bluuebunny/crossref_metadata_2025 huggingface dataset:
A new look at optimal foraging behaviour; rule of thumb in the rainbow trout
Authors: Bres M.
Published: January 2006

A realistic model of foraging behaviour in stream‐living rainbow trout was developed to address some shortcomings of previous tests of optimal foraging theory. The model predicts prey selection based upon both energy‐maximization and number‐maximization strategies. Trout diet selection on the basis of prey size and prey calorific content was examined under laboratory conditions.

Diet composition was strongly influenced by relative abundance of prey types under all feeding regimes, as predicted by the model. Additional important factors include fish stomach capacity and daily digestive capacity. Experimental results strongly suggest that prey selection in rainbow trout is not based on calorific content. Examination of energy (kJ) obtained from observed diets showed no energy penalties associated with ‘suboptimal’ food choices, since all fish (regardless of their choices) consumed far more energy than required for their basic metabolic needs.
The development of feeding behaviour in the lumpfish, Cyclopterus lumpus
Authors: Brown J. A.
Published: January 2006

This study concerned the development of feeding in larval lumpfish, Cyclopterus lumpus, and tested the hypothesis that these large, well‐developed larvae would not use typical ‘larval‐like’ modal action patterns (MAPs) in high frequency during early feeding. The early behavioural repertoire of larvae is unique, owing to a well‐developed, ventral adhesive disk used to adhere (Cling) to available surfaces. Most early feeding MAPs were performed from the Cling position; larvae did not swim in the water column to chase and capture prey during the first three weeks post‐hatch. Changes in feeding were not as predicted. The original hypothesis was refined to include a ‘state of development’ criterion as well as larval size.
Towards an isolation syndrome for the angelfish, Pterophyllum scalare
Authors: GÓmez‐Laplaza L. M. , Morgan E.
Published: January 2006

The behaviour of individual angelfish, Pterophyllum scalare, isolated for 4 days in the laboratory has been compared with that of the same fish in groups. Locomotor activity, feeding behaviour, aggression and responses to novel stimuli have been studied. Isolated fish are less active, approach the surface to feed less readily and are slower to recover from sudden mechanical shock than when kept in a group. In contrast, isolates are more attentive to a gradually‐applied, novel, visual stimulus. The aggressive behaviour of post‐isolates on return to the group tank was not significantly different from that shown before isolation.
Heart rate as an indicator of activity, metabolic rate, food intake and digestion in pike, Esox lucius
Authors: Armstrong J. D.
Published: January 2006

For pike in the laboratory, the relationship between heart rate (fH) and oxygen consumption (VO2, mg h−1 standardized to a 500‐g fish weight) can be described by a significant linear regression valid for heart rates below 55 beats min−1. Heart rate increases during activity and feeding, accurately reflecting fluctuations in metabolic rate; so it can be used as a measure of metabolic rate in the field, using heart beat telemetry techniques. Post‐prandial heart rates are elevated, and closely correlated with the calorific value of the food taken in the preceding meal. Meal size can be estimated from the heart rate record with an error of less than 10%.
Report of a naturally masculinized female of the Clear Creek gambusia, Gambusia heterochir Hubbs
Authors: Van H.‐Y.
Published: January 2006

A naturally masculinized female of the Clear Creek gambusia, Gambusia heterochir Hubbs, was collected from the headspring of Clear Creek, Menard County, Texas. The fish had 11 well‐developed, late stage embryos. It also possessed an incompletely developed gonopodium and a pair of male‐like, pectoral fins. This discovery constitutes the first report of natural masculinization within the genus Gambusia.
Comparative developmental biology of pink salmon, Oncorhynchus gorbuscha, in southern British Columbia
Authors: Beacham T. D. , Murray C. B.
Published: January 2006

Eggs and alevins from 21 families of pink salmon, Oncorhynchus gorbuscha, from five odd‐year broodline stocks spawning in southern British Columbia were incubated under controlled water temperatures of 4° C, 8° C and 12° C. There were significant differences in egg survival among stocks and among families within stocks at all incubation temperatures, but the differences were greatest at 4° C. Alevin survival was at least 97% for each stock at each temperature. The most northern spawning stocks had higher egg survival at 4° C than did the others. Hatching time of the alevins and emergence time of the fry were similar for all five stocks. Alevins hatching at 8° C were longer than those hatching at 4°C or 12°C, but there were no stock differences in alevin length or tissue weight. Stocks with larger eggs produced alevins of greater total weight and more yolk. Emergent fry from Vancouver Island stocks had the greatest tissue weight at 12° C, but Fraser River fry were heaviest at 8° C. There were significant differences among families within stocks for alevin and fry size parameters, suggesting that family variation should be accounted for in studies of salmonid developmental biology.
Histopathology in Paulicea lutkeni (Pisces: Pimelodidae) resulting from infections with Megathylacus brooksi and Jauela glandicephalus (Cestoda: Proteocephalidae)
Authors: Elras J. C. , Rego A. A. , Pavanelll G. C.
Published: January 2006

The histopathology in Paulicea lutkeni naturally infected with Megathylacus brooksi and Jauela glandicephalus is described. Megathylacus brooksi attaches to the epithelium of the anterior intestine by means of suckers, resulting in damage to the epithelium, haemorrhages and lymphocyte infiltration. Jauela glandicephalus penetrates through all layers of the intestine. This penetration elicits an intense host‐response resulting in the hyperplasy of connective tissue and formation of a nodule surrounding the scolex of the parasite. Lymphocyte infiltration was observed. Concurrent infections were found in some specimens.
Erythrocyte fusion in heat‐shocked Atlantic salmon
Authors: Fox D. P. , Johnstone R. , Durward E.
Published: January 2006

Feulgen‐stained blood smears taken from deformed alevins in a heat‐shocked Atlantic salmon population were analyzed by microdensitometry. Within individual alevins, variable proportions of erythrocytes of differing DNA contents were seen. In a frequency distribution of these cells, peaks of DNA content were observed whose means appeared to increase in an arithmetic series. It is suggested that this, together with the complex nuclear morphology of the higher members of the series, is most likely to have arisen as a consequence of cell fusion processes involving, originally, haploid cells. During the 5‐week period of yolk sac absorption there was an apparent selection against erythrocytes having higher DNA contents.
Intraspecific variation in competitive ability and food intake in salmonids: consequences for energy budgets and growth rates
Authors: Metcalfe N. B.
Published: January 2006

The interactions between dominance status, feeding rate and growth in rainbow trout, Salmo gairdneri Richardson, were analyzed using published data on experimental populations. There was a positive correlation between metabolic expenditure and food intake in both dominant and subordinate fish, but dominants obtained a greater intake for a given expenditure than did subordinates. Subordinates that adopted a high–return/high–cost foraging strategy actually expended more energy than they acquired, whereas those that minimized energy expenditure obtained a net energy gain. This led to the surprising finding that the growth rate of subordinates was negatively correlated with food intake.
Influence of toxic chemicals on the chemotactic response of fish macrophages
Authors: Weeks B. A. , Warinner J. E. , Mason P. L. , McGinnis D. S.
Published: January 2006

The chemotactic efficiency of macrophages isolated from the kidney of spot, Leiostomus xanthurus, and hogchoker, Trinectes maculatus. was determined in fish captured from the York River and the heavily polluted Elizabeth River (Virginia). Chemotactic activity was quantified in Boyden chambers using Escherichia coli as the chemotactic stimulus. Macrophage chemc‐taxis was found to be markedly reduced in the Elizabeth River fish as compared to York River controls. Chemotactic migrations of macrophages at 90 min were 55% and 33% for control and experimental spot, respectively. Values for control and experimental hogchoker were 85% and 56%, respectively. The macrophage chemotactic activity of Elizabeth River fish returned to normal (spot, 56%; hogchoker, 80%) after the fish were held in clean water for 3 weeks. This indicates that the decreased chemotactic activity was related to exposure to Elizabeth River pollutants but may be reversible.
Effects of size, culling and social history on growth of cultured elvers, Anguilla anguilla (L.)
Authors: Wickins J. F.
Published: January 2006

The growth of newly‐caught elvers was measured after they were separated into four size categories and induced to feed. All sizes grew equally well, indicating that size differences at capture reflected migration history rather than the presence of genetically poor or good growers. Socially experienced groups of elvers of equivalent size grew, on average, less well due to the presence of socially suppressed fish and fish that did not respond so well to handling or a new social environment.

Replicate groups of rapidly‐growing elvers were culled at either 2‐ or 4‐weekly intervals. The large animals removed were replaced by animals of modal size and the growth of selected residual size groups was compared to unculled control groups. Culling tended to increase the instantaneous growth coefficient of remaining small elvers but the added elvers of modal size may have exerted a disproportionate influence on mean growth rates.

The effect of large elvers on the growth of small elvers (and vice versa) was monitored using fish labelled subcutaneously with acrylic paint. Separate populations of elvers of each size group were used as controls. After 82 days in mixed populations, about 36% of the original large fish had been’ overtaken’ by small category fish.

The results suggested that, following disturbance, the expression of growth in elvers was not necessarily related to size or previous hierarchical position but may be governed by behavioural or physiological responses to handling and changed social environments.
Circulation pattern and transmission dynamics of the supra‐population of the nematode Cystidicoloides tenuissima (Zeder) in the River Swincombe, England
Authors: Aho J. M. , Kennedy C. R.
Published: January 2006

The circulation pattern and transmission dynamics of larval and adult Cystidicoloides tenuissima in all its intermediate and definitive hosts were investigated and quantified at three sites in a small upland stream over a period of 1 year. Both brown trout, Salmo trutta, and salmon parr, S. salar, were suitable definitive hosts, but because of the greater importance of the mayfly intermediate host in the diet of trout, between 73 and 98% of the parasite infrapopulation in fish circulated through this species. Trout was the only required host, and was alone responsible for the perpetuation of the parasite suprapopulation in the river. Around 99% of the parasite's eggs produced originated from trout but, of these, 90% or more failed to be ingested by an insect. Larval parasites were found in 18 species of insects, but could develop to the infective third stage in only one species, the mayfly Leptophlebia marginata. Two common but unsuitable species harboured up to 80% of the larval parasites, and less than 10% actually circulated through L. marginata. Differences in circulation pattern between sites could be related more to differences in fish feeding preferences than to differences in fish or insect density, but monthly differences in transmission rate reflected both fish diet and insect abundance. The overall mean transmission rate of eggs to larvae in L. marginata varied between 0.25 and 0.87%, but transmission rates of these larvae to fish were far higher, from 10.8 to 39.8%. The relative importance of ecological factors, host community structure and parasite specificity in determining circulation routes and transmission efficiencies are discussed.
Aerial respiration in the catfish, Eremophilus mutisii (Trichomycteridae, Siluriformes), in the Rio Bogota Basin, Colombia
Authors: Cala P.
Published: January 2006

Eremophilus mutisii uses the stomach for aerial respiration. Inspiration is during a rapid dash to and from the surface. Air‐breathing occurs in hypoxic and normoxic water, but is not obligatory. The evolution of a reduced swimbladder is associated with a benthic mode of life in E. mutisii.
Olfactory sensitivity of coho salmon, Oncorhynchus kisutch (Walbaum): can salinity play a role?
Authors: Rehnberg B. G. , Schreck C. B.
Published: January 2006

The importance of environmental ions to olfactory sensitivity in fish has not been clarified by electrophysiological experiments. We tested the ability of juvenile coho salmon, Oncorhynchus kisutch (Walbaum), to detect L‐serine after acclimation to either fresh water or sea water. The olfactory threshold was identical in the two waters, indicating that the sensitivity of olfaction was not affected by ionic content of the solutions bathing the sensory tissue.
Diet, food resource partitioning and feeding periodicity of two riffle‐dwelling fish species in a New Zealand river
Authors: Scrimgeour G. J. , Winterbourn M. J.
Published: January 2006

The diets and feeding periodicities of two small, riffle‐dwelling fish, the torrentfish, Cheimarrichthys fosteri, and the bluegilled bully, Gobiomorphus hubbsi, were investigated in an unstable, braided New Zealand river from May 1985 to April 1986. Aquatic insect larvae dominated diets of all fish and dietary overlap between species was high in 10 of 12 months. Nevertheless, the relative importance of prey items, as assessed by the index of relative importance (IRI), differed between species. Gobiomorphus hubbsi fed almost exclusively on larval Deleatidium (Ephemeroptera), whereas C. fosteri consumed a greater variety of prey items, with Deleatidium and trichopteran, elmid and chironomid larvae numerically dominant. A dietary switch from Deleatidium to chironomid larvae occurred in both species during December 1985, when total and relative abundances of mayfly and other benthic macroinvertebrate larvae were severely reduced by two consecutive floods. A diel sampling programme indicated that the feeding periodicity of the two species differed: C. fosteri was a nocturnal feeder, whereas G. hubbsi exhibited a strong crepuscular peak in feeding activity. Overall, the two fish partition their food resource weakly by consuming prey items in different proportions and sizes and more strongly by utilizing the food resource at different times.
The migration of ultrasonic‐tagged bream, Abramis brama (L), in Lake Constance (Bodensee‐Untersee)
Authors: Schulz U. , Berg R.
Published: January 2006

From May to October 1983 the migration of six adult bream was examined by long‐term ultrasonic tagging experiments. Two different migration types were observed: diurnal rhythmical migrations between the littoral and pelagic zones, and sporadic locomotions such as spontaneous excursions of several kilometers distance. At night, during their sojourn in the shallow littoral zone, bream feed intensively on benthic organisms; during their stay in the pelagic areas they presumably feed on zooplankton. Sporadic changes of place enable the bream to feed on locally abundant food resources. During the spawning season, migration contributes to successful spawning.
Light microscopical studies of chromosomes in embryos of cod, Gadus morhua L.
Authors: Stene A.
Published: January 2006

The chromosomes in the cells of 1–2‐day‐old cod embryos were studied using light microscopic techniques. The observations revealed slightly non‐synchronous cell divisions, with at least three different mitotic phases present in a 1‐day‐old embryo. Surprisingly high percentages of abnormal metaphases and anaphases were found in normal‐looking embryos. In the 2‐day‐old embryos, free‐lying nuclei were observed in the periblast zone. Chromosome studies of these nuclei revealed a cleavage pattern of the chromosomes which differed from that of the other cells.
The feeding and energetics of stream‐resident trout in winter*
Authors: Cunjak R. A. , Power G.
Published: January 2006

The feeding of brook and brown trout in a temperate Canadian stream was studied over two winters. Stomach analyses indicate that feeding continues throughout the winter. Both species had similar diets. Despite continuous feeding, condition factors declined significantly in early winter and remained low until the spring, suggesting an early‐winter depletion of lipid reserves. Energy (calorific) intake was similar in winter to that found in late summer or spring and therefore was not the cause of low winter condition. The derived energy from feeding was insufficient to offset the costs of maintenance metabolism in the early winter period, for both immature and recently spawned fish. It is suggested that stream‐dwelling trout suffer a metabolic deficit during acclimation to rapidly declining water temperatures in November/December. Such a phenomenon has important physiological implications for overwinter survival.
The influence of ration size and feeding frequency on ammonia excretion by juvenile Atlantic cod, Gadus morhua L.
Authors: Ramnarine I. W. , Pirie J. M. , Johnstone A. D. F. , Smith G. W.
Published: January 2006

Small groups of juvenile Atlantic cod, Gadus morhua L., were kept at 14°C in through‐flow tanks and were fed known quantities of a compounded diet of natural food. The cod were fed single and multiple meals with ration size in the range 0.5 to 4.1% of total wet fish body weight. Ammonia production in each feeding experiment was monitored continuously.

