bluuebunny/crossref_metadata_2025 huggingface dataset:
Some aspects of the reproductive biology of perch Perca fluviatilis L. Fecundity, maturation and spawning behaviour
Authors: Treasure J. W.
Published: January 2006

Fecundity of perch estimated from a regression of egg. number on fish length varied from 6711 for a fish of 14.5 cm to 77978 for a female of 34. 5 cm. Other independent variables related to egg number were age, gonad weight and somatic weight. Mean egg diameter varied from 0.94 to 1.62 mm. Males matured in their second year at a length of 6 cm and above while all females spawned at age four at a length of 15–18 cm. A proportion of females at Davan spawned one year earlier than at Kinord and were also slightly smaller on spawning. Faster growth of Davan fish may have encouraged earlier maturation. Spawning behaviour is described from film material.
Sexual maturation in female triploid plaice, Pleuronectes platessa, and plaice × flounder, Platichthys flesus, hybrids
Authors: Lincoln R. F.
Published: January 2006

The gonads of immature female triploid plaice (Pleuronectes plafcssa) and plaice × flounder (Platichthys flesus) hybrids produced from cold‐shocked eggs were examined. They were less than half the size of those in diploids of similar age and contained only small numbers of developing oocytes. These were similar both in size and cytological appearance to those in the controls. The bulk of the ovarian tissue was composed of nests of small undifferentiated cells resembling the oogonia in the ovaries of diploid fish. Mature, 5 year old triploid hybrids which had not produced eggs over the previous two spawning seasons were killed in January when the diploid controls were nearing spawning condition. The ovaries of these fish were smaller than those of the controls and contained degenerating oocytes at maturation stage V. The advantage of sterile female triploid fish for fish‐cultivation is discussed.
Tracking Atlantic salmon smolts, Salmo salar L., through Loch Voil, Scotland
Authors: Thorpe J. E. , Ross L. G. , Struthers G. , Watts W.
Published: January 2006

Twenty‐two salmon smolts, Salmo salar L., carrying miniature sonic tags were tracked individually for periods of up to 175 h in Loch Voil, Scotland, during May 1979 and 1980. Activity was predominantly nocturnal, 80% occurring between 21.00 and 06.00 hours, and was apparently undirected. Average velocities during this active interval were 0.6 body lengths per second (bl s−1), with 98 and 93% of the time spent moving at less than 2 and less than 1 bl s−1, respectively. The rates of downstream displacement were 0.04 bl s−1 in 1979 and 0.01 bl s−1 in 1980. The direction of displacement of smolts and of movement of water at a depth of 1 m was positively correlated (P<0.001) and smolt displacement was biassed slightly ahead of water movement. Mean step lengths were 141 and 200 m in 1979 and 1980, respectively. Rates of downstream passage of 327 ICES plate‐tagged smolts released 16.8 km upstream of the fish trap at Clunie dam, Loch Tummel, during the spring migrations of 1975 and 1976 averaged 0.13 bl s−1 in each year: net surface water movement was about 3.7 times this rate during the same intervals. These data are consistent with the model of passive smolt migration postulated by Tytler et al. (1978) and suggest that the active component required to ensure passage through a loch (Thorpe & Morgan, 1978) is very small.
An examination of the fish population in the River Trent, Nottinghamshire using angler catches
Authors: Cooper M. J. , Wheatley G. A.
Published: January 2006

During this study, anglers caught over 580 kg of fish, comprising over 29 500 individuals of 14 species. Nine times as many gudgeon, Gobio gobio, as roach, Rutilus rutilus, were caught. Gudgeon represented 35.94% of the total catch weight compared with 44.64% for roach. The mean total catch per man‐hour was 8.9 fish and the mean catch rate was 176 g per man‐hour. Population estimates for fish longer than 12 cm for all species other than gudgeon and bleak, Alburnus alburnus, gave fish densities of 0.21 fish m−2, the roach population was 0.15 m−2, and that for dace Leuciscus leuciscus, 0.02 m−2. The population density for all sizes of all species caught was estimated to be 2.25 fish m−2.

The fish biomass available to the angler was 447 kg ha−2. The rate of exploitation of the fishery over the period of sampling was high at 17%, representing an annual exploitation rate of 94%.
On the ultrastructure of specific heart granules in teleosts
Authors: Leknes I. L. , Sætersdal T. S.
Published: January 2006

The ultrastructure and chemical reactivity of teleostean specific (‘atrial’) heart granules (SHG) are described. In atrial cells of Glyptocephalus cynoglossus and Gadus morhua, large aggregations of SHG occur in areas of the sacroplasm rich in glycogen and poor in myofibrils. The SHG often appear to be in a process of lysis. A number of heart granules were also noted in atrial cells of Cichlasoma meeki, Pistella riddlei and Sebastes viviparus. although large aggregations were not seen. The mean diameters of SHG in G. cynoglossus and S. viviparus are 110 and 210 nm, respectively. SHG are regularly found in ventricular cells, although less frequently than in the atrium. Ultrahistochemical tests suggest that the teleostean SHG mainly contain proteins.
Gill ventilation and respiratory efficiency of Sacramento blackfish, Orthodon microlepidotus Ayres, in hypoxic environments
Authors: Campagna C. G. , Cech J. J.
Published: January 2006

Respiratory and gill ventilatory responses of Sacramento blackfish to three environmental temperatures (12, 20 and 28°C) and four environmental dissolved oxygen concentrations (130, 90, 65 and 40 torr PO2) were examined to determine physiological strategies of survival in eutrophic lakes and suitibility for culture conditions. Situated in van Dam‐type respirometers, experimental blackfish showed increased gill ventilatory flows from increased ventilatory frequencies and stroke volumes to meet higher respiratory oxygen demands at increased temperatures. Ventilation volumes also increased at reduced environmental dissolved oxygen levels by increased ventilatory stroke volumes alone, except at 28°C where frequency increases were also measured. Oxygen consumption rates remained essentially constant with declining dissolved oxygen, except at 28°C where excitement elevated respiratory metabolism at 65 and 40 torr. Percentage utilization of oxygen increased with temperature from 12°C, but levels at 20 and 28°C were insignificantly different. Contrary to most studies on other species, there was no change in percentage utilization under hypoxic conditions even with 4.7‐fold increases in ventilation volume in excited fish at 28°C. The ability of blackfish to survive in hypoxic waters is quantitatively compared with other species by calculation of a respiratory efficiency index (I), which includes the relationship between ventilation volume and percentage utilization of oxygen under normoxic and hypoxic conditions as well as the half‐saturation value (P50) of the species' blood with oxygen.
Amino acid transport and interconversions in tissues of freshly caught and food‐deprived plaice, Pleuronectes platessa L.
Authors: Moon T. W. , Johnston I. A.
Published: January 2006

Distribution ratios (intracellular/extracellular concentration) of α‐amino isobutyric acid (AIB) and activities of the transaminases of alanine (Ala AT), aspartate (Asp AT), leucine (Leu AT) and glutamate dehydrogenase (GDH) were determined in tissues of freshly caught plaice, Pleuronectes platessa, deprived of food for three months. Liver, red muscle and white muscle demonstrated increased distribution ratios for AIB, while the ratios decreased in kidney and gill with deprivation. Values of the distribution ratio were below 1.0 only in white muscle, with kidney and liver having the highest absolute values. Transaminase activities generally rose with deprivation in all tissues, although the absolute increases were greatest in liver and for the two enzymes Ala AT and GDH. These data indicate that with food deprivation, the role of the liver in amino acid metabolism is maintained and slightly enhanced, while that of the kidney is reduced. Both muscle types (red and white) showed increased water content implicating protein mobilization which could enhance the availability of amino acids for liver gluconeogenesis and metabolite sparing in other tissues during conditions of depletion.
Antigen‐binding cells in the peripheral blood of sockeye salmon, Oncorhynchus nerka Walbaum, induced by immersion or intraperitoneal injectijon of Vibro anguillarum bacterin
Authors: Gosting L. , Mirando D. M. , Gould R. W.
Published: January 2006

We used an immunocytoadherence assay to monitor the response of antigen‐binding cells (ABC) in the peripheral blood of sockeye salmon, Oncorhynchus nerka, after immersion in, or intraperitoneal injection of, Vibrio anguillarum LS 1–74 bacterin. Both methods initiated an elevated ABC response in less than one day; this response persisted one week longer in the injected than in the immersed fish.
Estimation of growth potential by measurement of tissue protein synthetic rates in feeding and fasting rainbow trout, Salmo gairdnerii Richardson
Authors: Smith M. A. K.
Published: January 2006

Protein synthesis in liver, gill and muscle tissue was measured in vivo by constant infusion of 14C‐tyrosine in fed and fasted freshwater rainbow trout, Salmo gairdnerii, at 12° C. Synthesis rates (percentage of tissue protein synthesized per day) were 15‐17% in liver, 4–5% in gill and 0.38% in muscle of fed fish. Liver and gill synthesis rate showed no significant change in fish that had been without food for 15 days, whereas muscle protein synthesis fell to 0.09%. The greater susceptability of muscle protein synthesis to fasting, possibly results from the greater proportion of synthesis retained as growth in this tissue. Growth rates indicate little change in protein turnover in the muscle but increased protein degradation with fasting. The difference between fed and fasted synthesis rates in muscle may be used as a measurement of potential growth rate for a particular species.
The fine structure of the chromatophores and other non‐sensory components of the eye of the blue‐eye, Pseudomugil signifer
Authors: Lanzing W. J. R. , Wright R. G.
Published: January 2006

Aspects of the fine structure of the chromatophores and of other components of the eye of the blue‐eye, Pseudomugil signifer, are presented. Comparisons are made with similar structures of the eye of the mosquitofish, Garnbusia affinis. The blue‐eye has a well organized argentea but no tapetum. Two types of iridophores and melanophores are identified in the weal tract. The uveal tract also includes another presumed chromatophore, the lipopterinophore and an as yet unidentified cell type provisionally named weal polypodal cell. The blue iris of Pseudomugil is thought to be due to the mode of organization of the irideal type β iridophores.
A radiographic estimation of the effect of temperature on gastric emptying time in Sarotherodon niloticus (L) × S. aureus (Steindachner) hybrids
Authors: Ross B. , Jauncey K.
Published: January 2006

A radiographic technique was used to determine temperature effects on gastric emptying time in S. niloticus/aureus hybrids. Stomach evacuation times for 30 g fish fed 3% of their body weight were 8.5 h at 30° C, 10.8 h at 25° C and 16.4 h at 20° C. Hence, there was a negative correlation between stomach evacuation time and temperature. The Q10 between 20 and 30° C was calculated to be 1.92. Similar relationships were found for intestinal evacuation and total evacuation.

The data were used to estimate maximum daily feed intake levels of fish within the size range studied. Levels for 30 g fish were 8.5% body weight at 30° C, 6.6% at 25° C and 4.4% at 20° C. However, the optimum feeding regime should take account of the feeding behaviour of the animals.
Cellular effects of adrenosterone feeding to juvenile carp, Cyprinus carpio L., effect on liver, kidney, brain and muscle protein and nucleic acids
Authors: Lone K. P. , Matty A. J.
Published: January 2006

Different groups of juvenile common carp (3–4 g) were fed diets supplemented with adrenosterone at doses of 1.0, 2.5 and 10.0 mg kg‐1 for 60 days and the effect on food conversion efficiency and cellular growth responses of liver, kidney, brain and muscle were investigated. At the end of the hormone feeding phase an increase of 40–75% was observed in food conversion efficiency. No change in hepato‐somatic and viscero‐somatic index was observed, but brain and kidney weights in relation to body weight was decreased compared with the controls. Variable changes in protein, RNA/DNA, protein/RNA and protein/DNA were seen in liver, kidney, brain and muscle. Feeding of the steroid for 60 days increased the water content of the muscle but ash contents of the muscle were decreased. No change in the total muscle lipids and total nitrogen content were observed. After the removal of the drug from the feed, some of the changes reported were ameliorated.
The histology and ultrastructure of the liver of Atlantic croaker Micropogon undulatus L.
Authors: Eurell J. A. , Haensly W. E.
Published: January 2006

Atlantic croaker, Micropogon undulatus L., were sampled from an estuary and selected offshore sites in the Gulf of Mexico. Liver samples were collected for light and transmission electron microscopy. Histologically, the Atlantic croaker liver parenchyma was arranged in tubular units. The tubules were similar to those of the primitive marine hagfish but contained unique features such as a central sinusoid and intercellular bile canaliculi. This liver structure may represent an evolutionary step from the primitive tubular hagfish liver to the muralium pattern of higher vertebrates. Pigments which may have occurred from disturbances in the normal oxidative pathways of hepatic lipids were also present in the liver.
Changes in selected blood component values of rainbow trout, Salmo gairdneri Richardson, following the blocking of the cortisol stress response with betamethasone and subsequent exposure to phenol or hypoxia
Authors: Swift D. J.
Published: January 2006

Cortisol was undetectable in rainbow trout plasma 24 h after the fish had been injected with betamethasone. This drug is known to suppress ACTH release and, consequently, cortisol production in teleosts. The blood glucose, chloride, sodium, potassium and total protein concentrations were not significantly affected by betamethasone. However, significantly increased blood packed cell volume values were found.

Betamethasone‐injected fish when exposed to hypoxia or phenol had a pattern of blood component changes similar to those found in sham‐injected fish also exposed to the pollutants. These changes in turn were similar to those found in exposed but uninjected and unhandled fish. Suppression of rainbow trout plasma cortisol concentrations with betamethasone apparently has no effect on the fish's short‐term blood component responses to pollutants under the conditions used in these experiments, but does prevent a stressormediated increase in plasma cortisol concentrations.
An aberration in the scale formation of the dace Leuciscus leuciscus (L.)
Authors: Beaumont W. R. C.
Published: January 2006

A first report and description is given of the formation of‘mirror’ scales on dace, Leuciscus leuciscus (L.), Cyprinidae; a similar scale formation in carp, Cyprinus carpio, Cyprinidae is often associated with decreased growth rate, but this was not observed in the dace.
The accumulation of zinc by O‐group plaice, Pleuronectes platessa (L.), from high concentrations in sea water and food
Authors: Milner N. J.
Published: January 2006

The uptake of zinc by young O‐group plaice, Pleuronectes platessa was investigated at levels of high input from sea water and food (Artemia nauplii). Zinc concentrations in the fish were strongly weight‐specific and accumulation effects were distinguished by regression analysis. Sea water was estimated to contribute >10% of the total input up to levels corresponding to high environmental concentrations (c. 0.1 μg Zn ml−1) and food was the major source of zinc up to sea water concentrations of c. 0.6 μg Zn ml−1. A high degree of regulation obtained along the food pathway to the fish although, in the system studied, most of this regulation was effected by the food organism. Regulation of food input explained the lack of variation in zinc levels previously observed in wild populations.
Changes in intestinal fluid transport associated with smoltification and seawater adaptation in coho salmon, Oncorhynchus kisutch (Walbaum)
Authors: Collie N. L. , Bern H. A.
Published: January 2006

The intestinal role in osmoregulatory preadaptation of freshwater‐adapted (FW) yearling coho salmon during smoltification was examined. Measurements of intestinal net fluid absorption (JV) using an in vitro sac preparation showed that JV of FW parr was significantly less than that of either FW or seawater‐adapted (SW) smolts. From two to four weeks following the springtime thyroxin surge, JV increases in FW coho to a level comparable with that observed for SW smolts. JV remained elevated in FW smolts throughout most of the summer and then decreased in the autumn. Two months after the thyroxin peak, intestinal wet weight per unit serosal surface area increases. Coho stunts resulting from premature transfer into sea water had significantly higher JV than that seen in SW smolts. The elevated JV of stunts is only partially explicable on the basis of differences in body weight between stunts and smolts.

