bluuebunny/crossref_metadata_2025 huggingface dataset:
A histological description of gonadal development and sex differentiation in the coho salmon (Oncorhynchus kisutch) for both untreated and oestradiol immersed fry
Authors: Foyle T. P.
Published: April 2005

Gonadal development is described in detail for coho salmon (Oncorhynchus kisutch) between hatching and 1000 degree‐days, post‐hatch, to aid sex reversal research. Germ cell morphology and sequence, vascular and reproductive duct development, and gross characteristics of the gonads are presented. Sex differentiation occurs by 380 degree‐days, post‐hatch (800 degree‐days, post‐fertilization) and is direct to male and female. Oocytes proliferate rapidly after differentiation while the testes enter a period of quiescence. Fry immersed for short durations in oestradiol (200 μg −1) are also examined. Hormone immersion advanced sex differentiation by 70 degree‐days. The immersions were applied early, at 20 and 90 degree‐days, post‐hatch, yet still altered the sex ratio and timing of differentiation. Definitive germ cells, which are abundant during this period, may be the type most receptive to steroid treatment.
Patterns of metamorphosis in summer flounder, Paralichthys dentatus
Authors: Keefe M. , Able K. W.
Published: April 2005

Summer flounder, Paralichthys dentatus, spawn over the continental shelf off the east coast of the United States from September to January with the peak in October–November. Based on plankton collections, mid‐metamorphic larvae (stages G‐H; mean s.l. 13.1 mm) enter Great Bay–Little Egg Harbor estuary in southern New Jersey as early as October with continued ingress through April. In the laboratory, mortality during metamorphosis ranged from 17 to 83% among treatment groups, and was significantly greater in flounder maintained at approximately 4°C relative to those maintained at ambient temperatures (daily average temperature 10.l°C). Laboratory‐reared summer flounder averaged 24.5 days (range 20 to 32 days) to complete metamorphosis (from Stage F– to Stage I) at ambient spring temperatures (daily average temperature =16.6° C). The time to completion of metamorphosis in wild‐caught flounder maintained in the laboratory was clearly temperature dependent. Both cold and ambient temperature treatments resulted in delayed metamorphosis such that, at ambient winter temperatures (daily average=6.6°C), partial metamorphosis (from Stage H – to Stage I) required as much as 92.9 days (range 67 to 99 days). There was no apparent effect of starvation on either mortality or time to completion of metamorphosis at cool water temperatures (< 10° C). It appears that prevailing temperature conditions influence the duration of metamorphosis in summer flounder, and that mortality during metamorphosis may play a significant role in the population dynamics of this species.
Sulphide tolerance and adaptation in the California killifish, Fundulus parvipinnis, a salt marsh resident
Authors: Bagarinao T. , Vetter R. D.
Published: April 2005

Hydrogen sulphide is a toxicant naturally produced in hypoxic marine sediments, hydrocarbon and brine seeps and hydrothermal vents. The California killifish, a salt marsh resident, is remarkably tolerant of sulphide. The 50% lethal concentration is 700 μM total sulphide in 96 h, and 5 mM in 8 h (determined in flow‐through, oxygenated sea water). Killifish exposed to sulphide produce thiosulphate which accumulates in the blood. The cytochrome c oxidase (a major site of toxicity) of the killifish is 50% inhibited by <1 μM sulphide. Killifish liver mitochondria are poisoned by 50–75 μM sulphide but can oxidize 10–20 μM sulphide to thiosulphate. Sulphide causes sulphhaemoglobin formation (and impairment of oxygen transport) at 1–5 mM in vitro and to a small extent at 2 mM in vivo. Killifish blood neither catalyses sulphide oxidation significantly nor binds sulphide at environmental (low) sulphide concentrations. Exposure to 200 μM and 700 μM sulphide over several days causes significant increases in lactate concentrations, indicating shift to anaerobic glycolysis. However, individuals with the most lactate die. In terms of diffusible H2S, the killifish can withstand concentrations two to three orders of magnitude greater than would poison cytochrome c oxidase. The high sulphide tolerance of the killifish, particularly of concentrations typical of salt marshes, can be explained chiefly by mitochondrial sulphide oxidation. Sulphide tolerance and mitochondrial sulphide oxidation in the killifish have a constitutive basis, i.e. do not diminish in fish held in the laboratory in sulphide‐free water for 1–2 months, and are improved by prior acclimation.
Reproductive strategies and early development of three freshwater gobies
Authors: Daoulas Ch. , Economou A. N. , Psarras Th. , Barbieri‐Tseliki R.
Published: April 2005

Three species of gobiid fish inhabit the freshwater Lake Trichonis of western Greece. Two of these species, Economidichthys pygmaeus and E. trichonis are endemic, and the third is the widespread Knipowitschia caucasica. There are habitat separations between the three species, E. pygmaeus and E. trichonis prefer vegetated areas, the first being fully demersal at all stages of development and the second being semi‐demersal. Knipowitschia caucasica prefers sandy bottoms and is distributed in shallower waters. Female E. pygmaeus and E. trichonis spawn in nests prepared by the males in the cavities of broken reeds. The males subsequently guard the eggs until they hatch, with females playing no role in parental care. Economidichthys trichonis is probably the smallest freshwater European species. Its eggs are ovoid, measuring about 0.64 × 0.58 mm, from which tiny, unpigmented and incompletely developed pelagic larvae hatch out after an incubation period lasting less than 1 day at a water temperature of 19.5° C. The eggs of E. pygmaeus are cylindrical and larger, measuring about 2.38 × 0.89 mm, from which relatively large, strongly pigmented and ontogenetically more advanced larvae hatch out after a longer incubation period. Both species reproduce only once in their lifetime, at the age of 1 year, and die shortly after spawning, but the breeding season involves several spawnings by each individual fish. These biological, developmental and reproductive characteristics are discussed in relation to current theories on evolution of life‐historics.
Suppression of first egg mitosis induced by heat shocks in the rainbow trout
Authors: Diter A. , Quillet E. , Chourrout D.
Published: April 2005

