bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of capture and recovery on plasma levels of cortisol, lactate and gonadal steroids in a natural population of rainbow trout
Authors: Pankhurst N. W. , Dedualj M.
Published: April 2005

Rainbow trout were captured by angling from a run of spawning fish on the Tongariro River in northern New Zealand, to examine the effects of catch and release angling on stress and reproductive parameters. Fish were blood sampled immediately after capture at playing times of <5 or 15 min, or after 1 or 24 h of recovery in stream enclosures. Plasma samples were assayed for cortisol (F), lactate, testosterone (T), 17β‐oestradiol (E2), and 17a,20β‐dihydroxy‐4‐pregnen‐3‐one (17,20βP). Plasma F levels were similar to those of hatchery stocks of rainbow trout, at capture, and became significantly elevated 1 h after capture. Plasma F was still clevated in some fish 24 h after capture. Plasma lactate levels began to increase 15 min after capture, were further elevated 1 h after capture, and had returned to normal 24 h after capture. We proposed that metabolic recovery had occurred but that some animals were still experiencing some degree of stress, possibly in response to holding conditions in the river. Both plasma T and E2 were depressed 24 h after capture, whereas there was no change in plasma 17,20βP. This is consistent with other findings showing that acute stress is associated with depression of plasma levels of T and E2. There was no mortality as a result of capture or any of the handling protocols. We conclude that catch and release angling will result in negligible mortality, but may have an inhibitory effect on some reproductive processes.
Redistribution of juvenile salmonid fishes after localized catastrophic depletion
Authors: Armstrong J. D. , Shackley P. E. , Gardiner R.
Published: April 2005

Juvenile Atlantic salmon and brown trout were depleted at three sites (c. 108–380 m2) of a natural stream during the summer months of 1991 and 1992. Local population changes and movements of fish marked in sections adjacent to each depleted area were monitored thereafter. There was very little movement of marked salmon parr into the central regions of the depleted areas following the immediate post‐marking period. Upstream movement by young‐of‐the‐year fish from high density sections in mid‐late summer was noted for trout but not salmon. Unmarked 1‐year‐old salmon parr immigrated into depleted areas in June 1992, and the pattern of recolonization was consistent with migration upstream from the adjoining river. It is concluded that resident salmon were very strongly site‐attached and resource tracking was of no functional significance as a compensatory mortality mechanism. The occurrence of a long distance migratory component in the population during early‐mid summer indicates that this, rather than local resource tracking, constitutes a potential compensatory mechanism.
Temperature effects on the incorporation of strontium in otolith of Japanese eel Anguilla japonica
Authors: Tzeng W. N.
Published: April 2005

The effects of temperature on somatic and otolith growth and the incorporation of strontium in otolith of the Japanese eel, were studied in laboratory‐reared and field‐caught eels. The somatic and otolith growth rates of the eel increased significantly with temperature and were estimated as approximately 0·096 mm t.l, (P<0·01) and 0·36 μm in otolith diameter per degree‐day (0·01<P<0·05), respectively. In contrast, the Sr/Ca ratio in the otoliths was negatively correlated with water temperature. The feasibility of using the otolith Sr/Ca ratio to reconstruct environmental temperature history of the eel is discussed.
Life histories as sampling devices: optimum egg size in pelagic fishes*
Authors: Wootton R. J.
Published: April 2005

In teleosts, egg size is an important determinant of larval size. The latter determines where larvae start feeding in the size spectrum of biomass particles. Egg and larval size also determine the size range of predators exploiting these early ontogenetic stages. Thus, egg size is important in determining the particle size range sampled during ontogeny. However, egg size also largely determines how many can be produced by a female. Optimum egg size for marine, pelagic fishes was estimated using a modification of a model developed by Ware. A numerical analysis using empirical information on size and temperature dependent mortality and growth in pelagic, marine systems suggests that allometry of size‐dependent mortality and temperature are significant factors in determining optimum egg size. Allometry of mortality will depend on the frequency of encounters between particles of different sizes. Both empirical and modelling studies of such frequencies in pelagic and other environments are required.
Differences in digestion and absorption of dietary protein in Atlantic salmon (Salmo salar) with genetically different trypsin isozymes
Authors: Torrissen K. R. , Lied E. , Espe M.
Published: April 2005

Digestion and absorption of dietary protein were studied through facilitation of amino acid in the plasma and white muscle after a single feeding. The comparison was made between Atlantic salmon with and without trypsin isozyme TRP‐2*92. Higher absorption of dietary protein was associated with the presence of the isozyme, as the post‐prandial total levels of free amino acids (FAA) in both plasma and white muscle were significantly higher in salmon with the isozyme than those in salmon without it. Higher digestion rate of the dietary protein in salmon carrying the isozyme was indicated by faster elevation of essential FAA in the plasma and of overall FAA in their white muscle. Other indications which suggest differences in nitrogen metabolism between salmon with and without the isozyme were the observations of significant differences in (a) the levels of lysine, hydroxyproline, alanine, aspartic acid, β‐alanine, threonine, valine and a nitrogen‐containing compound taurine in plasma, and (b) the levels of alanine, glutamic acid, glycine and anserine in white muscle.

Trypsin activity in the pyloric caeca showed less response to feeding than that in the intestine, but it may have consequence for growth as its activity was significantly higher in growing fish than in non‐growing fish.
Cellular responses in the skin of rainbow trout (Oncorhynchus mykiss) exposed to Rhine water
Authors: Iger Y. , Jenner H. A. , Wendelaar bonga S. E.
Published: April 2005

Trout, Oncorhynchus mykiss, were exposed to water from the Rhine for 24 days and their skin examined by light and electron microscopy. Relative to control fish mitotic figures were common and seen throughout the epidermis. Pavement cells in fish exposed to Rhine water contained significantly more secretory vesicles than control fish. Necrotic pavement cells were apparent after 24 h, and apoptotic cells from day 4 on. Mucous secretion was intense and the differentiation of mucous cells was stimulated. Some of these cells synthesized mucus of high electron density, probably of a serous composition. Leucocytes invaded the dermis and epidermis, and towards the end of the experiment many apoptotic and necrotic lymphocytes were found. In the dermis fibroblasts were abundant and actively producing collagen. Pigment containing cytoplasmic extensions of melanocytes penetrated into the epidermis. After 14 and 24 days of exposure many pigment cells, melanocytes, iridocytes and xanthocytes became apoptotic. Most of these changes are known from fish exposed to heavy metals, acid water or other stressful treatments, indicating that exposure to Rhine water is a stressful experience for trout.
Differences in diet and behaviour of sympatric saithe and pollack in a Scottish sea loch
Authors: Sarno Benedetto , Glass Christopher W. , Smith Gordon W.
Published: April 2005

Two closely related and morphologically similar gadoid predators, saithe, Pollachius virens and pollack P. pollachius, coexist in close proximity on a submerged reef in Loch Ewe, Scotland. The degree of overlap between the niches of these two gadoids in the wild was investigated by means of acoustic tracking, underwater television and an examination of stomach contents. Simultaneous tracking of individuals of both species revealed that pollack generally swim more slowly than saithe, restricting much of their movements to the submerged reef. Saithe ranged more widely around the reef as part of a school during the day, moving onto the reef at night. Video recordings showed that saithe swam actively and foraged in small groups and took prey items from the kelp, whereas pollack tended to remain solitary, maintained station at particular locations for minutes at a time and apparently used the kelp forest exclusively for cover. Although the dietary overlap of the two predators was considerable, their intake of different prey groups varied. In particular, within the crustaceans, saithe took amphipods, while pollack took mysids. In addition, saithe consume a wider range of prey than pollack. The relationship between the movement patterns and the use of food resources by these two predators is discussed, with particular emphasis on differences in feeding strategies.
Theoretical reflections on the growth of three‐spined stickleback morphs from island lakes
Authors: Hart Paul J. B.
Published: April 2005

A stochastic dynamic programming model is developed of prey choice by three‐spined stickleback. The fitness function relates growth ratekfrom the von Bertalanffy growth equation to stomach fullness. It is shown that the model predicts experimental results. Emphasis is given to handling time as an important variable determining diet. Two handling time vectors are defined, each of which is used to represent the benthic and limnetic morphs found in Paxton Lake, Texada Island, BC, Canada. The model is then used to examine the growth rates to be expected from these two morphs in habitats which vary in the distribution of encounter probabilities with each prey size and the distribution of prey size specific risk of predation. The benthic morph grows faster than the limnetic in most habitats but often the two do as well as each other. In the one habitat where limnetics grow better, they do so because their shorter handling times for small prey counteract the effect of a constant but high risk of predation. The results are discussed in the context of what is known of the ecology and evolution of the two morphs in Paxton Lake. It is concluded that the model is only dealing with conditions in the benthic habitat and data are required on encounter rates and prey size distributions in the linnetic habitat so that the model can be used to predict growth for limnetics.
Accelerating the onset of piscivory: intersection of predator and prey phenologies
Authors: Juanes Francis , Buckel Jeffrey A. , Conover David O.
Published: April 2005

Piscivorous fishes tend to be able to consume other fishes early in development and generally experience a dramatic increase in growth after the ontogenetic diet shift to piscine prey. Hence, an acceleration of the onset of piscivory may be favoured strongly by natural selection. Temperate freshwater piscivores, for example, becomes piscivorous at a relatively young age by spawning in advance of, and thereby achieving a size advantage over, the young of their piscine prey. Research in various North American estuaries suggests that young‐of‐the‐year (YOY) bluefish Pomatomus saltatrix, an offshore‐spawning estuarine‐dependent marine fish, may accelerate the onset of piscivory by being advected to higher latitudes and timing their estuarine entry with the appearance of small coastal fishes. This hypothesis was tested by: (i) determining the annual recruitment date of YOY bluefish and their prey; and (ii) examining the diet and prey size preferences, and predator size‐prey size relationships, of YOY bluefish in two different estuarine systems: Great South Bay, and the lower Hudson River. Results suggest that the relationships between bluefish and their prey are determined by a complex interplay between recruitment timing of both predator and prey, prey size availability, predator selectivities, and the timing of vernal warming. It is concluded that YOY bluefish migration into northern estuaries at an advanced size provides them with a predatory size advantage over their principal piscine prey thereby facilitating an early diet shift to piscivory white minimizing the time spent as planktivores.
Are all prey created equal? A review and synthesis of differential predation on prey in substandard condition
Authors: Mesa Matthew G. , Poe Thomas P. , Gadomski Dena M. , Petersen JamesH.
Published: April 2005

Our understanding of predator‐prey interactions in fishes has been influenced largely by research assuming that the condition of the participants is normal. However, fish populations today often reside in anthropogenically altered environments and are subjected to many kinds of stressors, which may reduce their ecological performance by adversely affecting their morphology, physiology, or behaviour. One consequence is that either the predator or prey, or both, may be in a substandard condition at the time of an interaction. We reviewed the literature on predator‐prey interactions in fishes where substandard prey were used as experimental groups. Although most of this research indicates that such prey are significantly more vulnerable to predation, prey condition has rarely been considered in ecological theory regarding predator‐prey interactions. The causal mechanisms for increased vulnerability of substandard prey to predation include a failure to detect predators, lapses in decision‐making, poor fast‐start performance, inability to shoal effectively, and increased prey conspicuousness. Despite some problems associated with empirical predator‐prey studies using substandard prey, their results can have theoretical and applied uses, such as in ecological modelling or justification of corrective measures to be implemented in the wild. There is a need for more corroborative field experimentation, a better understanding of the causal mechanisms behind differential predation, and increased incorporation of prey condition into the research of predator‐prey modellers and theoreticians. If the concept of prey condition is considered in predator‐prey interactions, our understanding of how such interactions influence the structure and dynamics of fish communities is likely to change, which should prove beneficial to aquatic ecosystems.
Escape manoeuvres of schooling Clupea harengus
Authors: Domenici Paolo , Batty Robert S.
Published: April 2005

The escape behaviour of schooling herring startled by an artificial sound stimulus was observed by means of high speed video filming. Response latencies showed two distinct peaks, at 30 ms and c. 100 ms. Escape responses belonging to the two latency groups showed different turning rates during the first stage of the response, and showed different escape trajectories. We suggest that long latency escapes may be responses to startled neighbours or simply weak responses to the sound stimulus. In addition, the different contraction rates during the C‐bend formation seen in the two latency groups may imply differences in the neuronal commands. The escape responses of herring were directed away from the stimulus more often than towards it (88% of the total). These away responses were more common in long latency responses, suggesting that the latter enable herring to be more accurate in discerning the direction of the threat. Startled fish contracting their body towards the stimulus (performing a towards response) appear to correct their escape course, since their escape trajectory distribution is non‐uniformty distributed around 360° and directed away from the stimulus. We hypothesize that when herring are schooling, the ability of each fish to correct its trajectory following turns towards the stimulus is enhanced.
The effect of light intensity on the nightly movements of juvenile Atlantic salmon alevins away from the redd
Authors: Fraser Neil H. C. , Auntingford Felicity , Thorpe John E.
Published: April 2005

Atlantic salmon (Salmo salar) alevins move away from the redd predominantly at night time, suggesting that light level is the controlling factor releasing activity. However, the exact relationship between Light level and alevin activity is unknown, so a series of artificial redds was used to monitor alevin movements under various night time incident light levels. Five experimental redds and two controls were run over a period of 3 years. Combining the results gave a significant negative correlation between the numbers of salmon alevins moving away from redds on light nights and light level. This behaviour was interpreted as a negative photoresponse since the frequency of alevin movement away from the redd was dependent on the light intensity. Two possible explanations as to why alevins may react in this way to light level were considered. Firstly, the behaviour could have evolved to ensure that alevins only move away from the redd when they are least likely to be caught by a predator or secondly, retinal developmental differences between alevins could have led to the observed behaviour.
Fish and game: a game theoretic approach to habitat selection by predators and prey*
Authors: Hugie Don M. , Dill Lawrence M.
Published: April 2005

Given a choice between habitats differing only in food availability, prey are known to select the habitat providing the highest energetic return. They do so in a frequency‐dependent manner, accounting for the reduction in food availability caused by the presence of other individuals; this results in the well‐known ‘Ideal Free Distribution’, an equilibrium solution to a spatial game. When habitats also differ in predation risk due, for example, to different predator densities, prey also appear able to take this into account. However, in most theory (and most experiments) the predation risk levels in the available habitats are assumed to be fixed. Here we ask what will happen if predators are able to adjust their distribution in response to the habitat choice decisions of their prey, i.e. we model a generalized habitat selection game between predators and prey. We first develop a basic model which captures the essence of the problem, and then expand it to include risk dilution and interference among predators. The model produces several new insights, notably that, in the absence of interference effects, the density of prey in a habitat is determined solely by the inherent‘ riskiness’of that habitat (a habitat measure independent of predator density, which might reflect cover or light levels, for example) and is unaffected by habitat productivity (a measure of the food resource available to the prey). When interference exists between predators, ptey density is also determined by habitat productivity but to a lesser extent than by riskiness. Consequently, prey may not respond significantly to changes in relative food resource availability among habitats if their predators are also free to choose the habitat which maximizes their expected fitness. We consider briefly the potential applications of game theory to diel vertical migration and other fish predator‐prey scenarios.
The ultrastructure of the intestinal epithelium in fishes with different types of feeding
Authors: Kuperman B. I. , Kuz'mina V. V.
Published: April 2005

The ultrastructure of the intestinal epithelium has been studied in three species of freshwater fishes, differing from one another in the type of feeding. The pike (a typical predator), the burbot (a predator‐facultative benthophage), and the bream (a typical benthophage) were examined. The differences in the condition of epithelial ceils and peculiarities in the structure of the brush border of enterocytes in fishes have been revealed in winter periods. The role of the brush border of enterocytes in the increase of the digestive and transport surface of the intestine in fish is discussed.
Social control of male sexual maturation in the swordtail characin, Corynopoma riisei
Authors: Bushmann P. J. , Burns J. R.
Published: April 2005

The presence of adult male Corynopoma riisei was found to inhibit the maturation of juvenile males. Males in a conspecific community tank took longer to mature and did so at increasingly slower rates compared to isolated controls, providing a positive correlation between size and time of maturational onset. The inhibitory effect increased with greater numbers of adult males. The first males to mature did so at accelerated rates, suggesting positive as well as negative control. Tanks in which adult males were removed as soon as maturation was complete showed an intermediate pattern, with no lengthening of the maturational time course but an increase in standard length. Histological examination revealed immature males with lengths greater than the control range; these appear to represent inhibited animals. Both the testes and pituitary gonadotropic zone of these males appeared undeveloped, arguing for inhibition at least at the hypothalamic level. This phenomenon has also been described in poeciliids The presence of a similar complex mechanism in two distant groups of fishes suggests convergent evolution. It also suggests that this phenomenon may be physiologically possible for a wide range of fish species.
The dorsal groove and associated structures on the head of the sucking loach, Gyrinocheilus aymonieri (Cypriniformes)
Authors: Benjamin M. , Ralphs J. R.
Published: April 2005

A prominent transverse groove is present on the snout of the adult sucking loach, Gyrinocheilus aymonieri. It is absent in juveniles. The groove is formed by fibrous thickenings of the dermis that create skin folds at its anterior and posterior margins. It accommodates movement of the joint between the maxillae and the neurocranium. The anterior fibrous thickening also provides anchorage for fibrous strands that partition dermal mucochondroid in the upper lip of the oral sucker into distinct segments. This structure forms a buffer that protects the delicate premaxillary bones when fish probe the substrate for food.
Numbers of muscle nuclei and myosatellite cell nuclei in red and white axial muscle during growth of the carp (Cyprinus carpio)
Authors: Koumans J. T. M. , Akster H. A. , Witkam A. , Osse J. W. M.
Published: April 2005

We determined the percentages of muscle fibie nuclei and satellite nuclei over a growth range of carp (Cyprinus carpio), as the increase in the number of muscle fibre nuclei is an important aspect of the increase in muscle mass, and myosatellite cells are believed to be the source of new muscle fibre nuclei. In white as well as in red axial muscle the percentage of the nuclei present in muscle that are muscle nuclei (muscle fibre nuclei+myosatellite nuclei) remained constant during growth (54 and 32% respectively). The difference in the percentage of non‐muscle nuclei between white and red axial muscle is mainly caused by the higher content of endothelial nuclei in red axial muscle.

In white axial muscle the DNA/protein ratio (nucleus/sarcoplasm ratio) decreased between 3 and 15 cm S.l. In red axial muscle we found a continuous decrease in DNA/protein ratio over the entire investigated size range (3–50 cm s.l.). This may be related to a longer occurrence of hyperplasia in red than in white axial muscle.

In both fibre types the percentage of muscle nuclei being myosatellite nuclei decreased with increasing length, In white axial muscle it decreased from about 5% in carp of 5 cm s.l. to less than 1% in carp of 20 cm S.L.; for red muscle these values were 11 and 3% respectively.

For white axial muscle we calculated that, especially in larger fish, the myosatellite ceils alone cannot account for the increase in the number of muscle fibre nuclei during growth. The percentage of proliferating nuclei in muscle tissue, measured by the uptake of 5‐bromo‐2′‐deoxy‐uridine, is high enough to account for the total increase in nuclei. So indirect evidence is available that another cell type present in the muscle tissue may also be involved in the formation of additional muscle fibre nuclei.
Parasite community diversity in two Mediterranean labrid fishes Symphodus tinea and Labrus merula
Authors: Campos A. , Carbonell E.
Published: April 2005

Examination of 111 peacock wrasse [Symphodus tinea (L.)] and 97 brown wrasse (Labrus merula L.) from the Valencian coast (Spain) yielded 24 metazoan parasite species (11 Digenea, three Cestoda, four Nematoda. one Acanlhocephala, five Crustacea). Eighteen species were from 5. tinea and 17 from L. merula; 11 of the 24 species were common to both hosts. Brillouin's diversity index, was applied to fully censused parasite infracommunities. This is the first time that all the metazoan parasites (internal and external) in any position in the host have been analysed for diversity. High values of prevalence, intensity, and diversity parameters indicate that these labrid fishes support diverse parasite communities. This may be due to their diverse diet, mainly marine invertebrates which are possible intermediate hosts; they also support certain netnatodes and crustaceans which have direct life‐cycle.
The testicular main ducts and the spermatic ducts in some cyprinid fishes—II. Composition of the seminal fluid
Authors: Lahnsteiner F. , Patzner R. A. , Weismann T.
Published: April 2005

The composition of the organic compounds of the seminal fluid, pH values and osmolalities were investigated in three cyprinid species, the bleak (Alburnus alburnus), the chub (Leuciscus cephalus) and the zaehrte (Vimba vimba). The seminal fluid contains monosaccharides (glucose, fructose, galactose, xylose), lipids (cholesterol, fatty acids, phosphatidylcholine, glycolipids) and proteins, and exhibits activities of acid phosphatase, β‐glucuronidase, proteases and to some extent of alkaline phosphatase. The composition of free amino acids reveals species specific differences.
Expected future reproductive success and paternal behaviour in the sand goby, Pomatoschistus minutus (Pisces, Gobiidae)
Authors: Lindström K. , Wennström C.
Published: April 2005

We studied egg care and guarding behaviour in the paternal sand goby, Pomatoschislus minutus, in relation to egg number and age. A male's expected reproductive success is assumed to increase with larger egg masses and older eggs. Non‐shareable care, i.e. fanning, was higher in larger and older egg masses. Egg age explained 65% and egg mass size 22% of the total variation in the amount of fanning performed by a male. Contrary to expectation, egg removal did not affect a male's fanning behaviour, Males that were approached stayed longer in the nest when they guarded larger egg masses. Males with older eggs were also more reluctant to leave the nest. The time since a male had been chased away from his nest until he returned decreased as the season progressed. The results are discussed in relation to tradeoffs between present and future reproductive events.
Growth and respiration of embryos and larvae of the rabbittish Siganus randalli (Pisces, Siganidae)
Authors: Nelson S. G. , Wilkins S. DeC.
Published: April 2005

Growth and respiration of larval rabbitfish from Guam were examined. Larvae were reared from eggs in 2‐ to 10‐ton tanks and were fed rotifers, Anemia, and artificial feed in succession as development proceeded through metamorphosis. Growth in length was rapid during the 12 h after hatching, then slowed until the larvae began to feed. The yolk sac was usually absorbed by 36 h after hatching. Rates of respiration of larvae and eggs were determined with a dissolved oxygen electrode at various times through development. Larval metabolism increased steadily during the embryonic stages culminating in a metabolic burst immediately after hatching. Respiration rates remained relatively stable from shortly after hatching until the onset of exogenous feeding, after which respiration rates increased with larval size. The respiration rates of post‐yolk‐sac larvae scaled isometrically with larval dry mass. Daily growth of feeding larvae was 27 to 28% of larval dry mass.
Respiratory‐cardiovascular physiology and chloroethane gill flux in the channel catfish, Ictalurus punctatus
Authors: McKim J. M. , Nichols J. W. , Lien G. J. , Bertelsen S. L.
Published: April 2005

A fish respirometer‐metabolism chamber was used to obtain in vivo respiratory‐cardiovascular and chloroethane gill flux data on transected channel catfish (Ictalurus punctatus). Methods used for spinal transection, attachment of an oral membrane (respiratory mast), placement and attachment of blood cannulas and urine catheters are described. Respiratory physiology, cardiac output and chemical extraction efficiencies for 1,1,2,2‐tetrachloroethane (TCE), pentachloroethane (PCE), and hexachloroethane (HCE) were determined on 419–990 g catfish. The overall mean values (± s.d.) for ventilation volume (Qv), effective respiratory volume (Qw), oxygen consumption (Vo2 and percentage utilization of oxygen (U) were 17‐3 ±4–71 h−1 kg−1, 9·8±l·71 h−1 kg−1, 71·6±12·5mg h−1 kg−1, and 49± 10%, respectively, while cardiac output calculated via the Fick Method was 2·4±0·61 h−1 kg−1. Additional measurements were made on ventilation rate (Vr), total plasma protein, haematocrit (Hct), and urine volume; while both arterial and venous blood were analysed for pH, oxygen partial pressure (P02), carbon dioxide partial pressure (Pco2), total oxygen (To2), total carbon dioxide (Tco2) and total ammonia (TAMM). Physiological measurements taken at 24 h were not significantly different from those taken at 48 h and indicated no deterioration of the in vivo preparation. All of these values agreed well with literature values on UTitransected channel catfish, except for Hct which was lower for cannulated animals used in this study. Overall, these data provide strong support for the use of transected channel catfish for in vivo collection of physiological and chemical gill flux data.

The mean initial chemical extraction efficiencies for TCE, PCE and HCE were 41, 61 and 73%, respectively. Chemical clearances (ClX) for these same three chemicals were 5·9, 9·3 and 10·8 1 h−1 kg−1, respectively. The approximate 1: 1 relationship between effective respiratory volume (Qw) and chemical clearance (Clx) indicated that branchial uptake of PCE and HCE was water flow‐limited. Chemical gill flux observed for channel catfish and chloroethanes was similar to that observed for rainbow trout in previous studies and provided further support for the flow‐limited model of chemical flux across fish gills.
Mitochondrial DNA variation suggests river capture as a source of vicariance in Gadopsis bispinosus (Pisces: Gadopsidae)
Authors: Waters J. M. , Lintermans M. , White R. W. G.
Published: April 2005

Gadopsis bispinosus from the Australian Capital Territory (ACT) were genetically similar to a population in north‐east Victoria, but highly divergent from another population in central Victoria. Upper tributary populations from the Murray and Murrumbidgee Rivers were similar probably due to river capture.
Gonadal development and spawning of female ocean whitefish, Caulolatilus princeps (Pisces: Branchiostegidae) in the Bay of La Paz, B.C.S., Mexico
Authors: Elorduy‐Garay J. F. , Ramirez‐Luna S.
Published: April 2005

The developmental stages of the gonads and the spawning season of the ocean whitefish, Caulolatilus princeps, were determined. Gonad maturation is annual, and the spawning season is prolonged, from late autumn to early spring. From November to March, around 80% of the females were in an advanced mode of gonadal development, and in April most gonads were spent. From May to October the gonads were at rest and preparing for the next spawning season.

The gonadosomatic index describes the reproductive activity of the species adequately.
The diet of largemouth bass, Micropterus salmoides, in Lake Naivasha, Kenya
Authors: Hickley P. , North R. , Muchiri S. M. , Harper D. M.
Published: April 2005

Lake Naivasha is a freshwater lake situated in the eastern rift valley of Kenya. Only five species of fish are present, all of which have been introduced. Of these, Oreochromis leucostictus, Tilapia zillii and Micropterus salmoides (largemouth black bass) support an important gillnet fishery with bass also being taken for sport. Until bass reached 260 mm f.l. they depended upon invertebrate food organisms. Thereafter crayfish, fish and frogs became increasingly important the larger the size of the bass. The most important invertebrate prey species was the water boatman, Micronecta scutellaris, followed by chironomid and culicid pupae. Zooplank‐ton was consumed but only in large quantity by fish smaller than 80 mm. For bass over 260 mm the crayfish, Procambarus darkii, was the principal food. The largemouth bass in Lake Naivasha are generalized macro‐predators, feeding principally on free‐living animals of a kind most likely to be found in the littoral zones.
Calcium metabolism in relation to ovarian functions during early and late pregnancy in the viviparous blenny Zoarces viviparus
Authors: Korsgaard B.
Published: April 2005

Calcium metabolism was studied in relation to ovarian functions and embryonic development during early and late pregnancy in the viviparous blenny Zoarces viviparus. The level of total calcium in the maternal serum decreased during pregnancy from 21·7 (± 2·6) to 8·7 (± 1·1) mg 100 ml−1. Calcium in the ovarian fluid surrounding the embryos appeared at a level which was always lower than in the maternal blood. The calcium content of the embryos increased during their development in the ovarian cavity. During early pregnancy, oestradiol‐treatment increased the level of total calcium and alkkali‐labile protein P (vitellogenin) in serum of the maternal organism, but did not have any effect on the level of ultrafiltrable calcium. However, in the untreated females, the post‐ovulatory follicles, believed to act as calyces nutriciae in the pregnant ovary, were able to concentrate the ultrafiltrable calcium above the level in the serum. The activity of injected45Ca per unit plasma and follicular fluid volume was always higher in oestradiol‐pretreated fish when compared with controls over a time course range. Embryos from females, which were not treated with oestradiol, accumulated high levels of labelled calcium and the accumulation was time‐course dependent. Embryos from oestradiol‐treated females showed low levels of tracer accumulation at all samplings and their appearance indicated an overall negative effect of oestradiol. During late pregnancy, labelled calcium showed a rapid turnover within 24 h post‐injection in the maternal blood and ovarian fluid and a large accumulation in the embryos. Calcium influx in embryos, which were incubated with labelled calcium during 72 h in in vitro systems was largest during the initial 4·5–24h time interval.
Mitochondrial DNA variation in River Usk brown trout, Salmo trutta
Authors: Bembo D. G. , Weightman A. J. , Beverton R. J. H. , Cresswell R. C.
Published: April 2005

Mitochondrial DNA (mtDNA) polymorphism in the essentially non‐anadromous River Usk brown trout Salmo trutta population was investigated by restriction analysis. Following mtDNA extraction and purification on caesium chloride density gradients, monomorphic restriction profiles were obtained with HaeIII, HindIII, Sau3AI and Xbal. However, the restriction endonucleases AvaII and HinfIl proved informative. The distribution of four composite genotypes found within the Usk system was heterogeneous, and a fifth genotype appeared exclusively in an outgroup sample from the adjacent River Wye drainage. The source of the observed genetic variation is discussed in relation to estimated divergence times for Usk mtDNA genotypes and the stocking history of the catchment.
The food of Pomatoschistus minutus (Pisces, Gobiidae) in Belgian coastal waters, and a comparison with the food of its potential competitor P. lozanoi
Authors: Hamerlynck O. , Cattrijsse A.
Published: April 2005

Data are presented on the food and gonadosomatic index of Pomatoschistus minutus obtained from the bycatch of a commercial shrimp trawler. P. minutus has a diverse diet including zooplankton and hyperbenthos but mainly epibenthic and benthic animals. During the spawning season males consumed high numbers of Pomatoschistus eggs, presumably after aggressive take–overs of territories. The food of P. minutus is compared to the food of P. lozanoi of the same size classes obtained from the same hauls. In the absence of data on predator and prey abundance the discussion on possible interference competition between the two species remains largely speculative.
Diets of sympatric flatfishes, Hippoglossoides platessoides, Pleuronectes ferrugineus, Pleuronectes americanus, from Sable Island Bank, Canada
Authors: Martell D. J. , McClelland G.
Published: April 2005

Prey exploitation was documented for Hippoglossoides platessoides, Pleuronectes ferrugineus, and P. americanus collected from southeast Sable Island Bank in February and June 1989. Diets varied significantly by sample and with fish species and length. Of 239 species consumed by flatfishes, 66 were determined to be principal prey. Crustaceans, particularly amphipods, were the most frequently exploited prey of all three flatfish species. Small H. platessoides fed on suprabenthic fauna, while larger fish exploited epifauna and hyperiid suprafauna. P. ferrugineus exploited epibenthic fauna, consuming crustaceans and tunicates when small and polychaetes when larger. P. americanus preyed on epifauna; smaller fish exploited polychaetes while larger fish usually consumed crustaceans associated with ectoproct colonies. Feeding intensity was dramatically lower in February, food being found in stomachs of only 36% of H. platessoides and 49% of P. ferrugineus, and lacking in the stomachs of P. americanus. In June, stomachs of 86% of H. platessoides, 94% of P. ferrugineus and 96% of P. americanus contained food. Results indicate that prey resources for the three flatfish species are partitioned by specific habitat and prey type preferences.
Haematological and biochemical reference values for captive Australian snapper, Pagrus auratus
Authors: Canfield P. J. , Quartararo N. , Griffin D. L. , Tsoukalas G. N. , Cocaro S. E.
Published: April 2005

Reference values for common haematological and biochemical tests were established for 64 captive Australian snapper, Pagrus auratus (Bloch & Schneider). Fish were bled from caudal vertebral sinuses after benzocaine anaesthesia. Haematological results were extremely variable for total leucocytes and types of leucocytes. There was no correlation between leucocyte counts and teucocrit values (R2=0·37). Thrombocytes were not determined by direct cell counting due to problem of aggregation. Polychromasia was common but did not correlate with reticulocyte counts (R2=0·08). Biochemical results were extremely variable for creatine kinase and aspartate transaminase but this was considered a direct result of muscle damage during collection.
Spawning migration and redd construction of Sakhalin taimen, Hucho perryi (Salmonidae) on northern Hokkaido Island, Japan
Authors: Fukushima M.
Published: April 2005

Spatial and temporal patterns of redd construction by Sakhalin taimen, Hucho perryi, were studied in small streams on northern Hokkaido, Japan. Spawning took place in late April with close relation to discharge patterns. Observed redd size (mean ± 95% C.I.) was 145 ± 11·8 cm in length and 84 ± 5·8 cm in width. The number of egg pockets per redd was either one or two, which is fewer than that of other salmonids reported in the literature. Spawning ground distributions in 1991 and 1992 were similar to each other in terms of the distribution mean and dispersion of the redds. Unlike other salmonids Sakhalin taimen probably constructed multiple redds during one spawning season.
Testicular main ducts and spermatic ducts in some cyprinid fishes I. Morphology, fine structure and histochemistry
Authors: Lahnsteiner F. , Patzner R. A. , Weismann T.
Published: April 2005

Alburnus alburnus, Leuciscus cephalusandVimba vimbaefferent duct systems of the male gonads consist of testicular main ducts and spermatic ducts. These have similar histological, fine structural and (enzyme–) histochemical characteristics and function in (1) storage and (2) nutrition of spermatozoa, (3) synthesis of steroid glucuronides, (4) secretion of proteins and enzymes (5) formation of an ionic gradient in the seminal fluid and (6) they have auto– and heterophagocytotic activities. Therefore testicular main ducts and spermatic ducts are important in the formation of the seminal fluid.
Muscle development in Atlantic salmon (Salmo salar) embryos and the effect of temperature on muscle cellularity
Authors: Usher M. L. , Stickland N. C. , Thorpe J. E.
Published: April 2005

Salmon eggs were incubated at 5, 8 or 11° C from fertilization to hatching. At Gorodilov stages 25, 27, 29, 31 and 33 transverse sections of whole embryos (at somite level 10–15) were prepared for histochemistry and electron microscopy. At every stage up to hatching, cross–sectional areas of the embryos were not different between temperatures, and from stage 27 onwards there was also no difference in the ratio of white to red muscle. However, there were more muscle fibres but of smaller average diameter in both the red and white muscle for the colder temperature embryos. At hatching there were also more nuclei (per cross–section) in the colder embryos but more nuclei per muscle fibre in the warmer embryos. In all cases the 8° C embryos were intermediate between 5 and 11° C embryos in their muscle parameters. Fast and slow muscle fibres could only be distinguished in the embryos by alkali–stable ATPase reactions. Succinic dehydrogenase activity was low in embryonic fish. No differences between the temperature groups were detected in the histochemical reactions for either ATPase or succinic dehydrogenase activities.
Ultrasonography, a non–invasive method for sex determination in cod (Gadus morhua
Authors: Karlsen øRjan , Holm JensChristian
Published: April 2005

Ultrasonography is a fast, accurate, and non–invasive method to determine the sex of cod (Gadus morhua). In this study it was used on 788 farmed cod ranging in age from 1 to 6 yr. Accuracy of sex determination was over 95% for fish subjected to Ultrasonography from October to April.
Population biology of two helminth parasites of flatfishes from the Atlantic coast of Morocco
Authors: Belghyti D. , Berrada‐rkhami O. , Boy V. , Aguesse P. , Gabrion C.
Published: April 2005

On the Atlantic Moroccan coast, two species of pleuronectiform fish coexist, wedge sole (Citharus linguatula) a temperate species, and spotted flounder (Dicohgoglossa cuneata) a tropical one. These two species are the definitive host for Bothriocephalus andresi and Acanthocephaloïdes propinquus, respectively. A negative binomial fits the dispersion of B. andresi in the population of C. linguatula. The fish become parasitized between their first and third year, while still immature, with the highest abundances in the third year. After the fish become ichthyopagous, the level of infection drops drastically. We postulate that copepods are the sole source of infection. The presence of B. andresi in both Atlantic and Mediterranean populations of C. linguatula shows that the parasite follows the host during its migration along the Mediterranean coasts.

The prevalence of A. propinquus remains above 50% as a consequence of the large numbers of amphipods included in the diet of D. cuneata, regardless of the age of the fish or the season. The amphipods, Phtisica marina and Pariambus typicus are an important food and represent potential intermediate hosts for A. propinquus. The population dynamics of A. propinquus on the Atlantic Moroccan coasts are similar to those observed in parasite populations of Gobius niger in the Gulf of Lion (French Mediterranean). The observation of B. andresi and A. propinquus in both Moroccan Atlantic and Mediterranean fishes highlights the problem of the evolution of these parasite populations during the colonization of the Mediterranean by the hosts.
The effects of temperature acclimation on the oxygen consumption and enzyme activity of red and white muscle fibres isolated from the tropical freshwater fish Oreochromis niloticus
Authors: Mwangangi D. M. , Mutungi G.
Published: April 2005

The standard oxygen consumption rate and the activities of muscle citrate synthase, creatine phosphokinase and lactate dehydrogenase in the tropical fish Oreochromis niloticus acclimated to either 20.5 ± 0.3° C or 26.5 ± 0 ± 5 ± C for at least 3 months were investigated. The standard oxygen consumption rate of individual fish from the two acclimation temperatures was determined at 20, 25 and 30 ± C. At all experimental temperatures, the standard oxygen consumption rate of fish acclimated to 20.5 ± 0.3° C was significantly higher than that of fish kept at 26.5 ± 0.5 ± C. In both groups smaller individuals had a higher oxygen consumption rate than large ones.

Analyses of the activity levels of citrate synthase (CS), creatine phosphokinase (CPK) and lactate dehydrogenase (LDH) in both red and white muscles isolated from fish kept under the two temperature regimes were performed at 26 ± C. The activity of CS in both red and white muscles isolated from the 20.5 ± 0.3° C acclimated fish was significantly higher than that of muscles isolated from the 26.5 ± 0.5 ± C acclimation group. Similarly, the CPK activity in white muscles isolated from fish acclimated to 20.5 ± 0.3 ± C was higher than that of muscles obtained from the 26.5 ± 0.5 ± C acclimation group. However, the CPK activity in red muscles isolated from the two fish groups was not significantly different. The opposite results were obtained for LDH activity. For example, the LDH activity of white muscles isolated from fish acclimated to 26.5 ± 0.5 ± C was significantly higher than that of the same muscles but from the 20.5 ± 0.3 ± C acclimated fish. No differences were observed in the LDH activity of red muscles isolated from the two fish groups.
Annual cycles of growth and reproduction in hatchery–reared Florida largemouth bass, Micropterus salmoides floridanus, raised on forage or pelleted diets
Authors: Rosenblum P. M. , Brandt T. M. , Mayes K. B. , Hutson P.
Published: April 2005

Annual cycles of growth and reproduction of hatchery–reared Florida largemouth bass, Micropterus salmoides floridanus, were investigated. Animals were raised on either forage (goldfish, Carassius auratus) or a pelleted salmon feed. Male and female year–class 1 largemouth bass were sampled throughout one complete yearly cycle (January–December). A biphasic growth cycle was observed in both forage–fed and pellet–fed fish. No increase in body length or weight was observed until approximately midway through the spawning period (May), after which fish grew at a consistent rate for the remainder of the study. The reproductive cycle of forage–fed fish was characterized by a rapid increase in gonadosomatic index (GS1) between January and April, followed by a prolonged spawning period (April–July) during which GSI progressively declined. Fully regressed gonads were observed in September and October, and a resumption of gonadal recrudescence was observed between October and December. Visceral adipose deposits (expressed as mesenteric fat index; MFI) were resorbed during gonadal growth and the initial stages of the spawning period, and restored during the post–spawning phase. Fish raised on pelleted feed had growth and reproductive cycles that parallelled those of forage–fed fish, but several significant differences were observed between the two diet groups. During the growth phase of the cycle, pellet–fed largemouth bass grew significantly faster than forage–fed largemouth bass, and had significantly larger MFIs than forage–fed largemouth bass at all times of the year. Pellet–fed fish also had significantly larger GSIs than forage–fed fish. These data indicate that diet composition may be an important determinant of growth and reproductive function in this species.
Dinucleotide‐repeat polymorphism in DNA of rainbow trout and its application in fisheries science
Authors: Sakamoto T. , Okamoto N. , Ikeda Y. , Nakamura Y. , Sato T.
Published: April 2005

Dinucleotide–repeat DNA polymorphisms for rainbow trout, Oncorhynchus mykiss, are described. The potential applications of these markers in fisheries science are discussed.