bluuebunny/crossref_metadata_2025 huggingface dataset:
Reproduction, growth and mortality of the common bully, Gobiomorphus cotidianus McDowall, in a eutrophic New Zealand lake
Authors: Stephens R. T. T.
Published: January 2006

Gobiomorphus cotidianus in Lake Waahi, North Island, New Zealand, (37° 34'S; 175° 08'E) spawned continuously between July 1976 and March 1977. Length frequency data indicated that two, and briefly, three year classes, were present, each made up of three groups which were the progeny from successive peaks in spawning activity. Scale examination revealed checks to growth associated with spawning and stressful midsummer conditions. These and length frequency data were used in growth estimates which indicated that bullies reached 3·5‐4·0 cm after their first year, 5‐6 cm after their second but did not survive a third year. Mortality was associated with spawning and midsummer stress.
Effects of egg quality on normal fertilization and early development of the cod, Gadus morhua L
Authors: Kjørsvik E. , Lønning S.
Published: January 2006

Normal cod eggs respond to insemination by a rapid cortical reaction followed by an increase in total osmolarity and a small increase in egg diameter. The chorion becomes harder, but this is a slower process reaching its maximum strength after c. 24 h. Bad eggs are characterized by a slower or incomplete cortical reaction, resulting in a slower rise in osmolarity and a softer chorion. Bad eggs rapidly lose their capacity for fertilization. In unfertilized eggs in sea water, no cortical reaction is observed. There is, however, a rise in total osmolarity and a hardening of the chorion.
Growth and maturation of roker Raja clavata L. in the Solway Firth
Authors: Nottage A. S. , Perkins E. J.
Published: January 2006

Two hundred and seventy‐one Raja clavata taken by otter trawl from the Solway Firth were examined for size, sex and state of maturity. Size relationships for both sexes were similar. Total length and disc width were linearly related as were disc width with wing width. Males and females appear to mature at 42 and 45 cm disc width respectively. The Solway population is heavily exploited by an unrestricted commercial fishery and a considerable proportion (48·6%) of the presently retained catch is immature. It is suggested that fishing pressure has brought about a reduction in the size at which female fish mature.
Multivariate analysis of the phenotypic relationships of the species of Paragalaxias and Galaxias (Pisces: Galaxiidae) in Tasmania
Authors: Johnson C. R. , Ratkowsky D. A. , White R. W. G.
Published: January 2006

The 10 species of Galaxias in Tasmania, G. olidus from mainland Australia and the four species of Paragalaxias were studied using principal co‐ordinates analysis (PCOA) and cluster analysis of a standardized Euclidean distance matrix based upon variate means, and by canonical variate analysis (CVA) conducted as a stepwise multiple discriminant analysis. Thirty‐five variables comprising 30 morphometric and five meristic characters were analysed. The meristic characters were not included in the CVA. Excellent separation of the two genera was achieved in all analyses. The multivariate analyses were repeated on each genus separately to see if relationships suggested by the overall analysis remain stable. When the resultant groupings of species are compared for the different analyses, no consistent, distinct groupings of species within each genus are apparent. Despite the absence of distinct groupings, some trends in the affinities of some species are evident. In particular, species affinities as indicated by the CVA are more consistent with established opinions of species relationships. From the results of the study it is suggested that caution be exercised in the application of multivariate statistical analyses of morphological data to ichthyological systematics and phylogeny.
Identification, habitats and seasonal occurrence of juvenile whiting (Sillaginidae) in Moreton Bay, Queensland
Authors: Weng H. T.
Published: January 2006

Three sympatric whiting species‐(Sillaginidae)—sand whiting, Sillago ciliata, golden‐lined whiting, Sillago analis, and trumpeter whiting, Sillago maculata, are common in Moreton Bay, Queensland. Their identification, habitats and seasonal occurrence of juveniles are studied. A key to identification of these species is provided. Juveniles of the three species inhabit shallow shores including lower sections of creeks and rivers; but 5. ciliata prefer sandy substrates with less than 1 m depth and S. analis favour muddy‐sand substrates also with less than 1 m depth, while 5. maculata juveniles stay in muddy‐sand to muddy substrates at 1–3 m depth. Sillago analis juveniles appear at the waters' edge from October to May each year.
Diplostomiasis in the sand smelt, Atherina presbyter (Cuvier), population at Fawley Power Station
Authors: Bamber R. N. , Glover R. , Henderson P. A. , Turnpenny A. W. H.
Published: January 2006

Diplostomiasis, or black spot, is a disease of teleost fish, which results from the encystment of metacercarial larvae of digenean trematodes in the skin of the fish. This parasite occurs on sand smelt, Atherina presbyter, and pout, Trisopterus luscus, at Fawley. Since the debilitating effects of disease or parasitism may be a factor influencing fish impingement, the incidence of black spot in the Fawley sand smelt population has been studied. Fish 3 months old can be infected, and an average of 9% of the population up to 2 years old is infected. There is a rapid size‐correlated rise in infection in 2 + fish, associated with their migratory habit. The metacercarial morphology has been examined, and it is tentatively identified as a species of Neodiplostomum. There is a greater settlement of metacercaria on the fins and the eye of the sand smelt than on the scaled parts of the body. No seasonality or change in levels of infection over the years 1977 to 1981 were found. The incidence of the parasite has no effect on the impingement of sand smelt at Fawley; the reasons for this are discussed. Models of the changing rate of infection with migration imply that the population associated with the power station is less infected than surrounding natural populations. The infection rates of diplostomiasis in separate populations of host fish may prove useful in distinguishing the origins of individuals in a mixed impingement on the power station screens.
The influence of water velocity on the downstream movement of alevins and fry of brown trout, Salmo trutta L.
Authors: Ottaway E. M. , Forrest D. R.
Published: January 2006

Trout eggs were planted in four experimental stream channels, each channel being run at a different but constant discharge. Survival of the eggs to hatching was low and apparently unrelated to surface water velocity. However, movement of young trout out of channels was affected by water velocity, the higher the velocity the greater the proportion of trout that were lost. Virtually all fry moved out of a channel with a mean surface water velocity of 0.73 m s−1. The rate of loss was not constant over the experiment but increased as the young trout entered the free‐feeding stage. At the end of the experiment loss of fry, after abrupt increases in discharge, was demonstrated in the lower velocity channels.
A note recording the occurrence of hermaphroditic smelt, Osmerus eperlanus (L.) from the river Thames, England
Authors: Hutchinson P.
Published: January 2006

Of a sample of 703 smelt, Osmerus eperlunus, from the estuary of the river Thames, 2.6% were identified as being synchronous hermaphrodites. The fish are compared with previously reported hermaphroditic smelt.
The morphology and histology of the pineal organ in roach, Rutilus rutilus (L.)
Authors: Jafri S. I. H. , Ensor D. M.
Published: January 2006

The pineal organ in the roach, Rutilus rutilus (L.), is covered by a semi‐transparent area, the pineal window. Beneath this the pineal is attached to a long robust stalk, lying just under the parietal bone. The pineal is attached to the brain through the dorsal sac. Three cell types have been identified histologically. These are the sensory cells, supporting cells and the ganglia cells. The inner segment of the sensory cells respond to PAS and AF staining, while the remaining cells respond to Orange G, LG, or Acid Fuchsin. The evidence suggests that the roach pineal may have a dual photosensory and glandular function.
A histopathological report of some epidermal anomalies of Dover sole, Solea solea L., and other flatfish species in coastal waters off south‐east England
Authors: Bucke D. , Feist S. W. , Norton M. G. , Rolfe M. S.
Published: January 2006

The gross pathological and histological changes of typical examples of epidermal anomalies of Dover sole, Solea solea L., and other flatfish from the sewage dumping areas of the Thames Estuary and two ‘control’ areas are described. Five per cent of flatfish showed anomalies including trawl damage abrasions, fin‐rot, ulcers, nodules and tumours, lymphocystis and skeletal anomalies. Many of the anomalies suggested a traumatic aetiology and were often chronic. There was no significant difference in disease incidence between the areas sampled, except more evidence of lymphocystis in one of the control areas.
Protein, lipid, water and caloric contents of immature rainbow trout, Salmo gairdneri Richardson, growing at different rates
Authors: Weatherley A. H. , Gill H. S.
Published: January 2006

Protein, lipid, water and caloric contents of immature rainbow trout, relative to size of whole fish, growing at different rates were examined by use of allometric analysis (y = axb, Huxley, 1932). Fish grew at different rates as a result of differences in ration size (satiation, or 4–5% of dry body weight), temperature (7 and 12°C) and bGH (bovine growth hormone) administration. In fingerlings, protein, lipid and caloric contents tended to increase (v. body weight) as a percentage of body composition, whereas above fingerling size, protein decreased while lipid and caloric contents still increased. These trends occurred regardless of growth rate differences. The correlations between protein, lipid, caloric contents and body weight were high so reliable estimates of body components can be made from body weight for all experimental treatments. At satiation rations (7 and 12°C), there were no significant differences in protein content, but lipid and caloric contents were significantly higher in control fish. At low rations, protein and caloric contents were lower than those at satiation rations and lipid was lower than in the control group. On a dry weight basis, in uninjected fish at 12°C, ration size did not influence the percentage composition (protein and lipid) but the low ration group had lower energy values per unit of body dry weight. At low temperature (7°C satiation), fish had lower lipid and higher protein content (dry weight basis) than their controls (12°C satiation), thereby resembling bGH injected fish at satiation rations. Values of caloric content estimated from protein and lipid values by use of standard conversion factors differed sufficiently from caloric values directly determined by bomb calorimetry to suggest that caloric values of lipids may change during growth. The increase in body caloric content during growth apparently results mainly from an increase in the percentage of lipid. The similarity of body composition between different growth rate groups implied a tendency for conservation of relative proportions of components such that body composition can be approximated from body weight. Equations were also given to describe the relationship between water content and body constituents, and the relationship between condition factor (K) and both the body dry weight and lipid content.
A short review and critique of methodology used in fish growth and nutrition studies
Authors: Jobling M.
Published: January 2006

A number of the techniques commonly employed in fish growth and nutrition studies are evaluated and limitations imposed by their use are indicated. Total and digestible energy values of dietary formulations should be measured directly and the use of caloric conversion coefficients and assumed digestibility values may lead to serious error. There is considerable misunderstanding relating to the term metabolizable energy and metabolizable energy has been estimated in a number of ways, all of which are unreliable. In view of this, it is suggested that there is a good case to be made for ceasing to use the term.
The biology of Boyer's sand smelt, Atherina boyeri Risso in the Bardawil Lagoon on the Mediterranean coast of Sinai
Authors: Gon O. , Ben‐Tuvia A.
Published: January 2006

