摘要:

The formation of daily growth increments of otoliths was studied in the reared larvae of milkfish. The first growth increment was formed during the yolk–sac reabsorption periodc.2 days after hatching, and increment formation continued on a daily schedule regardless of growth rate. The initial incremental zone was of amorphous structure, and the subsequent incremental zone was of needle–shaped crystalline structure; the former structure was formed in the yolk–sac reabsorption period of the larva and the latter in the exogenous feeding period. Accordingly, ageing of milkfish larvae is possible by counting growth increments, and timings within the developmental stage of the larvae can be understood by examining the otolith microstru

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1988.tb05389.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Histological observations were made on the distribution and concentration of the superficial mucous cells and on the thickness of the epidermis in immature yellow and in male and female silver eels. In all groups there was a decrease in the concentration of mucous cells from the anterior regions to the posterior regions, while the epidermis was thickest in the median parts of the body. Besides these common characteristics, a sexual dimorphism was shown: in silver eels the epidermis is thicker than in immature yellow eels; female silver eels have both the thickest epidermis and the greatest concentration of superficial mucous cells.Results are discussed in the light of knowledge on the influence of environmental and endocrine factors on the structure and function of epidermal mucosa in teleosts.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1988.tb05390.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The sardineLimnothrissa miodonwas very patchily distributed in Lake Kariba in 1981–1983 and its mean biomass was 59 23 kg ha−1, declining from 90–91 kg ha−1in 1981 to 38–66 kg ha−1in 1983. In addition, the mean size of the fish fell from 55–2 mm in 1981 to 49–9 mm in 1983. These changes are attributed to the effects of drought and reduced river flows as well as to the high level of commercial fishing for this species. There was a correlation between commercial catches and biomass estimates which allowed estimation of biomass in previous years from fishing statistics. Fishing effort appeared to be a major influence on sardine abundance: total biomass in 1985 was about 10% of what it was in 1974 when the fishery began. When expressed in terms of unit area, as is usual for African lakes, the pelagic biomass appeared to be greater in Lake Tanganyika, whereLimnothrissais endemic, than in Lake Kariba, although there is little difference in their primary productivity, but consideration in terms of volume rather than area shows that

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1988.tb05391.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

In monthly samplesof Liza abucollected November 1981–October 1982 from Mehaijeran Creek, a western branch of Shatt–Al–Arab river south of Basrah, fishes were infected with the third larval stage of the nematodeContracaecumsp., the acanthocephalanNeoechinorhynchus agilisand the gill crustaceanErgasilus mosulensis.Generally, the changes in the percentage prevalence coincided with the changes in the mean intensity of infection. There were no significant differences between the infection of male and female fishes in the cases of the monthly variations of infection withContracaecumsp. and of infection with bothContracaecumsp. andE. mosulensis, according to fish length, but in other cases more female fishes were infected than males.Infection withContracaecumsp. decreased gradually in the larger fishes. In the case of bothN. agilisandE. mosulensis, the infection at first increased with increase in fish length but decreased in larger fishes.Infection withContracaecumsp. occurred only during May–August and disappeared during September. The peak forN. agiliswas in April, and it disappeared during summer. Infection withE. mosulensisdisappeared during winter

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1988.tb05392.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Analysis of largemouth bass scales, including those from 48 tagged and recaptured fish, revealed that many scales had more ‘annuli’ than possible for the age of Flint Creek Cooling Reservoir. The mark‐recapture data indicated the formation of one supernumerary annulus per year for most bass. Time of formation of true and supernumerary annuli and the causative factors are discussed.Growth of bass from this reservoir greatly exceeded that reported for thermally unaltered reservoirs of Northwest Arkansas, due to the existence of a nearly year‐round growing season, a result of thermal enrichment. The relationship between the ratio of electric power output to reservoir surface area and growth offish was evaluated with reference to published data on cooling res

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1988.tb05393.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Juvenile Atlantic salmon,Salmo salarL., were implanted with different amounts of the stress hormone hydrocortisone in cocoa butter and wounded with small surgical incisions on the ventral and dorsal surfaces. Hydrocortisone had no effect on epidermal migration which closed the wound by 8 h. Although low levels of hydrocortisone had little effect on wound healing after 3 months, high levels retarded dermal repair, particularly fibrosis and closure of the stratum compactum. Ultrastructural findings indicated that fibroblast activity was impaired. The implications for aquaculture are discussed.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1988.tb05394.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Trout fitted with arterial catheters were subjected to 6 min of strenuous exercise, injected with either saline (controls) or the β‐adrenergic antagonist propranolol, and monitored over the following 8‐h recovery period. Control responses were very similar to those previously reported, except for much higher resting and post‐exercise plasma catecholamine levels, and less marked RBC pHi regulation, perhaps due to season (February–May). Trout subjected to prior β‐blockade would not exercise. Trout β‐blocked immediately after exercise showed a much higher incidence of mortality during the recovery period, but accompanying symptoms were similar to those previously documented in control trout dying after exercise. Specific effects of post‐exercise β‐blockade seen in both survivors and mortalities were a sustained elevation of arterialPco2and an inhibition of blood glucose elevation. There were negligible effects on RBC pHi and volume regulation, blood metabolic acid and lactate dynamics, or plasma ion changes. The results provide little support for the hypothesis that β‐adrenergic actions of plasma catecholamines are intimately involved in post‐exercise recovery, but must be considered in the context of the ‘winter’ trout, where

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1988.tb05395.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

After the disappearance of the haplochromine species in the Nyanza Gulf of Lake Victoria as a result of predation byLates niloticus, the latter has turned its attention to aquatic invertebrates and other fish. Changes in the diet of the Nile perch with increase in its size have been observed: youngL. niloticuspreyed mostly on invertebrates, including crustaceans and various small aquatic insects; large, immatureL. niloticussupplemented the invertebrate diet with both young and small fish; adults above 80 cm total length were mainly piscivorous.L. niloticusfeeds on fish prey of about one third its own length.The tendency ofL. niloticusto switch from one prey item to another, depending on availability, is reported; e.g., in the Nyanza Gulf, the prey diet has shifted from the haplochromine toCaridina niloticaandL. niloticusjuveniles.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1988.tb05396.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Peripheral blood neutrophils were studied in eels injected with phosphate buffered saline, bacterial lipopolysaccharide (LPS), carrageenan (CAR), LPS and CAR together (CAR/LPS(T)), CAR and LPS 4 days later (CAR/LPS(S)), zymosan and latex beads. All stimuli caused a left shift toward neutrophil immaturity but LPS‐elicited neutrophils, particularly in CAR/LPS stimulated eels, were often extremely basophilic, enlarged, vacuolated and had a large nucleus with poorly differentiated nuclear chromatin. These intensely basophilic neutrophils (IBN) had few granules and lower acid phosphatase and non‐specific esterase, but higher PAS levels, compared to normal neutrophils. Ultrastructurally, IBN showed loss of cytoplasmic content that gave a ragged appearance, the nucleus was often immature and many rough endoplasmic reticulum profiles restricted the distribution of reduced numbers of cytoplasmic granules. These features are attributed to asynchronous development, and IBN are compared with mammalian toxic neutroph

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1988.tb05397.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

A massive hybridization betweenLeuciscus cephalus macedonicusandChalcalburnus chalcoides macedonicushas been recognized and studied by examining 67 specimens from Lake Volvi (Macedonia, Greece). The majority of meristic and other characters present an intermediate position in the hybrid (total hybrid indexVh= 38.37). Nevertheless, the best expression of intermediacy is shown most clearly by the numbers of anal fin soft rays, lateral line scales and gill rakers, and also by the height of the dorsal fin and the length of the base of anal fin. Of the examined hybrid specimens. 92.5% were females. It seems that hybridization takes place during the reproduction period in the main streams flowing into the lake under special conditions which hinder the migration of the majority of the population ofC. chalcoidesfrom the lake to the breeding sites. It is suggested that individuals ofC. chalcoides, which manage to arrive in these sites, mate withL. cephalus, the normal inhabitant of the streams, thus producing the hybrid.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1988.tb05398.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY