bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of immunopotentiating agents on the immune response of rainbow trout, Salmo gair dneri Richardson, to ERM vaccine
Authors: Grayson T. H. , Williams R. J. , Wrathmell A. B. , Munn C. B. , Harris J. E.
Published: January 2006

The use of Bacille Calmette Guerin (BCG) and the saponin Quil‐A as a means of potentiating the immune response elicited by immersion vaccination of Salmo gairdneri with a commercial enteric redmouth (ERM) vaccine was investigated. The bactericidal activity of trout serum to Yersinia ruckeri, the causative agent of ERM, was enhanced by vaccination, although non‐specific factors appear to serve an important defensive function. Whilst the use of BCG and Quil‐A produced no conclusive improvement of the immune response, as determined by bacterial agglutination and serum bactericidal activity, some enhancement of in vivo bacterial clearance was apparent. Differences were observed in the susceptibility to trout serum of the three strains of Y. ruckeri tested.
In vitro response of Ichthyophthirius multifiliis to sera from immune channel catfish
Authors: Clark T. G. , Dickerson H. W. , Gratzek J. B. , Findly R. C.
Published: January 2006

Sera from channel catfish rendered immune to the protozoan pathogen Ichthyophthirius multifiliis were screened for activity against live parasites. Cells in the infective stage (tomites) were incubated in doubling dilutions of immune and pre‐immune sera from fish that had been immunized by exposure to sublethal infections. When examined by light microscopy, tomites were found to agglutinate in the presence of immune sera. While the stength of individual sera varied, agglutination of cells occurred at dilutions as high as 1:128. Cells showed little tendency to agglutinate in pre‐immune sera, and virtually no effects were seen with dilutions of pre‐immune sera greater than 1:16. Agglutination was usually accompanied by release of mucus from cells, and while tomites appeared to be immobilized, their cilia continued to beat. Low dilutions of immune sera appeared to be toxic. Similar effects on tomites were seen with rabbit antisera prepared against Ichthyophthirius cilia. The involvement of humoral antibodies in agglutination and protective immunity is discussed.
Esterases and phosphatases in the leucocytes of rainbow trout, Salmo gairdneri Richardson
Authors: Blaxhall P. C. , Doggett T.
Published: January 2006

A preliminary report is made on the distribution of acid phosphatases and acid esterases in the cells of rainbow trout. A modified technique for the cytochemical demonstration of acid esterases is given, resulting in clearer visualization. Lymphocytes undergoing transformation in the presence of phytohaemagglutinin show a parallel decrease in enzyme localization for acid esterase and acid phosphatase as transformation in culture proceeds.
The influence of thermal stratification on pelagic fish yields in Lake Kariba, Zambia/Zimbabwe
Authors: Mtada O. S. M.
Published: January 2006

Lake Kariba is thermally stratified for about 9 months of the year. The Tanganyika sardine, Limnothrissa miodon (Boulenger), thrives very well when the water is in circulation and when its food (zooplankton) is abundant due to increased nutrients in the water column. There is a fall in the sardine yields as the water column gets partitioned into a nutrient‐poor epilimnion and a nutrient‐rich hypolimnion during thermal stratification. A very high negative correlation (r2= 0.94, n= 32) was found between thermal stratification and the monthly yields of the sardines. This uneven annual distribution of sardine yields creates problems for the local fishery.
Post‐larval growth in the lateral white muscle of the eel, Anguilla anguilla
Authors: Romanello M. G. , Scapolo P. A. , Luprano S. , Mascarello F.
Published: January 2006

The post‐larval growth of lateral white muscle was studied in eels at different stages of post‐larval development (glass, yellow and silver eels) by means of histochemical methods for myosin‐ATPase (mATPase) activity, immunohistochemistry (for myosin isoforms) and electron microscopy.

Morphological, histo‐ and immunohistochemical data reveal a uniform appearance of white muscle in glass eels, whereas in following stages the typical mosaic appearance is present. Small‐diameter fibres show a more acid‐labile mATPase activity than large fibres and react with anti‐F, anti‐FHC and anti‐S sera, but not with anti‐SHC serum. In the silver stage, the small fibres tend to decrease in number as the size of the eels increases.

Electron microscopy reveals the presence of satellite cells at every stage: in glass eels there are also ‘activated’ elements showing scarce myofilaments in their cytoplasm; in yellow eels very small fibres are present, enveloped within the basal lamina of well‐differentiated muscle fibres; in silver eels there are no fibres showing signs of immaturity.

Presumably the post‐larval development of white muscle involves in juvenile eels a substantial recruitment of fibres from the satellite cell population; later the hyperplasia decreases or ceases and hypertrophy remains the only mechanism for muscle growth.
Relationship of density to growth and metamorphosis of caged larval sea lampreys, Petromyzon marinus Linnaeus, in Michigan streams
Authors: Morman R. H.
Published: January 2006

Larval sea lampreys, Petromyzon marinus, of the 1976 year class were studied between May 1977 and October 1981 in five Michigan streams to determine the relationship of density to growth and metamorphosis. Two cages were placed in each stream; one cage contained 25 larvae (low density group) and the other 75 larvae (high density group). Changes in body length, as an indicator of growth, were monitored in all streams from age I to V. Mean lengths ranged from 25 to 55 mm at the beginning of the study and from 102 to 158 mm at the end. Some ammocoetes attained lengths greater than 160 mm. Growth was related mainly to density; crowding affected growth from age I to metamorphosis. Mean increases of total length ranged from 90 to 128 mm among low‐density groups and from 54 to 97 mm among high‐density groups. Growth was typically greater in the cage with fewer lampreys in each stream. Most growth occurred from May to October when stream temperatures were highest. In two streams in which cages were not vandalized, 96% and 92% of the lampreys in the low‐density groups and 68% and 52% in the high‐density groups survived to age V. Metamorphosis occurred at age V in low‐density groups. Five lampreys (2.4%; range, 133–145 mm long) metamorphosed among the 207 that survived until completion of the study.
Fertility of roach × bream hybrids, Rutilus rutilus (L.) ×Abramis brama (L.), and their identification
Authors: Wood A. B. , Jordan D. R.
Published: January 2006

Adult roach, bream and their presumed F1 hybrid from an Anglian Water reservoir were identified on the basis of morphological and meristic characteristics. The hybrid was clearly intermediate. Four hybrid breeding crosses were induced to spawn by hypophysis. A bream × roach cross (female named first) failed to produce fertile eggs, whereas F1 hybrid × roach, roach × F1 hybrid and F1 hybrid × F1 hybrid all produced fry. Fertility (defined as survival of eggs to hatching) was high for the F1 hybrid × roach back‐cross (56%) but low for the others (<2%), in comparison to the pure species controls (roach 69%, bream 76%). Progeny from these crosses were reared until anal fin rays could be counted. These counts indicated intermediacy between the parents and back‐crossed individuals, and similarity between F1 hybrids and their F2 progeny.
Influence of temperature on yolk utilization by the white sturgeon, Acipenser transmontanus
Authors: Wang Y. L. , Buodington R. K. , Doroshov S. I.
Published: January 2006

The utilization of yolk nutrients by the white sturgeon was investigated at incubation temperatures of 11, 14, 17, and 20° C. The rates of development and dry matter loss are temperature dependent, with an upper critical temperature between 17 and 20° C above which survival is reduced (the temperature range investigated was not sufficient to allow determination of a lower critical temperature). The patterns of yolk utilization are similar to those of other fish. Protein depletion occurs at relatively constant rates throughout yolk nutrition, with the highest rate observed at 20° C. More than 95% of the original lipid levels were still present at hatch, except at 20° C (88%). After hatch, lipid content rapidly decreased at all temperatures, with fish incubated at 11° C possessing higher lipid levels at yolk depletion. The question of why the temperature tolerances of early life stages are more limited than those of older fish is discussed.
Predation on salmon smolts, Salmo salar L., in the estuary of the River Surna, Norway
Authors: Hvidsten N. A. , Møkkelgjerd P. I.
Published: January 2006

The post‐smolt stage of salmon, Salmo salar L., is subject to heavy mortality in Norway. Each year 35 000 hatchery‐reared smolts are stocked in the River Surna. Smolt stocking at sea and in the fjord resulted in recovery rates of adult salmon which were up to three times better than those resulting from river stockings. This was supposed to be due to by‐passing some predators. In 1984 and 1985 predators and their predation on smolts were studied in the R. Surna estuary. Cod, Gadus morhua, were found to prey heavily on smolts, and a total mortality up to 24.8% was found in a small restricted area. Cod are thought to assemble in the Surna estuary in the spring, foraging on the smolt run.
Feeding migration of roach, Rutilus rutilus (L.), in Lake Arungen, Norway
Authors: L'Abée‐Lund J. H. , Vøllestad L. A.
Published: January 2006

In the period April–July 1980 we studied the feeding migration and food of roach in a small tributary of the eutrophic Lake Årungen, south‐eastern Norway. Tagging experiments revealed a tendency in roach to utilize a specific tributary both for feeding and for spawning. The mean size of roach ascending the tributary in late June and July was significantly larger than the mean size of roach spawning 1–2 months earlier, probably due to higher water discharge in July than in May and June. The experiment indicates two separately motivated migrations involving homing. The roach fed more profitably in the tributary than in the lake, both in terms of food availability and predator avoidance.
Seasonal effects of pinealectomy on testicular recrudescence and secretory activity of seminal vesicles in the catfish Heteropneustes fossilis (Bloch)
Authors: Garg S. K.
Published: January 2006

The effects of pinealectomy on testicular activity and secretory activity of seminal vesicles were examined in the catfish Heteropneustes fossilis under various combinations of photoperiod and temperature during different periods of the annual reproductive cycle. Pinealectomy had no effect on gonadal activity during the preparatory, prespawning and spawning periods of the reproductive cycle. However, during the postspawning period, under long (LD 14:10) or short (LD 9:15) photoperiod at 25° C or at gradually increasing ambient temperature, pinealectomy accelerated testicular recrudescence and secretory activity of the seminal vesicles. Nevertheless. during this period the presence of the pineal facilitated the recrudescence of testes and seminal vesicles in catfish exposed to continuous light (LL), continuous darkness (DD) and 12 hL:l2 hD (LD) at 25° C. These findings suggest that the role of the pineal in catfish reproduction is variable and depends upon the photoperiod and temperature regimes to which the fish are exposed, as well as on the time of the year and the state of the reproductive cycle. The results also suggest that the effects of pinealectomy in catfish are mediated through an influence on the hypothalamo‐hypophyseal gonadal axis.
The cyprinodontiform gonopodium, with an atlas of the gonopodia of the fishes of the genus Limia
Authors: Chambers J.
Published: January 2006

The structure and mode of operation of the gonopodium (the modified anal fin of male poeciliid fishes) is described. A description of the distinctive characters of the gonopodium, with a figure, of each of the species of the genus Limia is given, together with a synonymy.
Co‐occurrence of three species of Choricotyle (Monogenea: Diclidophoridae) in the grunt Orthopristis ruber and their host‐specificity
Authors: Bashirullah A. K. M. , Rado N. E.
Published: January 2006

A total of 881 marine fish belonging to 11 species were examined for Choricotyle. Haemulon steindachneri was infected with C. reynoldsi (12%) and Orthopristis ruber with three species of Choricotyle: C. aspinachorda (40.6%), C. cynoscioni (15.2%) and C. reynoldsi (8.7%). Frequent co‐occurrences of two or three species in O. ruber were observed, but without any apparent sign of antagonism. Although Choricotyle was found in O. ruber (46%) and H. steindachneri (12%), no parasites were recovered from any of the 556 fish of the other nine species.
Influence of some environmental variables on the ascorbic acid status of striped mullet, Mugil cephalus Linn., tissues. III. Effects of exposure to oil
Authors: Thomas P.
Published: January 2006

Exposure to water‐soluble fractions (WSF) of a crude and two fuel oils altered the ascorbic acid (AsA) content of several striped mullet, Mugil cephalus, tissues. Exposure to sublethal concentrations of all three WSFs caused a depletion of AsA reserves in brain, gill, kidney and liver tissues, but not in muscle. There was a marked decline in AsA stores in kidney and gill tissues after only one day of exposure to WSFs of both crude and fuel oils. Liver AsA concentrations were significantly depleted after one week of oil exposure. Brain AsA content was only significantly depleted during chronic exposure to the highest oil concentration (20% WSF). A dose‐dependent depletion of AsA reserves in the liver but not in the other tissues was observed one week after a single exposure to 2–20% WSFs of a No. 2 fuel oil. Exposure to 20% WSF of the No. 2 fuel oil caused a 47% decrease in liver AsA content one week later. Hepatic concentrations were still significantly depleted after 15 days, but had returned to control levels 20 days after the initial exposure. The data suggest that the depletion of tissue AsA reserves in fish inhabiting oil‐contaminated environments could be sufficient on occasions to lead to AsA deficiency.
Seasonal activities of chitinase and chitobiase in the digestive tract and serum of cod, Gadus morhua (L.)
Authors: Lindsay G. J. H.
Published: January 2006

No statistically significant seasonal variations of chitinase and chitobiase in cod, Gadus morhua, stomach, intestine or serum could be detected. Enzyme activity often varied considerably (up to six‐fold) between fish captured at the same time, but no correlation could be detected between the presence of chitin or the amount of prey in the stomach and the activities of chitinase and chitobiase. Lysozyme was absent from all the tissues tested.
A procedure for obtaining erythrocytes from larval fish for cytological study and a description of larval blood of red hake, Urophycis chuss (Walbaum) and Atlantic mackerel, Scomber scombrus (Linnaeus)
Authors: Perry D. M.
Published: January 2006

A means of obtaining erythrocytes from larval fish and the blood of larvae of two fish species are described. Erythrocytes were obtained for cytological preparations from larvae of Urophycis chuss (Walbaum) and Scomber scombrus (Linnaeus) as small as 2.0 mm. Heart and gills were dissected from the larvae, stained, and flattened into a monolayer on a microscope slide. Mature erythrocytes were the only blood cell type observed in either heart or gill preparations, and these appeared to be the same as in the adult fish. Mature erythrocytes can be isolated from formalinfixed larvae, even as sorted from plankton, and prepared for cytological and cytogenetic study and for blood cell counts. Knowledge gained from the study of erythrocytes from larval teleosts can be important in assessing the normality and health of these early‐life stages of fish in either laboratory assays or field studies. The method described is applicable to other fish species, even after years of storage in formalin fixative.
Effects of temperature, oxygen and carbon dioxide on osmotic fragility of carp, Cyprinus carpio L., erythrocytes
Authors: Martinez I. , Viscor G. , Palomeque J.
Published: January 2006

The in vitro effects of gases and temperature on the osmotic fragility of carp erythrocytes were studied. At the three different temperatures analyzed (5, 11 and 20°C) there was no noticeable modification in erythrocyte membrane osmotic resistance. Osmotic fragility of red blood cells was altered by CO2 and air treatment, as compared to the standard procedure. This suggests the need to take into account a possible moderate hypoxia that develops in the routine procedure of nucleated erythrocyte osmotic fragility tests.
An anomalous specimen of Rhamdia guatemalensis (Günther, 1864)
Authors: Cabrera J. , Martinez G. , Alforo A.
Published: January 2006

In March of 1984 an immature Rhamida guatemalensis(Günther, 1864) lacking the right pectoral fin (Fig. 1) was captured in the Sangregado sector, Arenal Dam, Guanacaste, Costa Rica (10°28′ N, 84°46′W) The body colouration and morphometric characteristics were as described for this species (Bussing 1966; Zúñga, 1980). X‐ray examination revealed the absence of the radial bones and the fin rays of the right peoctoral fin. External examination of the tegument of this region showed no scars or evidence of accidental loss of the appendage, indicating that the fin had never developed.

Morphometric data from this abnormal specimen are: total length, 14.25 cm, standard length, 11.98cm; maximum height of body, 22.35 cm; maximum width of body, 2.40 cm, caudal peduncle width, 1.27 cm; head length, 3.00cm.
Estimating the carbohydrate reserves in fish
Authors: Black D. , Malcolm Love R.
Published: January 2006

The post‐mortem pH value of the muscle of cod, Gadus morhua L., is shown to be a valid indicator of the muscle glycogen level after rapid capture, stunning and rapid sampling (a level thought to be little different from that current before capture). Good correlations between initial glycogen values and post‐mortem pH were obtained in fish of a wide range of nutritional states comprising fed, starved for different periods, and refed on different diets after starvation. Inconsistencies in results published in the literature are attributed to variations in the initial glycogen values as measured, which in turn stem from the fish struggling on capture, differing degrees of which reduce muscle glycogen by different amounts but probably do not affect the post‐mortem pH. Variations in the time taken to sample the glycogen would also affect the results.
Morphometric, meristic character and electrophoretic analyses of two Irish populations of twaite shad, Alosa fallax (Lacépède)
Authors: O'Maoileidigh N. , Cawdery S. , Bracken J. J. , Ferguson A.
Published: January 2006

Since 1911 a rare lacustrine form of twaite shad, Alosa fallax killarnensis Regan (1916), has been known to occur in the Killarney Lakes. During the summers of 1985 and 1986 a gill netting programme in Lough Leane for brown trout, Salmo trutta L., yielded 32 shad (1985) and 64 shad (1986) as a by‐catch. These fish were deep frozen and compared with a sample of 59 marine twaite shad, taken on rod and line from St Mullin's, Co. Carlow, which had entered the River Barrow to spawn.

Morphometric, meristic and electrophoretic character analyses were carried out on the two populations. The three analyses, particularly the isoelectric focusing, confirmed a high degree of genetic similarity. The two major differences found were the dwarfed size of the Killarney shad and the increased numbers of gill rakers carried on the first branchial arch. The merits and demerits of assigning the term subspecies to the Killarney shad are discussed in the light of the available evidence produced.
Daily growth increments in otoliths of milkfish, Chanos chanos (Forsskål), larvae
Authors: Tzeng W.‐N. , Yu S.‐Y.
Published: January 2006

The formation of daily growth increments of otoliths was studied in the reared larvae of milkfish. The first growth increment was formed during the yolk–sac reabsorption period c.2 days after hatching, and increment formation continued on a daily schedule regardless of growth rate. The initial incremental zone was of amorphous structure, and the subsequent incremental zone was of needle–shaped crystalline structure; the former structure was formed in the yolk–sac reabsorption period of the larva and the latter in the exogenous feeding period. Accordingly, ageing of milkfish larvae is possible by counting growth increments, and timings within the developmental stage of the larvae can be understood by examining the otolith microstructure.
Variation in the degree of silvering of wild coho salmon, Oncorhynchus kisutch, smolts migrating seaward from Carnation Creek, British Columbia
Authors: McMahon T. E. , Hartman G. F.
Published: January 2006

Degree of silvering (colouration) is often used as an index of the degree of smoltification in salmonids. To judge the reliability of silvering as an indicator of migratory readiness, we examined the silvering of wild coho salmon, Oncorhynchus kisutch, smolts upon entry into the Carnation Creek, British Columbia, estuary. Silvering of migrants was greater in larger fish and increased over the course of the migratory period. Photoperiod appeared to account for most of the observed increase in silvering over time; increased silvering was not correlated with temperature or lunar phase. Overall, 50% of seaward migrants were completely silvered, 45% were in a transitional phase, and 5% still retained colouration characteristics of parr. Colouration thus appears to have limited utility as a reliable indicator of migratory readiness. Our findings suggest that estuarine residence is important for completion of parr‐smolt transformation and that acclimation of hatchery smolts in brackish water prior to sea water entry may enhance their survival.
Time‐course changes of plasma lipid levels and lipoprotein pattern after feeding in cultured sea bass, Dicentrarchus labrax L.
Authors: Santulli A. , Curatolo A. , Modica A. , D'Amelio V.
Published: January 2006

Results of a study of plasma lipids levels and lipoprotein pattern modification during digestion in sea bass indicate that, after feeding, non‐esterified fatty acids are rapidly delivered in plasma, while triglycerides reach a maximum concentration only 24 h later. The time‐course change of the lipoprotein pattern shows a relationship between their concentration and the lipid class carried.
Results of accelerated rearing of Atlantic salmon, Salmo salar L., smolts by use of warm waste water
Authors: Kazakov R. V. , Christoforov O. L. , Murza I. G. , Ilyenkova S. A. , Titov S. F.
Published: January 2006

The results of rearing salmon smolts, using warm water in winter time, are presented. Fishes weighing 25–50 g were released in spring time at the age of about 1 year, while smaller fishes were left to grow in ponds for release at age 2 years. As a result of warm‐water wintering of fingerlings, the yield to the fishery was at least doubled, while there was no decrease in fish size, nor in gamete quality. Three thousand to 5000 spawners entered the Narova River (Baltic Sea) per annum and the trend is to exceed these totals.
Seasonal changes in the size and composition of the fish yield from reefs around Apo Island, Central Philippines, with notes on methods of yield estimation
Authors: Bellwood D. R.
Published: January 2006

Fish yields from Apo Island, Central Philippines were assessed based on detailed quantitative analyses of fish landings, with specific reference to seasonal changes in the size and nature of the yield in terms of familial composition and degree of reef association of contributing species. The total estimated annual yield is 24‐861 km−2 year−1 (±12.75, 95% C.I.)‐ Of the 39 families harvested, yields are dominated throughout the year by two, the Carangidae (40%) and the Acanthuridae (23.6%). The yield is likewise consistently dominated by two specific groups: reef‐associated, 39.1%, and reef planktivores, 23.1%. Reef species comprise only 17‐1%. Seasonal differences in yields were only detected in the Carangidae and the reef‐associated species group. Apo Island reefs appear to be highly productive. Possible reasons for this are discussed. The variety of methods used for estimating reef fish yields, however, make comparisons difficult. Standardized procedures are therefore suggested.
The influence of maternal length and age on the size and weight of the eggs and the relative fecundity of the haddock, Melanogrammus aeglefinus, in British waters
Authors: Hislop J. R. G.
Published: January 2006

The diameter and dry weight of the eggs of haddock, Melanogrammus aeglefinus, are positively correlated with fish length. The correlations are largely due to the fact that many of the smaller fish that were sampled were 2 years old, and the eggs of these young haddock, which can be regarded as precocious spawners, are significantly smaller and lighter than those of older fish. The relative fecundity of 2–year–old haddock (274 eggs g−1) is also lower than that of the other age classes (493 eggs g−1); this has important implications for the estimation of egg production from female spawning stock biomass. It is pointed out that in some years precocious spawners represent a large component of the North Sea haddock spawning stock. When the annual egg production of this stock is calculated, it may be appropriate to apply a weighting factor to the number of eggs contributed by the 2–year–olds, on the assumption that the small eggs of these fish produce larvae that are less viable than those of older haddock.
The effects of aluminium and low pH on chloride fluxes in the brown trout, Salmo trutta L.
Authors: Battram J. C.
Published: January 2006

Juvenile brown trout acclimated to fresh water of 0‐3 mEq 1‐1 calcium and neutral pH were exposed to pH 4‐0 for 2 h at 10°C. Chloride influx was reduced by 66% and a 144% stimulation of chloride efflux recorded. The effect on chloride influx was reversed by returning the medium pH to 7‐0, restoring the influx rate to 89% of its former value.

After a control period without aluminium, chloride influx and efflux were measured at 10°C at pH 7‐0 in the presence of aluminium at a final concentration of 6‐5 μM. The experiment was repeated at pH 5‐5, and subsequently pH 4‐0. At pH 7‐0, aluminium stimulated chloride efflux by 105% but influx was not affected. At pH 4‐0, efflux was not affected but influx reduced to 55%. At pH 5‐5, influx was reduced by 62% and efflux was increased by 67‐5%.

Thus, the effects of aluminium on chloride fluxes are shown to be separate from those of low pH alone, and the presence of aluminium in natural waters may have a detrimental effect on chloride balance which is most evident at pH 5‐5.
The effects of a change in the growth rate of roach, Rutilus rutilus (L.), on the biology of the fish tapeworm Ligula intestinalis (L.)
Authors: Wyatt R. J. , Kennedy C. R.
Published: January 2006

Investigations into the biology of the roach and the pathogenic tapeworm Ligula intestinalis (L.) populations at Slapton Ley, Devon were carried out between October 1982 and December 1984. Data collected from the lake since 1977 have also been re‐analysed to determine how the dramatic improvement in the individual growth rate of the roach over this period may have affected the growth, maturation and life‐cycle of Ligula. Only the very young roach at this site become infected, so it was possible to follow cohorts of plerocercoids of similar age through each roach year class. Results for the 1978 and 1983 year classes are presented in detail. The roach grew extremely rapidly from May to August in each year, resulting in a pronounced cyclical pattern of changes in the condition of the roach, with the lowest condition occurring in late winter and spring. The yearly increase in the roach growth rate was accompanied by an increase in plerocercoid growth rate in the 0 + roach, but not in the 1 + roach. The growth rate of the plerocercoids was very high compared to that at other sites. It is usual for the parasite index (PI) of Ligula‐infected fish to be high and to increase throughout their first few years of life. At Slapton, however, a lack of multiple infections has prevented high PIs from occurring, and in recent years the growth rate of the roach has been so high that the plerocercoids were unable to maintain a high weight relative to the fish, and the highest PIs occurred in the 0 + roach throughout late winter and spring. In recent year classes, therefore, the maximum PIs and highest pathogenicities coincided with the period of lowest condition in the 0+ roach. Observations of both caged and natural populations of 0+ roach over winter showed that a significant loss of roach containing the larger plerocercoids occurred from the population. In vitro cultivation of Ligula plerocercoids showed that they were capable of maturation at weights of 0.5 g, and only 6 months after having infected the roach. The increase of the growth rate of the plerocercoids in the 0+ roach has therefore resulted in a greater proportion of these plerocercoids being capable of infecting the definitive host. As a result of the increase in individual growth rate of the roach at Slapton, the potential for Ligula transmission, as measured in terms of both their pathogenicity and maturity, has shifted from the 1 + to the 0+ roach.
Cohort sampling, anaesthesia and stocking‐density effects on plasma cortisol, thyroid hormone, metabolite and ion levels in rainbow trout, Salmo gairdneri Richardson
Authors: Laidley C. W. , Leatherland J. F.
Published: January 2006

The effect of serial removal of fish from aquaria, anaesthesia and stocking density on plasma cortisol, thyroid hormone, metabolite and ion levels was examined in rainbow trout, Salmo gairdneri, to determine the consequences of normal handling and maintenance procedures on the activity of the pituitary‐adrenal and pituitary‐thyroid axes in the species.

The capture and handling associated with serial removal of fish from an aquarium resulted in a rapid elevation of plasma cortisol concentrations and a slower rise in plasma glucose, Mg2+ and Na+ concentrations; plasma K.+ levels showed a transient fall shortly after commencing the sampling, followed by a significant increase.

A lethal concentration of 3‐aminobenzoic acid ethyl ester (MS 222) of 125 mgl−1 (but not a sublethal concentration of 62.5 ng 1−1) prevented the capture stressor‐associated changes in most of the measured parameters, including plasma cortisol levels, although plasma protein and ion concentrations were elevated in fish sampled after MS 222‐anaesthesia.

Stocking densities from 1 to 64 fish 80 1−1 aquarium did not appear to effect changes in the measured parameters, except for plasma T3/T4 ratios which decreased with increasing stocking density. The exception was found in fish which were stocked in pairs: one member of each pair had a markedly elevated plasma cortisol level and there was a high incidence of mortality, probably related to aggressive social interaction.
The influence of calcium on aluminium‐induced changes in the growth rate and mortality of brown trout, Salmo trutta L.
Authors: Sadler K. , Lynam S.
Published: January 2006

Yearling brown trout, Salmo trutta L., were maintained in a synthetic medium at pH 5.2 with various concentrations of calcium (4–400 μumol l−1) and aluminium (0–3 μumol l−1). In general, higher mortality and lower growth rates were found at higher aluminium concentrations, with these effects being reduced at high ambient calcium. Aluminium toxicity was greater in an experiment conducted in February–March than in an experiment conducted in October–December; this could be due to a seasonal variation in tolerance of the fish. Aluminium exposure resulted in an initial period of weight loss and high mortality followed by some recovery over the 6‐week period of the experiments. In the first experiment, as in previously reported work, adaptation was incomplete in that aluminium‐induced growth rate reduction was still evident to the end of the test. In the second experiment, however, no significant effect of aluminium treatment on growth was found during weeks 4 to 6 of the exposure period.
Changes in condition and maturation of the Oreochromis niloticus L. population of Ferguson's Gulf, Lake Turkana, Kenya
Authors: Stewart K. M.
Published: January 2006

The condition and maturation of the Oreochromis niloticus population of Ferguson's Gulf, Lake Turkana was assessed in light of the declining lake level and compared with similar data taken at the high lake level period 10 years ago. Results show a dramatically lower length/weight relationship and an earlier length at maturity for the 1980s population. A defined breeding period was seen for the 1980s population, unlike in the 1970s, perhaps in response to stressful conditions. The reduction in area of the Ferguson's Gulf breeding/nursery grounds is suggested as the major factor contributing to stress in the O. niloticus population, and it is suggested that measures be taken to protect what is left of these breeding/nursery areas.
Trophic ecology of striped bass, Morone saxatilis, in a freshwater reservoir (Lake Texoma, U.S.A.)
Authors: Matthews W. J. , Hill L. G. , Edds D. R. , Hoover J. J. , Heger T. G.
Published: January 2006

Many vertebrate predators consume a wide variety of prey types, depending upon availability and vulnerability. In contrast, striped bass, Morone saxatilis, that have been introduced to Lake Texoma (Oklahoma‐Texas, U.S.A.) use a very limited array of fish (mostly clupeids of the genus Dorosoma) as prey. As a large, mobile predator, M. saxatilis should be capable of capturing and consuming numerous other species of fish that are available in the reservoir. However, examination of 1845 stomachs year‐around over 5 years showed that the only marked ‘switching’ among prey was from Dorosoma to a diet including a high percentage of insects during spring–early summer, ignoring most other fish taxa that could have served as food. Even under essentially starvation conditions in late summer of years with scarce Dorosoma, M. saxatilis in Lake Texoma did not switch to other available fish as prey. Patterns of predation by M. saxatilis are trenchantly different from place to place: very narrow prey selectivity even under starvation conditions has been reported once previously for the species in a freshwater reservoir, but in its native marine and estuarine environment and in some other reservoirs the species is more catholic in its use of prey. Why this large predator shows fidelity in some environments to particular prey, even to the extent of starvation, remains an enigma.
Morphological adaptations of the digestive tract of tropical cyprinids and cichlids to diet
Authors: Hofer R.
Published: January 2006

Eight cyprinids with four different feeding habits fall into two distinct groups according to morphological adaptations of the intestine: (i) carnivorous and omnivorous cyprinids with large gut diameter and large mucosal surface which decreases from the foregut to the hindgut; (ii) benthivorous and phytoplanktivorous cyprinids with small gut diameter and small mucosal surface which is more or less uniformly built along the intestine, although relative gut length may vary considerably (1.45–6.10). Although the intestine of phytoplanktivorous cyprinids is extremely elongated, it appears less adapted for processing a refractory diet than that of cichlids with similar feeding habits.
Vertebral defects in fourhorn sculpin, Myoxocephalus quadricornis L., exposed to heavy metal pollution in the Gulf of Bothnia
Authors: Bengtsson Å. , Bengtsson B. E. , Lithner G.
Published: January 2006

Vertebral defects in adult fourhorn sculpin were used to trace heavy metal pollution in the Gulf of Bothnia (Baltic Sea). From 1978 to 1984 a total of 9789 specimens from 22 localities were X‐rayed and analysed for vertebral deformities, e.g., scoliosis, deformation and/or dislocation of individual vertebrae, etc. The frequency of fish with vertebral defects ranged between 4.3 and 39.7%, the highest frequencies being found in the vicinity of a metal ore smeltery (Rönnskärsverken) emitting heavy metals and arsenic. The possible influence of genetic factors, migration, sex, size, age and parasitic infections on the results are discussed and evaluated.
The effect of extreme northerly climatic conditions on the life history of the minnow, Phoxinus phoxinus (L.)
Authors: Mills C. A.
Published: January 2006

Over its exceptionally wide geographical range the minnow displays a remarkable variability in its life history. In southern England many fish mature after one year and few fish survive to their third birthday. Very few fish spawned for more than one season but a 65‐mm female is estimated to spawn up to 3172 eggs over the extended spawning season. In the River Utsjoki in Finnish Lapland maturity was strongly size‐dependent and delayed until the fish reached 5, 6 or even 7 years of age, with a maximum age of 13 years at a length of only 75 mm. Unlike some other small‐sized species in unproductive environments, individual females continued to spawn successive clutches of eggs though over a much shorter spawning season. The maximum estimated egg production was 824 for a 65‐mm fish. Temperature had a strong direct or indirect effect on growth, with significantly lower growth increments in cold summers. At a second Arctic site in eastern Lapland growth rates were higher and maturity earlier, yet clutch size was greatly reduced with a seasonal fecundity estimate of only 314. There were only small differences in size of eggs or larvae between the populations. Evidence from other species indicates that most of the observed changes over the range of the minnow are phenotypic responses to the contrasting environments. However, the different strategies displayed at the two Arctic sites could represent the results of selection for differences in pre‐ and post‐reproductive survival.
Morphological effects of mercury exposure on windowpane flounder gills as observed by scanning electron microscopy
Authors: Pereira J. J.
Published: January 2006

Windowpane flounder, Scophthalmus aquosus Mitchill, were exposed for 60 days to 5 or 10 μg 1−1 mercury and gill samples were examined by scanning electron microscopy. The response of the gill epithelium was different at the two levels of mercury exposure. The number of chloride cell apical pits and gill filaments bearing ‘cratered’ epithelial cells increased at the 5‐μg 1−1 level and decreased at the higher exposure level.

Focal swellings demonstrated a dose‐dependent relationship, their numbers being greatest at the higher exposure level. Marked fragmentation of pavement cell microridge patterns and swelling of the respiratory epithelial cells was evident at the 10‐μg 1−1 exposure level.
Chromosome polymorphism in farm fry stocks of Atlantic salmon from Asturias
Authors: García‐Vazquez E. , Linde A. R. , Blanco G. , Sanchez J. A. , Vázquez E. , Rubio J.
Published: January 2006

The karyotypes of two samples of Salmo salar fry used to repopulate the rivers of Asturias (northern Spain) during 1986 were analysed: chromosomal polymorphism differed significantly between them. The need to repopulate with non‐heterogeneous stocks is suggested.
The reproductive success of pike, Esox lucius: aspects of fecundity, egg density and survival
Authors: Wright R. M. , Shoesmith E. A.
Published: January 2006

Power‐law relationships have been estimated between fecundity and fish length, weight and age for pike from two gravel pit lakes (Main Lake and St Peter's Lake) in Buckinghamshire, England. Relative fecundity, estimated at 17.6 eggs g−1 for Main Lake pike and 19.4 g−1 for St Peter's Lake pike, did not differ significantly between the lakes. Population fecundity for the Main Lake was estimated at 10.6 million eggs and 6.4 million eggs in 1986 and 1987, respectively.

Experimental work involving samples of eggs from 18 artificially fertilized Main Lake female pike showed a significant relationship between egg diameter and female length, and a significant difference between mean egg diameters for 41‐cm and 101‐cm females. No significant relationships were found between mean egg size and mean fry size, nor between fry length and adult length. Mean size differences between newly hatched, 18‐day‐old and 41‐day‐old fry from the 41‐cm and 101‐cm females were not significant.

Samples of eggs taken at 2‐day intervals from 6 April to 5 May in a pike spawning area of the Main Lake revealed clumped distributions of eggs, with average egg densities ranging from 1 to 47 eggs per 0.071 m2 (14–671 m 2) on sand and silt substrata. The maximum egg density of 51 per 0.071 m2 (729 m−2) was found on flooded grass. The stages of development of the eggs were identified over the sampling period. Survival from stage 1 to fry was estimated at 3–6%. Egg losses were estimated at 9–10% day−1.

Egg survival experiments gave overall hatching success rates of 11 % on sand/silt compared with 2.5% on aquatic plants (1986), and 18.9% on undisturbed sand/silt compared with 7.9% on disturbed sand/silt (1987). The effect of siltation on egg hatching is discussed.
The feeding ecology of the Central American cichlid Cichlasoma urophthalmus (Gunther)
Authors: Martinez‐Palacios C. A. , Ross L. G.
Published: January 2006

The feeding habits of the cichlid Cichlasoma urophthalmus were studied in a brackish‐water lagoon in Yucatan Peninsula, Mexico, from spring 1985 to spring 1986. The strong mandibular, maxillary and pharyngeal teeth, and the short intestine strongly suggest that C. urophthalmus is primarily a carnivore. Subsequent gut contents analysis revealed that this species feeds principally on invertebrates throughout the year and that there were few differences between the five seasons studied. The algal material found in some stomachs may be consumed as a consequence of predation on small invertebrates, but the feeding structures and short intestine makes this species unable to digest vegetable materials efficiently. Differences with other cichlids used in aquaculture are discussed.
Recruitment patterns and trophic relationships of fish in Sulaibikhat Bay, Kuwait
Authors: Wright J. M.
Published: January 2006

The juveniles of nine species of fish constitute over 96% of the fish community captured in Sulaibikhat Bay, a shallow, semi‐enclosed bay located at the northern end of the Persian Gulf. These juveniles show four patterns of recruitment to the bay, including recruitment in early spring, in late spring, in summer and all year round. Stomach content analysis allowed five groups of diets to be distinguished. Within these five groups, competition for food resources was probable, particularly in the spring and autumn months.
The ontogeny of the alimentary tract of coregonid larvae: normal development
Authors: Loewe H. , Eckmann R.
Published: January 2006

The development of the alimentary tract in larvae of Coregonus fera fed with Anemia nauplii has been examined histologically from the 4th to the 24th day after hatching.

Buccal cavity and oesophagus are nearly completely developed before the start of feeding. The stomach exists only as an ‘anlage’, but starts to store food during the study period. The intestinal absorptive cells are stuffed with fat vacuoles between the 7th and 13th day after the start of feeding. During this time the rectal absorptive cells contain one large supranuclear body consisting of protein. The occurrence of large vacuoles in the intestinal and rectal absorptive cells may be caused by a partial non‐functioning of the larval digestion; after two weeks of feeding this restriction seems to be overcome.
A combined radio and acoustic transmitter for fixing direction and range of freshwater fish (RAFIX)
Authors: Armstrong J. D. , Lucas M. , French J. , Vera L. , Priede I. G.
Published: January 2006

A mobile system incorporating a novel transmitter for tracking the position of freshwater fish is described. The transmitter emits both acoustic and radio pulses simultaneously to allow a range estimate from the delay between signals arriving at a receiver station. Results of field trials are presented and the usefulness of the system is discussed in relation to other tracking methods.
Interaction of salinity and temperature as a mechanism for spatial separation of three co‐existing species of Ambassidae (Cuvier) (Teleostei) in estuaries on the south‐east coast of Africa
Authors: Martin T. J.
Published: January 2006

Ambassidae are represented in South African estuaries by three species which are very similar in external morphology, feeding ecology, alimentary system and distribution. The co‐existence and spatial separation of these species of Ambassis in the estuaries of southern Africa can be explained by the tolerance of each to salinity and temperature. Investigations of the temperature tolerance ranges of the three species suggest that the osmoregulatory capability of Ambassis productus in reduced salinities (<10%) increases while that of A. gymnocephalus decreases sharply in salinities below 20%. A. natalensis, which is endemic to the south‐east coast of Africa, is adapted to a wide range of estuarine conditions. Interaction between salinity and temperature tolerances on the limits within which Ambassis spp. survive is significant with regard to the distribution of the three species in estuaries. Catch data showed that A. productus is restricted to areas of low salinity and seasonal low temperature (upper reaches of estuaries), A. gynmocephalus to high salinities >25% (estuary mouths) and A. natalensis to intermediate salinities associated with the middle reaches of estuaries.
The oxygen requirements of a polluted estuary for the establishment of a migratory salmon, Salmo salar L., population
Authors: Curran J. C. , Henderson A. R.
Published: January 2006

The return of salmon in 1978 to the River Gryfe, a tributary of the Clyde estuary, and to the River Clyde itself in 1983, provides the opportunity for the derivation of the threshold oxygen requirements within the estuary for the successful migration of both adults and smolts.
Disused docks as habitats for estuarine fish: a case study of Preston dock
Authors: Conlan K. , Hendry K. , White K. N. , Hawkins S. J.
Published: January 2006

A netting and hydrographic study of Preston dock was undertaken between May 1987 and April 1988. Fish populations were assessed using Lundgren monofilament multimesh gillnets. The dock was a low‐salinity environment regularly replenished with estuarine water on spring tides. Influxes of higher‐salinity water caused intermittent saline wedges in the deeper regions. The dock water was poorly mixed in the summer, resulting in bottom water anoxia. The water was eutrophic, and blue‐green algal blooms were common for much of the year.

Fourteen freshwater, marine‐estuarine, anadromous and catadromous species were present in the dock. No seasonal patterns in diversity were apparent, due to the dominance of the herring population. Changes in species composition and abundance seem to relate to seasonal migratory patterns and, in the case of the freshwater fish, estuarine salinity, rather than to water quality.

The suitablity of docks for sampling estuarine fish assemblages is discussed.