bluuebunny/crossref_metadata_2025 huggingface dataset:
Demographics and recent productivity performance: insights from cross‐country comparisons
Authors: Beaudry Paul , Collard Fabrice , Green David A.
Published: April 2005

Abstract.  Over the last few decades, countries have experienced quite different patterns of productivity growth. In this paper, we emphasize the role of country level demographics in explaining these differences. In particular, looking over the period 1960–2002, we show that cross‐country data support the notion that, starting in the late 1970s, countries went through a period of technological transition that lasted at least until the mid‐1990s for the fastest adjusting countries and is still proceeding for the slower adjusting countries. The main claim of the paper is that the country‐level rate of labour growth was a key factor driving the speed of adjustment to the new technological paradigm, implying that much of the cross‐country difference in economic performance over recent decades can be explained by demographic differences across countries as opposed to the many other factors emphasized in the literature. JEL classification: O33, O41
Tax credits, insurance, and the use of medical care
Authors: Smart Michael , Stabile Mark
Published: April 2005

Abstract.  The personal income tax systems in Canada, the United States, and elsewhere permit deductions or tax credits for out‐of‐pocket health care expenditures and private medical insurance premiums. Little is known about the effects of such tax measures on individual behaviour, in contrast to the extensive research on the tax exemption for employer‐provided health insurance. In this paper, we exploit variation in the after‐tax cost of health expenditures under the tax law to estimate the tax price elasticity of demand for prescription drugs, health insurance, and other eligible expenditures. We find evidence of moderate to large tax price elasticities, compared with traditional point‐of‐service price elasticity estimates – despite the apparent differences in the way tax subsidies are experienced by consumers. In contrast, we find no evidence the tax subsidy affects demand for health insurance on the intensive margin, which we show is consistent with the theory of optimal self‐insurance. We discuss the implications of our results for recent proposals to reform public and private health insurance systems. JEL classification: I1, H2
A ‘long march’ perspective on tobacco use in Canada
Authors: Gospodinov Nikolay , Irvine Ian
Published: April 2005

Abstract.  In this paper we present a model of tobacco demand in Canada, with a view to establishing if price and tax policy on the one hand or educational, regulatory, and demographic influences on the other have been primarily responsible for the substantial drop in consumption since 1980. We address some methodological and econometric issues that have escaped the attention of some analysts to this point. Using data for the period 1972–2000, we find that non‐price developments have had a strong deterrent effect and that the price elasticity of demand is now lower than even the recently obtained low estimates propose. These findings have strong public policy content. JEL Classification: I12, C13, C22
Food for education versus school quality: a comparison of policy options to reduce child labour
Authors: Jafarey Saqib , Lahiri Sajal
Published: April 2005

Abstract.  In a model in which credit markets play a crucial role, we examine two policy options for reducing child labour, ‘food for education’ and ‘investment in education quality,’ With an imperfectly elastic supply of credit, an increase in food subsidy is more effective in reducing child labour than an ‘income‐equivalent’ increase in expenditures in education quality. The effectiveness of the latter policy improves, and the optimal share of resources devoted to this policy increases, at the expense of food subsidies, as the supply of credit becomes more elastic. JEL classification: H52, O10
Tests of microeconomic foundations of a North American common currency area
Authors: Swofford James L.
Published: April 2005

Abstract.  The movement of some members of the European Union towards a common currency area is likely to spark interest in other possible common currency areas. One such area of interest is a North American common currency area. In this paper some results from tests of microeconomic foundations of a North American common currency area are presented. These results can be viewed as favourable for the formation of a North American common currency area. JEL classification: F33, F36
Money, capital, and real liquidity effects with habit formation
Authors: Mansoorian Arman , Michelis Leo
Published: April 2005

Abstract.  The money in utility model is reconsidered in the presence of endogenous labour and habits. With standard assumptions about preferences and a policy rule that sets the nominal interest rate by adjusting the growth rate of money, the model exhibits superneutrality in the steady state. Nevertheless, habits give rise to real liquidity effects in the short run. After an increase in the nominal interest rate, employment falls, resulting in a fall in capital accumulation and in the short‐ and long‐term real interest rates. The adjustment of the capital stock is non‐monotonic. Employment and the short‐ and long‐term real interest rates may also adjust non‐monotonically. JEL classification: E22, E52, E58
Monetary union in West Africa: who might gain, who might lose, and why?
Authors: Debrun Xavier , Masson Paul , Pattillo Catherine
Published: April 2005

Abstract.  We develop a model in which governments’ financing needs exceed the socially optimal level because public resources are diverted to serve the narrow interests of the group in power. From a social welfare perspective, this results in undue pressure on the central bank to extract seigniorage. Monetary policy also suffers from an expansive bias, owing to the authorities’ inability to precommit to price stability. Such a conjecture about the fiscal‐monetary policy mix appears quite relevant in Africa, with deep implications for the incentives of fiscally heterogeneous countries to form a currency union. We calibrate the model to data for West Africa and use it to assess proposed ECOWAS monetary unions. Fiscal heterogeneity indeed appears critical in shaping regional currency blocs that would be mutually beneficial for all their members. In particular, Nigeria's membership in the configurations currently envisaged would not be in the interests of other ECOWAS countries unless it were accompanied by effective containment on Nigeria's financing needs. JEL classification: E58, E61, E62, F33
The non‐monotonic relationship between seigniorage and inequality
Authors: Bhattacharya Joydeep , Bunzel Helle , Haslag Joseph
Published: April 2005

Abstract.  We present an analysis of how political factors may come into play in the equilibrium determination of inflation. We employ a standard overlapping generations model with heterogenous young‐age endowments, and a government that funds an exogenous spending via a combination of non‐distortionary income taxes and the inflation tax. Agents have access to two stores of value: fiat money and an inflation‐shielded, yet costly, asset. The model predicts that the relationship between elected reliance on the inflation tax (for revenue) and income inequality may be non‐monotonic. We find robust empirical backing for this hypothesis from a cross‐section of countries. JEL classification: E5, P16
Using patents to mislead rivals
Authors: Langinier Corinne
Published: April 2005

Abstract.  Firms claim they do not rely heavily on patents. Yet they patent, as indicated by the large number of patents that are granted. This paper offers a possible resolution to this puzzle. It takes a simplified version of a duopoly innovation race and studies the patenting decision of an innovator who has private information about the improvability of her innovation. It is shown that a firm may use the patenting decision to mislead her rival. Under symmetric information, research can be stimulated but not disclosed. However, under asymmetric information, disclosure is more likely, even though research incentive may be weakened. JEL Classification: 031, L1
Cooperative R&D and strategic trade policy
Authors: DeCourcy Julie
Published: April 2005

Abstract.  In this paper three different cooperative R&D arrangements in a strategic trade policy model are examined. A policy game between two governments is analysed, where each government chooses a particular cooperative R&D policy in order to maximize national welfare. Allowing cooperation in R&D is also compared with the use of R&D subsidies. It is jointly optimal for both governments to allow their firms to participate in the same type of cooperative R&D, and allowing cooperation in R&D can be superior to the use of R&D subsidies. JEL Classification: F13, L24
Does S. Kuznets's belief question the Environmental Kuznets Curves?
Authors: Bousquet Alain , Favard Pascal
Published: April 2005

Abstract.  This paper examines the link between pollution and income. The main purpose is to assess whether the introduction of income inequality in a Environmental Kuznets Curve (EKC) analysis can give new insights into the relationship between pollution and economic growth. The EKC hypothesis proposes that there is an inverted U‐shape relation between environmental degradation and income per capita. We question this common result, in a simple model where the income inequality evolution is exogenous and where the planner could use only one instrument. For a set of parameter values we find, for example, a two‐hump curve. JEL classification: D3, H4, Q2.
Investing exhaustible resource rents and the path of consumption
Authors: Hamilton Kirk , Hartwick John M.
Published: April 2005

Abstract.  We set out dollar‐valued net national product for an economy with a wasting essential stock (oil deposit). We take up ‘maintaining capital intact’ and locally unchanging consumption. The percentage change in ‘net investment’ or ‘genuine savings,’ relative to the market rate of interest, denotes whether current consumption is rising, constant, or declining. JEL classification: O13, Q28, F0
Ultraviolet irradiation of tilapia spermatozoa and the Hertwig effect: electron microscopic analysis
Authors: Don J. , Avtalion R. R.
Published: April 2005

Electron microscopic analysis of U V‐irradiated tilapia sperm showed that with irradiation dose of 1800 J m−2 min−1, an irradiation duration of 0.5 min caused decondensation of sperm chromatin. This phenomenon of chromatin decondensation reached a peak after l.5min of irradiation, where ∼ 15% of the sperm showed total decondensation, and was less apparent after 3 min of irradiation or more. Damage to the cytoplasmic membrane and nuclear envelope could be seen in cells that underwent total decondensation. As the duration of irradiation increased, cytoplasmic membrane and nuclear envelope defects appeared more severe, the mitochondria were affected and appeared as empty capsules, and sperm cells tended to lose their tails. Based on these results and others reported in the literature, we propose an explanation for the ‘Hertwig curve’ obtained in tilapia using UV irradiation. Sperm cells with decondensed chromatin and damaged cytoplasmic membrane and nuclear envelope, activate the ‘developmental switch’ when they penetrate the egg, but their pronuclei are subjected to cytoplasmic nuclease digestion. Consequently, the maternal pronucleus is the only functional pronucleus in the zygote, and therefore, only haploid embryos with the exclusive maternal genome are formed. If the paternal pronucleus is not digested, these embryos will die due to improper expression of the paternal genes.
Growth in juvenile Scarus rivulatus and Ctenochaetus binotatus: a comparison of families Scaridae and Acanthuridae
Authors: Lou D. C.
Published: April 2005

Daily lapillus growth increments were used to determine age and growth parameters for Scarus rivulatus (Valenciennes) and Ctenochaetus binotatus (Randall) from reefs off Lizard Island in ihe northern Great Barrier Reef. The growth of S. rivulatus increased after settlement whilst growth of C. binotatus decreased after settlement. A check found in the otoliths of both species, and attributed to settlement, was estimated to be from 28 to 47 days for S. rivulatus and from 47 to 74 days for C. binotatus.
Temperature effects on incubation time and growth of juvenile whitefin gudgeon, Gobio albipinnatus Lukasch
Authors: Wanzenböck J. , Wanzenböck S.
Published: April 2005

Eggs of the whitefin gudgeon, Gobio albipinnatus Lukasch, were artificially obtained from adults caught in the Danube River near Vienna, Austria. Average diameter of hydrated eggs was 1.5 mm (S.D.=0.05). Incubation times decreased exponentially from 8 to 24° C. Mortality of embryos was lowest at 16° C and highest at 8° C. Total length at hatching ranged from 4 to 5.7 mm. First feeding occurred 3 days after hatching. Growth with excess food was observed for 3 months in the laboratory at 16 and 20° C. Highest growth rates obtained were 11 % fresh weight day‘. Field samples of 0+G. albipinnatus indicated four cohorts occurring in a Danube backwater. Growth in the backwater was comparable to juveniles growing at 20° C in the laboratory. From information on growth and incubation we estimate that spawning starts in the middle of May and proceeds at 2‐weekly intervals until the end of June. Incubation time and growth of 0+G. albipinnatus closely resembles that of Gobio gobio (L.).
Daily growth increments in the otoliths of the three‐spined stickleback, Gasterosteus aculeatus L.
Authors: Wright P. J. , Huntingford F. A.
Published: April 2005

Daily increment formation was demonstrated in the sagittae of the three‐spined stickleback, Gasterosieus aculeatus L., under both laboratory and field conditions. The onset of daily increment formation coincided with the day of hatching. The main sources of inaccuracy in age determination resulted from difficulties in resolving narrow increments in the sagittae of fish held at low temperatures and the increasing incidence of checks with age. The advantage of daily increments for investigating growth in this species was demonstrated from a comparison between increment‐derived age‐at‐length data and length‐at‐capture data, since the latter significantly under‐estimated early growth rate within a population.
The feeding strategies of Liza ramada (Risso, 1826) in fresh and brackish water in the River Tagus, Portugal
Authors: Almeida P. R. , Moreira F. , Costa J. L. , Assis C. A. , Costa M. J.
Published: April 2005

The stomach contents of samples of the mugilid Liza ramada (Risso, 1826), captured at Alcochete (brackish water zone of the Tagus Estuary) differed from those from Vala Nova (freshwater zone of the same estuary).

In the freshwater zone of the estuary the mullet ingested preferentially planktonic micro‐algae, while in the brackish water they ate benthic micro‐algae.

The stomach contents from Vala Nova showed a higher diversity of food items, compared with those from Alcochete. At Alcochete the Naviculales (numerical frequency, 82%) was the most representative order, while at Vala Nova it was the Coscinodiscales (61%) and the Chlorococcales (16%).

In fresh water, the stomach contents contained about 25–4% organic matter, while at Alcochete only 8.7% was found.

In the brackish water zone the ingestion rhythm was related to the tidal cycle, attaining a maximum during the high tide and a minimum at low tide.

At Vala Nova the mullet ate regularly throughout the day. showing a slight increase at dawn and dusk. Apparently, the fish remained inactive by night, at both locations.
Spawning and distribution of bluefish Pomatomus saltatrix (L.) in the northwestern Mediterranean
Authors: Sabatés A. , Martin P.
Published: April 2005

The present study was carried out on the Catalan coast, the northern limit of the geographic distribution of Pomatomus saltatrix (Linnaeus, 1766) in the Mediterranean. Within the area studied, both larvae and adults were more abundant in the southern part, where surface temperature was slightly higher than in the north. Spawning of P. saltatrix was limited to the warmest months, from July to September, when the surface temperature was about 25° C, The most common larval sizes, between 2.25 and 2.75 mm s.l., were distributed over the continental shelf, and the greatest concentrations were found between 20 and 100 m, suggesting an inshore spawning. Larvae, including the smallest sizes, were found in the most superficial layers and no evidence of vertical migration was observed. The species was regularly fished in the southern zone, maximum monthly catches ranging between 10–20 tonnes. The presence of adults in the coastal zone showed a marked seasonality closely related to temperatur, the lowest catches corresponding to the coldest months.
Environmental induction of Na+ transporter affinity in Atlantic salmon embryos
Authors: McWilliams P. G.
Published: April 2005

Atlantic salmon (Salmo salar L.) alevins hatched from eggs transferred from high‐ to low‐Na water at 250° days, before the onset of the phase of increasing whole egg sodium content (at ∼380°days), showed a significantly reduced Km for Na+ transport, whereas transfer at 400° days did not produce any change in Km. Alevins hatched from eggs given acid shocks of 1, 3, 7 or 14 days duration initiated at 250 or 400° days showed no significant changes in Na+ transporter Km. Extended acid exposure (38 days) from 250°days to hatching resulted in a slight lowering of Km (P<0.05). A 24‐day acid exposure from 400°days to hatching had no effect on Na+ transporter Km. Alevins hatched from eggs incubated throughout in acidified water had a significantly reduced Km compared to controls (P<0.01).

The timing and duration of periods of Na depletion of eggs is considered with respect to environmental induction of increased Na transporter affinity in teleost embryos as a mechanism of long‐term physiological adaptation to the gradual acidification of natural waters.
Evaluation of flow cytometry as a method for quantification of circulating blood cell populations in salmonid fish
Authors: Morgan J. A. W. , Pottinger T. G. , Rippon P.
Published: April 2005

Flow cytometry was used to estimate the proportions of different blood cell types in brown and rainbow trout. On the basis of forward light scatter and 90° side scatter three populations were differentiated. The relative abundance of these cells correlated with that of erythrocytc (r2= 0.994), lymphocyte plus thrombocyte(r2= 0.676) and neutrophil populations (r2= 0.571) enumerated by direct microscopy. By density gradient separation of cells, cell sorting and acridine orange staining it was confirmed that these cell types could be assigned to the populations detected. Changes in blood cell populations were monitored by flow cytometry in a group of experimental fish placed under confinement stress. Flow cytometry proved to be a rapid and reliable method for monitoring cell population dynamics in fish blood.
Routine respiration rates of Atlantic mackerel, Scomber scombrus L., and herring, Clupea harengus L., at low activity levels
Authors: Johnstone A. D. F. , Wardle C. S. , Almatar S. M.
Published: April 2005

Once adapted to the captive environment, mean minimum respiration rates were 118 mgO2 kg−1 h−1 for mackerel, body length (b.l) range 290 to 380 mm, at 11.1o C at a swimming speed of 0.6 b.l. s1 and 93 mgO2 kg−1 h1 for herring, length range 255 to 310 mm, at 9.3° C at a swimming speed of 0.3 b.l. s1.
Genetic variation in Atlantic salmon, Salmo salar L., within the Tamar catchment in south‐west England
Authors: Hurrell R. H. , Price D. J.
Published: April 2005

Electrophoretic analysis of enzymes in 383 juvenile Atlantic salmon, Salmo salar L., within the Tamar catchment (south‐west England) revealed significant genetic differences at the IDHP‐3* locus between the three tributaries studied. Aspects of temporal and spatial variation, and management policy within catchments, are discussed.
Development of the respiratory swimbladder of Pangasius sutchi
Authors: Liu W. S.
Published: April 2005

The swimbladder of Pangusius sutchi first appears on the dorsal surface of the oesophagus at about 5 days after hatching. The swimbladder has double chambers when it is separated by a medial septum at 8–10 days. Alveoli start to develop and function in air‐breathing at 12–14 days. Their number is increased by subdivision, and the respiratory portion grows towards the centre. Morphometric analysis shows that the swimbladder increases in respiratory surface, volume and surface area: volume ratio during development. On a histological basis, the development of the swimbladder is divided into three distinct periods: a blind tube, a double chamber and an alveolus period. It is characteristic that the flat epithelial cell arises from a primordial cuboidal cell and that a double capillary system is arranged in the interalveolar septa. Multilamellar bodies appear and a blood‐air barrier is established when the swimbladder becomes functional.
Empirical analysis of the influence of swimming pattern on the net energetic cost of swimming in fishes
Authors: Boisclair D. , Tang M.
Published: April 2005

We tested the hypothesis that the energetics of swimming in a flume accurately represent the costs of various spontaneous movements using empirical relationships between fish swimming costs, weight, and speed for three swimming patterns: (1) ‘forced swimming’ corresponded to movements adopted by fish forced to swim against a unidirectional current of constant velocity; (2) ‘directed swimming’ was defined as quasi‐rectilinear movements executed at relatively constant speeds in a stationary body of water and (3) ‘routine swimming’ was characterized by marked changes in swimming direction and speed. Weight and speed explained between 76% (routine swimming) and 80% (forced swimming) of net swimming cost variability. Net costs associated with different swimming patterns were compared using ratios of model predictions (swimming cost ratio; SCR) for various weight and speed combinations. Routine swimming was the most expensive swimming pattern (SCR for routine and forced swimming =6.4 to 14.0) followed by directed (SCR for directed and forced swimming =0.9 to 2.8), and forced swimming. The magnitude of the difference between the net costs of forced and spontaneous swimming increases with movement complexity and decreases as fish weight increases.
Pattern of energy allocation in the southern catfish (Silurus meridionalis)
Authors: Xie X. J. , Sun R.
Published: April 2005

Energy budgets were compiled for the southern catfish (Silurus meridionalis) under laboratory conditions at different ration size, body weights and temperatures. Though the food energy allocated among the components of the energy budget varied with changing conditions, for the fish fed maximum rations the pattern of energy allocation was independent of body weight and temperature. At the maximum ration about 60% of assimilated energy was deposited in growth and 40% spent in metabolism, indicating a higher proportion allocated to growth and a lower proportion to metabolism than is generally found in fish. This pattern of energy allocation is an energetic strategy adapted to the piscivorous lifestyle of this species.
Monitoring the feeding activity of individual fish with a demand feeding system
Authors: Brännäs E. , Alanärä A.
Published: April 2005

Feeding activity of individual Arctic charr (Salvelinus alpinus) was recorded automatically for 29 days using a demand feeding system. Each of three groups of 15 fish was kept in 1 m3 tanks, containing brackish water at 10° C. Individual biting activity was continuously monitored using a PIT‐tag (Passive Integrated Transponders) system with unique individual codes. The accuracies of the bite detection system were 91, 93.1 and 99.5% respectively, in the three tanks. In all tanks, most of the individuals (12–14) bit on the releasing trigger a few times during the first 3 days. Thereafter, one or two individuals per tank accounted for almost all of the biting activity. This pronounced shift in bite‐number distribution among individuals was probably due to the development of a dominance hierarchy, in which the dominant individuals monopolized the trigger. Growth rates appeared to be highest among high ranking fish. The implications of using demand feeding and PIT‐tag devices in feeding studies are discussed.
The distribution, density and growth of the European eel, Anguilla anguilla, in the freshwater catchment of the River Thames
Authors: Naismith I. A. , Knights B.
Published: April 2005

