bluuebunny/crossref_metadata_2025 huggingface dataset:
Protein synthesis, nitrogen excretion and long‐term growth of juvenile Pleuronectes flesus
Authors: Carter C. G. , Houlihan D. F. , Owen S. F.
Published: April 2005

This study aimed to measure protein synthesis using a stable isotope method, investigate protein‐nitrogen flux in a flatfish Pleuronectes flesus, and use the data to test the hypothesis that individual differences in growth efficiency were related to individual differences in protein‐nitrogen flux mediated through differences in protein synthesis and degradation. Three measurements of protein‐nitrogen flux via consumption, protein synthesis and nitrogenous excretion were made for individual flounder during a 212‐day period and fractional rates of protein‐nitrogen flux were scaled for a 50–g flounder to provide mean values for protein consumption (2·11 ± 0·21% day−1), protein synthesis (2·08±0·23% day−1), protein growth (0·71±0·06% day−1) and protein degradation (1·37±0·24% day−1). Mean rates of nitrogenous excretion were 0·142 mg N g−1 day−1 and 0·047 mg N g−1 day−1 for ammonia and urea, respectively. Individual flounder had different protein growth efficiencies and this was correlated negatively and significantly with mean rates of protein synthesis (r ‐ 0·70; P<0·05) and degradation (r ‐ 0·67; P< 0·05) and correlated positively and significantly with the efficiency of retaining synthesized protein (r+0·63, P<0·05). This supported the proposed hypothesis that flounder which grow more efficiently achieve this through adopting a low protein turnover strategy.
Epidemiology of Renibacterium salmoninarum in wild Arctic charr and brown trout in Iceland
Authors: Jónsdóttir H. , Malmquist H. J. , Snorrason S. S. , Gudbergsson G. , Gudmundsdóttir S.
Published: April 2005

Renibacterium salmoninarum (Rs) is common in wild Arctic charr Salvelinus alpinus and brown trout Salmo trutta in Iceland. Of 22 charr and nine trout populations none were free of Rs antigens. In two charr populations only one fish exceeded the Rs antigen detection limit and in one of these cases the ELISA value was within uncertainty limits of the infection criterion. Mean prevalence of infection was 46% for Arctic charr (range: 3–100%) and 35% for brown trout (range: 6–81%). No infected fish showed gross pathological signs of bacterial kidney disease (BKD). The ubiquity and high prevalences of infection indicated that the bacterium has been endemic for a long time, and is probably a normal, low density resident in the fish. A lack of correlation in mean intensity of Rs antigen and prevalence of infection between sympatricpopulations of Arctic charr and brown trout suggests that the dynamics of infection and internal proliferation of bacteria can be quite independent in the two species even if they live in the same lake. Rs intensity and its coefficient of variation decreased with age in older fish, suggesting a connection between Rs intensity and host mortality. However, this can be caused by other ecological factors that decrease survival, especially low food availability, which simultaneously increase the susceptibility to Rs infection and internal proliferation.
Effects of overripening on spawning behaviour and reproductive success of Atlantic salmon females spawning in a controlled flow channel
Authors: de Gaudemar B. , Beall E.
Published: April 2005

The influence of overripening on salmonid egg quality has often been described in artificial breeding. However, no information exists on the impact of this factor on fish reproducing naturally, although it is likely to be critical, especially in disturbed environments. Pairs of Atlantic salmon in which the size of the male and the female was evenly matched were released in a spawning channel from 1 to 12 days after ovulation. Handling did not affect egg quality. Overripening had a negative effect on egg viability. Egg mortality, infertility and malformations increased with the number of days after ovulation. In females which had just matured, 16·7% of their recovered eggs were dead, 3·1% were unfertilized and 1·7% were malformed, as compared to 25·4, 9·7 and 5·4%, respectively, in females that had been mature for at least a week. Overripening played a role in both female spawning behaviour and capacity to spawn, as females which had been mature for over a week released their eggs more quickly while they retained more ova in their abdominal cavity than early spawning females. Thus, in studies of reproductive behaviour and in particular of sexual selection, it is critical to take into account the maturation status of females since the duration of spawning activity is used by various authors to determine female sexual motivation. Alternatively, overripening may decrease the female selectivity for mates.
Testicular maturation and regression in the common snook
Authors: Grier H. J. , Taylor R. G.
Published: April 2005

During the annual reproductive cycle, the lobular testis of Centropomus undecimalis undergoes height, width, and morphological changes which reflect five reproductive classes: regressed; early, mid‐, and late maturation; and regression. Histological criteria, particularly differences between continuous and discontinuous germinal epithelia, are used to distinguish these five classes, even though they are only reference points within the annual gonadal cycle. A mechanism for lobular growth during early, mid‐, and late maturation is presented; and it is hypothesized that a permanent germinal epithelium first appeared in the fishes. Throughout the year, periodic acid‐Schiff‐positive macro‐melanophage centres and PAS‐positive granulocytes are observed in the testis. They are most abundant after the breeding season, and they may be involved in focal tissue degradation.
Genetic comparison of salmon from the White Sea and north‐western Atlantic Ocean
Authors: Skaala Ø. , Makhrov A. A. , Karlsen T. , Jørstad K. E. , Altukhov Y. P. , Politov D. V. , Kuzishin K. V. , Novikov G. G.
Published: April 2005

