= 98–2cm, K=0·07 and t0=− 1·94. Scales were observed to form firstly at the middle part of the lateral line, at a minimum body length of 160 mm and were inappropriate for ageing.
An effective method for oral administration of capsules to flatfish
Authors: Burton M. P. M. , Biddiscombe S.
Published: April 2005

Filled gelatin capsules can be inserted in the stomach of non‐anaesthetized flounder using a cheap, easy tube and plunger method.
Temperature and somitogenesis in embryos of the plaice (Pleuronectes platessa)
Authors: Brooks S. , Johnston I. A.
Published: April 2005

The rate of somitogenesis was observed in plaice embryos reared at 5 and 12°C. Somite formation occurred relatively later in development at 12 than at 5°C. At any given stage of development 5°C plaice embryos had significantly more somites than embryos reared at 12°C.
Gill morphology during hypercapnia in brown bullhead (Ictalurus nebulosus): role of chloride cells and pavement cells in acid‐base regulation
Authors: Goss G. G. , Laurent P. , Perry S. F.
Published: April 2005

The role of gill chloride cells (CCs) and pavement cells (PVCs) in acid‐base regulation was evaluated in brown bullhead catfish (Ictalurus nebulosus) subjected to acute hypercapnia (water Pco2=15 torr). Chronic (10 day) cortisol treatment was used as a tool to cause CC proliferation to permit a comparison of the regulatory capacities in groups of fish with widely different gill CC populations. Cortisol (4mg kg−1 day−1) caused a pronounced increase (170%) in the surface area of CCs exposed to the water based on scanning and transmission electron microscope analysis. The density of PVC apical membrane microvilli was significantly increased (20%) by cortisol treatment. Exposure of either group of fish to hypercapnia caused similar changes in gill epithelial morphology including: (i) a marked reduction in the surface area of exposed CCs (52 and 78% reduction in the control and cortisol‐treated fish, respectively); and (ii) pronounced increases in PVC apical membrane microvilli density (21 and 27% in the control and cortisol‐treated fish, respectively).

The rates of Cl− uptake (Jincl−) and Na+ uptake (JinNa+) were elevated (150 and 262%, respectively) in the cortisol‐treated fish. Regardless of treatment, Jincl− was markedly reduced to approximately the same levels after 6 h of hypercapnia, JinNa+ was stimulated in the control group and reduced in the cortisol‐treated group and thus, after 6 h of hypercapnia, JinNa+ was equal in each group. The similar morphological responses in fish possessing different initial populations suggests that the predominant mechanism of acid‐base regulation during hypercapnia, reduction of C1−/HCO3− exchange, is accomplished by removal of the CC‐associated C1‐/HCO3− exchange sites from the water. The increase in PVC microvilli density during hypercapnia suggests a role for the PVC in acid‐base regulation.
Time of start of spawning in Atlantic cod (Gadus morhua) females in relation to vitellogenic oocyte diameter, temperature, fish length and condition
Authors: Kjesbu O. S.
Published: April 2005

Spawning time of female Atlantic cod (Gadus morhua L.) can be predicted to within 3 days using vitellogenic oocyte diameters measured over the last month before spawning. Simulations show that a l°C drop in temperature during vitellogenesis delays spawning by about 8–10 days. Similar results were obtained with fish on low ration for 4–8 months before spawning. Moderately fed females held over two to four consecutive spawning seasons demonstrated a significant delay (⋍3–40 days) in the date of first spawning as the fish grew older and more fecund. Forecasting studies on spawning migrating Arcto‐Norwegian cod gave no evidence of a significant effect of fish length on the time of spawning. Warmer water temperature during vitellogenesis for the larger fish appears to compensate for the negative effect of fecundity On spawning time.
Taxonomy, biology and abundance of icefishes, or noodlefishes (Salangidae), in the Yellow River estuary of the Bohai Sea, China
Authors: Shuozeng Dou , Dagang Chen
Published: April 2005

