bluuebunny/crossref_metadata_2025 huggingface dataset:
Some observations on the food of the gwyniad Coregonus clupeoides pennantii Valenciennes of Llyn Tegid (Lake Bala), North Wales
Authors: Haram O. J. , Jones J. W.
Published: January 2006

The seasonal variations in the diet of adult gwyniad Coregonus clupeoides pennantii=C. lavaretus from Llyn Tegid, North Wales were studied. Stomachs were examined to determine fullness, volume and identity of contents.

A clear seasonal cycle in food intake was found. Feeding rates were low from January to April but increased during the summer (May‐June) and remained at a high level until December. The period of low feeding intensity coincided with the time of spawning and the time of annulus formation of both scales and otoliths. The diet showed seasonal changes and two main periods were distinguished : December to July, when the fish fed mainly on bottom fauna, and August to November, when the diet included both bottom fauna and midwater and surface foods.

The gwyniad were shown to be opportunistic in feeding, the composition of the diet reflecting availability of food items rather than selective feeding on the part of the fish.
The growth of brown trout Salmo trutta L. in northern Scottish lochs with special reference to the improvement of fisheries
Authors: Campbell R. N.
Published: January 2006

This paper is based on the investigation of 173 lochs in Scotland from which a total of over 4700 brown trout were examined. Twenty‐four of the lochs, all in northern Scotland, and their trout populations, were selected for detailed comparison in an attempt to identify environmental factors that might affect the growth rate of trout. The lochs probably represented the full range of main standing water habitats in the region‐ranging from a saline loch in the Outer Hebrides to one in a sub‐arctic environment high on the Cairngorm plateau in the Central Highlands. The study indicates that for practical purposes the growth rate of trout is negatively correlated with population density. Some suggestions for improving brown trout lochs, based on the findings of this paper, are included.
The anatomy and histology of the alimentary tract of the carnivorous fish the pike Esox lucius L.
Authors: Bucke David
Published: January 2006

The alimentary tract of the pike is described, relating its feeding habits to its intestinal gut histology. It is a carnivorous species having a short oesophagus, pouch‐like stomach and a short intestine with two convolutions. Stratified epithelium with columnar cells and many goblet cells are present in the oesophagus, columnar epithelial cells only in the stomach, and both cell types in the intestine.

Eosinophils in the mucosa of the oesophagus originate from connective tissue cells and lymphocytes and neutrophils are present. The lamina propria is composed of a stratum granulosum, stratum compactum, blood vessels and loose areolar tissue. The stratum compactum is a strengthening substance, composed of collagen, characteristic of carnivorous teleosts. The circular and longitudinal muscle layers and serosa are similar to those of other carnivorous teleosts.

The pancreas and liver are briefly described, the pancreas being the unusual compact type not often found in teleosts. The B cells are seen in the periphery and a cells in the centre of the islets. The liver is a unilobular organ, having oil storage as a major function.

The distribution of goblet cell mucin is given, differentiating it into neutral and acid mucosubstances. Nine levels of alimentary tract were examined in the mucin distribution study. The functions of mucin in the pike are digestion, absorption, protection and lubrication.
The inflammatory response of rainbow trout*
Authors: Finn J. Peter , Nielson N. O.
Published: January 2006

The basic responses of piscine tissues to inflammatory agents were investigated, using light microscopy. Tissue sections, smears and blood smears were examined. The period studied was from 3 h to 16 days after initial injury at 15°C. The piscine inflammatory response was compared to that of mammals, especially that of mice. The responses examined were basically similar to those of mammals. They varied by being less intense and slower to appear and resolve.
An evaluation of the acadja method of fishing as practised in the coastal lagoons of Dahomey (West Africa)
Authors: Welcomme R. L.
Published: January 2006

A method of fishing using installations of the fish‐park type, known collectively as acadjas, is common in the coastal lagoons of Dahomey. Acadjas are installed in shallow sheltered waters and are constructed of dense masses of branches planted in the muddy bottom. Two main types exist, small circular acadjavis and large rectangular avas, but these may be combined to give a variety of other forms. After construction the acadjas are left for varying periods before being fished. Many species of fish are found in the installations, but the majority of these are only casual invaders and most of the catch consists of 3 species only. The fish population appears initially to be derived from immigration, but after c. 2 months of implantation, increases exponentially by growth and reproduction. Acadjas that are fished after short periods of installation are therefore regarded as refuge traps, drawing fish from the surrounding environment, where those that are left longer before being fished, develop their own populations. The yield of the acadjas also increases logarithmically with increasing densities of branches planted. Properly managed acadjas may be regarded as a method of fish culture, which, because of the exceptional yields that can be attained, are a potential means of development for shallow mud bottomed waters such as the West African coastal lagoons.
Comparative swimming abilities of fed and starved larval largemouth bass (Micropterus salmoides)†
Authors: Laurence Geoffrey C.
Published: January 2006

