bluuebunny/crossref_metadata_2025 huggingface dataset:
River flow, Atlantic salmon (Salmo salar L.) movement and rod catch in the Aberdeenshire Dee
Authors: Potts W. T. W. , Malloch A. J. C.
Published: January 2006

The relationship between river flow and rod and net catches of salmon and grilse have been analysed for four of the major fisheries on the Aberdeenshire Dee. On the lower two fisheries there is a good correlation between the rod catch and the average flow on the day of the catch and the preceding 3 days but there is no such correlation at the highest fishery. There is also a good correlation between the annual flow during the rod season and the total annual rod catch at the lowest fishery, while there is an inverse correlation between the flow during the rod season and the net catch. When the nets are off there is no longer any correlation between river flow and rod catch at the lowest fishery.
An electrophoretic investigation of populations of Atherina boyeri Risso, 1810 and A. presbyter Cuvier, 1829 (Teleostei: Atherinidae): genetic evidence in support of the two species
Authors: Creech S.
Published: January 2006

The data obtained using electrophoresis strongly support the specific status of Atherina boyeri Risso, 1810 and A. presbyfer Cuvier, 1829, and thuscontradict the recently proposedsynonymyof the two species. Four populations of A. boyeri and six populations of A. presbyter were assayed for 11 enzymes and general protein using muscle and liver extracts. Eight of the 11 enzymes were shown to be polymorphic at the 95% level. Sixteen loci, encoding 40 putative alleles were consistently resolved in all 10 populations.

The two species were fixed for different alleles at the EST‐3 locus. At the G3PDH locus. with the exception of two heterozygotes, all individuals of each species were also homozygous for different alleles. At the PGM locus the common allele was unique to each species.

The mean Nei's genetic distance (D̄), over all loci, calculated between populations of A. boyeri (D̄= 0.10 ± 0.06); between populations of A. presbyter (D̄= 0.02 D̄ 0.02) and between populations of A. boyeri and A. presbyter (D̄= 0.42 D̄ 0.09) indicated the separateness of the two species.

UPGMA cluster analysis based on genetic distances produced a dendrogram whose principal dichotomy resulted in the formation of two clusters. The ordination of populations in the UPGMA cluster analysis strongly reflected the geographic distribution of populations in both species.
Bimodal size distributions in wild juvenile Atlantic salmon populations and their relationship with age at smolt migration
Authors: Heggenes J. , Metcalfe N. B.
Published: January 2006

A bimodal length distribution developed in an Atlantic salmon population planted as start‐fed fry in a Norwegian stream. The earliest fish to smolt were from the upper modal group.
Protein variation in wild Atlantic salmon, with particular reference to southern Ireland
Authors: Mcelligott E. A. , Cross T. F.
Published: January 2006

The extent of genetic variation in wild Atlantic salmon parr, Sulmo salur L., from river systems in Ireland, Iceland and eastern Canada, was investigated using starch gel electrophoresis. Within Ireland, seven polymorphic enzyme loci (sAAT‐4*, GPI‐1*, IDDH‐1*, IDDH‐2*, IDHP‐3*, MDH‐3* and mMEP‐2*) were screened in nine different rivers and nine tributaries from the River Blackwater. Significant heterogeneity in gene frequencies occurred between riverine samples and between samples from tributaries of the River Blackwater. Variation between tributaries was as great as between rivers elsewhere in the country. Levels of population differentiation were comparable to those found in other regions throughout the range of the species, and temporal stability in gene frequencies was apparent when the results were compared with previously published data. Screening of riverine samples from Iceland and eastern Canada (Newfoundland and New Brunswick) allowed the Irish results to be considered in a broader context. Irish salmon cluster in the western European group, to which may be added Icelandic populations. Salmon from eastern Canada show a high level of genetic distinctiveness from the European group.
Enzymatic polymorphisms in the Argentinian hake, Merluccius hubbsi Marini, of the Argentinian continental shelf
Authors: Roldán M. I.
Published: January 2006

A survey described genetically encoded enzyme variation in 197 adult Argentinian hake, Merhccius hubhsi, collected from 10 sample sites on the Argentinian continental shelf. Four of 11 muscle enzyme loci were polymorphic (PCM*, G3PDH*, EST‐1* and EST‐2*). Genotypes showed no significant difference between males and females. Only one of 37 tests of departure from Hardy‐Weinberg equilibrium showed a significant difference. The allele frequency data were tested for genetic heterogeneity among locations. The overall significance of the total samples and among those from Patagonia Central was primarily due to heterogeneity at the EST‐1* locus. The implications of these findings in a population structure context are discussed.
Effects of sea trout stocking on the population genetics of landlocked brown trout, Salmo trutta L., in the Conwy River system, North Wales, U.K.
Authors: Hauser L. , Beaumont A. R. , Marshall G. T. H. , Wyatt R. J.
Published: January 2006

The effect of the introduction of fry of anadromous sea trout, Salmo trutta L., on the genetic integrity of landlocked brown trout populations was evaluated. Samples were taken from six brown trout populations from streams above impassable waterfalls in the Conwy river system (North Wales, U.K.) in 1989 and 1990. Three of these streams had no known stocking history and three had been stocked with sea trout fry from the lower Conwy system over the last few years. Representatives of these sea trout were collected from two streams in the lower Conwy system and from a hatchery. Allele frequencies at 13 loci, six of which were polymorphic, were determined by starch gel electrophoresis.

