bluuebunny/crossref_metadata_2025_split huggingface dataset:
Host‐constrained epidemiology of the fish tapeworm Ligula intestinalis (L.)
Authors: Wyatt R. J. , Kennedy C. R. 
Published: January 2006

Investigations into the biology of the roach, Rutilus rutilus (L.), and Ligula intestinalis (L.) populations at Slapton Ley, Devon were carried out between October 1982 and December 1984, and additional data collected from the lake since 1977 have been re‐analysed. The Ligula population exhibited some unusual features: a limited specificity, a persistently low abundance and a scarcity of multiple infections. The population dynamics of the roach were also unusual in that the individual growth rate was one of the fastest in Britain, the survival was very poor and the year classes tended to alternate in strength. Whether the unusual epidemiology of Ligula could be explained by the unusual population dynamics of the roach is investigated.The transmission period of Ligula to the roach was limited to their first few months of life, probably due to a limited period of feeding on copepods by the fry. This narrow transmission window was almost certainly the major factor that has prevented the abundance of Ligula plerocercoids attaining high levels in the fry or of increasing in subsequent years, and has resulted in their abundance being determined entirely by transmission events to the fry. The limited transmission period has also caused the life‐cycles of the roach and Ligula populations to become synchronized. At other localities, the abundance of Ligula is typically high, and can have a significant effect on the mortality of the host population, but, with the low abundance at Slapton, Ligula‐induced roach mortality was insignificant. The rapid growth of the roach fry was the most likely explanation for the limited period of feeding on copepods, and the large size, short life‐span and low abundance of the roach probably also constrained the build‐up of the Ligula population in the lake. The random frequency distribution and scarcity of multiple infections was not considered unusual in view of the very low plerocercoid abundance. The very low abundance of Ligula, the separation of the spawning of roach and rudd in time and space, and the scarcity of rudd may account for the absence of infection in this species. It was concluded that the Ligula population in Slapton Ley was being constrained by the atypical population dynamics of the roach, and not vice versa as theory predicts.
Seasonal changes in the intestinal mucosa of winter flounder, Pseudopleuronectes americanus (Walbaum), from Passamaquoddy Bay, New Brunswick
Authors: McLeese J. M. , Moon T. W. 
Published: January 2006

Winter flounder from Passamaquoddy Bay, N.B. undergo an annual fast from November to May which results in a decrease in the slope of the length‐weight relationship (3·17 to 2·54), in the condition factor (9 to 12%), in the liver (75%) and white muscle (24%) lipid contents, and an increase in muscle water content (2·4%). Winter flounder appear to have sufficient lipid reserves to support the winter fast, as muscle water content declined only at the onset of feeding.The intestine could be divided into pyloric caeca (4), foregut, midgut and hindgut. Mucosal folding was reduced in all sections of the intestine during the fast. Goblet cell number declined, but little change in enterocyte ultrastructure was observed. Intestinal length remained the same, although the caeca shortened. Overall, mucosal mass declined by 57% from May to January, while surface area declined by 50%. This value is less than that in literature reports for a fast of shorter duration in freshwater rainbow trout. We propose that the continued need for salt and water transport for osmoregulation maintains the proximodistal gradient of mass and surface area and ameliorates the effect of starvation on mucosal mass and area.
Effects of different photoperiods on the reproduction of the barbel, Barbus barbus (L.), reared at constant temperature
Authors: Poncin P. 
Published: January 2006

The role of photoperiod as an environmental factor controlling reproduction, particularly the duration and ending of the breeding season, in the barbel was investigated by tank experiments. The experiments used a population of barbel matured in captivity which were stripped of eggs at frequent intervals: 10–15 'spawnings’for each female were obtained at 15‐day intervals.A decreasing photoperiod (16·5 light: 7·5 dark→8L: 16D), for an annual cycle contracted to 6 months duration, inhibited the spawning of both female and male fish. This allowed two periods of reproduction (February‐May and September‐November) within one year. Under natural or constant (10L: 14D) photoperiod conditions, spawning came to an end spontaneously. The rate (accelerated, slow or natural) of daylength increase did not affect the onset of spawning.
Observations on the colours of lumpsuckers, Cyclopterus lumpus L.
Authors: Davenport J. , Thorsteinsson V. 
Published: January 2006

Ripe unfertilized eggs derived from fish landed at two Icelandic ports were predominantly red and yellow‐red, but a small proportion were red‐purple. There was a significant difference between the frequencies of hues of eggs from the two landing places. During the phase of blastula formation, fertilized red‐purple eggs showed no discernible change in either hue or chroma. However, as the gastrula formed and covered the yolk, the chroma declined dramatically, although the hue remained unaltered. When the embryo formed, the chroma continued to decrease and the hue also began to change as the red‐purple pigment disappeared from the yolk and the orange‐yellow oil of the yolk became more visible.The most common plasma colouration in male fish collected at Hafnarfjordur and Husavik was red, but the observed hues covered 60% of the visible spectrum, ranging from green to purple. No significant differences between Hafnarfjordur and Husavik males in terms of hue or value were discerned, but there was a significant difference in chroma score. Female plasma hues were almost as variable as the males (spanning 45% of the visible spectrum) but centred in the green‐yellow zone. Plasma, subcutaneous jelly and skin colours were closely linked.Fish from the oceanic feeding grounds were all green in skin colour, whatever their age or sex; it is suggested that this colouration has a cryptic function in the near surface waters inhabited by lumpsuckers.
Larval competition for food between wild and hatchery‐reared ayu, Plecoglossm altivelis Temminck et Schlegel, in culture ponds
Authors: Uchida K. , Tsukamoto K. , Ishii S. , Ishida R. , Kajihara T. 
Published: January 2006

To examine the larval competition between wild and hatchery ayu in the culture ponds, mixed rearing of 580 000 wild and 520 000 hatchery larvae was carried out in two 25‐m3 ponds for 3 months, in contrast to the control in which 860 000 wild larvae were reared in another pond.The number of wild larvae in the mixed‐rearing treatments decreased rapidly 20 days after the start of mixed rearing, in contrast to hatchery larvae. Mortality of wild larvae was almost 100% at the end of the experiment (3 months), while the hatchery larvae showed the usual survival rate of 15–16%. In the control pond, however, 16% of the wild larvae survived. The wild larvae grew much slower (0.10mmday ‐1) than the hatchery larvae (0·26 mm day ‐1) in the mixed‐rearing ponds, whereas the wild larvae in the control pond showed almost the same growth rate (0·24 mm day ‐1) as hatchery larvae. On day 6 the gut fullness of wild larvae was only 30% of that of the hatchery larvae in the mixed‐rearing experiments. On day 46 the wild larvae occurred deeper in the mixed‐rearing ponds than the hatchery larvae. This depth difference in vertical distribution appeared to cause a disadvantage for the wild larvae in the competition with hatchery larvae, since the food was supplied at the surface. Thus, the wild larvae starved and died.
Production of juvenile Atlantic salmon, Salmo salar L., and brown trout, Salmo trutta L., within different sections of a small enriched Norwegian river
Authors: Bergheim A. , Hesthagen T. 
Published: January 2006

Growth, density and production of juvenile Atlantic salmon and brown trout were studied in three different sections of the Kvassheimsåna River in south‐western Norway from 1979 to 1983. Section 1. in the upper part of the river, is located above a waterfall impassable for migratory salmonids and is surrounded by grazing land. Sections 2 and 3, in the middle and lower parts of the river, are influenced by agricultural activity. Total nitrogen concentration varied between 250 and 1000 μg l −1 in section 1 and 1500 and 2500 μg l−1 in sections 2 and 3. Total phosphorus (Tot‐P) concentrations also increased with decreasing altitude: 19–46 μg l−1 in section I and 31–101 μg l −1 in sections 2 and 3.The number of 0 + salmon in sections 2 and 3 varied between 30.1 and 167.8 specimens 100 m −2, with means 90.2 and 95.2 specimens 100 m −2:, respectively; the density of 1 + salmon, with mean values of 16.3 and 51.0 specimens 100m−2 was significantly correlated with the original fry density. The growth rate of 0+ salmon was not inversely related to cohort density, but was significantly so for 1 + salmon. Mean annual salmon production in section 2 was 1595 g 100 m−2 year 1, and in section 3 was 841 g 100m−2 year 1. A logarithmic function gave the best curve fit between salmon production and mean annual biomass. Thus, production levelled off for the highest values recorded in section 2, and perhaps approached the carrying capacity of the stream. A multiple regression analysis showed that yearly variation in 1 + salmon density was the single factor accounting for most of the total variability in production (60%). Variation in water temperature and nutrient content were not significantly related to variation in fish production.Densities of brown trout were low in all sections (<20 specimens 100m −2). Fry density was highest in section 3 and parr density in section 1. All age groups of sympatric brown trout grew significantly faster in sections 2 and 3 compared with allopatric brown trout in section 1.
Seasonal variations in biochemical and physicochemical properties of actomyosin and energy content of the liver, gonads and muscle of mature Argentine hake, Merluccius hubbsi Marini
Authors: Montecchia C. L. , Crupkin M. , Truccos R. E. 
Published: January 2006

Seasonal variations in energy content of liver. gonads and muscle, and the condition factor (K) of mature hake, were investigated. High energy content values were found in the liver after spawning and during thegonadal restingperiod. Lowenergycontent valuesin liverand highenergycontent values in gonads were observed during the gonadal growth period. In some periods of the reproductive cycle, low values of energy content of muscle were found.The condition factor profile was similar to the energy content profile of liver and muscle. Physicochemical and biochemical properties of actomyosin were monitored by reduced viscosity and Mg2+‐ATPase activity. The profiles of these properties were similar to that of the condition factor.
Diet composition and prey preference of tench, Tinca tinca (L.), common bream, Abramis brama (L.), perch, Perca fluviatilis L. and roach, Rutilus rutilus (L.), in two contrasting gravel pit lakes: potential trophic overlap with wildfowl
Authors: Giles N. , Street M. , Wright R. M. 
Published: January 2006

The abundance of benthic macroinvertebrate taxa and the relative abundance of zooplankton taxa were compared with the diet of bream, tench. perch and roach from two gravel pit lakes during May‐July 1986 and 1987. Significant food preferences were demonstrated between species and between lakes. Chironomid pupae dominated the macroinvertebrate diet of perch, roach, ate predominantly either Spirogyra sp. (St Peters Lake) or Daphniu hyalina (Main Lake).The Main Lake, bream fed largely upon chironomid larvae and the bivalve Sphuerium but in St Peters Lake they positively selected a variety of less abundant benthic invertebrate taxa. Bream switched from benthos to zooplankton in the Main Lake in 1986. Tench ate large numbers of Aselhs and showed positive selection of various macroinvertebrate prey in St Peters but ate D. hjulim in Main Lake. Tropic overlap for chironomids and other macroinvertebrate prey was demonstrated between perch, bream and tench, and potentially with wildfowl which used the gravel pits for breeding and wintering.
Fish of the Amazonian IgapÔ: stability and conservation in a high diversity‐low biomass system
Authors: Henderson P. A. 
Published: January 2006

Water depth in the Amazon basin can differ by more than 11 m between low and high water periods in the annual cycle. When the water is high, the forest streams inundate the surrounding low‐lying forest creating vast lakes. Where the water originates from the forest it is rich in humic acids and low in dissolved nutrients. Such waters are termed blackwaters. Igapó is the specialized inundation forest of blackwater regions. Until recently it was generally held that the blackwater fauna was impoverished and of low biomass. However, recent studies have shown that these waters hold a specialized fauna living within and upon allochthonous input from the forest. Within submerged litter banks a diverse ichthyofauna forming dense local populations has been found.Information on the spatial organization, population density and food web of this fauna will be presented. It is argued that this community is highly vulnerable to deforestation and its long‐term future can only be assured if the forest is conserved. This is not to suggest that these fish are not adaptable to disturbance as the community has evolved to live with changing water levels and the loss of submerged wood and leaf‐litter habitat. It is a remarkable example of a climax community exhibiting high diversity and low total population sizes within a variable habitat. Its conservation is of economic importance to the local human population whose diet includes a high proportion of fish.
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.
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.
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.
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.
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.
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.
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.