Four species of icefishes were sampled in the Yellow River estuary of the Bohai Sea from April 1984 to April 1985 and from February 1988 to June 1989. Morphological analysis showed that they belonged to three subfamilies of Salangidae: one species from Protosalangicae, Protosalanx chinensis; two species from Salanginae, Salanx ariakensis and Salanx prognathus; and one species, Neosalanx andersoni, from Salangichthyinae, a new subfamily. External morphological characteristics, population composition, growth, maturity, food habits, longevity, fecundity, abundance and distribution of these icefishes are described. Based on these analyses, a clear outline of taxonomy, zoogeography aod biology of icefishes in the Yellow River estuary of the Bohai Sea was established.
Abundance, reproductive period, and feeding habits of eleotrid fishes in estuarine habitats of north‐east Brazil
Authors: Teixeira Rogério L.
Published: April 2005

Aspects of the abundance, reproduction, and feeding habits of Dormitalor maculatus, Eleotris pisonis, and Guavina guavina were assessed in the shallow waters of the Mundaú/Manguaba estuarine system, north‐east Brazil. Dormitator maculatus, the most abundant species, was caught in salinities ranging from 0·1 to 20·3 ppt and temperatures from 25·0 to 36·0° C. Eleotris pisonis, the second most abundant species, occurred in salinities from 0·1 to 18·2 ppt and temperatures from 25·0 to 33·0° C. Guavina guavina was rare at the stations sampled. Peak gonadal development was found during the winter (wet season) in D. maculatus and E. pisonis, and probably may occur during this season in G. guavina. Size‐at‐maturity was 51 and 46 mm T.L. for males and females of D. maculatus, respectively, and 57 and 43 mm T.L. for males and females of E. pisonis, respectively. Dormitator maculatus was omnivorous, and ingested primarily macrophytes, followed by sediment, and unidentified eggs; E. pisonis and G. guavina were predaceous, with the former preying mainly upon the gastropod Neritina virginea, and the latter mainly upon the crab Goniopsis cruentata. Dormitator maculatus and E. pisonis appear to coexist because of differences between the two in microhabitat and food utilization. The two more similar species, E. pisonis and G. guavina appear to coexist due to differences in spatial distribution.
Vertical segregation and seasonal changes in fish depth distributions between lakes of contrasting trophic status
Authors: Rowe D. K.
Published: April 2005

High frequency (200kHz) echosounding was used to determine vertical structuring and seasonal changes in the depth distributions of limnetic fish in three New Zealand lakes. Juvenile (f.l. 30–50 mm) and large‐sized (f.l. 50–80 mm) smelt Retropinna retropinna were segregated into discrete layers by depth in all three lakes throughout the year. Larval and post‐larval bullies Gobiomorphus cotidianus (f.l. 8–20 mm) formed a further layer between the layers of small and iarge‐sized smelt. Although the depths of the large‐sized smelt and bully layers changed on a seasonal basis, vertical segregation between the three layers of fish persisted throughout the year, even when the lakes were homothermal. Seasonal movements of fish were disrupted by the autumnal deoxygenation of the hypolimnion in Lake Rotoiti. The schools of large‐sized smelt were forced to ascend towards the layer of bullies, but segregation between these smelt and the bullies was maintained as the smelt occupied a much reduced depth range above the hypolimnion, and just below the bullies. The winter descent of bullies, which precedes their transition to a benthic existence failed to occur in Lake Rotoiti, even though the lake was fully mixed at this time.
Proteinase inhibitor(s) in seminal plasma of teleost fish
Authors: Dabrowski K. , Ciereszko A.
Published: April 2005

