bluuebunny/crossref_metadata_2025 huggingface dataset:
Reproductive effort and efficiency in the female common goby, Pomatoschistus microps (Krøyer) (Teleostei: Gobioidei)
Authors: Rogers S. I.
Published: January 2006

Reproductive effort and efficiency are terms which together help to describe the reproductive investment of spawning fish. In this paper they are applied to a small and abundant inshore fish, the common goby, Pomatoschistus microps (Kroyer), based on data collected from the wild, and by modelling likely breeding patterns. Wet calorimetry was used to determine the energy content offish tissue, and this allowed reproductive effort to be expressed as both an energy and a weight ratio of gonad to somatic body. The gonadosomatic index (GSI) calculated as an energy ratio was greater than that calculated as a dry “weight ratio”. For ripe females the GSI (dry weight) at the onset of breeding was 67.5%. Theoretical and observed values of the maximum number of egg batches laid by a single female during a 16‐week breeding season are 9‐10, and this corresponds to a total caloric investment of almost 12 kJ. Estimates of the reproductive efficiency, using the dietary energy content during the breeding season, range from 28.2% to a maximum of 44.0%. These values are among the highest calculated for a fish species, and are in keeping with the long and intensive breeding strategy observed in the wild population.
Olfactory sensitivity of the herbivorous grass carp, Ctenopharyngodon idella, to amino acids
Authors: Johnsen P. B. , Zhou H. , Adams M. A.
Published: January 2006

The olfactory sensitivity of a herbivore, the grass carp, Ctenopharyngodon idella, to ten amino acids was investigated using electrophysiological recording techniques. Underwater electroolfactogram recordings increased exponentially with logarithmic increases of stimulus concentration from threshold to 1 × 10−3 m. Calculated detection thresholds ranged from 1 × 10−7.15 m to 1 × 10−8.7 M and are similar to those previously reported for carnivorous fish species. The relative stimulatory efficacy (RSE) of the ten amino acids determined at 1 × 10−4 M revealed five groups of stimuli, with cysteine the most stimulatory and proline the least. Measures of amino acid RSE did not differ significantly from those of previously studied carnivores, except for arginine. Grass carp showed strong responses to this compound, whereas it has produced only limited responses in carnivores. Differences in the responsiveness of herbivores and carnivores were not observed, suggesting that feeding niche segregation is probably not facilitated by differential olfactory sensitivities to feeding stimuli.
Endurance at intermediate swimming speeds of Atlantic mackerel, Scomber scombrus L., herring, Clupea harengus L., and saithe, Pollachius virens L.
Authors: He P. , Wardle C. S.
Published: January 2006

Endurance and swimming speed were measured in mackerel, herring and saithe when they were induced by the optomotor response to swim at prolonged speeds along a 28‐m circular track through still water in a 10‐m diameter gantry tank. The maximum sustained swimming speed (Ums was measured as body lengths per second (b.l.s−1) for each species and for saithe of different size groups. Herring with Ums of 4.06 b.l.s−1 (25.3 cm, 13.5°C) were the fastest, mackerel Ums was 3.5 b.l.s1 (33 cm, 11.7°C) and saithe (14.4°C) showed a size effect where Ums at 25 cm was 3.5 b.l.s1 and at 50 cm 2.2 b.l.s1. When swimming at speeds higher that Ums, all three species showed reduced endurance as speed increased. How the curved track reduces the swimming speed is discussed.
Studies on the uptake of (14C) amino acids derived from both dietary (14C) protein and dietary (14C) amino acids by rainbow trout, Salmo gairdneri Richardson
Authors: Cowey C. B. , Walton M. J.
Published: January 2006

Previous studies have shown that rainbow trout fed on diets containing whole protein have superior growth rates compared to fish fed on diets of similar amino acid composition but containing a high proportion of free amino acids. The influence of several nutritional factors on the uptake of radioactivity from food pellets containing either [U‐I4C] protein or [U‐14C] amino acids into the systemic blood of trout has been investigated. The time taken for radioactivity in the free amino acid fraction of blood to reach a peak after a meal containing [U‐14C] protein had been given was much shorter, and the level of radioactivity in the blood higher, in trout with almost empty stomachs than in fish with almost full stomachs; uptake of radioactivity into blood amino acids was also more rapid and reached much higher concentrations when pellets containing [U‐14C] amino acids were fed than when [U‐14C] protein was fed. Incorporation of radioactivity into blood protein continued for a much longer period and reached higher levels when a pellet containing [U‐14C] protein was fed than when a pellet containing [U‐14C] amino acids was fed. Previous dietary history (low or high protein intake) did not appear to affect the rate of absorption of amino acids from either protein or free amino acid pellets. The uptake rates from pellets containing free amino acids could be slowed by mixing the dietary amino acids with albumin. The distribution, postabsorption, of radioactivity in the different fractions of blood and liver suggested that incorporation of carbon residues into glycogen and lipid from an amino acid diet was greater than from a protein diet. The converse was true of incorporation of radioactivity into tissue protein.
Digestive efficiency and nutrient composition gradient in the gut of Oreochromis niloticus L. in Lake Awasa, Ethiopia
Authors: Getachew T.
Published: January 2006

Assimilation efficiencies were measured by comparing the amount of nutrient in the food and faeces of fish from the natural environment. The comparison of nutrients was made in relation to reference markers: ash, hydrolysis‐resistant ash (HRA) and hydrolysis‐resistant organic matter (HROM). Assimilation efficiencies of nutrients computed using ash and HRA as reference markers were significantly (P < 0.05) lower than those measured with HROM; digestibility estimates of protein were the least influenced by the type of marker used. Generally, HROM appears to be the most suitable reference marker for a digestibility study in an herbivorous fish such as Oreochromis niloticus.

