bluuebunny/crossref_metadata_2025 huggingface dataset:
Lake enrichment and the status of Windermere charr, Salvelinus alpinus (L.)
Authors: Mills C. A. , Heaney S. I. , Butterwick C. , Corry J. E. , Elliott J.M.
Published: January 2006

All English populations of Arctic charr, Salvelinus alpinus (L.), are found in the Lake District (northwest England). There are at least four races of charr in Windermere, the largest lake in England; the North and South basins of the lake each contain two distinct races that spawn in autumn and spring respectively. The spring spawners in both basins probably represent less than 15% of the total population in the lake.

Changes in the population density of charr in the lake are described briefly and examined in relation to the trophic status of the lake. Other factors that could possibly affect the charr population are reviewed, especially the influence of climate change.
Threatened native freshwater fishes in Australia–some case histories
Authors: Ingram B. A. , Barlow C. G. , Burchmore J. J. , Gooley G. J. , Rowland S. J. , Sanger A. C.
Published: January 2006

Case histories of some of Australia's most threatened native freshwater fishes are presented. These include: six endangered species, Galaxias fontanus, G. johnsroni, G. pedderensis (Galaxiidae), Melanataenia euchamensis (Melanotaeniidae), Maccullochella sp. nov. and M. macquariensis (Percichthyidae): one vulnerable species, Galaxias tanycephalus: two potentially threatened species. Galaxias parvus and Prototroctes maraena (Prototroctidae); one indeterminate species. Maccllochella sp.; one restricted species, Macquaria australasica (Percichthyidae). Aspects of their taxonomy, distribution and reasons for their decline are discussed. Conservation management strategies that have been or are being applied to most of these species include protection of the fish and their habitats, establishment of refuge populations, and artificial propagation and re‐establishment programmes.
Time course of extracellular acid‐base adjustments under hypo‐ or hyperosmotic conditions in the euryhaline fish Platichthys flesus
Authors: Nonnotte G. , Truchot J.‐P.
Published: January 2006

In order to better understand the basis for the euryhalinity of the flounder, Platichthys flesus, which tolerates large variations in water salinity, experiments have been designed to characterize the time course of extracellular ionic and acid‐base adjustments under hypo‐ or hyperosmotic conditions. Abrupt transfer from sea water (SW) to fresh water (FW) provokes a transient decrease in the plasma osmolality (Posm) and a concomitant transient metabolic alkalosis (whole blood pH 7.78 in SW and 8.04 five days after FW transfer) associated with a marked, persistent hypercapnia. After 33 days in FW, Posm and whole blood pH are not significantly different from those in SW, but whole blood Pco2 and plasma bicarbonate concentration are always higher than SW values. Opposite transitory fluctuations, i.e. a metabolic acidosis associated with a respiratory alkalosis, occur when flounder long‐acclimated to FW are again exposed to SW. The mechanisms involved in these salinity‐dependent acid‐base disturbances are rather complex and remain to be elucidated. These observations attest to the importance of the extracellular acid‐base changes that may be (i) linked to extracellular anisosmotic regulation and/or to cellular metabolic adjustments, and (ii) compensated partially by ventilatory adjustments.
Age and growth of Lutjanus kasmira (Forskål) in Hawaiian waters
Authors: Morales‐Nin B. , Ralston S.
Published: January 2006

The growth of Hawaiian taape, Lutjanus kasmira, was studied by examining otoliths and by analysing length‐frequency distribution. Annual hyaline and opaque markings were visible in whole mounts of sagittae, which were verified by enumeration of daily increments with a scanning electron microscope (SEM) and through marginal increment analysis. The von Bertalanffy growth curve was fitted to the data, resulting in:

image

where t.l. is total length (cm) and t is age (years). SEM observations revealed that the slowgrowth hyaline zones were composed of daily increments too small (0.4–0.8 μm) to be resolved optically. Thus, age estimates derived by numerically integrating otolith growth rate data obtained with a light microscope showed a negative bias, resulting in overestimation of growth rates. Parameter estimates obtained from three different types of length‐frequency analysis were also unstable. This was due, at least in part, to differences in the size composition of fish sampled with different fishing gears and from different depths.

The growth rate registered in Hawaii falls within the reported growth coefficients of lutjanids, whereas it is one of the highest in the Pacific and clearly higher than a deep‐water lutjanid species growth in Hawaii. Probably, this high growth rate may have been enhanced by the relative lack of competitors in the depauperate Hawaiian marine fish community.
Seasonal changes in condition indices in adult mature and non‐maturing burbot, Lota lota (L.), in the north‐eastern Bothnian Bay, northern Finland
Authors: Pulliainen E. , Korhonen K.
Published: January 2006

The population structure and seasonal changes in condition factors of the burbot in a shallow coastal region of the north‐eastern Bothnian Bay are described. The significance of the so‐called rest years is examined by comparing condition indices in immature or sterile and mature burbot. The somatic condition index (K2), liver index (K1), intestine index (K1) and gonad index (Kg) are determined monthly in terms of organ weight in relation to body length. Approximately 30% of the whole catch of 1052 burbot were non‐maturing but were 40 cm or more in length. K2, K1 and K1 were lowest in the autumn, when the first sign of gonad recrudescence was observed in mature burbot. The non‐maturing burbot were never in poorer condition than mature ones. As mature and non‐maturing burbot dissipated their energy stores during the warmest period of the summer, it is concluded that burbot spending a rest year do not accumulate and store energy reserves over the summer for the next year, and that such rest years, if they exist, do not occur for nutritional reasons.
Surf zone fish community and species response to a wave energy gradient
Authors: Romer G. S.
Published: January 2006