Improvements in water quality in the Thames Estuary since the 1960s have removed a barrier to fish migration into the Thames catchment. The extent of recolonization by the eel is examined, using data from 235 electrofished and fyke‐netted sites, compared with information on pre‐pollution distribution. Density is highest in the lower parts of the catchment and decreases significantly with increasing distance from the tidal limit. Only sparse populations are found beyond 50 km from the tidal limit and are characterized by an increasing bias towards larger, slower‐growing females. Artificial stocking is believed to be a significant factor in certain areas. The rate of recolonization has been slow and neither the annual natural recruitment nor distribution of the pre‐pollution stock of the 1800s appears to have been achieved. The future management of the stock in relation to its commercial scientific and conservation value is considered.
Salinity tolerance of two tropical fishes, Oreochromis aureus and O. niloticus. I. Biochemical and morphological changes in the gill epithelium
Authors: Avella M. , Berhaut J. , Bornancin M.
Published: April 2005

Cichlids of the genus Oreochromis are fish of economic importance in African countries. They tolerate brackish water, however, with great variations between species. In this work, two species, both from the Ivory Coast but of different origins, O. niloticus (field and laboratory strains) and O. aureus (field strain) were compared during osmotic challenges (10, 20 and 30%o salinity) in order to provide physiological support for their specific behaviour when confronted with natural hypertonic environments. Tolerance to salinity was assessed by correlated observations on gill structure, plasma sodium levels and gill Na+/K+ ATPase activity. In fresh water (FW), all fish presented a gill epithelium structure characteristic of FW stenohaline fish: no chloride cells (CC) on the lamellae and few CC on the filaments. An increase in external salinity induced the proliferation of CC on filaments, a feature typical of seawater teleosts. This change in gill structure was accompanied by an increase of gill Na+/K+ ATPase activity. In the most tolerant strains, plasma Na+ did not change, indicating successful ion regulation in the hypertonic media. With regard to potential interest of field strains in fish culture, O. aureus acclimated more easily to brackish water than O. niloticus. Interestingly, O. niloticus, kept for several generations in the laboratory, performed best in our challenge studies. Plasma Na+ levels and gill CC proliferation upon transfer to an isotonic medium may be the parameters of choice when testing these fish for their response to a salinity change.
Seasonal variation of mass, condition and gonadosomatic index in fourhorn sculpin (Myoxocephalus quadricornis) with normal and malformed vertebrae in the Gulf of Bothnia
Authors: Bengtsson Å.
Published: April 2005

It may be expected that vertehral anomaties would reduer the viability and reproductive success of fish. In the present study. the relationship of vertebral defects to body mass. Iength, age, condition, gonadosomatic index and growth in fourhorn sculpin, Myoxocephalus quadricornis, in the Gulf of Bothnia was studied. There were no differences in growth between normal and defective lish, for either males or females. While normal and defectives males were similar in age and length. defective females were older and longer than normal females. Defective males and females had a significantly greater somatic mass that normal fish. However defective females may be later than in normal fish. Hence, vertebral defects do not necessarly reduce the reproductive potential of fourhorn sculpin.
A remarkable occurrence of isopod parasitism on an armoured catfish, Microlepidogaster maculipinnis
Authors: Schaefer S. A.
Published: April 2005

Numerous specimens of the armoured catfish species, Microlepidogaster maculipinnis collected in 1979 from four sites in Paraguay, were found to be parasitized by two species of cymothoid isopods, Artystone minima and Nerocila armata. The small size differential between isopods and host catfish, high incidence of infestation, pathology and details on the frequency of oecurrence and location of parasites are described for both cymothoid species.
Spawning behaviour of a farmed escaped female Atlantic salmon (Salmo salar)
Authors: Lura H. , Barlaup B. T. , Sægrov H.
Published: April 2005

Excavation of stranded redds revealed differences in spawning behaviour between farmed and wild Atlantic salmon. The redd of a farmed fish contained more egg pockets (nine v. average of two) and fewer eggs per pocket (averages: 459 v. 707). No other pocket measures differed.
The timing of the electromyogram in the lateral myotomes of mackerel and saithe at different swimming speeds
Authors: Wardle C. S. , Videler J. J.
Published: April 2005

Electromyogram (EMG) signals from two points at about 40%L and 65%L(L= length) in the left latera1 muscle of mackerel (Scomber scombrus L.) L= 28–33 cm a nd saithe (Pollachius virens L.) L= 42–50 cm were recorded synchronously with films of steady straight swimming motions. In both species, the duration of EMG activity at both electrodes, remains a constant proportion of the tail cycle period Tat all the tail beat frequencies between 1–8 and 13 Hz. In mackerel and saithe respectively: onset of EMG activity at the front was 74%T and 77%T before the left‐most tail blade position and fronl EMG‐onset occurred 15%T and 18%T before rear onset. The duration of the EMG burst is longer at the front position (41%T and 47%T) than at the rear (25%T and 27%T), At all swimming speeds the wave of electrical activation of the muscle travelled between the two electrodes 25%L apart at a velocity between 1.5 and 1.6L T−1. Frequencies of spikes within the burst of EMG activity rose from 30–40 Hz at 2 T s−1 to 50–80 Hz at 8 T s−1. In muscle at 40%L EMG‐onset happens at phase 30° just after muscle strain at this point reaches its resting length while lengthening (360°). At 65%L EMG‐onset occurs earlier in the strain cycle‐350° just before the muscle reaches it resting length while lengthening (360°). This could represent within the length of the fish, a phase shift of up to 90° in the EMG‐onset in relation to the muscle strain cycle. These timings are discussed in relation to optimized work output and a single instant of maximum bending moment all along the left side of the body.
The role of Callionymus lyra and C. reticulates in the life cycle of Lernaeocera lusci in Belgian coastal waters (Southern Bight of the North Sea)
Authors: Van Damme P. A. , Maertens D. , Arrumm A. , Hamerlynck O. , Ollevier F.
Published: April 2005

