bluuebunny/crossref_metadata_2025_split huggingface dataset:
Age, growth and feeding in the ballan wrasse Labrus bergylta Ascanius 1767
Authors: Dipper F. A. , Bridges C. R. , Menz A. 
Published: January 2006

A study of the age, growth and feeding of the protogynous wrasse Labrus bergylta (Teleostei: Labridae) was made on 25 male and 316 female specimens taken from the southern coasts of the Isle of Man from October 1972 to October 1974. Age determination and back‐calculations for length were made from the opercular bones. The oldest male and female specimens were 29 and 25 years old respectively. The growth curves showed only a slight increase in growth rate after sexual inversion, and a pattern of slow irregular increase, with no pronounced levelling off in old fish. The time of sexual inversion varied widely: intersexual specimens of 5 and 14 years were found. The youngest functional male was 6 years old. The weight/length relationships of males and females were very similar and the following equation, derived from all individuals, was used to calculate weights for age utilizing the back‐calculated lengths:

image
The mouth, pharyngeal teeth and gut length to fish length ratio (0.622) suggested an omnivorous diet. Analysis of gut contents confirmed this, with decapod Crustacea, isopods and molluscs the dominant food items. There were seasonal changes in feeding intensity and composition of the diet, related to temperature changes, onshore‐offshore migration patterns, availability of food items, and changes in habitat associated with maturation.
'Siamese‐twins’ in Sarotherodon mossambicus
Authors: Hulata G. , Rothbard S. 
Published: January 2006

Tilapia mossambica (Sarotherodon mossambicus (Trewavas, 1973)) a female mouthbreeding cichlid, Fryer & Iles (1972), has recently been introduced to the Fish and Aquaculture Research Station, Dor, from South Africa. They were found to spawn freely in aquaria. Females carrying eggs in their mouth are routinely transferred to small containers, and when the fry are released they are separated from their mothers.In one batch of 209 fry we found two fry connected at their ventral part to the same yolk sack. These' Siamese‐twins' survived for 8 days in an aerated glass jar. During this period the yolk sack was absorbed and they became connected at their abdomens. (Plate I). Similar cases were previously noted in sharks, trout, Salmonidae spp., guppy, Poecilia sp. and Haplochromis sp. (Reichenbach‐Klinke & Elkan (1972) and Reichenbach‐Klinke (1972)).
Spontaneous and gonadotropin‐induced ovulation in the goldfish, Carassius auratus L: effects of external factors
Authors: Stagey N. E. , Cook A. F. , Peter R. E. 
Published: January 2006

Spontaneous ovulation in goldfish is synchronized with photoperiod and influenced by water temperature and aquatic vegetation. As the latency to ovulation from injection of HCG is highly temperature dependent, the finding that ovulation occurs at approximately the same time of day at temperatures from 12° to 26° C suggests the time of the endogenous preovulatory gonadotropin surge may change with the temperature. The time of spontaneous ovulation adjusts to a reversed light:dark cycle within 2 weeks; some 4–6 h shifts in a single light:dark cycle modify the time of ovulation.Few sexually mature females kept under long photoperiod (16L:8D) and transferred from cold (13 ± 1°C) to warm (21 ± 1°C) water ovulated spontaneously. Exposure to artificial aquatic vegetation for as little as one light phase significantly increases the proportion offish ovulating in warm water. Fish kept in cold water without vegetation do not ovulate; the addition of vegetation induces ovulation, although the response latency is longer than in warm water. Aquatic vegetation may be an effective stimulus for ovulation in other teleosts which spawn on this substrate.
Progressive changes in haematology and tissue water of sexually mature trout, Salmo gairdneri Richardson during the autumn and winter
Authors: Lane H. C. 
Published: January 2006

Rainbow trout of the Kamploops variety were sampled at intervals from October to the end of March. During this period a decline was noted in red cell count, haematocrit, haemoglobin concentration and plasma osmotic concentration. Increases were seen, however, in mean cellular volume, mean corpuscular haemoglobin, mean corpuscular haemoglobin concentration and the water content of liver and dorsal muscle. Sexual differences were found in all values with the exception of mean corpuscular haemoglobin concentration and the water content of both tissues. Males always had higher values in those parameters in which sexual differences were noted. All trends, with the exception of male haemoglobin and mean cellular volume and female mean cellular volume and osmotic concentration, were significantly linear.None of the findings in this study could be correlated with temperature or photoperiod. Neither could the declining plasma osmotic concentration be correlated with the rising mean cellular volume or tissue water content. However, correlations were noted between haemoglobin and haematocrit, red cell count and haematocrit and between osmotic concentration and haematocrit. A negative correlation was seen between mean corpuscular haemoglobin concentration and mean cellular volume.
A biological analysis of eel catches, Anguilla anguilla L., from the lagoons of Lesina and Varano, Italy
Authors: Rossi Remigio , Villani Paolo 
Published: January 2006

A study of eel catches from Lesina (444 specimens) and Varano lagoons (325 specimens), in southern Adriatic, Italy, was made. Male silver eels in Lesina ranged from 33.4–51.5 cm in length, with a mean of 42.6 cm; from 50–240 g in weight, with a mean of 141 g and were 1.5–6.5 years old with a mean of 2.5 years. The average length of male silver eels in Varano lagoon was 40.5 cm (range 31–48.5 cm); the average weight was 122 g (range 80–220 g)and a mean age of 2.6 years (range 1.5–7.5 years).The females are bigger, heavier and older than the males with, in Lesina, a mean length of 61 cm (range 50.9–74.3 cm), a mean weight of 438 g (range 240–730 g) and a mean age of 3.4 years (range 1.5–6.5). The average length of Varano female silver eels was 58 cm (range 50.8–72.5 cm), and the average weight was 383 g (range 225–840 g). They were 1.5–7.5 years old, with an average of 3.8 years. Female silver eels were only 20% of the population at Lesina and 10% at Varano.In comparison with the silver eel populations of the North Adriatic lagoons, the North Sea or the Atlantic Ocean, the silver eels of Lesina and Varano show a greater growth rate, are younger and have a sex ratio in favour of the males.The water temperature, higher than in other countries, could be an important factor affecting the differences in age and growth rates between Lesina and Varano silver eels and those of other waters.
The effect of stress on the stomach of the European eel, Anguilla anguilla L.
Authors: Peters G. 
Published: January 2006

The gastrointestinal tract is a system that is very sensitive to stress‐like conditions in mammals. Fish display physiological reactions to stress that are fundamentally similar to those of the‘General Adaptation Syndrome’ in higher vertebrates. An investigation was therefore undertaken to determine if morphological changes equivalent to those affecting the stomachs of mammals also occur in fish under stress.Conflict for social dominance served as the stressor. The unavoidable confrontation with a dominant fish in a tank proved to produce great stress for the subordinate eel. This was demonstrated by a number of physiological and haematological parameters.Stressed eels have shrunken stomachs, the consistency of which is translucent and soft. The mucous membrane folds flatten or disappear. The mucous epithelium atrophies and during this process numerous residual bodies appear. The cell‐to‐cell contact loosens. The gastric glands degenerate developing large intracellular cavities, vacuolated ER and swollen mitochondria. The connective tissue proliferates replacing the necrotic glands. The submucosal vessels contract, thereby disturbing the circulation.The consequences of the gastric atrophy (increased self‐digestion, reduction of the immunological barrier, interference with protein digestion, endocrine function, etc.) are discussed.
Bioassay of insulin activity of pancreatic tissue in active and aestivated African lungfish, Protopterus annectens (Owen)
Authors: El Hakeem O. H. , Babiker M. M. 
Published: January 2006

The insulin activity of the pancreatic tissues of free‐swimming and aestivated African lungfish, P. annectens (Owen), was bioassayed against standard insulin in rabbits. The hepatic glycogen content and plasma glucose concentration in free‐swimming and aestivated lungfish were also estimated. The liver glycogen content was 64·47 ± 6·32 and 7·19 ± 2·68 mgg−1 net wt and the plasma glucose concentration was 37·62 ± 4·22 and 6·39 ± 1·29% in free‐swimming and aestivated lungfish, respectively.Extracts of pancreatic tissue of the lungfish produced a dose‐dependent decrease in the plasma glucose concentration in rabbits. The magnitude of the decrease in plasma glucose concentration produced by extracts from aestivated specimens was significantly smaller (about 26%) compared to that produced by pancreatic extracts from free‐swimming active lungfish (about 37%). The insulin activity of the pancreatic tissue was 0·82 ± 0·02 and 1·27 ± 0·25 iu mg−1 dry pancreatic tissue weight in aestivated and free‐swimming lungfish, respectively.
Some potentials and limits of the leucocrit test as a fish health assessment method
Authors: Wedemeyer G. A. , Gould R. W. , Yasutake W. T. 
Published: January 2006