Analysis of seine netting data for Algoa Bay, South Africa reveals that species richness and relative abundances of surf zone fishes differ at three beach sites, despite their close proximity. A gradient in species compositional and abundance response to spatially varying wave exposure is proposed as the principle cause. Implications are considered in the context of trophic interaction and impact of individuals and species assemblages upon energy and other resources of the habitat.
Haematological response to reduced oxygen‐carrying capacity, increased temperature and hypoxia in goldfish, Carassius auratus L.
Authors: Murad A. , Houston A. H. , Samson L.
Published: January 2006

Goldfish were exposed to three qualitatively distinct forms of respiratory stress: phenylhydrazine HCl‐induced reduction in blood oxygen‐carrying capacity; transient (3 h) hypoxia; and transient (1 or 2 h) temperature‐forced increases in oxygen demand. Response embodied three common features: (1) the relative number of immature red cells increased, and these were 3H‐thymidine positive; (2) the abundance of apparently karyorrhectic or degenerating cells rose; (3) cells undergoing a form of division became prevalent. Neither of the latter two cell types evidenced thymidine uptake. These observations suggest that respiratory distress triggers the proliferation of new erythrocytes, and that this is accompanied by elimination of some portion of the preexisting red cell population. It is hypothesized that the latter process limits viscosity‐related elevation of cardiac work costs. The significance of division by circulating erythrocytes is not clear.
The ploidy and reproductive mechanism of crucian carp, Carassius auratus gibelio
Authors: Fan Z. , Liu G.
Published: January 2006

With the method of Feulgen staining, through cytophotometric measurements, the DNA contents of sex‐reversed male (genotypic female) crucian carp (2n = 150 ±) had average values of 2.75 and 1.36 A.U., respectively, in erythrocytes and spermatozoa. The ratio of the erythrocyte and spermatozoon DNA contents of the ‘male’ crucian carp is 2.01:1 (2C: 1C) and is the same as in the normal male, 2.02:1. The crucian carp has a DNA value of 4.1 pg, which is 68% of that in humans. The results of the study suggest that both sex‐reversal males and normal males have the ability to complete the meiotic division during their gametogenesis, and that the population has diploidized over a long term of evolution.
The process of skin healing in experimentally wounded carp
Authors: Iger Y. , Abraham M.
Published: January 2006

The process of skin healing was studied in thin sections of adult mirror‐carp, superficially wounded with a razor blade in a scaleless region. Shortly after wounding, epidermal cells from both sides of the wound moved towards the wound cavity. The cells moved as compact groups, without severing the normal intercellular desmosomes. The moving cells displayed phagocytotic activity of cellular debris during the migration. The phagosomes reacted with diaminobenzidine, revealing strong peroxidase content. The normally abundant pinocytotic vesicles from the basal layer of filament cells vanished during the first hour after wounding, and reappeared after 2 days; 24 h after wounding, desmosomes interconnected the filament cells from both sides of the wound. Due to profuse mucus secretion, the number of mucous cells from the epidermal stratum was markedly reduced. Rodlet cells appeared 1 h after wounding in the external region of the epidermis. There was pronounced increase in alkaline phosphatase content of the pavement cells 10 min after wounding; this enzyme appeared around the ridges of the pavement cells and inside the mucous cells 20 min later.

In the dermis, the region surrounding the wound was darkened, blood cells extravasated, and penetrated partially into the epidermis. After 2 days, dermal fibroblasts displayed intense phagocytosis; after 8 days they were particularly abundant in the region of regenerating tissue and were secreting large quantities of collagen. Marked changes in the relative frequency of the different types of leucocyte occurred during the post‐wounding days.
The distribution and abundance of young (I +–II +) perch, Perca fluviatilis L., in a deep eutrophic lake, England
Authors: Goldspink C. R.
Published: January 2006

Seasonal changes in the vertical and horizontal distribution of young (I +–II +) perch in Rostherne Mere, a deep (max. depth 31.0 m) eutrophic lake are described using sonar. During the summer (June–August), perch were present within the thermocline (9–14° C) between 7 and 10 m. There was no significant difference between samples during this period, nor was there any evidence of shoaling. From September onwards perch moved into deeper waters. By late winter fish had become patchy in their distribution. Total numbers, during the summer, were estimated to be 988 ha 1 with 95% confidence limits of ±115 (biomass 98.8 kg ha −1). Densities (no. m−3) fell by over 90% after the autumn overturn. The implications for predators are discussed. Acoustic sampling provides a useful, non‐destructive method of sampling eutrophic lakes on a routine basis. Information obtained is of ecological, behavioural and physiological interest.
Consumption, growth and respiration of bleak, Alburnus alburnus (L.), and roach, Rutilus rutilus (L.), during early ontogeny
Authors: Keckeis H. , Schiemer F.
Published: January 2006

Three components of the energy budget, consumption (C), production (P) and respiration (R) in juvenile roach and bleak kept under controlled food (Anemia salina, 2400 ind. l−1) and temperature (20° C) conditions were measured in a study aimed at defining differences between the two species and elucidating the patterns of energy partitioning during ontogeny.

