bluuebunny/crossref_metadata_2025 huggingface dataset:
Diel food selection of pelagic Arctic charr, Salvelinus alpinus (L.), and brown trout, Salmo trutta L., in Lake Atnsjø, SE Norway
Authors: Dervo B. K. , Hegge O. , Hessen D. O. , Skurdal J.
Published: January 2006

Patterns of diel food selection in pelagic Arctic charr, Salvelinus alpinus (L.) and brown trout, Salmo trutta L. were investigated in Lake Atnsjo, SE Norway, by gillnet sampling during July‐September 1985. Arctic charr feed almost exclusively on zooplankton both day and night, while brown trout had a diurnal shift in diet. For this species zooplankton made up a considerable part of the diet in the daytime, while at night the diet consisted mainly of surface insect and chironomid pupae. Both species had a selective feeding mode on zooplankton during the day and night. Arctic charr had a higher gill raker number and a denser gill raker spacing compared with brown trout. Still, the differences in prey size between the two species were small. We argue that the observed differences in food selection between Arctic charr and brown trout can be explained by differing abilities to detect food items under low light conditions.
Daily ration estimates for yellowfin sole, Limanda aspera (Pallas), based on laboratory consumption and growth
Authors: Smith R. L. , Paul A. J. , Paul J. M.
Published: January 2006

Several estimates of minimal energy requirements for yellowfin sole were made. Energy expenditures of 1.6, 4.1 and 8.3 cal g−1 day−1 were obtained from starvation weight loss, standard metabolism and maintenance ration procedures, respectively, at 6° C. The temperature effect on energy requirement was reflected in the Q10 values for starvation weight loss (2.0), standard metabolism (6.3) and maintenance ration (6.5).

Both energy intake and weight of food were linearly related to, and good predictors of, laboratory growth. These relationships were used to estimate the food and energy intake necessary for yellowfin sole to achieve a year's growth in the natural environment. Based on a caloric value of 2.0 kcal g−1 of food (herring fillets), yellowfin would require 0.35 to 0.39% body weight day−1 at 3° C to achieve the mean growth rate exhibited in the Bering Sea. To achieve Gulf of Alaska growth rates at 5 to 6° C, yellowfin would require 0.63% body weight day−1. Based on a caloric value of 0.57 kcal g−1 of food (chopped octopus), yellowfin would require 0.83% body weight per day to achieve the Gulf of Alaska growth rate (6° C). These requirements based on the calorific value of herring fillets, which are three to five times higher than previous estimates of daily ration in this species, are probably conservative estimates since many of their prey species have a lower energy content.
The influence of prey size and abundance, and individual phenotype on prey choice by the three‐spined stickleback, Gasterosteus aculeatm L.
Authors: Hart P. J. B. , Ison S.
Published: January 2006

Prey selection behaviour of three‐spined sticklebacks, Gasterosteus aculeatus L., was studied in two experiments. Where possible, the experimental apparatus satisfied the assumptions of the simplest optimal diet model (the basic prey model); prey were presented sequentially, the fish could not search for and handle prey at the same time, and net energy gain, handling time and encounter rate were fixed. Experiment 1 presented fish with a range of Asellus sizes so that pursuit (p) and handling (h) time could be related to prey size. Published energy values of Asellus together with pursuit and handling times were used to calculate E/(p+h) for Asellus measuring 3,4,5,6,7 and 9 mm. Pursuit times did not differ with prey size but handling times did. E/(p+h) was very variable particularly at the larger prey sizes. Experiment 2 presented fish with two sequences of prey differing in the encounter rate with the most profitable prey sizes. Fish did not select the diet predicted by the basic prey model tending to always ignore the largest prey even when net energy gain would have been maximized by including them in the diet. Further analysis showed that the probability of a prey size being taken was a function of prey size, fish stomach fullness and encounter rate. It is concluded that the basic prey model is too simple to capture the behaviour of the fish. One of its main faults is that the changing state of the fish through the feeding bout is ignored.
The blood vasculature of the gastrointestinal tract in chinook, Oncorhynchus tshawytscha (Walbaum), and coho, O. kisutch (Walbaum), salmon
Authors: Thorarensen H. , McLean E. , Donaldson E. M. , Farrell A. P.
Published: January 2006

The venous and arterial vasculature of the chinook and coho salmon gastrointestinal tract were examined using corrosion casts and India ink injection techniques. Observations derived from 28 individuals of various sizes and of both sexes were used to construct simplified venous and arterial plans. Examination of the blood vasculature revealed the presence of a variety of anastomoses hitherto undescribed in teleosts.
Glycosaminoglycan composition of anguilliform and elopiform leptocephali
Authors: Pfeiler E.
Published: January 2006

Whole‐body glycosaminoglycan (GAG) composition of leptocephalous larvae was studied in eight eel (Anguilliformes) species, representing five different families (Congridae, Moringuidae, Muraenidae, Nettastomatidae and Ophichthidae) and the bonefish (Elopiformes: Albulidae: Albula vulpes). The extracted GAGs were identified by cellulose acetate electrophoresis, using standard GAGs as a reference, and by their susceptibility to GAG‐degrading enzymes (keratanase, chondroitinase ABC, chondroitinase AC and testicular hyaluronidase). The principal GAG in bonefish larvae was keratan sulphate. However, keratan sulphate was not the main GAG in any of the eel leptocephali studied, althoughit was present in small amounts in most species. The identities of the principal GAGs in eel leptocephali are still unknown, but the most likely possibilities include hyaluronic acid, chondroitin, and chrondroitin sulphate. In addition, a high degree of variability existed in the total amount of GAG that could be extracted from the different eel species and in the electrophoretic migration patterns of the extracted GAGs. Although a basic similarity is thought to exist in the body plan and developmental strategy of all leptocephali, the present results indicate that the GAG composition of the gelatinous body matrix is variable.
Sediment processing by gizzard shad, Dorosoma cepedianum (Lesueur), in Acton Lake, Ohio, U.S.A.
Authors: Mundahl N. D.
Published: January 2006

