bluuebunny/crossref_metadata_2025 huggingface dataset:
Urine of reproductively mature female rainbow trout, Oncorhynchus mykiss (Walbaum), contains a priming pheromone which enhances plasma levels of sex steroids and gonadotrophin II in males
Authors: Scott A. P. , Liley N. R. , Vermeirssen E. L. M.
Published: April 2005

Urine of reproductively mature female rainbow trout was shown to contain a priming pheromone which raised the levels of 17a,20β‐dihydroxy‐4‐pregnen‐3‐one (17,20β‐P), testosterone and gonadotrophin II in the blood plasma of reproductively mature male rainbow trout. Milt volumes, however, were unaffected.

Because it had been established in a previous study that the sulphated form of 17,20β‐P is abundant in the urine of spawning rainbow trout, synthetic 17a,20β‐dihydroxy‐4‐pregnen‐3‐one 20‐sulphate was also tested for pheromonal activity. It was found to have only a smalt and inconsistent priming effect on steroid levels and did not alter the orientation or spawning activity of males.

It was also shown that, in the majority of experiments, there was a significant drop, over the course of 24 h, in the levels of 17,20β‐P and testosterone in the control groups of males.
Primary and secondary indices of stress in the progeny of rainbow trout (Oncorhynchus mykiss) selected for high and low responsiveness to stress
Authors: Pottinger T. G. , Moran T. A. , Morgan J. A. W.
Published: April 2005

A series of pooled gamete matings was carried out employing eggs and milt from mature male and female rainbow trout selected for a consistently high‐ or low‐responsiveness to stress, as indicated by post‐stress plasma cortisol elevation. Development of the progeny was closely monitored and the responsiveness to stress of the progeny of high‐responding parents and the progeny of low‐responding parents was assessed by two methods. For a period of 14 months, at approximately monthly intervals, the plasma cortisol elevation evoked by a standardized confinement stress was determined in fish from each group, and secondly, on one occasion, the time‐course of the plasma cortisol response to a 24‐h period of confinement was monitored. Progeny of high‐responding parents snowed a significantly greater cortisol response to stress than the progeny of low‐responding parents during both testing procedures. However, when the effect of a 14‐day confinement stress was examined, high‐responding progeny showed a more rapid recovery of plasma cortisol levels, while levels in the low‐responding progeny, although initially lower, showed a more sustained elevation. To assess the possible functional implications of these observations, circulating lymphocyte numbers, an immunologically important cortisol‐sensitive component of the blood cell complement, were determined. The duration of the lymphocytopenia observed following the onset of confinement was found to be related to the initial, not the sustained, cortisol response. These data suggest that manipulation of the sensitivity to stress of fish is feasible by selective breeding, but that careful.choice of the indices employed to identify traits considered desirable is necessary.
Influence of temperature on ovarian recrudescence in the Indian catfish, Heteropneustes fossilis
Authors: Saxena P. K. , Sandhu R.
Published: April 2005

Over a 60‐day experiment during the preparatory phase of the reproductive cycle, ovarian weights increased with rise in temperature in Heteropneustes fossilis and oocyte diameters suggested an optimum temperature of 22° C for Stage II oocyte formation. The oocytes did not reach Stage II at 10° C. Atresia of Stage III oocytes occurred following 60 days of exposure at 30°C.
Intraspecific cleaning behaviour in Cyprinus carpio in aquaria
Authors: Soto C. G. , Zhang J. S. , Shi Y. H.
Published: April 2005

Intraspecific cleaning behaviour of diseased juvenile Cyprinus carpio L, in experimental tanks in Wuxi, China has been observed and is described.
Caudal eyespots on fish predators influence the inspection behaviour of Trinidadian guppies, Poecilia reticulata
Authors: Paxton C. G. M. , Magurran A. E. , Zschokke S.
Published: April 2005

The effect of the false caudal eyespots (ocelli) of fish predators on guppy inspection behaviour was tested by use of predator (Crenicichla) models with and without a caudal ocellus. When a false eyespot was present, inspecting guppies spent significantly less time near the tail compared to a control model without a tail eyespot.
Extracellular ionic and acid‐base adjustments of Atlantic salmon presmolts and smolts in fresh water and after transfer to sea water: the effects of ovine growth hormone on the acquisition of euryhalinity
Authors: Nonnotte G. , Boeuf G.
Published: April 2005

In order to better understand the basis for the acquisition of euryhalinity by juvenile salmon and the role of endogeneous stimuli, experiments have been carried out to examine the dynamics of ionic and acid‐base adjustments in fresh water (FW) and after direct transfer to full salinity (32 g l−1) sea water (SW) (1) on Atlantic salmon smolt during the natural period of smoltification in spring, (2) on presmolt salmon in autumn, after intraperitoneal implantation of pellets containing ovine growth hormone (oGH). During parr‐smolt transformation in FW, gill Na+/K+ ATPase activity gradually rises, the plasma osmolality (Posm) is unaffected and the total CO2 of the plasma decreases significantly while whole blood pH fluctuates slightly. Direct transfer of smolt from FW to SW provokes only a slight increase in Posm and emphasizes the acid‐base balance disruptions shown in FW. An oGHimplant in a presmolt stimulates gill Na+/K+ ATPase activity in FW, and affects the acid‐base balance. After SW transfer (12 days after implantation), oGH treatment prevents the increase of osmotic pressure and the restoration of the acid‐base, ionic equilibrium was faster for oGH‐implanted fish than for sham‐operated fish. These observations show that in FW smelting salmon develop most of the systems they need for migration and growth in SW and that oGH implants induce the development of physiological characteristics of smolts in a non‐natural period of smolting.
Estimates of gene flow among neighbouring populations of brown trout
Authors: Morán P. , Pendas A. M. , García‐Vázquez E. , Izquierdo J. I. , Lobón‐Cervlá J.
Published: April 2005

Between‐population gene flow was estimated in neighbouring freshwater and anadromous Salmo trutta populations from Asturias, Northern Spain. Populations from the same drainage showed a high mean level of gene flow. Gene flow was also found between populations from different drainages and was negatively related to the distance between river mouths. The strength of the homing orientation of migratory individuals (sea trout) is discussed.
Structures and movements of the buccal and pharyngeal jaws in relation to feeding in Diplodus sargus
Authors: Vandewalle P. , Saintin P. , Chardon M.
Published: April 2005

The present paper studies the possibly different feeding strategies of Diplodus sargus to crustaceans, molluscs, worms, and small fish. The buccal jaws are built strongly and bound together by numerous ligaments. The dentition is heterodont: incisors in front and molars in the middle and hind parts. The principal originality of the musculature of this species is the forward insertion of the adductores mandibulae. These are very thick and insert on both the upper and lower jaws, so that contraction of any individual muscle acts on the buccal pieces as a whole, which thus constitute a remarkable crushing device. The pharyngeal jaws are frail as in primitive perciforms: the lower ones are well separated, being bound only anteriorly, while the upper ones consist of the second and third pharyngobranchials and a posterior toothed plate. When feeding on crabs, Diplodus sargus always sucks in the prey and seizes it with the buccal jaws. Mouth opening is accompanied by extensive protrusion of the mouth, with or without neurocranial elevation. Mouth sucking and seizing movements vary little. Once seized, the prey is usually moved to the molars and crushed. The crushing movements may be fast and ample or slow. In the latter case, deformation of the prey is observable. Crushing usually results in the crab being broken into pieces. The pharyngeal jaws grip one part of the prey and shift it to the oesophagus, then seize the second part. Diplodus sargus adapts its feeding behaviour to the type of prey. A snail, for instance, is crushed by the buccal or pharyngeal teeth, the pieces of shell are ejected, and the soft parts conveyed with difficulty to the oesophagus by the pharyngeal jaws. A fish on the other hand, is sucked tail first into the mouth cavity and quickly shifted to the digestive tract by the pharyngeal bones. Behaviour toward different prey differs by the presence or absence of parts of the sequence of feeding movements (for example crushing) or by the fact that certain movements or parts of the sequence are repeated. The variability of any movement in the sequence is the same whatever the sort of prey. Crushing occurs between the buccal incisors and molars and was observed twice between the pharyngeal teeth. Usually, it seems, the latter are involved in transport only. In transport, the left and right pharyngeal jaws may perform different functions: their movements, unlike the symmetrical movements of the buccal jaws, sometimes differ.
The impact of intra‐ and interspecific interactions on young‐of‐the‐year brook charr, in temperate lakes
Authors: Venne H. , Magnan P.
Published: April 2005

The abundance, growth, spatial distribution, and feeding habits of five allopatric brook charr, Salvelinus fontinalis, populations (young‐of‐the‐year, 0+ juveniles; YOY) were compared with five other populations living sympatrically with white sucker, Catostomus commersoni. The study was made in oligotrophic lakes of the Laurentian Shield (Québec, Canada) during three sampling periods in 1989 (July, August and September). The abundance of YOY charr was significantly higher in allopatric than in sympatric populations (45·3 ± 3·8 vs 3·4 ± 3·8 fish/lake caught in 1773 m2 of gillnets; P<0·005). The mean length of YOY charr did not differ among allopatric and sympatric populations at each sampling period; July: 60·2 ± 3·0 vs 60·0 ± 4·5 mm; August: 61·9 ± 4·5 vs 63·2 ± 4·1 mm; September: 77·9 ± 8·7 vs 77·3 ± 7·8 mm respectively. Horizontal distribution of allopatric YOY charr did not differ from that of sympatric charr, 65% of the fish being captured within the first 2 m depth and the rest between 2 and 7 m depth. In contrast, the vertical distribution of allopatric YOY charr from both communities was significantly different; 81% of allopatric charr were captured within 0·5 m from the substrate compared to 64% for sympatric charr (P<0·001). Differences in vertical distribution of the fish were related to differences in diet; allopatric charr fed mainly on benthic and large planktonic organisms whereas sympatric charr fed less on these organisms and more on terrestrial organisms. In the lake where YOY charr were most abundant, individuals were spatially segregated into two groups; one ‘littoral’, found in 0–2m depth, and one ‘profundal’, found in 3–6 m depth. Growth, condition, and feeding habits of charr from the two groups were different, especially during the last sampling period.
Life history strategies of four small‐size fishes in the Suez Canal, Egypt
Authors: Fouda M. M.
Published: April 2005

Of 35 species collected from the shores of the Suez Canal and its lakes, five were abundant year round. Sihouettea aegyptia and Aphanius dispar are of Red Sea (warm water) origin, whereas Pomatoschistus marmoratus, Aphanius fasciatus and Atherina boyeri are Mediterranean species. S. aegyptia and A. dispar are distributed throughout the Suez system whereas A. fasciatus is restricted to the northern canal. P. marmoratus and A. boyeri have not spread southward beyond the Bitter Lakes. Salinity is the main limiting factor for the distribution of Mediterranean species. S. aegyptia and A. dispar are dominant in the Bitter Lakes (salinity 44‰), whereas P. marmoratus and A. boyeri are abundant in Timsah Lake (salinity 7·8–41·6‰). There was considerable interannual and monthly variation in the relative abundance of each species. The populations were dominated by a single age group, and life spans were no more than 2 years. Rapid growth was evident during the first spring in P. marmoratus and A. boyeri and during the first summer, early autumn in S. aegyptia and A. dispar. The relative abundance of each food item in the diet varied with fish size and season. S. aegyptia, P. marmoratus and A. dispar fed mostly on harpacticoid copepods, polychaetes, demersal eggs, diatoms and blue‐green algae whereas A. boyeri fed mostly on planktonic copepods. The warm water species are summer spawners, whereas the temperate species are autumn‐winter spawners.
The trout (Salmo trutta) population of the Afon Cwm, a small tributary of the Afon Dyfi, mid‐Wales
Authors: Crisp D. T. , Beaumont W. R. C.
Published: April 2005

Data are presented from a 10‐year (1984 to 1993) study of a Salmo trutta population in the Afon Cwm, a small tributary of the Afon Dyfi, mid‐Wales. The stream is a spawning and nursery area for sea trout. Growth of trout within the stream can be summarized by a von Bertalanffy growth coefficient (K) of 0·310, with asymptotic length (1∞) 21·6 cm and with length at age 1 of 7·6 cm. Mean population density in the whole stream varied from year to year between 0·05 and 0·60 0‐group trout m−2 and between 0·05 and 0·70 older trout m−2. Mean biomass varied, between years, from 0·1 to 3·5 g m−2 for 0‐group and from 1·3 to 10·4g m−2 for older trout. Loss between 3 and 5 months of age appeared to be proportionate at about 50 to 60% and instantaneous loss rate from 5 to 53 months of age varied from 0·04 to 0·10 month−1 and was positively correlated with cohort number at 3 months of age. Production between 3 and 53 months of age varied between cohorts from 3 to 8 g m −2 live weight.
Stimulation of the renin‐angiotensin system and drinking by papaverine in the seawater eel, Anguilla anguilla
Authors: Tierney M. L. , Cramb G. , Hazon N.
Published: April 2005

The administration of papaverine (a hypotensive agent) caused an elevation in plasma angiotensin II concentration in the seawater eel, with a corresponding increase in drinking rate. Captopril completely abolished papaverine‐induced increase in drinking and reduced papaverine‐stimulated plasma angiotensin II concentrations by over 80%.
Cyalume tagging: a new method for tracking reef fishes at night
Authors: Burke Nancy C. , Winn Howard E.
Published: April 2005

A new method for tracking nocturnal reef fishes using a Cyalume light stick is described. The Cyalume is attached to the dorsal musculature using dissolvable sutures. The tagged fish can then be monitored throughout the night. Potential uses and problems are discussed. Key words: tagging; nocturnal fishes; tracking; Cyalumes.
Fish host range of seven isolates of Cryptocaryon irritans (Ciliophora)
Authors: Burgess P. J. , Matthews R. A.
Published: April 2005

Host specificity of the marine ciliate Cryptocaryon irritans was investigated using seven parasite isolates and six experimental fish species. The low degree of host specificity of C. irritans to teleost fish has been confirmed. Furthermore, five fish species occurring outside the geographical range of this parasite were also susceptible to infection; three of these could be at risk to Cryptocaryon through aquaculture practices.
Light and electron microscopic observations on the route of the triactinomyxon‐sporoplasm of Myxobolus cerebralis from epidermis into rainbow trout cartilage
Authors: EL–Matbouli M. , Hoffmann R. W. , Mandok C.
Published: April 2005

Penetration of triactinomyxon–sporoplasms of Myxobolus cerebralis through skin, fins, gills and buccal cavity have been demonstrated experimentally in rainbow trout. Furthermore the multiplication–stages of penetrated triactinomyxon–sporoplasms reach the cartilage via peripheral nerves and the central nervous system (CNS). This is in contrast to the assumption that the agent reaches the cartilage via blood, lymph, and/or coelomic fluid. During the first hour following penetration, the sporoplasm migrates between the epidermal cells. Then, it enters the epithelia and multiplies intracellularly. These stages migrate deeper into the subcutis, then through the peripheral nerves and CNS. After about 21 days the parasites reach the head cartilages. During their migration they also multiply to increase parasite numbers. The ultrastructure of the proliferative phase (presporogonic development) and the sporogonic phase of the life cycle are demonstrated and discussed.
Peculiarities of the male urogenital apparatus of two grunt species (Teleostei, Haemulidae)
Authors: Rasotto M. B. , Sadovy Y.
Published: April 2005

An unusual testicular structure in the white grunt, Haemulon plumieri, and the French grunt, H. flavolineatum, and a urinary exocrine gland in H. flavolineatum are described. The testes of both species are comprised predominantly of efferent ducts, with spermatogenetic tissue restricted to the gonadal periphery. The epithelial cells of the efferent ducts produce glycogen which may serve a role in the storage and nutrition of sperm. The urinary gland is a male accessory gland thought to be associated with reproduction. The gland is mesonephric in origin and the epithelial cells of the gland produce mucins which may be involved in intraspecific chemical communication.
The influence of incubation salinity on the buoyancy of red drum eggs and yolk sac larvae
Authors: Ponwith B. J. , Neill W. H.
Published: April 2005

Fertilized eggs of red drum were harvested from a hatchery spawning tank at 28 ppt salinity in one trial and 32 ppt salinity in another. Eggs were apportioned among incubation chambers maintained at four salinities—a control at the spawning salinity, and three treatments: (1) the salinity at which the eggs were neutrally buoyant, this being 21 and 23 ppt for trials one and two, respectively; (2) 17 ppt; and (3) 25 ppt. For each treatment, the neutral‐buoyancy salinity for the eggs and developing larvae was measured over time and compared with that of the control. Values for none of the treatments differed significantly from the control in the first trial, but the 17 and 23 ppt treatments yielded values significantly different from the control in the second trial. Neutral buoyancy for each set of control eggs also varied significantly over time. The differences between the treatments and the control and between the two controls were most pronounced after the eggs hatched.
Mitochondrial DNA differentiation between two sympatric morphs of striped jack near Japan
Authors: Masuda R. , Kamaishi T. , Kobayashi T. , Tsukamoto K. , Numachi K.
Published: April 2005

Two sympatric morphs (type A with a vertebral number of 25 and type B with a vertebral number of 24) of striped jack Pseudocaranx dentex (Bloch & Schneider) were analysed genetically. A part of the 16S–rRNA region of mtDNA was amplified with polymerase chain reaction for 24 specimens, and a restriction enzyme fragment polymorphism showed significant differences between the two types. While all specimens sampled in Ogasawara were identified as type B, about 90% of striped jack in Oita were type A and 10% were type B. Although the spawning areas of these two types are still unknown, significant genetic differences between the two sympatric morphs show that recruitment and migration patterns might differ from each other. The current system suggests the possibility that the juveniles of type B in Oita may migrate from the Ogasawara Islands.
Life history and population dynamics of the western mosquitofish: a comparison of natural and introduced populations
Authors: Haynes J. L. , Cashner R. C.
Published: April 2005

Life history and population dynamic patterns of Gambusia affinis in southeastern Louisiana varied spatially and temporally in 1990 and 1991, but were consistent with previous reports of this species in the southern regions of its natural range. Several differences exist among populations in different geographic regions within the United States, as reported in the literature, which do not follow a‘ native v. introduced’ dichotomy: (1) brood size decreases and offspring size increases from north to south; (2) large overwintered females in northern areas produce more broods within a season than those in southern populations, while the reverse is true for young‐of–year females; (3) minimum size at first reproduction follows a seasonal pattern within populations, but tends to be smaller in southern and larger in northern and Hawaiian populations; (4) synchronous reproduction early in the season is characteristic of northern populations, but does not occur in southern areas; and (5) mosquitofish reproduce year–round in Hawaii, while 'southern’ populations within the continental U.S. cease reproduction during winter.
The effects of the cyanobacterium Microcystis aeruginosa, the cyanobacterial hepatotoxin microcystin–LR, and ammonia on growth rate and ionic regulation of brown trout
Authors: Bury N. R. , Eddy F. B. , Codd G. A.
Published: April 2005

Brown trout were exposed for 63 days to five treatments: a control; the purified cyanobacterial hepatotoxin microcystin—LR (MC—LR) (41—57 μg MC—LR 1−1); lysed toxic Microcystis aeruginosa cells (41–68 μg MC—LR 1−1 and 288 μg chlorophyll a 1−1); lysed non—toxic M. aeruginosa cells (non—MC—LR containing and 288 μg chlorophyll a 1−1); ammonia (65–325 μg NH3 1−1). All treatments produced significantly reduced growth compared to controls (P<0·05, Fisher test). Exposure to ammonia resulted weight loss over the first 7 days followed by weight increase, though at a significantly lower level than in the other treatments. First exposed to lysed toxic M. aeruginosa cells grew less than those exposed to lysed non—toxic cyanobacteria or purified MC—LR. Sodium influx rates after 63 days exposure to purified MC—LR, lysed toxic M. aeruginosa cells, or ammonia showed a significant increase compared to control fish or those exposed to lysed non—toxic M. aeruginosa cells. There were no significant differences in Na+ efflux or net Na+ uptake rates between treatments. Significant increases in body Na+ and Cl— were seen in fish exposed to lysed toxic M. aeruginosa cells or ammonia. Only fish exposed to ammonia showed a significant increase in body ammonia. Short—term exposure, over 4 h, to lysed toxic cells, non—toxic cells or purified MC—LR resulted in insignificant changes in Na+ flux rates compared to controls although there was a significant net Na+ loss in fish exposed to ammonia. Chronic exposure of fish to toxic cyanobacterial blooms may result in ionic imbalance and reduced growth.
Changes in some endocrinological and non‐specific immunological parameters during seawater exposure in the brown trout
Authors: Marc A. M. , Quentel C. , Severe A. , Le Bail P. Y. , Boeuf G.
Published: April 2005

The influence of autumnal progressive and direct seawater transfers on ionic parameters, plasma growth hormone (GH) and thyroid hormones (TH) and also on the non–specific immune traits phagocytic activity, lysozyme and non–specific cytotoxicity were examined in 45–55 g brown trout (Salmo trutta). In both experiments, the seawater transfer induced the same pattern of endogeneous modifications but they were more pronounced and more lasting after the direct seawater transfer than after the progressive one. In seawater–transferred trout, there was a significant transitory increase of the plasma osmolarity, chloride concentration, GH levels and a transient decrease of the TH. The phagocytic activity of the pronephric leucocytes and the lysozyme concentrations were significantly higher in seawater–transferred trout than in controls. Nevertheless, the non–specific cytotoxicity should not be modified after the seawater exposure. Moreover significant positive correlations were observed between plasma GH and chemiluminescence or lysozyme increases. These data support the hypothesis that GH is involved in the salmonids’ non–specific immune potential, especially by stimulating the macrophage functions.
First report on egg deposition and egg morphology of the endangered endemic Romanian perch
Authors: Riehl R. , Bless R.
Published: April 2005

The surface of the whitish translucent egg of Romanichthys valsanicola is sculptured in an irregular honeycomb–like pattern. The micropyle consists only of a type I micropylar channel.
In vitro differentiation of myoblasts from skeletal muscle of rainbow trout
Authors: Greenlee A. R. , Dodson M. V. , Yablonka‐Reuveni Z. , Kersten C. A. , Cloud J. G.
Published: April 2005

Substrata, plating densities and tissue culture media were compared for their effects on the proliferation and differentiation of myoblasts from skeletal muscle of rainbow trout. Mononuclear cells were isolated from the lateralis muscle of 4–11‐month‐old trout and plated on to glass coverslips coated with fibronectin, laminin or Matrigel. Cell proliferation was estimated by determining the density of nuclei on successive days in culture, and myoblast differentiation was detected by immunostaining cultures with the myosin‐specific monoclonal antibody MF20. Mononuclear cell proliferation was highest for cells cultured on fibronectin or laminin and lowest for cells cultured on Matrigel, but the total number of nuclei in myosin‐positive cells did not differ between substrata. The percentage of nuclei in myosin‐positive myocytes and myotubes was significantly higher for cells cultured on Matrigel. The proportion of cells adhering to Matrigel and undergoing differentiation increased with plating density. Of three media tested, Dulbecco's Modified Eagle Medium (DMEM), RPMI 1640 (RPMI), Leibovitz's L‐15 (L‐15) supplemented with 1 or 10% fetal bovine serum (FBS), a significantly greater proportion of the myoblasts differentiated when cells were cultured in L‐15+ 10% FBS. These results suggest that culturing trout muscle‐derived cells on a substratum of Matrigel at a high density and maintaining cells in L‐15+ 10% FBS provide the conditions that maximize the proportion of cells that actively synthesize muscle myosin and facilitate trout myoblast differentiation in vitro.
Genetic variation in immune parameters and associations to survival in Atlantic salmon
Authors: Lund T. , Gjedrem T. , Bentsen H. B. , Eide D. M. , Larsen H. J. S. , Røed K. H.
Published: April 2005

Lysozyme activity, haemolytic activity, total level of IgM, and levels of antibodies against A‐layer from Aeromonas salmonicida and O‐antigen from Vibrio salmonicida, respectively, were determined in 77 full‐sib groups of Atlantic salmon in order to evaluate their possible use as immune parameters for indirect selection to improve disease resistance. Fish from parallel full‐sib groups had previously been challenged with Aeromonas salmonicida (causing furunculosis), Renibacterium salmoninarum (causing bacterial kidney disease, BKD) and Vibrio salmonicida (causing cold‐water vibriosis). Heritabilities were estimated for each of the immune parameters and correlations between the least square means of the full‐sib groups for the different immune parameters and survival rates in the parallel full‐sib groups were determined. A significant genetic variation in lysozyme activity was found, as well as an apparent genetic association between low lysozyme activity and high survival rates. Low heritabilities and low univariate correlations with survival in the full‐sib groups were estimated for all of the other immune parameters. An analysis of the multivariate associations between the full‐sib mean values of the complete set of immune parameters, and survival rates in the parallel full‐sib groups in each of the challenge tests, revealed that, at low levels of lysozyme activity and with low antibody titres against V. salmonicida O‐antigen, increased IgM levels seemed to increase survival from furunculosis.
Foraging success of largemouth bass at different light intensities: implications for time and depth of feeding
Authors: McMahon T. E. , Holanov S. H.
Published: April 2005

Laboratory feeding trials were conducted to determine how light intensity affects foraging success by the visual piscivore, the largemouth bass (Micropterus salmoides). Foraging success was greater than 95% at light levels ranging from low intensity daylight (2.43 × 102 lx) to moonlight (3 × 10−3 lx), but declined significantly to 62% at starlight (2 × 10−4 lx) and near 0% in total darkness. Over a range of low to high water clarities (0.5, 2.0, and 4.0 m Secchi depth), estimated depth limits for feeding during the day ranged between 5.5 to 44 m and from 1.6 to 13 m at night during a full moon. At starlight, light intensity rapidly attenuated to a level below the feeding threshold within 0.5 m of the surface at all water clarities. The depth of the water column available for feeding in low clarity water (0.5 m Secchi) was 67 and 75% less than at moderate (2.0 m Secchi) and high (4.0 m Secchi) water clarities. The findings illustrate how differences in the light environment can have important ramifications for predator‐prey interactions.
Reactions of dace to linear accelerations
Authors: Pavlov D. S. , Tjurjukov S. N.
Published: April 2005

It is demonstrated that the rheophilic fish dace (Leuciscus leuciscus) is able to detect the direction of its movements in a water flow by perceiving and analysing positive and negative accelerations from 15 up to 50 cm s−2, by the use of labyrinth organs. Tests were conducted on fish with ‘switched off’ mechanoreceptors and labyrinth organs, under conditions which eliminated the use of visual orientation. It was also demonstrated that the values of linear accelerations which stimulated dace compensatory movements against water currents were comparable with the values of accelerations which could arise in river flows as a result of pulsation in current velocity. The results support the hypothesis that rheophilic fish are able to use inertial stimuli for their spatial orientation.
The influence of prey biomass on activity and consumption rates of brook trout
Authors: Sirois P. , Boisclair D.
Published: April 2005

The objectives of this work were (1) to assess the influence of zooplankton biomass on activity and consumption rates of young‐of‐the‐year brook trout (Salvelinus fontinalis) and (2) to validate an in situ enclosure approach to quantify energy allocation patterns in fish. These objectives were attained by directly estimating fish growth, consumption and activity rates on 10 occasions characterized by different levels of zooplankton biomass (0.005 to 0.100 mg dry weight 1−1). One enclosure was used to estimate growth and activity rates and five additional enclosures were used to estimate consumption rates. Among‐experiment variations of activity rates (sum for five trout = 2.4 to 33.5 calories day−1) were proportionally more important than variations of consumption rates (sum for five trout = 59.5 to 112.7 calories day−1). The results support the existence of a significant positive relationship between fish activity rates and zooplankton biomass. No significant relationship was found between consumption rates and prey biomass. Final size of fish inside the enclosure was within 7.6% of the value estimated using experimentally derived activity and consumption rates. This situation, together with the stability of among‐enclosure activity and feeding schedules, suggested that the experimental design was appropriate to estimate fish energy allocation patterns. Combination of our observations with those of a previously published work indicated that small variations of fish size or zooplankton biomass can cause a two‐fold variation of fish activity costs.
Seasonal activities of Barbus barbus: effect of temperature on time‐budgeting
Authors: Baras E.
Published: April 2005

Surgically implanted activity‐circuit radio transmitters (40 MHz) were used to study the seasonal activities of 21 adult (males: 23 to 35 cm f.l. and females 38 to 55 cm f.l.) Barbus barbus (Pisces, Cyprinidae) in the River Ourthe (Southern Belgium) in 1989–1991. During the autumnal thermal transition (water temperature 9 to 10° C), the typical dusk and dawn pattern observed in summer turned to a trimodal pattern with the emergence of a diurnal phase. The auroral then crepuscular and finally diurnal activity periods progressively vanished as water temperature decreased down to the thermal limit for activity (4.0° C), when barbel entered a dormancy period. An opposite progressive shift was observed during the spring thermal transition. Daily activity budgets ranged from 0 to 720 min—on the annual cycle and were significantly (r2=0.686, P<0.05, d.f. = 36) dependent on water temperature and on morphodynamic unit size, while fish size was non‐significant. Although the dusk and dawn rhythm pattern was consistent throughout summer, water temperature significantly (P<0.05) interfered with the respective duration of crepuscular and auroral activities (r2=0.586, d.f. = 57 and r2=0.692, d.f. = 55). The precise timing of activities was also thermal‐related and the activities of small male barbel were proportionally more nocturnal than those of large female barbel (ANCOVA, F=80.61, d.f. = 31 and F=4.s5, d.f. = 23, at dusk and dawn respectively), possibly due to predation pressure on small fish. It is concluded that the seasonal variations of activity budgets, rhythm patterns and timings in B. barbus correspond to a form of time‐budgeting partly to achieve thermal homeostasis in a variable environment.
A direct estimate of gillnet selectivity for brown trout
Authors: Jensen J. W.
Published: April 2005

Five hundred pre‐measured brown trout (Salmo trutta), 20 of each cm‐class from 5 to 29 inclusive, were released. They were recaptured with gillnets of mesh size 8.0, 10.5, 16.0, 19.5 and 24.0 mm, measured between adjacent knots. The nets were made of clear, nylon monofilament. The modal lengths and the general shape of the selectivity curves were in agreement with earlier findings. The height of the selectivity curve (S) increased exponentially with mesh size in mm (M): S= 0.047e0.075M.
Evaluating catches of salmonids taken by gillnets
Authors: Jensen J. W.
Published: April 2005

Data from 10 185 gillnetted brown trout (Salmo trutta L.) and 5777 Arctic charr [Salvelinus alpinus (L.)] were analysed. Relative to mesh size, the most efficiently caught fish length (the modal length) was somewhat larger with floated nets than with smaller nets placed on the bottom. There were no such consistent differences between the two species. Fish that exceeded the modal lengths were caught more efficiently than smaller fish. The relationship of most efficient mesh size to fish length and condition factor fitted excellently to a linear equation. Based on this equation, the selectivity curve for Arctic charr gillnetted in the Nesjø reservoir, the different efficiency of nets of 0.1 and 0.17mm twine and an equation expressing the increasing height of the selectivity curve with increasing mesh size, a model is presented to compare length frequencies and total numbers of gillnet catches taken with any combination of mesh sizes.
The effects of temperature, river flow, and tidal cycles on the onset of glass eel and elver migration into fresh water in the American eel
Authors: Martin M. H.
Published: April 2005

Anguilla rostrata elvers were collected in the Annaquatucket R., Rhode Island, and their otoliths extracted. Daily increments beyond the check mark formed upon entry into fresh water were counted and the date of freshwater entry was estimated. The effects of river temperature, difference between seawater and freshwater temperature, river flow and tidal stage on the number of elvers arriving on each date were estimated for six collection dates. At the earliest collection date (23 March), increasing river temperatures and reduced flow increased elver migration. At later dates (16 May‐12 June), tidal stage was the most important factor in determining the magnitude of elver migration.
Learning ability of triploid brook trout
Authors: Deeley M. A. , Benfey T. J.
Published: April 2005

Triploid brook trout (Salvelinus fontinalis) did not differ from diploids in their initial directional preference within a Y‐maze, electrical shock response threshold, or learning ability.
A light‐reflectance meter to quantify silvering during smolting in Atlantic salmon
Authors: Duston J.
Published: April 2005

An easy‐to‐construct apparatus is described to quantify changes in silvering during smolting. A modulated visible‐red light emitter/receiver unit converts light reflected from the flank of the fish into a DC voltage, the voltage being proportional to the intensity of the reflected light.
Thermal related variations of seasonal and daily spawning periodicity in Barbus barbus
Authors: Baras E.
Published: April 2005

In 1993, nocturnal spawning activities were observed in the diurnal spawning cyprinid Barbus barbus. This behaviour is interpreted as a response to exceptionally high daily thermal amplitudes, regarded as the sign of an unpredictable environment.
Scavenging on discarded saury by demersal fishes off Sendai Bay, northern Japan
Authors: Yamamura O.
Published: April 2005

Pacific saury Cololabis saira were found in 24 out of 1314 stomachs of demersal fishes collected by bottom trawling at 245–393 m depths. The same area was occupied by the stick‐held dipnet fishery for saury, in which a landing limitation was enforced to avoid overfishing. The fish species containing saury were: Pacific cod Gadus macrocephalus, walleye pollock Theragra chalcogramma, and oilfish Ruvettus pretiosus. These demersal species would not encounter living saury naturally, which normally are distributed above thermoclines. The ingested saury were smaller than market size which suggests that the saury from fish stomachs were discarded by fishermen because of small sizes to maximize profits under the landing limitation.

The scavenged saury made up 41.5, 24.6 and 77.7% of the diets of large‐sized (>30cm)Pacific cod, walleye pollock and oilfish, respectively in terms of DW composition. The extent to which discarded saury contributed to the total diet in the demersal fish assemblage, calculated by considering species composition and diets of bottom fishes, was 21.8% of the total diet. The discarded saury seemed to compensate the less productive feeding environment during autumn for the bottom fishes.
Corticosteroid and thyroid responses of larval and juvenile turbot exposed to the water‐soluble fraction of crude oil
Authors: Stephens S. M. , Alkindi A. Y. A. , Waring C. P. , Brown J. A.
Published: April 2005

Turbot larvae (24–590 degree C days; 2–32 days post‐hatch) and juveniles (1345 degree C days; 98 days post‐hatch), were exposed for 6 h to 25, 33 and 50% water‐soluble fraction (WSF) of crude oil in either static or flow‐through test systems. Larvae showed generalized primary endocrine responses, identified by elevated whole body cortisol content from as early as 2 days post‐hatch. In older larvae and juveniles, the response was related to the WSF concentration. This dose‐response relationship was not apparent in younger and yolk‐sac larvae. Whole body thyroxine content of turbot larvae exposed to the WSF of crude oil was increased, but triiodothyronine content remained stable. Aromatic hydrocarbon concentrations [benzene, toluene, ethylbenzene and xylene (BTEX) and naphthalenes] remained constant during flow‐through tests, but 65% of the initial level of BTEX hydrocarbons and 40% of the naphthalenes were lost during static exposures. Larval mortalities increased with exposure to an increasing concentration of crude oil WSF. Larval activity was significantly reduced even at the lowest WSF concentration.
Minnow predation on vendace larvae: intersection of alternative prey phenologies and size‐based vulnerability
Authors: Huusko A. , Sutela T.
Published: April 2005

Time‐intensive sampling was used to study minnow Phoxinus phoxinus density and foraging activity in the littoral area of Lake Lentua at a time of high vendace Coregonus albula larval abundance. Minnow activity and foraging during the late spring‐early summer period at low temperatures was found to be mainly nocturnal and quite consistent with features reported in the literature, with the exception of feeding on vendace larvae. The absence of the latter finding from previous studies may be due to previous seasonally limited daytime samplings. The temporal or spatial scale of sampling is decisive when studying foraging on food animals with a brief period of vulnerability and seasonal phenology. However, minnows in Lake Lentua seemed to prefer Bosmina longispina whenever available and low B. longispina density during the first weeks after the break‐up of ice directed minnow predation towards the vendace larvae. Estimated gross predation values showed that the minnow has the potential to become a remarkable predator on fish larvae. Slight variations in the vernal timing of the vendace hatching and larval development with respect to minnow activity, both of which are obviously temperature related, may be critical to vendace larval survival in the nearshore zone. However, the predation on the larvae is probably a strong factor only for a short period and the survival of the vendace larvae may be more related to the availability of suitably sized food resources than to predation by the minnow.
Histochemical, enzyme histochemical and ultrastructural investigation on the sperm‐duct glands of Padogobius martensi (Pisces, Gobiidae)
Authors: Cinquetti R.
Published: April 2005

The functions of the sperm‐duct glands of Padogobius martensi were investigated by histochemical, enzyme histochemical and fine structural methods during the prereproductive and reproductive periods, i.e. during their maximum activity. The epithelium lining the spermduct gland tubules produces strongly acidic sulphomucins, probably conjugated with proteins and the variety of sulphomucins increases during the reproductive period when the exocrine epithelium is also involved in the phagocytosis of degenerating sperm cells. A contractile network of myoid cells surround the tubules. The gland interstitium contains cells similar in enzyme histochemical and ultrastructural features to the testicular interstitial cells (Leydig cell homologues). Unlike the latter, however, the interstitial cells of the sperm‐duct gland are able to produce steroid glucuronides, which act possibly as pheromones.
Microhabitat use by 0+ and older fishes in a small English chalk stream
Authors: Watkins M. S. , Doherty S. , Copp G. H.
Published: April 2005

The microhabitat use of two size/age classes of fish (0 +, ≥1+) in the River Lee, based on measurements of 14 environmental variables, was studied using point abundance sampling by electrofishing over the summer and autumn of 1995. Microhabitat use by all cyprinid species (barbel Barbus barbus, minnow Phoxinus phoxinus, chub Leuciscus cephalus and gudgeon Gobio gobio) differed between 0+ and older (≥1+) with lentic, shallow, littoral environments being important for 0+ fishes, whereas deeper, faster areas in mid‐channel were important for ≥ 1 + fishes. There was more overlap in microhabitat use by 0+ juvenile cyprinids in the River Lee than in larger systems such as the River Danube (Slovakia/Hungary) and River Great Ouse (U.K.).
Histology of dart tag insertion sites in the epaulette shark
Authors: Heupel M. R. , Bennett M. B.
Published: April 2005

Samples of dermal and epidermal tissues of epaulette sharks Hemiscyllium ocellatum were examined histologically to assess damage caused by tagging. Tissues from around tag sites were removed at time intervals ranging from 100 min to 284 days post‐tagging. These samples showed acute and chronic responses to tagging. Acute responses consisted of localized tissue breakdown and haemorrhaging, and occurred within the first few hours after tag insertion. At 10 h post‐tagging, an intermediate response was apparent. This phase was characterized by further haemorrhaging and red and white blood cell movement into the wound area. The chronic response observed in the 10–284‐day post‐tagging samples was characterized by fibrous tissue formation to sequester the tag. This tissue presumably protects the adjacent musculature from further trauma produced by movement of the tag and provides a continuous barrier between the internal and external milieu. Tissue repair appeared to progress consistently in all specimens and no secondary infections at the tag site were seen. Tagging produced only localized tissue disruption and did not appear to be detrimental to the long term health of individual sharks. Our findings show that spaghetti style dart tagging is an acceptable method for marking individuals (40–75+ cm total length) of this species.
Divalent cations enhance ammonia excretion in Lahontan cutthroat trout in highly alkaline water
Authors: Iwama G. K. , McGeer J. C. , Wright P. A. , Wilkie M. P. , Wood C. M.
Published: April 2005

The Lahontan cutthroat trout lives under highly alkaline and saline conditions in Pyramid Lake, Nevada (pH 9.4; 0.2 mmol 1−1 Ca++; 7.3 mmol 1−1 Mg++). These experiments were conducted to study the possible roles of water Ca++ and Mg++ concentrations on ammonia excretion in the Lahontan cutthroat trout under highly alkaline conditions. The basic protocol of the experiments was to determine ammonia excretion rates during the following three exposure periods (each of 3‐h duration) in sequence: (a) in normal lake water; (b) in soft lake water with the divalent cation concentrations reduced; and (c) in the soft lake water with either Ca++ or Mg++ (or no divalent cations added) added back at the appropriate lake water concentration. The soft‐water exposure caused a significant reduction in ammonia excretion to about half of the control (original lake water) levels. When either Ca++ or Mg++ was added to the soft water in the third exposure period, the ammonia excretion rates were increased more than twofold back to lake water levels.
Spectral sensitivity of the weakly discharging electric fish Gnathonemus petersi using its electric organ discharges as the response measure
Authors: Ciali S. , Gordon J. , Moller P.
Published: April 2005

The spectral sensitivity of the weakly electric mormyrid fish Gnathonemus petersi was investigated under dark‐ and light‐adapted conditions using a transient change (startle) in its electric organ discharge (EOD) rate as response measure. The startle was resistant to habituation and graded with light intensity. Under both lighting conditions, the fish responded optimally to a monochromatic light of 525 nm. A porphyropsin pigment (520–5402) appears to mediate spectral sensitivity over most of the visible spectrum. However, G. petersi responded more strongly to 625‐ and 675‐nm lights (dark‐ and light‐adapted fish) and a 725‐nm light (light‐adapted fish only) than predicted by the presence of a single rod pigment. These data suggest that at least one additional visual pigment (most likely of cone cells) maximally absorbing long wavelength light (600 nm or longer) is present. The spectral sensitivity data are consistent with the sensitivity hypothesis in that heightened sensitivity to long wavelength light is predicted for fish living in blackwater habitats which are characterized typically by low light levels and transmission of predominantly long wavelengths. Histology of the retina showed photoreceptors grouped into bundles and ensheathed by pigment epithelial cells. Our results demonstrated a functional visual sense in a species of fish much better known and studied for its electrosensory and electromotor abilities.