A survey of the dragonet Callionymus lyra and the reticulated dragonet C. reticulatus from Belgian coastal waters (Southern Bight of the North Sea) in June 1991 revealed 34% of dragonets infected with 1–7 Lernaeocera lusci. This same parasite infected 9% of the reticulated dragonets (mean intensity =1). Parasite size is host‐size‐dependent. Of the parasites collected from C, lyra 64% were gravid adults (substage X), and a significant positive relationship between the number of eggs and axial length of the parasite was found. The parasites were overdispersed within the dragonet population (s2/m=1.67)
Histological and enzyme histochemical changes in the kidney of male bullhead (Cottus gobio) during the spawning period
Authors: Bucher F. , Hofer R.
Published: April 2005

Histological and enzyme histochemical studies were carried out on the excretory kidney of the male bullhead (Cottus gobio). During the spawning season striking morphofunctional changes were observed in the second proximal segment of the kidney tubule. The tubular epithelium was greatly hypertrophied, strongly basophilic and produced a PAS‐positive secretion. The enzyme histochemical pattern also changed conspicuously during this time: the alkaline phosphatase activity in the brush border was greatly reduced; the acid phosphatase and non‐specific esterase activity in the cytoplasm was distinctly elevated.
Stephanostomum lophii sp. nov. (Digenea: Acanthocolpidae), intestinal parasite of Lophius piscatorius, with reference to seasonal fluctuations of metacercariae in intermediate second hosts (Gadidae)
Authors: Quinteiro P. , Tojo J. , Núñez A. , Santamarina M. T. , Sanmartin M. L.
Published: April 2005

We describe the adult and metacercaria of a new species of digenetic trematode, Stephanostomum lophii sp. nov., an intestinal parasite of the angler fish, Lophius piscatorius. The species is distinguished from the similar Stephanostomum kovalevi by the numerous peristomial spines in the latter and from S. baccatum by the oral sucker being larger than the ventral sucker and by the fact that the principal intermediate hosts are gadids, not pleuronectids as in the case of Stephanostomum baccatum. We also report the prevalence of S. lophii metacercariae in various potential angler fish prey species caught off the coast of Galicia (NW Spain).
Karyological study of some cyprinid species from Ethiopia. The ploidy differences between large and small Barbus of Africa
Authors: Golubtsov A. S. , Krysanov E. Yu.
Published: April 2005

Chromosome sets of nine species of Barbus and a species of Varicorhinus from Ethiopia were investigated. All large Barbus (B. bynni, B. intermedius, B. ethiopicus) and V. beso are shown to have 2N =150, whereas all small Barbus (B. anema, B. kerstenii, B. paludinosus, and three unidentified (probably undescribed) species have 2N = 50. Based on the karyological data and on the published morphological data, an independent origin of small and large Barbus of Africa is suggested. The authors believe that large Barbus of Africa constitute a monophyletic group and that this group has no sister‐group relationships with any of the small Barbus of Africa.
Characterization and prevalence of pigments in the muscle of hawkfish (Cheilodactylus bergi)
Authors: Meneses M. I. , Lopez de Leon E. , Norbis W. , Lerena S. Lopez
Published: April 2005

Melanin pigment was prevalent in skeletal muscle of 338 out of 1079 Cheilodactylus bergi sampled from the Argentine‐Uruguay Common Fisheries Zone. A higher proportion of males than of females was pigmented, and only in males did that proportion increase with body length. No parasites were found in the muscle.
Karyotypes of three Garra species from Ethiopia
Authors: Krysanov E. Yu. , Golubtsov A. S.
Published: April 2005

Three cyprinid species from Ethiopia, Garra dembeensis, G. makiensis, and G. quadrimaculata, were found to be characterized by the chromosome numbers (2n) of 50 and by the arm numbers of 82, 84, and 88, respectively.
Composition of the seminal Fluid and ultrastructure of the spermatozoon of turbot (Scophthalmus maximus)
Authors: Suquet M. , Dorange G. , Omnes M. H. , Normant Y. , Le Roux A. , Fauvel C.
Published: April 2005

Mean values of the composition of the seminal fluid of 30 turbots were: osmotic pressure =306 mosml−1, pH =7–31, total protein =8.8mg ml1, Na+=133.0 mmoll1, K+=3.80mmoll−1, Cl−=129mmol l−1. The rounded nucleus, the reduced middle piece and the typical ‘9 + 2’ structure of the flagellum mean that the spermatozoon of turbot can be considered to be of a primitive type.
Food habits, feeding behaviour and impact of triploid bighead carp, Hypophthalmichthys nobilis, in experimental ponds
Authors: Opuszynski K. , Shireman J. V.
Published: April 2005