Gizzard shad are primarily detritivorous in Acton Lake, a 253‐ha impoundment in southwestern Ohio, U.S.A. To determine the magnitude of sediment utilization by the gizzard shad population in Acton Lake. I used data on population density and age structure, daily ration, and feeding selectivity in estimating the mass of sediments processed by shad daily from April through November. At densities of 4595–10 645 fish ha−1(wet weight biomass = 90–121 kgha 1), gizzard shad could process 3.8–23.0 kg of dry sediments ha−1 day 1. On average throughout the growing season, gizzard shad could process a dry mass of sediments each day equivalent to 13% of shad wet weight biomass. Because of the high rate of sedimentation (> 700 kg dry sediment ha−1 day−1) in Acton Lake, gizzard shad can process < 4% of the freshly deposited sediments each day, and therefore are likely to have little effect on benthic community dynamics in the system.
The effects of starvation and refeeding on plasma amino acid levels in carp, Cyprinus carpio L., 1758
Authors: Blasco J. , Fernández J. , Gutiérrez J.
Published: January 2006

Plasma amino acid (AA) levels of carp, Cyprinus carpio L., 1758, were analysed after various periods of starvation as well as after 12 days of refeeding. The levels were compared to control groups, which had been previously fasted for 24 h. A positive correlation between dietary and plasma essential amino acid (EAA) concentrations was observed in all of the control groups.

The effect of starvation on the dynamics of AA concentration was different according to the period of starvation. Fasting already produced a decrease of total α‐AA levels at 2 days, and these low levels were maintained until 5 and 8 days. These short periods of fasting affected the levels of EAA (especially branched‐chain AA) more than those of non‐essential amino acids (NEAA). The only AA that increased was Ala, which rose at 5 days of starvation, surpassing the levels of the control group. These high levels were maintained until 19 days of starvation.

A different situation was observed at 19 days, when an important increase of total α‐AA levels was produced, the branched‐chain AA being the most notable among EAA and Glu/Gln among NEAA. Later, at 50 days of starvation, total α‐AA, EAA (except Leu and Ile) and NEAA decreased.

After 50 days of starvation, 12 days of refeeding did not modify the levels of EAA and NEAA, and their concentrations were lower than those of the control group, which presented an increase of total AA at this time. The differences observed on the changes of individual AA levels are discussed.
Robertsonian polymorphism in plaice, Pleuronectes platessa L., and cod, Gadus morhua L., (Pisces Pleuronectiformes and Gadiformes)
Authors: Fan Z. , Fox D. P.
Published: January 2006

Karyotypic analysis of plaice, Pleuronectes platessa L., and cod, Gadus morhua L., revealed that the chromosome numbers in both species vary but that chromosome arm numbers (NF) stay constant. The C‐, Q‐ and R‐banding patterns also confirmed that the population of plaice studied shows Robertsonian polymorphism. The tendency of reduction in chromosome number in fishes suggests that Robertsonian fusions play a role in karyotype evolution in fishes.
Haemoglobin isomorph abundances in splenectomized rainbow trout, Oncorhynchus mykiss (Walbaum)
Authors: Murad A. , Houston A.
Published: January 2006

Rainbow trout, Oncorhynchus mykiss (Walbaum) were rendered acutely anaemic by immersion in phenylhydrazine HC1 at 5° C. Following splenectomy or sham operation erythropoiesis was induced by gradual warming. No consistent or significant differences in red cell numbers, haemoglobin, haematocrit, mean erythrocytic volume or haemoglobin or haemoglobin isomorph system organization were evident during or following recovery. It is unlikely, therefore, that reported acclimatory adjustments in haemoglobin isomorph abundances can be attributed to site‐related differences in erythroid cell lineages.
Feeding ofScardinius acarnanicus Stephanidis, 1939 (Pisces: Cyprinidae) from Lakes Lysimachia and Trichonis, Greece
Authors: Iliadou K.
Published: January 2006

The feeding of the endemic freshwater fish Scardinius acarnanicus Stephanidis, 1939 has been studied from the content of its intestine and from the results of feeding experiments in the laboratory. This species appears to be phytoplanktophagous when young, whereas as an adult, it becomes macrophytophagous. No difference was observed in the diet of males and females.
Chondrocranium morphology of northern Red Sea triakid sharks and relationships to feeding habits
Authors: Waller G. N. H. , Baranes A.
Published: January 2006

The structure of the neurocranium, mandibular arch and hyoid arch of I. omanensis (Norman) and M. mosis Hemprich & Ehrenberg is described. Comparisons between these species and other triakids and between triakids and carcharhinoids are given. Differences in the size, weight and structure of the mandibular arch, including its associated ligaments and jaw suspension, are shown to be related to feeding habits. Dental characters for both species are examined and differences are considered in relation to diet. Structural elaborations of the nasal capsules in I. omanensis are described in relation to protrusion of the upper jaw during biting. Comparable neurocranial features are poorly developed in M. mosis where the upper jaw shows little discernable anterior movement. The optic region is enlarged in both species in relation to nasal and otic areas of the neurocranium.
Study of the soluble white muscle tissue proteins from fifteen Sparidae species
Authors: Basaglia F. , Marchetti M. G.
Published: January 2006

Soluble proteins of white skeletal muscle tissue of 15 species of Sparidae were analysed. Species‐specific electrophoretic and isoelectric focusing patterns were found. Some bands exhibited the same mobility at genus level or at subfamily level, others differed significantly.

Considerable similarity was observed in the species of the genera Spams, Pagellus and Diplodus. Significant differences in the protein bands were noted between the contained subfamilies Denticinae, Sparinae and Boopsinae, confirming the existence of three separate phyletic lines within the family Sparidae.

This study has shown that in these species there is a similarity between classifications based on morphological data and those derived from biochemical studies.

Variation within species can be corrected for by carrying out multiple inter‐specific comparisons and determining the variance of the similarity coefficients. Closely related species have similar patterns and, thus, higher similarity coefficients.

The discrepancy in similarity matrices based on morphology and white skeletal muscle tissue proteins of sea bream species shows that electrophoretic methods provide additional information relevant to the systematics of fishes.

Further work on comparison on soluble red muscle proteins of these species is proposed.
Morphological variability among seven populations of brown trout, Salmo trutta L., in Greece
Authors: Karakousis Y. , Triantaphyllidis C. , Economidis P. S.
Published: January 2006

Morphological variation in five meristic and 21 morphometric characters was examined in the brown trout, Salmo trutta L., from seven distinct streams and rivers from N and NW Greece. Variation within each sample, estimated as the multivariate generalization of the coefficient of variation, did not vary substantially among the populations. The phenetic relationships of these populations were examined using the stepwise discriminant analysis. The taxonomic implications of these results are discussed.
The influence of metabolic rate on otolith increment width in Atlantic salmon parr, Salmo salar L.
Authors: Wright P. J.
Published: January 2006

The influence of metabolic rate on otolith accretion in Atlantic salmon parr was investigated by comparing oxygen consumption rate and increment width in fast and slow growing individuals. Increment width was found to be positively correlated to mean daily oxygen consumption in both fast growing (S1) and slow growing (S2) parr. The results support previous suggestions that a process related to metabolic rate, rather than somatic growth, governs the rate of otolith accretion.
Geographical patterns in the population genetics of Atlantic salmon, Salmo salar L., on U.S.S.R. territory, as evidence for colonization routes
Authors: Kazakov R. V. , Titov S.F.
Published: January 2006

From data on interpopulation genetic structure of the Atlantic salmon from the rivers of the Barents, White and Baltic Sea basins on U.S.S.R. territory, it is suggested that salmon colonized the Onega and Pechora River basins from the Baltic drainage as the last ice‐sheet receded, and that the Kola Peninsula rivers were colonized separately from the Barents Sea area.
Factors affecting the activity of two species of eel (Anguilla spp.) in a small New Zealand lake
Authors: Jellyman D. J.
Published: January 2006

Fyke net captures of both the shortfinned eel, Anguilla ausrralis Richardson, and the longfinned eel. A. dieffenbachü Gray, were recorded over a 4‐year period in Lake Pounui. New Zealand. Eel activity measured as catch per unit effort (CPUE) was correlated to 36 indices of water temperature water level, barometric pressure, amount of light at night and lunar period using multiple regression analysis. For longfinned eels, water temperature was the only individual parameter significantly related (P<0.001) to CPUE. The multiple regression model was improved (R2= 0.29. P <0.01) by the addition of lunar phase and change in barometric pressure. Water level was the most important parameter in the model for shortfinned eels, although water temperature and change in barometric pressure were significant influences in the predictability of the model (R2= 0.51. P<0.001.
The effects of spinal nerve section on responses of melanophores in the minnow, Phoxinus phoxinus(L.)
Authors: Amiri M. H.
Published: January 2006

A continuous observation apparatus was used to study the responses of Phoxinus phoxinus melanophores to illuminated black/white backgrounds and their reversal. The fish. Although confined, showed maximum melanosome dispersion (MI 5) and maximum melanosome aggregation (MI 1) when exposed to illuminated black and white backgrounds respectively. Melanophores affected by spinal nerve section showed full melanosome dispersion and the affected area appeared as a black band. The affected melanophores marginally and gradually aggregated their melanosomes if the fish was exposed to an illuminated white background for about a week. The responses of these melanophores to illuminated black and white backgrounds and their reversal indicates that the dispersal of their melanosomes in response to a black background is much faster than their aggregation in response to a white background. It is concluded that an active mechanism is involved and possible factors controlling it are discussed.
Daily growth increments in the otoliths of Atlantic salmon parr, Salmo salar L., and the influence of environmental factors on their periodicity
Authors: Wright P. J. , Rowe D. , Thorpe J. E.
Published: January 2006

Daily increments were demonstrated in the sagitta otoliths of fast‐ and slow‐ growing Atlantic salmon parr, Salmo salar L., when held under natural photoperiod and temperature. Otolith increments continued to be deposited at a daily rate when fish were held under constant light and/or temperature and on single or multiple feeding regimes. However abnormally short photoperiods of 6L: 6D induced two increments per day. The results suggest that an endogenous rhythm, synchronized lo light/dark transitions within a 24 h period, controls otolith increment deposition.
Cardio‐respiratory synchronization and myocardial function in hypoxic carp, Cyprinus carpio L.
Authors: Glass M. L. , Rantin F. T. , Verzola R. M. M. , Fernandes M. N. , Kalinin A. L.
Published: January 2006

