bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of food quality on maturation rate in Arctic charr, Salvelinus alpinus (L.)
Authors: Svedäng H.
Published: January 2006

The effects of food quality on maturation rate were followed in progeny from wild Arctic charr, caught in Lake Fattjaure, northern Sweden. The fish were reared at five different food quality levels. In the first summer, the fry were given feed of three qualities: diluted with cellulose in three proportions (0, 15 and 25%). During the second winter the impact of changed food quality level was studied by transferring half the fish from the high (control) to the low food quality level and vice versa.

Maturation rate was lower in males reared at the high and improved food quality levels than in males reared at the medium, low and reduced food quality levels. The maturation rate in females was similar at all levels, though the rate tended to increase at the reduced food quality level.

Fish reared at the high and medium levels had similar growth rates, whereas fish at the low food quality level experienced slower growth. Reduced food quality did not arrest the growth offish, whereas improved food quality enhanced their growth.
Age‐linked changes in salinity tolerance of larval spotted seatrout (Cynoscion nebulosus, Cuvier)
Authors: Banks M. A. , Holt G. J. , Wakeman J. M.
Published: January 2006

Acute salinity tolerance limits for the estuarine spawning spotted seatrout, Cynoscion nebulosus (Cuvier). were evaluated by examining 18 h survival of larvae in an extensive range of salinity treatments (0 to 56 ppt). Larvae from eggs spawned in two different salinities (24 and 32 ppt) as well as larvae acclimated in hypersaline and brackish waters were compared. Both upper and lower salinity tolerance limits showed an age‐linked pattern, decreasing to a minimum tolerance range (6.4 to 42.5 ppt) at age 3 days after hatching (at 28o C) and increasing to the widest range tolerated (1.9 to 49.8 ppt) on the last day tested (age 9 days). Acclimation to hyposaline conditions was demonstrated by larvae spawned at 32 ppt although significant hypersaline acclimation could not be demonstrated. Altered upper limits to the range tolerated by larvae from different spawning salinities indicated parental and/or early acclimation effects are important. Consistently greater vulnerability to both hyper‐ and hyposaline conditions at age 3 days after hatching was observed in all tests conducted. Exposures related to the onset of feeding at this time are likely explanations for this reduced tolerance.
Maturation in chinook salmon, Oncorhynchus tshawytscha (Walbaum): early identification based on the development of a bimodal weight‐frequency distribution
Authors: Heath D. D. , Heath J. W. , Iwama G. K.
Published: January 2006

Male chinook salmon, orhynchus tshawytscha (Walbaum), are known to mature sexually after one summer in sea water, one year earlier than any of the females. Two year classes of first generation domestic chinook salmon stock reared to sexual maturity on a commercial salmon farm in British Columbia, Canada were sampled for wet weight at various times during the spring after their first winter in the sea. Frequency distributions of wet weight were developed for both year classes. The weight‐frequency distributions for both cohorts became statistically bimodal in May of their first year in the sea. The fish from the two modal groups for both cohorts were sorted and kept separate over the summer. The difference in the mean weight for the two groups increased throughout the summer in both years. The higher weight group in each cohort proved to be >95% early maturing males, and represented 64–46% of all the early maturing males evident in the September following the sort. The potential use of this information for commercial salmon growers and fisheries scientists interested in sexual maturation of the chinook salmon is discussed.
Glycosaminoglycan composition of tarpon (Megalops atlanticus) and ladyfish (Elops saurus) leptocephali
Authors: Pfeiler E. , Donnelly J. , Tores J. J. , Crabtrees R. E.
Published: January 2006

Heparan sulphate was found to be the principal glycosaminoglycan (GAG) in tarpon leptocephali, with keratan sulphate also present. The main GAG in ladyfish leptocephali appeared to be a form of chondroitin sulphate (possibly undersulphated).
Biology of Galaxiella munda McDowall (Teleostei: Galaxüdae), including a comparison of the reproductive strategies of this and three other local species
Authors: Pen L. J. , Potter I. C. , Hilliard R. W.
Published: January 2006

The reproductive biology, growth and diet of Galaxiella munda McDowall in a south‐western Australian river are described. Monthly trends in gonadosomatic indices, stages in ovarian development and the size and maturity of oocytes show that spawning extended from July to October and peaked in late August to early September. Histology of ovaries indicated that G. munda produced clutches of eggs which it released at intervals. Data on length‐frequencies, otoliths and gonads demonstrate that G. munda typically died in the few months after spawning. By age I, the females and males of G. munda had reached 47 mm (≡ 0.54 g) and 43 mm (≡ 0.42 g), respectively. The respective von Bertalanffy growth curve parameters for L., K and to were 48.6 mm, 3.702 and ‐0.0014 for females and 44.3 mm, 4.217 and ‐0.0012 for males. Galaxiella munda fed predominantly on terrestrial fauna on the water surface, cladocerans and copepods in the water column, and dipteran larvae in the benthos. Comparisons are made between the above aspects of the biology of G. munda and those recorded for three other locally endemic species (Galaxias occidentalis Ogilby, Bostockia porosa Castelnau and Edelia vittata Castelnau) and wherever possible with other Galaxiella species. Such comparisons have emphasized the relationship between size and age at first maturity and spawning mode.
Seasonal changes in serum steroid hormones in a protandrous teleost, the sobaity (Sparidentex hasta Valenciennes)
Authors: Kime D. E. , Lone K. P. , Al‐Marzouk A.
Published: January 2006

Serum concentrations of 11‐ketotestosterone, 11β‐hydroxytestosterone, testosterone, testoster‐one glucuronide, oestradiol and 17,20β ‐dihydroxy‐4‐pregnen‐3‐one (17,20β ‐P) were measured in the sobaity at monthly intervals through their second breeding season. Concentrations of the 11‐oxygenated androgens in the males and of oestradiol in the females peaked during the spawning season in January‐February, while maximum levels of testosterone were found in the summer when these steroids were low. Testosterone glucuronide showed two peaks, one in the post‐spawning period as oestradiol and the 11‐oxygenated androgens were falling and the other coincident with the summer peak of testosterone. 17,20β ‐P was detectable in only one male and one female fish in February. Serum concentrations of 11‐oxygenated androgens are more reliable than those of oestradiol for determining the sex of sobaity, and may also be used as indicators of the occurrence of sex reversal. The seasonal pattern of serum steroids correlated well with the changes of sexual status of the gonads during regression and recrudescence observed histologically and suggests that oestradiol may be involved in the sex inversion of this species.
Smolting characters in anadromous and resident Arctic charr, Salvelinus alpinus (L.)
Authors: Damsgård B.
Published: January 2006

Morphological differences, haematocrit value and chloride cells were examined in downstream migrating Arctic charr, Salvelinus alpinus (L.) from the Hals River, North Norway, and resident charr from Lake Storvann. Fish were classified as visual parr, silvery parr or smolt based on the degree of silvering and the Occurrence of lateral parr marks. On average, 47% of downstream migrating Arctic charr were classified as visual molts, but only 14% of the resident charr. Charr longer than 20 cm fork length were mainly classified as visual molts. Morphometrical analyses of body size and shape revealed that most of the variations could be explained in terms of variations in fork length. Length adjusted ratios of post‐anal distances were significantly higher in migrating charr than in resident charr. The number of developed chloride cells, the cell nucleus diameter in the basin of secondary gill lamellae and blood haematocrit values were significantly higher among downstream migrating charr than in resident charr. However, morphological differences between anadromous and resident Arctic charr were not necessarily synchronized with the development of chloride cells.
The morphology of the club glands on the dorsal fin of mature male shannies, Lipophvys pholis (L.) (Blenniidae: Teleostei)
Authors: Northcott S. J. , Bullock A. M.
Published: January 2006

The pelvic, pectoral, anal and dorsal fins of mature male, female and immature male Lipophrys pholis (L.) were examined by light microscopy for the presence of club glands. All fins except the dorsal showed a highly stratified epidermis and a thick cuticle. Club glands were present on the dorsal fin of mature male fisH but only during the breeding season. The development and decline of the club glands corresponds to the period of gonadal build‐up and spawnout. Each club gland comprises several thousand bundles ofcolumnar cells. The columnar cells surround acentral pore which opens to the outside through a layer of Malpighian cells. The substance produced by the gland includes mucopolysacchdride. The function of the secretion is unknown and is discussed in relation to studies on similar glands in several Mediterranean blenniids.
Age and growth of three species of tuna baitfish (genus: Spratelloides) in the tropical Indo‐Pacific
Authors: Milton D. A. , Blaber S. J. M. , Rawlinson N. J. F.
Published: January 2006

Sprafelloides grarilis (Temminck & Schlegel), S. delirarulus (Bennett) and S. lewisi (Wongratana) live generally less than 4 months. They lived more than 5 months at only three of 10 sites sampled. Growth varied seasonally in S. grocilis(Temminck & Schlegel) at two sites in the Solomon Islands and in S. clelicululus (Bennett) at Helix Reef, near Townsville, Australia. This variation in the growth rate of S. grucilis could not be related to specific environmental patterns, but that of S. delicurulus at Townsville might be temperature‐related. Instantaneous growth rates for all species were 0.4‐1.7 mm day ‐1 at an age of I month and the range of variation in growth rate was similar for all species. These rates declined to 0.1 mm day ‐1 at 3 months of age, which is the rate reported for other short‐lived clupeoids at the same age. The growth rates of fish from coral atoll and coastal lagoons were similar but barrier reef fish grew significantly faster. These results indicate that Sprarelloides have an extremely flexible growth pattern and that biological variation within a site can be as great as variation between sites.
Examination of reproductive success of transplanted stocks in an amphidromous fish, Plecoglossus altivelis (Temmink et Schlegel) using mitochondrial DNA and isozyme markers.
Authors: Pastene L. A. , Numachi K. , Tsukamoto K.
Published: January 2006

Isozymes and mitochondrial DNA (mtDNA) were used as genetic markers to evaluate the reproductive success of transplanted stocks of ayu Plecoglossus ultivelis in a highly stocked Japanese river, the Shinano. Two major alleles at the MPP and GPI‐A* loci and 26 mtDNA clonal genotypes were demonstrated and surveyed in two non‐native source populations and five collections from the Shinano River. Contributing populations were clearly discriminated in their isozymes and mtDNA composition. Despite the stocking of large numbers of non‐native fish, they have had little effect on the genetic characteristics of the native population. Maturation and migration of the stocking and native populations was traced by genetic markers to clear the mechanism of this event. All the contributing populations join together in the migration toward the spawning ground throughout the spawning season but these contributing populations occur independently of each other in other sites of the river.
A direct approach to the measurement of genetic variation in fish populations: applications of the polymerase chain reaction to studies of Atlantic cod, Gadus morhua L.
Authors: Carr S. M. , Marshall H. D.
Published: January 2006

We used the polymerase chain reaction (PCR) and direct DNA sequencing to study genetic variation within and among populations of Atlantic cod, Gadus morhua, in the western North Atlantic. In a 307 bp region of the mitochondrial cytochrome b gene, 24 variable nucleotide positions define 24 genotypes, which differ by from one to six nucleotide substitutions. Greenland cod (G. ogac) differs from the most similar G. morhua genotype by an additional 12 nucleotide substitutions. Silent transitions dominate both intra‐ and interspecific comparisons, however four nucleotide substitutions within morhua result in amino acid replacements. Direct sequencing of DNA reveals substantially more of the genetic variation that exists within and between species than do previous indirect methods based on restriction fragment length polymorphisms, and thus has far greater potential to quantify such differences as may exist among fish stocks. Preliminary experiments also indicate that automation of DNA sequencing provides an efficient, rapid, and accurate means for detection of genetic variation in natural populations offish.
An immunochemical analysis of the novel liver‐restricted LDH activity from cichlid fishes (Cichlidae: Teleostei) confirms its non‐orthology with piscine LDH‐C
Authors: Leibel W. S. , Bass K. N. , Eshbach J. E.
Published: January 2006

In an electrophoretic survey of lactate dehydrogenase (LDH) isozymes in neotropical cichlid fishes (Perciformes: Cichlidae) several species were discovered in which a cathodal liver‐restricted isozyme is expressed along with the highly anodal eye‐restricted isozyme (LDH‐C4) typically encountered in perciform fishes. Biochemical characterization of these two isozymes from the basketmouth cichlid, Acaronia nassa (Heckel), strongly suggested that they were non‐orthologous and challenged the accepted view that eye‐ and liver‐restricted LDH isozymes are alternative expressions of the same (LDH‐C *) gene. In this study, antiserum raised against cypriniform (goldfish) liver‐restricted LDH‐C4 failed to cross‐react with the basketmouth liver‐restricted analogue while effectively titrating the eye‐restricted, anodal isozyme and, at higher titres, the LDH‐B4, heart‐restricted isozyme from all cichlid species. Anti‐serum raised against basketmouth muscle‐restricted LDH‐A4 failed to titrate any of the eye‐ and liver‐restricted isozymes. These data confirm the orthology of eye‐ and liver‐restricted LDH isozymes in Cypriniform and Perciform fishes as originally proposed, suggest that the liver‐restricted isozyme of cichlid fishes is non‐orthologous and further raise the question of identity and evolutionary origin of this anomalous LDH activity.
Spawning patterns in the three‐spined stickleback (Gasterosteus aculeatus L.): an evaluation by DNA fingerprinting
Authors: Rico C. , Kuhnlein U. , FitzGerald G. J.
Published: January 2006

We analysed a random sample of 10 three‐spined stickleback nests by DNA fingerprinting. DNA from the guardian male and a random subsample of LO fry per nest were probed with pYNZ 132, a human single‐locus probe for VNTR‐loci (variable number of tandem repeats). On average this probe produced DNA fingerprints of 12 scoreable bands. By comparing the bands present in each individual, we calculated band sharing indices (BSIs) between the guardian male and its fry. The BSls varied between 0.40 and 0.77 with an average (± S.D.) of 0.59 ± 0.09. We therefore conclude that the guardian male was the true father of the fry in all these nests. Once the paternal bands in each fry were determined, we compared the maternal bands among the fry of each nest. Based on the BSIs obtained with these comparisons, we found that one guardian male enticed three females to spawn in its nest, six enticed two females and three enticed one female.
Development and use of striped bass‐specific RFLP probes
Authors: Wirgin I. I. , Maceda L.
Published: January 2006

We sought to develop nuclear DNA (nDNA) probes which could be used to complement mtDNA and DNA fingerprinting markers in distinguishing striped bass, Morone saxatilis (Walbaum), from discrete spawning systems. Restriction endonuclease‐generated single copy, 10–20‐kb striped bass nuclear nDNA fragments were cloned into the bacteriophage vector Lambda Dash II and tested in Southern blot analyses for their abilities to reveal population‐specific polymorphisms. Three of the I7 nDNA sequences tested exhibited polymorphisms which potentially could be used to delineate striped bass populations. One probe, DSB 22, revealed significant genotypic frequency differences between Gulf of Mexico and Atlantic striped bass and among striped bass representative of some Atlantic systems. These preliminary results suggest that single copy nDNA sequences may provide sufficient polymorphisms to aid in stock identification of species which proved genetically monomorphic using other approaches.
Conservation genetics considerations in fishery management
Authors: Ryman N.
Published: January 2006

This paper discusses three aspects of genetic conservation relating to fishery management and fish culture, namely (1) the goal for conservation (what to conserve), (2) a guideline for assessing acceptable levels of gene flow among populations. and (3) the effect on the genetically effective population size resulting from stock enhancement. Goal for conservation: The goal for genetic conservation is to maintain genetic variability between and within populations. It has been suggested recently, as an alternative to that goal, that in the context of fisheries management conservation should strive at maintaining the variance or the distribution of fitness. The characteristics of this model are discussed from the perspective of population genetics. It is concluded that although the fitness approach may appear attractive it is not compatible with the more general objective of maintaining genetic diversity between and within populations. Acceptable levels of gene, flow: A tension exists between the need for protection of natural fish populations and the rapidly expanding levels of aquaculture causing increased migration into those populations. Guidelines are needed for assessing levels of introgression that are acceptable in the context of genetic conservation. To avoid unrealistically restrictive recommendations it is suggested that acceptable levels of introgression are related to those occurring naturally. It is argued that assessments of acceptable levels of introgression should be made on the basis of spontaneously occurring gene flow estimated from genetic data using parameters such as Fst or similar ones. Stock enhancement and effective size: In the context of genetic conservation previously published recommendations on stocking have focussed on the need to identify the genetic structure within the region in question to ensure that the appropriate population is targeted for propagation and release. There is, however, an additional aspect that appears to have been largely unrecognized: the reduction of the genetically effective size of the total population that may result from breeding‐release programmes aimed at supporting wild stocks. The details of this problem are introduced and discussed.
Strengths and limitations of molecular sequence comparisons for inferring the phylogeny of the major groups of fishes
Authors: Stock D. W. , Gibbons J. K. , Whitt G. S.
Published: January 2006

Although the phylogenetic relationships of the major groups of fishes have been extensively studied with morphological characters, not all have been convincingly resolved. Analyses of molecular sequences from these groups may provide additional insights into problematical relationships, but are only just beginning to appear. We compare our own results from analyses of 18s ribosomal RNA sequences with those of other studies using globins, parvalbumins, insulin, 28s ribosomal RNA, and portions of two mitochondria1 genes (12S ribosomal RNA and cytochrome b). Our evaluation of these studies reveals some of the difficulties encountered in reconstructing ancient divergences within the fishes, including unequal rates of evolution (among regions of a molecule as well as among lineages), gene duplication, extinction of lineages, and a possible rapid radiation of gnathostome higher taxa. The importance of evaluating the robustness of particular phylogenetic hypotheses is stressed. Some molecules appear to be inappropriate for investigating higher level divergences within the fishes; others are more promising, but must be examined in more taxa to allow an adequate evaluation of their utility. Convincing support for particular hypotheses of relationship will ultimately require congruence of trees generated from independent molecular data sets.
Molecular systematics of three tilapüne genera Tilapia, Sarotherodon and Oreochromis using allozyme data
Authors: Sodsuk P. , McAndrew B. J.
Published: January 2006

Allozyme data from 44 different loci were collected for 15 species from three genera in the tribe Tilapüni. Dendrograms constructed by using both genetic distance and binary coded presence or absence of alleles show that the substrate spawning Tilupiu are consistently separated from the two mouthbrooding genera Surorherodon and Oreochromis. The implications of these findings for the taxonomy of the group and minor rearrangement within the Oreochromis are discussed.
Introgressive hybridization in fishes: the biochemical evidence
Authors: Verspoor E. , Hammart J.
Published: January 2006

Biochemical methods can detect variation at individual genetic loci, making possible the direct assessment of natural hybridization and introgression between fish populations. Protein electro‐phoresis has been used to confirm and extend knowledge of many situations where species hybrids have been detected by morphological analyses. New cases of natural hybridization, including some at the subspecies level, have also been identified. Biochemical studies have provided the first conclusive evidence of natural post F1 hybrids and of introgression between fish taxa. The strongest cases for introgression have used a combined analysis of nuclear protein genes and taxaspecific maternally inherited mitochondrial DNA variation. Information on the significance of introgression as a source of gene flow between taxa, particularly below the species level where sympatric subspecies and sibling species are involved, should expand in the future as the numbers and types of nuclear and mitochondrial DNA loci which can be assayed for variation increase. The full importance of introgressive hybridization in speciation may then be understood.
An intensive study of allozyme variation in freshwater resident and anadromous trout, Salmo trutta L., in western Ireland*
Authors: Cross T. F. , Mills C. P. R. , de Courcy Williams M.
Published: January 2006

Ten polymorphic enzyme coding loci were assayed using starch gel electrophoresis in anadromous (sea trout) and freshwater‐resident trout, Salmo trutta, from two neighbouring river systems draining into Clew Bay in western Ireland. Samples were collected from the Burrishoole and from the neighbouring Newport river system. In the Burrishoole system, two samples were from above waterfalls impassable to migratory trout, two consisted of anadromous smolts or post‐smolts and the remainder were freshwater‐resident trout from freely accessible areas. There were large differences in gene frequency between trout from above impassable barriers and all others sampled, and these two groups also differed substantially from each other. More minor differences were evident between some other samples, particularly between trout from the upper lake and streams entering it and a stream associated with the lower lake. Two anadromous populations therefore occur in the Burrishoole system. In contrast, no differences were evident in two sampling years between anadromous trout and cohabiting freshwater‐resident trout from the upper part of the Burrishoole system. Thus, in the upper part of this system, anadromous trout do not appear to comprise a separate population from non‐migratory trout and interbreeding may occur.
A karyological analysis of the artificial hybridization between Clarias gariepinus (Burchell, 1822) and Heterobranchus longifilis Valenciennes, 1840 (Pisces; Clariidae)
Authors: Teugels G. G. , Ozouf‐costz C. , Legendre M. , Parrent M.
Published: January 2006