Food of sterile triploid bighead carp, Hypophthalmichthys nobilis, was examined in ponds receiving water from a hypereutrophic take in Florida. No distinctive seasonal changes in food composition were found. The fish fed selectively on Botryococcus braunii Kuetzing, a large nuisance algal species, which constituted 61% of the volume and 50% of the dry weight of the food. Zooplankton was highly selected, but constituted only 3% of the food volume because of the low zooplankton density in the ponds. The remaining proportion of food consisted mainly of blue‐green algae. Final fish biomass was low, ranging from 60 to 97 kg ha−1 in individual ponds. Low biomass was due to slow fish growth and high fish mortality. Despite low biomass, the fish lowered the ratio of blue‐green/green algae in the ponds and tended to lower phyto‐ and zooplankton abundance.
Is there a threshold size regulating seaward migration of brown trout and Atlantic salmon?
Authors: ØKland F. , Jonsson B. , Jensen A. J. , Hansen L. P.
Published: April 2005

We investigated the influence of variation in body size and growth rate on age of smolting in Atlantic salmon and brown trout in four different Norwegian rivers. In Atlantic salmon smolt ages varied between 2 and 6 years, and in brown trout between 2 and 7 years. Smolt age was negatively correlated with parr growth, and positively correlated with smolt size. Age at smolting was more variable in the two northern than the two southern rivers. Smolt sizes and ages were also more variable in brown trout than in Atlantic salmon. Based on the observed variation in smolt size and age, we reject the hypothesis that a threshold size alone regulates age at smolting. Within populations smolt age depends on growth rate so that fast‐growing parr smolted younger and smaller than slow‐growing parr. We hypothesize that smolt size and age is a trade‐off between expected benefits and costs imposed by differences in individual growth rate.
Parasites of lake sturgeon, Acipenser fulvescens (Chondrostei: Acipenseridae), from central Canada
Authors: Choudhury A. , Dick T. A.
Published: April 2005

Nineteen species of parasites were recovered from lake sturgeon, Acipenser fulvescens, from four major waterways of Central Canada; the Saskatchewan, Nelson, Winnipeg and Rainy River systems, Twelve of these are new host records. Host specific parasites, Crepidostomum auriculatum, Diclybothrium armatum, Spinitectus acipenseri and Truttaedacnitis clitellarius, forming the core parasite species, were recovered with the highest prevalence (≥70%) and were most widely distributed. Polypodium hydriforme was recovered from only stage IV sturgeon oocytes. With the exception of Pomphorhynchus bulbocolli, prevalence and intensity of endohelminth infections were not correlated with sex or age of host but the distribution of non host‐specific parasites among sampling sites was determined by the type and relative abundance of food items consumed. The parasites of lake sturgeon are closely correlated to its diet and the species of parasites recovered are more similar to those of freshwater sturgeon in Eurasia than to other species of Acipenser in North America. The present parasite community of lake sturgeon appears to have been shaped by three major factors; the presence of core parasite species which predates geographic isolation, a benthic freshwater diet which has reshaped the parasite community to one comprising freshwater species and a long association with freshwater habitats which is reflected in the reproductive isolation of the lake sturgeon and lastly, the establishment of a host‐specific parasite, Spinitectus acipenseri.
A comparison of the mouth morphology of three co‐occurring species of atherinid
Authors: Humphries P.
Published: April 2005

The mouth morphology of three species of atherinids, which feed at different levels in the water column (benthos, plankton and water surface) were compared. These three species, which all grow to less than 100 mm in length, inhabit the shallows (<2m) of Wilson Inlet, a temperate south‐western Australian estuary. The species could be distinguished primarily on the basis of the extent to which they can protrude their jaws. Thus, whereas Leptatherina presbyteroides feeds highest in the water column, including at the water surface on terrestrial insects, and has the most protrusible jaws, Atherinosonia elongata feeds predominantly at or near the benthos and has the least protrusible jaws. Leptatherina wallacei, which ingests prey from the plankton and near the benthos, is intermediate in the degree to which it can protrude its jaws. Other characters of the three species which are associated with feeding, such as the number of gill rakers and the size of teeth, show consistent trends with the degree of jaw protrusion in relation to the type of prey consumed.
Landolt's club in the retina of catfish, Heteropneustes fossilis: a new finding in Teleostei
Authors: Narayanan K. , Khan A. A.
Published: April 2005

The visual cells in the retina of the freshwater catfish, Heteropneustes fossilis comprise rods, long single cones, short single cones and Landolt's clubs.
Arterial Po2, acid‐base status, and red cell nucleoside triphosphates in rainbow trout transferred from fresh water to 20‰ sea water
Authors: Larsen B. K. , Jensen F. B.
Published: April 2005

Transfer of rainbow trout from fresh water to 20‰ sea water decreased dorsal aortic Po2 from 90 to 60 mmHg within 1 h. Arterial Po2 was depressed for 24 h before it returned to control values. The internal hypoxia rapidly reduced the red cell nucleoside triphosphate content, suggesting prompt regulation of blood O2 affinity. The extracellular acid‐base status changed towards a small mixed metabolic and respiratory acidosis.
Confirmation of the presence of schelly, Coregonus lavaretus, in Brotherswater, U.K.
Authors: Winfield I. J. , Fletcher J. M. , Cubby P. R.
Published: April 2005

