摘要:

Age, growth and reproduction of theR. lemmingiipopulation of the River Huebra, Duero basin are analysed. Females dominated older age classes and lived up to 6 years (5+) while males only reached 5 years (4+). The growing season extended from April to September; growth rates were similar for both sexes. 0+ fish condition increased during their first summer and spring. In older fish, condition cycle was related to gonad development and showed some differences between sexes. The number of females reaching maturity at age 1 + almost doubled that of males; females also matured at smaller size. Both fecundity and egg size increased with female length: mean egg counts varied between 974 for 1 + individuals and an estimated 10491 for 5+ fish. Eggs were produced as a single batch, but were released fractionally during April and May.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb03549.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The gills ofPeriophthalmus chrysospilosexhibited significantly greater pyruvate kinase and lactate dehydrogenase activities than those ofBoleophthalmus boddaerti(P<0.01). Under the control normoxic condition, the branchial lactate content of the former mudskipper was also significantly greater (P<0.01) than that of the latter. After hypoxic exposure, lactate and alanine accumulated in the gills of P.chrysospilosbut notB. boddaerti. Succinate and propionate were not detected in the gills of these two mudskippers under the control and hypoxic conditions.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb03550.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The ability of the gastrointestinal tract of chinook salmon,Oncorhynchus tshawytscha, to absorb polypeptidesin vivowas investigated by reference to the appearance of orally administered adrenocorticotropic hormone (ACTH) within the blood of fish previously treated with dexamethasone (3μg g−lbody weight) in order to suppress endogenous ACTH secretion. Further, since cortisol presence within plasma is dependent upon the availability of ACTH, dexamethasone blockade of endogenous ACTH secretion, in conjunction with subsequent measurements of plasma cortisol levels, provides a means by which biological patency of absorbed exogenous ACTH may be demonstrated. Levels of ACTH and cortisol in plasma of dexamethasone‐treated salmon were therefore measured for a period of 360 min immediately following oral intubation of ACTH (15μg g−1body weight). Peak plasma presence of ACTH‐like immunoreactivity (676.6 ± 33.6 pg ml−1plasma) and cortisol (227.1 ± 29.0 ng ml−1plasma) were recorded 120 min after ACTH administration. Results from the experimental groups were compared to those of 15 control treatments. Since administration of ACTH to chinook salmon elicited a consistent and significant elevation in not only plasma ACTH but also cortisol presence, it is contended that the salmonid gut expresses an ability to absorb polypeptides of dietary origin. The significance of these findings with respect to the oral administration of biologically active peptides and proteins to fish of importance to aquacultu

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb03551.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

A study was carried out on the serum levels of cholesterol [total (TC) and that associated with high‐density lipoproteins (HDLC)] and triglyceride (TG) in 127 specimens ofScyliorhinus canicula. The values obtained were correlated with sex, size, liver weight and reproductive stage. Results showed that male dogfish have higher levels of TC and HDLC, and lower TG than female. In adult males, TC increased and HDLC decreased with both size and spermatogenesis. Females carrying capsulated eggs showed a noticeable increase in TG together with a decrease of the HDLC levels, which were apparently not related with siz

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb03552.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Migration and spawning behaviour of eight Atlantic salmon adult females were analysed by radio‐tracking in relation to the degree of sexual maturity in a spawning tributary of the R. Sélune. Six of them were grilse and four of them were ripe. All the fish migrated upstream until reaching their spawning site at a distance of 4–12 km from the trap. The daily migration rate up to this site was inversely correlated with the length of the female. Spawning occurred in all fish at the same time when the water temperature increased dramatically. Spawning lasted 1–10 days according to the fish. After spawning, females quickly moved downstream only small distances and then stayed in approximately the same location until death. This study concluded that ripeness did not influence behaviour on the spawning migration and describes certain characteristics of the reproductive phase in a spawning tri

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb03553.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The problem of determining and verifying ages of fish, from populations having a considerable variation in size at age, has been investigated using the relationship between otolith size and fish size, which has been shown by several authors to be influenced by growth rate. In such a populationof Sardinella auritaVal. an index of age can be obtained for individual fish by calculating the equivalent otolith weight at a particular fish length, using the otolith weight–fish length relationship determined for each age group. This statistic not only permits a much greater proportion of fish to be assigned ages than is possible with otolith reading alone, but also enables the age groups to be verified as year classes. However, it is concluded that, although appropriate models based on otolith‐fish size relationships can predict age for groups of fish in which growth rates are known or can be assumed to be consistent, such techniques have a limited application in ageing fish from wild populations with highly variable growth ra

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb03554.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Ecological studies were carried out in shallow experimental sites in the Lancaster Canal to evaluate potential interactions between grass carp and feeding habits of tench.Grass carp, through moderate weed consumption, produced better conditions for the exploitation of benthic organisms by the benthophagous tench, because tench (>35 cm fork length) were able to search for food in the open areas created. This also enabled the fish to make use of zooplankton, mainly the large speciesEurycercus lamellatuswhose restricted phytophilic habitat made it vulnerable to predation. Epibenthic animals, in particular gastropods andAsellus aquaticus, suffered principally from the predation, which caused severe reduction of them in the site totally depleted of vegetation. In this site, tench utilized a diet in which red chironomids were the dominant prey group together with a large amount of fine detritus.It is suggested that a moderate control of vegetation in temperate climates, using the grass carp as the biological agent, could be a satisfactory management technique for the improvement of aquatic habitats.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb03555.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Growth, density and production of juvenile Atlantic salmon and brown trout were studied in three different sections of the Kvassheimsåna River in south‐western Norway from 1979 to 1983. Section 1. in the upper part of the river, is located above a waterfall impassable for migratory salmonids and is surrounded by grazing land. Sections 2 and 3, in the middle and lower parts of the river, are influenced by agricultural activity. Total nitrogen concentration varied between 250 and 1000 μg l−1in section 1 and 1500 and 2500 μg l−1in sections 2 and 3. Total phosphorus (Tot‐P) concentrations also increased with decreasing altitude: 19–46 μg l−1in section I and 31–101 μg l−1in sections 2 and 3.The number of 0 + salmon in sections 2 and 3 varied between 30.1 and 167.8 specimens 100 m−2, with means 90.2 and 95.2 specimens 100 m−2:, respectively; the density of 1 + salmon, with mean values of 16.3 and 51.0 specimens 100m−2was significantly correlated with the original fry density. The growth rate of 0+ salmon was not inversely related to cohort density, but was significantly so for 1 + salmon. Mean annual salmon production in section 2 was 1595 g 100 m−2year1, and in section 3 was 841 g 100m−2year1. A logarithmic function gave the best curve fit between salmon production and mean annual biomass. Thus, production levelled off for the highest values recorded in section 2, and perhaps approached the carrying capacity of the stream. A multiple regression analysis showed that yearly variation in 1 + salmon density was the single factor accounting for most of the total variability in production (60%). Variation in water temperature and nutrient content were not significantly related to variation in fish production.Densities of brown trout were low in all sections (<20 specimens 100m−2). Fry density was highest in section 3 and parr density in section 1. All age groups of sympatric brown trout grew significantly faster in sections 2 and 3 compared with all

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb03556.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Macrophage activating factor (MAF)‐containing supernatants, generated by mitogen (Con A/PMA) stimulation of rainbow trout leucocytes, were found to confer viral resistance (interferon, IFN, activity) on a rainbow trout epithelial cell line challenged with infectious pancreatic necrosis virus. Both the MAF and IFN activities co‐eluted by HPLC size exclusion chromatography and showed similar sensitivities to acid (pH 2), temperature (60° C) and trypsin. The mode of induction of this IFN, its acid and temperature sensitivity and its possible MAF activity suggest that fish leucocytes can secrete an IFN‐γ like m

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb03557.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Separation of leucocytes from tissues and enrichment of specific types of leucocytes are essential first steps in studies of leucocyte function. We describe a simple and rapid method for separating and enriching leucocytes from the anterior kidney and spleen of rainbow trout. Leucocytes were separated on self‐generating density gradients of Sepracell‐MN, a colloidal silica‐based medium. Recovery of leucocytes from the gradients was near 100% and was not affected by procedural variables such as cell suspension: Sepracell‐MN ratio (separation ratio), initial temperature, centrifugation time, or number of cells per gradient. Two bands of leucocytes formed at separation ratios of 1 : 1, 1:1.5, 1:2 and 1 : 3. Recovery of selected leucocyte types could be maximized, and contamination by other cell types reduced, by selection of the appropriate separation ratio and cell band. Recovered leucocytes were responsive in assays of functional capability (adherence, phagocytosis, superoxide anion production). Leucocyte populations that adhered to glass were enriched for macrophages, but some neutrophils and lymphocytes (paricularly spleen lymphocytes) were also adherent. The most abundant leucocytes in the anterior kidney and spleen of the experimental fish were lymphocytes (respectively, 47 and 88%, including thrombocytes), neutrophils (35 and 7%), and macrophages (11

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb03558.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY