bluuebunny/crossref_metadata_2025 huggingface dataset:
Changes in the feeding biology of the Nile perch, Lates niloticus (L.) (Pisces: Centropomidae), in Lake Victoria, East Africa since its introduction in 1960, and its impact on the native fish community of the Nyanza Gulf
Authors: Hughes N. F.
Published: January 2006

Lates niloticus is not native to Lake Victoria but was introduced during or shortly before 1960. It remained relatively uncommon until 1975, when the number in the Nyanza Gulf began to increase impressively, the estimated catch rising over 100‐fold between 1978 and 1982. Originally Lates was piscivorous, its diet reflecting the composition of the native fish community. The present investigation has revealed that its diet is now almost entirely comprised of Caridina nilotica, a small microphagous prawn, and juvenile Lates. Native fish species, except for the small pelagic Rastrineobola argenteus, are very rarely consumed. This change in diet is a result of the shattering impact Lates predation has had on the native fishes, which have been virtually wiped out. The original community, which was dominated by several hundred haplochromine species and the catfishes Clarias mossambicus and Bagrus docmac which preyed upon them, and included two endemic tilapiine cichlids and 38 species of non‐cichlids, no longer exists. It has been replaced by a community dominated by Lates which now accounts for well over 80% of the fish biomass in the Nyanza Gulf and very nearly 100% in the study area. The only other species regularly encountered were Oreochromis niloticus, an introduced tilapiine, and Rastrineobola argenteus, a native zooplanktivore.
The carotenoids of eggs of wild and farmed Atlantic salmon, and their changes during development to the start of feeding
Authors: Craik J. C. A. , Harvey S. M.
Published: January 2006

The only carotenoid detected in newly fertilized eggs of wild Atlantic salmon,Salmo salar, from western Scotland was astaxanthin at a concentration [μg carotenoid g−1wet wt of eggs, mean ±S.D. (number of parental females)] of 6.2±1.2(7) in 1982, 6.4±1.8(20) in 1983, and 7.6 ± 13(6) in 1984. In eggs of farmed Atlantic salmon the only carotenoid detected was canthaxanthin at concentrations which varied significantly between farms depending on the level of synthetic canthaxanthin in the broodstock diet. Thus on two farms using feed with 50 μgg−1, the levels were 11.8 ± 3.4(7) and 12.3 ± 2.9(6), while on two farms using 75μgg−1the levels were 18.7 ± 5.0(9) and 21.2 ± 2.7(21). The levels in eggs of one‐seawinter fish (grilse) did not differ from those of two‐seawinter fish reared on the same farm and diet. During development from newly fertilized egg to fry at the end of yolk‐sac absorption, the quantity of carotenoid present per individual decreased, presumably as a result of metabolism. Despite large differences in quantity present, the quantity so metabolized was fairly constant at 2–4 μg carotenoid g−1original egg weight for eggs from two‐seawinter farmed and wild salmon, except that in eggs from farmed grilse it was 7 μg g−1. In fry from wild eggs, 99.14% of the remaining carotenoid was present in the integument (skin and fins) as astaxanthin, astaxanthin monoester and astaxanthin diester. In fry from farmed salmon eggs, 47 ± 8% of the carotenoid present was found in the unused yolk oil droplets and in the liver, and 37 ± 6% was found in the integument as canthaxanthin and an unidentified metabolite of canthaxanthin. These findings explain visible colour differences between fry from wild parents and fry from canthaxanthin‐fed farmed parents, particularly in the fins, liver and residual oil droplets. The canthaxanthin metabolite was also found, together with canthaxanthin, in the skin of farmed adults fed canthaxanthin. Preliminary tests showed it to be unchanged by saponification but reduced by sodium borohydride. For eggs from the three farms incubated under the same conditions in the same season, percentage mortality both to the eyed stage and between hatching and first feeding varied significantly between farms, but percentage mortality between the eyed stage and hatching did not do so. Results combined from two seasons for eggs from three farms and one wild source showed that egg mortality between fertilization and the eyed stage was not significantly different between wild and farmed salmon, but mortality between the eyed stage and hatching, and between hatching and first feeding, were both significantly higher in farmed salmon than in wild salmon. Such differences could not be explained simply by the large differences in egg carotenoid content, but were almost certainly due to factors such as broodstock nutrition, broodstock management, and stripping and fertilization procedures.
The breeding‐season population structure of three sympatric, territorial sticklebacks (Pisces: Gasterosteidae)
Authors: Whoriskey F. G. , Fitzgerald G. J. , Reebst S. G.
Published: January 2006

Animals breeding only once late in life should spend most of the time during their one reproductive season attempting to reproduce. Contrary to this prediction, we found that the individuals of three species of sticklebacks (Pisces: Gasterosteidae) spent very short periods of time on their breeding ground. Tidal flooding of the site controlled patterns of fish immigration and emigration. Inundations early in the breeding season brought in new immigrants which replaced most resident fish. However, towards the end of the breeding season there was less immigration and a higher percentage of the residents remained in their pools. We expected to see movements among pools by surplus males searching for sites to establish a territory; instead, few fish moved among pools, and most of those that did were females. A high energetic cost of breeding in this unstable habitat may best explain these residency patterns.
The influence of sex and spawning on levels of tryptophan, serotonin and 5‐hydroxyindoleacetic acid in the brains of wild brook trout, Salvelinus fontinalis
Authors: Sloley B. D. , Cunjak R. A. , Power G. , Downer R. G. H.
Published: January 2006

Levels of tryptophan (TP), serotonin (5‐hydroxytryptamine, 5HT) and 5‐hydroxyindoleacetic acid (5HIAA) have been determined in the brains of wild brook trout, Salvelinus fontinalis (Mitchill), and brown trout, Salmo trutta L., using high performance liquid chromatography with electrochemical detection. Immediately prior to spawning, adult female brook trout exhibit higher levels of 5HT in the brain than adult males, immature brook trout and immature brown trout. After spawning, the highest levels of TP are found in spent males, which also have higher levels of 5HT in the brain than spent females and immature brook trout. Immature brook trout exhibit higher levels of 5HIAA than prespawning adults. This difference disappears after the spawning season. Serum protein levels and condition factors are lower in spent female brook trout; however, haematocrit values for both sexes remain unchanged after spawning.
Spatial and temporal distribution of whiting (Sillaginidae) in Moreton Bay, Queensland
Authors: Weng H. T.
Published: January 2006

Five species of whiting (Sillaginidae) inhabit Moreton Bay. The school whiting, Sillago bassensis, and stout whiting, S. robusta, are rare, caught occasionally by trawlers in areas of sandy substrates. The sand whiting, S. ciliata, golden‐lined whiting, S. analis, and trumpeter whiting, S. maculata, are very common throughout the year. Sillago maculata is distributed almost throughout Moreton Bay, from 1 to 30 m depth. Sillago ciliata and S. analis are shallow water dwellers, from the shoreline to 3 m and 5 m depth, respectively. In the shallow waters, S. ciliata prefers the sandy substrates and S. analis the mud‐sandy substrates. Distributions related to the depth, habitat preference, juvenile‐adult grounds, food availability, interspecific competition, and winter season are discussed.
A light intensity threshold for schooling in the Atlantic mackerel, Scomber scombrus
Authors: Glass C. W. , Wardle C. S. , Mojsiewicz W. R.
Published: January 2006

The schooling behaviour of Atlantic mackerel was studied in a large tank at different light intensities in the range 12.6–1.8 × 10−10μEs−1 m−2. Variable light intensity was produced by accurately controlling the current to a green light‐emitting diode (LED) 3 m above the experimental tank. Under high light levels (1.8 × 10−6μEs−1 m−2) mackerel always formed a single school, whereas at lower levels (1.8 × 10−8μEs−1 m−2) they swam as individuals. At light levels down to 1.0 × 10−6μEs−1 m−2 the mean nearest neighbour distance in a school remained relatively constant (0.3–0.9 body lengths), and individual mackerel swam along a path which deviated from the position of their nearest neighbours by less than 14°. As light dropped below 1.8 × 10−7μEs−1 m−2, both nearest neighbour distance and heading angle between nearest neighbours increased, with mean values of 1–1.8 body lengths and 23–92°, respectively, at 1.8 × 10−9μEs−1 m−2. The results are discussed in terms of ambient light conditions in the sea.
Mate choice in the monogamous and polychromatic Midas cichlid, Cichlasoma citrinellum
Authors: Barlow G. W.
Published: January 2006

Choice of mate in the Midas cichlid, Cichlasoma citrinellum (Günther, 1864), has been examined from a number of perspectives, proceeding from general species attributes to individual differences.

The Midas cichlid discriminates against closely‐related, highly‐similar Cichlasoma, and recognizes sex, probably chemically in both cases. It is polychromatic and changes from the normal (N) pattern to gold (G) or even white at almost any age. Gold colouration inhibited attack and made it difficult to mate an N female with a G male; the inhibiting effect was cancelled by using a larger N female.

Because the Midas cichlid is also biparentally monogamous, early experience could easily influence later choice of mate. G females of G × G parents preferentially spawned adjacent to G males; N females of N × N spawned mainly before N males. N females of G × G pairs, however, showed no preference.

Groups of females were reared by all four combinations of two colours and two sexes, or by no parents. Females reared by identically pure‐coloured parents responded most to males of those colours, whereas females raised by mixed‐colour parents did not discriminate. Females reared without parents preferred N males. Regardless of their own or their parents' colour, juveniles spent more time with N juveniles and behaved less aggressively towards them, compared to G juveniles.

Fish were offered a choice among potential mates that differed in aggressiveness, size or breeding experience. Males did not choose on the basis of those traits. Females preferred large, aggressive, experienced males. Pairs with large aggressive males more readily kept a breeding territory, and aggressive experienced males guarded young more effectively. All females were equally aggressive in protecting their young.
The development of shoaling behaviour in the European minnow, Phoxinus phoxinus
Authors: MaGurran A. E.
Published: January 2006

The effects of development and disturbance on schooling and shoaling were observed in laboratory‐raised minnows. Both behaviours were present at the onset of free swimming. Shoaling increased to become the most important behaviour by 3 weeks after emergence from gravel, while the main increase in schooling behaviour occurred at 4 weeks. These changes were accompanied by rises in elective group size and in the number of following responses, and by a decrease in nearest neighbour distance. The increases in social behaviour were observed at an earlier stage in the same minnows threatened by a standard net chase. The main increase in schooling in disturbed minnows took place between 3 and 4 weeks after emergence; after this time schooling became the dominant behaviour. Disturbed fish were also more likely to follow another minnow during an encounter.
Seasonal occurrence of metazoan parasites of Puntius binotatus in an irrigation canal, Pulau Pinang, Malaysia
Authors: Leong T. S.
Published: January 2006

Two hundred specimens of the cyprinid fish Puntius binotatus were collected over a period of 1 year, February 1976–January 1977, from an irrigation canal in Palau Pinang, Malaysia. Six species of parasites were recovered: Dactylogyrus sp., Rhabdochona penengensis Furtado, 1965; Proteocephalus sp., Bothriocephalus acheilognathi Yamaguti, 1934, Pallisentis gaboes MacCallum, 1918 and Lamproglena minula Capart, 1943. The prevalence and mean density of two ectoparasites (Dactylogyrus sp. and L. minuta) and an endoparasite (B. acheilognathi) were examined in relation to season and host size. Fish were found to be free of these parasites in many months of the year. Prevalence and mean density of Dactylogyrus sp. and L. minuta were found to be highest during the early part of wet season, whereas those of B. acheilognathi were found to be highest in the later part of wet season. Prevalence of L. minuta increased with increasing size offish, but mean density was least in the largest fish. Both prevalence and mean density of B. acheilognathi were highest in smaller fish, whereas that of Dactylogyrus sp. showed little variation in the three size–groups.
Fine structure and cytochemistry of the endothelial cells and rodlet cells in the bulbus arteriosus in species of Cichlidae (Teleostei)
Authors: Leknes I. L.
Published: January 2006

The ultrastructure of endothelial cells and rodlet cells in the bulbus arteriosus of specimens representing six genera of Cichlidae is described. The former are very closely packed by membrane–bound and mainly electron–dense inclusion bodies (0.3–0.7μm).

In Apistogramma ramirezi I observed numerous subendothelial rodlet cells throughout the entire length of the bulbus arteriosus. These cells penetrate the endothelium and connect to the latter by desmosomes and tight junctions. The luminal part of the cell contains numerous vesicles and tubules (width 50–100 nm), whereas the basal part is occupied by a number of membrane–bound, club–like inclusions (length ≤ 5 μm). Between these two layers there occurs a layer of small, elongated mitochondria. Peripherally, these cells consist of a filamentous wall, except in the apical area.

The endothelial and rodlet cell inclusion bodies do not react with phosphotungstic acid (pH 1) or Sudan black B stain. The endothelial cells react strongly with periodic acid–Schiff (PAS) stain, whereas the rodlet cells are only moderately coloured by this stain.

The present results are discussed and compared with those reported previously for endothelial/ endocardial cells and rodlet cells in bony fish.
Uptake, time‐course distribution and elimination of cadmium in embryos and tissues of the pregnant Zoarces viviparus (L) after intraovarian loading
Authors: Joensen J. E. , Korsgaard B.
Published: January 2006

Uptake, time‐course dependent distribution and elimination of cadmium after intraovarian loading with 0.5 mg Cd kg−1 body weight was investigated in the pregnant Zoarces viviparus (L), to elucidate the dynamics in the maternal‐foetal exchange of cadmium. After 7.5 h 95% of the injected cadmium was eliminated from the ovarian fluid, and half‐life was calculated as T1/2= 100 (S.D. 48) min. It took 48 h to eliminate 95% from the serum, where the half‐life of cadmium was T1/2= 11 (S.D. 3) h. The concentration of cadmium in the embryos increased during the first 5 h postinjection. However, a decrease was observed during the latter part of the experimental period. The liver and kidney of the mother fish showed a continuous accumulation during the 72‐h period of investigation. The negative linear correlation between elimination from the serum and the uptake in the liver, was calculated to be r=−0.79.
Haematological and haematopoietic response to sodium chloride stress in a freshwater air‐breathing fish Channapunctatus Bloch
Authors: Dheer J. M. S. , Dheer T. R. , Mahajan C. L.
Published: January 2006

Results of experiments to determine the sensitivity of Channa punciatus to different levels of sodium chloride (NaCl) (1.2, 3.2 and 6.2g 1−1) are reported. It was found that C. punctatus which is otherwise considered a hardy fish is more sensitive to higher levels of sodium chloride stress. Thus 10% of the LC50 96 h value (1.2 g 1−1 NaCl) was found stressful as evidenced by loss in body weight, while 25 and 50% of the LC50 96 h value (3.2 and 6.2 g 1−1 NaCl) even resulted in mortality. Haematological and associated haematopoietic investigation confirmed stress symptoms in all the parameters tested. Thus microcytic hypochromic anemia together with leucopenia was indicated at the two higher sublethal levels, i.e., 25% and 50% of LC50 96 h value. Differential leucocyte count showed that leucopenia is mainly contributed by thrombocytic and neutrophilic decrease. Other cell types, viz., eosinophils, basophils, large and small lymphocytes, showed a relatively significant (P < 0.01) increase in number.

Haematopoietic studies revealed that the two penultimate stages in both RBC and neutrophil development closely follow the trend of their counterparts in the peripheral blood. However, the stem cells of both these cell types recorded significant increase under sodium chloride stress, which indicated homeostatic response. Biochemical studies revealed a depletion in blood glucose level as well as in liver and muscle glycogen reserves.

Restoration to normal control conditions after 6 weeks of exposure to different levels of sodium chloride stress resulted in a cessation of mortality (if any), gain in body weight and more or less normality in all the haematological parameters within a period of 2 weeks.
Some aspects of the infection of bib, Trisopterus luscus (L.), by the parasitic copepod Lernaeocera lusci (Basset‐Smith, 1896) in Portuguese waters
Authors: Eiras J. C.
Published: January 2006

Winter samples totalling 2308 specimens of Trisopterus luscus (total length range: 13–36 cm) caught in northern Portugal were examined for infections with Lernaeocera lusci. Infection prevalence was of 42%, and infection intensity was 1.7 copepods per infected fish. Individual infection varied between 1 and 9 copepods per infected specimen; 30.6% of the fish had bilateral parasitosis. There was a significant correlation (P<0.01) between fish length and prevalence. Length‐weight relationships of uninfected and infected fish were not significantly different (P > 0.05) and thus provide evidence that L. lusci has no effect on the condition of T. luscus in all the examined 1–cm size classes.
The food habits of four small‐sized species of Mormyridae from the floodplain pools of the Sokoto‐Rima river basin, Nigeria
Authors: Hyslop E. J.
Published: January 2006

The diet of four species of the family Mormyridae, commonly found in the floodplain pools of the Sokoto‐Rima river basin, Nigeria, is described. All four species are small‐sized and show a degree of food overlap. Evidence is presented, however, that resource partitioning occurs enabling co‐existence of the species in a habitat where food resources become increasingly limited after the cessation of the rains.
First records of Ligula intestinalis (Cestoda) in rainbow trout, Salmo gairdneri, and common bully, Gobiomorphus cotidianus, in New Zealand
Authors: Weekes P. J. , Penlington B.
Published: January 2006

Plerocercoids of the tapeworm Ligula intestinalis are reported from a salmonid, Salmo gairdneri, and an eleotrid, Gobiomorphus cotidianus, in New Zealand for the first time. There was no significant difference in condition factors between infected and uninfected trout. The prevalence of infection in bullies sampled increased with total length.
The effects of various diets on chitinase and ß‐glucosidase activities and the condition of cod, Gadus morhua (L.)
Authors: Danulat E.
Published: January 2006

Groups of cod, Gadus morhua (L.), were fed exclusively on fish, crustaceans, or crustacean shells for a period of 3 weeks. Chitinase and ß‐glucosidase activities were measured in enzyme extracts of stomach contents, stomach tissue, pyloric caeca, intestinal contents, and intestine tissue, and compared to the enzyme activities of control fish starved over the same period. Fulton's condition factor K, liver lipid content and liver water content were determined to estimate the effects of the diets on the condition of cod.

general, the highest chitinase activities were measured in samples of cod that had been fed on whole crustaceans. In this feeding group, there was also a remarkable increase of activity by a factor of four to eight in the pyloric caeca, compared to the group fed on fish and the control group, respectively.

Measurements of ß‐glucosidase activity revealed no similar dependence on food quality, ß‐glucosidase occurrence seemed to be mainly restricted to the pyloric caeca and the intestine of cod.
Ecological factors influencing the composition of the parasite fauna of the European eel, Anguilla anguilla (L.), in Ireland
Authors: Conneely J. J. , McCarthy T. K.
Published: January 2006

The parasites of 121 eels from three contrasting sites in the Corrib catchment area, western Ireland, were investigated. Thirteen species, Ergasilus gibbus, Diplostomum gasierostei, Diplostomum spathaceum, Sphaerostoma bramae. Bothrocephalus claviceps, Proteocephalus macrocephalus, Camallanus lacustris, Cucullanus truttae, Paraquimperia tenerrima, Raphidascaris acus, Acanthocephalus clavula, Acanthocephalus lucii and Pomphorhynchus laevis, were recorded. Two species, P. macrocephalus and P. tenerrima, have not previously been reported from Ireland. Microhabitat preferences of the parasites were noted. Variations in the occurrence and intensities of the parasites observed were analyzed in relation to sampling period, host habitat and characteristics of the eel populations studied. A variety of factors were shown to be of importance, including composition of the fish communities and distributional patterns of intermediate hosts and piscivorous birds. Differences were noted in the parasit‐ocoenoses of eels in still and running water sites. The occurrence and intensities of infection of several parasite species were shown to be related to age and size of host: the occurrence of B. claviceps. C. truttae, P. tenerrima and R. acus was shown to be related to either age or size of eels, which is accounted for by the fact that eels become increasingly piscivorous with age and increasing size. Little evidence of interspecific interactions was noted.
Morphology and biochemical genetics of Atlantic halibut, Hippoglossus hippoglossus (L.), from various spawning grounds
Authors: Haug T. , Fevolden S. E.
Published: January 2006

Potential phenotypic/genotypic differentiation of Atlantic halibut, Hippoglossus hippoglossus (L.), samples from two spawning grounds in north Norway (Malangen and Sørøysund) were studied. In addition, the genetic relationship between fish from north Norway, mid–Norway (Folia) and western Greenland (off Fredrikshåb) was investigated. Uni– and multivariate analyses of 15 morphometric measurements and six meristic counts revealed a considerable degree of homogeneity between Malangen and Sørøysund. No morphological characters were thus found suitable as diagnostic tools in the classification of potential halibut stocks. As determined from electrophoretic studies, the allelic distribution at the four polymorphic loci ADA, PGI–2, PGM–2, and UTP (unidentified tissue protein) did not vary significantly when all four samples (Folia, Malangen, Sørøysund and Greenland) were considered together. However, when the Norwegian coast samples were split into a northern (Sørøysund and Malangen) and a middle (Folla) area, and each locus was regarded isolated, significant heterogeneity was detected at the PGM–2 locus, thus giving evidence for a potential heterogeneity along a north–south axis.
Geographic variation in thermal tolerance of a widespread minnow Notropis lutrensis of the North American mid‐west
Authors: Matthews W. J.
Published: January 2006

Eighteen populations of Notropis lutrensis, representing all of the major river systems occupied by this species across an 1100km north‐south span of its range, showed no significant differences in mean critical thermal maximum (CTM), although general north‐south differences in climatic temperatures exist. There were no clinal trends in CTMs, and CTMs were unrelated to stream size or any other discernible feature of the local habitats. Previous research has shown that N. lutrensis can adapt rapidly to an artificially altered thermal regime. The present results suggest that even though a species may have potentially ‘labile’ thermal physiology, it may nonetheless be ‘static’ or evolutionarily conservative in such characters when natural populations are examined empirically.
Electrophoretic examination of the population structure of brown trout, Salmo trutta L., from the Lough Neagh catchment, Northern Ireland
Authors: Crozier W. W. , Ferguson A.
Published: January 2006

Samples of brown trout, Salmo trutia L., from 34 locations throughout the Lough Neagh system in north‐east Ireland were electrophoretically examined for genetic variation at 28 enzyme loci. Patterns of allelic variation at 12 polymorphic loci indicated the existence of genetic differentiation within as well as among several river systems, suggesting the existence of multiple brown trout populations. Significant gene frequency differences were detected over distances as little as 3 km, demonstrating the propensity of this species for microgeographic genetic differentiation. This was confirmed by a hierarchical analysis of genetic variance, some 35% of among‐sample variance being distributed within tributaries. Within Lough Neagh itself significant genetic differentiation was detected between two morphotypes (dollaghan and salmon‐trout) and for one of these (dollaghan) among samples from different years and from different areas of the lough. This suggests the existence of genetically differentiated subpopulations of originating from separate river catchments.
Thermal preferences in upstream migrating glass‐eels of Anguilla anguilla (L.)
Authors: Tongiorgi P. , Tosi L. , Balsamo M.
Published: January 2006

The effect of temperature on the migratory behaviour of European glass‐eels, Anguilla anguilla, during the first stages of their ascent into inland waters has been investigated. Very little research has documented the thermal preferences of glass‐eels, most being directed instead to the study of their thermal resistance and survival. The experimental method adopted aimed at acquiring information on short‐ and long‐term thermal choices and sought to provide evidence of the influence of preceding experiences on choices made during the tests. The results obtained in short‐term choices (acute preferendum tests) show a clear preference for flows of water at temperature equal to acclimation temperature rather than for flows at temperatures lower or higher by 3° C. It is sufficient for the glass‐eels to remain for about 1 h at a different temperature (acclimation temperature ± 3–4°C) for their subsequent choices to be influenced. When choosing between flows warmer or colder than acclimation water, glass‐eels prefer the lower temperature. When the temperature presented is very low (about 3° C) the preference is inverted. There is evidence that the temperature gradient represents one of the main orienting cues. In long‐term choices (final preference tests) the experimental apparatus allowed prolonged observation (from 24 to 52 h) of the choices between three shelters, the only difference between these being their internal temperatures. In this situation the glass‐eels show a clear preference for temperatures higher than that of the environment. For both intervals of environmental temperature considered (11.0–12.6°C and 14.3–17.3° C) a linear correlation exists between temperature difference and number of choices made for the shelters at higher temperatures. The number of glass‐eels choosing a higher temperature is greater in the case of lower environmental temperature. In acute preference tests the thermal stimulation is added to a rheotactic response. The glass‐eels find themselves in an analogous situation to that during the ascent. On the other hand, in the second experimental situation the choices are an expression of a pure thermal preference.
Changes in selected haematological parameters in juvenile chinook salmon subjected to a bacterial challenge and a toxicant
Authors: Iwama G. K. , Greek G. L. , Randall D. J.
Published: January 2006

An infection and a toxicant were presented singly and in combination to juvenile chinook salmon. The fish were challenged with Renibacterium salmoniarum and exposed to two levels (0.05 and 0.50 × 96 h LC50) of the toxicant sodium pentachlorophenate. The experiment comprised measurement of seven blood parameters and observations on mortality and behaviour at 4‐day intervals over a period of 40 days.

All fish receiving the combined treatment of bacterial challenge and higher level of toxicant died 12 days post‐infection on the 8th day of toxicant exposure. Mortalities also occurred in the groups of diseased fish and fish receiving the toxicant alone. There were no mortalities in the appropriate control groups of unchallenged fish in clean water.

Most of the haematological changes pointed to a general haemodilution probably arising from progressive damage to the kidney and haematopoietic tissue by bacteria but which did not appear to be greatly affected by combined exposure to the toxicant. The blood parameters of the fish in clean water as well as those exposed to just the toxicant remained relatively constant. Higher mortality and sustained lower values of haematocrit, haemoglobin and glucose concentrations as well as red blood cell counts were present in both the diseased group of fish held in clean water and the disease plus low level toxicant group compared to the control fish; white blood cell counts were low initially but increased markedly as the infection progressed. This latter treatment combination also produced lower total protein and blood urea nitrogen concentrations.
Mating of anadromous Atlantic salmon, Salmo salar L., with mature male parr
Authors: Myers R. A. , Hutchings J. A.
Published: January 2006

Sexually mature male parr successfully mated with female anadromous Atlantic salmon, Salmo salar, in the absence of anadromous males. There was no significant difference between the proportion of eggs fertilized by mature male parr and anadromous males. One of the demographic consequences of our observations is that overfishing could eventually eliminate anadromy in male members of a population.
The effect of sublethal endrin exposure on rainbow trout, Salmo gairdneri Richardson. I. Evaluation of serum cortisol concentrations and immune responsiveness
Authors: Bennett R. O. , Wolke R. E.
Published: January 2006

Two‐hundred‐and‐forty rainbow trout, Salmo gairdneri, were exposed for 30 days to sublethal concentrations of the pesticide endrin. On day 30, ten fish from each treatment group were sacrificed and examined for the ability of peritoneal macrophages to phagocytize latex beads. The remaining fish were immunized with 10 μg of Yersinia ruckeri O‐antigen, and exposure to endrin continued. The migration inhibition factor assay (MIF), plaque forming cell assay (PFC), and serum agglutination titres (SAG) were performed 2, 14, and 30 days post‐antigen inoculation. Serum was collected from all fish for serum cortisol concentrations. Endrin exposure had no effect on the phagocytic ability of peritoneal macrophages. However, the MIF, PFC and SAG responses were significantly reduced from control values. Serum cortisol concentrations were found to be significantly elevated in endrin‐exposed fish. Serum cortisol concentrations were found to be significantly higher on days 44 and 60 (192 and 194 ng ml−1, respectively) when compared to days 30 and 32 (159 and 141 ng ml−1, respectively). Cortisol values for days 30 and 32 did not differ significantly, nor did those of days 44 and 60. The relationship between elevated serum cortisol concentrations and endrin exposure on the immune response is discussed.
Diel feeding chronology, gastric evacuation and estimated daily ration of juvenile coho salmon, Oncorhynchus kisutch (Walbaum), in the coastal marine environment
Authors: Brodeur R. D. , Pearcy W. G.
Published: January 2006

The feeding periodicity of juvenile coho salmon, Oncorhynchus kisutch, was examined from stomach collections taken during five sampling periods in coastal waters off Oregon. Significant differences in stomach content weight were found between several consecutive 3‐hour periods, with peak fullness occurring in early morning and around dusk. The rates of gastric evacuation of euphausiid meals were measured in the laboratory at two temperatures. The decline in stomach contents was best described by an exponential model: 90% evacuation of the wet weight contents required an estimated 28.4 and 18.1 h at 11.4 and 13.7° C, respectively. The method of Elliott & Persson was used to estimate a daily ration of 2.4 and 3.7% of the wet body weight at the two temperatures.
A key to the species of cestodes (tapeworms) parasitic in British and Irish freshwater fishes
Authors: Chubb J. C. , Pool D. W. , Veltkamp C. J.
Published: January 2006

Methods for the collection, fixation, preservation and examination of the cestodes parasitic in British freshwater fishes are described. An illustrated key to the species is provided, with the exception of the members of the genus Proteocephalus, for which the information is tabulated.
The record of daily growth in otoliths of Atlantic silversides, Menidia menidia, from field and laboratory
Authors: Barkman R. C. , Bengtson D. A.
Published: January 2006

Otoliths were removed from field‐collected silversides of age less than 3 months. Otolith diameter was highly correlated with total length of the fish. Daily growth ring counts for this species are known to be a function of age rather than size, so widths for the daily growth rings provide a record of daily increases in length of the fish. Measurement of ring widths showed that weekly specific growth rate was greater than 70% at age 1 week, but declined to about 30% at age 1 month and about 15% at age 2 months. A laboratory experiment in which temperature was changed on a weekly basis demonstrated that environmental variables can affect the width of rings. Nevertheless, the growth rate of field‐collected fish, as calculated from otolith ring widths, was more highly correlated with size of fish, as measured by otolith radius, than with the environmental variables of temperature, salinity and plankton abundance. Back‐calculation of growth rates from otolith ring widths of five fish collected at the end of the growing season yielded the same age‐growth curves as were obtained from 203 fish collected biweekly during the season.
Biometrical and biological features of Alburnus alburnus×Rutilus rubilio natural hybrids from Lake Mikri Prespa, northern Greece
Authors: Crivelli A. J. , Dupont F.
Published: January 2006

Morphometric and meristic characteristics of a rare hybrid between the Adriatic roach. Rutilus rubilio, and the bleak, Alburnus alburnus, discovered in Lake Mikri Prespa, north‐western Greece are described. Axis 1 and 2 of a discriminant analysis using all morphometric and meristic features explains 99.5% of the total variability of the hybrid and both its parents. No back‐crossing is detected in the discriminant analysis: all hybrids found are F1 fish. Age and length of the hybrid and its parents were measured; the best‐fit growth model is the logistic curve. Growth of the hybrid is faster than that of the Adriatic roach and slightly faster than that of the bleak: this indicates heterosis. Problems in the systematics of genera of European cyprinids are discussed.
A unique teleost dermal organ in a new European genus of fishes (Teleostei: Gobioidei)
Authors: Bianco P. G. , Bullock A. M. , Miller P. J. , Roubal F. R.
Published: January 2006

The freshwater fish fauna of Greece is a diverse assemblage of mediterranean, Ponto‐Caspian, and endemic western Greek elements. In the last category, a gobiid from Epirus has been found to possess a dermal perianal organ unique among teleosts, as well as systematic features warranting recognition of a new genus, Economidichthys gen. nov. (type‐species Gobius pygmaeus Holly, 1929). The perianal organ is a sharply‐demarcated, pitted area on the rear abdomen. Light‐and electron‐microscopy has revealed numerous specialized microvillous cells lining the pits and evidently secretory in function. Presence of the organ in both sexes, its ventral position and the secretory activity originally suggested an attachment role rather than involvement in reproduction, but obvious correlation with habitat is lacking and alternative functions are discussed.
Activation of rainbow trout macrophages
Authors: Chung S. , Secombes C. J.
Published: January 2006

Rainbow trout peritoneal macrophages were stimulated in vitro using Concanavalin A (Con A) and in vivo using formalin‐killed Aeromonas salmonicida in Freund's incomplete adjuvant (FIA). Whether these cells had been activated was determined by the measurements of oxygen anions (NBT reduction), H2O2 production (oxidation of phenol red), RNA synthesis (3H‐uridine incorporation), acid phosphatase activity and bactericidal activity.

In vitro‐stimulated macrophages showed an increased NBT reduction and 3H‐uridine incorporation over a range of Con A concentrations, compared with untreated control macrophages, but no detectable increases in H2O2 production or bactericidal activity were observed. On the other hand, in vivo‐stimulated peritoneal cells showed increases in all the assays compared with FIA‐elicited control cells, and were considered to have been activated.
The phagocytic ability of neutrophils and serum lysozyme activity in experimentally infected carp, Cyprinus carpio L.
Authors: Siwicki A. , Studnicka M.
Published: January 2006

The phagocytosis of neutrophils and serum lysozyme activity were investigated in carp experimentally infected with Pseudomonas alcaligenes and Aeromonas punctata. The total leucocyte numbers, relative leucocyte counts, nitroblue tetrazolium (NBT) reduction, NBT test rate, lysozyme activity and lysozyme index were examined on days 7, 14 and 21 after injection. On days 7 and 14 there was a significant increase in total leucocyte numbers and serum lysozyme activity, but a decrease in the NBT test rate and lysozyme index. NBT reduction was unchanged compared with the control group. On day 21 the total leucocyte numbers and lysozyme activity had declined and were less than control values, but there was a significant increase of the NBT test rate, NBT reduction and lysozyme index.
Induction of immunosuppression to bacterial antigens in carp, Cyprinus carpio
Authors: Wishkovsky A. , Avtalion R. R.
Published: January 2006

Typical primary antibody responses were found after injecting carp maintained at 25°C with formalin‐killed (Fk) Vibrio anguillarum bacteria, but not in fish injected with the same antigen held at 12° C. There were no significant increases over the primary responses in fish receiving a second injection 60 days after the first injection.

The differences in the results between fish groups receiving three V. anguillarum antigens at two dosages were found to be insignificant in most of the experiments. A comparison of the antibody titres of fish groups after challenge with Fk bacteria showed no difference from control fish receiving a single injection similar to the challenge dose or fish receiving a previous injection with the antigens emulsified in complete Freund's adjuvant (CFA) at 25° C. However, significant immunosuppression was found in fish that were given the primary injection intracardially at 25° C or 12° C, or with CFA emulsion at 12° C.
Preliminary studies on eicosanoid production by fish leucocytes, using GC‐mass spectrometry
Authors: Rowley A. F. , Barrow S. E. , Hunt T. C.
Published: January 2006

Culture supernatants from dogfish leucocytes, exposed to the Ca2+ ionophore A23187, were analyzed for eicosanoid production by gas chromatography‐electron capture mass spectrometry. Consistently high levels of the prostaglandins (PG) D2, F2α and E2 were produced, while thromboxane B2 and leukotriene B4 were found in smaller amounts. No 6‐oxo PGF1α, a degradation product of prostacyclin, or 13,14‐dihydro‐15‐oxo‐PGF2α, a metabolite of PGE2 and PGF2α, were detected. The results are compared with similar experiments using mammalian leucocytes.
Effects of cortisol on immunity in red drum, Sciaenops ocellatus
Authors: Thomas P. , Lewis D. H.
Published: January 2006

The immunocompetence of juvenile laboratory‐reared red drum treated with cortisol in the diet (250 and 500 mg kg−1 food) was assessed following intramuscular administration of bacterio‐phage (Escherichia coli OX 174), washed bovine erythrocytes (1% suspension) and bovine serum albumin (100mg). Cortisol induced suppressive effects on the fish response to two of the three antigens (i.e., haemagglutinating activity to bovine erythrocytes and precipitin development to bovine serum albumin). These differential effects of cortisol on T‐dependent antigens could be interpreted as evidence for heterogeneity of red drum T lymphocytes.
Cellular mechanisms of glucocorticoid immunosuppression in salmon
Authors: Kaattari S. L. , Tripp R. A.
Published: January 2006

Limiting dilution analysis was employed to determine the effect of cortisol and conditioned media on precursor frequency and clone size of antibody‐producing cells sensitive to trinitrophenylated‐lipopolysaccharide (TNP‐LPS). This analysis demonstrated that the restoration of the cortisol‐suppressed antibody response by conditioned media occurs through the activation of previously inhibited B cell precursors to that antigen, and not by the recruitment of other antigen‐insensitive B cell precursors.
Immune responses in the bicolor damselfish, Pomacentrus partitus, and their potential role in the development of neurogenic tumours
Authors: Schmale M. C. , Mckinney E. C.
Published: January 2006

Bicolor damselfish on southern Florida reefs are commonly affected by a disease consisting of Schwann cell tumours. Several features of this disease, termed damselfish neurofibromatosis (DNF), indicate that the immune system of these fish may play an important role in the expression and rate of progression of the tumours. The majority of fish in the advanced stages of DNF showed abnormal, presumably degenerative, histological changes in both the spleen and kidney, suggesting that a general, non‐specific suppression of immune responses might be occurring. This hypothesis was supported by results of mitogen‐induced proliferation and mixed leucocyte responses in fish with DNF which indicated a near total failure of several functions of the immune system involving the pronephros and the spleen. A sparse infiltrate of granulocytes and monocyte/macrophages was seen in these tumours.
Cercariae and diplostomules of Diplostomum spathaceum (Digenea) elicit an immune response in rainbow trout, Salmo gairdneri Richardson
Authors: Whyte S. K. , Allan J. C. , Secombes C. J. , Chappell L. H.
Published: January 2006

The immune response of rainbow trout to cercariae and diplostomules of Diplostomum spathaceum was investigated. Following immunization, serum was tested for the presence of antibody, using an enzyme‐linked immunosorbent assay (ELISA) and immunofluorescence. Circulating antibody was detected to both cercariae and diplostomules by 6–7 weeks postimmunization and the sera were tested for their cross‐reactivity with the other larval stage, using an ELISA.
Electron microscopic examination of antigen uptake by salmonid gill cells after bath immunization with a bacterin
Authors: Zapata A. G. , Torroba M. , Alvarez F. , Anderson D. P. , Dixon O. W. , Wisniewski M.
Published: January 2006

Atlantic salmon, Salmo salar, were given 2‐min bath immunization with Yersinia ruckeri O‐antigen bacterins at doses of 10, 100, and 1000 μg ml−1. The uptake of the antigen was followed by light and electron microscopy of samples taken immediately and periodically after immunization, and the immune response monitored by the passive haemolytic plaque assay. The particulate antigen was observed in the gill mucus, adhering to and within the pavement cells covering the gill filaments, and in mononuclear phagocytes below the epidermal gill cells. There was a direct doseresponse correlation in the observed immune response according to the numbers of splenic antibody‐producing cells 14 days after immunization. The cells involved in the recognition and uptake of a bacterin are initial important steps in the immune response, and these studies may aid in the immunopotentiation of fish vaccines and bacterins.
Intact protein (antigen) absorption in fishes: mechanism and physiological significance
Authors: Mclean E. , Ash R.
Published: January 2006

Although the literature indicates that there is no longer any reason to doubt that the fish gut possesses the capacity to absorb intact protein macromolecules, neither the exact mode of protein absorption nor the physiological significance of this phenomenon has been established. A review of the literature relating to evidence concerning the probable mechanism(s) of absorption and the means by which this process may confer physiological advantage is presented.
Breeding behavioural pattern of the lake fish Tilapia discolour Gunther (Teleostei, Cichlidae) in captivity
Authors: Owusu‐Frimpong M.
Published: January 2006

Close observation of the breeding activities of specimens of Tilapia discolour obtained from Lake Bosomtwe and held captive in glass aquaria, a net cage and a pond showed that this species practises substrate‐brooding; the eggs were incubated and hatched in prepared nests. However, brief egg‐carrying tendencies were observed; both the male and female brood fish carried the eggs in their mouths from the sites of spawning to new sites. Both sexes also made and guarded the nests, incubated the eggs and provided protection to the young fry.
Age and growth rate determination of southern bluefin tuna, Thunnus maccoyii, using otolith banding
Authors: Thorogood J.
Published: January 2006

Otoliths of southern bluefin, Thunnus maccoyii, of between 42 cm and 167 cm f.l., taken from waters off New South Wales, South Australia, and Western Australia were prepared to reveal annual banding. Methods of preparation and examination are detailed.

Otolith growth was demonstrated to be directly proportional to fish growth over the size range studied. Sampling over 13 months provided validation of the annual nature of bands for fish in their 3rd, 4th and 5th year of growth. Band formation of fish in their 2nd, 6th, 7th, 8th and 9th years of growth also appeared to be annular, though samples were available from an insufficient number of months for confident validation.

Von Bertalanffy growth parameters derived from determined age‐at‐length are LL, 261.3cm;k, 0.108,t0, –0.157.
On a new species of electric catfish from Kainji, Nigeria, with some observations on its biology
Authors: Sagua V. O.
Published: January 2006

A new species of electric catfish,Malapterurus minjiriya, from Kainji, Nigeria, is described and a key for separating it from the two other known species is given. Notes on some aspects of the biology of the electric catfishes in Lake Kainji, Nigeria are included.
Food and feeding relationships of fish in the Sudd swamps (River Nile, southern Sudan)
Authors: Hickley P. , Bailey R. G.
Published: January 2006

The gut contents of 37 species of R. Nile fish are described. Classification according to diet shows four species to be mud‐feeders, three to be microherbivores, two to be macroherbivores and five to be omnivores. The remaining majority (23) are categorized as carnivorous and comprise one neuston‐feeder, one zooplanktivore, six bottom‐feeders, seven browsers in vegetation and eight macropredators. Food webs are proposed for three major ecological zones, namely the open‐water and submerged vegetation of a river‐lake, the floating fringe of Eichhornia crassipes and the seasonally flooded grassland.