bluuebunny/crossref_metadata_2025 huggingface dataset:
Intrastream variation in growth rates and time of first otolith increment formation for young of the year Etheostoma simoterum (Cope) (Perciformes: Percidae)
Authors: Greenberg L. A. , Brothers E. B.
Published: January 2006

Growth rates and otolith‐estimated hatching dates of young of the year Etheostoma simoterum were studied at four localities along an elevational gradient in the Little River, Tennessee, U.S.A. during the summer of 1983. Changes in otolith increment width and mean daily air temperature corresponded well with each other, suggesting that increments were laid down daily. Growth rate increased nearly threefold from the highest elevation site to the lowest. Median otolith‐estimated hatching dates differed by about 2 weeks between sites, and the pattern was not directly related to elevation. These data indicate that within‐stream, life‐history variation of a broadly distributed species should be taken into consideration when studying factors regulating stream fish populations along elevational gradients.
Microhabitat use by brown trout, Salmo trutta L. and Atlantic salmon, S. salar L., in a stream: a comparative study of underwater and river bank observations
Authors: Heggenes J. , Brabrand Å. , Saltveit S. J.
Published: January 2006

Two methods, visual observation from the river bank and visual observation underwater by diving, were compared for microhabitat studies in young brown trout and Atlantic salmon in a stream. A wide range of habitat conditions were surveyed. Each method yielded different results with respect to microhabitat use. River bank observations missed small fish under surface turbulence and in deeper waters. Underwater observations missed small fish in shallow areas.
Cod, Gadus morhua L., populations identified by mitochondrial DNA
Authors: Dahle G.
Published: January 2006

Isozyme and haemoglobin analysis has shown that the cod, Gadus morhua L., in the NE Atlantic can be regarded as two populations: Arctic and coastal cod. One hundred and one individual cod from nine different locations were sampled and restriction fragment analysis uncovered 14 different mtDNA clones. Calculation of sequence divergence between localities displayed large divergence between samples from coastal and Arctic areas (l.77–5.62%), as opposed to the low intrapopulation divergence (∼0.10%) and the divergence between localities along the coast (∼0.17%) and in the Barents Sea (∼ 1.00%).
Correlations between egg size and egg energetic content within and among biotypes of the genus Poeciliopsis
Authors: Quattro J. M. , Weeks S. C.
Published: January 2006

That a positive correlation exists between egg size and egg energetic content is an assumption of empirical and theoretical studies of life‐history evolution. Although assumed, this relationship lacks substantiative support, particularly at the intraspecific level. To this end, we evaluated the validity of this assumption within and among clonal and bisexual females of the desert fish Poeciliopsis. As anticipated, we found generally high correlations between the two variables at all levels studied. Thus, egg volume remains a reliable and often precise indicator of maternal investment in this species.
Reproductive and histopathological effects of long‐term experimental exposure to bis(tributyltin)oxide (TBTO) on the three‐spined stickleback, Gasterosteus aculeatus Linnaeus
Authors: Holm G. , Norrgren L. , Lindén O.
Published: January 2006

Three‐spined sticklebacks, Gasterosteus aculeatus Linnaeus, were exposed to 0, 0.1, 1.0, 2.5 and 10 μg bis(tributyltin)oxide (TBTO) 1−1 for up to 7.5 months in a flow‐through system of sea water. As early as 4 weeks after the start of the experiment, fish from the 10 μg TBTO 1−1 group showed diminishing appetite, increasing lethargy and opaque eyes. The mortality in this group after 2 months of exposure was 80%. No significant differences between the control and the exposed groups were noted concerning fecundity, hatched fry and frequencies of malformed fry. The gonad somatic index (GSI) was determined before and during the spawning period. GSI in control fish increased significantly, while that in the exposed groups remained unchanged between the two sampling occasions. Structural examination of the gills from fish exposed for 2 months to 10 μg TBTO I−1 revealed fusion between secondary lamellae and gradual cell degeneration. The chloride cells were characterized by degenerating mitochondria. Hepatocytes in fish exposed to 2.5 and 10 μg TBTO I−1 contained an increased number of lipid‐containing vacuoles and the nucleoli were disorganized and fragmented.
Embryonic and larval development of brown trout, Salmo trutta L.: exposure to aluminium, copper, lead or zinc in soft, acid water
Authors: Sayer M. D. J. , Reader J. P. , Morris R.
Published: January 2006