Anti‐proteinase activity has been found in seminal plasma of three teleost fish: rainbow trout, whitefish and yellow perch. The activity was effective against trypsin (bovine and cod) and acrosin (boar), but not bovine chymotrypsin. Inhibitor activity against fish trypsin was nine‐ to ten‐fold higher than against bovine trypsin. All anti‐proteinase activity remained in the retentate after filtration through molecular filter with 30 kDa cut‐off membrane and eluted from a column of Sephacryl S‐200 HR at the volume characteristic for molecular weight of approximately 90 kDa (data for rainbow trout). Inhibitor(s) had low thermal stability (50–60% activity remained after 15 min at 60° C). The discovery of proteinase inhibitor(s) in the seminal plasma of teleosts raised the question of the regulatory function of this protein in the systematic group of fishes having anacrosomal spermatozoa.
A comparison of the movements of two species of gadoid in the vicinity of an underwater reef
Authors: Sarno B. , Glass C. W. , Smith G. W. , Johnstone A. D. F. , Mojsiewicz W. R.
Published: April 2005

Two saithe (35 and 38 cm) and two pollack (43 and 44 cm) were tracked simultaneously for 170 h. During the day, saithe generally patrolled over the whole of an underwater reef as part of a school, making occasional excursions off the reef to another smaller reef 250m distant. At night, saithe movements were largely limited to the reef. Pollack covered less than 50% of the reef during the study period, moving only small distances off the reef. Pollack swam more slowly than saithe during the day, but at the same speed at night.
Breeding ecology and nest aggregations in a population of Salaria pavo (Pisces: Blenniidae) in an area where nest sites are very scarce
Authors: Almada Vitor C. , Gonçlalves Emanuel J. , Santos Antóio J. , Baptista Céu
Published: April 2005

In this paper we present data on the breeding ecology and patterns of nest aggregation in a population ofSalaria pavo (Pisces: Blenniidae), in an area where hard substrates are very scarce. The study site was at Ria Formosa, an extensive littoral lagoon on the south coast of Portugal. The only hard materials available are bricks, tiles, stones and debris that clam culturists use to delimit their fields. The males of S. pavo establish nests intertidally in the holes of the bricks where they guard the eggs. Data were collected at low tide inspections of these artificial ridges and underwater behavioural observations during high tide. The main results are: (i) the same male can establish sequentially more than one nest in the same breeding season; the number of males that stay within the bricks increases before the start of the breeding season and declines towards its end; (ii) there is a large excess of mature males that do not establish nests and they are significantly smaller than the nesting males, suggesting very strong competition for nest sites; (iii) the nests of several males occur in adjacent holes of the same brick, sometimes being entirely surrounded by other nests. Thus, in this population, there is virtually no defended territory around the nest, a situation not known for other blenniid species. This pattern of nest aggregation implies both strong competition among males and reduction of aggression between neighbour parental fishes. This can be explained by the extreme scarcity and spatial distribution of available nest sites.
Genetic variation among Atlantic salmon in six Spanish rivers
Authors: Morán Paloma , Pendás Alberto M. , García‐Vazquez Eva , Izquierdo J. I.
Published: April 2005

Genetic variation at 24 protein loci was studied in six wild Spanish populations of Salmo salar. Temporal allelic variation and gene flow existing between rivers point out the similarity of these Spanish populations as well as the effect of stocking in the actual pattern of allelic distribution.
Factors affecting the distribution of genetic variability in the guppy, Poecilia reticulata
Authors: Shaw P. W. , Carvalho G. R. , Magurran A. E. , Seghersf B. H.
Published: April 2005

Previous studies on Trinidadian guppies have shown an apparent association of genetic variability, expressed as mean heterozygosity (Ho) at allozyme loci, with river order: fish from lowland sites exhibit higher mean Ho than their upland counterparts. Detailed genetic and behavioural observations were undertaken in the present study by repeated sampling throughout two river courses to examine population heterogeneity. Results show that the predation regime mediated mating behaviour of upland and lowland populations in the wild is not as divergent as previous laboratory observations have suggested. Furthermore, genetic variation at the eight loci variable in Trinidadian populations (p100=0·13–O·88, H0=O·03–0·23) appears to bear little association with predation regime, but is related to sub‐structuring of populations by habitat features and geographic isolation. We therefore conclude that the observed patterns of genetic variability arise primarily as a consequence of stochastic as opposed to deterministic factors.
The growth of grey mullet in a rural and urbanized Irish estuary
Authors: Walsh A. , Reav P. , O'Halloran J. , Cahill K.
Published: April 2005

The condition of grey mullet from the urbanized Coliigan estuary was higher than that of mullet from the rural Barnawee estuary and those of several other samples described in the literature (P<0·05). It is suggested that their better condition was due to dietary supplementation from creamery and tannery effluent in the urbanized estuary. As a result of their distinctive condiiion, indirect evidence is provided for homing in this species, at this site.
A study on teleost phylogeny using specific antisera
Authors: Buchmann K. , Pedersen K.
Published: April 2005

The phylogenetic position of 26 teleost species has been studied by the use of a dot blot test based on eight rabbit antisera generated against serum components from representatives from various teleost orders. The isolated positions of Anguilliformes, Cypriniformes, Salmoniformes and Clupeiformes were confirmed. Lophiiformes showed some affinities for Pleuronectiformes and less for Gadiformes.
Field observations on a mating attempt of a spawning grayling, Thymallus thymallus with a feeding barbel, Barbus barbus
Authors: Poncin P.
Published: April 2005

During the spawning period of the grayling, one male was sexually stimulated by a feeding barbel and consequently exhibited the behavioural patterns of ‘approach’, ‘qnivering’ and ‘dorsal fin clasping’.
Cardiovascular, ventilatory and total activity responses of brown trout to handling stress
Authors: Laitinen Markku , Valtonen Tapani
Published: April 2005

Changes in total activity, heart and ventilation rates were observed in 2‐year‐old brown trout, following handling stress, using non‐contact bioelectronic monitoring equipment. Experiments were carried out in laboratory conditions at water temperatures below 4° C, Transfer between tanks as well as 5 min restraint stress increased the total activity of fish for 24 to 48 h, after which it declined to near the pre‐stress level. The transfer and struggle both elevated the heart rate for 3 to 4 days. Ventilation rate was elevated to a maximum of about 30% above the nominal level and recovered within 3 to 4 days. Both heart and ventilation rates were higher in feeding fish relative to fasting fish after stress and rates remained higher throughout a 7 day period of recovery. A diel rhythm of lower rates during the night appeared in both heart and ventilation rates within 3 to 4 days after handling stress.
Direct estimates of multi‐mesh gillnet selectivity to Oreochromis shiranus chilwae
Authors: Mattson N. S.
Published: April 2005

The selectivity of multi‐mesh monofilament nylon gillnets to Oreochromis shiranus chilwae was estimated directly by gillnetting in a small reservoir containing a population marked by size class. Numbers in each size class were estimated using the adjusted Petersen estimate. Pearson Type I curves were fitted to plots of selectivity against the fish length/mesh perimeter ratio, for two modes of capture: wedging and tangling. The generality of the selectivity curves is tested and discussed. The tangling component of the selectivity was unimportant, and for many applications the selectivity curves may be approximated by normal curves obtainable through indirect methods. However, the increase in the amplitude of the curves with mesh size, deserves further study.
The critical thermal limits for juvenile Arctic charr Salvelinus alpinus
Authors: Baroudy E. , Elliott J. M.
Published: April 2005

The chief objective was to determine the critical thermal limits for alevins, fry and parr of Arctic charr, Salvelinus alpinus, (L.) from four races living in Windermere (northwest England). The experimental fish were reared in a hatchery but were the progeny of wild parents. As comparisons between tethal temperatures at four acclimation temperatures (5, 10, 15, 20° C) revealed few significant racial differences, the data were pooled to estimate the lethal values for survival over 7 days (incipient lethal temperature) and over only 10 min (ultimate lethal temperature) for each life stage. Upper lethal values increased with acclimation temperatures for alevins but this effect was negligible for fry and parr, Alevins were generally less tolerant than fry and parr at lower, but not higher, acclimation temperatures; e.g. after acclimation at 5° C, mean upper ultimate values were 23·3, 25·1 and 25·7° C and mean upper incipient values were 18·7, 21·5 and 21·5° C for alevins, fry and parr respectively; after acclimation at 20° C, mean upper ultimate and incipient values were 26·2, 26·1 and 26·6° C and 20·8, 20·8 and 21·6° C for alevins, fry and parr respectively. The area of the temperature tolerance polygon (expressed as ° C2) for juvenile Arctic charr is amongst the lowest recorded for salmonids; being 409, 439 and 461° C2 for alevins, fry and parr respectively. These low values are due to lower upper tolerance limits, not high lower tolerance limits; the latter being close to 0° C (<1°C for parr and fry, <0·3° C for alevins) at all acclimation temperatures. Arctic charr are therefore amongst the least resistant of salmonids to high temperatures but probably the most resistant to low temperatures.
Effects of temperature on allocation of metabolic energy in perch (Perca fluviatilis) fed submaximal rations
Authors: Mehner T. , Wieser W.
Published: April 2005

Growth and long‐term trends of oxygen consumption were monitored at 15 and 20° C in spontaneously swimming juvenile perch fed a fixed daily submaximal ration. The average rate as well as the efficiency of assimilation were the same at the two temperatures but a much higher proportion of food energy was allocated to activity and maintenance, and a correspondingly lower proportion to growth, at 20 than at 15° C. By computing average specific rates of oxygen consumption separately for all light and dark periods, it was found that at 20, but not at 15° C, the‘ scope for spontaneous activity’ of two consecutive (dark and light) phases of a diurnal cycle was indirectly proportional to the average rate of oxygen consumption in the dark phase. This indicates that at 20° C the perch displayed partial compensation for a high metabolic rate in the dark by reducing swimming activity in the following light phase. However, the overall effect of this behaviour was probably too small to make a noticeable impact on the low conversion efficiency in the juvenile perch at 20 as compared to 15° C.
Conditions for initiation of fertilization of eggs in the copulating elkhorn sculpin
Authors: Munehara Hiroyuki , Koya Yasunori , Takano Kazunori
Published: April 2005

The reason for failure to initiate fertilization internally was examined in a cottid fish, the elkhorn sculpin, Alcichthys alcicornis which has internal gametic association and external fertilization. While eggs could be activated in calcium free hypertonic media but not be fertilized, fertilization occurred in isotouic media rich in calcium ions. The rate of fertilization was dependent on calcium concentration, and eggs were not fertilized in solutions with a calcium ion concentration of less than 0·57 mmol kg−1. Calcium ions could be replaced to some extent by magnesium ions, but the former were the more effective in fertilization. Since calcium ion concentration of ovarian fluid of A. alcicornis was 0·41 mmol kg−1, it was inferred that low calcium concentration in the ovarian fluid was the cause of the failure of A. alcicornis eggs to fertilize internally.
Influences of illumination intensity on the nearest neighbour distance in coho salmon Oncorhynchus kisutch
Authors: Azuma T. , Iwata M.
Published: April 2005