The sensitivity of the leucocrit as a stress tolerance and fish health assessment method was evaluated by subjecting juvenile coho salmon, Oncorhynchus kisutch, or steelhead trout, Salmo gairdneri, to standardized crowding, handling, temperature and disease challenges. The leucocrit was a sensitive indicator of the physiological stress resulting from crowding at population densities of 0·2–0·4 kg l−1, and to the stress of handling and to temperature changes. It was relatively insensitive to physiological sampling procedures which supports its continued development as a stress assessment method.In the case of fish diseases, subclinical or active Renibacterium salmoninarum and Yersinia ruckeri infections had essentially no effect on leucocrit values. In contrast, active Aeromonas salmonicida infections significantly depressed the leucocrit. However, no change was seen during the subclinical (incubation) phase prior to the development of an epizootic. Thus, the potential of the leucocrit as a fish health assessment method appears limited.
A cytochemical, light and electron microscopical study of the leucocytes of the adult river lamprey, Lampetra fluviatilis (L. Gray)
Authors: Page M. , Rowley A. F. 
Published: January 2006

The morphological features of the leucocytes from the blood of the river lamprey, Lampetra fluvimilis, were studied using light and electron microscopy. Four cell types were identified, namely granulocytes, lymphocytes, monocytes and thrombocytes. Enzyme cytochemical tests were also performed for the detection of acid phosphatase, β‐glucuronidase and peroxidase. All the leucocyte types were positive for acid phosphatase and β‐glucuronidase, to a variable extent, with the greatest activity seen in the granulocytes. None of the leucocyte types however, contained any peroxidase activity.Only one type of granulocyte was found and this appears to be analogous to the mammalian neutrophil/heterophil. Characteristically, it has a cytoplasm containing a large number of morphologically heterogeneous granules (0.07–0.40 um in diameter). It is suggested that these granules, rather than belonging to several subpopulations, are in fact part of a single maturation series.The results of this study show that precise identification of lamprey leucocytes can only be achieved using a combination of ultrastructural and cytochemical techniques.
Cost of prey capture, growth rate and ration size in pike, Esox lucius L., as functions of prey weight
Authors: Hart P. J. B. , Connellan B. 
Published: January 2006

Prey intake, amount of time feeding, pursuit and manipulation times and growth rate were studied in the pike, Esox lucius, in relation to prey weight. Predator and prey were observed in tanks at 15°C and with a 14:10 h LD photoperiod. A total of 444 captures were recorded from five 1 g prey weight groups varying from 0 to 4.9 g. Ten pike were used weighing between 50 and 149 g.As prey weight increased, the number and weight of prey consumed decreased as did the time spent feeding, which became concentrated into the first trial of the day. Pursuit time did not vary with prey weight, but manipulation time and the weight of prey gained per unit pursuit plus manipulation time increased with prey weight.The growth rate of pike was a positive function of ration size and a negative function of the amount of time spent capturing each gramme of prey (capture cost). Growth rate was also correlated with the mean length and weight of prey eaten.The most profitable prey, as estimated from optimal foraging theory, need only be available once every 84 min for pike to maximize their net energy gain. The data show that feeding behaviour can have a direct influence on the reproductive success of pike through its effect on growth rate.
Cadmium dynamics in fish: pulse studies with 109Cd in female zebrafish, Brachydanio rerio
Authors: Karlsson‐Norrgren L. , Runn P. 
Published: January 2006

The dynamics of a subtoxic pulse of non‐dietary 109Cd was followed for up to 304 days after the exposure period in female zebrafish. The retention of dietary 109Cd was also estimated.The distribution of 109Cd was studied by autoradiography, whole‐body analysis and tissue sampling. After exposure to non‐dietary 109Cd for 10 days there was a rapid loss of 109Cd from the gills. The 109Cd content of the alimentary canal exceeded that which could have been expected from normal drinking. Based on the distribution pattern of non‐dietary 109Cd in tissues, two groups of tissues were distinguished:

the gills, alimentary canal and heart which showed maximum 109Cd values directly after exposure, followed by a pronounced decrease up to day 21;
the liver, kidney, ovary and muscle, in which there was a delay in maximum 109Cd activity to days 21–42, with subsequent loss.