Moderate hypoxia (Pio2, = 50 mmHg) caused tachycardia in carp, Cyprinus curpio Linnaeus, whereas severe hypoxia (Pio2, from 30 to 5 mmHg) coincided with bradycardia accompanied by alterations of the waveforms of the electrocardiogram. A cardio respiratory synchronization developed during hypoxia and was maintained during bradycardia. The data raised the question: Does hypoxic bradycardia in part result from myocardial dysfunction or only from regulatory adjustments?
Stream channel experiments on downstream movement of recently emerged trout, Salmo trutta L. and salmon, S. salar L.—I. Effect of four different water velocity treatments upon dispersal rate
Authors: Crisp D. T. , Hurley M. A.
Published: January 2006

Four experimental stream channels were used to study instantaneous downstream dispersal rates of young trout, Salmo trutta L., and salmon, S. salur L., relative to four different water velocities.

Young salmon showed a high rate of dispersal at a low velocity of 7.5 cm s−1 and lower rates at higher velocities of 25 to 70cm s−1. Trout showed their lowest rate at 25cm s−1 with a slightly higher rate at 7.5 cm s−1 and increasingly higher rates at velocities in excess of 25 cm s−1. These results are consistent with field observations on the velocity preferences of young trout and salmon.
Stream channel experiments on downstream movement of recently emerged trout, Salmo trutta L., and salmon, S. salar L.—11. Effects of constant and changing velocities and of day and night upon dispersal rate
Authors: Crisp D. T. , Hurley M. A.
Published: January 2006

Four experimental stream channels were used to study instantaneous downstream dispersal rates of young trout and salmon relative to day and night, constant low and high water velocities and changes of velocity from high to low and vice versa.

At high and low velocity for trout and at high velocity for salmon, the dispersal rate was higher by night than by day. Changes of velocity during daytime from high to low or low to high for trout and from high to low for salmon, were associated with much higher dispersal rates than were constant velocities.
Stream channel experiments on downstream movement of recently emerged trout, Salmo trutta L., and salmon, S. salar L.—111. Effects of developmental stage and day and night upon dispersal
Authors: Crisp D. T.
Published: January 2006

Four experimental stream channels were used to examine the temporal pattern of downstream dispersal of young salmon and trout at four constant water velocities from the time of emergence from the gravel onwards.

At low water velocities (c. 8.0 cm s −1) young salmon showed a high rate of dispersal which was maintained until a very low population density was attained. At higher velocities salmon showed a lower rate of dispersal and the final population density was higher. Trout showed a low dispersal rate at low velocity and higher rates at higher velocities. However, the final trout population density was similar at all water velocities because the low dispersal rate observed at the low velocity persisted for a much longer period than did the higher values at the higher water velocities. The results do not support the view that young salmonids have a narrow and definable period of sensitivity to water velocity.

Dispersal rates were significantly higher by night than by day (P <0.001) at all velocities for both fish species.
Population dynamics and community analysis of the parasite fauna of juvenile spot, Leiostomus xanthurus (Lacepede), and Atlantic croaker, Micropogonias undulatus (Linnaeus), Sciaenidae) in two estuaries along the middle Atlantic coast of the United States
Authors: Thoney D. A.
Published: January 2006

The parasite communities of juvenile spot, Leiostomus xanthurus Lacepede, and Atlantic croaker, Micropogonias undulatus (Linnaeus), changed with size, season. and geographical area. A total of 21 parasitic species occurred in juvenile spot and 19 occurred in juvenile croaker from Chesapeake Bay and Pamlico Sound. More parasitic species were acquired as juveniles grew, diversified their diets, and consumed larger numbers of intermediate hosts. They were also exposed to infective larvae of parasites with direct lifecycles over long periods of time. Equibility and, thus, diversity were depressed because of large numbers of Diplomonorchis /eiostomi Hopkins, I941 that dominated the parasite communities of both species. Although spot and croaker from both estuaries shared eight and six parasites, respectively, many of these non‐specific parasites (generalists) were more common in both spot and croaker from one estuary than from the other. All species occurring in both hosts have indirect life cycles suggesting that the availability of certain intermediate hosts as prey was an important determinant of infection. Estuary of residence was clearly as important as host species identity in determining parasite community structure.
Fine structure of hepatocytes in juvenile grey mullets: Liza saliens Risso, L. ramada Risso and L. aurata Risso (Teleostei, Mugilidae)
Authors: Biagianti‐Risbourg S.
Published: January 2006

Livers of 45 fingerling grey mullets (Liza sp. 5‐15 cm long) were subjected to light microscopy, transmission electron microscopy and enzyme cytochemical examination. The hepatic structure was found to be comparable in all three Liza species. As in other fish species, Liza liver parenchyma is arranged in cords (or dual‐plated laminae, in sections parallel to the sinusoidal axis). Hepatocytes showed numerous microvilli in their perisinusoidal and canalicular areas. They contained a centrally located nucleus, fairly large areas of rough endoplasmic reticulum, consisting mainly of parallel cisternae, and pools of glycogen. A few small lipid droplets were evenly distributed in the cytoplasm. The Golgi fields, between the canaliculus and the nucleus, consist mainly of dictyosomes, lysosomes and autophagic vacuoles. Acid phosphatase activity was cytochemically localized to reaction products in secondary lysosomes and lipofuscin granules. A comparison between grey mullet liver and that of other teleosts was made.
Energetic cost of spawning in male and female Atlantic salmon (Salmo salar L.)
Authors: Jonsson N. , Jonsson B. , Hansen L. P.
Published: January 2006

