bluuebunny/crossref_metadata_2025 huggingface dataset:
Interspecific interactions and diet of sympatric juvenile brook charr, Salvelinus fontinalis, and adult ninespine sticklebacks, Pungitius pungitius
Authors: Gaudreault A. , Miller T. , Montgomery W. L. , FitzGerald G. J.
Published: January 2006

Breeding male ninespine sticklebacks, Pungilius pungitius, are highly aggressive toward juvenile brook charr. Salvelinus fontinalis, in the Matamek River, Québec. Field observations revealed that such aggression was always initiated by the sticklebacks and only if the charr approached their nests or free‐swimming fry. There was considerable overlap in diet in August, but not in June and July, suggesting competition for food is possible under some circumstances.

In laboratory stream tanks, we compared frequency of intraspecific and interspecific aggression of single and mixed species groups over a range of densities. There was no simple relationship between aggression and density for either species, although significant differences in aggression occurred among fish in some of the different density conditions.
Role of diet and experience in the development of feeding behaviour in largemouth bass, Micropterus salmoides
Authors: Colgan P. W. , Brown J. A. , Orsatti S. D.
Published: January 2006

Two groups of largemouth bass, Micropterus salmoides, were reared in the laboratory. One group was reared on an artificial, passive diet (frozen brine shrimp) whereas the second was reared on a natural, active diet (cultured zooplankton). Observations on the development of feeding behaviour indicated that the motor patterns and duration (number of weeks in the behavioural repertoire) of the feeding acts did not differ between fry reared on the two diets. While feeding on their respective diets, natural‐diet fry performed significantly more orientations and bites, the two major early feeding acts, than did the artificial‐diet fry. When tested with live fish prey, fish reared on the natural diet performed fewer orientations and strikes and captured more prey per fry than did the artificial‐diet fry. Natural‐diet fry had a significantly better net efficiency (captures minus strikes minus orientations) than did artificial‐diet fry. Diet, experience, and length (T.L.) of fry affected their predator efficiency significantly. We argue that providing hatchery‐reared bass fry with an opportunity to prey on live forage fish once or twice before their release would enhance their survival and eventual recruitment into natural populations.
Experimental infection of American winter flounder (Pseudopleuronectes americanus) with Glugea stephani (Microsporida)
Authors: Cali A. , Takvorian P. M. , Ziskowski J. J. , Sawyer T. K.
Published: January 2006

Young‐of‐the‐year Pseudopleuronectes americanus were captured in Sandy Hook Bay, New Jersey and maintained in aquaria at 16–19° C for 115 days in 1982 and 127 days in 1983. Half of them were experimentally exposed to Glugea stephani and the others were sham exposed. During the course of these experiments fish from both groups died as a result of G. stephani infection, demonstrating Glwgea‐induced mortality in this species. Infections were found in both control and experimentally exposed fish. Mortality of Glwgea‐infected fish in the exposed group was 63% while that in the controls was 28.5%.
Quantitative and qualitative analysis of spawning behaviour of Heteropneustes fossilis (Bloch.) (Siluridae) in laboratory aquaria
Authors: Roy S. , Pal B. C.
Published: January 2006

Induced breeding of Heteropneustes fossilis (Bloch.) was studied in laboratory aquaria. Quantitative and qualitative data on pre‐mating, mating, and post‐mating behaviour and related parameters were recorded. Among the pairs examined, 83% spawned successfully. Mating behaviour started between 6 and 15 h after administration of pituitary hormones. The number of enfoldings varied from 25 to 350. Over 93% of the released eggs hatched within 21–24 h at temperature 24–31°C.
Emission rate of amino acids and ammonia and their role in olfactory preference behaviour of juvenile Arctic charr, Salvelinus alpinus (L.)
Authors: Olsén K. H.
Published: January 2006

The behaviour of juvenile Arctic charr, Salvelinus alpinus (L.), to an abrupt concentration step of L‐amino acids, L‐alanine and ammonium chloride was studied by fluviarium technique. The emission rates of these substances were studied. Juvenile Arctic charr emit 8.0 × 10−4 mol total ammonia‐N kg−1 h−1 and 3.3 × I0−5 mol amino acids kg−1 h−1. In behaviour tests the charr avoided 5.6x 10−6and 5.6 × 10−7 M ammonium chloride. The 17 L‐amino acid mixture, ranked as observed in the analysis of emission, was avoided at 4.6 × 10−7 M, while 100 times dilution of this value gave neither avoidance nor attraction. The charr avoided L‐alanine tested alone at the concentration of 4.6 × 10 −7 M. Anosmic charr showed neither avoidance nor attraction to the mixture of 17 amino acids tested at 4.6 × 10−7 M. The results indicate that ammonia as well as emitted amino acids are not responsible for the olfactory mediated attraction to conspecific odour shown earlier in Arctic charr. On the contrary, these substances may have a negative effect by reducing the strength of attraction.
Protogynous hermaphroditism in the slinger, Chrysoblephus puniceus (Gilchrist & Thompson, 1908) (Teleosteir:Sparidae)
Authors: Garratt P. A.
Published: January 2006

Hermaphroditism in the marine fishes is well documented, especially in the family Sparidae in which at least 35 species have been reported. Within this family sexuality ranges from gonochorism, through rudimentary, protogynous and protandrous hermaphroditism, to what is thought to be a single functional hermaphrodite.

A biological study of the economically valued Chrysoblephus puniceus revealed marked differences in the size of male and female fish, suggesting that this sparid undergoes sex reversal. Histology of gonads macroscopically classified as ‘female’, ‘male’ and ‘hermaphrodite’ were analysed. Degenerating pre‐vitellogenic oocytes in the ovarian sections of hermaphroditic gonads confirm that C puniceus is a protogynous hermaphrodite.
Biology of the acid‐tolerant fish species Umbra pygmaea (De Kay, 1842)
Authors: Dederen L. H. T. , Leuven R. S. E. W. , Wendelaar S. E. , Oyen F. G. F.
Published: January 2006

In The Netherlands, the mudminnow Umbra pygmaea mainly occurs in water bodies with a pH ranging from 3–5 to 4–0, an alkalinity less than 0.1 meq 1−1 and a calcium content below 100 μmol 1−1. The abundance of mudminnows is inversely related to the pH and the presence of predatory fish species. Experimental studies show that If. pygmaea is extremely acid‐tolerant. Exposure to media with pH values ranging from 4.0 to 7.0 did not cause mortality or significant changes in blood plasma osmolarity and haematocrit. At pH 3.0 no mortality was recorded although a strong decrease in the plasma osmolarity was observed. Exposure to pH 2.8 and calcium concentrations of 100 or 500 μ mol 1−1 for 10 days caused 70% and 40% mortality respectively. The growth, reproduction and feeding of mudminnows are described. Age‐growth and length‐age relationships were calculated. Gonadal development started between September and January. The highest Gonado Somatic Index was recorded in spring. Spawning occurred from April to May. Fecundity of a sample of females was assessed. Nematocera provided the main item of diet of U. pygmaea; the microfauna ingested was dominated by Cladocera. The adaptations of mudminnows to acid environments are discussed.
Activity and inhibition of carbonic anhydrase in Amia calva, a bimodal‐breathing holostean fish
Authors: Heming T. A. , Watson T. A.
Published: January 2006

Carbonic anhydrase (CA) activity was measured in the respiratory swimbladder, gill filaments and red blood cells of the primitive air‐breathing holostean fish, the bowfin, Amia calva. The activity of swimbladder CA, relative to gill and red cell CA activities, was within the range reported previously for unimodally‐breathing fishes and was comparable to the CA activities reported for the air‐breathing organs of teleosts. It is unlikely that carbon dioxide excretion across the bowfin swimbladder is limited to the uncatalyzed rate of HCO3‐dehydration. Bowfin blood plasma lacked any endogenous inhibitor(s) of CA, in contrast with information on teleostean fishes. This absence may have interesting phylogenetic implications and may offer some potential for investigating the nature and physiological role of plasma CA inhibitors.
Comparison of osmotic fragility of red blood cells of freshwater‐adapted and seawater‐adapted rainbow trout, Salmo gairdneri Richardson
Authors: Hughes G. M. , Martinez I. , Boeuf G.
Published: January 2006

The osmotic fragilities of erythrocytes in blood sampled from rainbow trout adapted to sea water or fresh water did not differ significantly although blood chloride concentration and osmolarity were lower in the freshwater group.
The leucocytes of the elasmobranch Scyliorhinus canicula L.—a morphological study
Authors: Parish N. , Wrathmell A. , Hart S. , Harris J. E.
Published: January 2006

The leucocytes of the peripheral blood of the elasmobranch Scyliorhinus canicula L. were examined by light, transmission and scanning electron microscopy and histochemistry. Seven distinct leucocytes were identified including lymphocytes, thrombocytes, monocytes and granulocytes. The major characteristics of these cells and their relative distribution is described.
Ontogenic development of surface ornamentation in the scales o fHemichromis bimaculatus (Cichlidae)
Authors: Sire J.‐Y.
Published: January 2006

The scale surface of laboratory‐raised Hemichromis bimaculatus selected from five age classes contains two regions, each characterized by a distinct ornamentation. The boundary between them corresponds to the anterior limit of the epidermis that covers the free region of the scale. In the overlapped region, the circuit and denticles are oriented toward the focus of the scale and form a classical pattern of ornamentation. During growth, the size of circuli and denticles does not change after they are formed. They appear stable at the species level and could thus be used in systematics. The ornamentation of the free region of the scale is composed of rounded tubercles, elongated ridges and sometimes ctenii. These structures appear long after the scales have been formed and thereafter grow and thicken throughout the life of the fish. The ontogenetic changes suggest that these characters should be used cautiously for taxonomic studies. The ridges of the scales of wild specimens are distinctly organized in a pattern that is lacking in laboratory specimens. Mechanical and hydrodynamical implications of the ornamentation are discussed.
Observations on the size, dry weight and energy content of the eggs of some demersal fish species from British marine waters
Authors: Hislop J. R. G. , Bell M. A.
Published: January 2006

The diameters, dry weights and calorific value of the eggs of seven gadoid species (cod, Gadus morhua, haddock, Melanogrammus aeglefinus, whiting, Merlangius merlangus, Norway pout, Trisopterus esmarkii, lythe. Pollachius pollachius, saithe, P. virens, ling. Molva molva) and one pleuronectid (plaice, Pleuronectes platessa) were measured. Ling eggs contain an oil globule; the eggs of the other species do not.