Effects of illumination intensity on the nearest neighbour distance (NND) of coho salmon in an experimental aquarium were studied under illumination intensities ranging from 0 to 4000 Ix. The NNDs in sighted (intact) fish were divided into three groups according to the illumination intensities; the largest [1.15 times fork length (f.l.)] at 0 1x, the medium (0.78 to 0.84 f.l.) at 0.01 to 0.4 1x, and the least (0.60 to 0.66 f.l.) at 4–4000 1x. The fact that NNDs under 4 1x or higher illumination conditions were significantly smaller than those under 0.01 to 0.4 1x conditions suggests a change from photopic to scotopic vision. Blinded fish exhibited constant NNDs irrespective of illumination intensity and the value was similar to that of sighted fish under the 0 1x condition. The NNDs of blinded fish and sighted fish exposed to 0 1x were larger than the simulated NND calculated by hypothesizing that fish distribute randomly in the experimental aquarium. These results indicate that NND in a coho school is maintained primarily by vision, however, the NND is not determined by vision alone but by integrated senses.
Effect of restricted feeding on early maturation in female and male amago salmon, Oncorhynchus mason ishikawae
Authors: Silverstein J. T. , Shimma H.
Published: April 2005

Incidence of early maturation of female amago salmon was reduced by >32% by feed restriction beginning in May, 5 months prior to spawning. Male early maturation was unaffected by this feed restriction regime.
The relation between morphology and behaviour during ontogenetic and evolutionary changes
Authors: Galis Frietson , Terlouw Arie , Osse J. W. M.
Published: April 2005

During development, form and function (behaviour) change while the match between them must be maintained. The quality of this match determines the importance of morphological parameters in constraining behaviour. If the match is close, the morphology of organisms will be more constraining to the behaviour than when there is a large reserve capacity that creates a certain flexibility. This leads to two questions: (1) How good is the match between form and function during development? The quality of the match necessarily changes during development because changes in structural capacity often cannot proceed at the same speed as changes in functional demand. The evidence for these changes is discussed. (2) What are the mechanisms that maintain the match between form and function during developmental and evolutionary changes? Two mechanisms for maintaining the match are discussed: (a) reserve capacity and (b) flexible muscle activity patterns. Special emphasis is given to fish examples throughout this review.
The interplay of ontogeny and scaling in the interactions of fish larvae and their predators
Authors: Fuiman L. A.
Published: April 2005

In this review and synthesis, new data from field and laboratory experiments on red drum, Sciaenops ocellatus, larvae as prey to larger fishes are presented to illustrate two approaches to the study of developmental effects on predation. Various sizes and species of predatory fishes imposed very different levels of mortality on experimental populations of red drum larvae. Differences in predator size explained little of the overall variation in mortality rates. In the laboratory, responsiveness of red drum to a single size and species of predatory fish was relatively low through much of the developmental period but increased steadily. Response effectiveness improved and the predator's capture success decreased once the prey exceeded 20 mm in length. General ontogenetic trends in the behavioural interaction of various larvae and their piscine predators are described by combining 22 data sets on a scale of roughly comparable ontogenetic state. This scale, together with absolute and relative measures of predator and prey size, are used to assess the roles of ontogeny and scaling in the predation interaction. Ontogeny is shown to be a significant contributor to changes in responsiveness, response effectiveness, and capture success. The influence of scaling always took the form of an interaction with ontogeny and not a main effect.
Predation risk and the evolutionary ecology of reproductive behaviour
Authors: Sih Andrew
Published: April 2005

A large literature exists on the effects of predation risk on foraging and survival‐related behaviours. In contrast, with some notable exceptions, relatively few theoretical or experimental studies have examined the effects of predation risk on reproductive behaviours. Existing literature on risk and reproductive behaviour and suggestion directions for future study are reviewed. In particular: (1) effects on predation risk on mating behaviour; (2) the influence of spatial patchiness on interactions between risk and reproductive behaviour; (3) the potential influence of multi‐species interactions on the effects of predation risk on mating dynamics; (4) the importance of looking at sets of inter‐related antipredator traits; and (5) some effects of predation risk on prey population patterns due to changes in prey reproductive behaviour are discussed. To illustrate various points examples involving fish and other aquatic organisms are used.
The influence of potential predators on the habitat preferenda of emerging brown trout
Authors: Bardonnet Agnes , Heland Michel
Published: April 2005