Energetic expenditure during spawning of male and female 1 ‐sea‐winter Atlantic salmon, Salmo salar L., was measured. Before spawning, the somatic energy content per unit weight did not differ between the sexes. The testes content offat was 0.24, of carbohydrate 8.89, of water 1.21 and of ash 1.61 times as high as that of the ovaries. Just prior to spawning, mean gonadosomatic index (GSI; wet weight, %) in males was 4.36 and in females 20.26, and expressed as energy ratios (kJ, %) 4.47 and 27.75, respectively. During spawning the energy loss of male soma was higher (35.57%) than that of females (25.00%). This was a result of higher loss of fat in males than in females. Total energy cost of spawning in males and females was on average 51.8 and 51.4%, respectively.
Reproductive isolation and the nest sites of Lake Malawi chambo, Oveochvomis (Nyasalapia) spp.
Authors: Turner G. F. , Witimani J. , Robinson R. L. , Grimm A. S. , Pitcher T. J.
Published: January 2006

The nest sites of chambo, Oreochromis (Nyusalupia) spp. were surveyed in the vicinity of Cape Maclear, Lake Malawi. O. karongae (Trewavas) nested at depths of 0.5 to 28 m, while O. lidole bred at depths greater than 17 m. Nesting areas overlapped between these two species. O. lidole (Trewavas) nests were generally larger than those of O. karongae. Both species bred from September to March. Contrary to previous suggestions, the two chambo species were not reproductively isolated by breeding depth, season, or beach type.
Post‐impoundment changes in the fish fauna of Lake Itezhi‐tezhi, Zambia
Authors: Kapasa C. K. , Cowx I. G.
Published: January 2006

The fish fauna of the newly inundated Lake Itezhi‐tezhi, Zambia was observed between 1980 and 1985. Marked changes in the community structure were identified. The most obvious were a decline in species diversity and a shift in species composition from acommunity with a preponderance of Alesles lateralis (Boulenger) (Characidae), to one dominated by cichlids. These changes were primarily due to members of the families Cyprinidae, Mormyridae and Schilbeidae being unable to adapt to the new environmental conditions, such as spawning and feeding grounds, and their inability to cope with fluctuating water levels in the lake. It was suggested that a sound fishery data collection system be implemented to provide reliable information on which to base management policy.
Effects of dietary zinc on the assimilation efficiency of carp (Cyprinus cavpio L.)
Authors: Brafield A. E. , Vkoodie A.
Published: January 2006

Adding zinc to the diet of carp lowered assimilation efficiency (AE) proportionately. AE values were higher (and higher proportions of zinc were absorbed) when zinc proteinate replaced zinc sulphate.
Biochemical genetics and fishery management: an historical perspective
Authors: Utter F. M.
Published: January 2006

This paper traces the development of applications of biochemical genetic methods to problems of fishery management over a period of four decades. In the 1950s, details of presumed genetic structuring offish species appeared destined for revelation through Mendelian characters identified by immunogenetic procedures. In the 1960s, immunogenetic methods were displaced by protein electrophoresis, with a proliferation of reports of genotypic and allelic data for protein‐coding loci. In the 1970s, disagreement about the biological significance of protein polymorphisms delayed acceptance of management applications of this variation. In the 1980s, management applications included identification of relationships among populations, analyses of mixed stock fisheries, and uses in fish culture, conservation biology and forensics. The complementary relationship between protein electrophoresis and nucleic acid technologies is stressed, with a plea to recognize the unique attributes of properly applied protein electrophoresis in fishery management.
Population structure of Atlantic herring, Clupea harengus L.
Authors: Jørstad K. E. , King D. P. F. , Naevdal G.
Published: January 2006

During the last decade, genetic studies have been carried out on samples of Atlantic herring, CIupea harengus L., from the Baltic, North Sea, British Isles, Norwegian sea‐waters and in the western part of the North Atlantic Ocean. Based on direct comparisons of samples drawn from several areas, the available information on allozyme variation was compiled into a comparable data set and analysed for population structure and genetic distance. The results are discussed in relation to the present stock model for herring.
Genetic structure and relationships among anadromous and landlocked populations of rainbow smelt, Osmerus mordax, Mitchill, as revealed by mtDNA restriction analysis
Authors: Baby M.‐C. , Bernatchez L. , Dodson J. J.
Published: January 2006

Larvae of anadromous rainbow smelt originating in various spawning tributaries are retained in the St Lawrence estuary. We proposed that these smelt represent one population genetically differentiated from adjacent populations characterized by geographically distinct larval retention areas. We also analysed four landlocked populations to evaluate the phylogenetic basis of dwarf and normal‐sized phenotypes and their relation to an adromous smelt. A phylogenetic distinction was revealed between anadromous and landlocked smelt, with only one of the two mtDNA phylogenetic groups of anadromous fish observed among landlocked smelt. Significant geographical heterogeneity in the distribution of mtDNA genotypes was observed among landlocked smelt, suggesting that dwarfism in smelt may be polyphyletic in origin. St Lawrence smelt were genetically identical but distinct from adjacent populations, supporting the proposition that population genetic structure reflects the number of larval retention zones rather than spawning sites.
Incongruent estimates of population differentiation among brook charr, Salvelinus fontinalis, from Cape Race, Newfoundland, Canada, based upon allozyme and mitochondrial DNA variation
Authors: Ferguson M. M. , Danzmann R. G. , Hutchings J. A.
Published: January 2006