Freshly fertilized ova, eyed ova and yolk‐sac fry of brown trout, Salmo trutta L., were exposed to each of four trace metals (aluminium: 6000 nmol l−1; copper: 80 nmol l−1; lead: 50 nmol l−1; zinc: 300 nmol l−1) while held in flowing artificial soft‐water media maintained at pH 4.5 or 5.6 and [Ca] 20 or 200 μmol l−1. In continuous exposure from fertilization, survival of ova was severely affected at pH 4.5 and [Ca] 20 μmol l−1, regardless of the presence of Cu, Pb or Zn; Al reduced embryonic mortality and improved hatching success. High ambient [Ca] at pH 4.5 increased egg survival. At ‘swim‐up’, surviving fry exposed to Al or Pb had lower whole body Ca, Na and K content, irrespective of pH or ambient [Ca]. Cu reduced whole body Ca and K content at pH 5.6 and [Ca] 200 μmol−1, and whole body Ca, Na and K content in the other media. Zn reduced whole body mineral content at pH 5.6 and [Ca] 20 μmol l−1. Whole body Mg content was reduced by all trace metals at pH 5.6 and [Ca] 20 μmol l−1, and by Cu at pH 5.6 and [Ca] 200 μmol l−1. Al and Cu impaired skeletal calcification at pH 5.6 at both ambient [Ca]; Pb only at [Ca] 20 μmol I−1. Zn enhanced calcification at pH 4.5 and [Ca] 200 μmol l−1. In the absence of trace metals, low pH reduced body Ca, Na, K content and skeletal calcification at [Ca] 200 μmol l−1. The uptake of Ca, Na and K, measured at regular intervals from hatching was impaired to the same extent by all treatments at pH 4.5, irrespective of ambient [Ca] or trace metal presence. At pH 5.6, irrespective of ambient [Ca], Al, Cu and Pb impaired Ca and K uptake. The rate of Na uptake was reduced by Al and Cu. Al‐treated yolk‐sac fry, exposed to low ambient [Ca] from 200–300° days post‐hatch, suffered high mortalities regardless of pH. Ca, Na and K uptake was impaired by all treatments at pH 4.5, and by Al and Cu at pH 5.6 in a similar exposure period. The development of the early stages of brown trout in the presence of trace metals is discussed in relation to recruitment failure in areas of soft, acid water.
Population ecology of the paddy field‐dwelling fish Channa gachua (Günther) (Perciformes, Channidae) in Sri Lanka
Authors: de Silva K. H. G. M.
Published: January 2006

A population of Channa gachua in a small irrigation canal that supplies rice fields was studied by monthly sampling over 2 years. The population density was positively correlated with the rainfall and varied from 0.34 to 0.95 individuals m−2. The growth parameters of the von Bertalanffy growth equation determined on monthly size–frequency data were Lx= 179 mm total length and K=0.50. Overall male to female ratio was 0.82 and there were more females than males in the middle size classes. Spawning occurred throughout the year, but all evidence indicated enhanced breeding during major rainy periods of May to July and October to December. The length at first spawning was 102 mm, which is reached in about 20 months. Fecundity, which varied between 389 and 2130, was positively correlated with gonad weight, body weight and total length. Longevity and natural mortality were estimated as 6 years and l.27 yr−1, respectively. However, 99% of the population appeared to live for only 3 years. The mean biomass, average annual production and turnover ratio of the population were 7.35 g m−2, 12.06 g m−2 and 1.64, respectively.
Development of length–bimodality and smolting in wild stocks of Atlantic salmon, Salmo salar L., under different growth conditions
Authors: Nicieza A. G. , Braña F. , Toledo M. M.
Published: January 2006

Growth dynamics of juvenile Atlantic salmon, Salmo salar L., from two sections of the Narcea River and one of the Esva River (Northern Spain) were examined in relation to the development of bimodality in their size–frequency distributions. Size–bimodality was clearer under intermediate growth (section A) than under relatively fast or slow growth. The proportion of fish entering the upper modal group increase with growth intensity. Composition of upper and lower modal groups became fixed prior to December, and at this time both groups separated on the 90–95 mm interval. Fish exhibiting smolt appearance in late March (larger than 130 mm) had already been upper group fish in December, while parr‐like fish and those that remained in the river by May (potential 2‐year‐old smolts) had formed the lower modal group. Anadromous salmon catch in the Narcea River was mostly of previously 1‐year‐old smolts (97.6%), of which 94% were larger than 100 mm by their first winter. In the Esva River, slow growth of juveniles is consistent with a large proportion of 2‐year‐old smolts (47.9%) among anadromous salmon. Both juvenile samples and scale analysis of anadromous salmon indicate that 2‐year‐old smolts were larger than 1‐year‐olds. Early disappearance of the former (before March) is, at least, partially related to earlier migration of large fish, since sexual maturity of parr does not provide a complete explanation. The Narcea stock have a minimum length at smolting of about 130 mm and an optimum smolt size in the 155–175 mm interval. Mean smolt length did not vary although the winter length changed between years.
The importance of fish stocking in the dissemination of parasites throughout a group of reservoirs
Authors: Kennedy C. R. , Hartvigsen R. , Halvorsen O.
Published: January 2006

In view of the known importance of anthropochore movements of fish in disseminating their parasites, it was hypothesized that local movements of fish between neighbouring water bodies for stocking and management purposes would similarly disseminate their parasites, resulting in a high degree of similarity in the parasite communities of fish in water bodies that have been linked by fish transfers. This hypothesis was tested by comparing the helminth parasite communities in brown trout, Salmo trutta Linnaeus and rainbow trout, Oncorhynchus mykiss (Walbaum), in reservoirs in south west England. In one group of six reservoirs there is a recent history of transfers of rainbow trout, and in the second group of four there have been no transfers over the last decade. There was no difference in mean similarity, using Jaccard's Coefficient and a Percentage Similarity Index, between the helminth faunas of trout in the reservoirs linked by transfers and those not so linked, and the distribution of several individual species of helminths was not consistent with their having been disseminated in the course of fish stockings. The hypothesis is thus rejected and it is concluded that anthropochore transfers of trout between reservoirs have been of little or no significance in the dispersal of parasites throughout the reservoirs or in the transfer of helminths from one reservoir to another. The reasons for this unexpected conclusion are discussed in the light of indications that factors unrelated to fish transfers were important determinants of helminth community composition in individual reservoirs.
The environmental requirements of Atlantic salmon, Salmo salar L., during their passage through the Thames Estuary, 1982–1989
Authors: Alabaster J. S. , Gough P. J. , Brooker W. J.
Published: January 2006