A karyological analysis of an artificial hybridization (reciprocal crosses) between two African clariid catfish, Clarias gariepinus (Burchell, 1822) and Heterobranchus longifilis Valenciennes, 1840, was performed. C. gariepinus has a standard karyotype of 2n= 56, while H. longifilis has 2n= 52. The hybrids revealed an intermediate karyotype (2n= 54), and it appears as if they have totalized the haploid chromosome number of both parental species, excluding gynogenesis or androgenesis. The hybrid karyotype is considered as aneuploid, although the hybrids proved to be fertile. No variation was found in the hybrids karyotypes.
Enzymatic variation in African clariid catfishes
Authors: Teugels G. G. , Guyomard R. , Legendre M.
Published: January 2006

Enzymatic polymorphism was examined at 13 protein loci in four African clariid catfish species: Clarias anguillaris (Linnaeus, 1758), C. ebriensis Pellegrin, 1920, C. gariepinus (Burchell, 1822) and Heterobranchus longifilis Valenciennes, 1840. The latter appears to be closer to C. anguillaris and C. gariepinus than C. ebriensis. These results correspond with recently published karyological and morphometrical data.

Reproductive compatibility, under laboratory conditions at least, is demonstrated between C. gariepinus and H. longifilis. The hybrids were shown to be completely intermediate between the parental strains.
Feeding ecology of the Iberian cyprinid Barbus bocagei Steindachner, 1865 in a lowland river
Authors: Magalhãtes M. F.
Published: January 2006

Patterns of food resource utilization by Barbus bocagei in a lowland river in the central part of the Iberian Peninsula are presented and discussed. Focal points include feeding activity, diet composition and seasonal and ontogenetic diet shifts. Striking features of overall feeding pattern of barbel are its continuous feeding activity, bottom habits, high consumption of detritus and dipteran larvae and narrow diet breadth. Seasonal changes in food resource availability elicited changes in food utilization patterns, revealing a trend to more generalist feeding during spring. Barbel increase consumption of plant material and large prey during ontogeny, but overlap in prey resource utilization between size classes is high. The versatility of barbel foraging behaviour may be an important feature in its exploitation of Iberian lotic systems.
Rhabdosargus haffara(Forsskål, 1775) andSphyraena flavicaudaRüppell, 1833—new Red Sea immigrants in the Mediterranean
Authors: Golani D.
Published: January 2006

Two Red Sea species, the sparidRhabdosargus haffaraand the sphyraenidSphyraena flavicauda, previously unrecorded in the Mediterranean, have been recently found in the vicinity of Tel‐Aviv, coast of Israel.
The crystalline ultrastructure of otoliths of the eel (A. anguilla L. 1758)
Authors: Lecomte‐Finiger R.
Published: January 2006

The ultrastructure of the organic and the mineral components of eel (Anguilla anguilla L. 1758) otoliths was studied using sections through the nucleus and observed by scanning electron microscopy. The otoliths were composed of crystalline material (aragonite) running radially from the centre to the edge. Structural discontinuities were described: seasonal rings, checks and daily growth increments.
Acoustic measurement of trout distributions in Spada Lake, Washington, using stationary transducers
Authors: Stables T. B. , Thomas G. L.
Published: January 2006

Diel patterns in the spatial distribution of rainbow and cutthroat trout were studied with stationary acoustic transducers, gillnets, and setlines in Spada Lake during summer thermal stratification. Four diel periods (dawn, 03.00–07.00 hours; day, 07.00–19.00 hours; dusk, 19.00–23.00 hours; night, 23.00–03.00 hours) and two horizontal strata (nearshore, bottom depth < 8 m; offshore, bottom depth > 8 m) were identified from fish distribution patterns. During the day, trout were almost exclusively offshore and their densities were highest at intermediate depths of the water column (4–16 m). From dusk to dawn, trout were in intermediate and shallow depths (0–4 m) of the offshore and nearshore strata. The mean depth of capture was significantly deeper for cutthroat trout (9 m) than for rainbow trout (3m). Both species primarily inhabited the epilimnion and metalimnion where temperature ranged from 22.5 to 11.0°C and were nearly absent from deeper, cooler waters. Dissolved oxygen levels ranging from 3.9 to 8.6 mg/l did not seem to influence trout distributions.
Territoriality and microhabitat selection in two intertidal New Zealand fish
Authors: Mayr M. , Berger A.
Published: January 2006

Aspects of territoriality and microhabitat selection in Acanthoclinus fuscus and Forsterygion nigripenne robustum were studied in intra‐ and interspecific confrontation experiments under tidal and constant conditions. In both species aggressive responses were closely related to activity with maximal frequencies during the first 2 h of the experiments. Under tidal conditions activity was higher than at constant water level. Size predominantly affected contest outcome in both species. Initiation of the first bout and past experience were further important factors, whereas prior residence did not influence dominance relationships. Dominant individuals defended access to shelter and low tide pools as critical resources. A. fuscus preferred tubes matching the body size for cover, whereas F. n. robustum spent more time in caves and on open areas. Furthermore, A. fuscus preferred shallower water and was able to sustain long periods out of water. The different microhabitat preferences may reduce interspecific competition. Although A. fuscus did not win significantly more trials, higher aggressive tendencies were observed in this species.
Effects of sexual maturation, castration, and androgen implants on growth in one‐ and two‐year‐old parr in a Baltic Atlantic salmon (Salmo salar L.) stock
Authors: Berglund I. , Mayer I. , Borg B.
Published: January 2006