Our observations indicate that an increase in intestinal fluid absorption is a preadaptive change associated with smoltification occurring in concert with alterations in renal and branchial osmoregulatory mechanisms. The timing of the increase in JV suggests a phase relationship to the thyroxin surge. This temporal relationship may help to explain the efficacy of using changes in plasma thyroxin levels to predict hatchery‐fish release dates that may optimize eventual seawater survival.
Lead acetate: toxicity without effcts on the locomotor activity of the bluegill sunfish, Lepomis macrochirus Rafinesque
Authors: Ellgaard E. G. , Rudner T. W.
Published: January 2006

The concentration of lead acetate which caused 50% mortality of bluegill in 96 h (96 h LC50) is approximately 400 ppm. Sublethal concentrations of 0.1, 1, 10, 100, 200 and 300 ppm lead acetate did not produce any effects on the locpmotor activity of the bluegill. The observation that lead can reach concentrations which are lethal without sublethal effects on locomotor activity at lower concentrations is unusual and in sharp contrast to studies with other metals (Ellgaard et al.. 1978).
A SCUBA‐diving investigation of Baltic herring (Clupea harengus membras L.) spawning grounds in the Askö‐Landsort area, northern Baltic proper
Authors: Aneer G. , Nellbring S.
Published: January 2006

In a spawning area survey in the Askö area, northern Baltic proper, undertaken in the beginning of summer 1978, 100 randomly established and sampled transects were studied by diving. Herring spawn was found at 45 of the transects. The eggs were usually found on Pilayella littoralis, a filamentous brown algae, at the more exposed transects. Eggs were only found down to a depth of 11 m. In a neighbouring oil spill area spawn were found at only four out of 20 transects. Of eggs taken to the laboratory for hatching, 54% of those from the unaffected area hatched but only 25% of those from the oil spill area.
Proprioceptive endings in the myotomes of the pickerel (Teleostei: Esocidae)
Authors: Ono R. D.
Published: January 2006

Simple spray nerve endings of axons with a large diameter (15 μm) were located in the stratum compactum overlying the myotomal muscles in the pickerels, Esox niger and E. americanus. Based on the location of these nerve endings within the interwoven collagenous fibre matrix comprising the stratum compactum, and on the lack of reactivity to cholinesterase treatment, it is suggested that the endings are sensory in function and may be used as proprioceptors. These putative proprioceptors may aid the pickerel in monitoring the position of the body, (1) during ambush prey capture where the pickerel must lie motionless with as little disturbance in the water column as possible, and (2) in counteracting unwanted hydrodynamic forces such as pitch or roll brought about by sudden stopping of forward movement immediately following prey capture. This is the first report of proprioceptive endings associated with locomotor musculature in teleost fishes.
Changes in the mucous cells of the gills, buccal cavity and epidermis of the nine‐spined stickleback, Pungitius pungitius L., induced by transferring the fish to sea water
Authors: Solanki T. G. , Benjamin M.
Published: January 2006

A histochemical analysis of mucous cells in the gills, buccal cavity and epidermis of the nine‐spined stickleback, Pungitius pungitius L., using alcian blue and PAS, showed that most cells contained more than one type of glycoprotein. In all regions, the cell content of sialylated glycoproteins increased, and of sulphated glycoproteins decreased during adaptation to sea water. The histochemical properties of the cuticle‐secreting cells in the epidermis were less easy to study, but it seems that their content of neutral glycoproteins increased and their content of acid glycoproteins decreased, during adaptation to sea water. Mucous cells were generally less common in seawater‐adapted animals, though in the epidermis of fish kept in sea water for 21 days, there were as many as in the freshwater controls. Sulphated glycoproteins may be more effective than others in freshwater osmoregulation for they are highly charged and could attract cations strongly. They may also help to combat bacterial and fungal infections, and perhaps these are less likely when laboratory fish are transferred to sea water.
Hybridization between Alburnus albidus (C.) and Leuciscus cephalus cabeda R. in Italy
Authors: Bianco P. G.
Published: January 2006

Thirty‐six specimens of hybrid between the cyprinid species Alburnus albidus and Leuciscus cephalus cabeda were recognized from samples collected from five rivers in southern Italy. In the Alento river hybridization was marked and in a single sample of 66 specimens, 23 were found to be hybrids. The identification of hybrids is easy due to the combination of intermediate characters such as body pigmentation, gill rakers, branched rays of anal and pelvic fins, and some proportional measurements. The growth rate of hybrids is intermediate between the parental forms. Males are more numerous than females.
Thermoregulatory behaviour, diel activity and the relationship of spontaneous locomotor activity to temperature in the sea raven, Hemitripterus americanus (Gmelin)
Authors: Reynolds W. W. , Casterlin M. E.
Published: January 2006

Twelve sea ravens, Hemitripterus americanus, were tested individually for three day periods in electronic shuttleboxes to measure their preferred and avoided temperatures, diel activity pattern and relationship of activity to temperature. The fish avoided temperatures below 9°C or above 25°C, preferring temperatures with a central tendency of 15–17°C. The fish were primarily nocturnal, being more active at night than by day. Locomotor activity increased eightfold between 10 and 20°C, but exhibited an anomalous decrease between 14 and 18°C, corresponding to the preferred‐temperature zone, characteristic of maximal summer temperatures in the natural habitat.
Strontium marking of hatchery reared coho salmon, Oncorhynchus kisutch Walbaum, identification of adults
Authors: Yamada S. Behrens , Mulligan T. J.
Published: January 2006

Hatchery‐raised coho salmon were marked with stable strontium prior to their release to sea. Returning marked spawners were correctly identified after 18 months at sea by measuring the Strontium (Sr) concentration of the central region of their scales and vertebrae.
The responses of a perch, Perca fluviatilis L., population to eutrophication and associated changes in fish fauna in a small lake
Authors: Bregazzi P. R. , Kennedy C. R.
Published: January 2006

A number of parameters were measured in a population of perch whose numbers had declined steeply in a habitat subjected to increasing eutrophication, and these measurements were compared with those taken before the population decline. Contrary to expectation, no adaptive responses were identified. The growth rate of perch up to the age of III had only declined slightly, and there was a marked preponderance of young fish. Relative growth rate was consistent despite the population decline. No dominant year class was apparent. Mean instantaneous mortality rate and annual survival rate were calculated, and the length‐weight relationship was analysed. Feeding strategy had not altered since an earlier study. A decline was seen in the percentage of perch maturing at early age. Ripeness coefficients and fecundity estimates were calculated. A previously documented spawning migration was confirmed. The absence of the expected adaptive changes is discussed.
Seasonal changes in the levels of 11‐oxotestosterone and testosterone in the serum of male salmon, Salmo salar L., and their relationship to growth and maturation cycle
Authors: Hunt S. M. V. , Simpson T. H. , Wright R. S.
Published: January 2006

Levels of 11‐oxotestosterone (17 β‐hydroxyandrost‐4‐ene‐3, 11‐dione) and testosterone in the blood serum of individually marked adult male Atlantic salmon held in captivity, were measured by radioimmunoassay at approximately monthly intervals for periods of up to 18 months. In addition to peak concentrations of both hormones shown by all the maturing fish at the time to full sexual maturation during October and November, a majority of maturing fish also showed a significant elevation of 11‐oxotestosterone during the early months of the year. The possible involvement of this early elevation of 11‐oxotestosterone in controlling the mitotic multiplication of spermatogonia is discussed. Weight and length increases expressed as specific values GW and GL and weight to length relationships for the maturing males for each sampling period are presented and compared with those of non‐maturing fish.
Description of two hybrids involving silver bream, Blicca bjoerkna (L.), from British waters
Authors: Swinney G. N. , Coles T. F.
Published: January 2006

This paper describes specimens of naturally occurring hybrids of silver bream x bronze bream and silver bream x roach from Lincolnshire and South Humberside waters.
Influence of bovine growth hormone on the growth dynamics of mosaic muscle in relation to somatic growth of rainbow trout, Salmo gairdneri Richardson
Authors: Weatherley A. H. , Gill H. S.
Published: January 2006

Bovine growth hormone (bGH), administered intramuscularly at 20 μg‐1 every 2 weeks, produced faster somatic growth in rainbow trout fingerlings to approximately 30 cm than in those not receiving the hormone. Both groups were maintained at 12° C, with a photoperiod of 16 : 8 LD, and on ad libitum rations daily. The faster growth was characterized by a controlled increase in input of fibres into the mosaic muscle (which dominates the body tissues by its bulk). It is not known if the enhanced input of fibres is an example of the known ability of the mosaic fibre mass to respond with flexibility and precision to widely differing somatic growth rates, or is a specific consequence of the growth hormone. In other fingerling trout receiving 4‐5% daily rations and consequently growing slowly, bGH did not stimulate growth or evidently modify fibre input dynamics. Body dry weight, and condition (K), though modified by rations and growth rate, evidently had little effect on muscle fibre growth.
Ultrastructure of alarm substance cells in the epidermis of the channel catfish, Ictalurus punctatus (Rafinesque)
Authors: Yoakim E. G. , Grizzle J. M.
Published: January 2006

The cytoplasm of the alarm substance cells in the epidermis of an ostariophysian fish, channel catfish, contained fine homogeneously dispersed fibrillar material. Most cyto‐plasmic organelles were concentrated perinuclearly. The mitochondria were of the tubular type and had matrix granules 30‐50 nm in diameter. The saccules of the Golgi bodies did not form a parallel array and were comparatively widely separated. The nucleus was irregular in shape and had a distinct nucleolus made up of deeply stained granules meshed with areas of less granulation. The nuclear envelope was in the form of a double membrane having a wavy appearance and occasionally it showed invaginations penetrating deeply into the nucleoplasm. Lysosomes and lipid inclusions were encountered in the vicinity of the nucleus. Proteins were demonstrated histochemically, but carbohydrates were not detected. Differences between the alarm substance cells of channel catfish and those of other ostariophysian fish were described and discussed.
Histological observations on the reproductive biology of the haddock, Melanogrammus aeglefinus (L.)
Authors: Robb A. P.
Published: January 2006

Histological observations were made on the changes occurring in the haddock ovary during maturation. The influence of varying food rations on the numbers of eggs released was considered. Oocyte development was found to be a continuous asynchronous process until the beginning of spawing, i.e. stage V when vitellogenesis became synchronized and there was no further initiation of new development. It is suggested that the upper limit of potential fecundity was determined before stage II, however the actual numbers of eggs spawned could still be reduced during later stages in response to a poor food supply.
Effects of polycyclic aromatic hydrocarbons on the proliferation of ectopic thyroid tissue in Poecilia formosa, the Amazon molly*
Authors: Woodhead A. D. , Setlow R. B. , Pond V.
Published: January 2006