The present study describes some aspects of the life history of Boyer's sand smelt Atherina boyeri in the hypersaline Bardawil Lagoon on the Mediterranean coast of the Sinai peninsula, Egypt. Monthly samples were collected with a small‐mesh experimental beach‐seine during the years 1973–1974. Age determinations were based on otoliths readings and length frequency distributions which indicate that the Bardawil Lagoon population consists mostly of 0‐age group. The largest recorded fish was 63 mm in standard length (S.L.). Length‐weight relationship has been calculated as: W= 13.7 × 10−6×L2.93 where W= weight (g) and L=S.L. (mm). Atherina boyeri mature at the length of 34 mm. Spawning takes place from March to September. The average number of eggs in the ovary of a ripe female at the beginning of the spawning season was found to be 522. Females of all sizes were more numerous than males. In immature fish, less than 34 mm long, females constituted 53% of the population. In larger fish the number of females was higher; in fish over 34 mm long females constituted 64% and in fish over 51 mm—96%. Atherina boyeri in the Bardawil Lagoon feeds on both zoobenthos and zooplankton, mainly amphipods and copepods. Polychaetes, mysidaceans, insects and fish were also represented. Atherina boyeri is the host of endoparasitic Trematoda, Acanthocephala and Nematoda. The examined fish were found to have metacercaria in their mesenteries and liver.
Factors influencing the uptake of 14C‐labelled Vibrio anguillarum vaccine in direct immersion experiments with rainbow trout, Salmo gairdneri Richardson
Authors: Tatner M. F. , Horne M. T.
Published: January 2006

The factors influencing the uptake of a 14C‐labelled Vibrio anguillarum vaccine in direct immersion experiments with rainbow trout, Salmo gairdneri were studied. Immersion times of longer than 10 s did not increase vaccine uptake. A pre‐immersion dip in a hyperosmotic solution had no effect on uptake, even at lower vaccine bath concentrations. It appeared that the head end of the fish was implicated in uptake. Vaccine uptake decreased at lower temperatures, whereas the use of an adjuvanted vaccine and a soluble vaccine preparation led to increased uptake. Larger fish took up more vaccine.
Observations on the dietary habits of wild and stocked brown trout, Salmo trutta L., in Irish lakes
Authors: O'Grady M. F.
Published: January 2006

The dietary habits and feeding rates of wild and stocked brown trout were compared for populations in a number of Irish lakes. Wild trout and stocked fish, which had been present in a fishery for 12 months or longer, tend to feed on the same dietary items at similar rates. Stocked fish in their immediate post‐planting period (1–14 days) ate less than both the wild trout and established planted fish. In some instances recently stocked fish appear to have a preference for surface food items. They also consumed stones and detritic material. Data indicate that stocked fish adopted a natural diet in less than 5 months. Results are discussed in relation to angling crops of wild and stocked fish and the comparative success of autumn and spring plantings of salmonids.
Respiration of the carp, Cyprinus carpio L., at 10 and 20° C and the effects of hypoxia
Authors: Hughes G. M. , Albers C. , Muster D. , Götz K. H.
Published: January 2006

Oxygen consumption of carp acclimated at 10 and 20° C has been measured under routine conditions. Some complications and precautions necessary in continuous flow respirometry are discussed. Routine Vo2 at different levels of hypoxia have been determined. Individual variation leads to scatter in the data and different methods of plotting the relationship between Vo2 and Po2 are proposed; attention is drawn to differences between inlet (or ambient) Po2 and inspired Po2. Using certain criteria a ‘critical’ oxygen tension of about 95 mm Hg was found at 20° C; Q10 values are about 2 at normoxia and some suggestions of an increase near to the critical oxygen tension were found. Blood samples from the dorsal aorta showed rising Pa,o2 of 16 mm Hg which increased to 70–80 mm Hg when Pinsp was 90 and they then fall as the inspired oxygen is lowered. During periods of deep hypoxia (25 mm Hg) blood lactate concentration increases steadily and indicates an increasing dependence on anaerobic mechanisms.
Quantitative protein requirements of Arctic charr, Salvelinus alpinus (L)
Authors: Jobling M. , Wandsvik A.
Published: January 2006

Arctic charr, Salvelinus alpinus, require diets with protein energy (PE): total energy (TE) ratios of at least 0.35 in order to maintain good rates of growth. The protein requirement is, therefore, similar to that of rainbow trout, Salmo gairdneri. Protein retention efficiency (PPV) declined as the protein content of the diet was increased, the relationship being described by the equation:

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It is suggested that charr will maintain good rates of growth if fed on diets used for commercial culture of rainbow trout and special formulations for charr should not be necessary.
The biology of solenette, Buglossidium luteum (Risso), in the Solway Firth
Authors: Nottage A. S. , Perkins E. J.
Published: January 2006

The population of solenette, Buglossidium luteum, in the Solway Firth was studied from November 1977 until January 1979. The fish live in mobile, highly aggregated groupings, on sandy bottoms, in the outer Firth. A general offshore movement occurs in winter with a limited incursion of juveniles into the inner Solway in summer. Most growth occurs in the first few years of life and a length of 130 mm is attained. Longevity is 10 years. Females grow larger than males, but both sexes mature in their third year. Spawning starts in March/April, is most active in May/June and ends in August. Food intake is markedly reduced in winter. Small Crustacea, bivalve molluscs and polychaete worms form year‐round components of a varied diet. Juvenile forms, especially shrimp and fish are readily taken when available.
Parasitic infestations of Pseudotolithus spp. off the coast of Lagos, Nigeria
Authors: Anyanwu A. O.
Published: January 2006

A nematode parasite Philometra translucida Walton (1927) was found in the ovaries of Pseudotolithus senegalensis Cuvier & Valenciennes (1833), P. typus Bleaker (1863) and P. elongatus Bowditch (1863), the most abundant and commercial sciaenid species in the Nigerian inshore waters. The parasite measured 56·0–59·0 cm in length. It occupied one‐third to two‐thirds of the mesenteries of the matured ovaries in severe cases of infection. The incidence of infestation, highest during peak spawning, was 10·0% in P. senegalensis, 12·0% in P. typus and 20·0% in P. elongatus. Another nematode parasite Coniracaecum sp. Ralliet & Henry (1912) was observed in the ovaries of two specimens of P. typus.
Factors affecting lymphocyte culture for chromosome studies
Authors: Blaxhall P. C.
Published: January 2006

Factors affecting the transformation of brown trout, Salmo trutta L., and carp, Cyprinus carpio L., lymphocytes in culture for subsequent karyotyping are examined. Optimum conditions for mitosis are established in respect of medium, mitogen, atmosphere, buffering system and serum.
Haematological and haematopoietic studies in pyridoxine deficient fish, Channa punctatus Bloch
Authors: Agrawal N. K. , Mahajan C. L.
Published: January 2006

Pyridoxine deficiency was induced in a population of Channa punctatus. The deficiency effects were increased by adding 4‐deoxypyridoxine as an antagonist. Haematological and haematopoietic changes were studied. The significant changes in peripheral blood appeared after 150 days in the antagonist treated group and 180 days in the group on the deficient diet. After 240 days when morphological changes and an increased mortality also appeared, the changes in RBC and related values (haemoglobin, haematocrit, MCV, MCH & MCHC) were highly significant and indicated hypochromic microcytic anaemia; this was accompanied by leukopenia. The haematopoietic studies revealed significant increase in the earlier stages of erythrocytic development (basophilic erythroblasts and polychromatophilic eryth‐roblasts) with a simultaneous decrease in the later stages (young and mature reticulocytes). A series of pathological disorders in the various developing cells were recorded in the imprints of haematopoietic tissues. The pyridoxine specificity of these changes were confirmed by remedial treatment for a month.
The acute lethal toxicity of mixtures of cyanide and ammonia to smolts of salmon, Salmo salar L. at low concentrations of dissolved oxygen
Authors: Alabaster J. S. , Shurben D. G. , Mallett M. J.
Published: January 2006

The survival of Atlantic salmon smolts on exposure to constant concentrations of cyanide and ammonia, singly and together, has been measured under laboratory conditions at a concentration of 5 mgl‐1 of carbon dioxide. The 24‐h LC50 values of cyanide and of un‐ionised ammonia, in fresh water, were 0·073 mg HCN l‐1 and 0·20 mg NH3l‐1 respectively at a concentration of dissolved oxygen of 10 mg l‐1, and 0·024 mg HCN l‐1 and 0·08 mgNH3l‐1 respectively at a concentration of dissolved oxygen of 3·5 mg l‐1. In 30% sea water the corresponding values were similar for cyanide but markedly higher for ammonioa. In 80% sea water the values were intermediate between those of fresh water and 30% sea water. Prior acclimation of the fish to the respective toxicant increased the resistance of the fish only slightly to cyanide, but with ammonia the 24‐h LC50 was increased between 1·4 and 2‐fold after acclimation for 1–3 days to between 0·2 and 0·5 of the 24‐h LC50 value. Mixtures of cyanide and ammonia were between 0·6 and 1·25 times as toxic as expected, assuming simple additivity of toxicity.
Report of a large fish kill resulting from natural acid water conditions in Australia
Authors: Brown T. E. , Morley A. W. , Sanderson N. T. , Tait R. D.
Published: January 2006

A large natural fish kill which resulted in the deaths of a total of more than 3400 fish comprising eight different species occurred in a freshwater billabong (lagoon or small permanent waterbody) on the Magela Creek in the subtropical Northern Territory of Australia in January, 1980. The fish deaths were assessed to be the result of a combination of natural acid water runoff into the billabong and resultant elevated aquatic biotoxic aluminium levels. Details of water quality changes which occurred during the event and analytical data for the fish killed are provided, together with some explanation of the sequences of occurrence of the fish kill.
Studies on the chemical nature of feeding stimulants for the juvenile European eel, Anguilla anguilla (L.)
Authors: Mackie A. M. , Mitchell A. I.
Published: January 2006

A study has been made of the chemical nature of feeding stimulants for juvenile European eels, Anguilla anguilla. Mixtures of L‐amino acids were stimulatory, while neither the corresponding. D‐amino acids nor the non‐amino acid components were effective. Synergistic effects were observed both between L‐amino acids and between L‐amino acids and non‐amino acid constituents. The results are discussed in the context of results obtained from electrophysiological and behavioural studies with other species.
A field investigation of water quality, fish and invertebrates in the Mawddach river system, Wales
Authors: Howells E. J. , Howells M. E. , Alabaster J. S.
Published: January 2006

A 3‐year study was made of the soft, acid waters of the Rivers Mawddach, Wen and Gain, which contained copper, zinc and iron from natural outcrops and abandoned mines. Invertebrates, typical of acid to neutral streams, were present but there was no pattern in overall numbers or in biomass between stations. However, the abundance and distribution of Ephemeroptera were related to pH and water hardness although not to copper and zinc. Brown trout, Salmo trutta, were present and there was little difference in rate of growth between stations, whereas biomass and population density varied considerably between stations, being related to water quality such that, where annual median and 95‐percentile of the summed proportions (p) of the threshold LC50 concentrations of copper and zinc to rainbow trout, S. gairdneri were 0·3 and 0·7 respectively, biomass was half that in the absence of the metals and, where they were 0·6 and 1·3 respectively, no fish would be expected to occur. Low pH was an additional adverse factor at some locations. Salmon, S. salar, failed to populate a tributary where the sum of the p tLC50 values of copper and zinc was 0·45. High aqueous concentrations of copper resulted in elevated concentrations of copper in the liver of trout, especially in older fish, but not in the muscle. Concentrations of zinc in fish liver and muscle were low despite high ambient concentrations.
Comparison of nuclear DNA content of rodlet cells and erythrocytes in some freshwater teleosts
Authors: Barber D. L. , Westermann J. E. Mills
Published: January 2006

DNA of rodlet cells and erythrocytes from three species of freshwater teleosts, Semotilus atromaculatus atromaculatus, Catostomus commersoni and Cyprinus carpio, was stained with the Feulgen reaction and examined by microdensitometry. Rodlet cells showed nuclear DNA content significantly different from erythrocytes of the same species, but the difference was less than a factor of C, assuming that erythrocytes reflect the normal 2C genome of somatic cells. In two species, S. atromaculatus and C. carpio, the rodlet cell nuclei contained less DNA than the erythrocytes; in C. commersoni they contained more. The identity of the rodlet cell is unknown; the results of these experiments lead to the rejection of the hypothesis that rodlet cells and erythrocytes of a species have the same DNA content, i.e. that the rodlet cell is a normal somatic component of fish tissue.
Erythrocyte measurements of diploid and triploid Ctenopharyngodon idella×Hypophthalmichthys nobilis hybrids
Authors: Beck M. L. , Biggers C. J.
Published: January 2006

Diploid and triploid hybrids resulted when grass carp, Ctenopharyngodon idella, and big‐head carp, Hypophthalmichthys nobilis, were experimentally hybridized. Erythrocyte size can be used to distinguish C. idella×H. nobilis hybrids of different ploidies.
Changes in serum thyroxine levels during smolting in captive and wild Atlantic salmon, Salmo salar L.
Authors: Youngson A. F. , Simpson T. H.
Published: January 2006

On a commercial fish farm in Western Scotland, smolting Atlantic salmon, Salmo salar L., showed no major changes in serum thyroxine (T4) levels in the spring. In contrast, serum T4 levels in smolting, wild salmon, trapped as they left the Girnock Burn, Aberdeenshire, varied markedly over this period. Serum T4 levels were correlated with the stream discharge rate pertaining as the fish left the stream. Levels in migrating, smolting fish were higher than those in fish captured above the fish‐trap by electro‐fishing. In a stream channel, serum T4 levels in smolting fish caught previously in the fish‐trap were rapidly elevated by exposure to increased water‐flow, whereas levels in fish previously captured above the trap remained substantially unchanged. Serum T4 levels in salmon parr leaving the stream in autumn were generally lower than those in smolting fish leaving in spring and were not demonstrably affected by stream discharge rate.
Age determination and growth of the pollan, Coregonus autumnalis pollan Thompson, of Lough Neagh, Northern Ireland
Authors: Wilson J. P. F. , Pitcher T. J.
Published: January 2006

Scales from Lough Neagh pollan display a large number of checks, making age determination difficult. Sclerite counts showed that an annual check is formed on scales in May and a second accessory check in most young fish in October. The method of ageing from scales was supported by inspection of length‐frequency plots and by following the growth of pollan in their first 2 years of life. The body‐scale relationship was curvilinear. Back‐calculation showed that pollan of both sexes attain a fork length of 29 cm in 5 years (1 ∞=28.9 cm; k= 0.65; l0= ‐0.06 year). There is no evidence that annual growth rates have changed since 1965. Possible environmental causes of scale check formation are discussed.
The immune response of carp, Cyprinus carpio L., following injection of antigen‐antibody complexes
Authors: Secombes C. J. , Resink J. W.
Published: January 2006

Cyprinus carpio immunized with antigen‐antibody complexes formed at equivalence were found to have both good memory and enhanced serum antibody responses compared with fish primed with antigen alone. Only priming with antigen or complex in adjuvent produced comparable results. Complexes formed in antigen excess gave better precipitation responses during the secondary response than in corresponding control groups injected antigen alone or in adjuvant. The role of antigen‐antibody complexes in the fish immune system and the possibility of using such complexes to vaccinate fish are discussed.
Some chemical and physical characteristics of the semen of Cyprinus carpio L. and Oreochromis mossambicus (Peters)
Authors: Kruger J. C. De W. , Smit G. L. , Van Vuren J. H. J. , Ferreira J. T.
Published: January 2006

The chemical and physical characteristics of the semen of Cyprinus carpio and Oreochromis mossambicus were investigated on a comparative and seasonal basis. Results were obtained for the volume, colour and viscosity of the semen, the percentage live spermatozoa, sperm concentrations and the degree and the duration of sperm motility under different environmental conditions. All showed distinct interspecific and less conspicuous seasonal intraspecific differences. Values have also been determined for the organic and inorganic components and the pH and osmolality of the seminal fluid. Some inorganic and organic components indicated seasonal intraspecific differences while all the components, with the exception of sodium and galactose, indicated significant interspecific differences. These observations suggest significant interspecific differences in the testicular secretions of the two fish species which add to the basic physiological differences recorded for the spermatozoa of C. carpio and O. mossambicus. The probable function of the carbohydrates, protein and enzymes present in the semen of these fish species are discussed.
An investigation of the consequences of egg size for the culture of Arctic charr, Salvelinus alpinus (L.)
Authors: Wallace J. C. , Aasjord D.
Published: January 2006

The variation in egg size present in the eggs of Arctic charr, Salvelinus alpinus, was significant for the survival and growth of newly hatched alevins. Alevins from large eggs were larger, grew more quickly, and suffered less initial mortality than alevins from small eggs. The yolk sac was proportionately larger in alevins from large eggs. The largest eggs produced a relatively high proportion of abnormal alevins.
Ovulatory rhythms and over‐ripening of eggs in cultivated turbot, Scophthalmus maximus L.
Authors: (Barton) L.‐A. McEvov
Published: January 2006

The aim of this study was to investigate ageing of ovulated eggs retained in the ovarian lumen of captive turbot, Scophthalmus maximus L., prior to handstripping. The ovulation times of egg‐batches were determined by catheterization, handstripping and plotting the percentage fertilizations and hatches of resulting eggs against time. The catheterization experiments showed that eggs age and change appearance rapidly after ovulation. The stripping method demonstrated that freshly‐ovulated eggs showed greater than 90% fertilization and up to 97% hatch, but ovulated eggs retained in the ovary lumen for 1 day before stripping gave 0% hatch. The turbot showed precise ovulatory rhythms. The time between ovulations varied between individuals but was constant for any one female, making it possible to predict future ovulation times. Three of the females studied had ovulatory periods of alternating length.
An electrophoretic analysis of plasma proteins from juvenile Oncorhynchus tshawytscha (Walbaum)
Authors: Bradley T. M. , Rourke A. W.
Published: January 2006

The plasma proteins of juvenile spring chinook salmon, Oncorhynchus tshawytscha, were examined as a function of development. Two‐way gel electroprioresis of plasma proteins was conducted on samples taken from fish before initiation of downstream migration, from fish classified as actively migrating and from fish that were prevented from migrating. Analysis of the samples indicated that plasma proteins of fish changed depending on the migratory status of the fish. The results were consistent with the notion that some of the factors normally associated with smoltification in species such as steelhead trout, Salmo gairdneri, and coho salmon, O. kisutch, may well be temporally separated in Idaho O. ishawytscha.
Vertebral abnormalities in white crappies, Pomoxis annularis Rafinesque, from Lake Decatur, Illinois, and an investigation of possible causes
Authors: Baumann P. C. , Hamilton S. J.
Published: January 2006

Crappie, Pomoxis annularis, from Lake Decatur, Illinois, were reported to have a high incidence of backbone deformities, an investigation was initiated to determine both the mechanism of vertebral injury and the causative agent. Three groups of fish were collected: normally shaped and abnormally shaped crappies from Lake Decatur and control fish from abnormally shaped crappies from Lake Decatur and control fish from nearby Lake Sangchris. Analysis of organic and inorganic residue levels in fish tissue revealed no significant levels of contaminants in any of the three groups. Evaluation of the mechanical properties, biochemical composition, and density characteristic of vertebral bone showed no significant difference between the three groups. A myxosporidean parasite, found in both normal and abnormally shaped crappies from Lake Decatur, may have been a contributing factor leading to the spinal deformities. We believe that a short‐term exposure to organophosphate insecticides, may have occurred causing muscular contractions and resulting in vertebral damage and abnormally shaped fish.
Post‐fertilization changes in the chorion of winter flounder, Pseudopleuronectes americanus Walbaum, eggs observed with scanning electron microscopy
Authors: Perry D. M.
Published: January 2006

Little has been reported on the fine structure of the outer membrane of fish eggs during and after fertilization. When observed in the scanning electron microscope, the unfertilized egg of the winter flounder, Pseudopleuronectes americanus, is characterized by a crisscross pattern of depressions. These depressions radiate in all directions across the membrane surface creating a wrinkled appearance. After fertilization, the surface of the chorion becomes regular with a smoother appearance. The pores of the unfertilized egg are flush with the chorion surface, but become thickened and elevated after fertilization. While the chorion of the unfertilized egg is also smooth and uniformly textured, the chorion of the fertilized egg appears granular by first cleavage of the blastodisc. Although no apparent change occurs in the distance between pores after fertilization, statistically significant decreases in pore diameter occur 5 min after fertilization. These results are compared to those on egg membranes of other species of fish and invertebrates.
Scanning electron microscopic study of the oesophageal mucous layer in the eel, Anguilla anguilla L.
Authors: Humbert W. , Kirsch R. , Meister M. F.
Published: January 2006

The structure of the mucous layer covering the oesophageal epithelium was analysed by scanning electron microscopy in the eel, Anguilla anguilla. Different fixation procedures were used to conserve the mucus in situ. The mucous layer changes progressively down the oesophagus from a thick dense layer to a very thin fibrous network. The possible roles of these mucous structures in ion absorption are discussed.
Dynamics of prevalence of Ligula intestinalis (L.) in Catostomus commersoni (Lacépède)
Authors: Black G. A. , Fraser J. M.
Published: January 2006

Prevalence of Ligula intestinalis in Catostomus commersoni was followed in four lakes near Algonquin Provincial Park, Ontario from 1963 to 1981. Two lakes remained in the natural state, except for regular sampling, and prevalence of the parasite fluctuated from 0.3 to 3.6% and from 1.5 to 13%. Prevalence was higher in fishes from the other two lakes. Fishes in the latter two lakes were removed with ichthyotoxin during the study. Fishes and parasite subsequently recolonized the lakes. Prevalence of the parasite peaked and then declined during recovery in each of the two lakes. Prevalence of the parasite fluctuated around levels which were unique for each of the four lakes. Differences in the level of prevalences among the lakes were probably most dependent on differences in the morphology of the lake basins.
Factors affecting the chemiluminescent response of fish phagocytes
Authors: Stave J. W. , Roberson B. S. , Hetrick F. M.
Published: January 2006

The effects of several factors on the phagocytic activity of cells isolated from the pronephros of striped bass, Morone saxatilis, were measured using a chemiluminescence (CL) assay. The CL responses of phagocytes to varying concentrations of bacteria, phorbol myristate acetate (PMA), and zymosan were shown to be dose‐dependent. Incubation of phagocytes with PMA resulted in a decrease in cell numbers related to the concentration of PMA used in the assay. Opsonization of Aeromonas hydrophila with normal pooled bass serum decreased the number of colony forming units present in suspension while enhancing the CL response by striped bass phagocytes. Opsonization of zymosan also resulted in an enhanced CL response. Aeromonas hydrophila and Aerococcus viridans killed by heat treatment, incubation with formalin, or exposure to UV radiation elicited little or no CL when incubated with phagocytes.
Reproductive ecology of female Oligocottus snyderi Greeley: a North American intertidal sculpin
Authors: Grossman G. D. , DeVlaming V.
Published: January 2006

The reproductive condition of female Oligocottus snyderi Greeley during 18+ months at Dillon Beach, California was examined. Seasonal differences in reproductive condition were identified by diameter measurements of ovarian follicles in pre‐vitellogenic, cortical alveoli and vitellogenic stages of development which showed that female O. snyderi appeared capable of reproduction during 6 to 8 months of the year. Reproduction occurred from late autumn to early spring and it is likely that females reproduce more than once a year. Follicular development within the population was asynchronous; development within individual females was group synchronous. The percentage of females with vitellogenic follicles in each collection was negatively correlated with photoperiod and productivity and positively correlated with wave action. Conversely, the percentage of newly recruited individuals in each sample was positively correlated with photoperiod and productivity. It appears that reproduction and recruitment in O. snyderi are significantly influenced by annual productivity cycles; daylength changes may provide an anticipatory cue for the productivity cycle.
Reproductive anatomy of the Australian grayling, Prototroctes maraena Gunther
Authors: Berra T. M.
Published: January 2006

Gross anatomy of Australian grayling testes showed progressive enlargement from March to the peak of the spawning season in late April–early May. The single, left testis changed from a flat, translucent wisp of tissue consisting of an anterior and posterior lobe connected by a thin filament to a three‐dimensional mass of milky‐white tissue which filled the coelomic cavity. Spawning lasted 2 weeks and testicular regression was apparent by 8 May when the bilobed condition of the testis was noted. The testis cleared rapidly and resembled pre‐spawning conditions by mid‐June. Histological examination revealed that Australian grayling testes follow the pattern of teleost spermatogenesis whereby clusters of spermatogonia arise from resting germ cells and all of the cells within a given cluster mature at approximately the same time.

The single left ovary of Australian grayling females showed a similar pattern of development, filling the body cavity with an average of 47 000 eggs of 0.9 mm diameter by late April–early May. Females exhibited swollen genital vents near spawning and males developed breeding tubercles which are illustrated by scanning electron micrograph.
The induction of maturation and ovulation in American eels, Anguilla rostrata (LeSueur), and the relevance of chemical and visual cues to male spawning behaviour
Authors: Sorensen P. W. , Winn H. E.
Published: January 2006

Female American eels, Anguilla rostrata (LeSueur), were artificially matured with injections of salmon and carp pituitary and human chorionic gonadotropin. In vivo ovulation was induced with 4‐pregnene‐17α,20β‐diol‐3‐one and eggs were spontaneously released. Eggs were fertilized in vitro and survived to the gastrula stage. Males were matured with injections of human chorionic gonadotropin. They were attracted by the sight and odour of maturing and mature females. Ovulated females released a sex pheromone which was especially attractive to mature males and triggered the release of sperm.
Surface secretions of the skin of Blennius (Lipophrys) pholis L.
Authors: Whitear M. , Mittal A. K.
Published: January 2006

Mucus is secreted to the surface of the body and fin webs of Blennius pholis by superficial epithelial cells and by goblet cells. Some goblet cells secrete sulphated acid glycoproteins, others produce a mucus which is neutral or mixed in its reactions. The superficial epithelial cells of these areas secrete sulphated acid glycoproteins, seen by electron microscopy as electron‐lucent or moderately lucent vesicles; this secretion is not normally visible external to the skin in transmission electron microscope (TEM) sections. These cells do not react to the bromphenol blue test for proteins. Over part of the surface of the pelvic fins and the distal parts of the rays of the pectoral fins, the skin contains no goblet cells and bears a thick external secretion, or cuticle, containing protein and glycoprotein which is mainly neutral in reaction, although some cells at the edges of the region secrete weakly sulphated or non‐sulphated acidic glycoprotein. The protein content of the columnar superficial epithelial cells of these regions correlates with the fibrous nature of the secreted cuticular layer as seen by TEM; the columnar cells are characterized by extensive ribosomal endoplasmic reticulum and vesicles which stain darkly with phosphotungstic acid, less so with uranyl acetate. The distal part of the cell, containing these vesicles, reacts positively to the PAS stain. In some places the borders of the zones with fibrous cuticle are characterized by cuboidal superficial epithelial cells which give a strong positive reaction to alcian blue at pH 1.0, indicating the presence of sulphated acid glycoproteins, but also react positively to the bromphenol blue test for proteins.
A scanning electron microscope study of the life cycle of Bothriocephalus acheilognathi Yamaguti, 1934
Authors: Pool D.
Published: January 2006

The stages in the life cycle of Bothriocephalus acheilognathi have been studied with the aid of scanning electron microscopy. Emergence of the coracidium occurred after 3–5 days at 20°C. Soon after hatching the coracidium began to swell and the cilia became coiled and lost their locomotory function. The surface of the coracidium was covered in protuberances of unknown function. After consumption by the copepod intermediate host, the coracidium developed into a procercoid. Upon development of a cercomer the procercoid could infect the fish definitive host. Identification of adult B. acheilognathi should be made on specimens relaxed in cold water for 10 min, and be based on the heart shaped scolex and prominent square apical disc.
Seasonal population dynamics of the nematode Cystidicoloides tenuissima (Zeder) from the River Swincombe, England
Authors: Aho J. M. , Kennedy C. R.
Published: January 2006

The seasonal population dynamics of adult and larval Cystidicoloides tenuissima were studied in its definitive hosts brown trout, Salmo trutta and juvenile Atlantic salmon, S. salar, and mayfly intermediate host, Leptophlebia marginata, from the River Swincombe, Dartmoor National Park, Devon, U.K. Infective larvae were present in each mayfly generation for almost its entire duration in the steam benthos. The infection parameters (prevalence and mean intensity) and maturation in the fish indicated C. tenuissima was an annual parasite exhibiting a seasonal periodicity and also systematic variation with the host age. Maturation was correlated to river water temperature. Infection parameters increased from September to May, then declined in June and July and remained relatively constant for the rest of the summer. Variation in the fish infection parameters over time, site, and host species appeared to be controlled by transmission related events; the availability of infective larvae, host feeding behaviour and water temperature. The availability of infective larvae and host diet controlled the rate at which parasites were added to the parasite population, but the pattern of gains and losses was determined by a temperature dependent rejection response.
Susceptibility of starved, juvenile smallmouth bass, Micropterus dolomieui (Lacépède) to low pH
Authors: Kwain W. , McCauley R. W. , MacLean J. A.
Published: January 2006

Juvenile smallmouth bass, Micropterus dolomieui, were starved over a period of 6 months in the laboratory and their survival in waters of low pH tested. The ability of the bass to withstand the toxic effects of hydrogen ion decreased with time. The LC50 (96‐h) changed from pH 3.7 to pH 4.4 over the experimental period. During the final days, the decrease in the threshold was greatly accelerated. In the wild, some overwintering bass are subjected to pulses of water as low as pH 4.7 as a result of vernal snowmelt. Bass at the end of winter are often emaciated and are especially susceptible to acid stress.
Oxygen requirements of larvae of the smallmouth bass, Micropterus dolomieui Lacépède
Authors: Spoor W. A.
Published: January 2006

Smallmouth bass larvae became highly sensitive to oxygen deficiency on the second day after hatching and continued so to the 10th day. During this period they could not survive exposure to 1 mg O2 l–1 for 3 h at 20° C, and many were killed within 1 h. At 2 mg O2 l–1 half the larvae survived 3 h at 20° C; at 2.5 mg l–1 most survived, and at 3.5 mg l–1 all survived. Resistance to oxygen deficiency was regained by the 11th day, the majority of the larvae withstanding a 3‐h exposure at 1 mg O2 l–1. At 25° C the effects of low oxygen concentration were intensified. At 3 and 4 mg O2 l–1 and 20° C the normally quiescent larvae became very active, even swimming to the surface 5 or 6 cm above the substrate. Increasing the temperature increased this response. Smallmouth larvae were more sensitive than large‐mouth bass larvae to oxygen deficiency.