For single‐meal experiments, significant relationships were derived between ration size and (a) total ammonia excreted, (b) total exogenous ammonia excreted above endogenous excretion levels, (c) duration of the elevated phase of ammonia excretion, (d) maximum rate of ammonia excretion, and (e) time delay after feeding to reach maximum rate of ammonia excretion. Relationships between nitrogen loss as ammonia and nitrogen intake were examined and estimates of endogenous excretion rate and maintenance ration made.

Repetitive feeding resulted in cyclical variation in ammonia excretion. At the lowest ration size, ammonia excretion rates had nearly returned to the pre‐feeding level within 24 h. At higher feeding levels, the effect of each successive meal tended to be cumulative, resulting in increasingly higher ammonia excretion rates which only stabilized towards the end of the experiments.
The relative importance of the gills to ammonia and urea excretion in five seawater and one freshwater teleost species
Authors: Sayer M. D. J. , Davenport J.
Published: January 2006

The classic Homer Smith divided box experiment (Smith, 1929) was repeated upon five marine and one freshwater teleost species. Of the nitrogenous output (as ammonia and urea), 50–70% occurred in the head region for marine teleosts, while the freshwater tilapia studied excreted 90% from the head. Together with the data of Smith, these data indicate that nitrogen excretion by the gills is of lesser importance in marine teleosts than in freshwater species.

In the dab, Limanda limanda, the head, anus and urinary opening were all in the anterior chamber of the divided box, but 47% of nitrogen excretion still occurred in the posterior chamber, presumably across the skin. In the blenny, Blennius pholis, exposed to air, the head region accounted for 46% of urea elimination, and 26% of ammonia output.
Occurrence of the caryophyllid cestode Lytocestus parvulus Furtado, 1963 in Clarias batrachus (L.) in a tropical environment, Kedah, Malaysia
Authors: Zaman Z. , Leong T. S.
Published: January 2006

Clarias batrachus (L.) and C. macrocephalus Gunther were collected monthly between October 1982 and September 1984 from Pendang, Kedah, Malaysia. The caryophyllid cestode Lytocestus parvulus Furtado, 1963 was found in 37.7% of C. batrachus examined, with a mean intensity of 11.3. Infection of the cestode in C. macrocephalus was minimal, so detailed study was not attempted. In C. batrachus, no seasonal cycles of prevalence, mean intensity or maturation of the cestode were detected. The prevalence and mean intensity of L. parvulus decreased with increasing size of the fish. The first segment of the intestine was the preferred site where larger numbers of the cestodes and the greatest numbers of mature parasites were found. The number and maturation decreased towards the posterior end of the intestine.
Behavioural and physiological adaptations to a burrowing lifestyle in the snake blenny, Lumpenus lampretaeformis, and the red band‐fish, Cepola rubescens
Authors: Atkinson R. J. A. , Pelster B. , Bridges C. R. , Taylor A. C. , Morris S.
Published: January 2006

Observations have been made on the mode of burrow construction in the snake blenny, Lumpenus lampretaeformis, under laboratory conditions. It appears that head probing and lateral oscillations of the body are principally responsible for the excavation of the burrow which is completed within 24 h. The burrow structure has been analysed in detail, showing a mean depth of 7.2 cm with a maximum observed length of 73 cm, with most systems between 20 and 35 cm in length. Initially linear burrows with two openings are usually provided with a small side tunnel, giving the system a characteristic Y‐shape.

Burrow irrigation was investigated for the first time in L. lampretaeformis. The mean duration of burrow irrigation, by flexions of the tail of the fish, was 21 s with over 13 min h−1 spent in irrigating the burrow. The mean water displacement per irrigation period was 3.1 ml. The PO2 and PCO2 were measured in both surface water and within the burrow system of L. lampretaeformis. Surface water values for PO2 were high (> 150 Torr) and PCO2 low (<0.4 Torr). Hypoxic and hypercapnic conditions were measured in the burrow system itself, with PO2 values ranging between 57 and 129 Torr and PCO2 rising to > 1.3 Torr in some burrows.

A comparative study of Cepola rubescens burrows indicated similar surface water PO2 and PCO2 values as in L. lampretaeformis. Burrow water PO2 values ranged between 60 and 94 Torr, with PCO2 values as high as 1.5 Torr being recorded. These results are discussed in relation to the adaptation of both species to a burrowing lifestyle.
Aspects of the biology of Hemichromis bimaculatus from a small stream in Nigeria
Authors: Hyslop E. J.
Published: January 2006

The diet, condition factor, gonadosomatic index, length:weight and length:fecundity relationships of a Hemichromis bimaculatus population from the Kandole Shela, a small stream in northern Nigeria, are described. In dietary terms the species is a generalized invertebrate predator, chiefly taking food categories in relation to their abundance throughout the year. The pattern of egg maturation indicates that repeated spawning occurs, and it is argued that this is an appropriate reproductive strategy for the habitat occupied.
In vitro suppression of the phagocytic response of fish macrophages by tetracyclines
Authors: Wishkovsky A. , Roberson B. S. , Hetrick F. M.
Published: January 2006