Sustained swimming abilities of fed and starved larval largemouth bass (Micropterus salmoides L.) were compared in the first week after swimming initiation. Fed larvae improved to a sustained velocity of 4·0 cm/sec while starved larvae attained a velocity of only 1·5 cm/sec. Swimming behaviour for fed and starved larvae was quantified for number of moves, average distance/move, and total distance for all moves in 1 min intervals. Fed larvae were always more active than starved larvae, although real differences did not appear until the 4th day after swimming initiation.
Studies on the skin of plaice (Pleuronectes platessa L.)
Authors: Roberts Ronald J. , Young Hamish , Milne J. A.
Published: January 2006

A histological, histochemical and ultrastructural examination of the skin of wild and cultured plaice was carried out, using fish from each year class from 0+ to 4+. The skin was shown to be similar in general structure to that of other teleosts but a previously undescribed cell, designated the Eosinophilic Granular Cell, a dendritic secretory cell found throughout the basal layers of the epidermis, is described. It was fixed only by formalin or dichromate, and contained numerous acidophilic granules. Melanin‐bearing macrophages were observed migrating through the epithelium, but no DOPA or tyrosinase positive cells were observed by the methods used. Mast cells were very common in the dermis but were only demonstrable by special techniques. The melanophore and guano‐phore systems are described and although no melanophores or melanocytes were found in the unpigmented areas of partially pigmented hatchery‐reared fish, the integrity of the guanophore system was complete in such fish.
Some aspects of pathogenesis of infectious hematopoietic necrosis (IHN)
Authors: Yasutake William T. , Amend Donald F.
Published: January 2006

The histopathogenesis of infectious haematopoietic necrosis (IHN) virus infection was studied by exposing juvenile sockeye salmon (Oncorhynchus nerka) to the IHN virus. Fish samples were taken every 24 h for histological examination and for determination of virus concentration. A close correlation was found between histopathological changes and virus concentration. The most significant changes occurred 4 days after exposure. The haematopocitic tissue of the kidney was the most extensively involved but minor degenerative changes were seen in the liver, pancreas, and in the granular cells of the digestive tract. On the 4th day, maximum tissue concentration of virus was reached and the mortality increased. By the 5th day, 90% of the samples showed extensive pathological changes in the kidney, together with variable changes in spleen, liver, pancreas, and gut. Similarities in the histopathogenesis of IHN, Oregon sockeye disease (OSD), Sacramento River chinook disease (SRCD) and viral haemorrhagic septicaemia (VHS), are discussed.
Population biology of the helminth parasites of Phoxinus phoxinus (L.), the minnow, in a Cardiganshire lake
Authors: Bibby M. C.
Published: January 2006

Specimens of Phoxinus phoxinus (L.) were collected over a period of a year from September 1967 to September 1968 from Frongoch Lake, Cardiganshire, Wales. Of a total of 650 fish examined for helminth parasites, 32 % were definitive hosts for Macrolecithus papilliger, and 16·5% for Neoechinorhynchus rutili (Müller), both parasites of the alimentary canal. All the fish examined were second intermediate host for Diplostomum phoxini (Faust) in the brain and 1·67% for Ligula intestinalis (L.) in the coelom. An increase in incidence of infestation with M. papilliger in spring and autumn and with N. rutili in summer were evident. The sex of the fish had no apparent effect on worm burden whereas size was more significant. There was a decrease in incidence of infestation with M. papilliger and an increase with N. rutili together with an increase in intensity of infestation with D. phoxini as the fish became larger. The latter species accumulated in the brain as the host increased in age.
An aeromonad epidemic in the brown trout (Salmo trutta L.)
Authors: Thorpe J. E. , Roberts R. J.
Published: January 2006

The pathology and bacteriology of an aeromonad epidemic in the spawning population of brown trout (Salmo trutta L.) of the freshwater Loch Leven, Kinross, Scotland, is described, together with estimates of its quantitative effect on the stock of trout.
The growth, reproduction and food of the roach Rutilus rutilus (L.), of the River Lugg, Herefordshire
Authors: Hellawell J. M.
Published: January 2006

Checks were formed on the scales in June and July. A dominant 1959 year class accounted for half the population present in 1964. Females grew faster than males and attained greater ultimate size. Growth in the River Lugg was good in comparison with rates in other British waters. The sex ratio was found to change with age; a predominance of males in the youngest age classes changed to a preponderance of females in the older classes. The youngest fishes caught (3+) were already sexually mature. The gonads were found to be a constant proportion of the body weight for fishes of all sizes at a given season. Spawning was completed by June; males were ripe in May. The ovaries recovered more rapidly than the testes after spawning. Seasonal variation in feeding activity, with higher activity in summer, was observed and could be correlated with temperature. Seasonal changes in the diet could be related to availability. The diet was predominantly vegetable; the most important animal component, aquatic insect larvae, accounted for 11 % of the total diet. Aerial insects were rarely eaten. Diet varied with age: molluscs being particularly important to older roach; younger roach consumed large amounts of substrate material. There is some evidence that young roach indiscriminately ingest substrate material but older roach are more selective and reject inert material.
A simple egg box planting technique for estimating the survival of eggs deposited in stream gravel
Authors: Harris G. S.
Published: January 2006