The stocked populations were intermediate in their allele frequencies between unstocked brown trout and sea trout samples. A principal component analysis suggested significant numbers of hybrids in all of the stocked streams. This shows that some of the introduced sea trout did not migrate down the falls to the sea, but stayed in fresh water and hybridized with the local population. The significance of this finding for the conservation of the genetic resource of brown trout stocks is discussed.
Phylogeny of Australian species of flatheads (Teleostei, Platycephalidae) as determined by allozyme electrophoresis
Authors: Keenan C. P.
Published: January 2006

Phylogenetic relationships of 24 taxa of Platycephalid fish were examined for up to 40 loci using starch and polyacrylarnide gel electrophoresis. Over 400 different enzyme mobilities were scored. The extent of homoplasy was estimated to be between 5 and 12%. Polymorphism at the 1% level was observed at 26 of the 40 loci. The importance of shared polymorphic alleles in cladistic analysis was endorsed by the different results obtained from multistate and binary coding of alleles. Many loci were shown to contain phylogenetically informative ancestral alleles which appear irregularly in extant species. The polymorphism parsimony method provided the most informative results. Genetic similarities between endemic Australian species from each family stem provide the basis for a major revision of subfamilies and genera within the family.
Biochemical genetic comparison of bighead (Hypophthalmichthys molitrix), silver carp (Aristichthys nobilis), and their hybrids reared in Czechoslovakia
Authors: Slechtova V. , Slechta V. , Hiep Do Doan , Valenta M.
Published: January 2006

Incidental and/or uncontrolled hybridization between silver carp (Hypophthalmichthys molitrix) and bighead (Aristichthys nobilis) represents a serious problem in Czechoslovak aquaculture. This fact affects fitness traits very negatively in successive generations of hybrids. To solve this problem, 1076 individuals in a total of both H. molitrix. A. nobilis, and their hybrids in 12 groups from six rearing facilities were analysed. Twelve protein systems representing 21 presumptive loci were studied to analyse the electrophoretic patterns of their products using horizontal starch gel electrophoresis of blood and tissue extracts. Both species displayed identical electrophoretic patterns in MYO‐I*, LDH‐A*, LDH‐B*, sMDH‐1*, sIDHP‐3*, GPI‐1*, and CK‐I* loci. For a reliable differentiation of both species products of the following nine loci are applicable ALB*, PA*, TF, sMDH‐2*, SOD*, NDH*, MYO‐IF, MYO‐III*, and CK‐2*. In addition, some polymorphic variants in slDHP‐1*, sIDHP‐2*, LDH‐C*, EST‐II*, and GPI‐2* loci are of use as auxillary markers while the other variants are common to both species. A high level of gene introgression was evident through hybridization between both species. All groups declared previously as ‘H. molifrix’ were actually confirmed biochemically to be H. molitrix. However, all groups declared as ‘A. nobilis’ were proved to be a mixture of A. nobilis and its hybrids of different level with H. molitrix. This suggests it is impossible to distinguish between A. nobilis and hybrids using their external morphology only.
Red muscle fibre and capillary dimensions in different sizes of a tilapia, Oreochromis niloticus (Trewavas)
Authors: Kisia S. M. , Hughes G. M.
Published: January 2006

Measurements of muscle dimensions that affect respiration in relation to body weight were carried out in a tilapia, Oreochromis niloticus. The fish used in all measurements weighed 0.65–812.3 g. The data were analysed with respect to body weight using logarithmic transformations (log Y=log a+blog W).

The slopes (b) of the log/log regression lines for weight of body trunk red muscle, average cross‐sectional area of muscle fibre, average number of capillaries in direct contact with a muscle fibre, average capillary contact length with a fibre as a fraction of average fibre circumference and number of capillaries mm2 of fibre cross‐sectional area [NA(cƒ)] were 1.16, 0.221, 0.084, 0.015, and −0.137 respectively.

These results show that there is an increase in muscle cross‐sectional fibre area and number of capillaries in contact with muscle fibres whereas number of capillaries supplying a unit area of muscle fibre decreases during development. There is development of new capillaries with increase in cross‐sectional area of red muscle fibres.
Mitochondrial DNA analysis of Scottish populations of Arctic charr, Salvelinus alpinus (L.)
Authors: Hartley S. E. , Bartlett S. E. , Davidson W. S.
Published: January 2006

Mitochondrial DNA analysis of a total of 82 individuals from seven Scottish populations of Arctic charr (Salvelinus alpinus L.) using restriction fragment length polymorphism and direct nucleotide sequencing of the cytochrome b gene revealed little variation within or between populations. One of 19 restriction enzymes showed a polymorphism that was present in three of the seven populations. Only one nucleotide substitution was detected in a 288 base pair segment of the cytochrome b gene examined in 26 fish. Approximately 4% of the mitochondrial genome was surveyed with these complementary procedures.
Closure of the micropyle during embryonic development of some pelagic fish eggs
Authors: Yamamoto T. S. , Kobayashi W.
Published: January 2006