Tetracycline (TC) and oxytetracycline (OTC) caused a dose‐dependent suppression of the chemiluminescence (CL) emitted by phagocytes from the kidney of rainbow trout, Salmo gairdneri, using zymosan or latex beads as the stimulus. Compared to the control response without antibiotics, partial but significant suppression was found after exposing the cells to OTC concentrations of 0.1–50.0 μg ml−1. Cells exposed to 100 or 500 μg ml−1 OTC showed CL responses below the base levels elicited by control cells. Comparable results were obtained with cells exposed to TC and stimulated by the same stimuli. The kinetics of the CL response and the suppressive effects of the antibiotics were similar in cells from individual fish but the magnitude of responses varied. No acclimation occurred following extended exposure to the drugs.
Sequential development and morphology of experimentally induced hepatic melano‐macrophage centres in Rivulus marmoratus
Authors: Vogelbein W. K. , Fournie J. W. , Overstreet R. M.
Published: January 2006

Formation of hepatic melano‐macrophage centres (MMCs) in Rivulus marmoratus was induced with the coccidian parasite Calyptospora funduli. Experimental infections were produced by feeding infected intestine and hepatopancreas from grass shrimp (Palaemonetes pugio) to individual parasite‐free fish. Livers of fish sampled 5–150 days post‐infection were examined histologically. Mild diffuse inflammation initiated during early merogony (5–8 days) consisted of eosinophilic granulocytes and heterophils. Liberation of merozoites (8–12 days) caused extensive hepatocyte degeneration and augmented leucocyte exudation. During gamogony (15–18 days) mononuclear phagocytes became a predominant component of the cellular exudate. Focal lesions, considered to be early MMCs, became apparent during early sporogony (20–25 days); they consisted of degenerating infected hepatocytes and inflammatory cells, and contained developing oocysts and degenerating macrogamonts, but no pigment. Early centres became visible grossly at 30 days as diffuse, yellow‐tan foci within the hepatic parenchyma. Pigment content increased progressively, but melanin was never a major component. Oocysts first elicited a granulomatous response between 40 and 50 days. The study suggests that MMC formation in this instance is an inflammatory process in which mononuclear phagocytes recruited from peripheral circulation play a dominant role. MMC development appears to be elicited by macrogamont degeneration, whereas granuloma formation is probably a response to oocysts.
Cutaneous tumour of northern pike Esox lucius L.: evidence for a monocytic neoplasm
Authors: Thompson J. S. , Kostiala A. A. I. , Miettinen M.
Published: January 2006

An epidemic of cutaneous tumours occurs in northern pike from the Åland Islands of Finland. Lymphocytes of pike could be triggered to synthesize DNA in vitro by mitogens. Tumour cells had a high basic metabolic rate and mitogens did not enhance their incorporation of 3H‐thymidine. High percentages of peripheral blood, spleen, and head kidney mononuclear cells were surface (SIg) and cytoplasmic (CIg) immunoglobulin‐positive by indirect immunofluorescence, using rabbit anti‐pike IgM antibodies. Lower but still substantially high percentages of SIg and CIg immunofluorescence were observed with mouse anti‐carp IgM antibodies. Tumour cells, however, were SIg‐ and Clg‐negative, suggesting that the neoplasm is not a B cell lymphoma or plasmacytoma. A majority of tumour cells exhibited an intense diffuse staining pattern for alpha‐naphthyl acetate esterase which was inhibited by sodium fluoride and was reminiscent of that in human monocytes. By electron microscopy (EM), the tumour cells were seen to be closely apposed with a lack of cell‐cell junctions, and characteristically contained groups of lysosomes and large numbers of cytoplasmic lipid droplets, which are features of histiomonocytic cells. Although the marker studies do not completely rule out a T‐lymphocytic origin, we suggest that the EM findings lend support for the view that the Åland pike neoplasm may be derived from the monocytic lineage.
Ontogeny of enzymatic activities in fed and fasting turbot, Scophthalmus maximus L.
Authors: Cousin J.C.B. , Baudin‐Laurencin F. , Gabaudan J.
Published: January 2006

The presence and localization of acid and alkaline phosphatase, non‐specific proteases, aminopeptidase, amylase, non‐specific esterase and lipase was investigated by histoenzymologic methods in fed and fasting turbot from day 1 to day 40 post‐hatching and compared with published data. Alkaline phosphatase and aminopeptidase activities were delected at day 1 in the distal region of the developing digestive tube. At day 3 (opening of the mouth) aminopeptidase and alkaline phosphatase activities were found all along the intestine. Sites of non‐specific esterase and protease activities became apparent in the digestive tract at days 2 and 3 respectively. Amylase was present in the exocrine pancreas at day 3 and in the lumen of the intestine at day 4. Acid phosphatase was active in the cellular structure surrounding the yolk stores and in the lipid droplets at day 1 and in the intestinal epithelium at day 3. Lipase was found at day 15 when the larvae metamorphose into juveniles.

All the investigated enzymes were detected in fasting animals, except for lipase. However, the intensities of the enzymatic activities were weaker in the fasting specimens relative to the fed specimens between days 7 and 10.
Comparative haematology of ten species of marine fish from Visakhapatnam Coast
Authors: Rambhaskar B. , Srinivasa Rao K.
Published: January 2006

A comparative study has been made of haematological parameters (erythrocyte numbers, leucocyte numbers, haematocrit and haemoglobin), erythrocyte indices (MCV, MCH and MCHC) and cytometric measurements (cell and nucleus) of 10 species of marine fish from the Visakhapatnam Coast, of which six are from harbour waters, three from rock pools and one from inshore waters. It is found that active fish have high values of erythrocyte numbers, haematocrit, haemoglobin and nucleo/cytoplasmic ratio and low values of leucocyte numbers and erythrocyte cytosome measurements. The most active of all is the inshore species Rastrelliger kanagurta depicting the haematological requirements of an active fish with high oxygen demand to meet the requirements of high metabolic rate. The other active fish such as Megalops cyprinoides and Mugil cephalus are intermediate, with the rock pool fish and Caranx carangus with low values of nucleo/cytoplasmic ratio at the other extreme.
Feeding ecology and daily food consumption of common sole, Solea vulgaris Quensel, juveniles on the French Atlantic coast
Authors: Lagardère J. P.
Published: January 2006

This study describes feeding rhythms in juvenile sole (0‐ and I‐groups) and differences in choice of prey according to age and feeding time. In the same biotype, 0‐group fish select amphipods or young opisthobranchs, whereas I‐group fish eat chiefly polychaetes such as Pectinaria koreni. The daily food consumption for juvenile soles in the field (T = 19.8°C) is estimated at 7% body dry weight in 0‐group and probably less in I‐group. When compared with estimates from previous methods or models, these rations are intermediate between estimates from Kuipers' method, with a gastric evacuation rate (R) per hour representing three times the amount of food in the stomach, and those from Elliott & Persson's model with R value around 1.46.
A study of the histology and morphology of the digestive tract of the sea‐bream, Sparus aurata
Authors: Cataldi E. , Cataudella S. , Monaco G. , Rossi A. , Tancioni L.
Published: January 2006

The anatomy and the histology of the digestive tract of young and adult sea‐bream is described from studies using light and scanning electron microscopy. The dentition in the juvenile (25–30 mm long) comprises all canine‐like teeth, to which plate teeth and transition elements are added in the adult.

The oesophagus shows a multi‐layered mucosa in the upper part, and single‐layered regions in the lower part. The multi‐layered regions are formed by epithelial cells, mucus‐secreting cells and by cells rich with eosinophilic granules.

The Y‐shaped stomach, clearly distinguishable, has a single‐layered columnar epithelium under which, in the cardiac and fundic portion, gastric glands, comprised of all similar cells, are present. The pyloric region is characterized by four caeca, to the base of which the ductus pancreaticus and the ductus hepaticus discharge.

The pancreas is composed of small masses spread along the upper intestine; in the adult, pancreatic infiltrations can be seen in the liver.

The intestine is short (relative length 0.5–0.6). The intestine epithelium consists of columnar cells intercalated with mucus‐secreting cells. A funnel‐like valve marks the passage to the intestine terminal region, characterized by a mucosa of cells with an abundance of vacuoles full of eosinophilic granules.
The diet and growth of 0‐group dace, Leuciscus leuciscus (L.), and roach, Rutilus rutilus (L.), in a lowland river
Authors: Weatherley N. S.
Published: January 2006

The diets of 0‐group dace and roach in the Lower Welsh Dee were studied by stomach contents analysis of seasonal and diel samples. During development, dace preyed on a sequence of food types, initially being mainly carnivorous then becoming nocturnally carnivorous and diurnally omnivorous. Roach showed a similar pattern, although after the first two months of life they were more herbivorous/detritivorous. From the variations in the diets, it is hypothesised that both species are limited by food. This receives circumstantial support from their poor observed growth. The food supply routes by which flow regulation of the River Dee could affect juvenile fish production are noted.
Influences of food particle size and dietary energy content on patterns of gastric evacuation in fish: test of a physiological model of gastric emptying
Authors: Jobling M.
Published: January 2006

The evacuation of food from the stomach is probably not a continuous smooth process but may occur in a pulse‐like (step‐wise) fashion. It is hypothesised that the pattern of emptying is influenced by feedback signals from receptors located in the upper intestinal tract and by factors affecting the rate of physical/chemical breakdown of the food particles. Mathematical functions used for describing evacuation patterns imply that emptying is continuous and they are, therefore, at best, only approximations. It was predicted that different mathematical expressions would give best fit to empirical data from gastric evacuation studies dependent upon the experimental conditions employed. An analysis of published data supported the predictions and revealed that an exponential function best described the evacuation of small, easily digested prey items, but a linear expression gave the best fit to data of the emptying of large food items. It is suggested that differences in surface‐to‐volume ratios between large and small food particles and the friabilities of different food types are important in determining the pattern of emptying. Whilst dietary energy content also appears to be an important factor in the governing of gastric evacuation, it appears that emptying pattern in fish species is rather less sensitive to changes in dietary composition than is gastric emptying in mammals.
Development of the activities of oxidative, glycolytic and muscle enzymes during early larval life in three families of freshwater fish
Authors: Hinterleitner S. , Platzer U. , Wieser W.
Published: January 2006

The development of the activities of oxidative (COX, CS), glycolytic (PFK, PK, LDH) and muscle enzymes (CK, MK, Pase) was studied in representatives of the families Coregonidae, Salmonidae and Cyprinidae, from hatching to an age of approximately 100 days. In addition, the activities of two enzymes of amino acid metabolism (GOT, GPT) were followed in rainbow trout and in roach.