We determined the amount and temporal stability of genetic differentiation among brook cham sampled from five rivers on Cape Race, Newfoundland, with an electrophoretic analysis of 42 protein coding loci. Fish from four of these rivers were analysed for restriction fragment length polymorphisms in mitochondrial DNA (mtDNA). A single mtDNA clone was observed in all rivers sampled, except one, where 47% offish were from a different and relatively divergent clone (0.31 % sequence divergence). In contrast, Cape Race brook charr show large amounts of genetic differentiation at six enzyme coding loci; Nei's genetic distance ranged between 0,020 and 0.048. This differentiation is relatively stable as no significant differences in allele frequencies were detected between fish sampled from two rivers over two consecutive years. The most divergent population based on protein polymorphism is not that with two mtDNA clonal lineages. In contrast to the commonly held view, mtDNA analyses do not necessarily provide greater resolution of population structure than allozyme analyses.
Mitochondrial DNA variation of Salvelinus species found in Finland
Authors: Partti‐Pellinen K. A. , Elo K. , Palva T. K. , Tuunainen P. , Hakumaki M. O. K.
Published: January 2006

Mitochondrial DNA (mtDNA) was purified from the Arctic charr, Salvelinus alpinus, the brook charr, Salvelinus fontinalis, and the lake charr, Salvelinus namaycush, and digested with restriction enzymes Ava II, Hinf I, EcoR V, Pst I and XbaI. Two Arctic charr samples were from natural populations and they represented two different morphotypes of Arctic charr. All other studied populations were hatchery maintained. Eight additional restriction enzymes and double digestions were employed to study morphotypes of Arctic charr. We distinguished two morphotypes with restriction enzyme Nci I. Sequence divergence among mtDNA types was 2.9–3.8% between S. alpinus and S. fontinalis, 3.4–4.6% between S. alpinus and S. namaycush, and 4.7–5.3% between S. fontinalis and S. namaycush. lntraspecific variation was lowest in Arctic charr, the average of nucleon diversity for three populations being 0.179, while for brook charr and for lake charr nucleon diversity was 0.334 and 0.550, respectively. According to the number of mtDNA types, it is obvious that introduction to Finland and hatchery propagation have not greatly affected the mtDNA variation of brook charr or lake charr.
Genetic differentiation among chum salmon, Oncorhynchus keta (Walbaum), from Primorye and Sakhalin
Authors: Ginatulina L. K.
Published: January 2006

Mitochondrial DNA (mtDNA) was examined in six wild populations of chum salmon (Oncorhynchus keta Walbaum) distributed over the Primorye Region which extends approximately 1000 km along the Sea of Japan coast, and six populations from Sakhalin, using restriction enzyme analysis. By means of two restriction enzymes (Bam HI and Eco 81I) eight mtDNA clonal lines were revealed in the 346 chum salmon studied. Mitochondrial DNA variants grouped the fish into two major clusters representing the Primorye and Sakhalin regions. Analysis of different chum salmon generations showed stability in the temporal population genetic structure in the three Primorye populations studied, but instability in the Sakhalin population of the Naiba River. We succeeded in detecting four major mtDNA clonal variants in Primorye chum salmon. The geographic distribution of clonal frequencies in Primorye populations has a clinal U‐shape associated with the north‐south axis of the Primorye region. On the whole, Sakhalin populations are less heterogeneous than Primorye ones. Two hatchery‐seeded stocks from south west Sakhalin showed no mtDNA clonal variation.
Effects of starvation on the formation of daily growth increments in the otoliths of milkfish, Chanos chanos (Forsskål), larvae
Authors: Tzeng W.‐N. , Yu S.‐Y.
Published: January 2006

The effects of starvation on daily growth and increment formation in the otolith were examined using a double oxytetracycline‐labelling method on larval milkfish, Chanos chanos (Forsskål), reared under different feeding regimes. The results indicated that the differences in body and otolith growth between the larvae fed once and three times a day were not significant, and that the otolith growth increment was deposited daily in both groups of fed larvae. In contrast, the starved larvae grew at a slower rate than fed larvae in body length and otolith dimensions, and the otolith growth increment in the starved larvae was not deposited on a daily basis. After undergoing starvation, the larvae were unable to recover their normal growth either in otolith increment deposition or in body and otolith growth even though they were fed. Therefore, the application of ageing techniques based on counting otolith growth increments seems to be inaccurate for starved larvae.
Temporal patterning of electric organ discharges in the African electric catfish, Malapterurus electricus (Gmelin)
Authors: Rankin C. H. , Moller P.
Published: January 2006

This paper is the first detailed analysis of situation‐specific temporal patterning of electric organ discharges (EODs) in a strong electric fish. Using a resident‐intruder paradigm EODs were recorded during interactions between dyads composed of Malapterurus electricus (Gmelin) and four different types of fish: (1) conspecifics; (2) large prey‐type mid‐water fish, goldfish (Carassius auratus, Linnaeus 1758) and tilapia (Oreochromis melanotheron, Rüppel, 1852); (3) a sympatric competitor, Polypterus palmas (Ayres 1850) and (4) a larger, threatening catfish, Clarias sp.

An analysis of the EODs emitted showed that in the presence of conspecifics the average EOD volley consisted of a single long‐duration, low frequency train of EODs. The presence of the midwater fish (goldfish and Tilapia) elicited volleys consisting of two short trains, and P. palmas elicited long duration volleys with two trains and long inter‐train intervals. Finally, an attacking Clarias resulted on average in volleys consisting of two high‐frequency trains of EODs. With nonconspecific partner species resident electric catfish emitted volleys with more pulses, more trains that were longer in duration and higher in frequency than the EODs in volleys emitted by intruder electric catfish with the same species stimulus fish.
Abundant males in populations of a selfing hermaphrodite fish, Rivulus marmoratus, from some Belize cays
Authors: Turner B. J. , Davis W. P. , Taylor D. S.
Published: January 2006

The killifish Rivulus marmoratus is the only known selfing hermaphroditic vertebrate, and males of the species are usually exceedingly rare or non‐existent in nature. Collections on several Belize cays in 1988 and 1989 yielded 13.5–24% males. Factors responsible for this unusually high proportion of males are currently not understood. Likewise, the biological significance of males in populations which otherwise consist of selfing hermaphrodites (with internal fertilization) is problematic and awaits further study.
Mugil cephalus L.—a first British record and a further 5°N
Authors: Reay P. J.
Published: January 2006

The occurrence of a 29 mm juvenile Mugil cephalus in the Camel estuary at 50°30′ N represents the first British record of this widespread tropical and subtropical species. Its origins, however, are obscure.
Food intake and growth in the blue‐spotted trevally, Caranx bucculentus Alleyne and Macleay 1877, with reference to predation on penaeid prawns
Authors: Smith R. L. , Salini J. P. , Blaber S. J. M.
Published: January 2006

Blue‐spotted trevally, Caranx bucculentus, were fed different rations of pilchard and prawn in order to investigate feeding and growth relationships. Maintenance rations at 25.5° C amounted to 3.7% B.W. day−1 and 2.7% B.W. day−1 for prawns and pilchards, respectively. Additional feeding experiments at 28.9° C yielded a maintenance ration of prawns of 3.8% B.W. day−1, suggesting there is very little if any temperature effect on the feeding‐growth relationship over the range studied. Fish fed twice or more each day consumed about 7.3 ± 1.4% B.W. day−1.

Given the biomass of this trevally in Albatross Bay, Gulf of Carpentaria, and the contribution of prawns to its diet, we estimate consumption of commercial prawns at 25 ± 5 g.ha−1 day−1 or 11 g kg−1 day−1.
Age, growth and mortality of red bandfish, Cepola macrophthalma (L.), in the western Aegean Sea (Greece)
Authors: Stergiou K. I. , Economidis P. , Sinis A.
Published: January 2006

Age, growth and mortality of red bandfish, Cepola macrophrhalma (L.), from the western Aegean Sea were studied using the otoliths from 1113 fish and the length and weight of 3351 fish. Two regions were established (north and south of the Euripos Strait). The red bandfish grows allometrically (slope of length‐weight regressions ≤2) and relatively rapidly until age 4 or 5 years. It is proposed that this rapid linear growth represents an adaptation which evolved to reduce the vulnerability of red bandfish to whole‐fish swallowers. Back‐calculated lengths‐at‐age showed significant differences between regions and between sexes. Males were larger than females after age 2 years. Maximum age of northern fish was also higher than southern fish (8 and 5 years respectively). Southern fish grow at a faster rate (K=0.379) but to a significantly smaller size (Lx=424.8mm t.l., Wx=25.1 g) than northern fish (K=0.214, Lx=676.1 mm t.l., Wx=90.9 g). Mortality rates (total and natural instantaneous mortalities) of southern fish were also higher than northern fish. We suggest that these variations represent responses to the different conditions of temperature and food availability prevailing in the two regions.
Interspecific and intraspecific variation in resistance to ichthyophthiriasis among poeciliid and goodeid fishes
Authors: Clayton G. M. , Price D. J.
Published: January 2006

A study was undertaken on genetic variation in resistance to infection by Ichthyophthirius multifiliis in two goodeid (Ameca splendens and Ilyodon xantusi) and two poeciliid species (Xiphophorus maculatus and Xiphophorus variatus), and among four strains of X. maculatus (red, red wagtail, yellow comet tail, blue). Analysis of infection data was performed with a generalized linear interactive modelling package (GLIM). Partitioning of the variation was such that the minimal variation attributable to each of several factors was computed. Size of fish, parasite isolate, temperature/tank effects, and various interactions all affect infection levels. Removal of these effects allowed the identification of highly significant differences in both inter‐ and intraspecific variation in resistance. Three distinct groups of fish were identified in terms of their resistance. Species recently derived from wild populations (the two goodeids) were more susceptible than the two poeciliid species which have a much longer history of domestication. The blue strain of X. maculatus had significantly higher resistance than the other three strains.
Bias in calculating growth rates in cod (Gadus morhua L.) due to size selective growth and mortality
Authors: Otterå H.
Published: January 2006

Size selective growth and size selective mortality strongly biased the calculation of specific growth rates among juvenile cod in a feeding experiment.
Effects of salinity and weight on routine metabolism in the juvenile croaker, Micropogonias furnieri (Desmarest 1823)
Authors: Aristizabal Abud E. O.
Published: January 2006