Much research has focused on the developmental behaviour of fish and it has been shown that their sensory and physical capabilities evolve very quickly during their early life. Thus, ontogenesis could influence fishes preferences for particular environmental factors. Little is known about the habitat preferences of trout during the post‐emergence phase and it is not known if they correspond to the preference curves established by the PHABSIM method for the‘ alevin phase‘. Here, the downstream movement and habitat preferences of young emerging trout were studied in a flume. In the absence of predators, alevins preferred a water depth of 20 to 30 cm and pebble rather than gravel substratum. When emergence occurred in an area with 1+ trout and sculpin, Cottus gobio, almost all the emergent trout remained cryptic. When visible, most of them were in the shallowest area (10cm depth) where their preference for pebble substratum was less marked. The presence of 1+ trout and sculpin increased the movement downstream of young trout by 20% without changing the general and diel patterns of catches. Their presence also reduced the initial growth of 0+ trout.
Effects of endogenous rhythms and light conditions on foraging and predator‐avoidance in juvenile plaice
Authors: Burrows Michael T. , Gibson Robin N. , Maclean Amanda
Published: April 2005

The influences of a light: dark cycle and a persistent endogenous rhythm of activity on foraging (on the bivalve Donax vittatus) and avoiding a predator (juvenile cod, Gadus morhua) were investigated in freshly‐caught juvenile plaice, Pleuronectes plalessa. Time lapse video recordings were made of fish in the presence and absence of prey and predators in laboratory tanks over 24‐hour periods between the times of successive daytime low waters. Endogenous rhythms of activity were seen in all experimental treatments. Swimming both close to the bottom and in the water column showed a strong circatidal rhythm, with most activity 2 to 3 h after the predicted time of high water. Swimming in the water column was more frequent at night than by day. In the presence of a population of Donax, whose siphon tips could be eaten as food, swimming close to the bottom became more frequent. This increase in benthic swimming was independent of the endogenous cycle of activity and was correlated with the frequency of attacks on siphons. The presence of the cod predator delayed the onset of foraging activity, producing a foraging/predator avoidance trade‐off. The independence of foraging from light and endogenous rhythms suggests that this trade‐off may be similarly independent. The cod also greatly reduced swimming in the water column in darkness, behaviour apparently unrelated to foraging.
Piscivory and cannibalism in Arctic charr
Authors: Amundsen P.‐ A.
Published: April 2005

Piscivory and cannibalism in Arctic charr,Salvelinus alpinus, were studied in three lakes in northern Norway: Guolasjavri, which contains only charr, Takvatn, where Arctic charr coexist with three‐spined sticklebacks,Gasterosteus aculeatusand brown trout,Salmo trutta, and Stuorajavri, where whitefish,Coregonus lavarelundominate a fish community containing six species. The prevalence of piscivory in the Arctic charr populations generally increased with increasing predator size. In all three lakes, many charr larger than 20 cm were piscivorous, but the extent of piscivory and cannibalism varied. The greatest prevalence of cannibalism was found in Guolasjavri, where 27% of charr greater than 20 cm in length had fed upon smaller conspeciflcs. In Takvatn, 5% of charr larger than 20 cm were cannibalistic, and an additional 9% had eaten three‐spined sticklebacks. In Stuorajavri, up to 74% of the charr greater than 20 cm had eaten whitefish but cannibalism was not recorded. The possible role of cannibalism in population regulation within Arctic charr populations is considered.
Lack of spatial coherence of predators with prey: a bioenergetic explanation for Atlantic cod feeding on capelin
Authors: Horne John K. , Schneider David C.
Published: April 2005