Daily food consumption rates (J day−1 fish−1) increased allometrically (C=a Wb) with body size (W, mg dry weight) in both species. Covariance analysis indicated no differences in slope or intercept for the two regression lines (P≤ 0.05, n= 82). However, the two species grew at significantly different rates, roach faster than bleak.

The dependence of the respiration rate (μmol h−1 fish −1) on body weight (W) can be described by an allometric function: R= aWb, where a ± 95% C.L. = 0.17 ± 0.15 for roach and 0.18 ± 0.20 for bleak. The slope for roach (b ± 95% C.L. = 0.78 ± 0.01) is slightly higher than that for bleak (0.69 ± 0.03).

Assimilation efficiency [AE = (P+R) C−1] was significantly higher in roach than in bleak. Different levels of AE correlated with differences in relative gut length (gut length as percentage of body length). Due to the shorter relative gut length above a weight of 5 mg, bleak has lower powers of digestion, which may explain lower production rates. These differences in energetic performance between the two species indicate mechanisms leading to niche differentiation in the early life history of the fishes.
Gross structure of the respiratory organs and dimensions of the gill in the mud–skipper, Periophthalmodon schlosseri (Bleeker)
Authors: Yadav A. N. , Prasad M. S. , Singh B. R.
Published: January 2006

In Periopkrlialnwdon scldosseri the respiratory organs consist of the gills, the suprabranchial and opercular chambers. The gills are more suited for aerial than aquatic respiration as is shown by the presence of the vascular papillae, blood sinusesand dilated blood vessels in their lamellae. The gill lamellae possess a surface coat of sulphated mucopolysaccharides that prevents water loss during exposure to the air. The filaments of the outer hemibranchs in the first gill arch are reduced to nearly one quarter of those of its posterior hemibranch. The gill area in relation to body weight shows a high slope value (b=0·93).
Chemical requirements of feeding in rainbow trout, Oncorhynchus mykiss (Walbaum); palatability studies on amino acids, amides, amines, alcohols, aldehydes, saccharides, and other compounds
Authors: Jones K. A.
Published: January 2006

Past studies on palatability perception and the chemical requirements of feeding in rainbow trout have focused on the amino acids. The stimulatory effectiveness of other classes of compounds remains largely unknown. In the present study representative members from several chemical classes were tested for their palatability to rainbow trout. Three heretofore untested amino acids (L‐norvaline, L‐norleucine and c‐aminocaproic acid), three amides (acetamide, valeramide and caproic amide), two alcohols (hexanol and octanol) and four sugars (o‐ribose, o‐glucose, D‐fructose and sucrose) were all mildly to highly palatable substances at their highest concentration tested. All other compounds tested within these classes did not evoke a positive behavioural response, demonstrating that rainbow trout are selective in thosecompounds deemed as palatable. Moreover, all of the aldehydes, trimethylamine, pyrrolidine and all of the amines except the alcoholic derivative, ethanolamine, were without effect. A provisional scheme for relating chemical structure versus the perception of palatability in rainbow trout is presented.
Morphological and behavioural development of halibut, Hippoglossus hippoglossus (L.) larvae
Authors: Pittman K. , Skiftesvik A. B. , Berg L.
Published: January 2006

Live yolk‐sac halibut, Hippoglossus hippoglossus (L.) larvae from rearing experiments at Austevoll Aquaculture Station, Norway, were examined from hatching to past first feeding for developmental morphology and behaviour. The findings include development of the respiratory and circulatory organs, eye pigmentation, mouth formation, organs of the digestive system and the process of yolk absorption, as well as swimming speed and activity levels.

A stomodeum is not present at hatching although drinking is possible through a pair of branchial pits which gradually develop into the operculum and gill basket. The mouth normally opens slowly, the gape being restricted by a transverse septum until bones are formed. The amount of time spent swimming varies from less than 15% of the observation period during the first 2 weeks after hatching to between 70 and 100% around the seventh week after hatching, when individual differences become more apparent. Larvae generally react with a burst of swimming when two come into contact. Speed and duration of swimming seems to be correlated with development of eye pigment, heart size and fin formation. The yolk‐sac period is divided into four stages.
Environmental correlates of life‐history variation in juvenile chinook salmon,Oncorhynchus tshawytscha(Walbaum)
Authors: Taylor E. B.
Published: January 2006

Throughout its native North Pacific, the chinook salmon, Oncorhynchus tshawytscha (Walbaum), exists as twolife‐history types that aredistinguished by the age at which juvenile salmon migrate to sea as smolts. ‘Stream‐type’ chinook migrate seaward after I or more years of feeding in fresh water, whereas ‘ocean‐type’ fish migrate to sea as newly emerged fry or after 2–3 months in fresh water. Stream‐type chinook predominate in populations distant from the sea south of 56° N, and in both inland and coastal populations north of this point. By contrast, ocean‐type chinook predominate in coastal populations south of 56° N, but are rare in populations in more northerly latitudes. Stream‐type populations are associated with areas of low ‘growth opportunity’ (as measured by temperature and photoperiod regimes) and/or areas distant from the sea compared to ocean‐type. Geographic variability in juvenile life history is suggested to result, in part, from environmental modulation of smolting timing via differences in growth opportunity among geo‐graphic areas. In addition, differences in migration distance and temperature regime may result in selection for different sizes at migration among populations which, through differences in growth opportunity, might promote geographic variability in age at seaward migration.
Foraging and dietary strategies of two sublittoral cottids, Jordania zonope and Artedius harringtoni
Authors: Demetropoulos C. L. , Braithwaite L. F. , Maurer B. A. , Whiting D.
Published: January 2006

The longfin sculpin, Jordania zonope Starks, 1895, and the scalyhead sculpin, Artedius harringtoni (Starks, 1896), arecommon subtidal cottids in the San Juan Archipelago, Washington, but little of their autecology has been investigated. Comparisons of distribution, microhabitat density, foraging behaviour and diet were conducted for the two species. Even though the two species occurred close together, microhabitat use differed between them, as did foraging strategies. Jordania zonope had a broader foraging range and tended to take bites out of prey items, whereas A. harringtoni had a more limited foraging range and tended to swallow prey whole. Partitioning of spatial and nutritional resources as well as morphological differences supported the hypothesis that J. zonope and A. harringtoni minimize interspecific competition in spite of microhabitat overlap and often side‐by‐side feeding.
The effect of feed cycling and ration level on the compensatory growth response in rainbow trout, Oncorhynchus my kiss
Authors: Quinton J. C. , Blake R. W.
Published: January 2006

Compensatory growth is the phase of rapid growth, greater than normal or control growth, which occurs upon adequate refeeding following a period of undernutrition. The effect of feed cycling periods (periods of starvation followed by periods of refeeding), ration level and repetitive feed cycles on the compensatory growth response in rainbow trout were evaluated in two experiments. A feeding cycle of 3 weeks starvation and 3 weeks feeding produced better results in terms of average percentage changes in weight and length, and in specific growth rate, than either 1 week and 1 week or 2 weeks and 2 weeks feed cycles. The fish on the 3 weeks starvation and 3 weeks feeding cycle did as well as, if not better than, the constantly fed controls over one or two complete cycles, though the controls were fed more than twice the amount of feed. Three ration levels were compared using a 3‐week starvation and 3‐week feeding period. The only effect of increasing ration level was to decrease conversion efficiency, indicating overfeeding. Carcass analysis of moisture, fat, protein and ash showed no significant differences between the controls and an experimental group on a 3 weeks starvation, 3 weeks feeding cycle after one complete cycle. Possible mechanisms underlying the compensatory growth response are discussed.
Larval growth and drift pattern and the separation of herring spawning groups in the North Sea*
Authors: Munk P. , Christensen V.
Published: January 2006

Data from two internationally co‐ordinated survey programmes are used in an attempt to display the events in the early life that took place during the ‘recovery period’ of the North Sea herring Stock, 1979–1986.

During the period, an increasing importance of the spawning grounds off Buchan and off Yorkshire is evident from distributions of newly hatched herring larvae. The dramatic changes in relative importance of spawning grounds are traced in the data on both late larvae (6 months old) and juveniles (18 months old). The onset of extended spawning off Buchan and off Yorkshire was followed by increase in distinct groups of late larvae of large mean length, and by enlargement of a group of medium‐sized juveniles. It is hypothesized that the identified groups are interconnected. Thus, larvae spawned off Buchan and off Yorkshire are found to have growth rates superior to those attained by larvae from west of Scotland and around the Orkney/Shetland Isles, whereas the relationship is reversed in the juveniles. In the investigated period, larval drift routes exhibited the same trends from year to year, the drift of the northerly spawned larvae being the most variable.

Thus, changes in the relative contributions from spawning grounds apparently influence the overall spatial distribution as well as size composition of larval and juvenile North Sea herring. The findings indicate that groups of larvae retain, to a large extent, separate distributions until metamorphosis, and point to larval drift pattern as a determinant of spawning group distinctness.
Sex‐determining genes in tilapia: a model of genetic recombination emerging from sex ratio results of three generations of diploid gynogenetic Oreochromis aureus
Authors: Avtalion R. R. , Don J.
Published: January 2006

Three major findings emerged from this study: (1) the existence of gynogenetic males among first, second and third generations of gynogenetic tilapias; (2) the sex ratios amongst gynogenetic offspring reflect two genetically different maternal types, the first type giving rise to both gynogenetic males and females, and the second type only to females; (3) females of the first maternal type produce more gynogenetic female than male offspring. On the basis of a genetic recombination model between sex‐determining genes and the centromere, the first maternal type was defined as heterogametic (WY) and the second as homogametic (WW). This model suggests that females with the WY combination can produce in all descending gynogenetic generations offspring expressing the three above gynotypes, and this suggestion is consistent with our FI–F3 sex ratio results.
Is there an optimal haematocrit for rainbow trout, Oncorhynchm mykiss (Walbaum)? An interpretation of recent data based on blood viscosity measurements
Authors: Wells R. M. G. , Weber R. E.
Published: January 2006

The viscosity of blood from rainbow trout was measured following manipulation of haematocrit by bleeding, hypoxia. exercise, and anaesthesia. Blood viscosity when measured at high shear rate (225 s 1) was proportional to haematocrit, but the dependence of viscosity on shear rate was far less for swollen erythrocytes from exercised and anaesthetized trout. Erythrocyte swelling was most marked in exercised and anaesthetized trout, and is a confounding factor when considering the effect of haematocrit on viscosity.