Samples of salmon Salmo salar from the River Kachkovka and the River Nilma in northern Russia were analysed by starch gel electrophoresis and compared to three Norwegian stocks, the Neiden river in northern Norway and Øyreselv and Hopselv rivers on the west coast. The comparison included the following polymorphic loci: AAT‐4*, IDDH‐2*, IDHP‐3*, MDH‐ 3,4*, MEP‐2*, ESTD* as well as the newly discovered polymorphic loci FBALD‐3* and TPI‐3*. Samples were run side by side on gels, and the alleles found in the Russian stocks were the same as those found in the Norwegian stocks, although the electrophoretic methods used lead to differences in designations of alleles. A polymorphism in ESTD* which involves a slow allele was commonly observed in the three northern populations of the Nilma, Kachkovka and Neiden rivers. This allele was absent in the other Norwegian stocks and in a major brood stock of farmed salmon in Norway. The IDHP‐3*116allele was found in unusually high frequencies in the northern populations. Thus, the variability observed at these two loci indicates a barrier to gene flow between the northern salmon stocks and the more southern stocks in the East Atlantic area.
Genetic divergence in Greek populations of the genus Leuciscus and its evolutionary and biogeographical implications
Authors: Doadrio I. , Carmona J. A.
Published: April 2005

In 23 populations of Greek Leuciscus (Squalius), the percentage of polymorphic allozyme loci ranged between 0·034 and 0·379 (P=0·19) and expected heterozygosity was 0·011–0·166 (He=0·067). Current taxonomy is confusing and does not correspond to genetic data that support the presence in Greece of at least seven different species: L. cephalus, L. peloponnensis, L. prespensis, L. moreoticus, L. borysthenicus, L. keadicus and Leuciscus sp. from Euboea Island. The maximum Nei modified genetic distance was found among L. keadicus and the rest of subgenus Squalius populations D* Nei=0·446–0·705). Accepting the molecular clock hypothesis, speciation for the genus Leuciscus in Greece must have occurred during the Cenozoic period (between the Middle Miocene and the Later Pliocene). The two main biogeographical events causing speciation on mainland Greece were the Uplift of the Pindic cordillera and the isolation of the southern part of Peloponnesus. The faunistic composition of the lakes studied, in which new taxa are reconsidered, suggests the same faunistic origin in the Early Pliocene for Lakes Prespa and Stymphalia and a younger one in the Late Pliocene for Lake Trichonis. Euboea Island was not a zoogeographical unit during the Cenozoic. The isolation of all the freshwater fish fauna of Euboea has occurred since the Pliocene. The biogeographical model proposed here differs from classical hypotheses in considering of lesser importance the dispersion of L. cephalus on the Greek mainland during the Neogene and Quaternary.
Effects of age and body size on gonadal development of Atlantic sturgeon
Authors: Van Eenennaam J. P. , Doroshov S. I.
Published: April 2005

Three hundred and five Atlantic sturgeon caught in the Hudson River and Hudson Bight were examined for age, body size and gonadal development (histology). Sampled fish ranged in age from 1·5 to 43 years and fork length (LF) 48–244 cm, and included 144 females and 161 males. All young sturgeon (age 1·5–4 years) caught in the river had sexually differentiated gonads. Age and size distributions of subadults and adults at different stages of gametogenesis were sex‐specific and conformed with von Bertalanffy growth curves. Males mature faster and at a younger age compared to the females. Females with mid‐vitellogenic ovaries were not found and their absence may be related to fishing gear selectivity or out‐migration into the ocean during ovarian recrudescence. Mature males and females caught during the spring spawning migration into the Hudson River, ranged in age from 12 to 19 and from 14 to 43 years, and LF 117–185 and 173–244 cm, respectively. Individual fecundity and diameter of fully grown ovarian follicles increased with age and body size, but this increase was dampened in older females. Three hermaphroditic fish were found and all exhibited sparse pre‐vitellogenic ovarian follicles embedded in normally developing testicular tissue.
A revision of the akysid catfish genus Breitensteinia Steindachner with descriptions of two new species
Authors: Ng H. H. , Siebert D. J.
Published: April 2005

The highly specialized akysid catfish genusBreitensteiniais revised; two new species are described.Breitensteinia cessatoris described from Sumatra and western Borneo. It can be distinguished by its large, wide‐set eyes and evenly scattered brown spots on the dorsal and pectoral fins.Breitensteinia hypselurusis described from western Borneo. It can be distinguished by its relatively tall neural spines on caudal vertebrae, smooth posterior edge of dorsal spine, short caudal peduncle, and fewer vertebrae.Breitensteinia insignisis sexually dimorphic.
Temperature‐induced changes of survival, development and yolk partitioning in Chondrostoma nasus
Authors: Kamler E. , Keckei H. , Bauer‐Nemeschkal E.
Published: April 2005