Chromosome doubling by mitotic interference was achieved by heat‐shocking rainbow trout (Oncorhynchus mykiss) eggs fertilized with either intact or genetically inactivated sperm. Tetraploid and mitotic gynogenetic individuals resulted from these treatments respectively. The temperature (27–33° C), duration (2–30min) and application time (2–4 h 40min after egg activation, at 10° C) of the thermal shock were investigated. The best yields of gynogenetics usually resulted from shocks of medium intensity (30° C for 9 min, 31° C for 5 min, 32° C for 4 min). A range of optimal application times was determined between 3 and 4 h after egg activation. A strong maternal effect on gynogenetic yield, irrespective of the application time, was observed. The treatments found to produce the highest yields of gynogenetics (up to 23% survival at hatching, relative to that of the diploid control) should not be used for tetraploid induction because of their rather low efficiency in chromosome doubling (around 70%). Tetraploid populations where viable residual diploids are undesirable should be produced by more intense shocks.
Drag reduction of fish skin mucus: Relationship to mode of swimming and size
Authors: Bernadsky G. , Sar N. , Rosenberg E.
Published: April 2005

Drag reduction by skin mucus was measured from Gulf of Eilat fish. Activity of burst swimmers was greater than manoeuvre swimming fish. Large fish from the same species had higher mucus drag reducing activity than smaller specimens.
Improvements to Atlantic salmon anterior kidney metaphase yields following phytohemaglutinin injection
Authors: Pendás A. M. , Morán P. , García‐Vázquez E.
Published: April 2005

Increased and reproducible yields of metaphase spreads were obtained when Atlantic salmon parr were injected parenterally with PHA (0.03 mgg‐1). Maximum yields were obtained when two separate injections were given at 72 and 36 h prior to sacrifice.
A specimen of Salmo trutta (Pisces: Salmonidae) possessing an additional dorsal fin
Authors: Raadik T. A.
Published: April 2005

A specimen of brown trout, Salmo trutta, with a supernumerary dorsal fin located just posterior to the nape is documented from the Yarra River, Victoria, Australia.
Clutch production in the darter Etheostoma lynceum and its implications for life‐history study
Authors: Heins D. C. , Baker J. A.
Published: April 2005

We tested two hypotheses that describe previously untested assumptions about the appropriate stage(s) for use in determining clutch sizes in darters. Three sequential stages of clutch/ovarian development are recognized: mature oocyte/ovary, ripening oocytc/ovary, and ripe oocyte/ovary. Mean ratios of clutch size to female length (relative clutch size, RCS) were significantly smaller and variances of RCS were significantly greater in ripe females when compared to mature and ripening females. Correlation coefficients for the relationship between clutch size and standard length (S.L.) were significantly greater for mature and ripening females than for ripe females. Mean clutch size, adjusted for the S.L. covariate, was significantly greater in mature and ripening females than in ripe females. Thus, we conclude that counts of eggs from ripe females yield fecundity estimates that are lower and more variable than estimates from counts of oocytes from mature and ripening females collected at the same time. Based on this conclusion, we discuss methods for developing fecundity estimates in darters. Our results may be broadly applicable to other taxa of fishes with group‐synchronous ovum development.
Spatial arrangement of fish gill secondary lamellar cells in intact and dissociated tissues from rainbow trout (Oncorhynchus mykiss) and Atlantic salmon (Salmo salar)
Authors: Pentuce W. S. , Eddy F. B.
Published: April 2005

Gill structure of rainbow trout and Atlantic salmon was investigated using cell disaggregation and dry fracture techniques for scanning electron microscopy (SEM), allowing new interpreta‐tions of the structure of the secondary lamella. The basement membrane underlying the lamellar epithelium (secondary epithelium) was shown to be a tough sheet with numerous depressions corresponding to underlying pillar cells. This membrane is probably the most important structural element of the secondary lamella, capable of withstanding considerable mechanical stress. For the first time the structure of the apical surface of the secondary lamella was shown by SEM to consist of an outer microridged coat overlying a fibrous coat which appears continuous with the extracellular matrix surrounding the rest of the cell. When cells were detached they rounded up and the external microridged coat became more vesicle like, indicating the labile nature of this coat. In cell suspension preparations, epithelial, mucus and chloride cells are present as well as many blood derived cells such as erythrocytes, presumptive leucocytes and thrombocytes.
Life history of the silverside Atherinomorus lacunosus (Atherinidae) in New Caledonia
Authors: Conand F.
Published: April 2005

The abundance, the seasonal variation and the life history of the silverside, Atherinomorus lacunosus, are studied from fish caught in the lagoons around New Caledonia. About 270 nights of fishing were carried out between 1980 and 1983. The silverside is present in most of the fishing hauls but seldom in large quantities. Fish reproduce from September to December at 1 year of age. At this time their size is about 10 cm. Mortality is high and a few individuals can survive a second year and reach 13 cm. Results from other studies indicate that in a less seasonally contrasted environment than the lagoons of New Caledonia, A. lacunosus has several spawning periods during the year. This species is thus able to adjust its phenology to the environmental conditions.
The composition and nutritional status of the diet of Oreochromis niloticus in Lake Chamo, Ethiopia
Authors: Getachew T.
Published: April 2005