Preservation in formaldehyde solution caused a small (<4%) reduction in egg diameter but a large (15–30%) reduction in dry weight. There was no significant difference between the dry weights of unpreserved eggs weighed after (a) oven‐drying at 60° C or (b) freeze‐drying. Equations relating the dry weight of unpreserved eggs to unpreserved diameter and to preserved diameter are given for six species, and general equations that may apply to all North Sea gadoids whose eggs lack an oil globule are calculated. The calorific values of the dried, unpreserved eggs of all species except ling were similar (mean 23.19 kJ g−1, S.D. 1.50) but the value for ling was higher (mean 26.92 kJ g−1, S.D. 2.29). The estimated energy content (kJ 1000 eggs−1) of eggs of each species are tabulated.
Predation risk and reduced foraging activity in fish: experiments with parasitized and non‐parasitized three‐spined sticklebacks, Gasterosteus aculeatus L.
Authors: Giles N.
Published: January 2006

After varying periods of food deprivation the foraging behaviour of parasitized and non‐parasitized sticklebacks was measured in both undisturbed and recently frightened fish. Parasitized sticklebacks forage significantly more actively and recover more quickly after a frightening stimulus than do control fish. They also react more quickly to food deprivation than do uninfected control fish. Seventy‐two hours without food is sufficient to suppress the fright response in parasitized fish, and causes them to forage at the same rate as when undisturbed. Non‐infected controls failed to forage successfully after a frightening stimulus, even when they had been without food for 96 h. Frightening stimuli can affect profoundly the normal foraging behaviour of hungry fish.
Agonistic behaviour and growth in the European eel, Anguilla anguilla L., in relation to warm‐water aquaculture*
Authors: Knights B.
Published: January 2006

Agonistic behaviours were studied at high densities and in tournament experiments with pairs of small eels with and without prior isolation. Although innate differences probably exist, eels appear to learn their average positions in diffuse social and size hierarchies from the outcome of repeated agonistic encounters. Dominance or avoidance were most marked when the larger fingerling eels were about 1.5 times the body weight of the smaller. Larger eels tended to attack more readily, be dominant in threat encounters, be less active and spend less time swimming high in the water, consume more food, and show higher growth rates and lower mortality. Implications for warm‐water aquaculture are discussed, and practical management techniques to minimize mortality and maximize productivity are suggested.
Fishes of the Lough Hyne marine reserve
Authors: Minchin D.
Published: January 2006

Lough Hyne marine reserve is a sea inlet, of area c. 60 ha, on the south‐west Irish coast. Conditions vary from the exposed outer harbour of Barloge Creek to a sheltered marine basin, with depths to 47 m. A shallow, narrow connection, the Rapids, between the two parts causes a reduced tidal range within the marine basin. The status of 72 fish species is given, 38 of them being recorded for the first time from this locality. Eleven goby species are present, including well established but isolated populations of Gobius cruentatus and G. couchi. The listing comprises museum material, previous records and direct observations from 1976 to 1985 inclusive. This reserve is recognized by the Council of Europe as part of an international biogenetic network of reserves.
The fish populations of some streams in Wales and northern England in relation to acidity and associated factors
Authors: Turnpenny A. W. H. , Sadler K. , Aston R. J. , Milner A. G. P. , Lynam S.
Published: January 2006

Electrofishing and water quality surveys were carried out on 60 upland moorland streams in central and north Wales and the Peak District of England (south Pennines). A number of biological characteristics of the fish populations were recorded, including species representation, population density and biomass and, for brown trout, Salmo trutta L., only, growth, condition factor and diet. The stream waters were also analysed over a 2‐year period for pH, calcium, aluminium and the heavy metals copper, zinc and lead.

Mean pH levels in the streams ranged from 5.0 to 7.6, with calcium concentrations in the range 0.80–27 mg 1−1. Trace metal concentrations (Al, Cu, Zn, Pb) tended to be elevated in the more acid streams. The latter had fewer fish species, and a higher proportion was fishless, 73% at pH < 5.5 compared with 6% at pH >6.5. Trout and eels, Anguilla anguilla L., predominated at lower pH values, but at reduced population levels.

Dietary composition and stomach fullness of trout were similar throughout the stream pH range. More than 40% of the diet was derived from surface and terrestrial sources, supplementing autochthonous items. Growth (as back‐calculated length to end of first year of life) and condition factor did not vary significantly with respect to stream acidity. It is thus concluded that the impoverishment of trout populations in the more acid streams was not a second‐order effect acting through the lower trophic levels.

Water quality acting directly on fish would appear to account for the poor status of salmonid fisheries in acid streams. Absence or paucity of salmonids was related to high levels of labile monomeric aluminium (>40 μgl−1) or Cu‐Zn‐Pb toxicity (>0.4 t‐LC50 to rainbow trout, Salmo gairdneri Richardson). Limiting values in this study correspond well with published laboratory and field data.
Maximum daily ration and the pattern of food consumption in haddock, Melanogrammus aeglefinus (L.), and dab, Limanda limanda (L.)
Authors: Hall S. J.
Published: January 2006

Food intake was measured under conditions of continuous food availability for haddock, Melanogrammus aeglefinus (L.), and dab, Limanda limanda (L.). Haddock consumed approximately 75% of all food during the day, with a peak of feeding at dusk and an inferred peak at dawn; peaks of feeding were associated with larger meals. By contrast, dabs were mainly night‐time feeders with daily consumption rates that were approximately 40% lower than those shown by haddock. Comparison of haddock maximum daily ration with published estimates of consumption in the wild indicate that wild haddock feed at between 15 and 22% of their maximum capacity. Using published data on gastric evacuation, the relationship between meal size and stomach residuum was investigated. There was no detectable relationship between these two variables.
The effect of temperature on development and hatching of scad, Trachurus trachurus L., eggs
Authors: Pipe R. K. , Walker P.
Published: January 2006

The effect of temperature on the rates of development and hatching of artificially fertilized eggs of the scad, Trachurus trachurus L., was studied using a thermal gradient incubator. Development of eggs through to hatching occurred within the temperature range 10.5–21.2° C, with greatest survival between 12.2 and 15.8° C. The mean egg diameter was 0.94 mm and mean length of larvae on hatching 2.46 mm. Regressions of development time on mean incubation temperature are presented. The data are compared with those reported in the literature and related to sea temperatures in scad spawning grounds.
Histocompatibility analyses in tetraploids induced from clonal triploid crucian carp and in gynogenetic diploid goldfish
Authors: Nakanishi T.
Published: January 2006

Histocompatibility analyses in goldfish were performed using the tetraploid goldfish‐crucian carp hybrid and the first generation of gynogenetic diploid (GD1) goldfish. Tetraploids were obtained by crossing clonal triploid crucian carp with goldfish. GD1 goldfish were produced by the suppression of the second meiotic division. Tetraploid scale grafts on triploid clone members evoked an acute rejection in 4–6 days, whereas the reverse transplants were accepted or rejected chronically. Reciprocal grafting between tetraploids showed subacute rejection in 10–12 days, although some fish showed chronic rejection in 20–30 days. On the other hand, scale grafts reciprocally exchanged among triploids were intact even 3 months after grafting, although some of them showed a unidirectional rejection pattern. Furthermore, allograft rejection among gynogens occurred between 5 and 20 days, whereas all the scale allografts between members of control siblings were rejected within 9 days. In addition, neither accelerated acute rejection nor acceptance of allografts was observed in grafts exchanged among GD1 goldfish. These results suggest that single doses of histocompatibility alleles are effective in eliciting acute rejection, and each of the fourth haploid set of chromosomes originating from paternal goldfish might share the same histocompatibility antigens to a large extent. This experiment also indicates that the genecentromere recombination rate is quite high with respect to the histocompatibility loci in this species.
Effects of sublethal concentrations of potassium dichromate on the occurrence of splenic melano‐macrophage centres in juvenile plaice, Pleuronectes platessa, L.
Authors: Kranz H. , Gercken J.
Published: January 2006

Plaice were exposed to 0.5 and 2.0 ppm potassium dichromate (K2Cr2O7) concentrations for 27 days. In both water concentrations chromium was accumulated up to a level of 400 ppb in the carcass of the fish. At the same time the number of splenic melano‐macrophage centres (MMC) tripled, whereas their average size was reduced to one third. The percentage area of MMC in the splenic tissue remained unchanged. Histological alterations following exposure to K2Cr2O7 included increases both in melanin content of the MMC and in the number of melanin‐containing cells within blood vessels; also, the splenic ellipsoids became less clearly demarcated. Splenic melano‐macrophages show a decreased ability to aggregate to form large MMC under the influence of K2Cr2O7, which leads to the assumption that the turnover rate of macrophage settlement in, and macrophage elimination from, the spleen is increased.
Metabolic and immunological effects of endotoxin in the plaice, Pleuronectes platessa L.
Authors: Fletcher T. C. , White A.
Published: January 2006

In an effort to identify factors contributing to the resistance of fish to endotoxin toxicity, the metabolic effects of an intraperitoneal injection of a Boivin preparation of E. coli lipopoly‐saccharide (LPS) were studied in plaice over 4 days. Significant changes were found in serum concentrations of glucose, cortisol and non‐esterified fatty acids but not in total or free cholesterol. The effect of injected LPS on the phagocytic capacity of kidney neutrophils was examined because of the possible use of LPS to promote non‐specific immunity. There was no enhancement of the chemiluminescent response to the phagocytosis of unopsonized bacteria by neutrophils from plaice 24 h after LPS treatment.
Lymphocytopenia and interrenal activity during sexual maturation in the brown trout, Salmo trutta L.
Authors: Pickering A. D. , Pottinger T. G.
Published: January 2006

In three different strains of brown trout a marked reduction in the number of circulating lymphocytes occurred in the blood of sexually mature male and female fish during the spawning season. This lymphocytopenia was closely correlated with elevated plasma cortisol levels in all three strains. It is well established that sexual maturation in salmonid fish is associated with an increase in susceptibility to disease: the present study provides strong evidence that this is mediated, at least in part, by a cortisol‐induced suppression of lymphoid activity. These findings are discussed in relation to possible physiological roles of cortisol during the spawning period and to the evolution of semelparity in salmonid fish.
The problem of sexual inversion in the minnow, Phoxinus phoxinus (L.)
Authors: Rasotto M. B. , Cardellini P. , Marconato E.
Published: January 2006

The incidence of sexual inversion in Phoxinus phoxinus has been studied by examining histologically (a) the gonads of 406 adult specimens caught from the wild during a period of 16 months, (b) the gonads of 168 adults kept in captivity in groups with an experimentally altered sex‐ratio, and (c) the differentiation of the gonads in the fry.