Fertilized Chondrostoma nasus eggs were incubated at 10, 13, 16 and 19° C until full resorption of the yolk sac. High survival was observed at 10–16° C (89–92% at the onset of external feeding), whereas at 19) C survival was depressed (76%). The time at which 5, 50 and 95% of individuals had hatched, filled the swim bladder, ingested the first food and fully resorbed the yolk sac was determined. An increase in temperature accelerated development and made it more synchronous. Within the period from fertilization to hatching embryonic development was theoretically arrested (t0 dev) at 8·8° C, and growth was arrested (t0gr) at 8·86° C. For the whole endogenous feeding period (from fertilization to full yolk resorption) the amount of matter transformed into tissue was temperature independent between 10° and 19° C. Respiration increased exponentially with age; the respiration increase was faster at higher temperatures, but, in general, metabolic expenditures of C. nasus were low. As a consequence, the efficiency of utilizing yolk energy for growth was high as compared with other fish species (57% during the whole endogenous feeding period); it was temperature independent. However, time was used less efficiently at low temperatures, increasing a risk of predation. Within the endogenous feeding period a shift from lower to higher temperatures for optimal yolk utilization efficiency was observed. The temperatures optimal for survival and energetic performance seem to be 13–16° C for egg incubation and 15–18° C for rearing of yolk‐feeding larvae. Chondrostoma nasus is a potential candidate for aquaculture for restocking purposes.
The occurrence and pathological effects of Stephanostomum tenue (Digenea: Acanthocolpidae) metacercariae in elvers of the American eel
Authors: Oliveira K. , Campbell R. A.
Published: April 2005

This is the first record of the American eel, Anguilla rostrata, as an intermediate host of Stephanostomum tenue. Metacercariae occurred most frequently in the pericardial cavity of elvers where they often produce severe distention of the thoracic region and impeded swimming.
Further examination of female preference for vertical bars in swordtails: preference for ‘no bars’ in a species without bars
Authors: Morris M. R.
Published: April 2005

Xiphophorus pygmaeus males do not have a vertical bar pigment pattern and so female preference for the bars was determined by giving females a choice between pairs of X. multilineatus males without bars (all bars removed by freeze‐branding) and with bars (freeze‐branded between the bars). Female X. pygmaeus had a significant preference for male X. multilineatus without bars over males with bars, and this preference was significantly different from the preference for bars detected in X. nigrensis and X. multilineatus. The implications of the results are discussed in regard to models for the evolution of female preference.
Fishery‐induced changes in a marine ecosystem: insight from models of the Gulf of Thailand
Authors: Christensen V.
Published: April 2005

Two mass‐balance trophic models are constructed to describe the Gulf of Thailand ecosystem (10–50 m depth): one model pertains to the initial phase of fisheries development, and the other to when the resources were severely depleted. The two phases are compared, and changes brought about by fishing discussed. A dynamic simulation model, Ecosim, is then used successfully to reproduce the 1980 state of the fishery based on the 1963 model and the development in catches. In addition the 1980 model is used to predict how the ecosystem groups may bounce back following marked reduction in fishing pressure. Finally, the 1963 model is used to study alternative scenarios for how the fisheries development could take place, notably the effect of exploiting only the resources of larger species. The study validates that the Ecosim model can be used to predict ecosystem level changes following changes in fishing pressure, therefore fishing induced changes can to a large extent explain the changes in ecosystem pools and fluxes observed over time.
Trophic models of protected and unprotected coral reef ecosystems in the South of the Mexican Caribbean
Authors: Arias‐González J. E.
Published: April 2005

General models of the energy flow of the back reef, reef front and slope zones of three coral reef complexes in the Mexican Caribbean are presented. The number of fish species registered varied considerably between reefs with a maximum found on the Mahahual reef slope. Generally, the maximum number of fish species and biomass were registered on the reef slope and the minimum on the back reefs. The greatest species number and flow diversity were obtained in the Mahahual reef. The individuals recorded for the fish feeders were also of greater size in the Mahahual reef. Maximum activity and biomass were found in the deeper Boca Paila and Tampalam habitats. The production and biomass trophic ratios used in this work were shown to be indicators of trophic tendencies of reef fish. However, the relative differences between piscivorous, carnivorous, herbivorous and zooplankton feeder fishes were not evident, but there were marked differences between biomass or production in each trophic group. Preliminary analysis suggests differences in trophic structure and energy flow between semi‐protected and unprotected areas. The comparative analysis of this nested set of models using trophic macrodescriptors may provide a useful index of anthropogenic impacts in coral reef ecosystems.
Variation in posing behaviour among fish species visiting cleaning stations
Authors: Côté I. M. , Arnal C. , Reynolds J. D.
Published: April 2005

The adaptive significance of posing behaviour by fish visiting cleaning stations on a Barbadian fringing reef was investigated. The probability of a visitor being cleaned by cleaning gobies (Elacatinusspp.) was significantly higher after posing than after failing to pose upon arrival at a cleaning station. Despite this, not all visitors posed, and there was much variation among species in tendency to pose. This interspecific variation was not related to the probability of being cleaned, either after posing or after failing to pose, nor was it related to trophic level or fish total length. The latter was true both for cross‐species analyses and phylogenetically independent contrasts. A cost‐benefit model is proposed to understand interspecific variation in posing behaviour, which considers both decisions by clients and by cleaners. As well as explaining the results, this may reconcile differences among anecdotal and experimental observations from previous studies.
Effects of seasonality and fish movement on tropical river food webs
Authors: Winemiller K. O. , Jepsen D. B.
Published: April 2005

Tropical rivers and their associated floodplain habitats are dynamic habitat mosaics to which fishes are challenged to respond in an adaptive manner. Migratory fishes create linkages among food webs that are partitioned along a nested hierarchy of spatial scales. Such linkages are examined across a hierarchy of spatio‐temporal scales, ranging from small streams to entire drainage basins, for rivers in South America and Africa. Migratory herbivorous fishes originating from eutrophic, productive ecosystems may subsidize resident predators of oligotrophic river ecosystems, which may result in cascading direct and indirect Effects on other species in local food webs. Successful management of many of the most important stocks of tropical river fishes requires conceptual models of how fish movement influences food web structure and dynamics.
Effect of hydrogen sulphide on liver somatic index and Fulton's condition factor in Mystus nemurus
Authors: Hoque M. T. , Yusoff F. M. , Law T. , Syed M. A.
Published: April 2005