The stomach contents of Oreochromis niloticus from L. Chamo were microscopically examined and chemically analysed in order to study the relationship between food quality, growth and condition. More than 20 genera of phytoplankton plus Copepoda, Rotifera and nauplii were present in the stomach contents. The diatom, Melosira, was the most dominant alga in the diet, contributing about 30% of the organic matter. The composition of the food in terms of organic nutrients was dominated by carbohydrate (20.3% dry weight). Both protein and fat made low contributions to the diet; 10% and 5.8% dry weight, respectively. The overall performance of the fish in assimilating food was high: 43.3% for ash free dry weight, 61.2% for protein, 57.2% for lipid, 29% for carbohydrate and 55.7% for energy. The digestible protein‐energy ratio was 15.7 mg kJ−1, suggesting that the food was qualitatively good both for fast growth and for maintaining good condition. It was concluded that the small amount of good quality food ingested, the low fish population density in the lake and the high temperature of the water are the major factors responsible for making O. niloticus a fast‐growing fish in Lake Chamo.
Effects of season and body‐size on the distribution and diet of the Iberian chub Leuciscus pyrenaicus in a lowland catchment
Authors: Magalhães M. F.
Published: April 2005

Seasonal and ontogenetic variations in space and food use by Leuciscus pyrenaicus were analysed in a Portuguese lowland catchment. Large fish occurred mostly in deep permanent‐flowing sites whereas small fish occurred mostly in the shallowest intermittent‐flowing site. No seasonal or size‐related changes in feeding intensity were found, but the diet changed both across seasons and throughout ontogeny. The diet was dominated by aquatic prey over all seasons, but during winter and summer more plant material and terrestrial prey, respectively, were eaten. Throughout ontogeny fish shifted from soft‐bodied to hard‐shelled prey and decreased animal prey breadth. Mean prey size increased with fish size but the prey size spectrum was more variable for medium‐sized fish than for either small or large fish. It is suggested that: (i) large fish avoid shallow drying areas owing to the risk of mortality, either by thermal and respiratory stresses or increased predation by mammals and birds; (ii) seasonal changes in diet are a response to differences in prey availability; and (iii) morphological constraints, prey handling costs and habitat partitioning are responsible for size‐related changes in diet.
Ceratomyxa spp. (Protozoa: Myxosporea) infections in wild and cultured sea bass, Dicentrarchus labrax, from the Spanish Mediterranean area
Authors: Alvarez‐Pellitero P. , Sitjà‐Bobadilla A.
Published: April 2005

Ceratomyxa labracis and Ceratomyxa diplodae, parasitic in the gall bladder of wild and cultured Mediterranean sea bass (Dicentrarchus labrax L.) were studied. Prevalences were clearly higher in cultured fish, especially for C. labracis. Starvation seems to favour the appearance of ceratomyxosis. Infection varied seasonally, with maxima in winter and minima in summer, a pattern almost contrary to temperature. Prevalence of C. labracis decreased in older fish. No clear influence of host sex was observed, and the apparent negative association between the two Ceratomyxa spp. was not confirmed statistically. Different degrees of histopathological damage of the gall bladder were observed by light and electron microscopy, mainly consisting of vacuolation, deformation or even necrosis of epithelial cells, and thickening and inflammation of the subepithelial connective tissue. Trophozoites appeared frequently lining the epithelium, closely attached to the cell surface or even forming invaginations in it. The importance of ceratomyxosis for sea bass and the influence of culture and stress conditions are discussed.
A phyletic study on lacustrine haplochromine fishes (Perciformes, Cichlidae) of East Africa, based on scale and squamation characters
Authors: Lippitsch E.
Published: April 2005

Phyletic relations within the haplochromine cichlids of East Africa were investigated using scale and squamation characters. Within the L. Victoria–Edward–Kivu species flock most of the genera proposed in Greenwood's revision could be confirmed by this approach. In addition the genera could be interrelated phylogenetically. They form two distinct superlineages comprising several genera each. The genus Astatotilapia as conceived by Greenwood is diphyletic. The fluviatile members of the genus form the sister taxon of the L. Victoria–Edward–Kivu flock, while the rest are a subgroup of that flock. The flock seems to be of monophyletic origin.
Coexistence of Mugil cephalus and M. curema in a coastal lagoon in the Gulf of Mexico
Authors: Aguirre A. L. Ibanez
Published: April 2005

Mugil cephalus and M. curema coexist in Tamiahua Lagoon, with no difference in diet or digestive system, but with a separation of 3 months in reproductive timing.
Observations of the biology and parasites of postsmolt Atlantic salmon, Salmo salar, from the Norwegian sea
Authors: Holst J. C. , Nilsen F. , Hodneland K. , Nylund A.
Published: April 2005

The main food items of postsmolt Atlantic salmon caught in the Norwegian sea during summer 1991 were Parathemisto spp. and herring (Chipca harengus). The most prevalent parasite species were Chloromyxion sp., Apatemon sp., H. adunction, A simplex and I. salmonis.
Winter feeding ecology of cod (Gadus morhua) in a fjord of southern Norway
Authors: Hop H. , Danielssen D. S. , Gjøsæter J.
Published: April 2005

We investigated the winter feeding ecology of cod (Gadus morhua) in the Risørfjord and Flødevigen areas on the Skagerrak coast, southern Norway. Diets from the ice‐covered Risørfjord were compared with diets from the more coastal Flødevigen area. In the Risørfjord area the diet featured numerically both decapods (56.0%) and fish (27.8%), but fish dominated by mass (75.1%). The most numerous dietary items from the Flødevigen area were decapods (48.1%) and isopods (30.6%), although fish still made up the bulk of the diet's mass (52.6%). Diets at Flødevigen shifted from winter to spring, as polychaetes became important numerically (67.8%) and also contributed substantially by weight (53.6%). Since cod feed opportunistically, differences between areas and seasons probably reflected differences in prey diversity and abundance. Prey size variability increased with increasing predator length, but maximum prey size relative to predator length was constant at about 9%. Prey fish increased in both length and numbers with the length of cod, particularly in the Risørfjord area, where fish were more important in the diet than at Flødevigen. However, the majority of fish consumed in both areas were small gobiids. Based on growth patterns observed in otoliths, with opaque zones (indicating faster growth) formed during winter, the quality and quantity of the winter diet may determine annual growth rates of cod on the Skagerrak coast. Fish and decapods constituted important, high energy food sources, and there was little indication that cod were food limited during winter in this area.
Feeding biology of bleak, Alburnus alburnus, in Lake Koronia, northern Greece
Authors: Politou C.‐Y. , Economidis P. S. , Sinis A. I.
Published: April 2005

The feeding of bleak, Alburnus alburnus (L.), was studied in a natural eutrophic lake of northern Greece by an analysis of gut contents. Feeding was more intense during the first half of the day. Monthly analyses showed temperature‐dependent feeding intensities, which were high during summer and the beginning of autumn and showed a decline in winter. The low feeding intensity in April coincided with the maximal value of the GSI. Bleak is a zooplankton feeder mainly, consuming Copepoda and Bosmina all the year round. During the hot period the diversity of its food increased. Other Cladocera, mainly Diaphanosoma, but also Moina, Daphnia and other less abundant genera, were found also. Meanwhile, Hydracarina and insect nymphs were found frequently, but in very low quantities. The size of bleak did not play an important role in its food composition. The stenophagic nature of its feeding could be explained in terms of the abundance of zooplankton in the environment. The influence of feeding intensity on the condition factor of the species is discussed.
Ultrastructure of the primary gill lamellae of Scomber australasicus
Authors: Perera K. M. L.
Published: April 2005

The ultrastructure of the primary epithelium, and the efferent half of the subepithelium, of the primary gill lamellae of slimy mackerel (Scomber australasicus) is described. The following cells are identified and described: light nucleated epithelial cells (surface and basal), dark nucleated cells, mucous cells, acidophilic cells, type 1 cells, type 2 cells, type 3 cells and chloride cells in the epithelial region, and subepithelial cells A and B, fibroblasts, chondrocytes, cells of the wall of efferent blood vessel and some blood cells in the subepithelium.
Genetic characterization in four sciaenid species from the Arabian Sea
Authors: Menezes M. R. , Naik S. , Martins M.
Published: April 2005

Four sciaenid species Johnieops dussumieri, Kathala axillaris, Pennahia macropthalmus and Otolithes ruber were analysed electrophoretically for genetic variation at 18 loci (16 in P. macropthalmus and O. ruber). Twelve loci were polymorphic in J. dussumieri, 10 in K. axillaris, three in P. macropthalmus and 12 in O. ruber (P<0·99). Average heterozygosity ranged from 0·033 ± 0·100 to 0·070 ± 0·122. The allele frequencies of 14 loci were used to estimate Nei's genetic distance (D̄). The D̄ values ranged from 0·334 to 0·612. Three isozyme loci (LDH‐B*, MDH‐2* and G3PDH‐1*) were found to be the most reliable species‐specific markers.
Growth of carp (Cyprinus carpio) white axial muscle; hyperplasia and hypertrophy in relation to the myonucleus/sarcoplasm ratio and the occurrence of different subclasses of myogenic cells
Authors: Koumans J. T. M. , Akster H. A. , Booms G. H. R. , Osse J. W. M.
Published: April 2005

In white axial muscle of carp addition of new fibres to the muscle mass (hyperplasia) decreased with increasing length of the fish. This was deducted from the decrease in the amount of small fibres. In carp larger than about 40 cm standard length (s.l.) hyperplasia no longer occurred (small fibres were absent) and muscle growth only occurred by means of hypertrophy (growth of existing fibres). The stage of growth in which many new fibres were added showed a relatively fast increase in trunk weight, as calculated from growth curves. During the stage of fast growth with a high occurrence of hyperplasia, the DNA/protein ratio decreased. The high percentage of postmitotic myosatellite cells isolated from carp of 5 cm s.l. suggests that in hyperplasia a subpopulation of already differentiated myosatellite cells formed in an earlier stage of development is incorporated in new muscle fibres. The increase of the relative importance of hypertrophy appears to be correlated to an increase in the percentage of proliferating myosatellite cells 17 h after isolation in vitro. This suggests that in hyperplasia and in hypertrophy different subpopulations of myosatellite cells are involved.
Differences in plasma cortisol and cortisone dynamics during stress in two strains of rainbow trout (Oncorhynchus mykiss)
Authors: Pottinger T. G. , Moran T. A.
Published: April 2005

Plasma levels of cortisone, a steroid hormone of potential physiological significance in fish, have rarely been measured. This study examines the interrelationship between circulating levels of cortisone and the major teleost corticosteroid, cortisol, in the blood of two strains of rainbow trout subject to confinement stress, a condition know to stimulate corticosteroidogenic activity. In unstressed fish from both strains, mean plasma cortisol levels were within the range 0.4–7.5 ng ml−1. Mean plasma cortisone levels were within the range 7.1–15.9 ng ml−1. Plasma cortisol levels were elevated within 5 min of the onset of strees and reached peak values within 45 min, although there was a marked difference betweed the maxima observed in the two strains (strain 1:70 ng ml−1; strain 2:150 ng ml−1). The rate of increase of plasma cortisone levels during strees was more rapid than that of cortisol, maximum values (strain 1:100ng ml−1; strain 2:160 ng ml−1) being reached within 10 to 20 min of the onset of stress. This rapid stress‐induced elevation of plasme cortisone has not previously been reported in fish. We suggest that rapid conversion of cortisol to cortisone during the initial response to stress accounts for the appearance of large amounts of cortisone in the blood, indicating that circulating for the appearance of large amounts of cortisone in the blood, indicating that circulating levels of cortisol alone do not fully reflect the secretory activity of the interregnal during the initial of cortisol alone do not fully the secretory activity of the interregnal during the initial phase of the stress response. The results also indicate that the rate of clearance of cortisone from the circulation may be a major factor in determining stress‐stimulated levels of plasma cortisol.
Reproductive biology of a Red Sea goby, Silhouettea aegyptia, and a Mediterranean goby, Pomatoschistus marmoratus, in Lake Timsah, Suez Canal
Authors: Fouda M. M. , Hanna M. Y. , Fouda F. M.
Published: April 2005

The reproductive biology of the Red Sea goby Silhouettea aegyptia, and Mediterranean Pomatoschistus marmoratus, has been studied in Lake Timsah, Suez Canal. Male: female sex ratio was 1: 1 7 in S. aegyptia and 1: 2 7 in P. marmoratus. Size at first maturity was 20 mm (s.l.) in S. aegyptia and 24 mm in P. marmoratus. The breeding season of S. aegyptia extended from March to September with most gonadal activity in May, whereas in P. marmoratus, it stretched from. November until the following April with a peak in February. Hepatosomatic index for both species exhibited monthly fluctuations and an inverse correlation with gonadosomatic index was evident. Oocyte size‐frequency distribution indicated several modes at 400, 600 and 800 μm during the breeding season. Fecundity of S. aegyptia ranged from 152 to 782 with an average of 468 eggs, whereas in P. marmoratus it varied between 293 and 1300 with an average of 603 eggs. Fecundity was related curvilinearly to fish length, body weight and ovary weight. Recruitment of young fish to the adult populations occurred in late July and early August for S. aegyptia and during March for P. marmoratus. Life history pattern indicated that both species of gobies are successful colonists of Lake Timsah, Suez Canal.
Lipid dynamics in the common torpedo, Torpedo torpedo, from the south eastern Mediterranean
Authors: Abdel‐Aziz S. H. , El‐Nady F. S.
Published: April 2005

Liver stores the major part of lipids in both mature and immature Torpedo torpedo of both sexes. Fluctuations in the lipid contents of liver, muscles and gonads of immature fish followed the relative change in food intake throughout the year. Hepatic and muscular lipids in mature females diminished before ovulation and were intensively consumed in the last stages of gestation (in pregnant females). After parturition, the recovery of the lipid stores was very rapid due to intensive food uptake. Storing of hepatic lipids in mature males started a little before gonadal maturation and reached a maximum in January and February while gonadal lipids decreased in the same period. Gonadal lipid for both sexes fluctuated in parallel to fluctuations in the GSI. Water content showed significant inverse correlation with lipid content in both liver and gonad tissues, but no significant correlation was recorded in the muscle tissues.
Arctic charr strain crosses: effects on growth and sexual maturity
Authors: Nilsson J.
Published: April 2005

Three Arctic charr strains and their crosses were evaluated with respect to growth and sexual maturation frequency. No significant heterosis was observed for growth. One out of five crosses was heavier, but not significantly so, than the best performing parental strain at ages 1 + and 2. The five other crosses did not perform better than the best performing parental strain at any age. Cross‐breeding was not recommended as an effective method to improve growth performance in Arctic charr. Growth performance of reciprocal crosses differed significantly in all strain combinations: crosses resembled more the male parent strain than the female parent strain. ANOVA for male maturation frequency showed a highly significant effect of the male parent strain and a weakly significant effect of female parent strain. In the Ottsjö strain mature males were significantly larger than immature fish and females. Such size difference was also observed in the offspring when sires of the Ottsjö strain were crossed with dams of the faster growing Honavan strain or with dams of the Rensjö strain. When Ottsjö dams were crossed to sires of the other strains no significant size difference between mature males and other fish was found.
On the pattern of correlation between the fecundity, length, weight and age of pikeperch Stizostedion lucioperca
Authors: ŽIvkov M. , Petrova G.
Published: April 2005

Great diversity was found in the correlation between absolute fecundity (F) and the length (L) and age (t) of pikeperch, Stizostedion lucioperca (L.) in 10 water bodies that differed in their geography, morphology, and ecology. However, this diversity is only apparent, and the Flt(L) relationships are logistic, with the linear, power, exponential and logarithmic functions found in different populations, representing segments of the sigmoid curve. The expected linear relationship between fecundity and weight was found for the fish in seven water bodies, but it was curvilinear in three others. In the latter waters, pikeperch matured at a comparatively young age, with shorter length, and lighter weight, yet their initial fecundity was comparatively lower.
Early ontogeny of Galeichthys feliceps from the south east coast of South Africa
Authors: Tilney R. L. , Hecht T.
Published: April 2005

The early development of Galeichthys feliceps (Valenciennes, 1840) was investigated using a combination of incubator‐reared embryos and embryos removed from the buccal cavities of wild‐caught parents. The eggs were 15·7 mm in diameter and the average brood size was 49. Hatching occurred at an advanced developmental state after approximately 75–80 days, when branchial and fin differentiation were complete. Exogenous feeding began within the adult buccal cavity shortly after hatching. The young were released as juveniles after approximately 140 days, at a total length of 54 mm.
The role of the pericardium in cardiac function in the dogfish,Squalus acanthias
Authors: Franklin C. E. , Davie P. S.
Published: April 2005

Opening the pericardium to the ambient bathing fluid surrounding thein situperfused dogfish (Squalus acanthias) heart caused a precipitous fall in cardiac output. Cardiac output fell by 55% despite the rise of mean input pressure from subambient, to near zero levels. Lower cardiac output caused a fall in mean output pressure but not diastolic pressure as this was set by the experimenters. With the pericardium intact, the heart was filled by suction. With an open pericardium the magnitude of negative input pressures was severely reduced. None the less, far short periods within the cardiac cycle, the heart was still able to generate subambient pressures in the atrium and so draw fluid from the central veins.
Chromosome analysis of Bothus podas (Pisces, Pleuronectiformes) from the Mediterranean Sea
Authors: Vitturi R. , Catalano E. , Colombera D.
Published: April 2005

A modal diploid number 2n=38 has been determined in both sexes of the pleuronectiform Bothus podas from the Gulf of Palermo (Mediterranean). An XX‐XY sex‐determining mechanism presumably occurs in this species. Application of silver staining (NORs) along with G‐ and C‐banding techniques showed that secondary constrictions occurring in a large metacentric pair were variable in length in different fish. Polymorphisms of these areas seem to have a genetic, rather than transcriptional, basis.
Rates of growth and protein synthesis correlated with nucleic acid content in fry of rainbow trout, Oncorhynchus mykiss: effects of age and temperature
Authors: Mathers E. M. , Houlihan D. F. , McCarthy I. D. , Burren L. J.
Published: April 2005

Groups of recently hatched fry of rainbow trout, Oncorhynchus mykiss were maintained in the laboratory in order to investigate the effects of age, ration level and temperature on whole body growth, nucleic acid concentrations, protein synthesis rates and enzyme activities. In fry of up to 30 days after hatching, which were feeding but still had some yolk sac, no significant change in mean RNA concentration was observed with ration level. In older fry of 50 days or more, when the yolk sac was completely absorbed and exogenous feeding fully established, the concentration of RNA was correlated with the rate of protein growth. RNA concentrations and activities of citrate synthase and lactate dehydrogenase were significantly different between fed and starved fry. As water temperature was raised (from 5 to 15° C), higher rates of protein growth were brought about by an increase in the rate of protein synthesis and also by increased efficiency of retention of synthesized protein (reduced protein turnover). In fed fry, no change in RNA concentration was found with increasing temperature, while the amount of RNA per cell (RNA: DNA) decreased, indicating that increased rates of protein synthesis were due to increased RNA efficiency.
Effects of river red gum, Eucalyptus camaldulensis, litter on golden perch, Macquaria ambigua
Authors: Gehrke P. C. , Revell M. B. , Philbey A. W.
Published: April 2005

Aquaria with added river red gum, Eucalyptus camaldulensis, litter became hypoxic, with decreased pH and contained up to 30 mg 1−1 tannin and lignin. Survival of golden perch, Macquaria ambigua, larvae in aquaria treated with a simulated annual litter density of 450 g m−2 for 72 h was 14·9% for 15‐day‐old larvae and 0% for 8‐day‐old larvae. A litter density of 1223 g m−2 resulted in total mortality for both age groups of larvae. Aeration increased survival of larvae to a minimum of 68·8% in 1223 g m−2 litter treatments compared to 89·8% in aerated controls and 86·8% in non‐aerated controls. A kinetic behavioural assay was used to detect alarm responses in golden perch larvae and juveniles exposed to leachates from river red gum bark, leaves and wood. Eight‐day‐old larvae exposed to bark and wood leachates (0·001–10 g 1−1) exhibited an initial period of hyperactivity, followed by a concentration‐dependent decrease in spontaneous activity. Larvae exposed to leaf leachates displayed only a decrease in spontaneous activity. Four‐month‐old juveniles exposed to wood leachates were also initially hyperactive, then progressively developed mild hypoactivity at increasing leachate concentrations. Juveniles exposed to wood leachates at 20g 1−1 for 30min suffered 97·5% mortality in 96 h. Wood leachates induced dose‐dependent lamellar fusion, epithelial dissociation and necrosis in the gills. The presence of toxic leachates and low oxygen availability in flooded river red gum forests may make these habitats unsuitable as nursery areas for native fish.
Monobothrium wageneri: another imported tapeworm established in wild British freshwater fishes?
Authors: Gibson D. I.
Published: April 2005

The caryophyllidean monozoic tapeworm Monobothrium wageneri is recorded for the first time in the U.K. in tench Tinca tinca from four different sites in S.E. England. The likelihood that this is an exotic import is discussed. It is considered that the weight of evidence indicates that it has been introduced into the U.K. probably in ornamental tench.
Migration, growth and survival of wild and hatchery‐reared anadromous Arctic charr (Salvelinus alpinus) in Finnmark, Northern Norway
Authors: Finstad B. , Heggberget T. G.
Published: April 2005

Two groups of anadromous Arctic charr (Salvelinus alpinus) (size 200–350 mm) reared in heated water (6–12° C) under simulated natural photoperiod were individually tagged and released in spring 1988. The fish were released at two sites, in the estuary of the River Halselva and in the fjord, 2 km from the river mouth. Growth, timing of migration and survival of these hatchery‐reared fish was compared to that of wild anadromous charr of the same size over a 4‐year period. The hatchery‐reared charr had poorer growth than the wild fish during their first year in sea water. They also resided longer in the sea and had a slightly lower survival than wild fish. During the second year, hatchery‐reared charr displayed good growth, and after the third sea‐season the fish were ready for slaughter at a size of approximately 800g. The results suggest that the successful development of Arctic charr ranching will be dependent upon production and release strategies that lead to improved migratory and feeding behaviour of the fish during their first season at sea.
A novel synthetic probe for DNA fingerprinting salmonid fishes
Authors: Bentzen P. , Taylor E. B. , Wright J. M.
Published: April 2005

The synthesis and use of a novel DNA probe that gives clear, highly polymorphic DNA fingerprints for salmonid fishes is described. When used at high stringency, the Ssal‐rep probe detects a group of minisatellite sequences limited to the Salmonidae and related families.
The migration and growth of O‐group flounders Pleuronecte* flesus in mixohaline conditions
Authors: Hutchinson S. , Hawkins L. E.
Published: April 2005

Post‐larval flounders have been found to migrate into the mixohaline region of the River Itchen, southern England, in mid April. These fish were 7‐9 mm total length and at the point of metamorphosis. The mean length and growth rate of O‐group flounders at this site was measured at monthly intervals.
Effects of two Avtemia diets with different contents of polyunsaturated fatty acids on the lipid composition of larvae of Atlantic herring (Clupea harengus
Authors: Navarro J. C. , Batty R. S. , Bell M. V. , Sargent J. R.
Published: April 2005

Atlantic herring larvae (Clupea harengus) were fed two enriched Artemia diets with different contents of (n‐3) highly unsaturated fatty acids (HUFA), one containing low levels of 20: 5(n‐3) and no 22: 6(n‐3), the other containing substantial levels of both 20: 5(n‐3) and 22: 6(n‐3). After 30 days of culture, fatty acid compositions of lipid classes in the heads, bodies and eyes of the larvae were analysed. Fish fed Artemia with the low (n‐3) HUFA diet lacking 22: 6(n‐3) had lower amounts of total (n‐3)HUFA and, in particular, of 22:6(n‐3) in individual phospholipids and total neutral lipids of heads, bodies and eyes as compared to fish fed Artemia with high levels of (n‐3)HUFA. The amount of 22: 6(n‐3) in the fatty acids of phosphatidyl‐ethanolamine of eyes was particularly susceptible to dietary depletion. The implications of these findings are discussed, particularly in relation to dietary requirements for 22: 6(n‐3) during development of neural tissue in predatory fish iarvae.
Interference affects food‐finding rate in schooling sticklebacks
Authors: Ranta E. , Juvonen S.‐K.
Published: April 2005

Experiments on sticklebacks seeking for food patches show that foraging in schools enhances food‐finding rate of individuals. A stochastic information‐sharing model characterizes food‐seeking behaviour in which food‐finding by one in a school of fish results in food‐sharing by many. The model predicts the food‐finding rate of a randomly selected individual in a school of n fish to be that of a solitary forager weighted by the inverse of the school size, 1/n. In sticklebacks this seems not to be the case, however. Though the food‐finding rate of individuals in the school reduces with n, the improvement is much slower than predicted by the basic model. We argue that a variant of the information‐sharing model accounting for interference among individuals affecting their food‐seeking behaviour fits the data better.
Population ecology of pike‐cichlid, Crenicichla lepidota, in two streams of the Brazilian Pampa subject to a severe drought
Authors: Lobón‐Cerviá J. , Utrilla C. G. , Querol E. , Puig M. A.
Published: April 2005

Scales were valid for age determination of pike‐cichlid Crenicichla lepidota Heckel in two Brazilian streams, since, for every age‐class, annual rings (annuli) were formed once a year, in August. Back‐calculated Jengths‐for‐age coincided with those obtained by inspecting the monthly length‐frequency distributions. Only 11 reproductive females were captured (length range 9.6–16 cm, age 1+ and 2 +) and their fecundity (F) increased with fish length (L) according to: F= 2.4027 L2.3631. Average annual density and biomass in four localities of Zanga do Campus were 2194, 1676, 1824 and 1071 individuals ha−1 and 17.2, 12.1, 13.8 and 18.7 kg ha−1and about 1000 individuals ha−1 and 8.5 kg ha−1 in three combined sites of Zanga do Barbará. The annual production ranged between 18.5 and 32.7 kg ha−1 a −1 in the first stream and 8.7 kg ha −1a −1 in the other. Feeding tactics differed between streams and age‐classes (0+v. 1+/2+). In winter, the 0+ age‐class in Zanga do Campus fed mainly upon Ephemeroptera (Baetidae) but in other months also fed on zooplankton. In winter, these age‐classes in Zanga do Barbara preyed upon benthic species but the contribution of different taxa varied between months. In January, these fish preyed exclusively upon Chydoridae and fish. The effects of a severe drought (November‐February) upon these parameters are discussed.
Gill Na+,K+‐ATPase activity, plasma cortisol level, and non‐specific immune response in Atlantic salmon (Salmo salar) during parr‐smolt transformation
Authors: Olsen Y. A. , Reitan L. J. , Røed K. H.
Published: April 2005