A simple technique for estimating the survival of eggs during their incubation in stream gravels by planting eggs in specially designed egg boxes is described. This technique ensures that all the live eggs and alevins present in the gravel at the time of sampling can be recovered. Survival can be calculated accurately from the ratio of the number of live recovered to the number of eggs originally planted and the errors caused by the loss of dead eggs and escape of live alevins from the sample area are avoided.
A study of the swimming performance of the Crucian carp Carassius carassius (L.) in relation to the effects of exercise and recovery on biochemical changes in the myotomal muscles and liver
Authors: Johnston I. A. , Goldspink G.
Published: January 2006

A study has been made of the maximum sustained swimming speed of Crucian carp Carassius carassius (L.) using a fixed velocity technique. The data obtained from swimming tests on 214 carp have been analysed using the method of probit analysis. The 50% fatigue level for 13–16 cm fish acclimated to 9.5±0.6°C has been estimated to be 3.35 lengths/sec. Biochemical measurements have been made on the red and white myotomal muscles and liver of fish subjected to both varying intensities of sustained swimming and short periods of vigorous swimming. Free creatine was found to increase only during high speed swimming in the white muscle. Elevated lactate concentrations occurred at both low and high sustained swimming speeds in the red superficial muscle but not during short periods of strenuous exercise. Glycogen depletion from the red musculature also only took place at the sustained swimming speeds investigated. The reverse situation was operative in the white muscle, significant glycogen depletion occurring only at the highest swimming speed studied. Lactate levels were only significantly different from non‐exercised fish in the fish swimming at the higher velocities. The effects of periods of recovery following 200 min of sustained swimming were also investigated. White muscle lactate was at a higher level than non‐exercise fish 5 h post‐exercise, while both red muscle glycogen and lactate rapidly returned to pre‐exercise concentrations. Biochemical measurements on the myotomal muscle types have been discussed in relation to the swimming performance of the fish and the division of labour between red and white fibres.
Characteristics of an established goldfish Carassim auratus (L.) cell line
Authors: Rio G. J. , Magnavita F. J. , Rubin J. A. , Beckert Wm H.
Published: January 2006

A new continuous line of goldfish somatic cells, designated SJU‐1 has been continuously subcultured over a 39‐month period. Best growth was obtained at 20°C over a pH range of 6.8–7.2. The minimal and optimal seed inocula, in terms of per cent cell increase, were determined to be 1.1 × 106 and 2.5 × 106, respectively. The susceptibility of the SJU‐1 line to infectious pancreatic necrosis virus offers an available assay system for goldfish in vivo and goldfish cells in vitro interferon studies. Chromosomal analyses of the line were also carried out.
The rainbow trout Salmo gairdneri (Rich.) fishery of Lake Titicaca
Authors: Everett G. V.
Published: January 2006

Rainbow trout were introduced to Lake Titicaca in 1942. A commercial trout canning operation started in 1961 but terminated in 1970. Data for this study were collected in 1966 and 1967, with the object of examining the life history, biology, and commercial fishery of Titicaca rainbow trout. Trout were caught commercially and experimentally by gillnets in different parts of the lake.

Lake Titicaca lies across the border of Peru and Bolivia at 3212 m above sea level. The physico‐chemical characteristics of the lake appear ideal for self‐sustaining populations of rainbow trout. Growth was constant throughout the year, and was good in relation to growth rates of rainbow trout in other parts of the world. Spawning took place in the tributaries in the winter. Recruitment to the fishery occurs in 7.62 cm stretch mesh gillnets at about 27 cm fork length.

The total annual commercial catch increased to 500 metric tons in 1965 before subsequently decreasing. The simplest explanation for the decline in total catch would be the increase in fishing mortality due to increased fishing effort, although it is possible that the decline in water level has had some effect. It appeared possible that the lake could sustain an annual catch of about 350 tons.
The tapetum lucidum in the eye of the big‐eye Priacanthus arenatus Cuvier
Authors: Nicol J. A. C. , Zyznar E. S.
Published: January 2006

The big‐eye Priacanthus arenatus Cuvier contains a tapetum lucidum or reflector which lies in the inner region of the choroid. It extends over the entire surface of the fundus, and it consists of several layers of reflecting cells. The cells contain many layers of thin guanine crystals, and there is about 0.5 mg of guanine in a square cm of tapetum. The retina is duplex, and rods are small and very numerous. The tapetum of the big‐eye is compared with those of selachians and sturgeons, which it much resembles.
Ichthyophthiriasis in the mirror carp
Authors: Hines Ron S. , Spira Dan T.
Published: January 2006

Changes in leukocyte counts in mirror carp infected with Ichthyophthirius multifiliis were recorded during the disease. Leukocytes were classified according to their appearance and stage of development. The overall white blood cell count in infected carp remained within the range found in normal carp under similar conditions. The first recognizable event in leukocyte dynamics was a sharp but temporary drop in lymphocytes with a concurrent rise in neutrophil percentages early in the infection. A similar trend also appeared towards the end of the infection. A significant shift towards younger cell populations was evident among the neutrophils. Blast cells with morphological characteristics of neutrophils appear in the circulation. The percentage of these cells and of other blast cells rose progressively during the infection. The number of cells termed fine reticular cells, also rose during infection. White blood cell changes in the mirror carp infected with I. multifiliis were similar to changes observed for other diseases and also in response to certain stress conditions.
Temperature tolerance of the mosquitofish, Gambmia affinis (Baird and Girard)
Authors: Otto Robert G.
Published: January 2006

The capacity of a warm‐adapted population of mosquito fish (Gambusia affinis) from the Sonoran Desert and a cold‐adapted population from northern Utah to adjust to changing environmental temperatures has been described in terms of four criteria: (1) critical thermal maxima, (2) resistance times at high, lethal temperatures, (3) upper incipient lethal temperatures, and (4) lower lethal temperatures. Non‐genetic scope for adaptation as related to changes in the thermal history of the individual and expressed in terms of the tolerance domain was identical for both populations. Genetic differences in adaptive capacity were apparent. The cold‐adapted population was less tolerant of heat and more tolerant of cold as would be anticipated.
A system for the quantitative study of the learning capacity of rainbow trout and its application to the study of food preferences and behaviour
Authors: Adron J. W. , Grant P. T. , Cowey C. B.
Published: January 2006

A system for the quantitative study of the learning capacity of rainbow trout and its application to the study of food preferences and of behaviour. Groups of trout were self‐trained in about 10 days to actuate a trigger and feed themselves. This capacity was retained for 3 months without the stimulus of continuous reinforcement. Presented with a choice, conditioned populations showed a high degree of discriminatory ability towards a trigger that supplies food and one that does not. The choice system was used to examine preferences for the taste of pelleted foods. A trained population, under continuous illumination developed a feeding rhythm that occurred about every 8 h.
A note on the effect of lowered temperatures on the survival of eggs and fry of the grass carp Ctenopharyngodon idella (Valenciennes)
Authors: Stott B. , Cross D. G.
Published: January 2006

The grass carp has been introduced into many countries and yet self‐sustaining populations are known at four sites only outside its natural range. While the hydrological conditions apparently necessary for spawning are unlikely to occur in the U.K. the requirements of temperature and perhaps water speed occur locally in heated effluents from power stations. Since most heated effluents tend to layer on the water surface, grass carp eggs laid in effluents would quickly be exposed to falls in temperature of up to about 9°C. Experiments carried out in Austria with newly fertilized eggs show that incubation temperatures below 20°C result in large scale deaths, and deformities which lead to death, although 20 h old fry are not adversely affected. Because summer river temperatures seldom exceed 20°C it is concluded that if spawning did occur it would be unsuccessful at most power station sites. At sites where the power station uses a considerable proportion of the available river flow and where the effluent mixes completely downstream, eggs could possibly survive if temperature were the major criterion for successful development.
Routine haematological methods for use with fish blood
Authors: Blaxhall P. C. , Daisley K. W.
Published: January 2006

Some routine haematological methods for examining fish blood are described including haemoglobin estimation, haematocrit, erythrocyte counts, erythrocyte sedimentation rate, total and differential leukocyte counts, and cytochemical staining. Descriptions of stained blood cells are given as are the ranges and mean values for the above tests on brown trout Salmo trutta (L.). These methods are suggested as a possible means of assessing fish health but there is a need for establishing values in health, disease and various stress conditions before their value in diagnosis can be evaluated.
A new occurrence of the parasitical copepod Lernaea cyprinacea (L.)
Authors: Sanderson J. M.
Published: January 2006

The first occurrence of Lernaea cyprinacea (L.) in Scotland is given together with a summary of Lernaea records for Britain including one other unpublished record. Source of the infection is discussed and host fish involved listed. General characters of the Scottish specimens are compared with those of Demaree, Fryer, Hu and Wilson.
Immature digeneans from the alimentary tract of larval and juvenile pelagic stages of haddock, Melanogrammus aeglefinus (L.)
Authors: MacKenzie K.
Published: January 2006

Immature specimens of Opechona sp. are described from the stomach, pyloric caeca and intestine of larval and O‐group haddock, Melanogrammus aeglefinus (L.), taken in the northern North Sea and to the west of Scotland. This appears to be a new host record and possible sources of infection are discussed, together with the occurrence of this normally intestinal parasite in the stomach. It is suggested that these infections may be worth taking into account when considering possible factors contributing to mortalities of haddock and other teleost larvae.
The distribution of mucous cells in the epidermis of the brown trout Salmo trutta (L.) and the char Salvelinus alpinus (L.)
Authors: Pickering Alan D.
Published: January 2006

The mucus of the trout and char was found to contain only one sialic acid, n‐acetyl neuraminic acid (NANA). The concentration of NANA in the epidermis is directly proportional to the mucous cell concentration. In both species the highest concentration of mucous cells occurs on the anterior regions of the body and there are significantly fewer cells on the fins. These findings are discussed in the light of our knowledge of the functions of fish mucus.
Tracking cod Gadus morhua L. in a Scottish sea loch
Authors: Hawkins A. D. , MacLennan D. N. , Urquhart G. G. , Robb C.
Published: January 2006

Equipment has been developed and used to follow the movements of free‐swimming individual fish in the sea. A pulsed ultrasonic transmitter inserted into the stomach is tracked by measuring differences in the time of arrival of the acoustic pulses at an array of omnidirectional hydrophones. The method was used to plot the movements of cod in an enclosed sea‐loch. After an initial phase of active movement the cod became less mobile and adopted a nocturnal cycle of activity.
The reproductive biology of the horse mackerel Trachurus trachurs (L.) in the North Sea and English Channel
Authors: Macer C. T.
Published: January 2006

In the horse mackerel the gametes develop asynchronously and are released in batches. The maturity cycle is characterized by a rapid post‐spawning recovery period and a relatively long period of oocyte maturation. Mean gonad weight reached a peak in June and intraovarian hyaline oocytes occurred from May to August. Determination of fecundity was complicated by resorption of oocytes both before and after spawning, and by the fact that resting and developing oocytes were not clearly separated by size. An estimate of‘potential fecundity‘was obtained by a combination of histology and oocyte measurement. Plankton surveys showed that a major spawning area exists in the Southern Bight of the North Sea, with eggs occurring from May to late August. An estimate of annual egg production was combined with the fecundity data to give an estimate of stock size of about 500 000 tons.
The population structure and growth of juvenile Rhabdosargus holubi (Steindachner) (Teleostei: Sparidae) in a closed estuary
Authors: Blaber Stephen J. M.
Published: January 2006

The population structure and growth rate of Rhabdosargus holubi (Steindachner) in the closed West Kleinemond estuary in south east Africa, from 1971–973, are described. Juvenile R. holubi invade the estuary at a length of 1–2 cm but migrate back to the sea at a length of about 14 cm without attaining maturity in the estuary. Adult R. holubi are rarely encountered in estuaries. The annual growth increment of O group R. holubi was 6 cm, almost all occurring in summer. The growth of Lithognathus lithognathus (Cuvier) was also measured in the same closed estuary and O group fish of this species also grew 6 cm per annum although 1 + fish grew 8 cm per annum.
The settlement, distribution and movements of O‐group plaice Pleuronectes platessa (L.) in Filey Bay, Yorkshire
Authors: Lockwood Stephen J.
Published: January 2006

The pelagic larval stages and the demersal O‐group stage of plaice were sampled in the immediate vicinity of Filey Bay, Yorkshire (54°12′N, 00°16′W), using a modified Gulf V high‐speed plankton sampler and beam trawls. The distribution and movements of these fish were studied from the time of first settlement in May through the period of metamorphosis and the O‐group stage. It was found that the larvae settled in water deeper than 5 m and moved into shallow water following metamorphosis. This established a typical distribution of larger fish in shallower water than the smaller fish. When the fish grew over 40 mm they moved out again into deeper water which leads to a reversal of the lengthdepth distribution. Further movements during the winter months and of the I‐group fish were studied by tagging. It was found that emigration from the nursery ground did not occur until the I‐group stage.
Observations on the distribution, specificity and pathogenicity of the acanthocephalan Pomphorhynchus laevis (Müller)
Authors: Hine P. M. , Kennedy C. R.
Published: January 2006

The distribution, specificity and pathogenicity of the acanthocephalan Pomphorhynchus laevis (Müller) were studied in the River Avon, Hampshire. The parasite occurred in every fish species, but three categories of hosts could be distinguished. Using growth and maturation as criteria of specificity, only chub Leuciscus cephalus (L.) and barbel Barbus barbus (L.) were recognized as its preferred hosts. Parasites occasionally matured in trout Salmo trutta (L.) and dace Leuciscus leuciscus (L.), but none grew or matured in other host species. Changes in the abundance of P. laevis along the river were related to changes in the abundance of both the intermediate host, Gammarus pulex, and the preferred hosts, and its occurrence in fish to the importance of G. pulex in their diet. In the upper reaches of the River Avon and in other localities populations could be maintained at a low level by parasites maturing in trout, and presence and abundance at any site depended upon the presence and abundance of both intermediate and definitive hosts especially and upon the dietary preferences of the latter. The absence of P. laevis from many parts of Britain is nevertheless still inexplicable. The parasite caused local damage to the intestinal wall of fish, the extent of which varied from species to species, but did not affect host growth rate or cause direct mortality and P. laevis cannot be regarded as an important pathogen in the River Avon or any other British River.
Behavioural studies on the lesser sandeel Ammodytes marinus (Raitt) II. The effect of light intensity on activity
Authors: Winslade P.
Published: January 2006

The behaviour of the lesser sandeel, Ammodytes marinus (Raitt), has been investigated at light intensities of 1, 10, 100 and 1000 lux, using a photographic method of recording activity. The level of swimming activity was high at 1000 and 100 lux, declining to a very low level at 1 lux. It was concluded that this was due to the limiting effect of light on feeding. The threshold light intensity for swimming activity in the tank was estimated as being approximately 20 lux but it was considered that in the area of the sandeel fishing grounds the threshold might be higher than this, in the region of 100 lux. The number of hours light per day above 20 and 100 lux at a depth of 15 m in the area of the Outer Dowsing sandbank (53°30′N, 01°00′E) was estimated for the various months of the year. It was shown that during the winter the light intensity does not normally reach 100 lux and only exceeds 20 lux for a few hours each day. It is suggested that this could limit swimming activity and accessibility at this time of year. Measurements were made of the penetration of light into sand and it was concluded that fish which are buried might be able to detect light, possibly via the pineal gland.
Behavioural studies on the lesser sandeel Ammodytes marinus (Raitt) III. The effect of temperature on activity and the environmental control of the annual cycle of activity
Authors: Winslade P.
Published: January 2006

The behaviour of the lesser sandeel, Ammodytes marinus (Raitt), has been investigated at 5, 10 and 15° C, using a photographic method of recording activity. The activity patterns at 10 and 15° C were very similar, there being a high level of swimming activity during the light period, which fell to a low level at 5° C. It was also lower at 10° C at the end of the experiment than at the beginning and it is suggested that this might have been due to an increase in the fat contents of the fish. The feeding rate of the fish was measured and showed a Q10 of 2.08 for the temperature range 5–15° C. The annual cycle of activity of A. marinus is discussed in relation to seasonal changes in food availability, light and temperature, and in the fat content of the fish. It is concluded that after spawning in the December–January period the fish remain buried in the sand until April, because of the limiting effect on swimming and feeding activity of the environmental factors in the intervening period. The proportion of fish available for capture at the start of the fishery in April is related mainly to temperature, but food (as measured by numbers of copepods) light intensity and photoperiod are by then increasing rapidly. After July the fishery ceases and it is thought that this is because the fish have entered an overwintering stage, during which they remain buried in the sand. This phase is also thought to be associated with the maturation of the gonads in readiness for the winter spawning. The factors causing the fish to enter this stage are as yet undetermined but may be related to the attainment of a certain level of fat content.
The growth of Tilapia mossambica Peters (Pisces: Cichlidae) in Lake Sibaya, South Africa
Authors: Bruton M. N. , Allanson B. R.
Published: January 2006

The scales of Tilapia mossambica Peters* from Lake Sibaya show clear rings formed by broken, widely‐spaced circuli in the anterior field. In order to determine the rate and time of scale ring formation, the number of circuli in the marginal increment was determined. Five scales from the pectoral region of 2223 fishes caught at regular intervals over two years were examined. When plotted as histograms, the number of circuli in the marginal increment showed a sharp movement to the left in September–October and again in January, indicating that the rings were formed during these months in the majority of fish examined. Pre‐ and postbreeding feeding migrations, and increases in condition factor, were associated with scale ring formation. Otoliths and opercula were also examined for age determination. Annual length increments were calculated for 450 T. mossambica collected throughout the year, and growth curves plotted. T. mossambica from Sibaya reach maturity after one year at a standard length of about 8 cm in females, and after two years at 10 cm in males. The breeding population had a standard length mode of 11–12 cm in females and 17 cm in males. The maximum final size was about 24 cm.
The relationship of gonad and egg size to weight and age in the European and Chinese races of the common carp Cyprinus carpio L.
Authors: Hulata G. , Moav R. , Wohlfarth G.
Published: January 2006

Gonad development was studied in young carp of the European and Chinese (big‐belly) races. The effects of age and body weight on gonad and egg size were partitioned and the following findings were made: (i) Gonad weight was correlated, in both males and females, with body weight, but proportional gonad weight, i.e. the ratio gonad weight divided by body weight, was independent of body weight, (ii) Proportional gonad weight had reached its maximum value in one year old males, but it more than doubled in two year old females, (iii) Egg size of two year old females was more than twice the size of eggs of one year old females, (iv) The European and Chinese races of carp differed in several aspects of gonad development. In particular, the Chinese matured earlier and their relative gonad sizes were considerably larger, (v) Genetic variation in gonad development was also found within the European race, where faster rate of development is dominant over slower rate. The evolutionary implications of the above differences were discussed.
Some observations on the ecology and the population dynamics of Merluccius angustimanus in the South Gulf ofCalifornia*
Authors: Mathews C. P.
Published: January 2006

A population of Merluccius angustimanus Garman has been discovered in the south‐east Gulf of California, where it is found at 80–120 m in the south of its range (Mazatlan to Altata) and down to 500 m at the northern end of its range (Isla San Pedro Nolasco, north of Guaymas). Studies of the otoliths and catch curves of M. angustimanus show that it lives up to seven years, and may reach 39 cm long (one fish) although it does not usually exceed 32 cm. Using the notation of Beverton & Holt (1959) the following parameters were estimated: L∞= 32.7 cm, K= 0.35, t∞= 0.016, t∞= 7years, Lm= 22.0 cm, M for 3–7 years of age = 0.79, M for 2–3 years of age = 0.79‐0.89. The von Bertalanffy equation for M. angustimanus was:

image
and was shown to give a reasonably close fit to the real growth curve.
Sublethal effects of three ectoparasites on fish
Authors: Vaughan Gene E. , Coble Daniel W.
Published: January 2006

Vulnerability to predation, resistance to high temperature, weight‐length relationships, and fecundity were compared for fish with and without or with light and heavy infestations of three ectoparasites. The fish and parasites were fathead minnow (Pimephales promelas) with anchor worm (Lernaea cyprinaceae); brook trout (Salvelinus fontinalis) with gill lice (Salmincola edwardsii); and yellow perch (Perca flavescens) with black‐spot (Neascus of Crassiphiala bulboglossa). The only sublethal effect found was that of gill lice, which reduced resistance of brook trout to high temperature. None of the three ectoparasites increased vulnerability offish to predation by piscivorous fish.
A survey of red and white muscle in marine fish
Authors: Greek‐Walker M. , Pull G. A.
Published: January 2006

The proportion of the mytomal muscle that comprises red or slow muscle fibres was assessed histologically for 84 species of marine fish. The results are discussed in relation to their mode of life.
A population study of Barbus barbus L. in the River Severn, England
Authors: Hunt P. C. , Jones J. W.
Published: January 2006

Scales from 7071 barbel from the River Severn were used for age and growth determinations. The scales showed clear annual checks which were laid in May when most fish spawned. Scale structure and length frequency distributions showed an almost total absence of 1968 year class barbel. Growth was significantly faster in some sections of the sampling area than in others. Back‐calculated growth analysis showed a systematic decrease in length for each age for females and males in the 1961 to 1967 year classes. Females grew significantly faster than males after four years of age and reached greater ultimate size. There was a preponderance of males between the ages of III and VII and a dominance of females in older age groups. The overall sex ratio of males to females was 2–41: 1. A distinct seasonal growth pattern was shown.
Infection of plaice Pleuronectes platessa L. with Glugea (Nosema) stephani (Hagenmüller 1899) (Protozoa: Microsporidia) in a fish farm and under experimental conditions
Authors: McVicar A. H.
Published: January 2006

One tank of plaice in the W.F.A. Fish Cultivation Unit at Hunterston, known to habour an infection with the microsporidian Glugea stephani, was sampled over a 2 year period and showed a mean level of infection of 49.4 % with an apparent trend towards a decrease. Experimental oral transmission was achieved, without the use of intermediate or carrier hosts, and the dependence of G. stephani on high temperatures was demonstrated. Most fish were able to tolerate the infection, but some mortalities in young fish were attributed to the parasite, particularly in the 2 months following the experimental infection. The parasite in the fish farm is believed to have been introduced with plaice stocks imported from more southern waters.
The ultrastructure of plaice (Pleuronectes platessa) leucocytes
Authors: Ferguson H. W.
Published: January 2006

The leucocytes of plaice were examined and, at a morphological level, in addition to their response to the injection of carbon particles, they could be divided into four main types. Unlike previous reports, monocytes were seen. The neutrophil granules resembled the third granule type described in mammalian neutrophils. Monocytes and thrombocytes were the only cells to take up appreciable amounts of the carbon.
Some general and theoretical considerations on the fish yield of African rivers
Authors: Welcomme Robin L.
Published: January 2006

The factors regulating fish production from river systems remain poorly studied and understood. Rivers conform to physical and chemical laws which determine their morphology. From these laws relationships are calculated which estimate the total length and number of streams of different order on the African continent. Edaphic factors very less than morphological ones and the chemical and physical conditions in the major river channels tend to resemble each other closely. The present catch from African rivers, evaluated from catch statistics, by country and by river system, resembles a theoretical figure derived from the basin area. However, these statistics are drawn only from major fisheries and there remain a very large number of smaller streams whose production does not enter into this calculation. A theoretical approach to this problem is proposed which gives an estimate of annual yield of 530 000 t of fish at present levels of catch. Deviations from the theoretical yield in individual river systems arise from differences in both edaphic and morphological characteristics.
The reproductive cycle of Coregonus lavaretus (L) in Loch Lomond, Scotland, inrelation to seasonal changes in plasma cortisol concentration
Authors: Fuller J. D. , Scott D. B. C. , Fraser R.
Published: January 2006

The reproductive cycle of Coregonus lavaretus (L.) in Loch Lomond, Scotland, was investigated by monthly sampling. Spawing takes place during the first 3 weeks of January, on offshore gravel banks. Males congregate on the spawning‐grounds throughout the spawning period, while ripe females cruise in unisexual shoals in deeper water. Individual females migrate to the spawning‐grounds as ovulation takes place, spawn, and return to deep water. After spawning, the gonadosomatic ratio and somatic condition factor of both sexes decrease until June or July. Gonad recrudescence occurs in males between July and October, and in females between July and December. The somatic condition factor of both sexes rises from its minimum in June or July to its maximum in September. A competitive protein binding assay was used to determine cortisol levels in 0–1 ml plasma samples of individual fish. The lowest cortisol levels occurred in fish caught by seine‐netting and killed immediately by anaesthesia in MS 222 (Sandoz). Seine‐netting and killing by concussion induced higher cortisol levels, in the range of 3–5 ng/100 ml. Cortisol levels in fish caught by gill‐netting for 18 h were 3–6 times higher than in seine‐netted fish, and the method of killing was immaterial in this case. The length of time spent in the gill‐net had no significant effect on cortisol level, but maintenance of the fish in aquaria for 24–80 h elicited high cortisol levels of over 50 μg/100 ml. Post‐mortem delay before blood‐sampling resulted in lowered cortisol levels. Seasonal variations in cortisol level were determined in gill‐netted fish throughout the year, and in seine‐netted fish when available. Cortisol levels were high in both sexes in September; and very high in ovulating females caught on the spawning‐grounds, though not in ovulating females caught off the spawning‐grounds.
Oxygen uptake by rainbow trout blood, Salmo gairdneri
Authors: Eddy F. B.
Published: January 2006

Oxygen uptake rate by rainbow trout red cells was measured in the temperature range 5° to 40° C. Between 5° and 20° C there was a steady increase in rate and at 20° C a maximum rate of 2.5 μl O2/min/ml red cells occurred, followed by a decline in the rate as the temperature increased. A morphological investigation of the red cell was conducted and possible functions of the nucleus in fish red blood cells are discussed.
The occurrence of fin rot in mullet (Mugil cephalus) associated with crude oil contamination of an estuarine pond‐ecosystem
Authors: Douglas Minchew C. , Yarbrough James D.
Published: January 2006

Four estuarine pond‐ecosystems equipped with tidal simulation were established and stocked with mullet, shrimp, and oysters. A 6 month pre‐spill sampling period established a consistently low incidence of disease in the mullet, Mugil cephalus, from all ponds. Following the preliminary study period, Empire Mix crude oil (4.0‐5.0 p.p.m.) was spilled on each of two of the ponds in mid‐July, 1974. Six to eight days following the oil spill all the mullet examined from the treated ponds had varying degrees of fin rot on one or more of their fins. The fin erosion involved primarily the caudal, pectoral, and pelvic fins with the caudal fin the most severely damaged. The degree of damage to the fins varied from a slight discoloration with no visible fraying to complete erosion of all of the fin elements. A gram negative rod tentatively identified as Vibrio sp. is considered the primary pathogen responsible for the fin erosion. Although the condition of the infected fish indicated the possibility of a systemic infection, only a low percentage of the kidney cultures taken from the diseased fish were positive indicating the infection was mostly external. The course of the infection was documented over a 56‐day period following the oil spill. Significantly, 96% of the mullet observed from the treated ponds had some degree of fin damage while only 6 % of those observed from the control ponds had eroded fins. The high incidence of fin rot which occurred in the estuarine‐pond ecosystems did not occur during numerous acute exposures of mullet to crude oil in the laboratory.
Population biology of parasites of striped mullet, Mugil cephalus L. Crustacea
Authors: Rawson Mac V.
Published: January 2006

Class 0 and class 1 striped mullet, Mugil cephalus, were collected from May 1970 to June 1971 to study development, seasonal abundance of parasite populations, and distribution of gill parasites. Crustacean parasites observed were Ergasilus lizae, E. versicolor, E.funduli, Bomolochus concinnus, Brachiella oblonga, Caligus mfimaculatus, Clavella inversa, Lernaeeni–cus longiventris, Argulus funduli and A. chesapeakensis sp.n. Cressey. Cyclipoid copepods initially infected class 0 mullet in late spring and populations were characterized by surges in intensity at 6 to 8 week intervals. Caligoid copepods initially infected class 0 mullet in late summer and fall or appeared only on class 1 mullet. Intensity remained low, but they were observed consistently. Branchiurans were rarely observed on class 0 mullet and occurred consistently at low intensity on class 1 mullet. Study of distribution of five gill parasites indicated a high degree of gill habitat subdivision, but competitive exclusion was not observed.
The effect of tricaine methanesulphonate (MS‐222) on the microhaematocrit of fish blood
Authors: Hattingh J.
Published: January 2006

The effects of the anaesthetic, MS‐222, on the microhaematocrit value of freshwater fish have been examined. Blood containing MS‐222 showed a higher haematocrit value than blood without the anaesthetic and haemolysis occurred in the former after a variable time depending on the concentration. The results are discussed in relation to previous findings.
Effect of stress on blood coagulation and haematology in rainbow trout (Salmo gairdneri)
Authors: Casillas Edmundo , Smith Lynwood S.
Published: January 2006

The effect of short‐term stress on blood clotting times, cell counts, haematocrits, and blood glucose levels was studied in a hatchery strain and wild type rainbow trout, Salmo gairdneri. Blood clotting times declined and thrombocyte counts, haematocrits, and blood glucose levels increased after stress in both strains of trout. The wild type of rainbow trout, however, required less time to recover from the stress than the hatchery strain of rainbow trout. The implications of a stress activated blood coagulation system in fish are discussed.
Investigations on inducing sexual maturity in the male eel Anguilla anguilla L.
Authors: Bleniarz K. , Epler P.
Published: January 2006

Studies on inducing sexual maturity in European eel males have been made. The fish were kept in fresh or artificial sea water at a temperature of 20°C, and hormonal injections were given. Among the hormones used, the positive results were obtained with human chorionic gonadotropin. All the male eel injected with this hormone produced sperm containing living spermatozoa. The quality of sperm of the males kept in fresh water was poorer in comparison with the sperm of the males kept in the artificial sea water.
Seasonal changes in the epidermis of the brown trout Salmo trutta (L.)
Authors: Pickering Alan D.
Published: January 2006

A sexual dimorphism was found in the epidermis of hatchery‐reared brown trout. The epidermis of both male and female fish undergoes rhythmical changes in thickness during successive spawning cycles. For most of the year the male has a significantly thicker epidermis than the female. During the spawning period (December and January) there is a highly significant drop in the concentration of mucous cells in the epidermis of the male brown trout. These findings are discussed in the light of our knowledge of the skin structure in other salmonid fish and in relation to possible hormonal factors influencing the epidermis of teleosts.