We tested two biologically based predictions that potentially influence scales of spatial association between Atlantic cod,Gadus morhua, and prey populations of capelin,Mallotus vilhsus. If cod aggregate in response to concentrations of prey, then spatial association (coherence) between capelin and cod was predicted to peak at the scale of maximum capelin spatial variance. If capelin‐cod coherence did not match the scale of maximum prey spatial variability, then capelin‐cod coherence was predicted to peak at the spatial scale that maximizes net energetic benefit to the predator. Contrary to predictions, we found no evidence of aggregative responses of cod to capelin over resolution scales of 20 m to 10 km. This result was observed consistently at the temporal scale of a single transect (c. 1 h duration) and at the scale of averaged transects (c. 2 weeks duration). Estimates of cod foraging energetics showed that they were not constrained by physiology to aggregate relative to capelin at any scale less than 10 km. A net energetic gain of 478 to 784 kJ would result if a 44 cm, 752 g cod consumed a ration of eight to 12 capelin over a period of 58 h. Energetic calculations included costs of egestion and excretion (317 to 476 kJ), maintenance (58 kJ), digestion (125 to 188 kJ), and continuous swimming during ration assimilation (79 kJ). During this period, a 44 cm cod could travel over 38 km swimming at 1 b.l. s−1. Foraging cod are virtually certain to encounter capelin over this distance based on the abundance of pre‐spawning capelin present in coastal bays during the spawning season. This study illustrates that aggregative responses of predators do no occur at all scales and possibly occur over a very limited range of scales.
Predator‐prey dynamics in an ecosystem context
Authors: Kitchell James F. , Eby Lisa A. , He Xi , Schindler Daniel E. , Wright Russell A.
Published: April 2005

Evaluating the role of fishes at the food web and ecosystem scales profits from an iterative process. At the community and population scales, prey selection by predators alters habitat selection behaviours of prey species as well as their abundance, size distributions, life histories and the consequent effects on their own prey. At the whole system scale, predation by fishes alters community structure and nutrient cycling. Thus, both direct and indirect predation effects are expressed in population structure, community composition and production processes at all trophic levels. These are the central tenets of the trophic cascade argument.

Examples are abundant and diverse. We know that predators are size selective, that resource partitioning occurs, that functional responses link the density dependence of predator and prey populations, and that predator avoidance behaviours are common. A more significant challenge exists when attempting to use this knowledge.

This presentation attempts to link theory and empiricism in forecasts of what will happen next in response to a management action or a planned experiment. Examples are drawn from whole system experiments conducted in small lakes and from large‐scale manipulations of predator populations in North America's Laurentian Great Lakes. Rapid and discontinuous or non‐linear responses are common. Extrapolating the lessons of mechanistic process studies proves insufficient because the context is dynamic. Inferences built from the whole ecosystem scale yield equally misleading results because the scale is too general, Resolving these problems will require a clever mix of selective applications of predator‐prey theory and astute empiricism.
Light‐mediated predation by northern squawfish on juvenile chinook salmon
Authors: Petersen James H. , Gadomski Dena M.
Published: April 2005

Northern squawfish Ptychocheilus oregonensis cause significant mortality of juvenile salmon in the lower Columbia River Basin (U.S.A.). The effects of light intensity on this predator‐prey interaction were examined with laboratory experiments and modelling studies. In laboratory experiments, the rate of capture of subyearling chinook salmon Oncorhynchus tshawytscha by northern squawfish was inversely related to light intensity. In a large raceway, about five times more salmon were captured during 4 h periods of relative darkness (0–03 Ix) than during periods with high light intensity (160 Ix). The rate of predation could be manipulated by increasing or decreasing light intensity.

A simulation model was developed for visual predators that encounter, attack, and capture juvenile salmon, whose schooling behaviour was light‐sensitive. The model was fitted to laboratory results using a Monte Carlo filtering procedure. Model‐predicted predation rate was especially sensitive to the visual range of predators at low light intensity and to predator search speed at high light. Modelling results also suggested that predation by northern squawfish on juvenile salmon may be highest across a narrow window of fight intensity.