bluuebunny/crossref_metadata_2025_split huggingface dataset:
The food of larval blue whiting, Micromesistius poutassou (Risso), in the Rockall area
Authors: Conway D. V. P. 
Published: January 2006

Larval blue whiting of 3–42 mm total length, taken in 1967 and 1968 in the Rockall Bank area, were found to have fed almost exclusively on various stages of small crustaceans; the eggs, nauplii and copepodites of copepods, along with fewer numbers of larval euphausiids and Evadne nordmanni, formed the major proportion of the diet. The guts of the larger larvae contained a greater number of, and larger organisms, than those of the smaller larvae. Feeding incidence was generally lower at night. There was a general increase in the weight of the gut contents as the daylight hours progressed followed by a decrease during the night. Diurnal variation in the percentage composition of the food was also demonstrated. Comparisons of the diet in the two years showed that more food was consumed by almost all sizes of larvae in 1968.It has previously been suggested that blue whiting larvae may find better feeding conditions on Rockall Bank than off the Bank. However the present study suggests that larvae, particularly of 8 mm and longer, took more food when off the Bank. A brief comparison is made of the gut contents of the larvae of blue whiting and of the other eight most abundant species.
The effects of powdered carp pituitary on ovarian development, ovarian ascorbic acid and ovulation in Carassius carassius L. exposed to various photoperiod and temperature regimes
Authors: Seymour E. A. 
Published: January 2006

The effects of temperature, photoperiod and powdered carp pituitary on ovarian development (measured by change in diameter of intraovarian eggs and gonadosomatic index), ovulation and ovarian ascorbic acid have been studied in crucian carp in winter. Short photoperiods stimulated ovarian development but long photoperiods were inhibitory. Photoperiod seemed to exert this effect by altering the release of pituitary gonadotropin. Temperature affected ovarian development independently of photoperiod. High temperatures were stimulatory and overcame the negative effect of a long photoperiod. The results suggested that temperature acts at the level of the gonad rather than the pituitary. On the basis of these findings a hypothesis is suggested to explain gonadal cycles in cyprinids and similarities to previous findings in other fish groups are discussed.Levels of ovarian ascorbic acid varied according to treatments. Ovulation was associated with a decreased level. The results suggested that this vitamin aids biosynthesis of sex steroids in a similar fashion to that observed in higher animals. The results also demonstrated that measurement of gonadal ascorbic acid can provide a useful indication of physiological events at the level of the gonad.
Trophic biology of herbivorous reef fishes: alimentary pH and digestive capabilities
Authors: Lobel P. S. 
Published: January 2006

Certain herbivorous fishes are well known for morphological specializations enabling trituration; such as scarids with a pharyngeal mill and mullets with a gizzard‐like stomach. However, utilization of plant foods by fishes is limited by these animal's digestive capabilities, most notably the apparent lack of cellulose digesting enzymes. Fishes possessing a grinding mechanism are able to break open plant cells for digestion. But how fishes without grinding mechanisms make plant cell contents accessible to digestion is unknown. These fishes include many acanthurid and pomacentrid species which are among the most abundant on reefs.Another mechanism for rupturing plant cell walls has been recently proposed, namely lysis by gastric acidity. This study surveyed stomach and intestinal pH for 17 herbivorous species at Fanning Atoll, Central Pacific and two species from St Croix, Caribbean with additional data for seven selected carnivorous species. The herbivorous fishes included acanthurids (surgeonfishes), mugilids (mullets), pomacanthids (angelfishes), pomacentrids (damselfishes) and a scarid (parrotfish). The effect of different pH concentrations and trituration was examined experimentally for eight common Pacific marine algae including two reds, two blue‐greens, two greens, one brown, and the algal mat complex from inside damselfish territories.Fishes, possessing morphological adaptations for trituration, ingested quantities of calcium carbonate material and did not contain gastric acidity low enough to lyse algal cell wells. However, fishes without grinding mechanisms but with defined stomachs have gastric pH values from 2.4 to 4.25 which can be as effective as trituration in releasing algal cell contents of certain algae. These results are considered in a review of previous studies of herbivory in fishes. The trophic relationship between fishes and algae of specified morphologies are predicted by extrapolation from the experimental results on algae vulnerable to acid lysis or trituration.
Gross and fine structure of the pseudo branch of the climbing perch, Anabas testudineus (Bloch)
Authors: Munshi J. S. D. , Hughes G. M. 
Published: January 2006

The structure of the glandular pseudobranch of the air‐breathing fish Anabas testudineus is described on the basis of light and electron microscopy. It is shown that the pseudobranch has the same basic structure as a typical gill, although in this case it is not freely exposed to the water.Individual secondary lamellae can be recognized in which well‐defined, but narrow, blood channels are present between typical pillar cells. The epithelial layer is mainly represented by enlarged mitochondria‐rich cells which constitute a large proportion of the whole organ. Mitochondria‐rich cells contain an abundant endoplasmic reticulum which is in close contact with the mitochondria and becomes concentrated near the vascular borders of the cell and opens directly into the basement lamina.The presence of numerous pinocytotic vesicles in the enlarged pillar cell flanges may transfer material to the blood channels. The precise nature and role of any materials released in this way remains to be investigated.
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.
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.
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.
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.
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.
Sexual maturation in triploid rainbow trout, Salmo gairdneri Richardson
Authors: Lincoln R. F. , Scott A. P. 
Published: January 2006

This paper compares some morphological and endocrinological characteristics of diploid and triploid rainbow trout.Significant differences were found between diploid and triploid females in GSI, condition factor, gut weight, liver weight and percentage dress‐out, and between diploid and triploid males in GSI, condition factor and gut weight.Diploid females had large, well‐developed ovaries containing yolk‐filled secondary oocytes whereas the triploids had only string‐like ovaries containing nests of oogonia. No primary oocytes were present.All the diploid males produced copious quantities of milt but it was possible to express a thin, watery milt containing motile spermatozoa from only two of the 12 triploid males. Testes weights in triploids were similar to those of diploids but, while the diploid testes were packed with spermatozoa, those of the triploids consisted mainly of spermatocytes and spermatids with few spermatozoa present. Measurements of the heads of spermatozoa revealed that those from triploids were larger and had a wider size range than those from diploids.Levels of testosterone and 11‐ketotestosterone in triploid and diploid males were not significantly different. However, levels of testosterone and 17β‐oestradiol in diploid females were considerably higher than those of triploid females.
The effect of starvation on RNA: DNA ratios and growth of larval striped bass, Morone saxatalis
Authors: Wright D. A. , Martin F. D. 
Published: January 2006

Hatchery reared larval striped bass, Morone saxatilis, 8‐days‐post‐hatching were subjected to various feeding/starvation regimes over a period of 14 days.Batches of larvae from each treatment were sampled over the 14‐day period and subdivided for determination of notochord length and RNA:DNA ratio. The best growth was found in fully fed F1000 larvae (exposed to 1000 Artermia nauplii l−1), which reached 8.2 mm after 11 days and 9.6 mm after 14 days. Starved animals after 11 days had notochord lengths of 4.9 mm. Growth curves from feeding‐delayed larvae indicated that animals fed after up to 5 days starvation were capable of complete recovery. F100 larvae (exposed to 100 Anemia nauplii 1−l) had a slower growth rate than F1000 larvae, reaching a notochord length of 7.3 mm after 14 days. RNA:DNA ratios over time closely followed notochord growth curves, with clear differences between starved, F100 and F1000 larvae being established after only 2 days. Equilibrium RNA:DNA ratios of 3.0 and 2.25 were established in F1000 and F100 larvae, respectively, 6.8 days after the beginning of the experiment. The average lag time between a change from the starved to the fed condition and a change in RNA:DNA ratio as determined by the divergence of the nucleic acid curve from the starved condition was 0.66 days.In treatments where starvation followed various periods of feeding, larvae regressed in notochord length such that the final length at 14 days reflected the degree of feeding. RNA:DNA ratios in these animals again closely followed growth curves with a lag time of 0.81 days.It was concluded that RNA:DNA ratios provided very accurate indices of growth in striped bass larvae which were highly sensitive to feeding status.
Evaluation of pulse fishing for the walleye, Stizostedion vitreum vitreum, in Henderson Lake, Ontario
Authors: Reid D. M. , Momot W. T. 
Published: January 2006

A total of 3226 walleye were removed from Henderson Lake, Ontario over 3 years (1980–2), causing the stock to collapse. This removal tested the applicability of ‘pulse’ fishing as a management alternative, and also provided an opportunity to determine which population characteristics might be monitored to serve as predictors of stock collapse in this species.Following initial exploitation, increased length at age occurred only within younger age‐lasses. To use this response as a predictor, one must first obtain pre‐exploitation length‐at‐age data through using the proper gear to sample small fish. Abrosov's mean age to mean age at maturity index may also forewarn of stress (1.2 critical t value for Henderson Lake), but poor recruitment usually invalidates this index, since the lower angling vulnerability of large fish biases mean age calculations. While annual production estimates were a good indicator of the collapse, their determination required much effort. Petersen population estimates produced much more realistic estimates of population size than Schumacher–Eschmeyer estimates, but both estimates not only require much effort but also are influenced by changes in recruitment.Poor predictors of the walleye collapse included: catch‐per‐unit‐effort data, which, while giving some idea of fish density, were not good indices of exploitation stress; condition factors, which were not correlated to fish abundance; fecundity increases, which suffered far too much of a retarded response in Henderson Lake to serve as a predictor of stock collapse. The inability to determine accurately sex ratios of measure recruitment made these parameters unless.At least over the short term, neither northern pike nor white sucker populations have increased following the walleye collapse. As yet, walleye have not returned to their former abundance, so the operational usefulness of ‘pulse’ fishing remains an unknown.
Lake resident and migratory smelt, Retropinna retropinna (Richardson), of the lower Waikato River system, New Zealand
Authors: Northcote T. G. , Ward F. J. 
Published: January 2006

Retropinna retropinna occurred in two forms in Lake Waahi, North Island, New Zealand. One form was characterized by high mean gill raker counts (c. 28) and low mean vertebral counts (c. 52)—similar to those of non‐migratory, lake resident, native smelt in some other lakes of the lower Waikato River system. The other form had low mean gill raker counts (c. 21) and high vertebral counts (c. 60)—similar to migratory smelt at five sites along the lower Waikato River down to its estuary. The lake resident form was shorter but deeper bodied than the migratory form, as indicated by significant differences in mean length and in weight‐length regression analyses.The two forms overlapped in time of sexual maturity. As in other native lacustrine smelt populations of the lower Waikato system, the resident form had more but smaller eggs than the migratory form. The egg number to body length regression and the mean egg diameter of migratory Lake Waahi smelt were similar to those of lower Waikato River smelt. Evidence for reproductive separation of the two forms is presented and mechanisms controlling their meristic and other differences are considered.
Growth, mortality, parasitism, and potential yields of two Priacanthus species in the South China Sea
Authors: Lester R. J. G. , Watson R. A. 
Published: January 2006

In the northern part of the South China Sea the ‘big‐eye’, Priacanthus tayenus, spawned once a year in June, had von Bertalanffy growth parameters of k = 0.8 and L∞= 30 cm, and a mean total annual instantaneous mortality of Z= 2.0, calculated from adjusted catch curves and a mean length equation. The natural mortality rate M= 1.4, fishing mortality rate F= 0.6, and the exploitation rate (E) was 0.27. The maximum potential yield, calculated using Marten's method, was 0.06 kg/recruit when F= 5.4. The fish were heavily parasitised by the protozoan Pleistophora priacanthicola.A second big‐eye, P. macracanthus, spawned twice a year in May‐June and September, had growth parameters of κ= 0.7 and L∞= 32, and population parameters of Z= 2.0, .F= 0.7, and E= 0.34. The maximum potential yield was 0.13 kg/recruit when F= 5.8.A marked reduction in fishing mortality occurred for both species between 1965 and 1966, coinciding with the onset of the Chinese Cultural Revolution. Our estimates of maximum potential yield correspond to fishing mortalities eight times estimated levels, though such heavy exploitation could risk recruitment failure.
Infestations of Atlantic salmon, Salmo salar, by Gyrodactylus salaris in Norwegian rivers
Authors: Johnsen B. O. , Jensen A. J. 
Published: January 2006

Over the 6 years 1980–85, 212 Norwegian rivers have been examined for occurrence of Gyrodactylus salaris: it was found in 26 rivers and six salmon hatcheries scattered throughout the country from Troms county in the north to Sogn og Fjordane in western Norway. The distribution of G. salaris is connected with the stocking of fish from infected salmon hatcheries. The populations of salmon parr have been drastically reduced in the infected rivers. In later years catches of ascending salmon in these rivers have also sharply declined: in 1984 salmon fishery losses were estimated at 250–500 t. Gyrodactylus salaris is most probably a recent introduction to Norwegian rivers. A primary aim is to exterminate this parasite from all infected rivers and hatcheries: so far this has been accomplished in one river and one hatchery.
Physiological salines and the mechanical properties of trout red blood cells
Authors: Hughes G. M. , Kikuchi Y. , Barrington J. 
Published: January 2006

Suspensions of rainbow trout erythrocytes in different physiological salines were compared with respect to their haematological and filtration properties.A method is described for the suspension of erythrocytes in Cortland saline which has proved suitable for studies of their mechanical properties over periods of several hours.Significant differences were found between whole blood samples taken during cannulation and after several days recovery, particularly mean cell volume, frequency distribution of red cell volumes and the pore passage time through nucleopore filters. These differences were also found using red cell suspensions of the same bloods. The pore passage time of whole blood sampled during cannulation or its suspensions is less than that of recovery blood although its mean cell volume is greater.
Population estimates of juvenile Atlantic salmon, Salmo salar, as indices of smolt production in the R. Scorff, Brittany
Authors: Baglinière J.‐L. , Champigneulle A. 
Published: January 2006

The numerical production of juvenile Atlantic salmon was estimated on an Armorican Massif river (Brittany), using habitat characteristics of the main stream and an annual electrofishing census from 1975 to 1983. This showed that (i) 0 + fish accounted for 79% of the production; (ii) there were larger annual variations of production in spite of some compensatory events depending on genetic and environmental factors; (iii) riffles and rapids (depth <40cm, current velocity > 40 cm s−1) were the more productive habitats, providing 86.4% of the production from 28% of the water area; (iv) the middle course of the river accounted for 57.6% of production, producing more 1 + individuals in a large area of rapids.Features of this method, their limitations and the value of the results are discussed in relation to the estimation of smolt production.