The effects of maturation, castration, and androgen implants on growth in 1‐ and 2‐year‐old Baltic salmon (Salmo salar L.) were studied in a stock originating from the Umeälven (Ume river) in northern Sweden. 1 + male parr that later matured were larger than non‐maturing parr in the spring. Later in the summer, during the period of gonadal growth, the growth rate of maturing parr was depressed compared to that of non‐maturing males. Implantation of capsules with 11‐ketoandrostenedione (OA) or testosterone (T) in sexually immature 1‐year‐old fish, accelerated the specific growth rate in spring and early summer, particularly considering growth in weight, resulting in an increase in the condition factor. In contrast, the growth rate was depressed from late June onwards, the period when the gonads normally develop in 1 + parr. T, but not OA, also promoted sexual maturation. Castration or OA treatment did not affect total summer growth in 2‐year‐old salmon. This study suggests a causal relationship between androgens and the growth pattern observed in maturing 1 + male parr.
Otolith microstructure pattern in Oreochromis niloticus (L.)
Authors: Zhang Z. , Runham N. W.
Published: January 2006

The microstructure of otoliths from young and old Oreochromis niloticus (L.) were studied. Otoliths were prepared histologically except for those from newly hatched fish. Hatching results in the formation of a check in the otoliths, which appeared 1 day later. Other checks are rare in juvenile otoliths but common in adult otoliths. Faint and non‐daily increments were observed within the hatching check. After hatching, increments were deposited daily. Sub‐daily increments were faint and narrow, they were present in the area along the dorso‐ventral axis of the otolith but did not continue into the lateral region. Discontinuous zones in the medial area appeared different from those in the lateral area. New growth centres were not only found in the juvenile fish otoliths, but also in adult fish otoliths.
Effects of food ration and temperature level on the growth of Oreochromis niloticus (L.) and their otoliths
Authors: Zhang Z. , Runham N. W.
Published: January 2006

Sub‐optimal conditions in terms of maintenance ration and/or low temperature resulted in otolith bands, with distinct microstructural features, in response to each particular condition. Check(s) were not only produced corresponding to the transition from optimal to the sub‐optimal conditions but also from sub‐optimal to the optimal ones. Daily increment deposition, although faint and narrow, persisted in the otoliths of fish when they were kept at low temperatures and fed on maximum food rations. Observable increments were produced only in the first few days of the period when fish were fed on maintenance rations at the optimal temperature. There were only a few checks formed in the otoliths of fish under the conditions of low temperature and maintenance rations. Restraining fish growth in each of the above sub‐optimal conditions boosted the growth of the fish and their otoliths when optimal conditions resumed.
Lunar synchronization of spawning in sea bass, Lates calcarifer (Bloch): effect of luteinizing hormone‐releasing hormone analogue (LHRHa) treatment
Authors: Garcia L. Ma. B.
Published: January 2006

Based on egg collection records, spontaneous spawning activity of sea bass, Lates calcarifer (Bloch), reared in floating net cages followed a semilunar cycle. The peak of multiple spawnings coincided with declining spring tides of quarter moon periods. Maximum diameter of intra‐ovarian, ripe oocytes (0.51–0.55 mm) occurred in synchrony with the quarter moon periods. Smaller oocytes (0.44–0.47 mm) were sampled during the new and full moon periods. Two structural analogues of luteinizing hormone‐releasing hormone (LHRHa) (des‐Gly10, d‐Ala6‐LHRH ethylamide and d‐Ala6, Pro9‐Nethylamide‐LHRH), in pelleted or dissolved form, induced mature female sea bass with a mean egg diameter of at least 0.40 mm to spawn at any day during the lunar cycle. The onset of spontaneous and LHRHa‐induced spawnings occurred during low tides in the evening until dawn (from 19.00 to 05.00 hours). These results demonstrate that LHRHa can effectively induce mature sea bass to spawn independent of the highly predictable semilunar spawning rhythm. In addition, the occurrence of both spontaneous and hormone‐induced spawnings at a precise period of the day suggest a tidal and diurnal cue entraining spawning of mature female sea bass.
Extensive chromosomal rearrangements and nuclear DNA content changes in the evolution of the armoured catfishes genus Corydoras (Pisces, Siluriformes, Callichthyidae)
Authors: Oliveira C. , Almeida‐Toledo L. F. , Mori L. , Toledo‐Filho S. A.
Published: January 2006

Karyotypes and nuclear DNA content were studied in 11 species of the genus Corydoras from rivers in South America: C. sp. from Caripi river 2n=60, C. cf. simulatus 2n=62, C. simulatus 2n=62, C. reticulatus 2n=74, C. sp. from Galheiro river 2n=84, C. aff. punctatus from Negro river 2n=102, C. flaveolus 2n=58, C. arcuatus 2n=46, C. trilineatus 2n=46, C. schwartzi 2n=46, and C. metae 2n=92. Extensive chromosome diversity and differences in DNA content were detected among species. The high variability in chromosome counts was not exclusively related to chromosomal structural rearrangements, but also to large changes in DNA content. Species could be grouped using their shared cytogenetic characteristics, suggesting that within the genus Corydoras different groups of species followed distinct evolutionary trends. Chromosomal rearrangements in Corydoras are, apparently, more frequent that morphological modifications, so cytogenetic data may be very useful for species delimitation and for the understanding of interrelationships among species.
Occurrence of Phyllodistomum folium (Olfers) (Digenea) in the eel, Anguilla anguilla (Linnaeus), in a small river
Authors: Nie P. , Kennedy C. R.
Published: January 2006

The occurrence of Phyllodistomum folium in a population of eels was studied throughout one year. Abundance exhibited a summer peak. Gravid adults were found in all months, indicating that eels can serve as a definitive host for this parasite.
Orally induced spawning of Thai carp (Puntius gonionotus, Bleeker) following co‐administration of des Gly10 (D‐Arg6) sGnRH ethylamide and domperidone
Authors: Sukumasavin N. , Leelapatra W. , McLean E. , Donaldson E. M.
Published: January 2006

Oral delivery of a salmon gonadotropin releasing hormone analogue (50–100 μg kg−1 B.W.) and domperidone (25–50 mg kg−1 B.W.) to Thai carp, induced ovulation in 83–100% of treated animals within 48 h of administration.
The ultrastructure of myotomal muscles of the golomianka, Cormephorus baikalensis Pallas
Authors: Kilarski W. M. , Kozlowska M. , Martynova M. G.
Published: January 2006

An ultrastructural study of the myotomal muscles in the golomianka, Comephorus baikalensis Pallas, revealed two main and distinct muscle regions: superficial and white. They were distinguished on the basis of histological and ultrastructural organization. Only the superficial fibre region shows homogeneous organization. The principal new finding is the unique ultrastructural organization of the superficial muscle fibres. Their myofibrils occur in the form of ribbons surrounded by large mitochondria.
Influence of size and level of satiation on prey handling time in Channa striata (Bloch)
Authors: Bindoo M. , Aravindan C. M.
Published: January 2006

Channa striata fry (100 ± 20 mg) and fingerlings (2 ± 0.2 g) were offered mosquito larvae as prey and the adults (75 ± 5 g) small fishes. The size of the fish was directly related to satiation time and inversely related to satiation amount. The influence of satiation levels on handling time, showed an increase to almost eight‐fold in fry and fingerlings and about two‐fold in adults. The study also revealed the role played by the young of C. striata in mosquito control. With the increase in size of the fish the preference for mosquito larvae was seen to decrease. The air breathing habit and hence its ability to survive in polluted and oxygen‐depleted waters makes it a suitable candidate as a fish for mosquito control.
Cyclic growth and activity of pancreatic enzymes in alevins of Arctic charr (Salvelinus alpinus L.)
Authors: Dabrowski K. , Krumschnabel G. , Paukku M. , Labanowski J.
Published: January 2006

Growth and digestive enzymes were studied in alevins of Arctic charr raised on six commercial diets that differed in protein source and level. There were links between diet composition (protein quality), fish performance and proteolytic and amylase enzyme activities. Trypsin and amylase activities were up to 10‐fold higher in charr fed high protein (65–70%) diets than in fish fed live feed. A depression of pancreaticenzyme activities was noticeable when charr were fed starter diets in which fish meal was partially replaced by soybean meal. Specific growth rates (SGR) showed a cyclic pattern during early ontogeny of charr and SGR was highly correlated with food conversion efficiency. Activities of pancreatic enzymes also demonstrated a cyclic pattern but the periodicities of the growth cycle (50.6 days) and those of the enzymes differed. We hypothesize that both photostimulation and feedback responses might be involved in pancreatic responses in fish, which result in cyclic growth patterns.
Effect of somatostatin on intragastric pressure and smooth muscle contractility of the rainbow trout, Oncorhynchus mykiss Walbaum
Authors: Chan C. B. , Hale E.
Published: January 2006

These studies investigated the effects of somatostatin on gastric motility in the rainbow trout. Two experimental models were used, the isolated vascularly‐perfused stomach and isolated strips of gastrointestinal smooth muscle. Both models demonstrated that somatostatin can inhibit gastrointestinal motility and may therefore modulate gastric emptying in fish.

In the vascularly‐perfused stomach, somatostatin (10–1000 nm) decreased maximum and baseline intragastric pressure by 10–20% in the presence of stimulatory doses of carbachol or 5‐hydroxytryptamine. In addition, somatostatin (1 μm) inhibited by 50% the magnitude of spontaneous contractions generated by distension. Somatostatin had little effect on the pressure gradient or contractile frequency. These results suggest that somatostatin may negatively modulate gastric emptying in the rainbow trout.

In isolated gastric smooth muscle strips, somatostatin (100 pmol) inhibited tension stimulated by carbachol (circular orientation of muscle) or 5‐hydroxytryptamine (longitudinal orientation). These results correlated with those observed in the vascularly perfused stomach preparation. Somatostatin also decreased tension stimulated by carbachol and 5‐hydroxytryptamine in intestinal smooth muscle strips, suggesting that under some conditions somatostatin could increase gastric emptying rate by relaxing intestinal musculature.
Migration of hatchery reared juvenile Atlantic salmon,Salmo salarL., down a release ladder. 2. Effect of fish developmental strategy on speed and pattern of movement
Authors: Greenstreet S. P. R.
Published: January 2006