The growth rate and liver somatic index were significantly (P<0.05) lower in Mystus nemurus exposed to hydrogen sulphide compared to controls. These differences increased with corresponding increases in hydrogen sulphide concentrations. No significant differences (P >0.05) in Fulton's condition factor were detected between the exposed fish and the controls. The results revealed that liver somatic index is a more sensitive indicator of hydrogen sulphide toxicity compared to Fulton's condition factor.
Ovarian structure and batch fecundity in Lophiomus setigerus
Authors: Yoneda M. , Tokimura M. , Fujita H. , Takeshita N. , Takeshita K. , Matsuyama M. , Matsuura S.
Published: April 2005

The ovarian structure and batch fecundity of anglerfish Lophiomus setigerus were examined from specimens collected in the East China Sea during March 1991 to September 1995. The right and left ovarian lobes were connected at their posterior ends. Stalk‐like ovigerous lamellae protruded from the ovarian wall. During the spawning season, gelatinous material was secreted from the epithelia of both the ovigerous lamellae and ovarian wall, and these epithelia showed morphological changes accompanying the ovarian maturation cycle. Tertiary yolk, migratory nucleus, and mature stage oocytes occurred in the ovaries between May and November, when females with postovulatory follicles and developing vitellogenic oocytes were collected also. These results suggested an extended spawning season during which females undergo repeated spawnings. When the most advanced oocytes attained the secondary yolk stage, they formed a batch that separated from the adjacent group of smaller oocytes. Batch fecundity (F) in 20 females with secondary yolk stage ovaries was related to total length (LT, mm) as F= 556.2 LT1.157 (300≤LT≤396).
Morphological variation between red mullet populations in Greece
Authors: Mamuris Z. , Apostolidis P. , Panagiotaki P. , Theodorou A. J. , Triantaphyllidisdir C.
Published: April 2005

Morphometric variation in 15 characters of the red mullet Mullus barbatus samples from seven Greek localities was examined using multivariate analysis. ANOVA, stepwise discriminant analysis and cluster analysis revealed a rather high morphological variability between the populations studied. The discriminant analysis revealed that about 80% of the examined fish could be correctly classified into the seven areas. This variability could be explained in terms of genetic structuring of the populations and/or environmental conditions prevailing in each geographic area in combination with fish migration and egg/larvae transportation from one area to another. The results suggest that multivariate analysis when combined with other important biological parameters of red mullet may have important implications for the management of the Greek demersal fish resources.
Genetic changes in an Atlantic salmon population resulting from escaped juvenile farm salmon
Authors: Clifford S. L. , McGinnity P. , Ferguson A.
Published: April 2005

The study was undertaken on three adjacent rivers in NW Ireland, on one of which an Atlantic salmon Salmo salar freshwater juvenile rearing unit is situated. Two markers which distinguished farm and wild populations were used. An Ava II‐B RFLP in the ND1 region of mtDNA was at a frequency of 0.58 in the farm strain but absent in the wild populations. Allele E at minisatellite locus Ssa‐ A45/2/l was at a frequency of 0.91 in farm samples, but at a maximum of 0.41 in the populations in the two rivers adjacent to the one with the juvenile rearing unit. The farm strain showed a significant reduction in mean heterozygosity (0.281 ± 0.057), over three minisatellite loci examined, compared to wild samples (0.532 ± 0.063). The occurrence of farm genotypes and the independent occurrence of mtDNA and minisatellite markers in several parr samples from the river indicated that escaped juvenile salmon completed their life cycle, bred and interbred with native fish, upon their return to the river. Escaped fish homed accurately, as adults, to the site of escape, i.e. the area adjacent to the hatchery outflow in the upstream part of the river. Breeding of males in the lower part of the river was also indicated but this could have been due to mature male parr which had moved downstream. The return of adults of farm origin to the river to breed was indicated by the presence of the Ava II‐B haplotype in adults netted in the estuary.
Plasma concentrations of ovarian steroids in relation to oocyte final maturation and ovulation in female plaice sampled at sea
Authors: Scott P. , Witthames P. R. , Turner R. J. , Canario A. V. M.
Published: April 2005

Blood plasma concentrations of free 17β‐oestradiol, free testosterone and glucuronidated testosterone were strongly positively related to the percentage of vitellogenic oocytes remaining in the ovaries of plaice Pleuronectes platessa caught at sea–being at their highest in pre‐spawning (stage IV) females (i.e. those in which the oocytes were close to fully grown, but had not yet entered the stage of final maturation). In contrast, the concentrations of free and sulphated 17,20β‐P, 3αaL,17, 20β‐P‐5β, and 3α,17,21‐P‐5β were at their lowest in stage IV females. Free 17,20β‐P (the putative maturation‐inducing steroid) became only slightly elevated (less than twofold) during spawning (i.e. in stage V and VI females with hydrated and/or ovulated eggs). Sulphated 17,20β‐P and 3α,17,21‐P‐5β became slightly more elevated (three‐ to fourfold). However, sulphated 3α, 17,20β‐P‐5β concentrations increased 30‐fold and were at their highest in fish in which only 40% of vitellogenic oocytes remained in the ovaries. Sulphated 17,20β‐P, 3α, 17, 20β‐P‐5β and 3α,17,21‐P‐5β concentrations were significantly positively related to hyaline oocyte batch size; and sulphated 17,20β‐P and sulphated 3α, 17,20β‐P‐5β were significantly negatively related to the degree of hydration of the hyaline oocytes. None of the steroid concentrations, however, was related to the time of capture. More ovulated females were found in the afternoon than at any other time of the day.
Discrimination between high and low repetition rates of ultrasonic pulses by the cod
Authors: Astrup J. , Møhl B.
Published: April 2005