Water content of fresh body weight and protein content of dry body weight decrease during the early larval period. Specific activities of the two oxidative enzymes decline, whereas those of glycolytic and muscle enzymes increase in all species.

A family‐specific event is the enormous increase in glycolytic and muscle enzymes from very low values in the early larva to very high levels in adult Coregonus sp. In rainbow trout, CS activity begins with a low‐level period lasting throughout the yolk‐sac period, whereas in the other species CS activity is high immediately after hatching.

Acclimation to either 15 or 20° C has no effect on the mass‐specific activities of PFK, M K, CK and Pase in roach and chub, but the former three enzymes appear to be strongly dependent on rearing conditions during the early larval period, whereas Pase is not.
A study on an herbivorous fish, Oreochromis niloticus L., diet and its quality in two Ethiopian Rift Valley lakes, Awasa and Zwai
Authors: Getachew T.
Published: January 2006

The natural food of Oreochromis niloticus from two Ethiopian Rift Valley lakes, Awasa and Zwai, was studied from the stomach contents. The food was analyzed to determine its chemical composition. The major consumed nutrient by the Awasa population was carbohydrate whereas in the Zwai population it was lipid. Microscopic identification revealed that Microcystis sp. and Botryococcus braunii are the dominant algae present in the food of the fishes from Lakes Zwai and Awasa, respectively. Assimilation efficiency of total organic matter is somewhat low, 28.3% for Awasa and 14.7% for Zwai populations. Both populations assimilated protein to a greater extent than other nutrients. In both lakes the quality of the food, expressed as a ratio of digestible protein to digestible energy, is adequate (>4 mg kJ −1) for growth, but the Awasa population appears to have higher growth and better condition.
Orientation behaviour of Lepomis macrochirus Rafinesque to salinity fluctuations
Authors: Peterson M. S. , Gustafson D. E. , Moore F. R.
Published: January 2006

The impact of the rate of salinity change has never been studied in primary freshwater fish occupying oligohaline marshes, where they are near their upper physiological limits. We conducted experiments on the bluegill sunfish, Lepomis macrochirus Rafinesque, to examine their orientation to salinity changes under winter temperature and photoperiod. We found significant difference in behavioural responses to rates of salinity change. The responses to the two flow rate changes indicate orthokinesis for ± 1.0‰ and −12.0‰ change h −1 treatments; however, a ‘closure’ type of response is apparent during +12.0‰ change h −1 treatment. These results indicate that bluegill sunfish respond behaviourally to salinity change, but reduce all overt activity when rate changes are unnatural and potentially lethal. It is apparent that behavioural and physiological responses are synergistic when the salinity exceeds a critical rate of change, which presumably is based upon the species' recent acclimatization history. Moreover, an orthokinetic response to the rate of salinity change may allow bluegill sunfish to move into and out of oligohaline marshes.
Diurnal changes in the territorial behaviour of the tilapia Oreochromis mossambicus (Peters)
Authors: Munro A. D. , Singh I.
Published: January 2006

The numbers of black, territorial, male tilapia in large tanks undergoes a clear diurnal cyclicity, with peak numbers seen in the afternoon. It is suggested that this cyclicity is functionally related to an observed spawning cyclicity.
Seasonal occurrence of the infectious stage of proliferative kidney disease (PKD) and resistance of rainbow trout, Salmo gairdneri Richardson, to reinfection
Authors: Foott J. S. , Hedrick R. P.
Published: January 2006

The seasonality of proliferative kidney disease (PKD) in rainbow trout, Salmo gairdneri Richardson, at the American River Hatchery, California was found to be primarily dependent on the presence or absence of the infectious stage in the water supply. This was determined by introducing sentinel trout into the hatchery water supply on a monthly basis, followed by their transfer to the laboratory for subsequent holding in 18° C, pathogen‐free water for one month prior to examination. These exposures demonstrated that infections were obtained from April through October at ambient temperatures 12–20° C. Trout which had recovered from clinical infections were found to be resistant to reinfection. Resistance was induced by active infection and not just previous exposure to the infectious stage. Trout surviving PKD were also found to harbour later sporogonic stages of the parasite for at least one year following initial infection, but fully formed spores, as judged by well‐developed valves, were not observed.
Effect of experimental conditions on the stomach evacuation of Coregonus lavaretus L.
Authors: Röusch R.
Published: January 2006

The gastric evacuation of juveniles of Coregonus lavaretus L. fed on living Daphnia pulicaria was investigated. Three successive stages of stomach evacuation were observed when one meal per day was given: (i) a lag phase between the end of food intake and the beginning of stomach evacuation, (ii) a linear reduction of stomach content, (iii) a long residence time for food relics in the stomach. The initial stomach content and the stomach evacuation time are correlated positively. The stomach content increased during feeding when three meals day −1 were provided and it decreased when no food was available. During the course of an experiment the highest stomach content found increased with increasing daly ration. Excess feeding resulted in a low stomach content similar to that found with rations about 30–50% of the maximum daily food intake. Therefore the daily food intake cannot be determined by the single parameter of stomach content alone. Identical initial stomach contents showed significantly higher stomach evacuation rates under three meals day−1 conditions than under one meal day−1 conditions.
Haematological and haematopoietic response to acid stress in an air‐breathing freshwater fish, Channa punctatus Bloch
Authors: Dheer J. M. S. , Dheer T. R. , Mahajan C. L.
Published: January 2006

Response of Channa punctatus to acidic water was studied by exposing fishes to pH 3.5, 4.5, 5.5 and 6.5 for 6 weeks. Growth and mortality data indicated increasing stress as the acid level in the ambient water increased. While no mortality was recorded at pH 6.5, a distinct loss of weight compared to continuous gain in body weight in control fish indicated stress. As the pH level decreased, the rate of loss in body weight increased accompanied by mortality which rose to as high as 60% within 3 weeks in fishes exposed to water at pH 3.5.