Nutrient composition gradient examined by analysis of stomach, intestinal and rectal contents showed that digestion of all nutrients was completed when the food passed two‐thirds of the way through the length of the intestine. Most of the nutrients were significantly (P < 0.05) affected by the processes of digestion and assimilation in different sections of the gut, and a decline in the quantity of nutrients was obvious towards the rectum.
Feeding habits of the Lessepsian migrant Siganus luridus in the eastern Mediterranean, its new environment
Authors: Stergiou K. I.
Published: January 2006

The feeding habits of the Lessepsian migrant Siganus luridus in the eastern Mediterranean (Kastellorhizo Isle, Dodecanese, Greece) are examined. The stomach contents of 209 specimens, 131–250 mm total length, collected by bottom trammel nets, April 1985 July 1986, were analysed. Feeding intensity was high, although it significantly declined during the spawning period in summer. Siganus luridus feeds on a diverse assemblage of benthonic algae including 24 genera (seven green, eight brown and nine red algae) contributing 84.4% by weight (green algae 3%, brown 70.3%, red 11 %). Posidonia oceanica, diatoms, hydrozoa and sand were also found in the stomachs examined. On an annual basis, Dictyota sp., Cysloseira sp., Sphacelaria sp., Gelidium sp., Dictyopteris membranacea, Kuckuckia spinosa and Padina pavonica predominated in the diet. Diet overlap, on a weight basis, indicated a similar food spectrum during spring and summer which was different from that in autumn.

The high feeding intensity of S. luridus during the year (except for the spawning period), its nonselective euryphagous nature, its high competitive potential, and its position in the food web of the eastern Mediterranean ecosystem are important characteristics that, along with suitable oceanographic and ecological conditions for the development and survival of young stages, have enabled the successful establishment and build‐up of the population of this Lessepsian migrant in its new environment. Possible competitive implications in the eastern Mediterranean ecosystem are also discussed.
Cellular responses in the skin of carp maintained in organically fertilized water
Authors: Iger Y. , Abraham M. , Dotan A. , Fattal B. , Rahamim E.
Published: January 2006

Carp were maintained for a month in well‐oxygenated water fertilized with organic manure. During the experiment the thickness of the epidermis increased from 140 to 180 urn. Fish from pulluted water were dark, an adaptation to the dark, turbid water. The number of cytoplasmic extensions from the dermal pigment cells increased continuously from 6 per unit length in control specimens to over 80 in the experimental specimens at the end of the month. Apart from background adaptation, this activity of the pigment cells may be a stress reaction. Holocrine secretion of mucous cells was pronounced, with a progressive reduction on the first day after the transfer, to almost total disappearance of this cell type from the epidermis after 3 days. A thick mucous coat became visible on the outside of the epidermis. Eight days after the transfer, a slightly subnormal mucous cell count was observed, indicating the development of newly differentiated mucous cells. This subnormal cell count lasted until the end of the experiment. The pavement cells actively secreted glycocalyx, while newly differentiated pavement cells with still‐intact secretory granules replaced the exhausted cells at the epidermis surface throughout the experimental period. Granulocytes, both baso‐ and neutrophilic, as well as macrophages, infiltrated the epidermis; despite the high bacterial count in the water, no bacteria were observed either inside the skin or entangled in the mucous coat.
A special pattern of haem catabolism in a marine fish, Clinocottus analis, with green blood plasma
Authors: Fang L.‐S. , Bada J. L.
Published: January 2006

The mechanism responsible for the green colouration of blood plasma in the marine fish Clinocottus analis was studied. Biliverdin in the blood of this fish is unconjugated and is tightly bound to albumin‐like proteins. Hydrophobic interactions and hydrogen bonds contributed more than electrostatic interactions to the binding between the bile pigment and the carrier protein. This special biliverdin protein complex was not metabolized by biliverdin reductase, and prevented the further metabolism or excretion of the bile pigment. This accounts for the normal green colouration of the blood plasma in this fish.
Annual changes in the testicular activity of the river sculpin, Cottus hangiongensis Mori, with emphasis on the occurrence of aberrant spermatids during spermatogenesis
Authors: Quinitio G. F. , Takahashi H. , Goto A.
Published: January 2006

Annual changes in the spermatogenetic activity of the testis were studied histologically in the river sculpin. Coitus hangiongensis, sampled monthly from a river in southern Hokkaido, Japan. A pair of sperm reservoirs, consisting of many anastomosing lacunae, was present along the dorsomedian edge of the paired testes, and functioned also as a sperm‐transporting system instead of the typical sperm duct. Spermatogenesis occurred actively in August, yielding an increasing number of mature spermatozoa in October. This process advanced, but slowly during the succeeding winter months, until March. The testis became functionally mature during the spawning period in April and May. In July, small numbers of spermatocytes were found to have appeared already, which indicated a relatively short period of post‐spawning testicular regression. In November, germinal cysts containing aberrant binuclear spermatids began to appear within the seminal lobules. The paired nuclei of aberrant spermatids gradually enlarged, and the cells were released into the lumina of the seminal lobules simultaneously with the release of mature spermatozoa from the germinal cysts. During the functional maturity stage, lumina of seminal lobules which had expelled mature spermatozoa to sperm reservoirs became filled with these abnormal bodies. Discussion includes the occurrence of aberrant spermatids which resulted in the formation of ‘spermatid masses’ as has been described in other cottids.
Evaluation of the separation of triploid and diploid grass carp, Ctenopharyngodon idella (Valenciennes), by external morphology
Authors: Bonar S. A. , Thomas G. L. , Pauley G. B.
Published: January 2006

The external morphology of diploid and triploid grass carp was studied to determine whether the two types could be separated by differences in external characteristics. In a comparison of 27 measurements, six scale counts and five fin formulae from two stocks of diploid and triploid fish obtained from commercial producers, analysis of covariance and discriminant analysis indicated a classification accuracy of only 65–85%. Clearly, triploid grass carp differentiated by external morphology alone should not be stocked into waters where diploid fish are illegal or would cause management problems.
Mate choice, egg cannibalism and reproductive success in the river bullhead, Cottus gobio L.
Authors: Marconato A. , Bisazza A.
Published: January 2006

The seasonal pattern and individual variation in reproductive success was studied in a population of the river bullhead, Cottus gobio L. Female fecundity and male reproductive success were correlated with body size. Large males were found to breed early in the season when most of the large females spawned. The diameter of eggs found in male nests indicates that females tend to mate with males larger than themselves. The analysis of stomach contents suggests that guarding males cannibalize some of their own eggs. During parental care, the rate of filial cannibalism increases as guarding male body condition deteriorates.
The role of fish studies in estuarine pollution assessment
Authors: Elliott M. , Griffiths A. H. , Taylor C. J. L.
Published: January 2006

The environmental quality objective and standards (EQO/EQS) approach to controlling and assessing estuarine pollution is described together with details of the information necessary to assess the health of the fish populations and determine whether the EQO/EQS are being met in an estuary. These concepts are illustrated by examples from the Forth estuary, Scotland, involving studies of the ecology, pathology, biochemistry and contaminant bioaccumulation of fish in relation to the benthos, water quality and anthropogenic influences.
First results with a new estuarine fish tracking system
Authors: Solomon D. J. , Potter E. C. E.
Published: January 2006

A ‘sonar buoy’ tracking system has been developed at the MAFF Fisheries Laboratory based upon acoustic transmitting tags and relay units which retransmit the pulsed acoustic signal as a radio signal. The output from several such ‘sonar buoys’ is monitored by a single automatic recording station on the shore. The system has been used on salmon in the estuary of the River Fowey in Cornwall, providing useful data on the behaviour of returning adults before they enter the river. The tags also transmit a radio frequency signal to allow tracking in the river itself. Of fourteen fish tagged in 1985, six were recorded entering the river between 12 h and 41 days after being released. Another fish was recaptured in a coastal net 160 km to the east. These few preliminary results indicated two distinct patterns of behaviour: one fish remained in deep water in the lower estuary for several days, often lying near moored ships or jetties; at other times fish made extensive excursions up the estuary with the tide, usually returning with the ebb.
Behaviour of adult Atlantic salmon, Salmo salar L., in the estuary of the River Ribble in relation to variations in dissolved oxygen and tidal flow
Authors: Priede I. G. , Solbé J. F. de L. G. , Nott J. E. , O'Grady K. T. , Cragg‐Hine D.
Published: January 2006

Twenty adult returning salmon were tracked in the estuary of the R. Ribble using acoustic oxygensensing transmitters during summer when a pronounced dissolved oxygen (DO) sag develops. Excluding two mortalities, 75% of these fish left the estuary to sea. Fish in the estuary moved to and fro with the tides over a 10 km amplitude experiencing cyclical changes in DO. Fish movement was inhibited below 40% of air saturation value (ASV) DO, and there was evidence of avoidance of DO below 55% ASV. The high rate of loss of fish to sea suggests that many of the fish in the estuary are non‐Ribble fish en route to other rivers. Adverse conditions in the Ribble therefore are likely to affect stocks in adjacent rivers.
Ultrastructural changes in the muscle tissue of Clupea harengus L. larvae induced by acid pH
Authors: Bahgat F. J. , King P. E. , Shackley S. E.
Published: January 2006

The pH of sea water remains relatively constant at 7·8–8·3 but, in lower salinity environments, inshore and in estuaries, localized changes in pH can be caused by effluent discharge. Eggs and larvae of the Atlantic herring, Clupea harengus L., can be spawned and develop in these areas and thus may be exposed to acidic conditions. Larvae hatched from eggs exposed to sea water at pH 7·0 or 6·0 or 5·2, in comparison to controls, showed a significant reduction in the mean volume of muscle fibres and mitochondria, degeneration of mitochondrial cristae and swelling of the sarcoplasmic reticulum. These sublethal ultrastructural changes would cause reduced metabolic activity and loss of contractility leading to reduced swimming and equilibrium ability with consequent loss of viability.
The parasite faunas of meso‐ and bathypelagic fishes of Norfolk Submarine Canyon, western North Atlantic
Authors: Gartner J. V. , Zwerner D. E.
Published: January 2006

A total of 668 specimens representing 18 species of meso‐ and bathypelagic fishes collected from the western North Atlantic were examined for parasites. Seventeen species and 39.1% of the specimens harboured at least one type of parasite. The highest number of parasite taxa recovered from a single fish species was seven. Host species had overall infection prevalences ranging from 10.0 to 88.9% of the specimens examined. Cestodes were most common (22.8% of all specimens examined), followed by fungi (6.6%), nematodes (6.1%) and digenetic trematodes (4.9%). Mesopelagic fishes showed a greater prevalence of infection (49.1%) than bathypelagic fishes (28.9%). Most parasites recovered were immature; however, based on the presence of adult and postlarval stage parasites, definitive and second intermediate host status is suggested for at least three fish species (Nemichthys scolopaceus, Nessorhamphus ingolfianus and Eurypharynx pelecanoides). The presence of the cestode Nybelinia and Anisakis‐lype nematodes among a number of host species may have been due to predation on the euphausiid Nematoscelis, which was found in the stomachs of all host species infected by these two parasite taxa. Higher overall infection prevalences among host species were found than have been previously reported for mid‐water fishes and it is possible that this may be a function of near‐bottom presence of the fishes over the continental slope. It is suggested that the low prevalence of parasites within meso‐ and bathypelagic fishes when compared to benthic and shallow‐water species reflects the lower overall energy of, and reduced probability of host‐to‐host transfer in, the deep‐sea pelagic ecosystem.
Immunological importance of the second gut segment of carp.
Authors: Rombout J. H. W. M. , Bot H. E. , Taverne‐Thiele J. J.
Published: January 2006

Lymphocytes, plasma cells, granulocytes (three to four types), macrophages and monocyte‐like cells were ultrastructurally distinguished in the intestinal mucosa of carp. Neutrophilic granulocytes and lymphoid cells were present in and under the epithelium throughout the gut. In contrast to macrophages which dominated in the epithelium of the second segment, basophilic and eosinophilic granulocytes (and their intermediates) were mainly found in the connective tissue of the first segment. Applying monoclonal antibodies against serum immunoglobulin (Ig) in an immunogold technique, only a minority of lymphoid cells appeared to be Ig‐immunoreactive at their external membrane, suggesting the presence of many more T than B cells in the intestinal mucosa. Except for cells which resembled immature plasma cells, plasma cells did not show, or hardly showed, Ig at their surface. In contrast with the head kidney, plasma cells with an Ig‐immunoreactive cytoplasm were scarce in the intestinal mucosa. As mucosa plasma cells were regularly found with the electron microscope, they possibly contain another class of Ig. Macrophages and monocyte‐like cells were also found to be Ig‐immunoreactive, suggesting the presence of immune complexes at their external membrane. The immunological significance of B‐ and T‐like lymphocytes next to immune complex‐binding and antigen‐presenting macrophages in the second gut segment is discussed.
Digestive enzymes in larval Coregonus lavaretus L.
Authors: Segner H. , Rösch R. , Schmidt H. , von Poeppinghausen K. J.
Published: January 2006

Using histochemical methods, morphofunctional aspects of the alimentary tract of larval coregonids were investigated. Larvae of Coregonus lavaretus were reared for 34 days with either zooplankton or one of two dry diets. Ontogeny, localization and diet‐related modifications of the following enzymes were examined: trypsin (luminal digestion), aminopeptidase, maltase, alkaline phosphatase (brush border‐bound digestion) and unspecific esterase (intracellular nutrient processing). All of the enzymes studied were present in 13‐day‐old larvae. Except for the intracellularly located unspecific esterase, there was an ontogenetic enhancement of enzyme staining intensities accompanied by a significant increase in the volume of the intestinal mucosa. Enzyme activities differed within and between intestinal regions. This finding suggests that a spatial gradient of nutrient breakdown and absorption already exists in the morphologically and physiologically incompletely developed digestive system of larval coregonids. Digestive enzyme activities were modified in response to the dietary regimen. There was no obvious correlation between enzymic response and growth performance of the larvae.
The feeding, growth and behaviour of juvenile cod, Gadus morhua L., in cold environments
Authors: Brown J. A. , Pepin P. , Methven D. A. , Somerton D. C.
Published: January 2006

Most studies on feeding‐related activities of fish in cold water (0° C) have not used eurythermal species or examined a broad suite of activities. In this study we report on the feeding, growth, behaviour and conversion‐efficiency of 0 + Atlantic cod in response to water temperature and food availability. In one experiment, activity, opercular beat and growth decreased with decreasing temperature over the range 8·3–0·6° C. However, the conversion efficiency increased with decreasing temperature, a result partly explained by the relative change in activity and opercular rate. In another experiment, temperature had a linear effect on growth in cod fed different food rations. Both food availability and temperature were found to influence growth in group 0 + cod. The specific growth rate of cod in this experiment exceeded 2% day‐1. Growth data collected from cod sampled in the field during the cold‐water period showed a progressive increase of mean length over the season. Overall, these results demonstrate that 0 + cod have adapted to life in cold‐water environments, in contrast to adult cod which mostly inhabit warmer environments.
Histological, fine‐structural and histochemical differences in the testicular glands of gobiid and blenniid fishes
Authors: Seiwald M. , Patzner R. A.
Published: January 2006

The testicular gland (t.g.) is a glandular tissue situated adjacent to the testis of blenniid and several gobiid species. In the present study the t.g. of Blennius pavo Risso and Gobius niger L. were compared by histological and histochemical methods. In B. pavo the spermatozoa have to cross the t.g. to reach the vas deferens and thus they come into contact with the gland cells, whereas in G. niger the vas deferens is situated between the testis and the t.g. The fine structure and histo‐chemistry of the t.g. cells reveal that in B.pavo the cells of the t.g. have exocrine as well as endocrine functions. The t.g. cells of B. pavo contain large amounts of lipids, form a secretion containing acid mucopolysaccharides, show positive reaction for acid phosphatase, and some cells stain for 3β‐HSD and G6PD. The function of the t.g. of G. niger is exclusively endocrine. Characteristics of the gland cells of this species are well developed smooth ER and tubulovesicular or paracristal‐line mitochondria. The stainings for 3β‐HSD, G6PD and UDPGD give strong positive results in the whole t.g., indicating the presence of steroids and steroid glucuronides.
Amount and distribution of biochemical‐genetic variation among wild populations and a hatchery stock of Atlantic salmon, Salmo salar L., from north‐east Ireland
Authors: Crozier W. W. , Moffett I. J. J.
Published: January 2006

Tissue samples from a total of 617 Atlantic salmon from seven locations in north‐east Ireland were electrophoretically examined for genetic variation at 28 enzyme loci. Patterns of allelic variation at eight polymorphic loci indicated the existence of genetic differentiation within, as well as among, river systems. This suggests the presence of localized genetically differentiated populations of salmon in N. Ireland. Temporal variation in allelic frequencies was tested among three year classes of wild R. Bush salmon and found to be insignificant compared to the spatial variation. Examination of equivalent year classes of R. Bush hatchery‐reared salmon displayed significant temporal variation at five loci, and significant departures from Hardy‐Weinberg equilibrium at two loci. Heterozygosity was not reduced in the Bush hatchery population (mean 4.3%) compared to the wild populations sampled (range, 2.9‐5.4%; mean, 4.2%). These results are discussed in relation to management of wild populations and maintenance of hatchery stocks.
Pomphorhynchus laevis (Müller) in the flounder, Platichthys flesus L., in the tidal River Thames: population structure, microhabitat utilization and reproductive status in the field and under conditions of controlled salinity
Authors: Munro M. A. , Whitfield P. J. , Diffley R.
Published: January 2006

The infection of R. Thames flounders, Platichthys flesus L., at Fulham by the acanthocephalan parasite Pomphorhynchus laevix (Müller) is described in terms of parasite population structure, life‐cycle organization, reproductive biology and host microhabitat utilization. The parasites demonstrated 100% prevalence in this tidal but essentially freshwater locality (intestinal intensity 34.47) and were overdispersed in the flounder population (variance/mean ratio = 10.39, k= 1.04). Overall about 11% of the worms occurred in peritoneal cavity sites, the remainder being firmly attached to the gut wall in the posterior region of the intestine and rectum. The P. laevis populations were reproductively active, demonstrating that the flounder acts as a significant final host in this locality. Viable larval stages were identified in Gammarus zaddachi Sexton, a predominantly estuarine amphipod, indicating that P. laevis is likely to be able to complete its life cycle at Fulham. Over half the female parasites examined were gravid and many of the non‐gravid worms were inseminated but had not yet started egg production. The proportion of females gravid, the number of ovarian balls and the number of eggs in gravid females was seen to increase with worm size. Both the identity of the intermediate host and the reproductive status of P. laevis in the Thames flounders differ from the Pomphorhynchus/flounder system studied by Kennedy (1984) in the R. Avon, suggesting that the two P. laevis populations may belong at least to discrete subspecies or strains. Parasites in flounders maintained under laboratory conditions in fresh water, 50% sea water and 100% sea water showed similar population, microhabitat and reproductive characteristics to those observed in the field. This suggests that increased salinity has a negligible effect on established parasites in the short term, and therefore that salinity may not form a barrier to the survival and dispersal of the R. Thames parasite when the flounders return to sea.
The immune response of wild rainbow trout, Salmo gairdneri Richardson, to naturally acquired plerocercoid infections of Diphyllobothrium dendriticum (Nitzsch, 1824) and D. ditremum (Creplin, 1825)
Authors: Sharp G. J. E. , Pike A. W. , Secombes C. J.
Published: January 2006

Natural infections of rainbow trout with two species ofDiphyllobothrium result in a host inflammatory response encapsulating the plerocercoid. The encapsulating cyst, observed by light and electron microscopy, comprises leucocytes, fibroblasts and collagenous connective tissue and is infiltrated with a blood vascular network. An indirect immunofluorescence technique and enzyme‐linked immunosorbant assay (ELISA) have shown that specific antibodies are elicited by the fish host to these Diphyllobothrium spp. These antibodies have been semi‐quantitatively measured by ELISA and correlated with worm burdens in individual fish.
Otolith resorption induced by anaerobic stress in the goldfish, Carassius auratus
Authors: Mugiya Y. , Uchimura T.
Published: January 2006

To examine otolith resorption induced by anaerobic stress, 45Ca‐prelabelled goldfish, Carassius auratus, were kept in oxygen‐deficient ambient water (O2 < 0.5 .1 1−1, 26° C) for 2 days and otoliths (asterisci) were analysed for 45Ca retention. In a second experiment, fish were anaerobically stressed for 2 days, and then received a single intraperitoneal injection of 45Ca. They were maintained under stress for one more day and killed to examine 45Ca deposition in otoliths. Plasma was analysed for total and radioactive calcium. Otoliths (lapilli) were examined for stress‐induced check formation by scanning electron microscopy (SEM).

Stress significantly reduced plasma calcium levels and the rate of calcium retention in otoliths, which was calculated from the 45Ca specific activity of the plasma. On the other hand, the rate of calcium deposition in otoliths was the same in the stressed as in the control fish. SEM observation revealed that the applied stress resulted in a check formation in otoliths. These results indicate that a 48‐h stress of oxygen deficiency induces calcium resorption in otoliths.
Low efficiency of dietary carbon and nitrogen conversion to growth in an herbivorous coral‐reef fish in the wild
Authors: Polunin N. V. C. , Brothers E. B.
Published: January 2006

Annual ingestion and body growth have been estimated for average‐sized adult (mean s.l. 62.7 mm) jewel damselfish. Plectroglyphidodon lacrymatus (Quoy et Gaimard), on a shallow fringing reef of southern Papua New Guinea. Mean ingestion (calculated from daily algal‐food consumption in winter, the relationship between water temperature and feeding activity, and C, N and P contents of algal food) was 304.3gC year, 20.4gN year−1 and 3.5gP year−1 for this herbivorous fish. Mean body‐growth rates for the fish were 5.7 mm year−1, from SEM analysis of sagittal‐otolith microstructure, and 6.2 mm year−1 from a mark‐release‐recapture study in the wild. Based on C and N analyses of whole fish and the dry‐weight/s.L. relationship, the gross growth efficiency of these fish was 0.2% for C and 0.5% for N. These very low efficiencies indicate that although P. lacrymatus ingests and absorbs a high proportion of algal production in its territory, only a small part of the assimilation goes into body growth and is thus potentially available to piscivorous fish higher in the food‐chain.
Early life histories of three sympatric sticklebacks in a salt‐marsh
Authors: Poulin R. , Fitzgerald G. J.
Published: January 2006

The effects of abiotic factors (water level, temperature, dissolved oxygen and salinity) and interspecific competition on the survival and growth of early life stages of three sympatric sticklebacks, Gasterosteus aculeatus, G. wheallandi and Pungitius pungitius, were studied in salt‐marsh tide pools near Isle Verte, Quebec. Significant year‐to‐year variation was observed in the percentage of live eggs per nest, egg incubation times, and the growth and condition of juveniles for all three species. These differences were associated with variations in temperature, oxygen and salinity in the pools. Comparisons of egg survival and juvenile growth rates were also made for G. aculeatus living in two contrasting habitats of the salt‐marsh, the harsh and variable tide pools, and a less harsh, less variable freshwater site. Egg incubation times were longer, and the percentage of live eggs per nest lower, in the river than in the pools. However, river juveniles had higher growth rates and condition factors than pool juveniles. Results of experiments to study interspecific competition between juvenile G. aculaetus and juvenile G. wheatlandi were inconsistent, and it is suggested that the effects of abiotic factors on the survival and growth of early life stages in sticklebacks are more important than competition at this site.
Ultrastructural alterations in branchial chloride cells of Atlantic salmon, Salmo salar, during parr‐smolt transformation and early development in sea water
Authors: Lubin R. T. , Rourke A. W. , Bradley T. M.
Published: January 2006

The ultrastructure of the gill primary lamellae of juvenile Atlantic salmon was examined during the parr‐smolt transformation and for 42 days after smolts were exposed to sea water. Scanning electron microscopy indicated that primary lamellae were characterized by rough convoluted surfaces that became rougher throughout the experimental period and that crypts did begin to form in freshwater fish. Crypt formation increased in sea water.

Transmission electron microscopy indicated that parr preadapt for life in sea water in part by changes in chloride cells. Chloride cells show an elaboration of rough endoplasmic reticulum in fresh water and a decline of rough endoplasmic reticulum after 42 days of sea water exposure. The tubular membrane system becomes well developed in fresh water, and apical vesicles become abundant only after seawater exposure. Mitochondria are both spherical and elongate through the period and contain well developed cristae. No evidence of mitochondrial rupture was observed. The junctions between chloride cells and adjacent cells were characterized in fresh water by long tight junctions with desmosomes. This type of junction continued in sea water and was the norm between chloride cells and accessory cells after 42 days of seawater exposure. While leaky junctions appeared to be forming, no evidence was found of membrane interdigitation between accessory cells and chloride cells after 42 days of seawater exposure. It also appeared that seawater exposure influenced the number of chloride cells exposed to the external milieu.

Pavement cells showed an elaboration in fresh water of free ribosomes and rough endoplasmic reticulum and these elements became less prominent after seawater exposure.
Ecological parasitology of polymorphic Arctic charr, Salvelinus alpinus (L.), in Thingvallavatn, Iceland
Authors: Frandsen F. , Malmquist H. J. , Snorrason S. S.
Published: January 2006

The helminth endoparasite fauna in four Arctic charr morphs, Salvelinus alpinus (L.), small benthivorous (SB), large benthivorous (LB), planktivorous (PL) and piscivorous (PI) charr, from Thingvallavatn, Iceland consisted of: Crepidostomum farionis (Trematoda: Allocreadiidae); Diplosttomum sp. (Trematoda: Diplostomatidae); Eubothrium salvelini; Diphyllobothrium dendriticum; D. ditremum (Cestoda: Pseudophyllidae); Proteocephalus longicollis (Cestoda: Proteocepha‐lidae): and Philonema oncorhynchi (Nematoda: Filariidae). The morphs exhibited distinctive patterns in prevalences and parasite burdens (mean intensity and mean relative density of parasites). SB charr had high prevalence and parasite burden of the eye fluke Diplostomum sp. and none to very light infections of the other parasite species. LB charr had relatively high prevalence and parasite burden of the intestinal fluke C. farionis, whereas infections of the remaining parasite species were light to moderate. PL and PI charr had high prevalences and worm burdens of Diphyllobothrium spp. and P. longicollis. PL charr differed from PI charr in higher worm burden off P. longicollis and lighter burden of £. salvelini. Prevalences of P. oncorhynchi were high in PL and PI charr. Association of parasite intensities and age and length offish were investigated. The different infection patterns among the morphs agree well with their partitioning in food and habitat utilization, and confirm that there is a high degree of ecological segregation between the morphs. The results demonstrate the importance of ecological factors influencing transmission efficiency of parasites to the fish host.
Histochemical characterization of myotomal muscle of five teleost species
Authors: Gill H. S. , Weatherley A. H. , Lee R. , Legere D.
Published: January 2006

A histochemical study was performed on the myotomal musculature of five teleost fish from four families (longnose dace, Rhinichthyes cataractae; bluegill, Lepomis macrochirus, smallmouth bass, Micropterus dolomieul; yellow perch, Perca flavescens; lake whitefish, Coregonus clupeaformis). Three main types of fibre (red, pink, white) were distinguished in these species on the basis of relative activities of actomyosin adenosine triphosphatase (ATPase) and NADH diaphorase. White muscle formed the bulk of the myotomal musculature. The proportion of red muscle was greater in the caudal region (11·–5% of the total cross‐sectional area) than in more anterior regions of the body in all the species. Pink fibres comprised only a transitional layer (cells deep) between red and white. In bluegill, the red fibres penetrated deeper medially from the superficial lateral position than in the other four species.

It appears that, among the present five species, the somewhat greater amount of red muscle in yellow perch may be related to the free‐cruising sometimes associated with that species, compared to the more desultory activity of the other four. It is noted that the amount of red muscle relative to white is appreciably greater in all five species than that revealed in two esocid species in an earlier study; the latter are‘ ambush predators’that swim very rapidly towards prey.
Daytime changes in oocyte development with relation to the tide for the Hawaiian saddleback wrasse, Thalassoma duperrey
Authors: Hoffman K. S. , Grau E. G.
Published: January 2006

Hourly variations in oocyte stages were characterized by size class and histological examination inassociation to the daytime tidal cycle for the Hawaiian saddleback wrasse, Thalassoma duperrey. Stage I (previtellogenic), stage II (vitellogenic) and stage III (hydrated) oocytes were identified as distinct clutches. During the autumn the profiles of oocytes stages showed rapid, group‐synchronous development from stage I to stage III. Concurrent increases in percentages of both stage III oocytes and the gonadosomatic index (GSI) were positively correlated to and occurred I h before the high tide. Increases in stage I and stage II oocytes 1 h after high tide indicated development of new clutches following a decline in stage III oocytes, and the appearance of post‐ovulatory follicles. The profile of stage II oocytes always exceeded 30% of the ovary. Lower GSI and percentages of stage III oocytes reflect significantly reduced reproduction in the summer: as in the autumn, both factors were significantly correlated, but neither variable showed a statistical relationship to the tide. Nevertheless, hydrated oocytes were found almost exclusively within 2 h of the high tide. The association of developmental changes with changes in tidal heights points to the importance of the tidal cycle or its underlying lunar influence as a predominant reproductive cue. These data show that developmental changes in oocytes occur more rapidly than observed in some more commonly studied temperate species which reproduce annually.
Age and growth of yellow eels, Anguilla anguilla, in the estuary of the Guadalquivir river (south‐west Spain)
Authors: Fernéndez‐Delgado C. , Hernando J. A. , Herrera M. , Bellido M.
Published: January 2006

A total of 1068 eels were examined from a population located in the Guadalquivir river estuary (37°N, 6°25′W). Maximum ages recorded were 4 + (males) and 7+ (females), and maximum lengths were 39‐1 cm (males) and 54.1 cm (females). No growth was recorded between November and April, most occurring in May and, to a lesser extent, in June‐October. Females grew to be larger than males. A classification analysis, based on 17 different European eel populations revealed that populations in brackish waters grew faster than those in fresh waters, but latitude also had an influence. Length‐weight relationships obtained for three eel categories (males, females and undifferentiated) were used to estimate relative condition: condition cycles were similar between sexes, with increases in autumn and decreases in winter. There were monthly fluctuations in the sex ratio, and females dominated significantly in the combined catch (234 males/276 females).
A method for direct measurement of the maximum volume of fish stomachs or digestive tracts
Authors: Burley C. C. , Vigg S.
Published: January 2006

A new method for measuring maximum stomach or digestive tract volume of fish incorporates air injection at constant pressure with water displacement to measure directly the internal volume of a stomach or analogous structure. The method was tested with coho salmon, Oncorhynchus kisutch (Walbaum), which has a true stomach, and northern squawfish, Ptychocheilus oregonensis (Richardson), which has a modified foregut as a functional analogue. Both species were collected during July‐October 1987 from the Columbia River, U.S.A. Relationships between fish weight (= volume) and maximum volume of the digestive organ were best fitted for coho salmon by an allometric model and for northern squawfish by an exponential model. Least squares regression analysis of individual measurements showed less variability in the volume of coho salmon stomachs (R2= 0.85) than in the total digestive tracts (R2= 0.55) and foreguts (R2= 0.61) of northern squawfish, relative to fish size. Compared to previous methods, the new technique has the advantage of accurately measuring the internal volume of a wide range of digestive organ shapes and sizes.
Food partitioning among scorpaenid fishes in Mediterranean seagrass beds
Authors: Harmelin‐Vivien M. L. , Kaim‐Malka R. A. , Ledoyer M. , Jacob‐Abraham S. S.
Published: January 2006

Diets of three scorpaenid fishes, Scorpaena notata, S. porcus and S. scrofa, from a Posidonia seagrass bed off Marseilles were quantitatively analysed and categorized according to the size and sex of individuals, to elucidate diel and seasonal rhythms. All three preyed on the same crustacean and fish species, but in different proportions: S. notata mostly fed on Caridae, S. porcus on brachyurans and S. scrofa on fishes. Individual size and diel period were the main factors responsible for diet variation and food partitioning that evolved according to both cyclic (temporal) and continuous (ontogenic) trends. A strong interspecific food overlap was observed in juveniles (S.L. < 50 mm), whereas intraspecific potential competition was low between juveniles and adults. Among medium and large size classes, intra‐ and interspecific food overlaps were high and of equal intensity. Narrower food niches at night, due to a stronger specialization on type and size of prey, diminished the intra‐ and interspecific potential competition during this period of maximum feeding activity. This probably allowed the high number of coexisting scorpaenid populations in Mediterranean seagrass beds. Nevertheless, microhabitat and time partitioning seemed as important as food partitioning in the structuring of fish assemblages.
Plasma ionic regulation and gill Na+/K+‐ATPase changes during rapid transfer to sea water of yearling rainbow trout, Salmo gairdneri: time course and seasonal variation
Authors: Madsen S. S. , Naamansen E. T.
Published: January 2006

Danish rainbow trout, Salmo gairdneri Richardson, (40–65 g) were transferred to 28%o sea water at intervals throughout the early spring and summer. Gill Na+/K+‐ATPase of fish kept in fresh water surged distinctly during May. Simultaneously, a body silvering occurred and plasma concentrations of Cl−, Na+ and total thyroxine (T4) decreased. The seawater transfer‐induced adaptive response in plasma electrolytes comprised a biphasic change, i.e., an adjustive peak phase and a regulatory phase lasting for 2 days and 1 week after transfer, respectively. Further, gill Na+/K+‐ATPase activity increased to a new level after an initial lag phase of 2–3 days, but electrolyte regulation was mostly initiated prior to the adaptive change in ATPase activity. In spite of increasing pre‐transfer freshwater Na+/K+‐ATPase activity during the spring, the electrolyte peak level, the degree of muscle dehydration and the mortality of fish transferred to sea water increased from April to July. The apparent uncoupling of freshwater Na+/K+‐ATPase activity and plasma electrolyte regulation in sea water is discussed in relation to smelting and prediction of hypo‐osmoregulatory performance.
Sibling cannibalism in Koi carp, Cypvinus carpio L., larvae and juveniles reared under controlled conditions
Authors: van Damme P. , Appelbaum S. , Hecht T.
Published: January 2006

The potential impact of sibling cannibalism on the size and population structure of captive populations of Koi carp, Cyprinus carpio L., which were fed only dry foods, was determined. The rate of cannibalism was found to be positively density‐dependent, with the highest rate being recorded at initial stocking densities of 40 larvae 1 (33.3% of the fish had been eaten by cannibals by day 52). Two types of cannibalism could be distinguished: type I, where the head of the prey was rejected once the caudal region of the prey had been progressively ingested; type II, where the prey were caught either head‐first or tail‐first and were ingested completely. The first type was limited to the period from the ninth to the 15th day of rearing, and the second type started on the 18th day. Measurement of the mouth, head and tail allowed the calculation of predicted cannibal ‐prey relationships. The consequences and implications of coeval sibling cannibalism in culture systems are discussed.
Gastric emptying in Scyliorhinus canicula (L.): a comparison of surface‐dependent and non‐surface dependent models
Authors: Macpherson E. , Lleonart J. , Sanchez P.
Published: January 2006

The usefulness of both surface‐dependent and non‐surface‐dependent models for describing the gastric emptying process in Scyliorhinus canicula (L.) was examined. In most cases the surface‐dependent models produced better fits than did the non‐surface‐dependent models. The exponential model (non‐surface‐dependent) only adequately described gastric evacuation in the case of small prey items with thin exoskeletons. On the other hand, the exponential model was clearly better than the linear model in all cases. Prey size had little effect on digestion rate. However, the number of prey items ingested was an important factor influencing digestion.