The viscosity of blood with variable haematocrit, but constant mean cell Hb concentration, indicated that the relative oxygen transport capacity in trout was optimal at a haematocrit of 30%. Data from this, and earlier studies show that haematocrit in trout is variable and labile, yet none of the haematocrit values following manipulations are less than 85% of optimal. Optimal haematocrit is however, significantly higher than measured values from either cannulated or acutely venesected resting trout.
The effectiveness of sodium lauryl sulphate as a shark repellent in a laboratory test situation
Authors: Smith Larry J.
Published: January 2006

Swim‐through chemical repellency tests, using sodium lauryl sulphate (SLS), cupric acetate, and rotenone, were conducted in a specially‐designed roundabout tank on horn sharks, Heterodontus francisci, swell sharks, Cephaloscylliun ventriosum, and leopard sharks, Triakis semifasciata. Effective concentration thresholds (EC50s) were calculated for two levels of response: (1) minimum noticeable and (2) strong. The SLS EC50s were: horn shark 43.6 and 174.5 ppm; swell shark 95.1 and 160.0 ppm; and leopard shark inconclusive and 113.1 ppm. No response was discernible from cupric acetate. Rotenone evoked a weak response with an EC50 of 5.7 ppm, but no strong response.

The ratio of the minimum noticeable EC50: 24‐hour lethal concentration (LC50) indicated the relative repellency (compared to toxicity) of the chemicals. The ratio for SLS was 19:1 and for rotenone 57:1. SLS did not provoke a repellency response at a low enough concentration to function effectively as a classical, surrounding‐cloud type, repellent. The range of potency of SLS, however, does allow it to be used as a directional repellent.
The influence of ambient salinity on routine metabolism in the teleost Cyprinodon variegatus Lacepède
Authors: Nordlie F. G. , Walsh S. J. , Haney D. C. , Nordlie T. F.
Published: January 2006

Routine metabolism of the euryhaline cyprinodontid Cyprinodon variegatus Lacepede was measured at a series of ambient salinities ranging from fresh water through 100‰. Fish used had been sequentially acclimated to the test salinities (ambient temperature of 20±1° C and a 12: 12 L: D schedule).

Routine metabolic rates were highest at ambient salinities from 15 to 50‰. Metabolism was somewhat lower at ambient salinities less than 15‰, and showed a sequential decline at ambient salinities greater than 50‰. It is suggested that routine metabolism is depressed at elevated salinities by reduced O, transfer, a consequence of maintenance of hydromineral balance in hypersaline waters.
Stress response in the Antarctic teleosts (Notothenia neglecta Nybelin and N. rossii Richardson)
Authors: Egginton S. , Taylor E. W. , Wilson R. W , Johnston I. A. , Moon T. W.
Published: January 2006

Blood chemistry and haematological parameters have been determined in the Antarctic teleosts, Notothenia neglecta Nybelin and Notothenia rossii Richardson at 2° C. Samples were taken using chronically implanted dorsal aortic cannulae following a minimum of 24–36 h recovery. Broadly similar results were obtained for the two species. In N. neglecta, routinely active specimens had high values of arterial pH (7.81) and PO2 (9.26 kPa), and modest haemoglobin levels (5.6 g dl−1) relative to temperate species. Following 3 min strenuous activity there was a decrease in arterial pH (7.63) and a small rise in lactate from 0.41 to 0.68 mm, but no significant change in the calculated net metabolic acid load (δHm+). PaO2 and PaCO2 varied inversely during exercise, and oxygen content declined by 22%. pHa and most other haematological parameters returned to routine values between 1–3 h post‐exercise. The results suggest that the major effect of strenuous activity in Notothenia spp. is a respiratory, rather than a metabolic acidosis.
Shifts in fish communities along the productivity gradient of temperate lakes—patterns and the importance of size‐structured interactions
Authors: Persson L. , Diehl S. , Johansson L. , Andersson G. , Hamrin S. F.
Published: January 2006

Species biomass and size composition of fish faunas along a productivity gradient were studied in south Swedish lakes. Generally, with increasing productivity (measured as chlorophyll content), Salmoniformes were replaced by percids, which in turn were replaced by cyprinids, as suggested in previous studies. However, percids showed two peaks in biomass, one in medium productive lakes due to perch and one in highly productive lakes due to zander. Benthic piscivores were present in all lakes, whereas pelagic piscivores were absent in the least productive lakes. The proportion of piscivores in the total fish biomass showed a peak in medium productive lakes, largely reflecting the importance of piscivorous perch. The median size of the dominant cyprinids (roach) in the systems studied increased as the importance of piscivores increased, which was interpreted as a size refuge response to increased predation pressure. The same pattern was present for the dominant planktivore, vendace, in low productive systems. Although a predictable pattern of change in the fish fauna was found along the productivity gradient, other environmental factors such as structural complexity may be the ultimate cause of the observed succession pattern.
Incorporation of 14C‐labelled polyunsaturated fatty acids by juvenile turbot, Scophthalmus maximus (L.) in vivo
Authors: Linares F. , Henderson R. J.
Published: January 2006

The ability of juvenile turbot, Scophthalmus maximus (L.), to elongate and desaturate various polyunsaturated fatty acids (PUFA) was examined in relation to their lipid composition. Triacylglycerols were the most abundant lipid class present in the fish and phosphatidylcholine was the predominant phospholipid. In all lipid classes examined the levels of (n‐3) PUFA exceeded that of (n‐6) PUFA. 18C PUFA were minor components in comparison with 20:5(n‐3) and 22:6(n‐3). 20:4(n‐6) was present in highest concentration in phosphatidylinositol in which it accounted for 16.9% of the fatty acids. When the fish were injected with either 14C‐labelled 18:2(n‐6), 18:3(n‐3), 20:4(n‐6), 20:5(n‐3) or 22:6(n‐3) the highest percentage recovery of radioactivity (69%) in body lipid was observed with 22:6(n‐3). With all labelled substrates free fatty acids contained only a small proportion of the total recovered radioactivity whereas triacylglycerols were highly labelled. Phosphatidylcholine/sphingomyelin was the most highly labelled polar lipid fraction. With 14C‐20:4(n‐6) as injected substrate, 23.2% of the radioactivity recovered in total lipid was present in phosphatidylinositol in comparison with less than 6% with the other substrates. Only small proportions of radioactivity from 14C‐18:2(n‐6) and 14C‐18:3(n‐3) were recovered in the 20 and 22C fatty acids of triacylglycerols and total polar lipid. With 14C‐20:5(n‐3) as substrate, 27 and 33% of the total radioactivity recovered in the fatty acids of triacylglycerols and polar lipids respectively was present in 22C fatty acids. The corresponding values for l4C‐20:4(n‐6) as substrate were 19 and 18%. The results confirm the limited capacity of turbot to convert 18C PUFA to longer chain PUFA but demonstrate their ability to synthesize 22C PUFA from 20C PUFA. They also suggest a small but specific requirement for 20:4(n‐6).
The effects of capture, net retention and preservation upon lengths of larval and juvenile bass, Dicentrarchus labrax (L.)
Authors: Jennings S.
Published: January 2006

Relationships between live and preserved lengths of larval and juvenile bass, Dicentrarchus labrax, subjected to simulated capture, net retention and preservation were investigated. Bass larvae and juveniles shrank during the period of net retention following death. Preserved lengths of larvae, but not of juveniles, decreased significantly when increased periods of net retention preceded preservation. The time which larvae or juveniles remained in 4% formaldehyde in distilled water buffered with 3gl−1 sodium acetate trihydrate or in 70% ethanol in distilled water neutralized with 1gl−1 calcium carbonate powder, had no significant effect upon preserved length. Appropriate data were pooled to calculate transformation factors for estimating live from preserved length. Shrinkage phenomena, and their effects, are discussed. It is suggested that larval bass captured and preserved during standard ichthyoplankton surveys are unsuitable for determination of live length.
A comparative assessment of temporal variation in diet of powan, Coregonus lavaretus (L.), from Loch Lomond and Loch Eck, Scotland, U.K.
Authors: Pomeroy P. P.
Published: January 2006

Stomach contents of powan caught throughout the year from Loch Lomond and Loch Eck were examined. Adult powan in Loch Lomond fed mainly on planktonic Cladocera, switching to benthic food during December‐April. Bosmina coregoni was the principal planktonic food with Daphnia hyalina an important late summer and autumn prey. Loch Eck powan fed throughout the year on chironomid larvae and Pisidium spp. from the benthos and ingested large amounts of non‐food material. Mean dry weights of food in stomachs were correlated with water temperature in Loch Lomond but not in Loch Eck and were higher in powan from Loch Eck over most of the year.
The population biology of Camallanus lacustris (Zoega) in eels, Anguilla anguilla (Linnaeus), and their status as its host
Authors: Nie P. , Kennedy C. R.
Published: January 2006

The population biology of Camallanus lacustris (Zoega) and the status of the eel, Anguilla anguilla (Linnaeus), as its definitive host have been studied in a small Devon lake. No clear seasonal pattern in prevalence and abundance was observed, and recruitment of the new generation may occur in all seasons. However, reproduction exhibits some seasonality as adult nematodes were the commonest stage in the parasite population from early summer onwards and production of first‐stage larvae appeared to occur primarily during this period. These larvae were viable, and shown experimentally to be infective to copepods. The occurrence of the nematode and its development to full maturity in eels, the absence of its typical definitive host (Perca fluviatilis Linnaeus) from the lake and the absence of the nematode from other species of fish in the lake indicate that eels serve as the only, true definitive host of the nematode in this locality. It is suggested that account must be taken of this alternative host when the population of C. lacustris is investigated in the future.
Larval fish production in the tidal River Elbe 1985–1986
Authors: Möller H. , Dieckwisch B.
Published: January 2006

In 1985 and 1986 ichthyoplankton composition was studied during seven sampling series at 37 stations along the tidal Elbe and its tributary rivers between Hamburg harbour and the North Sea. The highest larval density was observed in May and April. No, or very few, larvae occurred from late summer to early spring. Smelt (59% on average of all samples) and twaite shad (20%) dominate in the freshwater region. Herring/sprat (17%) dominate in the estuary. All major spawning grounds are located along the southern shore. Smelt spawn further upstream 1 month earlier than twaite shad. Three percent of all larvae found were flounder. Most of them occurred upstream from the estuary in the R. Este and in other tributary rivers. It is not clear whether flounders are able to spawn in freshwater. Attention is drawn to the fact that an unknown but probably very high percentage of the ichthyoplankton is entrained by local power plants.
Investigations into the biology of the garfish, Belone belone (L.), in Swedish waters
Authors: Dorman J. A.
Published: January 2006

Garfish, Belone belone (L.), were collected from commercial fishermen between May and September of 1987 from around the Swedish coast. Fish belonging to the year classes of 1983, 1984 and 1985 dominated the catch, with very few fish from the year classes of 1980, 1981 and 1982. Maturity stages and condition were investigated, and estimates of fecundity calculated; these ranged from 2193 to 10804 eggs per ripe female. Examination of gut contents showed fish, especially juvenile clupeids and gasterosteids, as well as isopods and amphipods, to be the most important components of their diet. Garfish populations from both the Baltic and the west coasts were parasitized by copepods of the genus Caligus. A study of meristic characteristics showed a significant difference between the number of vertebrae in fish from the Baltic and those captured on the west coast of Sweden.
Episodic exposure to acid and aluminium in soft water: survival and recovery of brown trout,Salmo trutta L.
Authors: Reader J. P. , Dalziel T. R. K. , Morris R. , Sayer M. D. J. , Dempsey C. H.
Published: January 2006

Yolk‐sac fry, swim‐up fry and 1–2 yr juveniles of brown trout, Sulmo trutta L., were exposed to episodes of aluminium and low pH, maximum aluminium concentration 12 μmol l−1 (323 μg l−1), minimum pH 4.5, total duration up to 54 h (yolk‐sac fry) or up to 78 h (swim‐up fry and juveniles), in an artificial soft water medium, [Ca] 20 μmol l−1 (0–8 mg l−1) (nominal baseline: pH 5.6, zero aluminium concentration). Yolk‐sac fry mortality was nil or very low. A marked increase in susceptibility, with high mortalities, occurred when the yolk was fully absorbed. Mortality of juveniles exposed to two successive episodes was lower than would have been expected on the basis of comparisons with mortalities in single episodes, and mortality declined as the interval between the two episodes was increased. Disturbance of sodium, potassium or calcium balance or gill damage in surviving yolk‐sac fry or juveniles was still evident 5 to 6 days after the end of a single episode.
Algae as first food for cod larvae, Gadus morhuaL.: filter feeding or ingestion by accident?
Authors: Van der Meeren T.
Published: January 2006

Cod larvae. Gadus morhua L., 24 days posthatch, were fed different species of algae in order to evaluate both rates and mechanisms of ingestion. The results were compared with cod larvae feeding on a natural assemblage of algae in a lagoon. Small algae (Nannochloris atomus Butcher, 14 pm) were found to enter the larval gut in accordance with drinking rate. In contrast, the cod larvae concentrated larger algae [Dunaliella salina(Dunal) Teodor. 6 10 pm] in the gut at rates from 492 to 7251 times the drinking rate. D. salina was captured in the slits between the visceral arches, and increased activity when the algae was added indicate that the cod larvae are active filter feeders during early larval stages. In the gut of cod larvae from the lagoon the fraction of algal material with diameter larger than 8 pm was 39.2% in 7‐day‐old larvae while, in 12‐day‐old larvae it had decreased to 12.6%. The most conspicuous characteristics of gut content in the youngest larvae were green spheres (10 μn) and a naked dinoflagellate (20 μn). Short chains of the diatom Skeletonemu cosrarum (Greville) Cleve were also frequently found.
Direct measurements of metabolism, activity and feeding behaviour of pike, Esox Zucius L., in the wild, by the use of heart rate telemetry
Authors: Lucas M. C. , Priede I. G. , Armstrong J. D. , Gindy A. N. Z. , De Vera L.
Published: January 2006

Heart rate telemetry records of up to 5 days duration were obtained from pike living in Lochs Kinord and Davan, Scotland. Applying metabolic rate correlations it was found that mean metabolic rate (R) was 1.5 times standard metabolic rate (Ra), The fish rarely worked near their metabolic limits. Activity metabolism (Ra) was much higher than estimates based on mean swimming speed and comprised up to 10% of R. Most activity metabolism was the result of localized bursts of activity. Less than 10% of activity showed evidence of oxygen debt. Specific Dynamic Action or feeding metabolism (Rf) comprised 15–25% of R. Food intake estimated from heart rate was 1.5% wet body weight day−1, consumed in the form of small items captured during the day and digested during the afternoon and night.
Mechanisms of digestion in the marine herbivore, the luderick, Girella tricuspidata (Quoy and Gaimard)
Authors: Anderson T. A.
Published: January 2006

The effect of feeding frequency on the mechanisms of digestion in the mucosa and contents of the gastrointestinal tract of the luderick, Girella tricuspidata (Quoy and Gaimard), was determined. Use was made of the variation in utilization frequency of Enteromorpha intestinalis by C. tricuspidata fed according to two different regimes to determine the importance of these digestive mechanisms in algal digestion.

The contents of the oesophagus and stomach of fish fed ad libitum were consistently acidic whilst those from fish deprived of food were highly variable and more alkaline. The contents of the pyloric caeca. intestine and rectum were slightly alkaline in both groups.

The number of microorganisms found in the digestive tract increased with a reduction in food availability. There was no significant cellulase activity in any of the animals tested.

Amylase and lipase were found in the pyloric caeca, intestine and rectum, but were not present in the oesophagus or stomach. Lipase activities were highly variable. Although some protease was found in the posterior portion of the gut, the majority of the activity occurred in the oesophagus and stomach.

Generally, amylase, lipase, and protease activities were unaffected by a change in the feeding regime of the fish from being fed ud libitum to being fed for a period of 24 h every 5 days. It is concluded that a reduced activity of enzymes that hydrolyse algal cell contents is not the reason for the lower utilization efficiency of food‐deprived fish.

It is clear that the only difference in digestive mechanisms between fish fed ad libitum and fish fed infrequently is the variation in pH of the foregut. It is considered likely that the increased acidity of the foregut of animals fed ad Iibilum facilitates hydrolysis of the algal cell walls and allows greater utilization of algae by these fish.
The pericardium facilitates pressure work in the eel heart
Authors: Franklin C. E. , Davie P. S.
Published: January 2006

An in siru perfused eel (Anguilla dieffenbachü) Gray 1842) heart was used to investigate the role of the pericardium in cardiac function. Hearts with intact pericardia were compared with hearts in which the pericardia were either punctured or opened completely. Cardiac function was assessed at low and high adrenaline levels by determining: maximum cardiac output; maximum sustainable output pressure; power output under maximal filling and output pressures; and maximum power output. Puncturing a small hole in the pericardium equalizing ambient and intrapericardial pressures had little effect on cardiac function and performance. Opening the pericardium, thereby fully exposing the chambers of the heart, severely limited the heart's ability to do pressure work. This effect was reversed at high adrenaline concentrations. Flow related work, and maximum power output levels were maintained after opening the pericardium.
Food habits, ontogenetic diet shift and selectivity in Zeus faber Linnaeus, 1758
Authors: Stergiou K.I. , Fourtouni H.
Published: January 2006

The feeding habits of Zeus faber Linnaeus, 1758 were studied by examining digestive tracts in I2 size classes of individuals. It is a stenophagus species which begins life feeding almost exclusively on zooplankton until it is about 80 mm long, then switches gradually from zooplankton to small demersal fish, and finally when > 140 mm switches to feeding exclusively on benthic and demersal fish. Mysids were the most important food component in Z.faber < 141 mm and Cepola macrophthalma (Linnaeus, 1758) in Z.fiber > 140mm. The switch to fish prey was followed by a greater body weight per unit length. Z.faber > 140 mm selected primarily for small‐and intermediate‐sized C. macrophthalma (and to a lesser extent for Callionymus maculatus Rafinesque‐Schmaltz, 1810, Gaidropsarus sp. and Trigla Iyra Linnaeus, 1758). Our results suggested that the ratio of vertical to horizontal dimension of prey, the motion and coloration of prey as well as the visual capabilities and perceptual potentialities of Z. faber may all in a synergetic fashion account for prey type and size selection and the positive relations found between the size of Z.faber and the size and variance of its ingested prey. Possible co‐evolutionary relationships between Z.faber and C. macrophthalma are also discussed.
Distribution of fishes on the Cretan shelf
Authors: Tsimenides N. , Tserpes G. , Machias A. , Kallianiotis A.
Published: January 2006

Information on the abundance of demersal fishes on the shelf of Crete has been collected through a 3‐year bottom trawl survey carried out at fixed sampling stations. Cluster analysis identified three major station‐groups delimited by the nature of the substrate. Two of the identified substrate zones were situated on the continental shelf while the beginning of the third zone coincided with the start of the continental slope. Discriminant analysis applied to the abiotic variables defined that depth was the most important variable in discriminating between the identified groups. Discriminant analysis also identified that the most important species in discriminating among station‐groups were Capros aper (Linnaeus, 1758), Gadicuh argenieus argenteus Guichenot, 1850, Merluccius merluccius (Linnaeus, 1758), Mullus surmuletus Linnaeus, 1758 and Spicara flexuosa Rafinesque, 18 10. Association analysis revealed few species pairs having significant associations which in most cases seem to be related to the reproductive migration of these species. The results demonstrate that there is a pronounced change with the substrate and by extension with depth in the ichthyofaunal composition of the shelf of Crete. It has also been suggested that there may be a particular relationship between the fish communities of the two zones of the continental shelf.
A new method to determine sex and gonad size in live fishes by using ultrasonography
Authors: Mattson N. S.
Published: January 2006

A method to determine, non‐invasively, sex and gonad size employing ultrasonography and using Atlantic salmon, Salmo salar Linnaeus, as an example, is described. Although gonads of immature males may be difficult to discern, gonads of females are always visible and hence sexing is possible by deduction. Gonad diameter can be estimated by ultrasonography; the correlation coefficients between ultrasonographic and ruler‐derived measurements were 0.926 for females and 0.754 for males. The appearance of ultrasonographic images of the gonads during sexual maturation are described. The results are discussed and suggestions made to improve the quality of images and reliability of measurements.
Spread of parasites and diseases of aquatic organisms by acclimatization: a short review
Authors: Bauer O. N.
Published: January 2006

The influence of transportation and acclimatization of fishes and shellfishes on their parasites and pathogens is discussed. It has been shown that aquatic organisms lose most of their parasites during the period of establishment, but some species may remain. In most instances these are parasites with direct development (Myxosporea, Monogenea, Crustacea). Species with intermediate hosts, but which utilize many species of invertebrates, establish more easily than those which have specific invertebrate intermediate hosts. If there are closely related host species to those introduced into the water body, parasites brought to it can transfer to these related species. This may result in a high infection of the native species and significant mortality.