The fine structure of the egg envelope and micropyle was studied in unfertilized and developing eggs of the flounder Paralichthys olivaceus (Temminck & Schlegel), the Alaska pollack Theragra chalcogramma (Pallas), the Japanese tilefish Branchiostegus japonicus (Houttuyn) and the porgy Pagrus major (Temminck & Schlegel). The outer envelope surface of the unfertilized egg was wrinkled, while the inner surface was folded. The micropyle of the unfertilized egg consisted of a shallow vestibule and a distinct canal. The micropylar region of the inner surface of the envelope had a conical‐ or bowl‐shaped protrusion. In developing eggs, the thickness of the envelope decreased and showed smooth outer and inner surfaces which indicated that it had been stretched tangentially at the time of the perivitelline space formation. The lumen of the micropylar canal was invariably occupied with envelope material. We postulate that the blockage of the micropylar canal is a result of the stretching of the envelope. The closure of the micropyle inhibits sperm and external pathogens from penetrating into the perivitelline space and seems to be involved in both the permanent prevention of polyspermy and the protection of the developing embryo from bacterial infection.
Temporal deposition of incremental and discontinuous zones in the otoliths of Oreochromis niloticus (L.)
Authors: Zhang Z. , Runham N. W.
Published: January 2006

Ultrathin sections of otoliths were prepared and studied with the transmission electron microscope. The discontinuous zone starts to grow at night, 3 h before light‐on, and is completed a few hours after light‐on. The growth of the incremental zone follows immediately afterwards and continues approximately until light‐off. There is little material deposited onto the otolith at night before the start of discontinuous zone deposition.
Predation by Nile perch Lates niloticus (L.) on Oreochromis niloticus (L.), Cyprinus carpio (L.), Mugil sp. and its role in controlling tilapia recruitment in Egypt
Authors: El Gamal A. A.
Published: January 2006

Vulnerability of three fish groups (tilapia, common carp, mullet) to predation by Nile perch Lates niloticus was evaluated. The study was conducted in aquaria and in cages placed in concrete ponds. Common carp Cyprinus curpio was the more vulnerable to predation by Nile perch followed in order by mullet (Mugil cephulus and M. cupito) and Nile tilapia Oreochromis niloricus. Medium‐size Nile perch (30–32 cm t.l.) were able to consume tilapia up to 14 cm t.l., while tilapia of 15 cm total length were not eaten. Ratios of 1 : 10 to 1 : 15 between Nile perch and ready‐to‐spawn females of O. niloticus were found to be adequate to control tilapia reproduction.
The ontogeny of predatory mechanisms in the fifteen‐spined stickleback, Spinachia spinachia (L.)
Authors: Kaiser M. J.
Published: January 2006

Predatory behaviour is similar in juvenile and adult fifteen‐spined sticklebacks. Despite achieving velocities up to 20.2 times faster than the prey, juvenile fish do not employ low‐energy attacks. This contrasts with adults which adjust predatory behaviour according to prey‐type, but may be a result of the unpredictable prey escape response.
Virus‐associated spawning papillomatosis in smelt, Osmerus eperlanus L., in the River Thames
Authors: Lee S. , Whitfield P. J.
Published: January 2006

Smelt were collected from the R. Thames, at Lots Road Power Station, Fulham between October 1989 to June 1990. Smooth, white, ovoid tumours were observed on the fins of smelt during their anadromous spring migration and recognized as a form of spawning papillomatosis. Papillomatous fish constituted about 21% of the population in March and about 19% in April but were not present in any other samples. Up to 13 tumours were found on a single fish. Papilloma prevalence and intensity were both raised in larger fish. Ultrastructural examination revealed that a high proportion of tumour cells contained virus particles with herpesvirus group characteristics. Epithelial cells of fins without tumours revealed no such virus particles. Evidence of the herpesvirus as a likely aetiological agent of spawning papillomatosis is discussed.
Demand‐feeding behaviour and diel pattern of feeding activity in Oncorhynchus mykiss held under different photoperiod regimes
Authors: Boujard T. , Leatherland J. F.
Published: January 2006

Demand‐feeding behaviour was studied inOncorhynchus mykissheld at 7–10°C in groups of 30 individuals, under a 16:8, 12:12 or 8 : 16 light : dark regime, using self‐feeders connected to a computer. The daily food demand was variable between tanks from 1.5 to 5% of the body weight, the specific growth rate ranged between 1.4 and 2.6% of body weight increase per day, and the feed: gain ratio ranged between 0.84 and 3.17, regardless of the photoperiod length. More than 98% of the feeding demand occurred during the photophase, regardless of the photoperiod, with a main peak at dawn and an occasional peak at dusk.
The relative profitability of particulate‐ and filter‐feeding in the herring, Clupea harengus L.
Authors: Gibson R. N. , Ezzi I. A.
Published: January 2006

Analysis of laboratory video‐recordings of herring feeding by biting and filtering on Calanus finmarchicus and three sizes of Artemia enabled the capture rates of the two methods to be estimated at different prey concentrations. At low concentrations the fish feed by selective capture of individual particles, but the capture rate achievable by this method is constrained by the maximum rate at which they can bite. Filter‐feeding is not subject to this constraint because capture rate is directly proportional to prey concentration and above a critical prey concentration its capture rate exceeds that of biting. The possession of two feeding methods allows the fish to maximize prey intake over a wide range of concentrations and the phenomenon of switching between feeding methods can be explained by their relative profitabilities at different concentrations. The observation that less than 50% of fish are filtering when capture rates by the two methods are equal suggests that filtering is energetically more costly than biting. Estimates of the energy cost of filtering indicated that it may be from 1.4 to 4.6 times higher than that of biting.
Exceptionally big individual perch (Perca fluviatilis L.) and their growth
Authors: Le Cren E. D.
Published: January 2006

In Lake Windermere (U.K.) where there was a dense, slow‐growing population of perch (Perca fluviatilis L.) which had an lx of about 180 mm, there co‐existed a few individuals with an lx of 463 mm. Data from 137 of these big perch, mostly caught in gillnets fishing for Esox lucius L., were examined. Their early growth was identical to that of normal perch, but, at an age, varying between individuals, from 1 to 8 and averaging 4 years, their growth accelerated for about 4 years and then followed a von Bertalanffy model with an lx of 463 mm. They thus had a ‘double’ growth‐curve that is revealed only if individual growth is examined. Acceleration tended to occur in certain calendar years and was correlated with strong year‐classes of young perch. Growth was greater in years with warm summer water temperatures. There were no changes in the growth of big perch, after they had achieved 290 mm, during a period of great changes in the population density and an increase in the growth of normal perch < 290 mm. No more big perch were caught in Windermere between 1967 and 1990. Net selection, length‐weight relationships, seasonal cycle in gonad weight, and opercular‐body length relationship were the same as those of normal perch. The few available data suggest that big perch were piscivorous, feeding largely on small perch. The distribution of sites in the lake where big perch were caught is contagious, catches follow the negative binomial; but within fishings that caught big perch at the same site and time, catches were more evenly distributed than random. It is postulated that most adults would have accelerated their growth if they had sustained piscivory. Similar big perch have been found in other lakes.
Seasonal changes in some blood chemistry parameters and in relative liver and gonad weights of pike (Esox lucius L.) from the River Danube
Authors: Lenhardt M.
Published: January 2006

Samples from a natural population of pike (Esox lucius L.) from the River Danube were used in a 12‐month study to determine seasonal variations in biochemical parameters of pike blood sera, hepatosomatic index (HSI) and gonadosomatic index (GSI). The ranges of enzyme activities for sample means were: aspartate aminotransferase (ASAT) 252.0–583.8 U 1−1, alanine aminotransferase (ALAT) 4.9–11 ‐2 U1 and alkaline phosphatase (AP) 39.5–91.8 U1−1. The ranges of other parameters analysed in serum were total protein 27.7–40.1 g 1 1, urea 0.57–l.52 mmol 1 1 and creatinine 21.2–118.6 μmol 1 1. The range of sample means for HSI and GSI were 1.28–4.16 and 0.07–20.2 respectively. Temperature ranged from 4.5 to 23.5°C. The activity of serum AP was positively correlated to water temperature in males only, while urea and creatinine showed a positive correlation to water temperature in individuals of both sexes. GSI was correlated significantly with HSI in females. Total protein reached the lowest values during the spawning period, while creatinine levels depended on both the sex and season.
Electrophoretic identity between allis shad, Alosa alosa (L.), and twaite shad, A.fallax (Lacépède)
Authors: Boisneau P. , Mennesson‐Boisneau C. , Guyomard R.
Published: January 2006

Morphological characteristics as well as electrophoretic polymorphism have been analysed in eight samples of allis shad, Alosa alosa (L.) and twaite shad, Alosa fallax (Lacepede), collected in the Loire basin and the Gironde‐Dordogne system. The morphological characteristics showed that allis and twaite shad were present in these samples. Moreover, specimens with intermediate characteristics were found in the Loire and assumed to be hybrids between the two forms. By contrast, the two species were monomorphic and electrophoretically indistingishable at the 22 loci analysed. Therefore, it cannot be excluded that these two forms correspond to a single species.
Genetic variation in haemolytic activity in Atlantic salmon (Salmo salar L.)
Authors: Røed K. H. , Fjalestad K. , Larsen H. J. , Midthjel L.
Published: January 2006

Spontaneous and antibody‐dependent haemolytic activity against sheep red blood cells (SRBC) has been studied in serum from Atlantic salmon, Salmo salar L. Considerable increase in haemolytic activity was detected when SRBC were sensitized with haemolysin produced in Atlantic salmon. Haemolytic activity was sensitive both to divalent cations and to heat treatment. Significant reduction in haemolytic activity was detected after absorption with SRBC, indicating the presence of natural antibody against SRBC in Atlantic salmon serum. Persistent haemolytic activity of unsensitized SRBC in serum absorbed to remove natural antibodies was found, which suggests the activation of the alternative complement pathway, while the observed increased haemolytic activity in the presence of specific antibody against SRBC suggests activation of the classical complement pathway. Spontaneous and antibody‐dependent haemolytic activity were both analysed in absorbed and non‐absorbed sera in a family material of Atlantic salmon. The material consisted of 574 fish belonging to 57 fullsib groups within 20 paternal halfsib groups. Fish with signs of sexual maturity generally showed reduced haemolytic activity. Statistically significant effect of sire on the spontaneous haemolytic activity of both absorbed and nonabsorbed serum, and on antibody‐dependent activity, provides evidence of significant additive genetic variation in both the alternative and the classical complement activation in Atlantic salmon. Neither on a phenotypical nor on a family basis were the two traits statistically correlated. The estimated heritabilities were 0.2–0.3 with a standard error of approximately 0.1.
An improved method for studying the condition of fish, with an example using Pacific sardine Sardinops sagax (Jenyns)
Authors: Patterson K. R.
Published: January 2006

The statistical treatment of condition used in many previous studies has been to determine a predicted weight for a fish, and to calculate a ratio of actual to predicted weight. The ratios obtained, known as condition factor K, are then further analysed using analysis of variance or other techniques to relate changes in K to other independent variables. It is suggested that condition can be studied better by using a single model to analyse the response of fish weight to a number of factors simultaneously. This approach affords benefit from the simplicity of using an integrated analysis and avoids problems with skewed distributions of ratios. An example using data on the Pacific sardine, Sardinops sagax (Jenyns), is given. Changes in condition of this fish due to monthly, yearly and temperature effects are calculated.
Otolith microstructure and daily age of Anguilla japonica, Temminck & Schlegel elvers from the estuaries of Taiwan with reference to unit stock and larval migration
Authors: Tzeng W.‐N. , Tsai Y.‐C.
Published: January 2006

To test the hypothesis that the Japanese eel, Anguillu japonica, elvers in the eastern and western coasts of Taiwan are recruited from two different spawning grounds and to increase the knowledge of the early life history of the eel, the otolith microstructure and daily age of elvers collected from five estuaries in the coast of Taiwan during December 1989 through February 1990 were examined by scanning electron microscopy. The total length of elvers at arrival in the estuaries was similar among estuaries, averaging c. 56.0 mm and showed a seasonal decrease. The maximum radius of the sagittal otolith of elvers ranged from 124.46 to 181.82μm with a mean of 143.15 ± 12.72 μm. The otolith from centre to edge included an organic‐rich primordium (9.20 ± 2.02 μm in diameter), a diffusively calcified core (20.94 ± 1.99 μm), and the daily growth increments; these three layers were probably deposited during the embryonic, yolk sac and feeding period respectively. The growth rate of the otolith was higher at the beginning of early life (0.5−1.0 μm day −1), lowest at approximately 100‐days old (<0.5 μm day−1), and highest 1 month before arrival at the estuary (> 1.0 pm day−1). The mean age for elvers arriving in the estuaries of the coasts of Taiwan was approximately 170.4 ± 21.02 days. Neither the growth pattern of the otolith nor the age of elvers arriving in the estuary were significantly different among estuaries, indicating that the elvers in both eastern and western Taiwan were probably recruited from the same spawning ground. The growth pattern of the otolith in relation to larval migration was analysed.
Localization of chitinolytic enzymes in blood of turbot, Scophthalmus maximus, and their possible roles in defence
Authors: Manson F. D. C. , Fletcher T. C. , Gooday G. W.
Published: January 2006

The intracellular localizations ofchitinase and β‐N‐acetylglucosaminidase were detected in turbot blood smears, using a novel method employing fluorogenic substrates. The two enzymes showed different distributions, with chitinase being more generally distributed and N‐acetylglucosaminidase being strongly associated with distinct intracellular bodies, probably lysosomes. The fluorogenic substrates were used to analyse soluble and membrane fractions of homogenates of red and white blood cells prepared on Percoll gradients. In the leucocytes, the chitinase and N‐acetylglucosaminidase activities were mostly in the soluble fraction. In the erythrocytes the activities were lower, at about one‐hundredth and one‐tenth specific activities, respectively, and were distributed between soluble and membrane‐bound fractions at about 2 : 1 and 3 : 1, respectively. In contrast, lysozyme had a soluble distribution in leucocytes and was not detected in erythrocytes. Plasma was rich in chitinase and lysozyme activities but had no detectable N‐acetylglucosaminidase. Two possible roles for the chitinolytic enzymes are discussed: defence against pathogens and processing of glycoproteins or glucosaminoglycans. Evidence for a defence role for the chitinase and lysozyme is provided by demonstrating that they had inhibitory activity against the chitinous fungus Mucor mucedo.
Spawning behaviour and diel periodicity of egg production in captive Atlantic mackerel, Scomber scombrus L.*
Authors: Walsh M. , Johnstone A. D. F.
Published: January 2006

Spawning was observed in groups of captive Atlantic mackerel and occurred when a few fish swam away from the main school during a brief burst of high speed swimming. Counts of eggs from aquarium and field studies show that, in contrast to most pelagic fish species, spawning by Atlantic mackerel can occur at any time ofday or night and is not group‐synchronized. Implications of the observed die1 periodicity of egg production to stock size estimation by the Daily Egg Production Method are discussed.
An application of a bioenergetics model to Eurasian perch (Perca fluviatilis L.)
Authors: Karås P. , Thoresson G.
Published: January 2006

A bioenergetics model was developed for Eurasian perch (Perca fluviatilis L.) by revising an existing model for yellow perch and walleye. Data were gathered from field studies and the literature. Besides adjusting the original parameters of the model, effects of season on consumption and metabolic rates were added. The predictive capability of the revised model was high both concerning the levels of growth and its seasonal development in the Baltic coastal waters to which the model was applied. Perch young‐of‐the‐year attained almost maximum consumption and growth except in the highest temperatures experienced. In larger fish, the model estimated consumption to be about 50 per cent of the maximum possible rate.
A study of the population biology of Athevina boyeri Risso, 1810 in Aberthaw Lagoon, on the Bristol Channel, in South Wales
Authors: Creech S.
Published: January 2006

The biology of the sixth population of A. boyeri Risso, 1810 to be recorded outside of the Mediterranean basin is described. The 2 year life cycle was similar to that of other populations of the species that have been investigated. A maximum standard length of 93 mm was recorded for 2‐year‐old fish. Sexual maturity was attained by females at a length of 39 mm. A temporal lag in ovarian development was noted between the two spawning age groups, with the older age group spawning first. Details are provided of batch spawning in A. boyeriand the difficulties of assessing fecundity in batch spawners is discussed. Discrepancies between direct and indirect methods of assessing batch size indicated that the eggs around the largest mode may not represent the next batch to be spawned. Evidence is presented to suggest that in A. boyeri these eggs represent a ‘ store’ from which batches of eggs are subsequently released.
The routine metabolism of the guapote, Cichlasoma managuense (Günther 1869), related to body weight and temperature
Authors: Lezama E. , Günther J.
Published: January 2006

The routine metabolism of the guapote tigre, Cichlasoma managuense, was measured for a weight range between 6 mg and 800 g and at three different temperatures: 22, 27 and 32° C. Equations describing the routine metabolism of the guapote in relation to fish weight and temperature were calculated. The results are compared with those of other stenothermal tropical species.
Morphological and biometrical study of the gill rakers in four species of mullet
Authors: Guinea J. , Fernandez F.
Published: January 2006

The morphology and biometry of the gill rakers have been studied by scanning electron microscopy in juveniles and adults of four species of mullet (Liza aurata, Liza, saliens, Liza ramada and Chelon labrosus).

A detailed description of the structure and orientation of gill rakers and related structures is presented for the four species and the two sizes considered, showing broad similarities between them. However a biometrical study has shown significant differences between juveniles and adults of the same species as well as between juveniles or adults of different species and sizes. The possible relationship of such differences with the capacity for gathering food is discussed.
The periodicity of primary increment formation in the otoliths of Arctic charr Salvelinus alpinus (L.)
Authors: Adams C. E. , Murray K. R. , Huntingford F. A.
Published: January 2006

The role of environmental factors in the regulation of sub‐annual increment formation in fish otoliths appears to differ markedly between species. To examine the periodicity of primary increment formation in the otoliths of O + Arctic charr, Salvelinus alpinus (L.), and the effects of temperature, and photoperiod on their formation, fish were held under controlled environmental conditions. Primary growth increments were found in the otoliths of fish held at constant temperature (18° C) and at ambient temperature [fluctuating with a circadian and circannual rhythm (4–18° C)]. Consistent and significant disruptions in increment formation occurred however, in experimental groups subjected to rapid change from ambient photoperiod to a 6L: 6D photo‐period for 96 h. Disruptions in increment formation were also observed immediately following transportation of fish between holding facilities and following disease treatment. The number of otolith increments formed in fish held on an ambient photoperiod regime, correlated closely with time elapsed in days since checkmark formation (r= 0.989, P≤0.001) in fish sampled sequentially over a period of 10 to 105 days. Thus we demonstrate that under conditions of ambient photoperiod, primary increments are formed daily.
Further evidence for size‐assortative schooling in sticklebacks
Authors: Ranta E. , Juvonen S.‐K. , Peuhkuri N.
Published: January 2006

Using brook (Culaea inconstans) and 10‐spined (Pungitius pungitius) sticklebacks we examined body‐size related schooling behaviour. Small and large sticklebacks were allowed to choose between two test schools, of small and of large individuals, with and without a piscivorous fish (Oncorhynchus mykiss) visible. Sticklebacks of both species preferred the company of fish of matching body size: small fish associating with a school of small fish, large fish with a school of large fish. While no interspecific differences were found in responses to school selection, body size and predator presence did affect selection of school‐type. In both species, small fish tended to show a stronger preference for matching schools. The preference was enhanced in small fish with presence of a predator, but not in large fish. These observations are further evidence for assortative schooling in sticklebacks.
Genetic population structure of Norwegian brown trout
Authors: Skaala Ø.
Published: January 2006

Biochemical genetic variation in populations of anadromous and resident brown trout, Salmo trutta L., was studied. Altogether 50 Norwegian populations were screened for 32 enzyme loci. Genetic polymorphism was found at the following 11 loci: AAT‐4* (E.C. 2.6.1.1), CK‐1* (E.C. 2.7.3.2), G3PDH‐2* (E.C. 1.1.1.8), IDHP‐2* (E.C. 1.1.1.42), LDH‐5* (E.C. 1.1.1.27), MDH‐2* (E.C. 1.1.1.37), MDH‐3/4* (E.C. 1.1.1.37), MEP‐2* (E.C. 1.1.1.40), GPI‐2* (E.C. 5.3.1.9). GPI‐5* (E.C. 5.3.1.9) and PGM‐1* (E.C. 5.4.2.2), giving an overall polymorphism of 34%, ranging from 3.7 to 29.6% among individual populations. The average calculated heterozygosity ranged from 1.4 to 10.2% among populations. Genetic heterogeneity was observed among anadromous populations, and significant differences in allelic frequencies were found between anadromous populations in neighbouring watercourses, among resident populations and between anadromous and resident populations inhabiting the same watercourses. Significant heterogeneity was also found among 12 populations from Lake Mjøsa, with a major division between the western and eastern populations of the lake. Differences in allelic frequencies were found between wild stocks and their hatchery derivatives, and between different hatchery derivatives originating from the same wild population. In some cases release of hatchery populations into wild stocks may have influenced the genetic characteristics of wild stocks. The data support the hypothesis of eastern as well as western postglacial colonization lines for Norwegian brown trout.
β‐Adrenergic antagonists and carp (Cyprinus carpio L.) sperm motility
Authors: Nicotra A. , Senatori O.
Published: January 2006

We studied the effects of two β‐adrenergic antagonists, atenolol and propranolol, on carp sperm motility. Atenolol (10−3−10−8m) has no appreciable effects while propranolol (6 × 10−5−3 × 10−6m) affects the percentage of sperm motility in a dose‐dependent fashion.
The cellular composition of the blood and haematopoietic organs of turbot Scophthalmus maximus L.
Authors: Quentel C. , Obach A.
Published: January 2006

The cellular composition of the blood, anterior kidney, spleen and thymus of turbot Scophrhalmus maximus L., aged 1 + was determined. Ninety‐four per cent of blood cells belonged to the erythrocyte lineage of which 82% were mature erythrocytes. The leucocytes, which represented 4.5% of the blood cells, were mainly lymphocytes (50%). The presence of crythroblasts in the anterior kidney and the spleen demonstrated an erythropoietic activity in both organs. However, this activity appeared to be prevalent in the spleen which also appeared to act as a storage zone for erythrocytes and as the centre point for thrombopoiesis. Although 96% of the anterior kidney cells were leucocytes, the number of white cells per gram of organ was higher in the spleen.
Pattern of sea bass oocyte development after ovarian stimulation by LHRHa
Authors: Alvariño J. M. R. , Carrillo M. , Zanuy S. , Prat F. , Mañanos E.
Published: January 2006

The cyclic pattern of oocyte development in the sea bass, Dicentrarchus labrax L., was studied after induction of spawning by two injections, 24 h apart, of a luteinizing hormone releasing‐hormone analog (LHRHa) administered at the end of vitellogenesis. The first difference in the developmental stage of the ovary and in the size‐frequency distribution of oocytes between the LHRHa treated group and the control group, was detected 32 h after the first injection, the LHRHa group showing a higher proportion of the 900 μm diameter oocyte class (maturing oocytes) (P<0.01). At 48 h LHRHa‐treated females showed an increase in the 1000 and 1100 μm classes (maturing oocyte and ovulated eggs) (P<0.01) and at 72 h these females exhibited a bimodal pattern, reaching the highest proportions in the 1100 (27.4%) and the 600 (14.7%) μm classes (ovulated eggs and advanced vitellogenic oocytes, respectively). Bimodal distributions were present in 80% of the LHRHa‐treated females. Once oocyte final maturation was triggered by LHRHa the time needed for ovulation was about 48 h and the interval between consecutive ovulations and spawnings seemed to be 48–72 h.
Influence of size, winter duration and density on sexual maturation of Atlantic salmon (Salmo salar) juveniles in Little Codroy River (southwest Newfoundland)
Authors: Prévost E. , Chadwick E. M. P. , Claytor R. R.
Published: January 2006

Factors affecting sexual maturation of Atlantic salmon (Salmo salar L.) juveniles in fresh water were analysed under wild conditions in Little Codroy River (southwest Newfoundland). Large size after the first year of life and short winters favoured maturation of age 1 + male parr. Incidence of maturing 1+ males was greater where high densities of parr (>0.2 individuals m 2; fish >6cm fork length) were recorded in the second season of growth. These results were discussed according to current knowledge on early maturation in Atlantic salmon.
Evidence that size‐selective mortality affects growth of Atlantic cod (Gadus morhua L.) in the southern Gulf of St Lawrence
Authors: Hanson J. M. , Chouinard G. A.
Published: January 2006

The effects of size‐selective fishing mortality on the growth of Atlantic cod (Gadus morhuu L.) in the southern Gulf of St Lawrence were investigated and compared between: (1) a period when fishing mortality was relatively high, growth was relatively rapid, and abundance low (1967–1972 year classes): and (2) a period when fishing mortality was lower, growth was slow, and density high (1977–1982 year classes). Cod first entered the fishery at age 3 during both periods. The 1967–1972 year classes (fast growing) were fully recruited to the fishery by age 5 or 6 and the fishery removed over twice as many fish from the lower than upper quartiles of length‐at‐age distributions for cod 4 to 10 years old (disproportionately high exploitation of slow‐growing fish). In contrast. the 1977–1982 year classes (slow growing) did not fully recruit to the fishery until age 9 or 10 and the fishery removed four times as many fish from the upper than lower quartiles of the length‐at‐age distributions for 4‐ to 10‐year‐old cod (disproportionately high exploitation of fast‐growing fish). The reduced mean lengths‐at‐age of the 1977–1982 year classes compared with the 1967–I972 year‐classes is consistent with the different patterns of exploitation of fast‐ and slow‐growing fish for the two periods.
Cardiac pathology associated with the infection of Oncorhynchus mykiss Walbaum with Apatemon gracilis Rud. 1819
Authors: Watson J. J. , Pike A. W. , Priede I. G.
Published: January 2006

The chronological development of gross pathological and histopathological changes associated with the infection of rainbow trout, Oncorhynchus mykiss Walbaum, with metacercariae of Apatemon gracilis Rudolphi was investigated.
The evolution of sexual size dimorphism in fish*
Authors: Parker G. A.
Published: January 2006

Life history strategy models in which female size depends on fecundity and male size on male‐male competition, are used to predict male and female size. Sperm competition alone—without any form of contest competition—cannot readily generate size ratios (male weight/female weight) greater than 1·0, and if sperm competition is very weak, small or even dwarf males are predicted. Increasing sperm competition increases male size, but only with high numbers of competing males can male size approach that of females. Size dimorphism is also affected by the ratio: growth rate/mortality rate in each sex. If this is higher in one sex, its size increases. Two trade‐offs in fish could affect this ratio but neither appears likely to yield size ratios above unity under sperm competition.

Male‐male combat is capable of pushing male size beyond that of females, but male size seems never to exceed female size by more than one order of ten, whilst the reverse can proceed to many orders of ten (dwarf males), a pattern which applies generally in animals. Reasons for this asymmetry in size ratio include buffering effects of reducing growth rate (‘von Bertalanffy buffering’), and an asymmetry in the homeostatic effect of operational sex ratio (‘OSR buffering’). High adult male mortality and weak male‐male competition can generate dwarf males. A fundamental problem concerns why the sexes are often so similar in size: this may relate to sperm competition, size buffering effects, and many other features not considered in the present models.
Optimizing foraging behaviour through learning
Authors: Hughes R. N. , Kaiser M. J. , Mackney P. A. , Warburton K.
Published: January 2006

Manifestation of life‐history strategy is through the allocation of resources acquired by foraging. Foraging efficiency can be improved by learning, as fishes adjust their behaviour to changing circumstances. We briefly review the influence of learning on the foraging behaviour of fishes and make recommendations for further research. We stress the importance of quantifying learning and memory in relation to ontogeny and life history.
Early predictors of life‐history events: the link between first feeding date, dominance and seaward migration in Atlantic salmon, Salmo salar L.
Authors: Metcalfe N. B. , Thorpe J. E.
Published: January 2006

Previous studies have suggested that the earliest fry to emerge from a salmonid redd may have an advantage in the subsequent competition for feeding sites, partly through a ‘prior residence’ effect. Here we examined whether there was any relationship between the relative date of first feeding and subsequent dominance status and growth in a sibling group of Atlantic salmon, Salmo salar L., fry. Earlier‐feeding fry were dominant over their later‐feeding siblings (controlling for prior residence), despite not being any larger. However, these early fish soon established and then maintained a size advantage. This led to an increased probability of early‐feeding fish migrating to sea at age 1 year (rather than 2 or more). Thus a difference of less than 1 week in the relative timing of first feeding can translate into a year's difference in the timing of migration.
After‐care for Alcoholics—a Follow‐up Study
Authors: DUBOURG G. O.
Published: January 2006

Résumé (1) 76 alcooliques mâles, ont été tenu sous observation pendant 1‐2½ ans, aprés avoir quitté l'hôpital. L'évaluation de leur progrés état basée sur les habitudes de boire, la manniére de travailler et l'adapation sociale. (2) Aprés l'exclusion des psychopates de ces séries, les facteurs isolés, personels et sociaux, montrérent peu de relation avec le résultat, quoique une échelle de stabilité sociale générale retint sa valer pronostique. (3) Une bonne perspicacité et une motivation manquérent fréquemmet de prévenir une recute aprés la sorte de l'hôpital. (4) Deux tiers des patients qui se portéret birn aprésla sortie n'ont été incapables de bénéficier des soins ultérieurs actifs. (6) Ces résultats indiquent la nécéssité d'anutres recherches pour déterminer comment les soins ultérieurs pourraiet être donnés avec plous d'efficacité.
Contribution à l'Etude des Valeurs Existentielles Chez les Alcooliques
Authors: JURIJ ZALOKAR
Published: January 2006

Abstract 96 alcoholics in course of treatment wrote essays on the subjects of suffering, death and faith. We subsequently studied these essays by the method of analysis of the contents. The results confirmed the clinical impression that in alcoholics one can find no deeper vital philosophy. The ideas expressed by alcoholics reflect on the one hand the chiefly sensualist mentality and consuming of the present time and, on the other hand, a good dose of primitivism and incompleteness. For most of them suffering presents only an evil, whilst they avoid the thought of death as being something taboo. Concerning religion, they expressed faith only in varied immediate values. In none of the essays did we find any reflections on the deeper questions of man.
Beiträge zum Problem des symptomatischen Alkoholismus–I. Endogene Psychosen und “Alkoholismus”*
Authors: KARDOS G. , MÁRIA B.
Published: January 2006

Abstract We talk in Jellinek's sense about the disease of alcoholism, but we must regard the word “alcoholism” as a collective clinical conception in which we see: (1) “abnormal” habitual drinkers who drink too much and too often, but need not do so, for they are not dependent upon alcohol; (2) “real” alcoholics who also drink too much and too often because they cannot help it, i.e., because of their alcohol dependence they can be only alcoholics or abstainers; (3) symptomatic drinkers, in whom the everyday or periodic misuse of alcohol functions as a symptom or auto‐correction system of some fundamental psychiatric disorder. These “double” cases can occur together but can change the course of both diseases, sometimes favourably and sometimes unfavourably.

We have investigated this problem of symptomatic alcoholism over a period of many years, and have pointed out the importance of the reciprocal action between the abuse of alcohol and schizophrenia. In the case of our 29 schizophrenic drinkers we have observed and described several typical forms of these pathoplastic constellations. We also found, in the history of 100 non‐selected cyclothymics 19 cases of the symptomatic abuse of alcohol, which in the majority of cases led only to a non‐typical or even a typical–i.e., manic or melancholically amalgamate–intoxication, but in 8 cases led to a prolonged bout of habitual or relief drinking. Both these possibilities occurred very often in female cyclothymics.

In the pathogenesis of not a few cases the endogenic and endoreactive disturbances of the affectivity can, in addition to the well‐known sociological and psychological factors, play a causative or pathogenetic role. On the other hand, in the coincidence of schizophrenia and alcoholism, pathoplastic intermediate effects occur only from one case to another.