Haematological investigations confirmed the general stress indicated by growth and mortality data. Thus. RBC and related values indicated overall polycythemia. However, eosinophils, basophils. and large and small lymphocytes showed a distinct fall in number as compared to the control.

Correlated haematopoietic studies revealed that both the initial and penultimate stages in RBC and neutrophil development recorded an increase parallel to that observed in peripheral blood, but intermediate stages, probably because they were unable to keep pace with the fast turnover, showed a relative decrease.

Biochemical investigations showed an increase not only in blood glucose level but also in liver glycogen content. However, there was a significant decrease in muscle glycogen reserves.

The significance of these changes is discussed.
Male aggression and female mate choice in the threespine stickleback, Gasterosteus aculeatus L.*
Authors: Ward G. , FitzGerald G. J.
Published: January 2006

A laboratory study of female G. aculeatus revealed no conclusive evidence of active female mate choice on the basis of male aggression levels. However, highly aggressive males failed in 95% of all choice tests. The less aggressive ‘chosen’ males were generally successful again in subsequent trials with the same female, and certain males were consistently successful with different females. Females exhibited an increased readiness to spawn at the end of the reproductive season, although the same males were usually selected again.
Feeding selectivity of four species of sympatric stickleback in brackish‐water habitats in eastern Canada
Authors: Delbeek J. C. , Williams D. D.
Published: January 2006

Although sympatric populations of sticklebacks occur commonly along the north‐eastern coast of North America, very few studies have considered the interspecific relationships within such populations. This paper investigates prey selectivity, feeding behaviour and potential prey availability within sympatric populations from five brackish‐water sites in New Brunswick. Differences between the diets of species from different sites were related to differences in the range of prey available. Fish collected from sites with abundant aquatic vegetation consumed greater numbers of prey than those from vegetation‐poor sites. The proportions of prey types eaten by both adults and juveniles reflected prey species abundance at the different sites; thus shifts in diet over time were found to be related to changes in the abundance of potential prey and not to shifts in prey preference on the part of the fish. The size of prey consumed was related to mouth size; adult and juvenileGasterosteus wheatlandi, having the smallest mouths, consumed the smallest prey. Differences in prey size detected in the four species studied were due to differences in the types of prey consumed. Laboratory experiments on feeding behaviour showed that adultApeltes quadracusandPungitius pungitiuswere more efficient at capturing benthic prey than wereGasterosteus aculeatusandG. wheatlandi.Competition for food is thought not to occur in these populations, because of the abundance of potential prey and the morphological constraints on feeding behaviour.
Factors limiting fish populations in the Loch Fleet system, an acidic drainage system in south‐west Scotland
Authors: Turnpenny A. W. H. , Dempsey C. H. , Davis M. H. , Fleming J. M.
Published: January 2006

Loch Fleet is an oligotrophic upland lake in Galloway, south‐west Scotland. It once supported a brown trout, Salmo trutta L., sport fishery with low annual catches (< 150 fish year −1) but catches declined markedly after 1950 and no fish were caught after 1975. Diatom records for the lake sediments indicate acute acidification since 1975, pH changing from c. 5–8 to 4–6.

In 1984 a project was set up at Loch Fleet to investigate techniques of acidity mitigation, with a view to restoring fisheries in this and similarly affected waters. An underlying assumption of the project was that fish had been lost as a direct result of acidity and associated factors. Studies were therefore undertaken during a 2‐year baseline period (1984–1986) to validate this assumption.

Fish surveys using a variety of techniques (gill‐netting, trapping, electrofishing) confirmed that trout were absent from the Loch and its afferent streams, and also from its main outlet stream, the Little Water of Fleet, for a distance of 7 km downstream. Trout were present below this point but are prevented from passing upstream by a 5‐m waterfall. Eels, Anguilla anguilla L., were present throughout the Little Water of Fleet, though not in the Loch itself. Population densities of both species were low, with less than 7 eels and 5 trout per 100 m2.

Survival studies using brown trout ova and yolk‐sac fry indicated that conditions in the Loch and its afferent streams were acutely toxic to these stages as a result of the low pH (pH 4.5), low calcium (I mg l−1) and high aluminium concentrations (200 μg 1 −1 total Al, 60 μg 1 −1 inorganic monomeric Al). Trout fingerlings could survive these conditions in short‐term tests (9 days) but, in chronic exposure tests lasting up to 180 days carried out in situ in streams adjoining the loch, no fish survived this period. This toxicity was eliminated in experiments where pH was raised to 5.4 by KOH addition.

It is concluded that the loss of the brown trout fishery at Loch Fleet occurred as a direct result of acidity and related factors, probably acting in the first instance on the sensitive intra‐gravel ova and yolk‐sac fry stages, leading to recruitment failure.