Atlantic salmon (Salmo salar) yearling presmolts were reared under two different photoperiod regimes (simulated natural photoperiod, SNP, and continuous light, CL) and identical ambient temperature conditions from 21 November 1990 until 29 May 1991. Sampling was done biweekly from 21 February. Gill Na+,K+‐ATPase activity increased under both photoperiod regimes from early April, concurrently with the increase in ambient temperature. The initial increase and final levels (29 May) in enzyme activity were much lower in the CL regime fish. Seawater challenge tests (24 h, 35 ppt) on 2 and 15 May resulted in lower plasma chloride levels in the SNP regime fish, indicating better hypo‐osmoregulatory ability. This difference wasANNOUNCEMENT not present on 29 May. Resting plasma cortisol levels increased from March under both regimes, but the increase was much greater in the SNP regime fish (75 nm on 29 May v 22 nm in the CL regime). The individuals from the SNP regime were of lower weight and condition coefficient on 29 May, whereas length was uniform. Plasma lysozyme activity was unchanged throughout the sampling period, with the CL regime fish showing an overall higher activity. The in vitro leucocyte stimulation test did not indicate a reduced immune response in May in smolting fish exposed to the simulated natural photoperiod regime compared to fish reared under continuous light.
Pack‐hunting in two species of catfish, Clavias gariepinus and C. ngamensis, in the Okavango Delta, Botswana
Authors: Merron G. S.
Published: April 2005

During the annual drawdown in the Okavango Delta, Botswana, large shoals of catfish migrate upstream in the main river channels. The examination of samples of the sharptooth catfish Clarias gariepinus and blunttooth catfish C. ngamensis revealed that they were pack‐hunting and selectively preying on two species of mormyrids, the bulldog Marcusenius macrolepidotus and the churchill Petrocephalus catostoma. The predation on mormyrids may be related to prey size and abundance. In addition, catfish may sense the electrical discharge given off by the mormyrids when disturbed. The catfish feed intensively for a few months and build up body reserves and reproductive condition prior to spawning on shallow floodplains with the onset of the annual floods from Angola.
A comparative analysis of the feeding apparatus in pomacanthids, with special emphasis of oesophageal papillae inGenicanthus personatus
Authors: Howe J. C.
Published: April 2005

Of the pomacanthids examined in the present study (22 species; seven genera), onlyGenicanthus(eight species) had unique oesophageal papillae. The papillae of the masked angelfish,Genicanthus personatusare arranged in a radial fashion, finger‐like or polypoid in shape, very abundant, fill the lumen, and vary considerably in length (0·38–2.40 mm) and width (0·12–1·18 mm). The surface pores (2.8–45.2 μm in diameter) of each papilla are part of the gastric or mucus‐secreting oesophageal glands as determined by histological examination. Preliminary stomach content analyses revealed thatG personatusconsumes a variety of animal and plant material, including algae, copepods, diatoms, and eggs, but dominated in volume by plant material. The oesophageal papillae may constitute a morphological specialization of the digestive tract at the genus level. This may enableGenicanthusspp. to utilize and process a food source not readily available to other pomacanthid species. Additional studies are necessary to determine other ecological, behavioural, social, and morphological variables that separate this large and diverse group of fishes ecologically.
The effect of intragastric transmitters on feeding behaviour of Atlantic salmon, Salmo salar; parr during autumn
Authors: Armstrong J. D. , Rawlings C. E.
Published: April 2005

The proportion of Atlantic salmon parr (146 265 mm total length) that fed in laboratory tanks during autumn was 0% in fish filled with intragastric transmitters compared with 78 100% in controls.
Chromosome complement, C‐banding and Ag‐NOR in Gymnammodytes cicerelus (Ammodytidae, Perciformes)
Authors: Amores A. , Thode G. , Martinez G. , Giles V.
Published: April 2005

The karyotype of a sandlance species, Gymnammodytes cicerelus, comprises: seven meta‐centric, seven submetacentric and nine subtelocentric‐acrocentric pairs (2n=46, FN=74). The C‐bands appear in paracentromeric and telomeric areas of most chromosomes and the NOR regions, in two pairs of larger chromosomes. All these characteristics indicate that a large number of rearrangements seem to have been involved in the karyotype evolution of this species.
The distribution of Gobius cobitis in the British Isles
Authors: Wheeler Alwyne
Published: April 2005

Records of occuerence of Gobius cobitis on the British coast are listed from the literature and from extensive collecting in interfidal areas. In Britain the number of suitable habitats is reduced and the density of population is lower than in the Channel Islands and Brittany.
The ability of U.K. salmonid alevins to emerge through a sand layer
Authors: Crisp D. T.
Published: April 2005

Artificial redds were used to examine the effect of layers of sand at the gravel surface upon the emergence of trout and salmon. Alevins of both species can negotiate sand layers up to 8 cm thick.