Juvenile croakers from a brackish water bay showed minimal oxygen consumption rates at salinities between 17–19.
Chondroitin and keratan sulphate in the epidermal club cells of teleosts
Authors: Ralphs J. R. , Benjamin M.
Published: January 2006

Club cells in the epidermis of the catfish, Corydoras aeneus and the loaches, Acanthophthalmus semicinctus and Botia horae contain chondroitin and keratan sulphate as demonstrated by immunocytochemistry using monoclonal antibodies. Their release from club cells might contribute to the physical support of the epithelium and could help seal damaged tissue.
Comparative examination of soluble red muscle proteins of fifteen Sparidae species
Authors: Basaglia F.
Published: January 2006

Soluble red muscle proteins from the lateral line of 15 Sparidae species were analysed by isoelectric focusing. Species‐specific patterns were found. The species‐specific protein fractions could be correlated with different metabolic activities and with different growth indexes. More protein fractions were identified for Pagellus acarne (Risso) and Diplodus annularis (L.) than for the other 13 species. This would appear to be related to growth index. The existence of red muscle with a greater number of protein bands than white muscle was confirmed in almost all species. The similarity coefficients have shown that closely related species have similar patterns and, thus, higher similarity coefficients. The derived dendrogram agrees with previous classifications based on morphological information.
Olfactory sensitivity to amino acids in the juvenile stages of the European eel Anguilla anguilla (L.)
Authors: Crnjar R. , Slcalera G. , Bigiani A. , Tomassini Barbarossa I. , Magherini P. C. , Pietra P.
Published: January 2006

Scanning electron micrograph observations of the olfactory mucosa from both unpigmented glass eel(GE)andpigmentedelvers(EL)of the European eel, Anguilla anguilla(L.), revealed the presence of various cell types; amongst these, the ciliated and microvillous ones are likely to possess a chcmosensory function. Recording of underwater electro‐olfactograms (EOGs) showed that various amino acids (glycine, L‐alanine, L‐valine, L‐leucine, L‐asparagine, L‐glutamine and L‐methionine) are effective stimulants for the olfactory mucosa. Dose response curves of stimulus concentrations v. EOG amplitudesfit regression linesat both GE and EL stages. Leucine was more stimulatory at the GE than at the EL stage. The stimulatory effect of the other six amino acids tested was similar at both developmental stages. The possible role of olfactory sensitivity in animal behaviour at different developmental stages is discussed.
Initial feeding in migratory brown trout (Salmo trutta L.) alevins
Authors: Zimmerman C. , Mosegaard H.
Published: January 2006

Initial feeding of brown trout was investigated under laboratory conditions. Fifty per cent feeding occurred when yolk constituted approximately 31% of total alevin dry weight, and feeding rate was positively correlated to developmental stage. The possible ecological implications of initial feeding are discussed.
Migration of hatchery reared juvenile Atlantic salmon, Salmo salar L., smolts down a release ladder. 3. Reactions on exiting the ladder
Authors: Greenstreet S. P. R.
Published: January 2006

Twenty‐eight hatchery‐reared Atlantic salmon (Salmo salar L.) smolts were tracked as they left a release ladder and moved through the estuary of the Lussa River and out to sea. Smolt passage through the estuary was fastest at high water and slowest at low water; the reverse of the situation observed for passive objects floating in the surface water layer. At low tide the water channel was effectively a freshwater stream and the smolts behaved in it accordingly, attempting to maintain station. At high water smolts moved downstream with the current close to the water surface. The degree of variation in individual speed through the estuary was the main difference observed between immature S2, stripped mature male S2, unstripped mature male S2 and S1 smolts. Smolts moved directly out of the estuary with no apparent check in their progress. Sea contact times in the vicinity of the river mouth, for both passive objects and smolts, were longest around high water and shortest around low tide. In the sea no differences were observed in the behaviour of the four different smolt types. While passive objects showed no tendency to move off in a particular direction, smolts showed a significant inclination to head off on a southerly bearing.
The bioenergetics of the southern catfish (Silurus meridionalisChen): growth rate as a function of ration level, body weight, and temperature
Authors: Xiao‐Jun Xie , Ruyung Sun
Published: January 2006

A feeding‐growth experiment was conducted in the laboratory on 114 young southern catfish (Silurus meridionalisChen) with initial weights of 8.71–127.9g at 15, 20, 25 and 30°C. The experiment consisted of eight weight‐temperature groups, with five ration levels ranging from starvation to satiation in each group. A multiple regression equation fitted to the experimental data was developed to describe the relation between specific growth rate (SGR) and the three factors, ration level (RL), body weight (W) and temperature (T): SGR = 0.471 + 0.172lnW−0.0443T+0.0682Tln(RL + l). This predicts that with increasing temperature the specific growth rate decreases at lower ration levels and increases at higher ration levels. The equation, SGR =a+bln(RL + l), may be considered as the basic growth model whereais the maintenance metabolism exponent andbis the conversion exponent of the net energy; body weight and temperature influence the two parameters. With this relationship the two antagonistic effects of temperature on growth can be understood, increasing temperature imposes a negative effect on growth due to increment in energy cost for maintenance metabolism, and a positive effect due to higher efficiency of transforming food energy into net energy; the positive effect will increase at higher ration levels. This could also explain why at a restricted ration level relationships between growth and temperature are different in different species.