All the adults had either testes or ovaries and no case of intersexuality was observed. For both testis and ovary, we recognized two phases, depending on the seasonal cycle: an active spring‐summer phase, corresponding with the period of reproduction, and a quiescent autumn‐winter phase. The ovaries showed an asynchrony in oocyte development, which is typical of species that spawn many times during the breeding season.

In P. phoxinus the ovaries are easily recognizable just one month after hatching and testes are well differentiated in 2‐month‐old fingerlings. Differentiation is, therefore, precocious and follows a pattern typical of gonochoristic species in which hermaphroditism never occurs.
Food and growth of age‐0 smelts, Osmerus eperlanus, in a Norwegian fjord lake
Authors: Næsje T. F. , Jonsson B. , Klyve L. , Sandlund O. T.
Published: January 2006

Pennate diatoms, especially Aslerionella spp. and Tabellaria fenestrata, were the most important food items for smelts in Lake Mjøsa during the first month of external feeding; rotifers and early stages of copepods were eaten occasionally. Later, during summer and autumn, crustacean zooplankton (cladocerans and copepods) were the most important food items; selected species were Polyphemus pediculus, Eudiaptomus gracilis, Limnocalanus macrurus, Heterocope appendiculata. Leplodora kindti, and Bythotrephes longimanus; some smelts larger than 7.4 cm fed on Mysis relicta. In 1979 and 1980, mean lengths of smelts in October‐November were 4.7 cm and 7.2 cm, respectively. A difference in length increment between the two years may have resulted from summer water temperatures being higher in 1980 than in 1979.
An automated method for counting and sizing fish eggs
Authors: Witthames P. R. , Walker M. Greer
Published: January 2006

This paper describes an automated method for counting and sizing fish eggs in the diameter range 200–2500 μm. Eggs, suspended in water, are pumped at a controlled rate through an electronic sensor which produces a voltage pulse which is proportional in amplitude to particle size. The sensor is connected to a HIAC Criterion PC‐320 particle analyser which is in turn connected to a Tracor Northern pulse height analyser. This equipment separates the voltage pulses into 398 recording channels. An ACT 1 Sirius microcomputer is used to store the data, transform it to egg size and then produce a histogram of egg size distribution in 20‐μm class intervals.

The method has a counting accuracy of 99.5 ± 0.5%. It has been compared with two manual methods of estimating egg numbers.
Phosphoglucose isomerase polymorphism in the common goby, Pomatoschistus microps (Krøyer) (TeleosteirGobiidae), around the British Isles
Authors: Al‐Hassan L. A. J. , Webb C. J. , Giama M. , Miller P. J.
Published: January 2006

Phosphoglucose isomerase (PGI) polymorphism has been investigated by horizontal starch‐gel electrophoresis in the common goby, Pomatoschistus microps (Krøyer), from 21 localities around the British Isles and at Roscoff, France. Sixteen PGI phenotypes were observed, consistent with occurrence of four alleles at each of the two loci (A,B). In the Teign estuary at Shaldon, Devon, seasonal fluctuation in PGI‐A allele frequencies was accompanied in some months by departure from Hardy‐Weinberg equilibrium. At this locality, a significant change in PGI‐A allele frequencies was found with increasing modal age of sample (within a year class) but not between year‐classes over eight years. Similar stability is noted for other areas. Major alleles (PGI‐A2, A3; PGI‐B2, B3) were found at all localities, but with marked differences in proportions. Atlantic coast populations tended to have higher A2 and B2 frequencies than those of the North Sea and English Channel, with Irish Sea populations having high A2 but low B2. Historical and selective causes for this geographical variation are discussed. A significant correlation exists between the frequencies of the major PGI‐A alleles and maximum monthly mean sea temperature for the same area.
Response of fed and starved roach, Rutilus rutilus, to sublethal copper contamination
Authors: Segner H.
Published: January 2006

Fed and starved yearling roach, Rutilus rutilus. were subjected to a sublethal copper contamination of 80 μg Cu × l−1 for 7 days. Copper accumulation was determined by atomic absorption spectroscopy. In both fed and starved fishes, the gill tissues showed significant uptake of copper, while the liver tissues of only starved specimens showed significant accumulation. Refeeding roach after 7 days of starvation and contamination resulted in a significant decrease of liver copper content. No copper release from the liver occurred if, after cessation of exposure, starvation was continued. Analysis of liver ultrastructure demonstrated no pathological lesions or copperspecific alterations. Cellular changes represented combined influences of nutrition and of copper. Qualitative as well as quantitative results provide evidence that the nutritional status of a fish is of great importance in modifying its response to sublethal copper contamination.
Lunar periodicity in the spawning of Tilapia mariae in the Ethiop River, Nigeria
Authors: Schwanck E.
Published: January 2006

In a clear‐water Nigerian stream, Tilapia mariae showed lunar periodicity in breeding activity over a 9‐week study period. Most clutches were laid during the last quarter of the moon cycle. It is suggested that spawning before full moon enhances the effectiveness of the parental care by allowing a maximal amount of moonlight during the most critical phases in the development of the young and by providing a cue for the pairs to spawn at the same time.
An experimental investigation of the non‐reproductive, post‐mature state in winter flounder
Authors: Burton M. P. , Idler D. R.
Published: January 2006

Winter flounder from known locations were sorted according to their reproductive status about 4 weeks before spawning. Five groups were then fed to satiation and three groups were not fed. The experiment was terminated at the end of the summer feeding season. At termination, only one of the recently spawned fish with restricted feeding showed gonad recrudescence. Conversely, all previously reproductive fish which had been fed to satiation showed gonad recrudescence. Fish fed to satiation included some which had been initially designated non‐reproductive post‐mature. These experiments indicate that a non‐reproductive post‐mature state is inducible and may be reversible, with the switch related to nutritional status.
Notes on the biology of Spratelloides lewisi (Wongratana, 1983), a recently described species of sprat from Papua New Guinea waters
Authors: Dalzell P.
Published: January 2006

The biology of two populations of Spratelloides lewisi, one from the Ysabel Passage and the other from Cape Lambert, were studied during 1980 and 1981. A total of 2201 specimens of S. lewisi were collected from a regular sampling programme of tuna bait‐fish catches. The annual length frequency distributions for both populations indicated differences in the full recruitment length and maximum size attained between the two populations. The age and growth of S. lewisi was described at both locations by von Bertalanffy growth curves fitted to length‐at‐age data obtained by reading the daily growth increments of the sagittae. Ovarian maturation data suggested there was no distinct spawning seasonality for this species: spawning was either protracted or markedly reduced over several months. The total annual mortality rates for both populations of S. lewisi were high, but consistent with those of other short‐lived fishes. An estimate of the natural mortality rate for the Ysabel Passage population of S. lewisi by an empirical method corresponded very closely to another estimate based on the relationship between total mortality and fishing effort.
Size at maturity in male Gambusia heterochir
Authors: Yan H. Y.
Published: January 2006

The size at maturity in many male poeciliid fish is believed to be controlled by ‘social control mechanism’, and post‐maturation growth is insignificant. In the Clear Creek gambusia, Gambusia heterochir. post‐maturation growth in male fish is limited. Male G. heterochir matures at a fixed size, and age of maturation is dependent on environmental factors (e.g. temperature). In the presence of an adult male, the maturation size of a young male is largely determined by genetic factors rather than ‘social control’ factors. A male can switch its status as a ‘dominant’ or ‘subordinate’ male, depending on the relative size of rival males in mating competition. Mating success of a large (dominant) male reduces as the number of competing small (subordinate) males increases. These unique reproductive tactics may explain in part why ‘social control mechanism’ does not play a key role in determining the maturation size of male G. heterochir.
Leuciscus cephalm (Linnaeus), with records of fingerling adult males, Leuciscus plemobipunctatus (Stephanidis) and their hybrids from western Greece
Authors: Bianco P. G.
Published: January 2006

The spawning season of chub, Leuciscus cephalus, in western Greece starts in January‐February when males are aged at least 2 + and females 3 + (rarely 2 +) years. In the R. Ermitsa (Achelos R. basin) a population is reported with fingerling adult males with developed gonads and breeding tubercles at a size of 42 72 mm s.l. Leuciscus pleurobipunctatus breeds between February and the first half of May, when males are aged at least 1 + and females 2 + (sometimes also 1 +); their life span is about 4 years. L. cephalus × L. pleurobipunctatus hybrids were found in the R. Ermitsa (five specimens) and R. Louros (one specimen). In the former the contemporary presence of adult fingerling male chub, the smallest adults of L. pleurobipunctatus, and hybrids between the two species, may be related to channel width and the human interference which has resulted in considerable disturbance of the habitat.
Size characteristics and diet of emergent chinook salmon in a small, stable, New Zealand stream
Authors: Field‐Dodgson M. S.
Published: January 2006

The emergence timing, quality and diet of chinook salmon, Oncorhynchus tshawytscha, fry were studied as they emerged from ten natural redds. The impact of selected environmental factors on emergence was studied also. Samples of fry were obtained daily using redd traps.

The mean period of total emergence for redds with more than 450 fry emerging was 44.8 days (range 25–57 days), but for 80% of the fry in each redd to emerge the mean time elapsed was 10.8 days (range 6–21 days). No fry sampled had a visible yolk sac. The effect of temperature and light on emergence timing was weak, but stream flow had a strong influence. Fry length was constant for each redd throughout emergence, but fry weight tended to decline; consequently condition factor declined also. There was evidence that fry fed before emergence, but they did not grow. The major prey item, Deleatidium spp. (47.4% of the contents of all stomachs sampled), was the most abundant invertebrate in stream benthos and drift. Empty stomachs were prevalent at the start of emergence, with full stomachs becoming more common as emergence progressed.

The time distribution of numbers of fry emerging was usually unimodal, but occasionally bimodal. Over one third of fry emerged during the best 2 days of sampling.
Diseases of the African estuarine catfish Chrysichthys nigrodigitatus (Lacépède) from the Cross River estuary, Nigeria
Authors: Obiekezie A. I. , MÖer H. , Anders K.
Published: January 2006

A survey based on monthly sampling of commercial catches was carried out in the Cross River estuary in 1984 and 1985 to determine the extent of parasitization and occurrence of externally visible lesions on the bagrid catfish Chrysichthys nigrodigitatus. Infections with the following parasites were encountered: Henneguya chrysichthyi (32%), Protancylodiscoides chrysichlhes (77%). Siphodera ghanensis (4.2%), Aspidogaster africanus (0.1%), Hysterothylacium larvae (64%), Nerolica orbignyi (1.5%), Ergasilus lalus (27%), and Chonopeltis brevis (0.02%). A new kind of epidermal papilloma was found and is described. On a yearly average, less than 0.5% of the catfish population was affected by either skeletal deformities or skin ulceration. Fin rot was observed from December to May, reaching a prevalence of 79% in February. Gill myxozoosis due to Hemwguya chrysichthyi is considered the most important parasitic disease of the fish, occurring throughout the year with a maximum prevalence of 76% in October. Results of the study are discussed in the light of a projected intensive cultivation of the fish in the extensive estuaries and lagoons bordering Nigeria's coastline.
Quantitative and qualitative studies of the bacterial microflora of turbot, Scophthalmus maximus L., gills
Authors: Mudarris M. , Austin B
Published: January 2006

Populations of aerobic heterotrophic bacteria, occurring on the gills of healthy turbot, were estimated using a dilution plate technique. From a comparison of 18 media, the highest counts, i.e. 7.0 × l05 g−1, were obtained after incubation at 15–25°C on a specifically formulated medium which contained low quantities of beef extract, casein, tryptone and yeast extract. These bacteria were equated with Asticacaulis sp., Hyphomicrobium sp., Janthinobacterium lividum, Prosthecomicrobium sp., Pseudomonas fluorescens and Vibrio sp. Evidence from scanning electron microscopy pointed to a general lack of intimate colonization of exposed areas of the gill. Instead, micro‐organisms colonized protected niches, such as the clefts between lamellae and in secluded areas on the arches.
Aspects of the spawning biology of the Brazilian sardine, Sardinella brasiliensis (Steindachner, 1879), (Clupeidae)
Authors: Isaac‐Nahum V. J. , Cardoso R. de D. , Servo G. , Rossi‐Wongtschowski C. L. del B.
Published: January 2006

Biological data, size frequency distribution of intraovarian oocytes, maturity indices and histological observations of the gonads were used to assess the spawning cycle of S. brasiliensis, sampled September 1981–August 1982 throughout the main fishing area off the Brazilian coast (22°S to 28°S). Post‐ovulatory follicles are described and classified, and the incidence of mature females displaying these structures was calculated. The main findings were (a) spawning occurred during the spring and summer with a maximum in December and January; (b) spawning occurred throughout the area studied; (c) spawning was fractional; (d) average batch fecundity was 26 000 oocytes per female, or 393 eggs g−1; (e) spawning frequency reached values of approximately 50% during the spawning peak, but was sensibly lower during the other months of spawning activity.
A comparison of the effects of temperature on melanophore in vitro responses to noradrenalin in two teleost species adapted to cold ocean and tropical conditions
Authors: Burton D.
Published: January 2006

Melanosome‐aggregating responses to noradrenalin in winter flounder, Pseudopleuronectes americanm Walbaum, manifest different in vitro temperature characteristics compared with such activity in sailfln molly, Poecilia velifera Regan. Winter flounder off St John's are adapted to cold ocean temperatures between − 1° C and + 15° C associated with the Labrador current, whilst sailfin molly is a tropical species adapted to temperatures up to about 30° C. The experimental data indicate that melanophores from these two species are physiologically adapted to function in contrasting thermal environments. Consequently, the optimum temperature for melanosome aggregation in winter flounder is approximately 20° C, and that of the tropical species approximately 40° C. Also, flounder melanophore In vitro responses are relatively uninfluenced by low temperatures, which drastically inhibit sailfin molly melanophore activity.
Bioenergetic model of planktivorous fish feeding, growth and metabolism: theoretical optimum swimming speed of fish larvae
Authors: Darowski K. , Takashima F. , Law Y. K.
Published: January 2006

The feeding activity of an individual fish larva is described by an equation which includes parameters for the area successfully searched, probability of food capture multiplied by the cross‐sectional perceptive visual field, larval swimming speed and the time required to consume a unit of food energy. The proportion of ingested food energy used for metabolism increases exponentially with increasing swimming speed. The model predicts that food consumption rate increases asymptotically whereas metabolic rate increases exponentially. This results in a predicted growth rate curve that reaches a maximum at a certain swimming speed and decreases at both higher and lower speeds.

The model can be used to predict the influence of type of prey, prey density, water temperature etc. on larval growth. An expression describing how many hours per day fish larvae must forage in order to grow at a certain daily body weight gain allows the limits of environmental conditions for positive, zero and negative growth rate to be set.

Results of simulations demonstrated that the optimum swimming speed for maximum growth of coregonid larvae increased with an increase in food density, decrease in water temperature or decrease of prey vulnerability. At optimum ‘theoretical’ swimming speed an increase in water temperature from 5 to 17° C required the food density to be increased from 20 to 80 copepods l−1 in order to maintain a daily growth increment of 2%. The minimum Artemia density required for maintenance metabolism increased from 10 to 30 items 11 over the same temperature increase from 5 to 17° C, and food densities required for 8% growth rates were 26 and 56 Artemia nauplii l−1 at 5 and 17° C, respectively.

Contrary to previous findings, results of the present study suggest that metabolic rates of actively feeding fish larvae may be from 5 to 50 times the standard metabolic rate: earlier studies suggested that a factor of 2–3 may be generally applicable.
Occurrence of parasites of the freshwater mugilid fish Liza abu (Heckel) from Basrah, southern Iraq
Authors: Mhaisen F. T. , Al‐Salim N. K. , Khamees N. R.
Published: January 2006

In monthly samples of Liza abu collected November 1981–October 1982 from Mehaijeran Creek, a western branch of Shatt–Al–Arab river south of Basrah, fishes were infected with the third larval stage of the nematode Contracaecum sp., the acanthocephalan Neoechinorhynchus agilis and the gill crustacean Ergasilus mosulensis.

