bluuebunny/crossref_metadata_2025 huggingface dataset:
A note on growth and mortality of trout, Salmo trutta L., in afferent streams of Windermere
Authors: Craig J. F.
Published: January 2006

Trout were sampled in six afferent streams of Windermere during the spawning season. The main migration of adult trout into the streams took place during early November. Length‐weight relationships and scale‐fish length relationships are given. There was no significant difference in length for age or sex between cohorts within streams. Three groups of fish could be identified depending on whether the fish entered the lake at 1+, 2+, or 3+ years. The percentage number of the population entering the lake at each of these ages was 16, 70 and 14%, respectively. After the fish had migrated from the streams their growth in length fitted the von Bertalanffy growth model. Fish entering the lake at 1+ and 2+ years had similar A.95 values (6·31 and 6·97 years) as the latter grew slightly faster in the lake. Those entering the lake at 3+ years grew at a slower rate to the other two groups but achieved a longer ultimate length. Faster growing fish had higher instantaneous mortality rates. Twenty‐eight to 29% of the males remaining in the stream at 1+ years became sexually mature. Faster growing females became sexually mature earlier. Only those fish which entered the lake at 1+ years grew close, during their early years before sexual maturity, to the theoretical maximum given by Elliott's model.
Changes in activity levels of glutamate dehydrogenase and two transaminases of maternal liver during reproduction and after administration of oestradiol and progesterone in Zoarces viviparus (L.)
Authors: Korsgaard B.
Published: January 2006

The enzyme activity per unit liver wet weight, the specific activity and the total liver activity level of glutamate dehydrogenase (GDH) and two transaminases (GOT and GPT) were studied during vitellogenesis and pregnancy. A steady level of activity was observed during the short summer vitellogenesis and during early pregnancy. During mid‐term pregnancy in October the activity level significantly increased.

Administration of 5 and 100 μg oestradiol increased serum vitellogenin, total liver protein and the liver somatic index during late pregnancy. Oestradiol decreased activity and specific activity of the enzymes. However, expressing activity as total hepatic enzyme activity units in fish of standard body weight oestradiol had no effect.
The distribution of salmonids in upland streams in relation to depth and gradient
Authors: Kennedy G. J. A. , Strange C. D.
Published: January 2006

The distribution of various age classes of salmon and trout was assessed in upland streams by electrofishing. Water depths and site gradients were measured and correlated to fish densities. The fry of both species were significantly more abundant in shallow water; up to 75·3% of salmon fry and 72·2% of trout fry were captured in sites of mean depth < 20 cm. Older trout were found mainly in the deeper areas, with a maximum of 7·4% captured in sites < 20 cm mean depth. Yearling fish were found in all the depth‐ranges sampled, but with a tendency for higher numbers in mid‐range depths. There were similar correlations in the abundance of each age class with the actual areas of shallow, mid‐range and deep water habitat available within sites. Correlations of fish density with gradient indicated that trout were limited in their distribution to areas of lower flow, whereas salmon were not. Since depth and gradient were significantly negatively correlated, there was an apparent preference of trout for slightly deeper habitats than the equivalent year classes of salmon. The observed habitat segregation is discussed in terms of competition and selection.
Changes in the blood chemistry of rainbow trout, Salmo gairdneri Rich, in relation to dietary protein level, and an anabolic steroid hormone, ethylestrenol
Authors: Lone K. P. , Inch B. W. , Matty A. J.
Published: January 2006

The effect of feeding isocaloric test diets containing 35, 45 and 55% protein, with and without inclusion of the anabolic steroid hormone, ethylestrenol, was studied in rainbow trout, Salmo gairdneri, in relation to blood chemistry. The control (no hormone) and experimental diets (hormone‐supplemented), were fed for a total of 60 days, after which time all groups of fish were fed an identical commercial diet with no hormone for a further 30 days (withdrawal period). After 60 days, the body weights offish fed the 35 and 45% experimental diets were significantly greater than their respective controls, and after hormone withdrawal, increased growth was still apparent in the 35% experimental group.

No significant changes in serum amino acid nitrogen (AAN), protein, or glucose in relation to the dietary protein level, or inclusion of steroid, were observed after 30 days. Serum creatinine, however, increased with an increase in dietary protein, and was significantly higher in the 35% experimental group than the respective control. After 60 days, the most significant observation was the marked increase in serum glucose with an increase in dietary protein, but respective control and experimental values were not significantly different at this time. Following a 30‐day withdrawal period, serum AAN in the 55% experimental group was significantly higher than the control, whereas serum protein, creatinine, and glucose stabilized to similar concentrations in all groups. Over the 90‐day period of feeding, in both control and experimental groups, serum AAN and protein tended to increase, serum creatinine and glucose to decrease, whilst haematocrit remained constant. It is concluded that addition of ethylestrenol to trout diets has apparently little effect on serum metabolite concentrations and haematocrit, the most significant variations being related more to diet composition and duration of study.
Regenerative capacity of the spleen in a splenectomized fish, Channa punctatus Bloch, with related investigations into changes in peripheral blood and haematopoiesis
Authors: Mahajan C. L. , Dheer T. R.
Published: January 2006

The present investigation has provided evidence by a simultaneous study of the regenerating spleen, peripheral blood and the kidney of the haematopoietic tissue to establish the role of the spleen in the development of circulating blood cells in Channa (Ophiocephalus) punctatus Bloch. Regeneration of the spleen after eight to nine weeks of splenectomy was shown to be complete. Weekly observations a fortnight after splenectomy are recorded with reference to spleen morphology and weight, erythrocyte and differential leucocyte counts, haemoglobin content, haematocrit value and related red cell indices (MCV, MCH, MCHC). The results show that splenectomy leads to a macrocytic hypochromic anaemia and leucopenia, resulting in 25% reduction in haemoglobin content and a decrease in leucocyte numbers in five weeks following splenectomy. Thrombocytes and neutrophils show a relative (P < 0·01) increase. The leucopenia is caused by large and small lymphocytes, eosinophils and basophils whose number was reduced from 50% to 67%.
Exploitation of fish in the inner Kavirondo Gulf of Lake Victoria based on tag returns
Authors: Muller R. G. , Benda R. S. , Powell T. G.
Published: January 2006

Total mortality and exploitation rates of Bagrus docmac, Tilapia nilotica and T. variabilis in the inner Kavirondo Gulf of Lake Victoria were estimated. Fishing mortality comprised the greatest portion of the total mortality. Catch per recruit for B. docmac and T. nilotica indicated the exploitation levels were almost three times those yielding maximal catches. There has been an apparent shift in gear from beach seines and hooks to mosquito nets and smaller mesh gill nets.
An assessment of the performance of a resistivity fish counter
Authors: Dunkley D. A. , Shearer W. M.
Published: January 2006

Closed‐circuit television was used to provide a visual record of the events associated with the counts recorded by a resistivity fish counter. The fish seen were classified as‘ large’fish > 50 cm length and‘ small’fish of < 50 cm. Some of the‘ large‘ fish escaped detection by the counter, some‘ small’fish were counted and some counts were registered when nothing was seen. The sensitivity of the counter varied inversely with water conductivity which varied inversely with discharge.

Evidence was obtained suggesting that fish ascending a weir tend to swim closer to the bottom than do those descending. It was found that fish tended to move upstream just after sunset and downstream just before sunrise except when the water was turbid and when the fish were very close to spawning. The numbers of fish movements recorded increased during those periods when discharge was decreasing after a spate but when spawning activity was at its peak, increased activity occurred in the complete absence of any change in discharge. Instances of the same fish re‐crossing the counting zone several times were recorded and the simultaneous passage of more than one fish through the counting zone was observed.
Influence of water depth on dispersion of juvenile salmonids, Salmo salar L. and S. trutta L., in a Scottish stream
Authors: Egglishaw H. J. , Shackley P. E.
Published: January 2006

The dispersion of salmon and trout of 0 +, 1 + and 2 + age classes was examined by electrofishing 12 sections of a stream in Perthshire, Scotland at the end of the growing season in September to October in 1972 and 1976. In 1972 sections ranged in surface area from 21 to 122 m2 and had volumes of 5.0–17.3 m3 and when surveyed in 1976 surface areas were 15–106 m2 and volumes 2.1–6.7 m3. In 1976 widths and areas of sections were 63–87% of the values for 1972, depths were 39–68% and volumes 28–52% of the earlier values. These differences were due to 1976 being drier and warmer. In both years, all sections contained 0 + and 1 + age classes of salmon and trout and some sections contained 2 + age salmon and trout. The total density of fish in a section ranged from 1.9 to 3.9 m−2 in 1972 and from 3.72 to 6.08 m−2 in 1976. There was an inverse relationship, significant in 1972 only, between the density of 0 + salmon and that of 1 + trout in the different sections. Densities of both 0 + and 1 + salmon in the sections were inversely correlated, and those of 0 + and 1 + trout were directly correlated, with area of water deeper than 10 cm.
The feeding habits of 0+ stone loach, Noemacheilus bavbatulus (L.), and bullhead, Cottus gobio L.
Authors: Hyslop E. J.
Published: January 2006

The feeding habits of the 0+ year class of two of the most common small fish species in the River Ouzel, Milton Keynes, stone loach, Noernacheilus bnrhafulus (L.), and bullhead, Coftus gobio L., are assessed throughout the first growing season and compared. Despite similarities in the diets of the two species, differences in feeding behaviour and in morphology, especially in gape, may serve to reduce interspecific competition by partitioning of food resources.
The effect of single step and fluctuating temperature changes on the oxygen consumption of flounders, Platichthys flesus (L.): Lack of temperature adaptation
Authors: Duthie G. G. , Houlihan D. F.
Published: January 2006

The standard oxygen consumption of flounders, PLatichthys flesus, adapted for two months to 5 and 15° C was measured during single step and fluctuating temperature changes, A considerable recovery period from handling was required before standard levels were recorded, although no locomotor activity was evident. The Q10(adapt) value between 5 and 15° C was 2.0. Q10 (acute) values were higher. The responses of oxygen consumption to temperature rise conform to Type I11 metabolic compensation (Precht, 1958). No compensatory response was evident at lower temperatures. An alternative explanation of the results in terms ofexcitement metabolism is suggested.
An immunoinhibitory substance in the serum of laboratory held killifish, Fundulus heteroclitus L.
Authors: Miller N. W. , Tripp M. R.
Published: January 2006

Serum of the killifish, Fundulus heteroclitus, maintained under laboratory conditions for more than four weeks, contained a factor that depressed the immunocytoadherence response to SRBC. When serum was injected into immunocompetent fish 48 h prior to antigen stimulation it was effective; when injected simultaneously with the antigen there was no effect. Fractionation of the serum by ultracentrifugation suggests that the inhibitor is either low or very low density lipoprotein. Hypophysectomy decreased immune inhibition suggesting that the production of the inhibitor may be under the control of the pituitary.
Effect of feeding frequency on food intake and growth of Arctic charr, Salvelinus alpinus L.
Authors: Jobling M.
Published: January 2006

Social interactions and dominance hierarchy effects are important factors governing rates of growth of Arctic charr, Salvelinus alpinus L. The effects of hierarchy were increased as access to food became more restricted, i.e. feeding frequency was reduced, but these effects could not be attributed to direct competition for food since fish were fed to satiation at each feeding period. The results suggest that, whilst some fish on the restricted feeding regime were able to maintain good rates of growth, feeding by the majority of the fish was inhibited by the presence of larger individuals. Due to the importance of these hierarchy effects it was not possible to demonstrate physiological adaptations in fish allowed infrequent access to food.
The inshore fishes of Heard and McDonald Islands, Southern Indian Ocean
Authors: Williams R.
Published: January 2006

Nine species of fishes are recorded from the inshore waters of Heard and McDonald Islands. These records confirm the affinities of the fish fauna of these islands to that found at the nearest neighbouring islands, the Iles Kerguelen, 380 km to the north‐west on the same submarine plateau. Data on the stomach contents and gonad states of Notothenia coriiceps coriiceps, N. rossii rossii and Channichthys rhinoceratus show some differences from the same or related subspecies at other localities. Notothenia c. coriiceps shows more affinities in feeding and reproduction to N. c. neglecta from Terre Adelie, Antarctica, than to those from the Scotia Sea, in having a significant proportion of active benthic and benthoplank‐tonic invertebrates in its diet, in spawning in mid‐summer and in having a low relative gonad size. Channichthys rhinoceratus has a slightly more diverse diet and its spawning season is later than in the same species at Iles Kerguelen.
Calcaemic responses in the freshwater mud eel, Amphipnous cuchia, to vitamin D3 administration
Authors: Srivastav A. K.
Published: January 2006

Vitamin D3 (1000 iu 100 g−1 body wt) was administered to the freshwater mud eel, Amphipnous cuchia, which was maintained either in tap water or a calcium‐rich environment. Elevation of serum calcium levels was observed after the Vitamin D3 administration. This response was faster in the fishes which were maintained in a calcium rich environment after the vitamin D3 administration.
The seasonal cycle of condition in the pollan, Coregonus autumnalis pollan Thompson, of Lough Neagh, Northern Ireland
Authors: Wilson J. P. F. , Pitcher T. J.
Published: January 2006

The length–weight relationship for Lough Neagh pollan was log W= 3·2 log L–2·24. Covariance analysis indicated that there were no differences between the sexes, with maturity, or between years. While a seasonal cycle in relative condition was in phase with gonad development during late summer and autumn, changes in somatic condition presented a more complex pattern. Somatic condition increased in spring, as did the quantity and diversity of food consumed. Despite good conditions for feeding and growth, there was an autumn fall in somatic condition, caused by the diversion of energy to gonad growth.
Lytic and bactericidal properties of salmonid sera
Authors: Sakai D. K.
Published: January 2006

There are two types of haemolytic activity against heterologous red blood cells in the sera of fishes including salmonids: a specific antibody‐dependent complement‐mediate activity ‘CH50’ and a natural, non‐specific activity ‘SH50’. Sera of coho salmon, Oncorhynchus kisutch, masu salmon, O. masou, rainbow trout and steelhead trout, Salmo gairdneri, were assayed for CH50 and SH50 activities by incubation at 30°C for 60 min with goldfish red blood cells (GFRBC) sensitized with the rainbow trout antiGFRBC serum and unsensitized GFRBC for CH50 and SH50, respectively. SH50 activity was usually half that of CH50 in each serum. In healthy individuals, both CH50 and SH50 activities were confined to a narrow range specific for each species. While EDTA abolished both haemolytic activities, moieties of the activities remained in the presence of EGTA. Incubation with lipopolysaccharide and zymosan reduced both CH50 and SH50 activities. Fish serum possessed a natural, powerful bactericidal action, which for Aeromonas salmonicida was proportional to the level of SH50 activity. Changes in the SH50 activity were related to starvation and infectious diseases. The SH50 activity decreased as the diseases (furunculosis and vibriosis) progressed.
The deposition of otolith rings in Atlantic salmon, Salmo salar L., embryos
Authors: Geffen A. J.
Published: January 2006

Salmon embryos, age 48–81 days post‐fertilization (dpf), were incubated under three different temperature and photoperiod regimes to test the effects of incubation conditions on otolith ring deposition. Otolith rings were first observed at 50 dpf and certain developmental events were marked by distinct, heavy rings. The rate of ring deposition increased with increasing temperature and exposure to light, ranging from 0·50 to 2·33 rings per day. The possible relation to physiological activity as measured by oxygen consumption is discussed.
Pathogenic bacteria associated with cultured American eels, Anguilla rostrata Le Sueur
Authors: Davis J. F. , Hayasaka S. S.
Published: January 2006

American eels, Anguilla rostrata, obtained from an aquaculture facility in South Carolina were examined for diseases and bacterial pathogens were isolated and identified. During the first year of culture, only a small number of bacterial pathogens and diseases were detected in glass and elver stages. This observation appears to be associated with a natural immunity to disease and/or administering the antibacterial compound, nitrofurazone. There was also a positive correlation between the use of nitrofurazone and the isolation of nitrofurazone resistant strains of Aeromonas hydrophila. A higher incidence of bacterial pathogens and/or disease occurred during the process of culling and in older eels during warmer months. The primary aetiological agent of disease of cultured eels was A. hydrophila. Other potential pathogens isolated included A. salmonicida, Vibrio spp. and Pseudomonas spp.
Digestibility of an aquatic macrophyte by the cichlid Etroplus suratensis (Bloch) with observations on the relative merits of three indigenous components as markers and daily changes in protein digestibility
Authors: De Silva S. S. , Perera M. K.
Published: January 2006

The digestibility of the aquatic macrophyte Hydrilla verticellata by the Asian cichlid, Etroplus suratensis was estimated using three indigenous markers viz. hydrolysis resistant organic matter (HROM), crude fibre (CF) and hydrolysis resistant ash (HRA). In the fodder HROM showed the least variation and HRA the highest. The recovery of HRA in the faeces was always higher than 100% whereas HROM was the nearest to 100%. The total digestibility varied between 34·6% and 51·9%, and the digestibility estimates were higher when HRA was considered as the marker. The overall protein and lipid digestibility varied between 59·2%–70·9% and 65·0%–70·1 % respectively. It is suggested that HROM is a better reference marker in comparison CF and HRA. Daily variation in protein digestibility ranged from 51·2% to 81·8%.
Electrophoretic analysis of protein systems of Ctenopharyngodon idella (Val.), Hypophthalmichthys nobilis (Rich.) and their F1 triploid hybrid
Authors: Beck M. L. , Biggers C. J. , K.Dupree H.
Published: January 2006

Electrophoretic analysis was performed on eight protein systems (lactate dehydrogenase, liver esterases, superoxide dismutase, haemoglobin, isocitrate dehydrogenase, glucose‐6‐phosphate dehydrogenase, 6‐phosphogIuconate dehydrogenase, transferrin) in Ctenopharyngodon idella, Hypophthalmichthys nobilis, and their F1 triploid hybrid. The data demonstrated codominant Mendelian inheritance at individual loci for each protein system. Transferrin and superoxide dismutase were the only proteins found to be polymorphic in either parental species. Both parental alleles were present and functional at each enzyme locus examined in the F1 triploid hybrid.
The biology of bream, Abramis brama (L), and its natural hybrid with roach, Rutilus rutilus (L), in the River Exe
Authors: Cowx I. G.
Published: January 2006

Hybrids between bream, Abramis brama, and roach, Rutilus rutilus, occur in the lower reaches of the River Exe and were positively identified by their meristic features and shape of the pharyngeal bone. The growth of bream and hybrids was determined by back‐calculation from scales. Annual checks were laid down in early June. The mean length for age of female bream was significantly larger than that of males for fish 6 years of age and older. This divergence in growth rate was associated with the sexual maturation of the fish. Data for the sexes were combined and compared with the growth rate of hybrids and roach from the same region. Hybrid growth was similar to that of bream for the first 6 years of life but was intermediate between that of the two parent species in the older age groups. Some hybrids with developing gonads were found. A change in the diet of bream from planktonic feeding to a benthophagic habit with age was noted. Detritus, substrate and chironomid larvae formed the bulk of the diet of hybrids.
Records of seven juveniles of the whale shark, Rhiniodon typus
Authors: Wolfson F. H.
Published: January 2006

Seven juvenile whale sharks ranging from 550 to 930 mm in length are reported. Measurements of six are tabulated with remeasurements of the single known embryo. The mode of reproduction of this shark is again questioned, and the lack of records of sizes between 1 and almost 4 m is discussed.
Spontaneous occurrence of a synchronous hermaphrodite in the banded killifish,Fundulus diaphanus(Lesueur)
Authors: Porter D. A. , Fivizzani A. J.
Published: January 2006

An intersex specimen of the banded killifish,Fundulus diaphanus, was encountered during the analysis of the annual gametogenic cycle of this species. The simultaneous presence of mature spermatozoa and ova suggests that the potential for self‐fertilization existed in this fish. The spontaneous occurrence of this intersex individual, although a rare event, indicates the potential for the development of the synchronous hermaphroditic condition under natural environmental conditions in this normally gonochoristic species.
Consumption and growth of hybrid grass carp fed four vegetation diets and trout chow in circular tanks*
Authors: Shireman J. V. , Rottmann R. W. , Aldridge F. J.
Published: January 2006

Grass carp, Ctenopharyngodon idella, and hybrid grass carp (grass carp ♀× bighead carp ♀Aristichthys nobilis), were fed duckweed (Lemna sp.), hydrilla (Hydrilla verticillata), chara (Chara sp.), filamentous algae (Odogonium sp., Spirogyra sp.), and trout chow. Grass carp consumed all plants in greater amounts than hybrids. Grass carp grew best when fed hydrilla and trout chow and showed positive growth on all diets. Hybrids grew equal to grass carp when fed trout chow but did not grow on the vegetation diets. Low consumption rates of aquatic plants may indicate that hybrids are questionable as a plant biocontrol agent.
Influences of Ca and Mg ions on the egg survival of grey mullet, Mugil cephalus L.
Authors: Lee C.‐S. , Hu F.
Published: January 2006

Five kinds of artificial sea water with similar salinity, pH and osmolarity were prepared with different concentrations of calcium and magnesium ions. They were complete sea water, calcium‐free sea water, half calcium‐free sea water, magnesium‐free sea water and half magnesium‐free sea water. The fertilized eggs from induced spawnings of grey mullet Mugil cephalus, were transferred to these sea waters at two development stages, i.e. before the formation of 2‐blastomere stage and at the gastrula stage. Survivals of fertilized egg in different sea waters were checked after several hours incubation, the percentage survival was used as an index of the importance of calcium and magnesium to the embryonic development. The results showed that calcium is indispensable to the embryonic development of mullet egg. Magnesium, however, is not the necessary element in the incubation medium.
Relative growth of tissues at different somatic growth rates in rainbow trout Salmo gairdneri Richardson
Authors: Weatherley A. H. , Gill H. S.
Published: January 2006

Growth of tissues (heart, spleen, liver, gonad, gut, skin, visceral fat and carcase) in immature rainbow trout relative to growth of whole fish, was examined by means of allometric analysis (y=axb; Huxley, 1932) of wet and dry weights. Relative growth rates of tissues are compared in an initial sample of fingerlings (< 11·29 g), and in fish (> 11·29 g) growing rapidly (at 12°C ad libitum rations) and slowly (at 12°C, 4–5% rations, and 7°C ad libitum rations). In the fingerlings of the initial sample, the major tissues by weight (liver, gut, skin, visceral fat) increased relatively more rapidly than whole body weight (i.e. with positive allometry; b> 1·00), and carcase increased more slowly than body weight (b< 1·00). Above fingerling size, the reverse holds: tissues other than carcase (with exception of visceral fat) increased less rapidly than body weight (b < 1·00), and carcase more rapidly (b > 1·00). These principles hold for post‐fingerling, immature rainbow trout, regardless of growth rate differences of whole fish, and even in fish that also received bGH (bovine growth hormone). The characteristic b (slope) values in the allometry equations for the wet and dry weights of the various tissues tend to remain constant, despite whole fish growth rate differences and the effects of this constancy are to maintain approximate constancy of body proportional (%) wet and dry weights. It is emphasized however that the effect of b values only slightly > or < 1·00 can cause important changes in the proportional (%) weights of major tissues as fish continue to increase in size. In low (4–5%) rations fish (without bGH) the slope (b) value for gut is less than for fish on ad libitum rations with the result that gut proportional weight is significantly less among these fish. In fish on ad libitum rations at 7°C, the slope (b) value for skin is greater than for all other (12°C) groups; skin proportional weight for the 7°C group is therefore, significantly greater. The overall impression of relative growth in immature rainbow trout is of remarkable conservativeness of body proportional weights regardless of overall somatic growth rate.
Comparative physiology of three ecologically distinct freshwater fishes, Alestes nurse Ruppell, Synodontis schall Broch & Schneider and Tilapia zillii Gervais
Authors: Oni S. K. , Olayemi J. Y. , Adegboye J. D.
Published: January 2006

There are species differences in the physiological robustness of Alestes nurse, Synodontis schall and Tilapia zillii. The values of coefficient of condition in the Alestes sp., Synodontis sp. and Tilapia sp. were 1·74,2·48 and 3·6 respectively. Tilapia zillii was significantly more robust than any of the other two species (P<0–02).
Cry (preservation of spermatozoa of the whitefish Coregonus muksun Pallas
Authors: And J. Plironen , Hyvärinen H.
Published: January 2006

The cryopreservation methods for whitefish, Coregonus muksun, spermatozoa were studied using six different extenders with ‐40°C and ‐196°C as storing temperatures. In 1980, the spermatozoa of individual fishes were frozen in dry ice, in vials containing three different media based on glycerol as cryoprotectant. The pure glycerol media resulted in a 20% average rate of fertilization when samples were stored at — 40°C. The thawing procedure did not affect fertilization. In 1981, the sperm of individual fishes was frozen in pellets and stored in liquid nitrogen. Cryopreserved semen thawed in 0·119M NaHCO3 produced 29·6–87·7% eyed eggs. The differences were caused mainly by the type of extender. The highest rate of fertility was obtained using an extender consisting of 0·3 M glucose with 20% glycerol (87·7% eyed eggs; 98·6% eyed eggs when compared to the corresponding control). The same values, using the modified extender of Stoss (Stoss & Refstie, in press), were 38·7–82·4% and, on the average, 90% eyed eggs, respectively.
The biology of Carangidae (Teleostei) in Natal estuaries
Authors: Blaber S. J. M. , Cyrus D. P.
Published: January 2006

The occurrence and abundance of 17 species of Carangidae in Natal estuaries are described. The following six species are of significance in the estuarine community: Caranx ignobilis, C. melampygus, C. papuensis, C. sexfasciatus, Lichia amia and Scomberoides lysan. Only juveniles and subadults utilize estuaries. The time of recruitment, growth rates and feeding biology of the six species were investigated. Among the juveniles, C. ignobilis and C. sexfasciatus are mainly piscivorous on a variety of small estuarine fishes and estuarine dependent juveniles of marine species, while C. melampygus, C. papuensis and S. lysan filter feed on mysids and juvenile penaeids. Subadults of all species are piscivorous, although C. papuensis and S. lysan retain a suitable gill raker structure for filter feeding and a proportion of their diet consists of mysids and penaeids. The salinity and turbidity preferences of each species were investigated. All are euryhaline but C. melampygus, C. papuensis and 5. lysan are only found in clear water. It is suggested that the more widespread estuarine distribution of juvenile C. sexfasciatus and C. ignobilis may be related to their turbidity tolerances. The role of carangids in Natal estuaries is discussed in relation to their ecological significance in estuaries as predators and their degree of estuarine dependence.
Electron microscope studies of fish lymphocytes and thrombocytes
Authors: Blaxhall P. C.
Published: January 2006

No observable differences were noted in electron microscopic studies between brown trout, Salmo trutta L., and carp, Cyprinus carpio L., lymphocytes and thrombocytes separated by the Ficoll‐Paque technique. Transmission electron microscopy showed a similar ultra‐structure of fish lymphocytes to those of other reported species. Scanning electron microscopy showed that these lymphocytes studied all had a villus structure and the thrombocytes clearly showed their spindle‐shaped structure.
Contribution to the sexuality of a Hermaphroditic teleost, Serranus hepatus L.
Authors: Bruslé S.
Published: January 2006

Using histological and cytological criteria, it has been shown that in the ovotestis of Serranus hepatus, a synchronous hermaphrodite, the differentiation of the ovary is earlier than that of the testis. Primordial germ cells (PGC) exhibit the same ultrastructural features in the ovary and the testis. These cells migrate from the ovary to colonize the testicular anlage.
Composition of the milt of some teleost fishes
Authors: Piironen J. , Hyvärinen H.
Published: January 2006

The milt composition of six freshwater teleosts was studied, and the measured parameters showed clear specific differences between species. The highest spermatocrits and sperm densities were observed in perch, Perc afluviatilis, and burbot, Lota lota, and the lowest in rainbow trout, Salmo gairdneri, and whitefish, Coregonus lavaretus. Fructose concentrations in the seminal plasma were small compared to mammalian values. The glucose concentrations in the seminal plasma were five times higher than those of fructose, and higher in landlocked salmon and rainbow trout than in the other species. The citric acid concentration of all species except whitefish showed a significantly positive correlation to either spermatocrit or sperm density. The role of citric acid in the seminal plasma of fishes was also assumed to be important. The glycerol concentration in the seminal plasma was comparatively high, and highest in whitefish. This was assumed to be related to the high applicability value of glycerol as a cryoprotective agent for whitefish sperm. The high glycerol concentration was also assumed to be related to the lipolytic capacity of the testis in the studied species.
Chromosome karyotyping of fish using conventional and G‐banding methods
Authors: Blaxhall P. C.
Published: January 2006

The various methods by which chromosomes using lymphocytes, from Salmo trutta and Cyprinus carpio, can be collected, prepared and stained for analysis are described and evaluated.
The survival and growth of six species of freshwater fish, in tapwater and diluted and undiluted effluent from sewage percolating filters
Authors: Clark E. R. , Eraser J. A. L.
Published: January 2006

The survival and growth of rainbow trout,Salmo gairdneriRichardson, stone loach,Noe‐macheilus barbatulus(L), bullhead,Cottus gobio L., three‐spined stickleback,Gasterosteus aculeatusL., minnow,Phoxinus phoxinus(L), and roach,Rutilus rutilus(L), have been studied in water of three qualities—Birmingham tap water, 50% and 100% settled effluent from filter beds. Predicted toxicities (the sum of the proportions of the 48‐h LC50 of individual poisons to rainbow trout) were compared with the observed toxicity in 50% and 100% effluent. The behaviour of each species offish and the rates of mortality over an exposure period of 210 days are given together with cumulative growth rates (as a percentage of the initial weight). The Mean Percentage Change in Weight (MPW) and Mean Growth Rate (MGR) for each group offish was calculated from the initial mean wet weight and the mean weight of surviving fish at the end of the first and second intervals. The Mean Production Rate (MPR) over the experimental period was also calculated and was used as a holistic measure of the rate of total tissue elaboration or utilization, or loss in biomass due to mortality. The Condition Factor (K) also reported was calculated from the body weight and length and was used to examine (a) the effects of water quality, and (b) the timing and duration of maturation of the gonads. The latter was further used as a measure of the energy status of the fish.
Maturity classification and growth of capelin, Mallotus villosus villosus (M), oocytes
Authors: Forberg K. G.
Published: January 2006

Ovaries of female capelin, Mallotus villosus villosus (M), from the Barents Sea were sampled at various times of the year and material conserved for morphological examination. The maturity of female capelin, was assessed using low power microscopy for examination of whole oocytes. The diameters of oocytes were measured to give additional information regarding development, and to study the growth rate of the ripening oocytes. A maturity scale for use in the field is described based on the result of low power microscopy. A comparison is made between the‘old’and‘new’maturity scales, and the ease of use of the new scale has been tested.
Can Newfoundland landlocked salmon, Salmo salar L., adapt to sea water?
Authors: Burton M. P. , Idler D. R.
Published: January 2006

Landlocked salmon derived from a wild population of stunted ouananiche and bred in the laboratory showed signs of smoltification, but adaptation to sea water was slow and limited to 11% of the fish tested. Sea water survival was not related to initial size, within the range used, nor to sex, age (2 + years v. 3 + years) or spawning history.

Freshwater ouananiche had fewer gill chloride cells than anadromous smolts of similar size in fresh water. Anadromous smolts showed an increase in chloride cells after adaptation to sea water and those ouananiche which successfully adapted to sea water had a greatly increased number of gill chloride cells.
Seasonal changes in the pituitary‐ gonad axis of feral goldfish, Carassius auratus L., from Ontario, Canada
Authors: Munkittrick K. R. , Leatherland J. F.
Published: January 2006

Apparently healthy, feral goldfish, Carassius auratus L., were collected from a pond in Cambridge, Ontario from March until November 1981, and during April 1982. Based on histological examination, oocyte development was divided into five stages and the reproductive cycle into five periods. The origins of oogonia and the atresia process were examined. The gonadosomatic index (GSI) was found to be an accurate indicator of ovarian activity in the feral population. Based on the GSI, proportion of various oocyte stages and egg size, females older than 2 years appeared to spawn during two periods, May to June and late August; 2‐year‐old fish spawned in the first period. There was a reduction in the density, abundance and nuclear diameter of presumptive pituitary gonadotrops in early August, after the completion of ovarian development and before the completion of spawning.
Gonad differentiation and body growth in Anguilla anguilla L.
Authors: Colombo G. , Grandi G. , Rossi R.
Published: January 2006

Using histological sections, the gonads of samples of yellow and silver eels of two populations were examined. The populations were previously analysed for growth and sex ratio. The histological structures observed are similar to those described in previous publications for the European eel, Anguilla anguilla and to those indicated for the Pacific eel, A. japonica. Well differentiated gonads are present in the silver eels. In the yellow eels, ranging in age from 0 + to 2 + years and from a length of 20 cm to that at which they become silver, undif‐ferentiated and both sex gonads are found. Histological evidence is presented which suggests that the ovary, found even in young and small eels, is completely differentiated at a very early stage. The testis‐like gonad of the yellow eel is a more primitive, and possibly reversible, gonad which differentiates completely at the beginning of sexual maturation and the change to the silver phase.
Incidence of parasitic worms in stomachs of pelagic and demersal fish of the Rockall Trough, northeastern Atlantic Ocean
Authors: Mauchline J. , Gordon J. D. M.
Published: January 2006

The incidence of gyrocotyllid worms in chimaeroids and cestode larvae and nematodes in the stomachs of some 13 600 demersal and pelagic fish from the Rockall Trough, northeastern Atlantic is determined. The observations were made in conjunction with a detailed study of the diets of the fish which belonged to 117 species. No dietary sources of the infections could be identified with certainty. Pelagically caught fish, from between the surface and 2500 m depth, had no helminth infestation of their stomachs. Infestations of demersal fish were more pronounced between 1500 and 2900 m than between 500 and 1250 m depth.
Gastric evacuation rates for two foods in the black rockfish, Sebastes melanops Girard
Authors: Brodeur R. D.
Published: January 2006

The rates of gastric evacuation of two food types, squid and fish, were measured in the laboratory for adult black rockfish, Sebastes melanops, held nominally at 11°C. Linear, logarithmic and square root regression models were applied to analyse the data expressed as both wet and dry weight proportions of the original meal. The linear model provided the best fit for the wet weight relationship of squid. The dry weight of squid and both the wet and dry weight of fish were best described by a logarithmic model, or by a square root model when the regressions were’ forced’ through the original meal size. The instantaneous evacuation rates (≃ 6% h−1) and times to complete evacuation (≃ 76 h) were similar for all relations except those involving the wet weight of squid. The addition of the meal size as an independent variable improved the models in most cases whereas the addition of the weight of fish used in the experiments did not improve the model in any instance.
Note on nutritional dynamics of Gymnotus carapo (L.) from the Lobo Reservoir, Sâo Paulo State, Brazil
Authors: Barbieri G. , Barbieri M. C.
Published: January 2006

The nutritional dynamics of Gymnotus carapo were studied in 3253 male and female specimens collected in the Lobo Reservoir over a period of 18 consecutive months (September 1978 to February 1980). Analysis of the repletion stages, of mean repletion grade and index showed that the fishes exhibited better feeding conditions after the reproductive season. The condition factor was determined and shown to be influenced by the ovarian weight at the time of reproduction, but was little influenced by testis weight. The effect of stomach weight is negligible for both males and females.
The ontogeny of the retina and optic tectum inAequidens portalegrensis(Hensel)
Authors: Munro A. D.
Published: January 2006

External features of the development of fry of the brown acara,Aequidens portalegrensis, are described. There is evidence that thyroxine is a melanophore‐concentrating hormone early in larval life. There is also evidence that adrenal corticosteroids are of importance in the growth and development of fry. The development of the retina is described. All structural components of the adult retina are present by 7 days after fertilization, when rods and the capacity for visual accommodation appear. Double cones first appear a day previously; circumstantial evidence suggests that they originate from the incomplete fission of single cones. The development of the optic tectum is similar to amphibians. The pace of tectal differentiation is slower than that of the retina. When the fry become free‐swimming (+ 6 days), the wall of the tectum comprises a thickstratum periventricularewith, external to this, a thinstratum corticalis.Thestratum corticalissubsequently increases in thickness, concomitant with the migration of individual neurones from thestratum periventriculare.The distinct stratification of the adult optic tectum is not apparent until shortly after the transition to the juvenile phase (+24 days).
Salinity tolerance of the guppy, Poecilia reticulata Peters
Authors: Chervinski J.
Published: January 2006

Experiments were conducted to determine the adaptability of the guppy to various salt concentrations. The guppy, Poecilia reticulata, (total length 11–40 mm) were subjected to abrupt and gradual changes from fresh water (salinity=0.1%) to various salinities (%). No mortality occurred when the fish were transferred from fresh water to 50% sea water (19.5%). Through gradual adaptation from 50% sea water to 80% of the fish were able to tolerate 100% (39%) sea water for 7 days. After a 7 day stay in sea water, fish were readapted to fresh water during a 3 h period. Through gradual adaptation fish were also able to tolerate salinities ranging from 39.0% (100% sea water) to 58.5%. After a 30 day stay in 150% sea water (58.5%), fish were readapted to fresh water over a 5 h period. The results indicate that they were well able to tolerate the abrupt change from 100 or 150% sea water to fresh water. Females that stayed in 150% sea water (58.5%) for 30 days had embryos in their gonads.
The reproductive biology of Gerres in Natal estuaries
Authors: Cyrus D. P. , Blaber S. J. M.
Published: January 2006

An investigation of the reproductive state and gonad development of Gerreidae in Natal showed that the fry of Gerres rappi, G. acinaces and G. filamentosus entered estuaries at 10 mm (s.l.). They stayed in the estuary until attainment of maturity, which was between 70 and 110 mm according to species. Gonad activity was initiated in estuaries but all females left before their eggs were ripe. Testes ripened while the fish were still in the estuary but no ripe running individuals were found. Since few large and no spent individuals occurred in the estuaries sampled, it appears that most fish do not return from the sea. Sequence of oocyte maturation and testes development were determined histologically. The estuarine area may be of importance to the fry as a safe nursery ground and to maturing individuals as an environment in which gonad maturity is reached for the first time.
The growth and mortality of larval herring, Clupea harengus L., in the River Blackwater Estuary, 1978–1980
Authors: Henderson P. A. , Whitehouse J. W. , Cartwright G. H.
Published: January 2006

Herring larvae were sampled in the Outer Thames Estuary and the River Blackwater Estuary in the springs of 1978, 1979 and 1980. Data were collected on larval stage, yolk sac and post yolk sac, larval length and total larval numbers. Newly hatched larvae were 6.8±0.5 mm long and the growth rate of yolk sac larvae was estimated at 0.18 mm d−1 (L= 6.8±0.186t). The growth rate of post yolk sac larvae increased to 0.43mm d−1 (L= 11±48.0±43t). Mortality estimates, derived from total numbers in the summed estuary segments, varied between the years and the cohorts within the year. In 1979 the mortality rates were 0.061 d−1 and 0.074 d−1 for the two cohorts. The mean size of the larval population was estimated at 2.48×109 (1.63–3.77 × 109) which agreed well with population size estimates from egg laying and from catch in numbers at age together with estimated fishing mortality rates.
Seasonal prevalence of the microsporidan, Glugea stephani (Hagenmuller), in winter flounder, Pseudopleuronectes americanus (Walbaum), from the New York‐New Jersey Lower Bay Complex
Authors: Takvorian P. M. , Cali A.
Published: January 2006

During a 32 month period 26 monthly collections of winter flounder were conducted from various locations in the New York‐New Jersey Lower Bay Complex. A total of 3125 flounder were captured and examined for the presence of the microsporidan, Glugea stephani. Of the total number of fish collected, 260 (8.32%) were infected with the protozoan. At least one G. stephani infected flounder was captured and identified each month, which indicates that the infection is present on a year‐round basis. The monthly infection prevalence ranged from 0.63 to 25%. Increased parasitism corresponded with elevated water temperatures. Fish size was not a statistically significant factor for infection.
The uptake of the anaesthetic benzocaine hydrochloride by the gills and the skin of three freshwater fish species
Authors: Ferreira J. T. , Schoonbee H. J. , Smit G. L.
Published: January 2006

The uptake of benzocaine hydrochloride and neutralized benzocaine hydrochloride by the skin and the gills of Cyprinus carpio, Oreochromis mossambicus and Salmo gairdneri were studied. The differences observed can mainly be ascribed to degree of ionization and the lipid solubility of the anaesthetic.
Ectoparasite induced changes in epidermal mucification of the brown trout, Salmo trutta L.
Authors: Pottinger T. G. , Pickering A. D. , Blackstock N.
Published: January 2006

The apparent effects of environmental factors on skin structure in hatchery‐reared brown trout are shown to be mediated by the influence of these factors on the skin parasite population. The presence of ectoparasites promotes a reduction in the concentration of epidermal mucus‐secreting goblet cells, the magnitude of which is related to the intensity of infection.
Effects of different acids on the bluegill sunfish, Lepomis macrochirus Rafinesque
Authors: Ellgaard E. G. , Gilmore J. Y.
Published: January 2006

The concentration of hydrogen ions which caused 50% mortality of bluegill in 96 h (96 h LC50) was between pH 3.5 and 3.0 for four acids; sulphuric, nitric, phosphoric and hydrochloric. Therefore, it appears that any contribution by the anions of these acids to fish toxicity is similar. This suggests that the quantity rather than the quality of acids is the primary factor in fish toxicity brought about by acid precipitation.

At sublethal concentrations of acids, bluegill became hypoactive with respect to their swimming behaviour.