摘要:

Yearling brown trout,Salmo truttaL., were maintained in a synthetic medium at pH 5.2 with various concentrations of calcium (4–400 μumol l−1) and aluminium (0–3 μumol l−1). In general, higher mortality and lower growth rates were found at higher aluminium concentrations, with these effects being reduced at high ambient calcium. Aluminium toxicity was greater in an experiment conducted in February–March than in an experiment conducted in October–December; this could be due to a seasonal variation in tolerance of the fish. Aluminium exposure resulted in an initial period of weight loss and high mortality followed by some recovery over the 6‐week period of the experiments. In the first experiment, as in previously reported work, adaptation was incomplete in that aluminium‐induced growth rate reduction was still evident to the end of the test. In the second experiment, however, no significant effect of aluminium treatment on growth was found during weeks 4 to 6 of th

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1988.tb05460.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The condition and maturation of theOreochromis niloticuspopulation of Ferguson's Gulf, Lake Turkana was assessed in light of the declining lake level and compared with similar data taken at the high lake level period 10 years ago. Results show a dramatically lower length/weight relationship and an earlier length at maturity for the 1980s population. A defined breeding period was seen for the 1980s population, unlike in the 1970s, perhaps in response to stressful conditions. The reduction in area of the Ferguson's Gulf breeding/nursery grounds is suggested as the major factor contributing to stress in theO. niloticuspopulation, and it is suggested that measures be taken to protect what is left of these breeding/nursery areas.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1988.tb05461.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The morphology of the alimentary canal, feeding technique and responses to sensory cues were investigated inLeiopotherapon unicolor. The small conical teeth on the jaws and pharynx, simple Y‐shaped stomach and short gut ofL. unicolorare characteristic of opportunistic carnivorous fish. Five types of behaviour, ‘basal’, ‘orientation’, ‘positioning’, ‘attack’, and ‘ingestion’, were recognised and are described. Capture of prey small enough to swallow whole was assisted by suction created as the mouth opened to engulf prey. Crustaceans too large to ingest whole were broken into smaller pieces against the substrate. Directional and oscillatory movement were the most effective sensory cues in eliciting feeding behaviour, implicating vision as an important sense forL. unicolorfeeding in confined aquaria. Acoustic and olfactory senses are less important in prey capture. The frequency with which spangled perch responded to different sensory cues increased w

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1988.tb05462.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Age and size at sexual maturity were significantly greater for male mosquitofish,Gambusia affinisBaird and Girard, reared in sib‐groups than for their sibs reared individually. Age at sexual maturity averaged 43.3 and 62.1 days for individually‐ and group‐reared males, respectively, a 43% difference; final length and weight at maturity were 7.7 and 34.2% greater, respectively, for group‐reared males than for their individually‐reared sibs. The results were consistent among 30 families that represented the progeny of 30 wild‐caught females. The observed differences may be attributable to behavioural interactions affecting the neuroendocrine control of the maturation process, as suggested by previous studies of

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1988.tb05463.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Ontogenetic changes in the diet of early post‐settlementScarusspecies are described, based on analyses of intestinal contents. There is a marked change‐over from carnivory to herbivory. Newly settled individuals feed on Crustacea, primarily harpacticoid nauplii and adults, whilst larger juveniles almost exclusively ingest algae and sand. In comparison, the diets of recentlysettled Acanthuridae, Siganidae and Pomacanthidae were found to be almost exclusively herbivor

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1988.tb05464.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The fat laid down as a winter reserve by O‐group sand smelt,Atherina boyeri, was found to be size‐dependent. The larger, earlier‐spawned fish lay down more fat prior to the onset of winter. During the winter the fish do not feed for some 100 days and rely on this fat for energy; laterspawned O‐group fish (<59 mms.l.in November) have insufficient fat reserves and starve to death in a normal winter. This loss of the smallest 46% of the O‐group is shown as an increase in the mean size of the O‐group over the winter period. Older sand smelt age classes have more than sufficient fat reserves for overwintering. There is thus a clear advantage in spawning early in the season, and any restriction on spawning ground availability at that time will result in overall population regulation. This conclusion supports the hypothesis that the density‐dependent control on population size in the sand smelt is a limitation on the number of fish which can spawn at the