An examination of data on both water quality in the Thames Estuary and on the count of salmon. Salmo salar L. trapped in fresh water above the head of the tide in 1982–1989, was carried out to establish statistical correlations. The annual and monthly return of salmon as 1‐sea‐winter fish (grilse) in June to September was negatively correlated with water temperature, a nil catch being associated with a maximum value of 24.2° C, coupled with lower values maintained over substantial lengths of the estuary (e.g. 21.5° C over a distance of no more than 50 km). The annual return was negatively related to the extent to which the estuary was predicted to be lethal from the combination of low concentration of dissolved oxygen (DO) and high temperature, a reduction in DO of 1 mg 1 1 being equivalent to an increase in temperature of 4° C. The annual return for the whole year was directly related to the return in July to September. Depending upon the year, the monthly returns were related to both DO and temperature; they were reduced to a tenth at a 95 percentile DO of 2.7 mg 1 1, whilst the weekly catches were reduced to zero at 2.4 mg 1−1. Weekly catches increased with river flow and daily catches increased with both river flow and tidal height. The few mortalities observed in the estuary in July are generally related to the quality of the water as predicted from the combination of high temperature and low DO.
The first record of fishes of the rare deep‐sea family Megalomycteridae (Lampriformes) from the north‐eastern Atlantic
Authors: Swinney G. N.
Published: January 2006

Two fishes of the family Megalomycteridae are reported from off Madeira; the first time this family has been recorded in the NE Atlantic. The specimens generally agree with the generic description of Ataxolepis, but raise doubt over the validity of the characters used to separate the taxa within the family.
Short‐term movements of larval and juvenile lumpfish, Cyclopterus lumpus L., in tidepools
Authors: Moring J. R. , Moring S. W.
Published: January 2006

Larval and juvenile lumpfish, Cyclopterm lumpus L., which attach to marine algae and eelgrass using a ventral sucker, were marked and recaptured in a series of experiments along Schoodic Peninsula, Maine, U.S.A. A repeat‐marking experiment in 1988 indicated immigration and, possibly, emigration in tidepools. Yet, some individuals remained in the same tidepool for up to 25 days. Experiments with marked groups of fish in 1988 and 1989 revealed significant short‐term residence of individual lumpfish; up to 79% of marked fish were recaptured in the same tidepool 2 days later, even after major storms. A translocated group of 34 lumpfish left the new tidepool within 1 day, but two individuals returned to the home tidepool within 6 days. Extended inhabitance of tidepools by larval and juvenile lumpfish seems to be a function of availability of food and algal cover.
Territoriality and associated behaviour in three species of the genus Cephalopholis (Pisces: Serranidae) in the Gulf of Aqaba, Red Sea
Authors: Shpigel M. , Fishelson L.
Published: January 2006

Social structure and behavioural mechanisms enabling sympatry in three species of predatory fish in the Gulf of Aqaba (Cephalopholis miniata (Forsskål), Cephalopholis argus Bloch and Schneider, and Cephalopholis henistiktos (Rüppell)) were examined in this study. C. miniata and C. argus formed compound interspecific territories in which they occurred in haremic groups consisting of a dominant male and two to 12 females. C. miniata and C. argus groups occupied territories of up to 475 m2, and 2000 m2 respectively, subdivided into secondary territories, each inhabited by an individual female. Observations of tagged fish disclosed behaviour patterns of patrolling by males, visiting the females, and antiparallel swimming of sexes. C. hemistiktos, in contrast, was monogamous and each pair jointly defended a common territory of up to 62 m2. Among the three species the dominance hierarchy was C. argus > C. miniata > C. hemistiktos.
Population biology of Proteocephalus macrocephalus (Creplin) in the European eel, Anguilla anguilla (Linnaeus), in two small rivers
Authors: Nie P. , Kennedy C. R.
Published: January 2006

Seasonal changes in populations of Proteocephalus macrocephalus (Creplin) were investigated for 17 months in the European eel, Anguilla anguilla (Linnaeus), in two rivers in Devon, SW England, but no clear seasonal patterns in prevalence and abundance were apparent. Population levels of the cestode are low in both localities, and it is suggested that natural population levels of P. macrocephalus may generally be low. However, growth and maturation of the cestode show marked seasonality with both occurring mainly in early summer.
The diet of Oreochromis lidole (Trewavas) and other chambo species in Lakes Malaŵi and Malombe
Authors: Turner G. F. , Grimm A. S. , Mhone O. K. , Robinson R. L. , Pitcher T. J.
Published: January 2006

Oreochromis lidole (Trewavas) is a member of a flock of tilapünes endemic to the Lake Mala% catchment area, of which it is considered to be the most pelagic and planktivorous species. Analysis of the stomach contents of adults from the South East Arm of Lake Malaŵ, from fish caught by both the offshore trawl fishery, and the inshore gillnet fishery, indicates a very narrow dietary breadth, dominated by the filamentous diatom Melosira. The presence of quantities of sand in the stomach indicates that at least some of the food is obtained from sediment feeding. During the breeding season, in November, brooding female O. lidole caught in shallow water exhibited a much broader diet, resembling the more inshore species O. squarnipinnis (Gunther) and O. karongae (Trewavas), with a higher proportion of filamentous chlorophytes and a large amount of sand. Juvenile chambo initially feed mainly on epilithic and epiphytic algae, turning more to plankton and sediment at larger sizes. In general, the different Oreochromiv spp. Caught in the same place at the same time have very similar diets, suggesting that any avoidance of competition for food resources results from habitat partitioning.
Influence of temperature on evasive responses of Atlantic herring larvae attacked by yearling herring, Clupea harengus L.
Authors: Fuiman L. A.
Published: January 2006

Predation encounters were staged in the laboratory between yearling herring, Clupea harengus L., 66 to 104 mm t.l., and herring larvae, 8 to 30 mm t.l.., at 8,11 and 14o C. Video records were used to quantify prey behaviour. Prey responsiveness, reactive distance, response latency, and apparent looming threshold were not affected by temperature. Response speeds increased with temperature. Predator error rate and capture success showed no consistent thermal effects. Although the experiments could not fully evaluate the influence of temperature on the predators, results suggest that the predator's performance largely governs the outcome of an attack on a larva and that higher temperatures favour the predator by increasing the frequency of its encounter with prey.
Stocking experiments with 0 + and 1 + trout parr, Salmo trutta L., of wild and hatchery origin: 2. Post‐stocking movements
Authors: Jorgensen J. , Berg S.
Published: January 2006

Wild and hatchery‐reared 8–12‐month‐old (5–8 cm) trout, Salmo truttu L., were stocked into tributaries of the River Gudená. Movements were examined by means of electrofishing. Overall dispersal and upstream movement were greater for wild trout than for domestic trout. Maximum distance of movement was 600 m upstream for both strains and 600 m downstream for wild trout, and 700 m for domestic trout. Upstream movement started within 2 months from stocking and continued for at least 4 months. Downstream movement during the first few days after stocking, was more pronounced for domestic trout than for wild trout.
Fine structure of chloride cells in freshwater‐ and seawater‐adapted Oreochromis niloticus (Linnaeus) and Oreochromis mossambicus (Peters)
Authors: Cioni C. , de Merich D. , Cataldi E. , Cataudella S.
Published: January 2006

Ultrastructural features of branchial chloride cells in Oreochromis niloticus (Linnaeus) and O. mossambicus (Peters) adapted to both fresh water and sea water were compdred. In freshwater adapted fish of both species chloride cells showed similar morphological features. Multicellular complexes made of a mature chloride cell and one or more accessory cells sharing a single apical crypt have been observed. Whereas high percentages of 0. mossambicus survived at maximum salinity only a few individuals of 0.niloticus showed the capacity to adapt to sea water. In the seawater‐adapted individuals of 0.niloficus and 0. rnossambicusthe chloride cells showed a two‐ and three‐fold increase in sizei. respectively. Most chloride cells are organized in large multi‐cellular complcxcs with apical interdigitations of accessory cells and ‘leaky junctions’. These results indicate that the difference in euryhalinity of the species studied is related to functional rather than structural differences.
Immunoglobulin concentration in Atlantic cod, Gadus morhua L., serum and cross‐reactivity between anti‐cod‐antibodies and immunoglobulins from other species
Authors: Israelson O. , Petersson A. , Bengtén E. , Wiersma E. J. , Anderson J. , Gezelius G. , Pilstrom L.
Published: January 2006

The immunoglobulin (Ig) level in serum from Atlantic cod, Gudus morhua L. (Teleostomi, Gadiformes), was measured using ELISA. Cod serum contains 5.62 ± 0.19 mg Ig ml, which constitute 17.2% of the total serum proteins.

Polyclonal and monoclonal antibodies (Ab) against cod‐Ig were used for cross‐reactivity studies in sera from other species. The cross‐reaction with polyclonal Ab was high in gadifom fish, and low or absent in the other tested species. Immunoprecipitation showed that the Ab only binds to the Ig of the serum from the other species. The results within the gadiform group indicate that (1) Gadidae and Lotidae are more closely related to each other than to Merluccidae, (2) Phycidae is more distant related to Lotidae than earlier considered, (3) Zoarcidae seem to be more distant related to Gadus than other species of Gadiformes. These results support recent revisions of the systematics of Gadiformes.

Monoclonal Ab against the heavy chain of cod‐Ig show no, or small (< 15%) cross‐reactions with serum from gadiform species. One monoclonal Ab against the light chain shows high cross‐reaction and also binds to Ig from species outside the Gadiformes, indicating that the light chain of Ig might be more conserved than the heavy chain.
The opercular gland of the cleaner‐wrasse Labroides dimidiatus (Labridae), a light‐, electron and scanning electron microscopic investigation
Authors: Lenke R.
Published: January 2006

A histological and ultrastructural examination of the opercular gland of the cleaner‐wrasse Labroides dimidiutus has demonstrated that the slimy envelope which covers the animal at night is mainly produced by large mucous goblet cells in a folded epithelium; there is a high number of acidophilic secretory cells. At the ultrastructural level, both cell‐types open at the surface of the epidermis. Preliminary experiments with pilocarpine, atropine and the α‐blocker propranolol reveal a neural regulation of mucus discharge. Also, the rich vascularization of the gland could indicate a hormonal control e.g. by prolactin. The secretory products of both types of goblet cells are discussed in relation to their possible antibiotic properties.
Growth and morphological development of chub, Leuciscus cephalus (L.), during the first year of life
Authors: Economou A. N. , Daoulas Ch. , Psarras T.
Published: January 2006

The growth and the morphological development of larvae and juveniles of chub, Leuciscus cephalus (L.), from a small stream of western Greece is described, based on field samples and laboratory‐raised fish. In the laboratory, size hierarchy was developed and morphological differentiation occurred at a younger age in the fastest growing larvae. Growth was faster in the field and differentiation of fins and scales began at a larger size, but apparently at a younger age, than in the laboratory.
A study of the peripheral innervation and muscle fibre types of Ictalurus nebulosus (Lesueur) and Ictalurus punctatus (Rafinesque)
Authors: Raso D. S.
Published: January 2006

The innervation pattern and fibre types of the axial musculature of two closely related catfish species with differing lifestyles, Ictalurus nebulosus (Lesueur) and I. punctatus (Rafinesque) were investigated. Both fish displayed the multiple innervation pattern in the red muscle. However, the white muscle of I. nebulosus demonstrated terminal innervation while I. puncrurus displayed multiply innervated white muscle fibres. Fibre typing utilizing histochemical techniques for glyco‐gen, lipid, succinic dehydrogenase and glucose‐6‐phosphate dehydrogenase revealed the typical teleostean distribution of red, intermediate and white muscle fibres in both fish. Staining was greatest in the red muscle fibres and least in the white muscle fibres. The white muscle fibres of I. punctatus stained slightly more for lipid than the white fibres of I. nebulosus which may be correlated with a greater aerobic capacity related to lifestyle and possibly innervation.
Life‐history plasticity under resource stress in a clonal fish (Poeciliidae: Poeciliopsis)
Authors: Weeks S. C. , Quattro J. M.
Published: January 2006

Within‐individual plasticity for reproductive investment was examined in a clonal fish (Poeciliidae: Poeciliopsis) grown under six levels of resource stress. Growth, age at first reproduction, egg production, egg size, egg energetic content, and survivorship were measured from fish grown in three dietary and two density treatments. Growth and fecundity decreased with both increased density and food stress. Age at first reproduction increased with increased density, but was unaffected by the diet treatments. Reproductive effort (clutch size per female weight), offspring investment (egg size and egg energetic content), and survivorship were invariant across all treatment combinations. We compare these results with predictions based on theoretical treatments of optimal reproductive investment.
Spatio‐temporal distribution pattern of the red band‐fish Cepola rubescens Linnaeus at different stages of its life cycle in the northwestern Mediterranean
Authors: Martín P. , Sabates A.
Published: January 2006

The larvae of Cepola rubescens Linnaeus, 1766 were collected from May to October with a surface temperature of 17.5°C at the beginning of the spawning. They were widely distributed over the continental shelf and the greatest concentrations were found at stations with depth around 100 m. During all months, most of the larvae were of small size, between 2.0 and 3.0 mm s.l. The juveniles and adults were caught in a wide range of depths, from less than 25 m to about 200 m, and the highest abundance was also found at depths of about 100 m, but no large individuals were found at depths less than 50 m. The catches of the trawling fleet showed a marked seasonality, with maximum values at the end of spring and minimum at the end of autumn and the beginning of winter. This seasonality seems to be related to reproduction since the highest catches were obtained during the spawning period.
Daily growth increments in the otoliths of juvenile greenback flounder, Rhombosolea tapirina Gunther, 1862
Authors: Stewart B. D. , Jenkins G. P.
Published: January 2006

Otolith check marks of both tetracycline‐treated and control juvenile greenback flounders, Rhombosolea tapirina, were attributed to the stress of transfer between aquarium tanks. Subsequent counts showed that otolith increments were deposited daily.
Short‐term cell culture technique for obtaining chromosomes in marine and freshwater fish
Authors: Alvarez M. C. , Otis J. , Amores A. , Guise K.
Published: January 2006

In this paper we describe a simple and reliable short‐term fish cell culture technique, for obtaining chromosome spreads with minimum stress involving the specimens sampled. Fibroblasts were derived from primary cultures from the caudal fin of some economically important freshwater species: northern pike, Esox lucius L., goldfish, Carassius auratus L., and marine species: gilthead sea bream, Sparus aurata L. and cardinal fish, Apogon imberbisL.
The ingestion of bacteria in suspension by the common carp Cyprinus carpio L.
Authors: Beveridge M. C. M. , Sikdar P. K. , Frerichs G. N. , Millar S.
Published: January 2006

Groups of large (65 ‐75 g) and small (8‐17 g) common carp (Cyprinus carpio L.) fingerlings were exposed to the bacterium Chromobacterium violaceurn in order to establish whether they could detect and ingest unattached bacteria. Small fish exposed to both bacteria and to cell‐free bacterial extracts showed a significant increase in opercular beat rates, thus demonstrating that they are able to detect the presence of unattached bacteria in suspension. Examination of carp gut contents showed that the proportion of small fish ingesting bacteria increased with exposure time although no significant relationship was observed among larger fish. Significant, positive correlations between numbers of viable bacteria isolated from the intestinal tracts and concentration in the environment were observed. Possible mechanisms of bacterial ingestion are discussed.
Morphology of the male reproductive system of, Coralliozetus angelica (Pisces, Blennioidei, Chaenopsidae)
Authors: Patzner R. A.
Published: January 2006

The testis, the seminal vesicles and the spermatic duct of Coralliozetus angelica (Böhlke & Mead) are described. The testis and the seminal vesicles are not arranged in pairs but are single. The testis is situated on the left side of the animal and consists of chambers instead of tubules. The seminal vesicle on the right side is composed of two different types (seminal vesicle 1 and 2) which are not connected with each other
The bioenergetics of grass carp, Ctenopharyngodon idella (Val.): energy allocation at different planes of nutrition
Authors: Carter C. G. , Brafield A. E.
Published: January 2006

Complete energy budgets were constructed for 19 grass carp, Ctenupharyngudon idella (Val.), held individually in a respirometer for a month. The fish were fed one of four diets or starved. Diets varying in the proportions of protein, lipid and carbohydrate were described as high protein (HP), high carbohydrate (HC) or high lipid (HL). A fourth diet (LM) was made from dried duckweed, Lemna spp., to provide a more natural diet. Fish were fed and faeces collected daily and oxygen consumption was measured continuously over the month that each experiment lasted. Excretion of ammonia and urea was measured on several days. The total energy lost via nitrogenous waste was calculated using an average daily ammonia quotient (AQ).

For growing fish between 50 and 61% of consumed energy was lost via respiration. Energetic losses via nitrogenous wastes were highest on the HP diet (4.7%) and lowest on the HC diet (3.1%). Faecal loss washigheston the HL diet (19.4%)and lowest on the HP diet (10.2%). Over a month of starvation, 32.5% of energy requirement was met by the respiration of protein and 3.2% of the total energy lost was via nitrogenous waste. Fish fed zero or sub‐maintenance rations tended to respire lipid in preference to protein whereas fish fed super‐maintenance rations accumulated lipid. Protein retention was proportionally highest on HP (48% of total energy retained as growth) and lowest on HC (32%) and HL (30%). This reflected the accumulation of lipid on both the high carbohydrate and high lipid diets. The partitioning of metabolizable energy (ME) was investigated and 0.45 (HL), 0.59 (HP) and 0‐67 (HC) kJ ME.kJ‐1 retained were lost via respiration.
The occurrence of young scaldfish Arnoglossus latevna (Walbaum, 1792) in the eastern Irish Sea
Authors: Rogers S.I.
Published: January 2006

Unusually high numbers of scaldfish have been found in the eastern Irish Sea during 1990. Advantageous climatic conditions may be responsible. The impact of this predator on inshore flatfish nursery populations may be important.
Measurement of trophic niche breadth using occurrence frequencies
Authors: Cardona L.
Published: January 2006

A modification of Gladfelter‐Johnson's index to measure trophic niche breadth using occurrence frequencies is proposed, in order to make it more sensitive to different resource use patterns. The new index ranges from 0 to 1 and measures niche breadth in a guild context.
Genetic discrimination of wild and hatchery populations of brook charr, Salvelinus fontinalis (Mitchill), in Ontario using mitochondrial DNA analysis
Authors: Danzmann R. G. , Ihssen P. E. , Hebert P. D. N.
Published: January 2006

Two brood stocks of brook charr, Sulvelinus fontinalis, are currently maintained by the Ontario Ministry of Natural Resources. The Nipigon brood stock originated from Lake Nipigon, in north‐central Ontario, while the Hills Lake stock is believed to have been produced by hybridizing several strains (including charr from a Pennsylvania hatchery as well as charr from Ontario) in the past. The mitochondrial DNA (mtDNA) variability of these brood stocks was characterized using 51 hexanucleotide restriction enzymes. Eleven restriction enzymes, Acc I, Am I, BunI, Bun II, Hind III, Nco I, NdeI, Nhe I, Nsi I, Pst I and Sph I, were polymorphic between the two brood stocks. Eight hatchery mtDNA haplotypes were detected showing a maximum of 0.41 % sequence divergence. Seven haplotypes are present in the Hills Lake strain, and two in the Nipigon strain. These mtDNA haplotypes are useful markers to determine the degree of reproductive success between planted and native fish. In one comparison in southern Ontario, less than 20% of the wild fish sampled from the head water regions of a small drainage entering Lake Erie could have resulted from random introgression with hatchery fish planted further downstream, because most of these fish possessed a unique Acc 1 cut site. This is one of the few examples in stock analysis studies where such a high degree of genetic discrimination is evident between hatchery and native fish.
Nuclear DNA and salmonid phylogenetics
Authors: Phillips R. B. , Pleyte K. A.
Published: January 2006

There are many unresolved problems in salmonid systematics, both at the interspecific and sub‐specific levels. Some of the major systematic problems in the subfamily Salmoninae are briefly reviewed along with the available molecular methods for their analysis. Nuclear DNA markers available for use in molecular systematics include localized and dispersed highly repetitive DNA sequences, moderately repetitive sequences such as the ribosomal RNA genes (rDNA), and single copy DNA sequences. Both coding and non‐coding sequences can be examined in the rDNA and single copy DNA. The rDNA is especially suitable for use in phylogenetic analysis, since different regions evolve at different rates and can be used for comparisons at different taxonomic levels. Comparison of restriction maps of the entire rDNA repeating unit in 17 salmonid species from Hucho. Sahelinus, Salmo and Oncorhynchus has shown that the transcribed spacer regions are the most informative for interspecific comparisons and that the intergenic spacer has potential for use in intraspecific comparisons. Our current approach is to amplify selected regions from each of these spacers for analysis by DNA sequencing. DNA sequence analysis of the internal transcribed spacers should be very informative in elucidating interspecific relationships in Salvelinus and Oncorhynchus. Analysis of a hypervariable region in the intergenic spacer has potential for identification of geographically separated stocks. The relative utility of different types of nuclear DNA sequences for identification of stocks and subspecies is examined.
Phylogenetic relationships among the subfamily Coregoninae as revealed by mitochondrial DNA restriction analysis
Authors: Bernatchez L. , Colombani F. , Dodson J. J.
Published: January 2006

Mitochondria1 DNA (mtDNA) restriction analysis was used to assess phylogenetic patterns among 21 taxa of the subfamily Coregoninae. The genus Prosopium formed a very distinct group differing by 10% (sequence divergence estimate) from other species. Coregonus and Stenodus species were closely related, diverging by sequence divergence estimates of less than 5.6%. These species split into two major sister groups. One comprised all ‘true whitefish’ (subgenus Coregonus) and four cisco species (subgenus Leucichrhys). The most distant species within this assemblage was the Acadian whitefish (C. huntsmani). The other group included all other cisco species and also the Inconnu (Stenodus leucichthys). These results supported a polyphyletic origin of the ciscoes, and did not support Stenodus as a sister taxon of the genus Coregonus. The levels of sequence divergence observed suggested that most extant coregonines radiated during the Pleistocene.
Natural hybrids between Atlantic salmon, Salmo salar L., and trout, Salmo trutta L., in juvenile salmonid populations in south‐west England
Authors: Hurrell R. H. , Price D. J.
Published: January 2006

Electrophoretic analysis of juvenile salmonids from south‐west England revealed the presence of natural hybrids between Atlantic salmon, Salmo salar L., and brown trout, Salmo rrurra L., within three of five rivers. Amongst 409 juvenile ‘salmon’, 1.2% were hybrids, and of 150 juvenile ‘trout’ sampled, 2.0% were natural hybrids. In one river, similar hybridization levels in ‘salmon’ parr samples were found in two successive years. Levels of hybridization are high when compared with most similar studies, especially others within the United Kingdom. Possible factors influencing this are discussed.
High frequency of natural hybrids between Atlantic salmon, Salmo salar L., and brown trout, S. trutta L., in a Swedish river
Authors: Jansson H. , Holmgren I. , Wedin K. , Anderson T.
Published: January 2006

Among 332 parr from the Swedish River Grönån examined by electrophoresis, 44 (13%) were hybrids between Atlantic salmon and brown trout. The hybrid frequencies in three sections of Grönån were significantly different (23. 8 and 2%). All hybrids are evidently of natural origin. and possible factors promoting hybridization are irregular overlapping spawning times. lack of separate spawning grounds, and involvement of sneakers.
Allozyme heterozygosity and morphological homeostasis in pink salmon, Oncorhynchus gorbuscha (Walbaum): evidences from family analysis*
Authors: Kartavtsev Y. P.
Published: January 2006

In the families produced by diallel 2 × 2 crosses there were positive relationships in two experimental groups between individual heterozygosity (H0) at four allozyme loci (PGM*, G3PDH*, sMEP*, sMDH−3,4*) and the size of the fish, their morphological variability (10 traits) and the viability among families. An integrative H0 influence on complexes of morphological traits was also obtained. On the basis of factor and discriminant analysis it was shown that H0 correlated with morphological homeostasis at least within one experimental group.
A comparative study on morphology, growth rate and reproduction of Clarias gariepinus (Burchell, 1822), Heterobranchus longifilis Valenciennes, 1840, and their reciprocal hybrids (Pisces, Clariidae)
Authors: Legendre M. , Teugels G. G. , Cauty C. , Jalabert B.
Published: January 2006

A detailed study on reproduction indicated that female C. gariepinus mature earlier (5–7 months) than female H. longifilis (12–14 months). In the reciprocal hybrids, female first sexual maturity was attained at 20–21 months. Both reciprocal hybrids and parental species displayed an equilibrated sex ratio. Macroscopical and microscopical observations revealed numerous abnormalities in gonadal development of the hybrids. GSI and fecundity in female hybrids were considerably lower than those found in the parental species. Moreover, intra‐ovarian tumors occurred in 20% of the hybrids. In hybrid males, GSIs were generally higher than those found in the parental species, but the spermatozoa concentration in the semen was about 100 times less. Despite these abnormalities, viable larvae, resulting from F2 and backcross fertilizations, were obtained.
Spatial variation in reproduction, and occurrence of non‐reproductive adults, in orange roughy, Hoplostethus atlanticus Collett (Trachichthyidae), from south‐eastern Australia
Authors: Bell J. D. , Lyle J. M. , Bulman C. M. , Graham K. J. , Newton G. M. , Smith D. C.
Published: January 2006

This study was designed to determine whether orange roughy reproduce throughout their distribution in Australian waters, and if so, whether commencement of spawning and length at maturity vary within the region. We found that females from four widely separated sampling areas reproduced in 1988, but that the onset of spawning and length at maturity were not the same in all the areas. In New South Wales, ovulation was finished by mid‐June, and 50% of females were mature at 28 cm standard length (S.L.). On the other hand, females from eastern and western Tasmania and South Australia did not spawn until mid‐July, and 50% of females from Tasmania were not mature until 32 cm S.L. Females from all areas had oocytes with yolk granules at least 5 months before ovulation. However, in the few months before spawning, some adult females from all areas had not undergone vitellogenesis or were resorbing all yolky oocytes. The best estimates of the proportion of these non‐reproductive females were made in March and April, when the single batch of eggs to be spawned was clearly distinguishable, and before spawning aggregations had formed. In 1990 in eastern Tasmania, at the site of a major spawning aggregation, the best estimate of the proportion of non‐reproductive fish was 45%. We suggest that scarcity of food, coupled with the cost of joining a spawning aggregation, may result in intermittent spawning in this long‐lived species.
Intact antigen uptake in intestinal epithelial cells of marine fish larvae
Authors: Olafsen J. A. , Hansen G. H.
Published: January 2006

Endocytosis of bacteria by epithelial cells in the hindgut of 4‐ to 6‐day‐old cod (Gadus morhua L.) larvae and of 10‐ to 12‐day‐old herring (Clupea harengus L.) larvae was demonstrated by fluorescence microscopy and transmission electron microscopy. Fixed sheep erythrocytes and bacteria‐sized latex particles were not ingested by these cells. By immunohistochemical methods intact bacterial antigens were observed in columnar epithelial cells in the foregut of 4‐day‐old yolk‐sac larvae of cod. In these cells a preferential uptake of Vibrio fischeri and Vibrio salmonicida cells as compared to Flavobacterium sp. was found. The possible role of these findings in the establishment of an indigenous microflora, defence against pathogens or nutrient absorption in fish larvae is discussed.
Ascorbate concentration in fish ontogeny
Authors: Dabrowski K.
Published: January 2006

The ontogenetic trend of ascorbate has been quantified in three freshwater fishes: roach (Rutilus rutilus), whitefish (Coregonus lavaretus) and Arctic charr (Salvelinus alpinus). Total ascorbate (reduced and oxidized) declined from 150 to μg g−1 as newly hatched larvae grew to become several‐months‐old juveniles. Declining total ascorbate with increasing size of metamorphosing fish could not be reversed by feeding on brine shrimp, Artemia salina nauplii, zooplanktonic food containing > 74μg g−1 total ascorbate. The proportion of reduced ascorbate in total ascorbate increases with fish size/age. The physiological mechanism of the changes in transferable ascorbate forms remains unknown, but high dehydroascorbate concentrations suggest high vulnerability of larval fish to oxidation stress. This is the first report on quantity of vitamin C retained in actively‐feeding larval and juvenile fish. The efficiency of ascorbate transfer from zooplankters to larval fish amounted to 5–20%. The ecological significance of larval fish feeding on various zooplankters and/or phytoplankton may reflect a trend toward maximum transfer of this vitamin in freshwater food webs.
Sub‐surface drift feeding by coho salmon (Oncorhynchus kisutch, Walbaum): a model and test
Authors: Dunbrack R. L.
Published: January 2006

The results of a test of a mechanistic encounter model that predicts the size‐frequency composition of the diet of drift‐feeding coho salmon (Oncorhynchus kisulch, Walbaum) are described. When all taxa in the drift were included in the model the predicted and actual diets differed significantly, although the model explained most of the variance between the diet and the predictions of a null model. When non‐consumed taxa, including the distasteful and aposematic taxon Hydracarina, were excluded from the drift composition there was no significant difference between predicted and actual diets. The model's goodness of fit increased when it was modified to predict the biomass size‐frequency diet composition, explaining 99% of the weighted sum of squared deviations between the diet and a null model. A number of alternate models are tested and a potentially useful simplification of the model is identified.
Gill chloride cell surface‐area is greater in freshwater‐adapted adult sea trout (Salmo trutta, L.) than those adapted to sea water
Authors: Brown P.
Published: January 2006

An increase in the apical surface‐area exposed to the environment in sea trout (Salmo trutta, L.) branchial chloride cells, examined by scanning electron microscopy after adaptation to fresh water, indicates that salt‐uptake may be dependent upon apical membrane morphology.
Awareness reactions and avoidance responses to sound in juvenile Atlantic salmon, Salmo salar L.
Authors: Knudsen F. R. , Enger P. S. , Sand O.
Published: January 2006

The possibility of using intense sound as a deterrent for juvenile Atlantic salmon (Sulmo salar L.) was studied by recording both physiological awareness reactions in an acoustic tube and behavioural avoidance responses in a pool. The measured awareness reactions consisted of decreased heart rate and breathing movements. Three criteria for the awareness reaction were used to compare the effect of different frequencies between 5 and 150 Hz: (i) threshold for spontaneous awareness reactions relative to the hearing thresholds, (ii) magnitude of the change in heart rate, (iii) degree of habituation to sound. After these criteria the lowest frequencies (5–10 Hz) were most effective in eliciting an awareness reaction from the fish. The responses of freely swimming fish to 10 and 150 Hz sounds were studied in an artificial pool. Juvenile salmon showed avoidance responses to 10 Hz stimulation at intensities 10–15 dB above the threshold for spontaneous awareness reactions measured in the acoustic tube. The 150 Hz sound failed to evoke avoidance responses, even at a level 30 dB above the threshold for spontaneous awareness reactions.
Predation by Moses perch, Lutjanus russelli, and blue‐spotted trevally, Caranx bucculentus, on juvenile brown tiger prawn, Penaeus esculentus: effects of habitat structure and time of day
Authors: Laprise R. , Blaber S. J. M.
Published: January 2006

The effects of habitat structure and time of day on predation success of Moses perch, Lutjanus russelli, and blue‐spotted trevally, Caranx bucculentus, feeding on juvenile brown tiger prawn, Penaeus esculentus, were tested in the laboratory. Our experiments demonstrated that both softsubstratum, in which prawns can burrow, and seagrass habitats reduce predation rates by fish during daytime when compared to hard‐substratum habitats. However, the protection offered by burrowing in a soft substratum during daytime disappears at night when prawns become active and are more available to fish. Seagrass structure offers the same protection during both night and day. This is attributed to the structural complexity of the seagrass habitat, as well as the behaviour and disruptive coloration of the prawns. The results suggest that fish predation on juvenile P. esculentus may not be very important in seagrass nurseries but could be very high in other habitats.