The behaviour of different types of Atlantic salmon smolt migrating down a release ladder were compared. Immature S2 smolts were faster through a release ladder, and their journey times less variable than S1 and mature male S2 fish. Journey time variability was less among stripped than among unstripped mature male smolts. The mean residence time of passive objects (oranges) in each pool of the ladder was correlated with pool surface area, whilst that of fish was correlated with pool volume. The general pattern of movement of smolts through the ladder was consistent with the hypothesis of non‐directed passive displacement of fish near the water surface. In fact, fish spent most of their time nearer the bottom of the pools with the result that their migration speed was slower than that of passive objects. Pools towards the top of the ladder had the highest volume and surface area and therefore offered the greatest hindrance to passive displacement. Immature S2 smolts may have been more active in seeking a passage through this barrier. In 1986 and 1987 no significant change in ladder travel time or fish condition factor was detected over the period May to July. In 1986 fish condition factors and variance in ladder travel time increased significantly in August. Immature S2 smolt migration may have been less nocturnal. Mature male smolts were affected more by high daytime water temperatures than immature S2 and S1 smolts.
Presence of Chame Dormitator latifrom (Richardson, 1844) (Pisces: Eleotridae) in the Galapagos Islands, Ecuador
Authors: Massay S. , Mosquera R.
Published: January 2006

Six specimens of Dormitator latifrons caught in Laguna del Cementerio, Isabela Island, represent the first record of this species in the Galapagos Islands.
Protogynous hermaphroditism in the half‐banded sea perch, Hypoplectrodes maccullochi (Serranidae)
Authors: Webb R. O. , Kingsford M. J.
Published: January 2006

The half‐banded sea perch, Hypoplectrodes maccullochi (Serranidae) exhibits protogynous hermaphroditism, based on the presence of transitional individuals collected from rocky reefs along the coast of New South Wales, Australia. Males dominated the larger size and age classes, whereas females predominated the smaller size and age groups. Histological preparations suggested that sex change occurs between 55–85 mm s.l. and 1 + to 4+ years of age. Three transitional phases were identified which varied according to the proportion of gametogenic tissue and remnant oocytes present within their gonads. All individuals greater than 85 mm s.l. were functional males containing well defined crypts of spermatids and spermatozoa. Remnant oocytes within these testes indicated prior female function. H. maccullochi were sexually monochromatic. The occurrence of some small males derived from pre‐spawning females suggested pre‐maturational sex change occurred in some individuals. Sex changing individuals were found in all the months of the year that gonads were examined in detail (January, February, April and June 1989). Fish were ripe in August and November. H. maccullochi conforms with the pattern of reproduction evident within the genus Hypopleclrodes.
Melano‐macrophage centres in whitemouth croaker, Micropogonius furnieri, as biological indicators of environmental changes
Authors: Macchi G. J. , Romano L. A. , Christiansen H. E.
Published: January 2006

Quantitative analysis of the melano‐macrophage centres in the Micropogonius furnieri were made. The results obtained showed a stimulation of the mononuclear phagocytic system related to the presence of contaminants.
Sexual status of Paralabrax humeralis (Serranidae) and infection by Philometra sp. (Nematoda: Dracunculoidea)
Authors: Oliva M. E. , Bórquez A. S. , Olivares A. N.
Published: January 2006

Evidence is presented that Philometra sp. infects Paralabrax humeralis only after first maturity
Growth and survival of carp (Cyprinus carpio L.) larvae in alkaline water
Authors: Korwin‐Kossakowski M.
Published: January 2006

Growth of carp larvae was significantly retarded in water with pH between 9.4 and 10.3, as compared with control conditions of pH 7.8–8.2. The survival rate was lower the higher the pH.
Measurements on ground or sectioned otoliths: possibilities of bias
Authors: Panfili J. , Ximenes M.‐C.
Published: January 2006

Back‐calculation usually requires measurements of growth marks revealed on otoliths by specific preparations. The standardization of the grinding (or sectioning) plane is necessary, but difficult, especially along the antero‐posterior axis. In order to show the importance of the grinding plane, tetracycline labelling of eel otoliths (Anguilla anguilla L.) has been used. This marking has a calcio‐traumatic effect on otoliths, which can be revealed with staining techniques. Unless the grinding plane is incorrect, the tetracycline labelling and the staining of the ground surface are then superposed.
Growth and energy budget in young grass carp,Ctenopharyngodon idellaVal., fed plant and animal diets
Authors: Cui Yibo , Liu Xiaofang , Wang Shaomei , Chen Shaolian
Published: January 2006

Young grass carp held under laboratory conditions were fed either duckweed or tubificid worms. Food consumption (C), faecal production (F), excretion (U), metabolism (R) and growth (G) were estimated for fish fed both diets. Fish fed tubificid worms had higher growth rates than those fed duckweed, in terms of wet weight, dry matter, protein, lipid and energy. Fish fed duckweed consumed more wet and dry matter than did the fish fed tubificids, but rates of protein and lipid consumption were lower. The energy budget was estimated to be 100C = 9F+ 8U+ 61R+ 22Gfor fish fed tubificids, and 100C = 35F+ 5U+ 51R+ 9Gfor fish fed duckweed. Linear relationships existed between specific growth rate in wet weight and rate of food absorption (consumption minus faecal production) in dry matter, protein or energy. Food type did not have a significant effect on these relationships. It was concluded that differences in growth rate between grass carp fed different diets were mainly caused by differences in absorption rate.