Small amounts of 109Cd were noted in fry and fertilized eggs originating from zebrafish exposed to non‐dietary 109Cd. After exposure to dietary 109Cd, less than 5% was retained in the zebrafish body, mainly in the alimentary canal.
The formation of non‐anadromous populations of Atlantic salmon,Salmon salarL., in Europe
Authors: Berg O. K. 
Published: January 2006

Comparison of the different populations of non‐anadromous Atlantic salmon in Europe has revealed some common traits. The non‐anadromous populations probably became isolated from the anadromous salmon populations during a period of rapid land‐upheaval after the last ice age, about 10 000 years ago. The oceanic temperature in the eastern part of the Atlantic was especially low in this period. This probably diminished the advantage gained from the anadromous habit. During this period the low temperatures in the rivers probably increased the frequency of females which matured without migrating seawards. A large number of individuals in the different populations seems to have been favourable for the formation and survival of such races. The occurrence of a lake in such a river system would probably ease the transition to non‐anadromous behaviour, because the salmon would not then be forced to adjust its entire life‐history when isolated (the salmon could spawn in the river in the usual manner and the smolts then migrate downstream into lakes). Larger lakes would also seem to infer problems for the navigation of the smolts towards the outlet. The only known exception is the river‐living land‐locked salmon population found in the River Namsen, Norway.The factors mentioned above have led to an increase in the probability of occurrence and thriving of mature females without a sea migration or to a decrease in the competitive advantage of anadromous behaviour. The above mentioned similarities can explain the seemingly casual distribution of the non‐anadromous populations of Atlantic salmon in Europe.
Estimation of population parameters and their application to the development of fishery management models in two African rivers
Authors: Payne A. I. , McCarton B. 
Published: January 2006

The dynamics of fish populations in two African rivers are being investigated with a view to developing fishery management models for tropical non‐floodplain rivers. Preliminary work was carried out in the Rufiji River, East Africa, to establish growth and mortality rates along with L∞ and K for six species in a river where fishing mortality is zero. These parameters, derived from scale‐reading and length frequency analysis, also allowed the development of phased management plans for the fishery resulting from impoundment.A subsequent investigation has begun on a West African river, the Taia in Sierra Leone, to pursue observations over four seasons, two of which are now complete. A systematic daily sampling programme is being carried out of the whole community, to accumulate similar but more extensive data to those obtained previously. In the Taia, however, fishing mortality must also be estimated from catch surveys, and analysis is carried out using the recently developed ELEFAN programs which can be compared with results obtained by other methods such as scale‐reading.
The food, feeding habits and feeding structures of the whiting species Sillago sihama (Forsskål) and Sillago analis Whitley from Townsville, North Queensland, Australia
Authors: Gunn J. S. , Milward N. E. 
Published: January 2006

The diet, feeding habits and feeding structures of 519 Sillago sihama and 493 S. analis specimens collected from beaches and estuaries in the Townsville region are described. The species are carnivores on a wide range of benthic, epibenthic and planktonic prey. Both undergo size related dietary shifts; S. sihama from predominantly planktonic crustaceans in fish of less than 80 mm t.l. to polychaetes, penaeid and brachyuran crustaceans and molluscs at larger sizes; S. analis from a mixture of small Mesodesma eltanae and amphipods at sizes of less than 80 mm t.l. to predominantly M. eltanae and small quantities of penaeids and brachyuran crabs in larger fish. The dietary shift was not associated with migration from a nursery area.While the species showed considerable overlap in the types of prey utilized, there were significant differences in the relative importance of shared components in their diets. The major difference was in the relative importance of the bivalve mollusc, M. eltanae. This was the dominant food of S. analis but of secondary importance in S. sihama. Associated with this basic difference in diet was a specialization of the pharyngeal dentition in S. analis to molariform crushing plates and a reduction of the gill rakers to vestigial knobs. In S. sihama, the pharyngeal teeth are sharp and pointed and the gill rakers normal.The feeding activity of S. analis, but not S. sihama, is limited by the tidal cycle, a factor which may be a form of temporal partitioning.
Changes in structure of tissues and in plasma cortisol during the spawning migration of pink salmon, Oncorhynchus gorbucha (Walbaum)
Authors: Mcbride J. R. , Fagerlund U. H. M. , Dye H. M. , Bagshaw J. 
Published: January 2006

Changes in the structure of the gonad, skin, interrenal, liver, kidney, stomach, gill and pituitary gland, as well as blood cortisol and haematocrit values were investigated in adult pink salmon during their migration through the Fraser and Thompson Rivers to the spawning grounds. At the commencement of their freshwater migration the gonads of both males and females were in an advanced state of development, the pituitary contained a large complement of well‐granulated gonadotrops, and hypertrophy was evident in the interrenal tissue and in the epidermis of the skin. At this time, no change from the normal sexually immature salmon was evident in the structure of the gill, liver or stomach. Sclerosis of the glomeruli was noted in the kidney. The plasma cortisol level was consistent with concentrations in unstressed salmon.Migration of the fish through a turbulent section of the Fraser River evoked a marked increase in both blood cortisol concentration and in interrenal nuclear diameters.On arrival at the spawning grounds, 10–15 days after entry into fresh water, a general but not marked deterioration of the tissues was evident. The results are discussed in relation to the spawning migration of other species of Pacific salmon.
Size‐segregative behaviour in minnow shoals
Authors: Pitcher T. J. , Magurran A. E. , Allan J. R. 
Published: January 2006

Shoals composed of equal numbers of two size‐classes of European minnows were observed undisturbed, feeding and after threat from a pike in a large arena tank.The time/frequency budget and analysed sequences of behaviour of the two size‐classes were very similar. Irrespective of size, for standard behaviour measures, fish in the shoal behaved similarly under the same external influences, including predator threat.In contrast, however, the distribution of the two size‐classes provided evidence of size segregation within the shoal. This was brought about by individual minnows making shoaling responses preferentially to their own size‐class. After exposure to the predator, shoaling responses changed and differed between small and large minnows.The outcomes of contests at foraging patches were governed primarily by fish size and information asymmetry rather than by occupation of a feeding site.The experiment shows that asymmetrical pay‐offs in foraging and in response to predator threat are the probable reasons for size‐segregation behaviours. This conclusion supports the views of earlier workers that mechanical sorting by swimming speed is not an important factor in size segregation in shoals.
On causation and function of the pre‐spawning behaviour of cichlid fish
Authors: Baerends G. P. 
Published: January 2006

This paper reviews studies based on the theory that animal behaviour is organized and controlled by a taxon‐specific ‘software’ design, to which the principles valid for the evolution of morphological and physiological mechanisms equally apply, and which therefore is also subject to adaptive radiation.Causal ethological analysis of the pre‐spawning behaviour of some oral‐ and some substrate‐breeding cichlid species has led to the conclusion that the course of this behaviour, as well as the character of its elements, results from the interaction of at least three mutually‐incompatible behavioural control systems serving, respectively, escape from danger, repulsion of conspecifics (‘aggression’), and attraction of a mate (‘sex’). In the course of pre‐spawning behaviour, the third system gradually gains control over the other two, at least with respect to a particular individual (i.e., the potential mate), losing its effectiveness as a releasing stimulus for aggression and/or escape the more an affinitive individual relationship is built up.In all cichlids, specific motor patterns resulting from the interaction of different sytems in the behavioural organization are functional in selection of the sex‐partner and in preparation of the spawning site. In the sexually dimorphic oral incubators, the form of these activities also differs between the sexes. Performed alternately by male and female, they form a stimulus‐response chain. In contrast, in the monomorphic substrate spawners, in which pair bonds last much longer, these activities are the same in both sexes, which usually perform them simultaneously. In addition to the two functions just mentioned, they serve the establishment of the long‐lasting bond between partners, and the necessary synchronization of their endocrine states for spawning.