Cod were trained to detect a shift in the repetition rate of intense ultrasonic pulses (approximately 210 dB re 1 μPa). For cod exposed to predation by toothed whales, this ability may provide information to guide evasive manoeuvres.
Rod opsin sequence in the John Dory: further evidence for the spectral tuning of rhodopsin
Authors: Archer S. N. , Hirano J.
Published: April 2005

The opsin from the John Dory Zeus faber rod visual pigment (maximum spectral sensitivity =492 nm) was cloned and sequenced. Comparison of the John Dory rod opsin sequence with those from other fish with blue‐shifted scotopic spectral sensitivity provides further evidence for the spectral tuning of this group of visual pigments.
Growth and production of the dominant pelagic fish, Acanthobrama terraesanctae, in subtropical Lake Kinneret, Israel
Authors: Ostrovsky I. , Walline P.
Published: April 2005

Acanthobrama terraesanctae (local name lavnun), an endemic planktivorous cyprinid, dominates total fish numbers (>80%) in Lake Kinneret, and may have a significant top‐down impact on the lake ecosystem. The length of young‐of‐the‐year fish calculated from the von Bertalanffy equation agreed with field observations of juvenile growth. An unusual bi‐modal length‐frequency distribution observed in May 1993 provided additional help in age identification. Males grew more slowly than females and reached a lower maximum length. Total mortality coefficients (exponents) of males and females >12 cm (minimal legal size of fish in the catch) were similar (c. 1·52). An average cohort reaches maximum biomass during its second year. Maximum production is created at the end of the second year. The production: biomass ratio of the population was 1·16, and 36% of total lavnun standing stock was taken by fishing. From the late 1980s to early 1990s, when standing stock and population structure were stable, the average harvest of 1000 t was consistent with a total lavnun biomass of 2800 t, which constitutes 50–70% of the total fish stock measured acoustically in the lake. Such a biomass could be sustained by the known production of zooplankton. Absence of verified growth data for lavnun contributed to the collapse of the fishery in 1993, because it hampered timely revision of fishery policy in response to the drastic changes in the lavnun stock in 1992.
Sibling cannibalism among juvenile vundu under controlled conditions. I. Cannibalistic behaviour, prey selection and prey size selectivity
Authors: Baras E.
Published: April 2005

Sibling cannibalism among vundu Heterobranchus longifilis larvae started at the age of 4 days, with the prey caught tail‐first then swallowed up to the head, which was eventually discarded (type I cannibalism). At 17 days old, this type of cannibalism vanished and was replaced by the ingestion of the whole prey (type II cannibalism), which could only be exerted by predators six times as heavy as their prey. Type II cannibalism consisted of a seemingly opportunistic ambush attack by a formerly passive predator towards a disorientated prey. It required no preliminary aggression or chase, or even contact with the prey, suggesting that the attack was not mediated by the tactile sense, and that cannibalism was independent of aggressive behaviour. When alternative food resources (formulated feed, live tilapia prey) were available, the intensity of cannibalism decreased but pellet‐eaters or tilapia predators always achieved lower growth rates than those feeding on conspecifics, suggesting that cannibalism was the most advantageous foraging tactic. Losses to cannibalism among populations of 30‐day old juvenile vundu with an initial ratio of 4% of cannibals were as high as 75·5–79·9% over 15 days. Predation peaked during the first days (up to 2·8 prey C−1 day−1), then vanished progressively as surviving prey grew faster than cannibals and escaped their predation. Cannibals preferred consuming the largest prey available with respect to the logistics of cannibalism (body weight ratio of 6·0). This preference for large prey was interpreted both as a foraging tactic aiming to maximize the energetic return, and as foraging strategy enabling the cannibals to exploit their prey as long as possible. Based on these data, comprehensive models of the impact of cannibalism on vundu populations were developed.
Sibling cannibalism among juvenile vundu under controlled conditions. II. Effect of body weight and environmental variables on the periodicity and intensity of type II cannibalism
Authors: Baras E. , Tissier F. , Philippart J.‐C. , Mélard C.
Published: April 2005

Cannibalism among starved groups of juvenile (19–48 days old) vundu catfish Heterobranchus longifilis was 66·5% nocturnal, and its impact under modified day length was proportional to the duration of the dark phase. Shallow depth and high population density decreased the intensity of cannibalism, whereas low density and deeper environments had an opposite effect. The presence of refuges had no significant effect on cannibalism. The maintenance (Rmaint) and maximum (Rmax) daily food rations (% day−1) of cannibals feeding on live prey were modelled as Rmaint=3·899 WC0·327 (r2=0·684; d.f.=31), and Rmax=49.545 WC0·321 (r2=0·999; d.f.=5), where WC was the body weight of the cannibal (g). The latter model indicated that the impact of a cannibal on a population decreased by a 20% margin each time the cannibal doubled its body weight, and suggested that cannibalism among vundu would become insignificant for cannibals heavier than 30 g. The significance of these findings is discussed within the contexts of vundu aquaculture and of general, conceptual models of the dynamics of cannibalism among fishes.
Functional implications of early sexual growth dimorphism in vundu
Authors: Baras E.
Published: April 2005

Female juvenile vundu Heterobranchus longifilis outweighed males by > 60% (P < 0·0001) margins when aged 142 or 177 days. Not only did females grow faster (P=0·0494) than males during the experiment, but they also outweighed them by a 38·5% margin at the start of the experiment (86 days: P=0·0109). Sexual growth dimorphism (SGD) was estimated as having arisen at 15 ± 10 days. Vundu aquaculture could be improved substantially by monosex female rearing. Because the modelled emergence of SGD corresponded precisely with the start of type II cannibalism, it was suggested that cannibalism among juvenile vundu be exerted essentially by females, and might have different impacts on faster‐growing females and slower‐growing males.
Diversity of intestinal helminth communities of carp from six lakes in the flood plain of the Yangtze River, China
Authors: Nie P. , Yao W. J. , Gao Q. , Wang G. T. , Zhang Y. A.
Published: April 2005

The infra‐ and component communities of intestinal helminths of carp Cyprinus carpio were investigated in six lakes in the flood plain of the lower and middle reaches of the Yangtze River, China. Eight species of helminth parasites were recorded. The intestinal helminth communities were species rich in Niushan and Tonghu lakes where the digenean Asymphylodora japonica was the dominant species, whereas in Qinggang and Yanglan lakes a species‐poor helminth community had only one species, Khawia sinensis. The degree of similarity within localities was highest in Qinggang and Yanglan lakes, and was high between communities where K. sinensis was the dominant species. The rich composition of these helminth communities may be because China is the heartland for carp while the poor helminth composition of those in Qinggang and Yanglan lakes may reflect the poor fauna there. It is suggested that species compositions of intestinal helminth communities of carp may be diversified in lakes in the flood plain of the Yangtze River.
Biochemical genetic differentiation between Pomatoschistus marmoratus and P. tortonesei
Authors: Arculeo M. , Mauro A. , Lo Brutto S. , Mirto S. , Cammarata M. , Mazzola A. , Parrinello N.
Published: April 2005

Several diagnostic genetic markers were identified in Pomatoschistus marmoratus and P. tortonesei using polyacrylamide gel electrophoresis (PAGE) of allozymes. Twenty‐one loci were resolved, including the electrophoretic pattern of muscle proteins. The MDH*, PGM‐,2*, EST‐1,2*, FUM* and PGI‐2* loci exhibited different alleles which were fixed for the two species being analysed. Genetic distance, as calculated by Nei's index, showed a value of 0·413. Environmental hypersalinity, could have influenced the geographical distribution of P. tortonesei.
Oogenesis and the spawning pattern in Greenland halibut from the North‐west Atlantic
Authors: Rideout R. M. , Maddock D. M. , Burton M. P. M.
Published: April 2005

Gametogenesis in Greenland halibut Reinhardtius hippoglossoides from the North‐west Atlantic is not synchronous between individuals of the same population suggesting that the spawning season is not well defined. Differences in oocyte size–frequency distributions in prespawning, spawning and spent conditions suggest that Greenland halibut are capable of de novo vitellogenesis prior to and during spawning, indicating that the spawning pattern is not determinate. Greenland halibut may be capable of fast‐tracking oocytes to maturity, whereby during the spawning season oocyte batches may be brought quickly through vitellogenesis so as to increase the fish's yearly reproductive output. 1999 The Fisheries Society of the British Isles
A long‐finned specimen of Beryx decadactylus caught in the North‐eastern Atlantic of Rockall
Authors: Swinney G. N. , Holmes M. , Blackadder J. S. , Pye S. E.
Published: April 2005

A long‐finned specimen of Beryx decadactylus from of Rockall is reported and the Northeastern Atlantic persistence of juvenile characters in subadult and adult fish is discussed.
Migration patterns and recapture rates of North‐east Arctic and Norwegian coastal cod reared and released under similar conditions
Authors: Otterå H. , Jørstad K. E. , Svåsand T. , Kristiansen T. S.
Published: April 2005

A total of 5000 1‐group cod of Northeast Arctic and Norwegian coastal origin were reared under similar conditions, anchor tagged and released at two sites in western Norway. There were significantly more recaptures from the coastal cod. No differences in migration patterns were detected, suggesting that mortality rates were higher in North‐east Arctic cod.
The validity of different methods in the backcalculation of the lengths of roach—a comparison between scales and cleithra
Authors: Horppila J. , Nyberg K.
Published: April 2005

The backcalculated lengths of roach Rutilus rutilus obtained with three different proportional methods [body proportional (BPH) and scale proportional hypotheses (SPH), Fraser—Lee] were compared. In the BPH and SPH methods both scales and cleithra were used, while the Fraser—Lee method was used with scales only. The validity of the results was evaluated by comparing the results with observed lengths within one cohort. Both body—scale and body‐cleithrum relationships were best described by a power function (r2= 0·83). The backcalculated lengths of roach at age 1 varied from 51 mm (SPH, scales and cleithra) to 72 mm (Fraser—Lee), a 30% difference. In within‐cohort comparisons, the difference compared with observed lengths was smallest in BPH (<4% with few exceptions). The linear Fraser—Lee method overestimated (up to 5%) the lengths at young ages and underestimated the lengths at older ages (3–5%). In SPH the difference with observed length was 12% at highest. The length estimates by SPH were more affected by the age—structure of the sample than the estimates by BPH, which suggested that Lee's phenomenon was present. This was tested by backcalculating the lengths at the age of 2 years for roach, separately from different age‐groups. The backcalculated lengths declined with the increasing age of fish used in the calculations. The phenomenon was strongest in SPH and weakest in Fraser—Lee. The results suggested that in the backcalculation of the lengths of roach, BPH method gives the most reliable results. Considering the other methods, Fraser—Lee should be used rather than SPH.
Active biomonitoring with brown trout and rainbow trout in diluted sewage plant effluents
Authors: Schmidt H. , Bernet D. , Wahli T. , Meier W. , Burkhardt‐Holm P.
Published: April 2005

Brown trout Salmo trutta populations of numerous Swiss rivers are declining. Sewage plant effluents are discussed as a possible cause. To investigate the influence of sewage plant effluents, brown trout as well as rainbow trout Oncorhynchus mykiss were exposed to 10% diluted waste water over a period of 12 months. The effects were compared to those on trout kept in commercial tap water. The mortality rate was low and no pathogenic bacteria or viruses were recorded in exposed and tap‐water animals. Parasitological examination revealed a mild infestation with Gryodactylus sp. in all groups. Macroscopically and histologically, only minor changes in gills, skin, and kidney of exposed animals were found when compared to fish kept in tap water. Degenerative and inflammatory reactions in the liver of exposed animals were the most prominent findings. Several brown trout caught in the River Langete showed marked proliferative, degenerative and inflammatory lesions of gills, liver, and kidney. The results do not suggest that waste‐water effects would explain the decrease of fish populations. However, it is conceivable that the effluents in combination with other factors in the river enhance the development of changes.
Inter‐ and intrapopulation variation in temperature sum requirements at hatching in Norwegian Atlantic salmon
Authors: Berg O. K. , Moen V.
Published: April 2005

The duration of the ontogenetic development of the eggs up to hatching time was studied under stable water temperatures for a total of 47 families (the offspring of a single pair of spawners) from eight wild populations and one domesticated stock of Norwegian Atlantic salmon. Eggs from each family were incubated at stable water temperatures of 7·3 and 9·4° C. The number of days required to 50% hatching differed significantly between populations for both experimental temperatures together and for each temperature separately. The interpopulation and intrapopulation variation each accounted for about 50% of the overall variation. Significant differences were found for the days required to 50% hatching between eggs of the domestic stock from The Norwegian Salmon Breeding Company and two natural populations and between some of the wild populations. It is concluded that the time required from fertilisation to hatching in Atlantic salmon is a population‐specific adaptive trait.
Mitochondrion‐rich cells in the embryonic yolk sac of Oreochromis mossambicus
Authors: Lin H. C. , Hwang P. P. , Lee T. H.
Published: April 2005

By removing a small amount of yolk, tilapia embryos were dechorionated successfully as early as 30 h after fertilization. Using DASPEI, a mitochondrion‐specific fluorescent stain, we were able to determine the first appearance of the mitochondrion rich cells on the surface of the yolk sac 26 h after fertilization (c. 2 h after the beginning of gastrula stage). However, with scanning electron microscopy examination, no apical crypt could be found until 48 h after fertilization.
Recent visitations by eels to Sable Island, Canada, confirmed by parasites
Authors: Marcogliese D. J. , Scholz T.
Published: April 2005

The presence of immature stages of Proteocephalus macrocephalus in nine‐spined stickleback Pungitius pungitius, four‐spined stickleback Apeltes quadracus, three‐spined stickleback Gasterosteus aculeatus, and mummichog Fundulus heteroclitus from Sable Island ponds was confirmed using scolex morphology. The occurrence of this eel‐specific parasite in these accidental hosts provides evidence for recent visits by eels Anguilla rostrata to the isolated island in the North‐west Atlantic Ocean off the east coast of Canada.
Plasma concentrations of sex steroids and fighting in male Tilapia zillii
Authors: Neat F. C. , Mayer† I.
Published: April 2005

In laboratory‐held Tilapia zillii the gonadosomatic index (IG) is an accurate predictor of dominance in pairwise fights between males. Immediately after fighting no differences were detected between winners, losers or controls, in plasma concentrations of testosterone (T) or 11‐ketotestosterone (11KT). 11KT was correlated negatively with IG and positively with T. 11KT appeared to be the major androgen in this species, but there was no evidence that simple differences in levels of these sex steroids mediated aggressive behaviour.
Skin‐penetrating parasites and the release of alarm substances in juvenile rainbow trout
Authors: Poulin R. , Marcogliese D. J. , McLaughlin J. D.
Published: April 2005

Juvenile trout Oncorhynchus mykiss did not react to the odours of Diplostomum sp. Cercariae alone, indicating that they were incapable of detecting the parasites directly. However, they increased the number of random darts as well as the amount of time spent motionless when exposed to the odours of a conspecific that was being infected by Diplostomum cercariae. These results suggest that even the minor damage inflicted by the cercariae to the fish's skin was enough to cause the release of alarm substances. The effectiveness of the fish's response with respect to the avoidance of parasites remains to be demonstrated.
Metazoan parasite community structure of sea trout on the west coast of Ireland
Authors: Byrne C. J. , Holland C. , Tully O.
Published: April 2005

A total of 129 sea trout smolts from 10 locations on the west coast of Ireland were examined for metazoan parasites. Of 11 species identified only four had a prevalence >20%. Two species Hysterothylacium aduncum and Hemiuris communis have a confirmed marine origin; Eubothrium crassum has been shown to exist in both the sea and fresh water. The remaining species were fresh water. Overall the parasite community was dominated by autogenic species with only Diphyllobothrium dendriticum having allogenic transmission. Infracommunity values for mean species richness, and Brillouins index of diversity were low, indicating the presence of an impoverished helminth community with little potential for interspecific interaction. The relationship between marine helminths and sea lice was also examined.
Early larval development and metamorphosis in the summer flounder: changes in per cent whole‐body water content and effects of altered thyroid status
Authors: Schreiber A. M. , Specker J. L.
Published: April 2005

At the end of premetamorphosis, summer flounder Paralichthys dentatus larvae had 84·1% whole‐body water content (WBW), which decreased to the lowest levels (8·5%) at the start of metamorphic climax (MC). During mid‐ and late MC, %WBW was slightly higher (82·1%) then returned to the lowest levels at the juvenile stage. In fish treated with thyroxine (T4‐Na salt, 100 ng ml−1) beginning at premetamophosis, %WBW never differed from controls of the same age throughout metamorphosis, despite an earlier start of metamorphic climax and transitional settling behaviour. This suggests that thyroid hormones do not mediate the drop in %WBW which accompanies natural metamorphosis. Thiourea (TU, 30 μg ml−1) treatment of fish over the same period induced a developmental stasis in early MC which was accompanied by initially higher %WBW than controls at 33 days post‐hatch, followed by a progressive decrease to abnormally low %WBW by 42 and 45 days post‐hatch. Since concurrent treatment with TU+T4 rescued the fish from both the TU‐induced developmental stasis and abnormally low %WBW, these findings suggest that thyroid hormones, or thyroid hormone‐mediated developmental progression, are necessary for regulating %WBW.
Influence of salinity on early development in the spined loach
Authors: Bohlen J.
Published: April 2005

Spined loach Cobitis taenia developed successfully between 0·12 and 4·80‰ salinity. At 6·00‰, net production was strongly reduced, and development failed at or above 7·20‰. Below 0·12‰ S, net production became variable, indicating restrictive effects. In comparison with other primary freshwater fish species C. taenia has a low sensitivity to salinity. The upper limit for early development was equal to the highest salinity under which C. taenia adults are found along the Baltic coast. Therefore, salinity should not limit early development within the brackish habitats of spined loach.
Coping with resource variation: Effect of constant and variable intervals between feeding on reproductive performance at first spawning of female three‐spined sticklebacks
Authors: Ali M. , Wootton R. J.
Published: April 2005

Female three‐spined sticklebacksGasterosteus aculeatusexposed to spring conditions (14) C and a photoperiod of 16L: 8D), and fed 6% of initial body weight per day of enchytraeid worms (controls) over 56 days, or either at regular 3‐day or variable 1–5‐day intervals between feeds, did not differ significantly in the proportion spawning (72%), in time to first spawning (24·5 days), in fecundity at first spawning (34) or in egg diameter (1·4 mm) at first spawning. There was no significant effect of feeding regime on lipid concentration of females immediately after first spawning (18·8% dry weight), but the experimental females had a slightly lower dry matter content and lower fresh and dry liver weight than controls. Eggs of females on the variable‐interval regime had a higher lipid content than eggs from other groups. Days to spawning was correlated inversely and fecundity positively with initial length. Females adjusted their food intake to compensate for short periods of food deprivation, allowing them to maintain their reproductive performance at first spawning.
rDNA RFLPs as genetic markers for resource management in brown trout
Authors: Castro J. , Pardo B. G. , Sánchez L. , Martínez P.
Published: April 2005

Interesting population‐specific rDNA markers were detected for microgeographical analysis of brown trout Salmo trutta as well as for monitoring stocking practices.
The toxicity of iron to brown trout and effects on the gills: a comparison of two grades of iron sulphate
Authors: Dalzell D. J. B. , Macfarlane N. A. A.
Published: April 2005

The 96‐h LC50 on brown trout Salmo trutta of a commercial iron (III) sulphate liquor, used for treating reservoirs to reduce algal growth, was 28 mg total Fe l−1 (0·05 mg soluble Fe l−1). The 96‐h LC50 for analar grade iron (III) sulphate was 47 mg total Fe l−1 (0·24 mg soluble Fe l−1). Lethal and sublethal exposure to both grades of iron resulted in accumulation on the gill, which appears to be the main target for iron toxicity. Greater iron accumulation occurred during exposure to commercial iron sulphate liquor. Physical clogging of gills and gill damage was seen during lethal and sublethal exposure to iron. Gill tissue analysis showed no evidence of iron uptake into gill tissues during lethal or sublethal exposure to iron. Iron did not accumulate in plasma of fish exposed to iron compared to controls. Respiratory disruption due to physical clogging of the gills is suggested as a possible mechanism for iron toxicity.