Generally, the changes in the percentage prevalence coincided with the changes in the mean intensity of infection. There were no significant differences between the infection of male and female fishes in the cases of the monthly variations of infection with Contracaecum sp. and of infection with both Contracaecum sp. and E. mosulensis, according to fish length, but in other cases more female fishes were infected than males.

Infection with Contracaecum sp. decreased gradually in the larger fishes. In the case of both N. agilis and E. mosulensis, the infection at first increased with increase in fish length but decreased in larger fishes.

Infection with Contracaecum sp. occurred only during May–August and disappeared during September. The peak for N. agilis was in April, and it disappeared during summer. Infection with E. mosulensis disappeared during winter months.
Thermal enrichment of a reservoir and the effects on annulus formation and growth of largemouth bass, Micropterus salmoides
Authors: Galloway M. L. , Kilambi R. V.
Published: January 2006

Analysis of largemouth bass scales, including those from 48 tagged and recaptured fish, revealed that many scales had more ‘annuli’ than possible for the age of Flint Creek Cooling Reservoir. The mark‐recapture data indicated the formation of one supernumerary annulus per year for most bass. Time of formation of true and supernumerary annuli and the causative factors are discussed.

Growth of bass from this reservoir greatly exceeded that reported for thermally unaltered reservoirs of Northwest Arkansas, due to the existence of a nearly year‐round growing season, a result of thermal enrichment. The relationship between the ratio of electric power output to reservoir surface area and growth offish was evaluated with reference to published data on cooling reservoirs.
The relationship between nitrogen output and changes in mucous cell function in the amphibious teleost Blennius pholis L. during aerial exposure
Authors: Sayer M. D. J. , Blackstock N.
Published: January 2006

The numbers of mucous cells in the epidermis of the head and body and in the surface of the gill arch of the amphibious blenny, Blennius pholis L., were estimated on fish immersed in sea water and after 4 h aerial exposure. During emersion there appeared to be a considerable reduction in the frequency of epithelial mucous cells in the areas studied, although counts for the head epidermis were somewhat variable. A concomitant decline in the number of cells thought to be actively secreting was also recorded in tissue samples from both the head and gills, while in the body epidermis the potential for mucus‐secretion was maintained close to the levels observed in immersed fish.

Histochemical studies revealed epidermal mucous cells containing either sialylated acid mucopolysaccharides or neutral mucins, or a mixture of these, in both the head and the body, whereas in the gill arch epithelia there were, in addition, cells containing sulphated acid mucopolysaccharides. After emersion, a disproportionate loss of cells containing neutral and sialylated mucus from the gill epithelia resulted in an increase in the proportion of secreting cells staining positively for sulphated acid mucopolysaccharides.

The results of this study are discussed in relation to nitrogenous excretion during aerial exposure.
Morphometric analysis of two ecologically distinct forms of Arctic charr, Salvelinus alpinus (L.), in Loch Rannoch, Scotland
Authors: Gardner A. S. , Walker A. F. , Greer R. B.
Published: January 2006

Gill–netted samples of Arctic charr from Loch Rannoch, Scotland were bimodal when tested by univariate and multivariate morphometric analyses. The separation into two morphs corresponded very closely (95–98%) with fish classified subjectively in the field as benthic or pelagic, based largely on colour differences and ecological observations. The benthic charr had relatively longer heads, larger eyes and more powerful jaws than the pelagic charr. Unlike sympatric morphotypes described from Scandinavia and Greenland, neither Rannoch morph is dwarfed.
Development, morphometry and particle retention capability of the gill rakers in the herring, Clupea harengus L.
Authors: Gibson R. N.
Published: January 2006

The development of gill rakers in the herring, Clupea harengus L. was followed from the larva to the adult. The first rakers appear on the gill arches at a total length (t.l.) of about 16 mm. Their number then increases rapidly until the fish are about 50 mm t.l. when the rate of addition becomes much slower. The length of individual rakers and the space between them continues to increase throughout life. The rakers on the first gill arch account for almost 60% of the whole filtering area. The observed particle retention capabilities of the fish when filter‐feeding were lower than those expected on the basis of the estimated spaces between the rakers. Several reasons are suggested for the discrepancy.
Changes in the ovary of the Gulf killifish, Fundulus grandis (Baird and Girard), during seasonal and semilunar spawning cycles
Authors: Greeley M. S. , MacGregor R. , Marion K. R.
Published: January 2006

Annual and semilunar ovarian cycles were examined in a wild population of Gulf killifish, Fundulus grandis, from the Alabama (U.S.A.) coast of the Gulf of Mexico. Production of mature eggs was first observed in late February, with the main breeding season beginning by mid‐March and extending into August. The season was punctuated by shorter, typically semilunar, cycles of spawning activity and gamete development that became more pronounced as the season progressed. In September any remaining ovulated eggs and oocytes past the intermediate‐cortical alveolus stage underwent atresia, suggesting that the latter may be the final gonadotropin‐ independent stage of oocyte development in F. grandis. Seasonal proliferation of primary growth phase and cortical alveolus oocytes occurred in late autumn and early winter (October‐January). Vitellogenic oocytes first appeared in early February at the start of a month of intense and rapid vitellogenic oocyte growth prior to the March onset of a new breeding season.