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1988.tb05465.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Granulocytes from cranial granulopoietic tissue were studied under the electron microscope, and cytochemistry carried out oncranial and peripheral blood granulocytes of two sturgeons,Acipenser brevirostrum. Ultrastructurally, eosinophils and basophils had homogeneous electron‐dense granules similar to those of teleosts and some higher vertebrates. Neutrophils contained two granule types: small elongated fibrillar granules and large (<3.8μm long) usually homogeneous granules.Neutrophil fibrillar granules were positive for alkaline phosphatase (ALP), acid phosphatase (ACP), α‐naphthyl acetate esterase (ANAE), acetyl‐l‐tyrosine‐α‐naphthyl esterase (ATNE) and periodic acid Schiff (PAS) reaction. The large homogeneous granules were negative for all enzymes, and were only PAS positive. Eosinophils had granular, cyanide‐, azide‐ and aminotriazole‐resistant peroxidase (PO) and were ACP, ATNE, tosyl‐l‐lysine‐α‐naphthyl esterase (TLNE) and Luxol fast blue positive.Ultrastructure and cytochemistry are discussed in relation to other vertebrates, and eosinophils identified as

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1988.tb05466.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Observations on granulocyte peroxidase of 123 teleosts are reported and correlated with previous studies to put occurrence of fish granulocyte peroxidase in a phylogenetic perspective. Eosinophil peroxidase occurs in archaic groups such as lungfish and sturgeons, but is usually weak and infrequently observed in chondrichthyans, and in teleosts occurs in some elopomorphs, is consistently observed in stomiiforms, is rarely observed and usually weak in acanthopterygians and absent from salmoniforms, scopelomorphs and paracanthopterygians. Peroxidase is absent from lungfish and sturgeon neutrophils, is present in neutrophils of some elopomorphs and clupeimorphs. both of which are basal teleost groups, but in salmoniforms and higher teleosts is consistently observed in neutrophils. although often weak in pleuronectiforms.Loss of eosinophil peroxidase and development of neutrophil peroxidase in teleosts may be due to inefficient phagocytosis and loss of peroxidase with degranulation in eosinophils, being superseded by concentration of peroxidase in phagosomes in neutrophils.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1988.tb05467.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Endurance and swimming speed were measured in mackerel, herring and saithe when they were induced by the optomotor response to swim at prolonged speeds along a 28‐m circular track through still water in a 10‐m diameter gantry tank. The maximum sustained swimming speed (Umswas measured as body lengths per second (b.l.s−1) for each species and for saithe of different size groups. Herring withUmsof 4.06b.l.s−1(25.3 cm, 13.5°C) were the fastest, mackerelUmswas 3.5b.l.s1(33 cm, 11.7°C) and saithe (14.4°C) showed a size effect whereUmsat 25 cm was 3.5b.l.s1and at 50 cm 2.2b.l.s1. When swimming at speeds higher thatUms, all three species showed reduced endurance as speed increased. How the curved track reduces the swimming speed is

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1988.tb05468.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Regurgitation of stomach contents in the predatory perch and pike captured in gill nets could be readily identified and occurrence measured. Stomachs following regurgitation, as opposed to true ‘empty’ stomachs, were large, distended, with a thin wall and little internal ridging. The mean percentage of genuinely empty stomachs over a 22‐month period in perch was 20–21 % and in pike 7–10%. Regurgitation in perch was rare (21°C: gill netting is therefore a legitimate means of sampling perch in food studies. In pike the sum of partial and complete regurgitation was important, with mean annual values in two lakes of 48 and 50%, and up to 84% in summer samples; it was related to water temperature (x) and described by the significant relationshipy= 20.63+x2.84, but was unrelated to fish length and gill net mesh size. Food studies of predatory fishes using gill nets as a capture method should take account of regurgitation. Further information is required on the extent of regurgitation when other sampling method

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1988.tb05469.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY