bluuebunny/crossref_metadata_2025 huggingface dataset:
Bimodal distribution of length of juvenile Atlantic salmon (Salmo salar L.) under artificial rearing conditions
Authors: Thorpe J. E.
Published: January 2006

In 52 populations of juvenile Atlantic Salmon, Salmo salar L., from 14 pairings of wild parents, reared at the Almondbank smolt rearing station between 1973 and 1976 in circular radial‐flow tanks, bimodality in the frequency distribution of length and weight has been characteristic by the first autumn of growth, and has become progressively clearer during the following winter.

The examination of 13 populations showed the modes did not correspond to separate sexes, from four others it was shown they did not correspond to immature fish and precociously mature males. It is suggested that the two modes correspond to subpopulations smoltifying at ages (t) and (t+1) years. The age‐composition of the smolt‐run originating from individual year‐classes of salmon in four Scottish rivers was found to be consistent with stocks having size‐group segregations, at the time of the first smolt emigration, similar to those found among Almondbank experimental material. It is inferred that bimodality of size distribution is the norm among sibling populations of juvenile Atlantic salmon.
Digestion of duckweed (Lemna spp.) by the grass carp (Ctenopharyngodon idella)
Authors: Van Dyke J. M. , Sutton D. L.
Published: January 2006

A feeding trial was conducted in 55‐1 aquaria indoors with the grass carp (Ctenopharyngodon idella Val.) using fresh duckweed (Lemna spp.) as food. Faeces dry weight was closely correlated with dry weight of duckweed consumed based upon a linear regression. From this regression, the estimated true digestibility of dry matter was 65%. Samples of duckweed and fish faeces were analysed for crude protein and gross energy. Van Soest's Analysis was conducted on composite samples of duckweed and faeces. Apparent digestibilities were 80% for crude protein, 61% for gross energy, 72% for organic cell contents, and 30% for organic cell wall constituents.
Comparison between serum values of pond and intensive raceway cultured channel catfish Ictalurus punctatus (Rafinesque)
Authors: Warner Mark C. , Williams R. Whitney
Published: January 2006

Blood serum components in channel catfish (Ictalurus punctatus) were compared between raceway (with low dissolved oxygen) and pond populations. Normal limits were defined for the pond populations, for each of 18 variables, as ± two standard deviations. Carbon dioxide, blood urea nitrogen, total protein, uric acid, creatinine, sodium, and total bilirubin were all lower in fish raised in raceways. Carbon dioxide and sodium had the greatest reductions; all reductions were statistically significant.

Alkaline phosphatase, inorganic phosphorus, calcium, cholesterol, and glucose values were higher in raceway fish, but only alkaline phosphatase and glucose were significantly higher.
Approaches to estimating fish biomass and potential yield in Lake Tanganyika
Authors: Coulter G. W.
Published: January 2006

The annual fish yield of 73 000 tonnes (22.5 kg/ha) from Lake Tanganyika consists primarily of two planktivorous clupeids Stolothrissa tanganicae (Stdr.) and Limnothrissa miodon (Blgr.) and their centropomid predators, three Lates species (Nile perch) and Luciolates stappersii (Blgr.). At the north and south ends of the lake, the Lates spp. have been fished‐up by purse‐seines, and the clupeids and young L. stappersii predominate there. Estimates of pelagic fish biomass may employ (i) catch and fishing effort data (ii) abiotic variables (iii) echo‐sounding surveys (iv) tropho‐dynamic relationships.
The leucocytes of fish: A review
Authors: Ellis A. E.
Published: January 2006

The data available in the literature concerning fish thrombocytes, lymphocytes, monocytes, macrophages and granulocytes is discussed and the dearth of reliable information concerning the functional identity of most fish leucocytes is underlined. The methods of applying nomenclatures to fish leucocytes encountered in the literature is discussed in some detail and found to be unsatisfactory. An attempt is made to simplify the confused and conflicting reports by applying the concepts which have recently arisen in the field of mammalian immunology. Nomenclatures are assigned to cells on a functional and morphological basis where sufficient data exists.

Thrombocytes are responsible for clot formation and are considered to be distinct, separate and unrelated to lymphocytes. Lymphocytes are recognised as immuno‐competent cells though as yet little information exists on their role in immune mechanisms. Recent work is furnishing interesting results in this direction, especially in the origin of lymphocyte populations and their co‐operative responses in immunity. Previous references to monocytes and macrophages in fish are confused and the literature is discussed in the light of the new classification of the Mononuclear Phagocyte System.

Very few experimental data exist concerning granulocytic leucocytes in fish, indeed the presence of such cells with granulocytic functions still requires proof. Cells with morphological similarity to mammalian granulocytes do exist in fish but information essential for an understanding of their role in defence mechanisms is lacking. The state of the literature concerning the eosinophil, basophil and mast cell in fish is so confused that an entirely new approach to a study of these cells is warranted. It is hoped that this review will supply guidelines for future research.
Uptake, metabolism and excretion of the molluscicide N‐tritylmorpholine by the tropical food fish Sarotherodon mossambicus (Peters)
Authors: Matthiessen P.
Published: January 2006

Uptake, metabolism and excretion of radio‐labelled N‐tritylmorpholine (Frescon) were studied in the tropical food fish Sarotherodon mossambicus (Peters). After 55 h exposure to sub‐lethal solutions, concentration factors in whole fish were as high as 1300 (up to 40 mg/kg), at least 80 % of the absorbed activity being unchanged Frescon. Approximately 40 % of this activity was found in bone, 16% in muscle, 16% in gut and 10% in gill. The bile was found to be a route of Frescon excretion, and recovering fish excreted 50% of the absorbed activity in 55 h. The applicability of these results to the field situation is discussed.
Ultrastructure of the chorion and its micropyle apparatus in the mature Fundulus heteroclitus (Walbaum) ovum
Authors: Kuchnow Karl P. , Scott James R.
Published: January 2006

The ovum ‘membranes’ and the micropyle apparatus of mature, extruded ova of Fundulus heteroclitus were examined by scanning electron microscopy. The ovum is covered by a thin jelly coat comprised of a dense mat of 0.3‐0.5 urn fibrils, except for a 50–100 um fibril‐free zone surrounding the micropyle apparatus. The micropyle apparatus consists of a 50–100 um diameter funnel‐shaped vestibule, at the bottom of which is a circular aperture 4–5 μ in diameter leading to the micropyle canal which traverses the entire chorion layer. The inner micropyle aperture, 2–3 um diameter, apposes the inner ovoplasm mass.

The chorion is the major protective coating of the ovum. It consists of a thin (0.4 μm) outer zone, a thicker (9–12 μ), lamellated inner zone with 4–10 lamellae, and sometimes an innermost crystalline zone, varying in thickness from 1–13 μm. The extreme variability in the structure of the lamellated and crystalline zones of the chorion suggests that generalizations concerning ovum membranes can be misleading.
The fish populations in inshore waters of the west coast of Scotland. The food and feeding of the whiting (Merlangius merlangus L,.)
Authors: Gordon J. D. M.
Published: January 2006

The food and feeding of the whiting (Merlangius merlangus) of the inshore waters and sea lochs of the west of Scotland were studied from 1969–1973. Fish and Crustacea were the main food items and their occurrence in the stomachs was clearly related to the size of the whiting and also to their seasonal abundance. The diurnal changes in feeding were also investigated and the results indicated that the size of fish was again an important factor which could affect the interpretation of the seasonal data.
An ultrastructural study of the mitochondria‐rich‘chloride‘cells from the gills of freshwater and seawater‐adapted Tilapia aurea subjected to a pesticide
Authors: Coleman R. , Yaron Z. , Ilan Z.
Published: January 2006

An electron microscopic description is presented of the mitochondria‐rich‘chloride‘cells of the gill epithelium in the cichlid fish Tilapia aurea kept in freshwater or adapted to seawater and injected with the pesticide p,p′DDT. The‘chloride‘cells may have a light or dark (electron dense) appearance. Dark‘chloride‘cells are more common in seawateradapted than in freshwater T. aurea. Characteristic features of‘chloride‘cells include an abundance of mitochondria and an elaborate tubular reticulum, which communicates directly with the basal and lateral membranes of the cells. The apical portion of the‘chloride‘cells is often larger in seawater‐adapted than in freshwater fish. Differences in‘chloride‘cell ultrastructure, which can possibly be associated with a response to different salinities, arc described and discussed. No significant ultrastructural differences are detectable in response to injections of the pesticide.
Spontaneous skeletal deformities in the Zebra Danio (Brachydanio rerio) bred for fish toxicity tests
Authors: Piron R. D.
Published: January 2006

Zebra Danio (Brachydanio rerio, Hamilton‐Buchanan) tropical fish are easily maintained and bred under laboratory conditions; procedures for maintenance and breeding are described. Intensive inbreeding of this fish gave rise to a high incidence of spontaneous skeletal deformities which appear to reflect a genetic defect rather than an environmental stimulus. This finding casts doubt on the suitability of the Zebra Danio for fish toxicity testing.
Aspects of the biology ofScomberomorus maculatus(Mitchill) in Trinidad
Authors: Sturm M. G.de L.
Published: January 2006

A study was made of the biology ofS. maculatus. Results of gonadal examination of 347 males and 409 females suggest spawning takes place from October to April, a period associated with low salinities. First spawning takes place at ages I1 and/or III for both sexes. Sex ratio results suggest spawning may be promiscuous, males outnumbering females. Egg counts from 12 ripe females ranged from 26 057 to 149 736. A period of abundance from May to September may be associated with a post‐spawning feeding migration encompassing the island, possibly in a clockwise direction. Otolith were used to age 817 fish. Opaque and translucent rings are formed yearly. The translucent ring, representing a period of slow growth, is laid down during the spawning season. The fish can live for nine years with females growing faster than males. Growth parameters are compared with those obtained for Brazilian and Florida fish. Mortality rates were investigated and gill nets effected higher mortality rates than beach seines. Full recruitment takes place at age III for gill nets, and ages II and III for beach seines.
A three‐spined stickleback, Gasterosteus aculeatus L. from the North Atlantic
Authors: Jones D. H. , John A. W. G.
Published: January 2006

An unusual occurrence of a three‐spined stickleback, Gasterosteus aculeatus, is described from Ocean Weather Station India in the North‐east Atlantic. Previous records of G. aculeatus caught well offshore are summarised and reasons for these occurrences are suggested. Mention is made of the possibility of sticklebacks breeding in the open ocean.
The use of opercular bones in the study of age and growth in Labeo senegalensis from Lake Kainji, Nigeria
Authors: Blake C. , Blake B. F.
Published: January 2006

Check marks were found on the scales and opercular bones of Labeo senegalensis from Lake Kainji, Nigeria. The scale marks were often indistinct and difficult to interpret, but an attempt was made to determine age from the opercular bones.

At least two check marks per year were found on the opercular bones, one of these occurring during June‐July, and the other during January. The relationship between opercular length and fish total length was plotted logarithmically and back‐calculations of length made.

Problems of interpretation are discussed in relation to possible causes of ring formation.
Annual cyclical changes in the testicular activity of a freshwater teleost, Barbus luteus (Heckel) from Shatt‐Al‐Arab, Iraq
Authors: Bhatti M. Nazir , Al‐Daham Najim K.
Published: January 2006

The testes of Barbus luteus are a pair of elongated structures composed of an anastomosing system of seminiferous lobules. Six spermatogenetic stages of germ cells have been described in the gonad. The endocrine factor lies in the interstitial cells. Spermiation occurs during the months of May, June and July. Fertilization appears to be external. Un‐expelled spermatozoa undergo pycnotic degeneration. The testes show a regular annual cycle which has been described in five arbitrary stages.
The reproductive biology of the dab Limanda limanda (L.) in the North Sea: Seasonal changes in the ovary
Authors: Htun‐Han M.
Published: January 2006

Oogenesis in the dab is described in six easily identifiable stages: oogonium (Stage I), primary oocyte (II), primary vitellogenesis (III), secondary vitellogenesis (IV), tertiary vitellogenesis (V) and hyaline oocyte (VI). The annual reproductive cycle in female dab may be divided into four morphologically and histologically distinct periods: prespawning (October–January), spawning (February–April), postspawning (May–June) and resting (July–September) period.
Sustained swimming speeds and myotomal muscle function in the trout, Salmo gairdneri
Authors: Walker M. Greer , Emerson L.
Published: January 2006

Rainbow trout were trained for 3–4 weeks in a flume at swimming speeds of 1, 2 and 3 l s−1. For each experiment growth rates were estimated and by measuring the hypertrophy of red and mosaic skeletal muscle fibres their function was described at particular swimming speeds and compared with earlier experiments on coalfish using the same technique.

Maximum growth, compared with controls in still water, occurred at swimming speeds of 1 l s−1. At this speed the trout mosaic muscle fibres hypertrophied by 40% but the red muscle fibres showed only a 25% hypertrophy. It is suggested that natural swimming speeds are close to 1Ls−l and the trout mosaic fibres are better adapted for use at this speed in comparison with coalfish white muscle fibres.
A histochemical, light and electron microscopic examination of eel, Anguilla rostrata red and white muscle
Authors: Hulbert W. C. , Moon T. W.
Published: January 2006

The histochemical and structural properties of red and white muscle from the American eel, Anguillu rostrata, are examined. The results suggest that in addition to the classic red and white fibre types, with the generalized pattern of SDH, LDH and myosin ATPase activities, the eel also has two further fibre types. Both are localized directly adjacent to the perimysium separating the red and white muscle masses: one is found only in white myotomes at the lateral line, while the other is unique to red myotomes. During the transition from immature yellow to mature bronze eels, the red muscle myofibrils become partitioned as a result of increases in mitochondria1 numbers and lipid content. It is suggested (1) the myofibrillar partitioning may reflect an altered functional role of red muscle and (2) eel white muscle may provide a portion of the muscular power required to sustain cruising speeds necessary for the long seaward migration of this animal.
The hearing of the Atlantic Salmon, Salmo salar
Authors: Hawkins A. D. , Johnstone A. D. F.
Published: January 2006

The hearing of the salmon, Salmo salar L., was studied by means of a cardiac conditioning technique. Fish were trained to show a slowing of the heart, on hearing a sound, in anticipation of a mild electric shock applied later. The minimum sound level to which the fish would respond was determined for a range of pure tones, both in the sea, and in the laboratory. The fish responded only to low frequency tones (below 380 Hz), and particle motion, rather than sound pressure, proved to be the relevant stimulus. The sensitivity of the fish to sound was not affected by the level of sea noise under natural conditions but hearing is likely to be masked by ambient noise in a turbulent river. Sound measurements made in the River Dee, near Aberdeen, lead to the conclusion that salmon are unlikely to detect sounds originating in air, but that they are sensitive to substrate borne sounds. Compared with the carp and cod the hearing of the salmon is poor, and more like that of the perch and plaice.
Effects of salinity and starvation on the alimentary canal anatomy of the rainbow trout Salmo gairdneri Richardson
Authors: MacLeod M. G.
Published: January 2006

A study has been made of the effects of salinity, starvation and salinity‐starvation interactions on the structure of the alimentary canal of immature rainbow trout Salmo gairdneri Richardson. Intestinal and rectal cross‐sectional areas and the height of the intestinal villi increased with salinity. The thickness of none of the tissue layers measured in the intestine and rectum, including the columnar epithelium and the tunica propria, was influenced by salinity. There was a significant negative correlation between salinity and mucous cell distribution density in both the intestine and rectum. In trout acclimatised to salinities of 15.0 p.p.t. (parts per thousand) and above, there was a high incidence of deep depressions in the columnar epithelium. The oesophagus and stomach were not visibly affected by salinity.

There was a marked decrease in intestinal and rectal cross‐sectional area and height of intestinal villi with starvation except in 32.5 p.p.t. sea water. Mean intestine epithelial cell height decreased with starvation at 32.5 p.p.t. A 48 day period of starvation had little effect on the posterior oesophagus and the cardiac stomach.
Investigations of the toxic mechanisms of ammonia to fish–gas exchange in rainbow trout (Salmo gairdneri) exposed to acutely lethal concentrations
Authors: Smart G. R.
Published: January 2006

Exposure to acutely lethal un‐ionised ammonia concentrations resulted in a 3.3‐fold increase in oxygen consumption. This was associated with increases in ventilation volume, respiratory frequency and amplitude. ‘Cough’ frequency was not significantly affected. Heart rate and dorsal aortic blood pressure were increased and cardiac output was estimated to have more than doubled. Dorsal aortic blood Po2 decreased but no significant changes in erythrocyte number, haematocrit, haemoglobin concentration, blood pH or P50 were observed. Possible toxic actions of ammonia were discussed and it was speculated that, as in mammals, ammonia may act by impairing cerebral energy metabolism.
Swimbladder and skeletal deformations in hatchery bred Spams aurata
Authors: Paperna I.
Published: January 2006

Among hatchery bred Sparus aurata, 5.4% of the offspring of a single parent pair showed severe skeletal deformations coupled with marked growth retardation and pathological changes in the swimbladder. This resulted from extreme proliferation, then hypertrophy, of the cuboidal epithelial cells of the gas gland and proliferation of the rete mirabile. This caused almost complete congestion of the swimbladder air space. The nature of the pathological changes in the swimbladder and the possibility of hereditary origin for both the skeletal and swimbladder deformations are discussed.
Surface folds in superficial epidermal cells of three species of teleost fish
Authors: Hunter C. R. , Nayudu P. L.
Published: January 2006

Scanning electron microscope studies of fish epidermis demonstrate whorled arrangements of microfolds on the surface of superficial epidermal cells in the following species of teleost fish: the guppyfish Poecilia reticulata (Peters), the goldfish Carassius auratus auratus (L.), and the clown anemone fish Amphiprion percula (Lacépède). The pattern is most pronounced in epidermal cells covering the scales, but is also seen in the epidermal cells of the tail and body fins. The whorled pattern was not present on the gill epithelium or the surface of the eyes. These observations differ from transmission electron microscope studies which have described the skin surface as being composed of microvilli.
Fibre types in locomotory muscles of the cartilaginous fish Chimaera monstrosa
Authors: Kryvi Harald , Totland Geir K.
Published: January 2006

The cartilaginous fish Chimaera monstrosa swims slowly by means of pectoral fin movements, and fast by undulations of the tail. In order to compare the fibres in the corresponding muscles, they were studied by histochemistry and electron microscopy. Three fibre types were identified by microphotometry and morphometry. Most of the axial muscles are white fibres, containing little mitochondria and glycogen. Red fibres, with glycogen and about 5 % mitochondria constitute a thin sheet in the axial muscles, composed of one fibre layer only. Pink fibres, with intermediate amounts of glycogen and mitochondria are situated between these two types, but are often not covered by red fibres. Pectoral muscles contain numerous red and intermediate fibres, partially mixed, superficially, and white fibres deeper. Pectoral muscle red fibres contain about 25 % mitochondria, half of which are situated in subsarcolemmal accummulations. The sarcotubular system has T‐tubules at the Z discs, and the terminal cisternae are partially divided by regularly spaced clefts.
The effects of impoundment and regulation upon the stomach contents of fish at Cow Green, Upper Teesdale
Authors: Crisp D. T. , Mann R. H. K. , McCormack Jean C.
Published: January 2006

The stomach contents of 1003 brown trout, 1551 bullheads and 800 minnows taken from the reservoir basin and below the dam, before and after impoundment of the river Tees, were examined. Their composition reflected observations by other workers on river and reservoir benthos, except for the increase in numbers of Hydra and Nais below the dam, and Mollusca, Hirudinea and oligochaetes in the reservoir.

Trout below the dam ate more Ephemeroptera nymphs and Chironomidae larvae but fewer terrestrial casualties after river regulation, whereas bullheads ate more Mollusca but fewer Plecoptera nymphs. In both species Baetidae nymphs increased in numerical importance relative to Ecdyonuridae. Trout, but not bullheads, took zooplankton discharged from the reservoir.

Before impoundment, trout within the reservoir basin ate chiefly benthic organisms and terrestrial casualties. Inundated terrestrial material, mainly earthworms, formed the bulk of their food for at least three years after impoundment, whilst from the second year onwards Chironomidae and, in some years, Gammarus became increasingly important. Zooplankton was taken by all sizes of reservoir trout.

Bullheads within the reservoir basin ate chiefly river benthos before impoundment, with Ephemeroptera and Plecoptera nymphs predominant in older fish, and aquatic Diptera and Coleoptera also important in the fry. After impoundment, Chironomidae and Gammarus were the main items taken by older bullheads, and Chironomidae and micro‐crustacea by the fry. Among all sizes of minnow, Chironomidae, micro‐crustacea and detritus increased in numerical importance after impoundment.
Satiation amount, frequency of feeding and gastric emptying rate in Salmo gairdneri
Authors: Grove D. J. , Loizides L. G. , Nott J.
Published: January 2006

Rainbow trout consumed food in direct proportion to their body weight although the ration increased with temperature. Satiation time varied as 0.031 weight+0.868 temperature+29.145 min. Appetite after deprivation returned in close conjunction with gastric emptying, as judged from serial slaughter studies. Trout trained to operate demand feeders ate less but exhibited feeding rhythms even under conditions of constant illumination. Radiography showed that these rhythms closely paralleled gastric emptying. When offered food diluted with kaolin, the fish compensated by eating more food. This was achieved by increasing feeding frequency caused by a more rapid rate of gastric emptying.
Rhythmic aspects of estuarine migration of hatchery‐reared Atlantic salmon (Salmo salar) smolts
Authors: McCleave J. D.
Published: January 2006

Seasonal, diel and tidal rhythmic activity of hatchery‐reared Atlantic salmon (Salmo salar) smolts migrating through a large estuary was studied by ultrasonic tracking of 46 individuals during two seasons. Prior to 10 May each year most smolts were inactive and remained near shore in shallow water. After 10 May nearly all smolts moved away from the release point into swift water and made rapid seaward progress. Initiation of migration each year occurred when river and hatchery water temperatures rose above 9°C. Migration in the estuary was largely passive drift, and as a result there were distinct tidal rhythms of ground (‘swimming’) speed and net seaward travel. There were no diel rhythms in ground speed or net seaward travel; smolts drifted seaward on the tides during both day and night. Smolts may be slightly deeper during day than night.
Considerations of blood parameters of largemouth bass, Micropterus salmoides
Authors: Clark S. , Whitmore D. H. , McMahon R. F.
Published: January 2006

To evaluate physiological stress resulting from environmental influences, a haematological study of a natural population of largemouth bass, Micropterus salmoides, was undertaken to establish a ‘normal’ blood profile. Several parameters including haemoglobin concentration, haematocrit, erythrocyte count, mean corpuscular volume, mean corpuscular haemoglobin, mean corpuscular haemoglobin concentration, plasma protein concentration and glucose levels were investigated. Haematocrit, haemoglobin, and total plasma protein were positively correlated with fish length. Haemoglobin and haematocrit were positively correlated with fish age while mean corpuscular haemoglobin, concentration was negatively correlated with fish age. Both haemoglobin and haematocrit values were related to erythrocyte counts.
Some haematological responses of normal and splenectomized rainbow trout Salmo gairdneri to a 12% blood loss
Authors: Lane H. C.
Published: January 2006

Anaemia can be induced in Rainbow trout by removing 12 % of the blood volume by cardiac puncture. Recovery from such an anaemia has been monitored in both normal and splenectomized fish. After the bleeding there is a decrease in red cell numbers, haematocrit and blood haemoglobin concentration. Although recovery in normal trout was not complete within 27 days, which was the period of the observations, it was seen as a replenishing of red cell numbers, haematocrit and blood haemoglobin concentration. Mean corpuscular haemoglobin (MCH) and mean corpuscular haemoglobin concentration (MCHC), both depressed by the bleeding, did not appear to recover during the experimental period.

Splenectomy reduced erythropoietic intensity. After bleeding all the parameters studied were more depressed than those found in normal trout, and recovery was not noted. Blood haemoglobin and red cell numbers did not have the same post‐bleeding pattern as normal individuals; MCH and MCHC values remained markedly depressed.

Splenic involvement was further demonstrated by bleeding trout for a second time from both normal and splenectomized groups. In contrast to the response of normal animals, there was a further deterioration of red cell numbers and blood haemoglobin concentration in splenectomized individuals.
The microscopic anatomy of the oesophagus, stomach and intestine of the channel catfish, Ictalurus punctatus
Authors: Sis R. F. , Ives P. J. , Jones D. M. , Lewis D. H. , Haensly W. E.
Published: January 2006

An anatomical study of the digestive tract of the channel catfish revealed that the oesophageal mucosa was longitudinally folded and that secondary folds were occasionally located on the primary longitudinal folds. The infoldings were more numerous near the stomach. The stratified squamous epithelium covering the folds was made up of a basal layer, large mucous cells and simple squamous cells on the surface. The epithelium on the side of the folds consisted primarily of mucous secreting cells. Taste buds were observed between mucous cells on the apical portion of the oesophageal folds and were more prevalent in the cranial part of the oesophagus. The remaining layers of the oesophagus were: a lamina propria‐submucosa, tunica muscularis and adventitia or serosa.

The J‐shaped stomach had two regions: a large sac‐shaped region containing gastric glands and a smaller, nonglandular pyloric region. The large rugae of the stomach became gradually smaller near the pylorus. There was a well developed pyloric sphincter. The mucosa included a simple columnar epithelium, a lamina propria and adventitia or serosa.

The intestine could be differentiated into a thick ascending segment, a descending segment, a thin convoluted segment and a thicker terminal segment, the rectum. Many mucosal folds containing branched villi characterized the ascending segment of the intestine. The descending and convoluted segments contained fewer folds with shorter and less‐branching villi and were smaller in diameter and thinner walled. Descending and convoluted segments were also mildly convoluted and accounted for 80% of the total length of the intestine. An intestinal valve with a sphincter marked the beginning of the rectum. There was an approximately four‐fold increase in the thickness of the tunica muscularis of the terminal segment of the intestine.
The morphology of the accessory air‐breathing organs of the catfish, Clarias batrachus: A SEM Study
Authors: Lewis S. V.
Published: January 2006

The scanning electron microscope (SEM) has been used to study the morphology of the accessory air‐breathing organs of the catfish Clarias batrachus. Although the gross morphology of the dendritic organs, the fan organs and the membrane lining the supra‐branchial chambers differ, the nature of the respiratory surfaces are similar. The gaseous exchange surfaces of all three organs consist of double rows of paired lamellae, a feature strongly indicative of their common origin from the gills. The surfaces of the epithelial cells from the respiratory organs were seen to have numerous small projections consisting of microvilli and short microridges. This is in contrast to the concentric whorls of micro‐ridges on the surface of cells from the interlamella regions of these organs.
New observations on the rodlet cell (Rhabdospora thelohani) in the white sucker Catostomus commersoni (Lacépède): LM and EM studies
Authors: Barber D. L. , Westermann J. E. Mills , Jensen D. N.
Published: January 2006

Light and electron microscopic studies of the morphological features of immature and mature rodlet cells in Catostomus commersoni are presented emphasizing the cells' association with epithelial tissues. The peripheral fibrillar layer is lacking from the apex and from the base of the cell. A cytoplasmic extension from the base may be a feeding mechanism whereby the rodlet cell obtains nutrient at the expense of adjacent cells leaving intercellular spaces often containing myelin figures. RNAase digestion studies demonstrate the presence of RNA in the electron dense rodlet core.

The structure and histochemistry of the rodlets which do not appear to disintegrate upon expulsion from the cell are compared to the cytoplasmic inclusions of both normal fish cells and protozoan parasites. The possible association of the rodlet cell with various pathological conditions is briefly reviewed and the authors conclude that it is premature to disregard the possibility that this cell could be a parasite or infective agent.
Ventilation in rainbow trout (Salmo gairdneri, Richardson) with damaged gills
Authors: Hughes G. M. , Nyholm K.
Published: January 2006

An account is given of damage to the gills of trout which involved reduction in total filament length and consequently reduced respiratory surface area. It was noted that fish with the greatest gill damage tended to ventilate the gills by active swimming (ram ventilation) to a greater extent than those with more normal gills.
Mechanical and biochemical components of apparent specific dynamic action in largemouth bass, Micropterm salmoides Lacéepède
Authors: Tandler A. , Beamish F. W. H.
Published: January 2006

Apparent SDA was defined as the energy expenditure associated with the ingestion of a meal. In the present study apparent SDA was equated to an increase in oxygen consumption above the postabsorptive level subsequent to the ingestion of a meal. The energy cost for physically processing a meal, mechanical SDA, was equated to the oxygen uptake associated with the ingestion of non‐digestible cellulose. The energy utilized by anabolic and catabolic processes associated with the ingestion of a standard diet was identified as biochemical SDA. Apparent, mechanical and biochemical SDA were each positively related to the energy intake of the standard diet. Apparent SDA expressed relatively to energy ingested equalled 10·5% and was independent of the caloric content of the meal. Mechanical SDA increased asymptotically with ingested meal size and energy content. Relative to apparent SDA, mechanical SDA decreased with meal size, suggestive of an enhancement in efficiency. Biochemical SDA rose exponentially with increase in ingested energy, reflective of the cost for growth and catabolism.
Growth and production of some important species of fish in a Mexican coastal lagoon system
Authors: Warburton K.
Published: January 2006

In terms of biomass, the three dominant fish species in the Huizache‐Caimanero lagoon system during 1975–76 were the mullet Mugil curema, the anchovy, Anchoa panamensis and the catfish, Galeichthys caerulescens. Peaks in the abundance of the secondary predators occurred at the end of the wet season (September‐October), while pelagic forms and members of the centropomid‐gerreid association (Warburton 1968a) were most common during November‐February and December‐February respectively. Twelve species, including the ten having the highest overall mean biomass, were selected for growth and production studies. Lagoon‐specific differences in the patterns of growth and recruitment of several species were observed. The total estimated annual fish production in Caimanero lagoon was 34·48 g m−2 y−1, with M. curema contributing 9·36 g m−2, A. panamensis 9·24 g m−2 and G. caerulescens 6·15 g m−2 (maximum estimate). Mean turnover ratios (annual production: mean biomass) were 3·25 (demersal species), 8·44 (pelagic species) and 4·48 (all species). Implications for possible fishery and aquacultural expansion are discussed.
Biology of young grey mullet, Mugil cephalus L., populatioins in a coastal lagoon in Sri Lanka
Authors: De Silva S. S. , Silva E. I. L.
Published: January 2006

The biology of young grey mullet, Mugil cephalus L. populations of a coastal lagoon—the Negombo Lagoon on the West Coast of Sri Lanka was studied from October 1976 to March 1978. The relative abundance of fry were found to vary from month to month, with peaks occurring in December‐January, May and September‐October, coinciding with the end of rainy seasons. It was found that the young fry tended to migrate into the lagoon at a size of about 10–20 mm, most frequently between 15–20 mm in length, by which time they were fully scaled. The young fry after a period of growth in the shallow areas of the lagoon, when they reached a size of 30–35 mm, emigrated into the deeper waters of the lagoon. The rate of growth, as computed from length frequency distribution studies, was found to be around 0.24 mm day−1. Results of diurnal surveys showed a movement of the larger size fry into shallower waters during the hours of darkness and this movement appears to be independent of the tidal cycle. It is postulated that the cause of this migration is to escape from predators, chiefly piscine. Investigations of the meristic characters indicated that the young fry which migrated into the lagoon at different times of the year probably originated from a single spawning stock.
The effects of population density on fecundity and fertility in the guppy, Poecilia reticulata (Peters)
Authors: Dahlgren B. T.
Published: January 2006

Experiments were performed to examine the influence of population density on the fecundity and fertility in the guppy, Poecilia reticulata. The frequency of females with only ova or with different combinations of reproductive units and developmental stages in the ovary was significantly different between different densities but not between females with one and two gestations from the same population density. The ovarian width of females with one gestation from the lowest density was significantly larger than in the highest population density. Gonad length and height and ovarian volume of females with two gestation periods were larger in the lowest compared with the highest density. After one gestation, females at the lowest population level had greater ovarian length, height, gonad weight, width and volume compared with those from the higher density. Ovarian length, height and volume and gonad weight were also significantly greater among females of two gestation periods in the lowest than in the second lowest density. The average gonadosomatic ratio was highest in the lowest population density. A significant correlation was found between gonad volume and total body weight and between gonad volume and ovarian weight of females at every population level. This was also the case when ovarian weight vs. total body weight was examined in each population density. Only at the lowest population level was there a significant correlation between fecundity and total body length and between fertility and body length. A significant relationship was also found between gonad volume and total body length and between gonad weight and body length at the same population level. No significant difference of fecundity and ovum size was found between females of one and two gestation periods from the same density. Fecundity and fertility were significantly higher among females of one and two gestation periods from the lowest than from the highest density.
Studies on scale structure in the common goby Pomatoschistus microps Krøyer
Authors: Fouda M. M.
Published: January 2006

A histological study on scale structure in the common goby, Pomatoschistus microps (Krøyer) has established a similarity to other teleost scales, but yielded two new findings. First, the osseous layer of the scale was formed of successive and parallel calcified bands that may reflect a rhythm in scale growth. Second, extracellular matrix vesicles (100–200 nm) were identified by electron microscopy, at the calcifying area in the anterior growing edge of the scale; distribution of these vesicles corresponded closely to the pattern of scale calcification. A proposal on the mechanism of growth and calcification of scale has been made. The surface topography of the scale has also been examined by scanning electron microscopy. The raised edge of the circulus is formed of minute knobs, which may be used as criterion in fish taxonomy.
‘Ferox’ trout, Salmo trutta L. of Loughs Mask and Corrib
Authors: Went A. E. J.
Published: January 2006

Sets of scales with the relevant information were collected by the Irish Specimen Fish Committee from large or specimen brown trout taken by angling from Loughs Mask, and Corrib. The relationship between lengths and age were determined for those fish for which the necessary information was available. It was concluded that those fish destined to become specimens (10 lb or over in weight) had adopted a fish‐eating habit to enable them to maintain a high rate of growth.
Temporal variations in the skin of Atlantic salmon Salmo solar L.
Authors: Wilkins N. P. , Jancsar S.
Published: January 2006

The thickness of the skin of Atlantic salmon increases throughout the first two years of life. This increase involves, principally, an increase in the connective tissue of the dermis, and occurs independently of sexual maturity. The concentration of mucous cells in the epidermis changes seasonally, being least during the winter period. No sexual dimorphism is observed in these features among sexually immature fish. The epidermis of precociously mature male parr is thicker and contains more mucous cells than that of sexually immature individuals.
A scanning electron microscope study of the gills of the air‐breathing catfish, Clarias batrachus L.
Authors: Lewis S. V.
Published: January 2006

Using the scanning electron microscope, the gills of the air‐breathing catfish, Clarias batrachus, have been studied. The overall morphology of the gills are similar to other teleosts. In contrast to water‐breathing species, however, microridges are absent from the surfaces of the secondary lamellae and only short microvilli are present. Long, convoluted microridges are present on the epithelial cells of the gill filaments. The possible roles of these structures in relation to water flow are discussed.
Effects of temperature on the growth and survival of the European eel, Anguilla anguilla L.
Authors: Sadler K.
Published: January 2006

Experiments to determine the growth rate of eels (Anguilla anguilla L.) at different temperatures are described and show the optimum temperature for growth to be 22–23° C. The ultimate upper lethal temperature was found to be 38° C and the critical thermal maximum varied from 33 to 39° C for fish acclimated at 14 to 29° C. An attempt was also made to determine lower lethal temperatures. Eels enter a state of torpor at temperatures varying from 3° C for fish acclimated at 29° C to less than 1° C for fish acclimated at 23° C or below. The results have been used to estimate the growth rates expected from eels cultured in power station cooling water using different types of temperature control.
Growth hormone binding to tissues of normal and stunted juvenile coho salmon, Oncorhynchus kisutch
Authors: Fryer J. N. , Bern H. A.
Published: January 2006

The premature transfer of juvenile Coho salmon into seawater results in high mortality and a reduction of growth (stunting) of a significant portion of the population while the remainder of the salmon continue to grow normally. Binding studies were conducted with I25I‐labelled tilapia (Sarotherodon mossambicus) growth hormone (tGH) to determine if differences in specific binding of tGH existed in membrane preparations of tissues of stunted and normal coho salmon. Membrane preparations of both liver and gill of stunted salmon obtained from stocks in California, Washington and British Columbia and kidney membrane preparations obtained from stunted salmon in California exhibited deficiencies in 125I‐labelled tGH‐binding sites compared to corresponding membrane preparations of normal smolts. These results indicate that stunted coho salmon have a decreased ability to bind GH which may be reflected in perturbations in GH‐mediated processes.
Spawning kinetics in the gilthead sea‐bream, Sparus aurata L. after low doses of human chronic gonadotropin
Authors: Zohar Y. , Gordin H.
Published: January 2006

This paper reports the temporal pattern of hormonally induced spawning in Sparus aurata females reared in captivity. A low dose of human chorionic gonadotropin (100–400 i.u. kg−1 body weight), administered to females with oocytes in the last stages of vitello genesis, induced a daily cycle of maturation, ovulation and spawning of fertilizable eggs. This cyclic pattern lasted for a period of 4–100 days. In fish injected with saline and most of the untreated fish, all vitellogenetic eggs underwent rapid atresia.
Larval anisakids and other helminths in the hake, Merluccius gayi (Guichenot) from Chile
Authors: Carvajal J. , Cattan P. E. , Castillo C. , Schatte P.
Published: January 2006

One hundred and twenty hake Merluccius gayi caught off central Chile were examined for helminth parasites. Sixty hake were kept in ice from the catch of a trawler were examined upon arrival at port, while the other 60 hake were dissected on board immediately after collection. Ninety one per cent of hake were infected with one or more species of the following helminths: trypanorhynch plerocerci of Grillotia dollfusi Carvajal, 1971; adult worms of the genus Clestobothrium; larval nematodes of the genera Anisakis and Phocanema; 86% of the total were infected with Anisakis sp. and 42.5% with Phocanema sp. Infection with larval nematodes increased with length of the fish and there was a greater incidence of infection among the females. There was a greater frequency of occurrence of the parasites in the viscera than in the musculature.
Selective haematological parameters in steelhead trout, Salmo gairdneri Richardson
Authors: Meade T. L. , Perrone S. J.
Published: January 2006

Fifteen steelhead trout, Salmo gairdneri, were assayed for selective blood parameters. The trout were reared under flow‐through conditions at the salmonid aquaculture facility at the University of Rhode Island. The means of the measured haematological parameters were: pH, 7·59 ± 0·05; pCO2, 8·5 ± 1·05 mmHg; HCO3‐, 11·9 ± 1·9 meq/1; Ferri‐Hb, 21·7 ± 2·0%; C1‐, 147 ± 17·8 meq/1; Hct, 30·7 ± 4·8%.
Environmental stress and bacterial infection in channel catfish, Ictalurus punctatus Rafinesque
Authors: Walters G. R. , Plumb J. A.
Published: January 2006

Channel catfish, Ictalurus punctatus, were injected intraperitoneally with a sublethal dose of Aerornonas hydrophila and then stressed for 144 h by being maintained either in a dissolved oxygen concentration of 1·5 mg/1, 1·2 mg/1 total ammonia, and/or 6·5 mg/1 free CO2 with a continuous inflow of water. A significant difference in percentage of mortality was noted between treatments (P < 0·05). The trunk kidneys of surviving stressed fish had significantly higher total bacterial counts than non‐stressed controls. A. hydrophila was isolated from 67% of the stressed fish and 9% of the control fish. Edwardsiella tarda, apparently endemic in the population, was isolated from 43% of the stressed fish and 7% of the control fish. Histopathological lesions were in the gills, liver, spleen, trunk kidney, and head kidney of stressed fish, but not control fish.
Gastric evacuation in plaice, Pleuronectes platessa L.: effects of dietary energy level and food composition
Authors: Jobling M.
Published: January 2006

Using a volume dependent model of evacuation, the effects of dietary energy level and source upon gastric emptying were examined. Diets containing small amounts of energy were evacuated from the stomach more rapidly than those with a higher energy content. When the data is examined with respect to the evacuation of energy from the stomach and is plotted as √Energy = ce−me Time; the rate of evacuation (me) is seen to be independent of energy level and the composition of the diet.
Reproductive biology, length‐weight relationship and relative condition of pond raised Tilapia zilli (Gervais)
Authors: Dadzie S. , Wangila B. C. C.
Published: January 2006

In ‘runted’ populations of Tilapia zilli positive correlations were found between maturation stages and the following: gonadosomatic index, gonad weight, fish weight and fish length. The minimum size at maturity was 9·0 cm in males and 11·0 cm in females. The mean fecundity in the ‘stunted’ females was 2359 eggs and it increased with length (L) weight (HO and depth (D) of the fish. There was, however, no correlation between fecundity and egg size. The results indicated that growth in this ‘stunted’T. zilli population was not isometric. The relative condition factor (Kn) which approached one indicates good condition.
The occurrence of black spots in the tongue sole, Cynoglossus browni Chabanaud, due to nematode eggs (Capillaria spinosa) previously described in the shark Carcharhinus mttberti Müller & Henle
Authors: Van Banning P.
Published: January 2006

The occurrence of black spots in fillets of the tongue sole, Cynoglossus browni, due to the occurrence of nematode eggs is reported. The eggs were found to be identical with Capillaria spinosa egg type previously described from the shark, Carcharhinus milberti. The presence of the capillarid eggs in the tongue sole is discussed as a new observation in relation to gaps in knowledge of the adult nematode and the biology of the shark.