A single intraperitoneal injection of any one of several polycyclic aromatic hydrocarbons given to young Amazon mollies induces massive enlargement of the spleen. This enlargement is the result of splenic tissue being partially or wholly replaced by proliferating thyroid tissue. The pharyngeal thyroid gland is stimulated but to a lesser degree. No exuberant thyroid tissue is found at any other extrapharyngeal site. We discuss the possible causes of this finding.
Seasonal variations in the gonad size and the protein and water content of cod, Gadus morhua (L.), muscle from Northern Norway
Authors: Eliassen J.‐E. , Vahl O.
Published: January 2006

Water and protein contents of muscle and gonad index of sexually mature and immature cod of the same size were studied throughout a one‐year cycle. In mature cod, the gonad was found to increase isometrically with fish weight suggesting that the relative energy demand for gonadal growth is independent of fish size. Spawning took place in late March or early April. Similar seasonal variations of water and protein contents of the muscle occurred in both mature and immature cod. In December to February, the protein content reached a maximum and water content a minimum, and in March to April, protein content was low, whereas the water content of the muscle was at a maximum. Since mature and immature cod showed the same variations in body composition, it is suggested that little of the seasonal variations of mature cod can be explained by reproductive processes.
Retinal development and retinomotor responses in perch, Perca fluviatilis L.
Authors: Guma'a S. A.
Published: January 2006

The development of the retina of perch, Perca fluviatilis L., was studied for all developmental stages. The density of cones 100 μm‐1 was found to decrease with age, although their actual numbers increased. All premetamorphosed perch had pure‐cone retinae, the rods developing at, or after metamorphosis. Retinomotor responses were found to commence after metamorphosis when the rods developed. Visual acuity, measured as the minimum separable angle (α), was observed to improve exponentially with age, and its value was found to depend more on the focal length of the lens, than on the number of cones in the retina. The cones in the unspecialized part of the retina were predominantly of the twin type and were related to single cones in a ratio of 4 : 1.
Operant conditioning of feeding behaviour and patterns of feeding in thick lipped mullet, Crenimugil labrosus (Risso) and common carp, Cyprinus carpio (L.)
Authors: Wright D. E. , Eastcott A.
Published: January 2006

Groups of carp and thick lipped mullet quickly learned to operate an underwater trigger for food reward. Single mullet also learned this operant response but single carp did not. Groups of mullet exhibited a higher rate of responding than groups of carp. Mullet appeared to feed in bouts, whereas carp fed randomly during the learning trials. Both species adapted well to six days continuous demand feeding. Grouped and single mullet decreased their feeding at night but carp did not show a diurnal feeding pattern. Feeding responses were found not to be sequences of random events and response rates over the six days were higher in carp than in mullet. In both species, individual fish within a group operated the trigger significantly more often than other fish but all fish took food and gained weight.
Effect of food attractants on appetite and growth rate of gilthead bream, Sparus aurata L.
Authors: Tandler A. , Berg B. A. , Kissil G. wm. , Mackie A. M.
Published: January 2006

Appetite and growth rate were measured in Sparus aurata fed ad‐libitum a basal diet supplemented with either a synthetic mixture of chemicals based upon the analysis of Mylilus edulis, muscle extract, or newly hatched Artemia saline nauplii. These components were tested for their feeding attraction potency, and were added to the basal diet at three concentrations each; 5, 10 and 20 g kg‐1 dry diet.

Appetite, which was defined as ad‐libitum food intake, was significantly affected by the type and concentration of attractant. When the basal diet was supplemented with 10 or 20 g kg‐1 of the synthetic Mytilus edulis muscle extract, it was associated with significantly higher appetite than the basal diet only or the basal diet supplemented with any level of newly hatched Artemia salina nauplii. On the other hand, relative growth rate under the same conditions did not completely conform to the results with appetite. The difference between appetite and growth rate as criteria for the evaluation of food attractants is discussed.
Relation of visual changes to the onset of sexual maturation in the European eel Anguilla anguilla (L.)
Authors: Pankhurst N. W.
Published: January 2006

Eye size was correlated with body length and gonad development in 112 untreated and 33 hormone injected female Anguilla anguilla. A length‐related measure of eye size was developed as an index of sexual maturity. Eels of eye index of 6.5 or less were classed as sexually immature adults, those of < 6.5 as sexually Maturing adults. Structural changes in the eye during maturation were examined. Total numbers of rods increased markedly while density of photoreceptors remained approximately constant. Cone density decreased with degenerative changes occurring. Changes in the eye were found to be essentially complete early in the maturation process.
Vertical distribution and abundance of the Peruvian anchovy, Engraulis ringens, and sardine, Sardinops sagax, larvae during November 1977
Authors: Sameoto D.
Published: January 2006

Horizontal samples taken with the BIONESS at various depths on 13 stations within 115 km of the coast of Peru showed nine species of fish larvae present with the most common of these being, in order of abundance, Leuroglossus stilbius, Sardinops sagax, Diogenichthys laternatus, Merluccius gayi and Engraulis ringens. All the species except S. sagax and E. ringens showed a diurnal migration to the upper 30 m of water at night. The two above species were present in the top 30 m at all times. The size of the larvae of all species did not vary with time, depth or sample location. The numbers of larvae increased with zooplankton m−3 up to 1000 copepods m−3 above which no further increase in larvae occurred. A significant linear relationship was found between the total number of larvae m−2 and biomass and zooplankton m−2, but not between individual species of larvae and zooplankton biomass. Significant correlations were found between E. ringens and seven species of copepods found in the upper 50 m of water.

Polymodal analysis showed that the larval populations of all species, with the possible exception of S. sagax, were made up of more than one sub‐population. From this analysis the length of the spawning season forE. ringens was estimated at 54–68 days.

A significant correlation was found between the numbers of E. ringens larvae m−2 and the maximum concentration of chlorophyll α, as measured with Batfish, in the area of the BIONESS stations. This showed the largest numbers of larvae in areas of the highest chlorophyll concentrations.
The downstream migration of precociously mature Atlantic salmon, Salmo salar L, parr in autumn; its relation to the spawning migration of mature adult fish
Authors: Buck R. J. G. , Youngson A. F.
Published: January 2006

The autumn emigration of juvenile Atlantic salmon, Sulmo salur L. from the Girnock Burn, Aberdeenshire, is shown to be comprised of two components. Precociously mature males and sexually immature fish differ in their dependence on seasonal and biological cues for the release of migratory behaviour. The emigration of ripe mature male parr is shown to follow the entry of mature adult salmon to the stream; when adult fish are prevented from entering the stream, the emigration is induced by seasonal factors. Spent male parr tend not to participate in the autumn emigration. The emigration is considered to be principally an appetitive phenomenon which maximizes the number of precociously mature males attaining sexual contact with adults.
Effects of crowding and availability of food on growth rate of fry in the European and Chinese races of the common carp
Authors: Hulata G. , Moav R. , Wohlfarth G.
Published: January 2006

Fry of the European and Chinese races of the common carp and interracial crossbred fry were grown together in a series of ponds for 28 days after hatching. The degree of crowding and the amount of available natural food were intentionally varied in these experimental ponds. This resulted in a large variation in mean growth between ponds, ranging from 0·1 to 5·2 g per fish during the 28 days growth period. Under conditions of very slow growth, resulting from severe crowding and lack of natural food, fry of the Chinese carp grew several times faster than European carp. At lower densities and when natural food was more abundant, resulting in a faster rate of growth, this difference between the two races disappeared. Crossbred fry between the Chinese and European carp grew faster than either of their parents under all conditions tested.
Protein loci in the Arctic charr, Salvelinus alpinus L.: electrophoretic expression and genetic variability patterns
Authors: Andersson L. , Ryman N. , Ståhl G.
Published: January 2006

In the search for electrophoretically detectable protein loci in the Arctic charr, Salvelinus alpinus L., tissue samples of eye, liver, and muscle from a total of 934 specimens collected at 10 Swedish localities were analysed. General protein staining and specific staining for 33 enzymes revealed 52 detectable loci; 37 of which were considered usable in population surveys. Variability was observed at four loci coding for esterase (est‐2), the liver‐specific form of lactate dehydrogenase (ldh‐3), and the skeletal muscle form of malate dehydrogenase (mdh‐4, 5); genetic variation at loci coding for ldh‐3 and mdh‐4, 5 has not previously been described in the Arctic charr. Relating our results to the multiple locus studies presented in the literature including Arctic charr from Ireland and North America reveals polymorphism at approximately one‐third of the loci studied in the Arctic charr, and the fraction of variable loci does not appear lower in this species than in other salmonids. There were highly significant allele frequency differences between samples. Nevertheless, there was a high degree of genetic similarity among all the populations sampled indicating that they were derived from a relatively recent common ancestor. The results are discussed in relation to the current controversy concerning the number of major evolutionary lines in Scandinavian Arctic charr.
Swimming performance of juvenile sprat, Sprattus sprattus L., and herring, Clupea harengus L., at different salinities
Authors: Turnpenny A. W. H.
Published: January 2006

Sustained swimming performance of juvenile sprat, S. sprattus (29–48 mm s.l.), and herring, C. harengus (46–58 mm) was measured in a laboratory flume over a range of salinities from 18 to 33%0 at water temperatures of 16–19°C. Critical swimming speeds (CSS) of both species, relative to body length, were similar, averaging 10–12 body lengths per second (bl s−1). There was no apparent relationship with salinity.

These swimming speeds are higher than values generally quoted in the literature for sustained swimming of sprat and herring (2–7 bl s−1) and it is concluded that the better performance found in this study was a function of improved fish handling techniques, and of the size of fish used since most other studies have dealt with larger, commercial sized fish.
Digestion of free‐living nematodes fed to fish
Authors: Hofsten A. V. , Kahan D. , Katznelson R. , Bar‐El T.
Published: January 2006

Free‐living nematodes—Panagrellus sp., Turbatrix aceti, Caenorhabditis elegans and C. briggsae—were each fed to the fish Danio sp. and the process of their digestion, in the fish alimentary canal, was studied by light and electron microscope.

Almost no identifiable nematodes were found in the fish gut when the digestion period was 3 h or more, except for buccal capsules of the four studied species, males' spicules of Panagrellus sp. and Turbatrix aceti and egg‐capsules of the Caenorhabditis species. These structures could serve as indicators that the nematodes had been preyed on and digested by the fish.

Differences in the mode of digestion were noticed between the various species of nematodes studied, after a period of 0·5–1 h, in the fish gut. In Panagrellus sp. and T. aceti disintegration of the soft inner tissues occurred mostly at the anterior or posterior ends of the nematode's body, while in Caenorhabditis the majority of digested nematodes were affected at both ends or evenly along the entire body. Digestion seemed to be initiated mostly at the nematodes' body apertures: mouth, anus or cloaca, and vulva which could be due to a more vulnerable cuticle around those areas. Disintegration proceeded from the soft inner parts to the more resistant cuticle that was finally disintegrated. Of the three layers of cuticle the most resistant were the external cortex and the basal layers.
In vitro effects of zinc on lymphoid cells of the carp, Cyprinus carpio L.
Authors: Cenini P. , Turner R. J.
Published: January 2006

Cells from the spleen, anterior kidney, middle kidney, thymus and peripheral blood of common carp were tested in culture at 22°C. Unlike mammals, zinc was not found to be a mitogen but to have a suppressive effect. This was usually detectable at very low concentrations (10−7M), although the degree of suppression varied depending on the organ investigated. Direct toxic effects of the metal were only observed at high concentrations (0·5 × 10−3 m or greater). The use of carp serum supplement rather than foetal calf serum was important in demonstrating these effects.
Photoperiod and diel variations of serum cortisol, thyroxine and protein in goldfish, Carassius auratus L.
Authors: Noeske T. A. , Spieler R. E.
Published: January 2006

Goldfish Carassius auratus L., were held for 1 month on one of four different photoperiods. In those groups with diel variations of serum cortisol and thyroxine (approximately 60%) the variations were entrained to the photoperiod; peak titres occurred around light onset, minimum titres at light offset. Fish held on two of the photoperiod regimes had diel variations in serum protein, however, the pattern was not consistent in relation to any aspect of the photoperiod.
Inter lake comparison of liver morphology and in vitro hepatic monodeiodination of L‐thyroxine in sexually mature coho salmon, Oncorhynchus kisutch Walbaum, from Lakes Erie, Ontario, Michigan and Superior
Authors: Leatherland J. F. , Sonstegard R. A.
Published: January 2006

The hepatosomatic index (HS1) of female sexually mature coho salmon, Oncorhynchus kisutch, from Lake Superior was significantly higher (P<0.01) than in males, whereas that of females from Lake Erie was significantly lower (P<0.05) than in males; there was no significant sex differences in coho salmon from Lakes Ontario or Michigan. Hepatic nuclear areas (HNA) were significantly higher (P<0.01) in males compared with females in fish collected from Lakes Ontario and Erie, but there was no sex differences in HNA of coho salmon from Lakes Superior or Michigan. In all four lakes, hepatocyte cytoplasmic volume was significantly higher (P<0.01) in males than in females from the same lake, and the cytoplasmic volume: nuclear volume ratio of males was corresponding significantly higher (P< 0.05) than in females from the same lake.

Two hepatocytic cell types were evident, termed' light and dark cells, based on the electron density of their cytoplasmic matrix. There were considerable intersex and interlake differences in the relative populations of light ‘and dark’ cells in coho salmon from Lakes Ontario, Michigan, Erie and Superior, and also in the hepatocytic content of lipid, glycogen, mitochondria and ribosomal and smooth endoplasmic reticulum.

There were no sex differences with regard to in vitro hepatic monodeiodination of L‐thyroxine (T4) to triiodo‐L‐thyronine (T3) in salmon from any of the lakes. However, T4 to T3 conversion was significantly lower (P< 0.05) in liver homogenates prepared from Lake Ontario coho salmon than in comparable preparations of liver from Lake Superior, Lake Erie, or Lake Michigan salmon.
Abundance and distribution of Salmincola edwardsii (Copepoda) on anadromous brook trout, Salvelinus fontinalis, (Mitchill) in the Moisie River system, Quebec
Authors: Black G. A. , Montgomery W. L. , Whoriskey F. G.
Published: January 2006

Riviere a la Truite, a tributary of the Moisie River, is probably a focus of Salmincola edwardsii transmission within the system. Differences in prevalence of the copepod on fish between Riviére à la Truite and the main river suggested that up to 41% of anadromous brook trout, Salvelinus fontinalis, in the Moisie River system overwinter in the tributary. Infected fish were generally less than 200 mm long and copepods were attached almost exclusively to the fins and their bases. The primary site of copepod attachment at low intensities of infection was the adipose fin but at high intensities the dorsal fin was most frequently infected. This displacement in attachment location with increased intensity may result in density‐dependent mortality of copepods. Copepods were overdispersed on the host population at each major sampling time and data fit a negative binomial distribution (k ranged from 0.2 to 0.8).
Effect of social interactions on growth rates and conversion efficiency of Arctic charr, Salvelinus alpinus L.
Authors: Jobling M. , Wandsvik A.
Published: January 2006

Mixing of fish from size‐graded groups did not have detrimental effects on subsequent growth performance as compared with control groups. Coefficients of variance for size, within each population, increased with time demonstrating that social interactions were influencing the growth rates of some individuals. Rates of growth of large fish were higher than those of small indicating the growth of the small fish was suppressed below its potential maximum. The results are discussed in relation to those of previous studies and it is concluded that inferences drawn from changes in coefficients of variance have frequently been incorrect.