The presence of the nationally‐rare schelly. Coregonus lavaretus, in Brotherswater, a small lake in the English Lake District, was confirmed in the summer of 1992. However, pronounced deepwater oxygen depletion may pose a threat to the continued survival of this seventh U.K. population.
Abundance‐depth relationship, condition factor and adaptive value of zooplanktophagy for red bandfish, Cepola macrophthalma
Authors: Stergiou K. I.
Published: April 2005

The abundance‐depth relationship, condition factor and feeding of red bandfish, Cepola macrophthalma, were studied from trawl samples collected seasonally in 1986–1988 in the western Aegean Sea (Greece). The red bandfish comprised numerically 1.4% of the total fish catch. Its abundance ranged between 0 and 1362 individuals/h (mean = 57.7 individuals/h, +s.d.= 124.7). The relationship between the natural logarithm of the mean number of individuals/h, ln[(n/h) + 1], and depth, D in m, was found to be described by the following quadratic model:

image

Feeding intensity and condition factor were significantly (P <0.05) lower in December and March, when annuli formation takes place, and significantly higher (<0.05) in June and/or September when reproduction takes place. The red bandfish is a zooplankton predator. Copepods and euphausids dominated by far its diet and made up 60.4% and 31.1 % by number, respectively. The remainder of the diet was shared by cladocerans, decapods, mysids, chaetognaths, amphipods, fish larvae and decapod larvae. Red bandfish has probably evolved a zooplanktophagus habitat because, by providing a relatively abundant food supply, it will neither limit its high linear growth in the first 4–5 years of life nor increase its predatory induced mortality.
The influence of gradual water acidification on the acid/base status and plasma hormone levels in carp
Authors: van Dijk P. L. M. , van den Thillart G. E. E. J. M. , Balm P. , Bonga S. Wendelaar
Published: April 2005

Carp (Cyprinus carpio) fitted with arterial catheters were subjected to gradual water acidification (from pH 7.6 to 4.0 in 4 h), and then monitored for 48 h. The measured blood parameters showed little or no disturbance; there was no ionoregulatory disturbance, no hyperglycemia, increase in plasma lactate, hypoxemia, or swelling of red blood cells. Only a slight transient decrease of plasma pH was found. Plasma catecholamine levels remained at control level. The plasma cortisol concentration showed a transient increase, and was returned to the control level 24 h after beginning water acidification.

Our results contrast with literature data on carp where exposure to pH 4.0 caused severe blood electrolyte disturbance. We conclude that the rate of water acidification (gradual in our study as compared to acute in the literature) rather than the pH level itself determines the early effects of water acidification.
Is there a synergistic effect between steady‐state exercise and water acidification in carp?
Authors: van Dijk P. L. M. , Van den Thillart G. E. E. J. M. , Bonga S. E. Wendelaar
Published: April 2005

Carp (Cyprinus carpio) fitted with arterial catheters were trained to swim in a swim tunnel. While constantly swimming at two body lengths per second, they were subjected to gradual water acidification (from pH 7–6 to 40 in 4 h), and monitored subsequently over 24 h. It was hypothesized that exercise would expose the gills to a larger extent and that conseq uently the effect of water acidification would be greater in exercising than in resting carp. In contrast to our earlier study with resting carp we found a constant dedine of plasma pH, and of plasma Na+ and Cl concentration, indicating ionoregulatory failure. While plasma catecholamincs remained at control levels, the plasma cortisol showed a three‐ to four‐fold increase over the first 7 h. This was followed by a slow decline. We conclude that there is a synergistic effect between moderate exercise and gradual water acidification.
Behavioural responses of glass eels (Anguilla anguilla) towards amino acids
Authors: Sola C. , Spampanato A. , Tosi L.
Published: April 2005

The behavioural responses of glass eels of Anguilla anguilla towards amino acids were investigated by binary choice experiments testing different concentrations of 14 L‐amino acids in fresh water and salt water. Glass eels responded to solutions of individual amino acids down to a concentration of 10−8M, 10−9m. Media of different salinities influenced the responses. In freshwater, gln and thr were strongly attractive; asn, ala, met, glu and ile induced significant avoidance; gly elicited multimodal reactions depending on concentrations; his, lys, phe, val, leu and asp hardly influenced behaviour. In salt water, only gly, asn and lys significantly influenced the behaviour of the glass eels.
The influence of light on egg buoyancy and hatching rate of the walleye pollock, Theragra chalcogramma
Authors: Olla B. L. , Davis M. W.
Published: April 2005

Changes in buoyancy in fertilized bathypelagic eggs of the walleye pollock, Theragra chalcogramma, collected from Shelikof Strait in the Gulf of Alaska were measured under controlled laboratory conditions in density gradient columns from 90 h post–fertilization through hatching. Eggs were incubated at 6° C and exposed to either diel light or constant dark. Eggs held under diel light conditions became more dense than eggs under constant dark beginning <10 h after exposure to light and remained so until 12 h before hatching. Eggs held under constant dark then became more dense than those under diel light. Hatching of eggs under both conditions began at the same time but eggs under diel light showed a delayed hatching rate. Light–induced changes in egg density indicate the ability of walleye pollock eggs to respond to external stimuli and thereby alter their position in the water column in an ecologically meaningful way.