摘要:

Juveniles of five species of cyprinids of body length 15–90 mm as well as juvenile perch,Perca fluviatilisL., were fed on living natural zooplankton over periods of 2 or 3 days. For all species the correlation of the daily ration (% body weight) with body weight showed a maximum curve. The maximum was reached at a body weight (wet weight) of 0.6 g forLeuciscus leuciscus(L.) and 0.1 g for a group consisting of varying numbers ofRutilus rutilus(L.),Abramis brama(L.) andAlburnus alburnus(L.). ForL. leuciscus, the maximum was 220% body weight (wet weight), corresponding to 40% on a dry weight basis. For the mixed species group the maximum was about 500% (wet weight) and about 140% on a dry weight basis. The highest daily ration coincided with the occurrence of the spring bloom of zooplankto

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb05628.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Roach larvae and 0+ juveniles were sampled weekly in three different floodplain channels (stagnant, semi‐lotic, lotic) of the Upper Rhône River, France, from spring to autumn 1985 using Point Abundance Sampling by electrofishing. Length‐frequency analysis by size‐class ordination of developmental steps successfully distinguished both overlapping and non‐overlapping histograms within the data matrix and revealed the temporal and spatial segregation of a number of cohorts, individuals born at a common site on the same day, which in some cases presented significant differences in standard length within a given developmental step. Despite these initial differences, the various cohorts converged to form one relatively homogeneous cohort around the moment of transition to the juvenile period. Significant differences in standard length were found between populations in the open lotic channel (relatively cooler) and those in the closed, stagnant (relatively warmer) former channel, suggesting that fish growth in isolated ecosystems is influenced by higher or periodically elevated temperatures and by greater levels of resource competition and predation. A similar pattern of differences in length was also observed in 0+ juvenile roach collected from 18 other floodplain channels of the Upp

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb05629.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

An electron microscopic study was performed on leucocytes from circulating blood of the goldfish. The leucocytes were divided into eight types: neutrophil, eosinophil, large granular leucocyte (LGL), medium‐sized granular leucocyte (MGL), small granular leucocyte (SGL), fine granular leucocyte (FGL), lymphocyte, and monocyte. In this report the thrombocyte was excluded from leucocytes, and LGL, MGL, SGL and FGL were tentatively classified based on the size of intracytoplasmic granules possessed by each cell. The existence of goldfish monocytes was electron microscopically demonstrated for the first time in the present repor

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb05630.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Four types of bacteria, two fluorescent pseudomonads, one aeromonad (Aeromonas hydrophila anaerogens) and one coccus (Micrococcus variant) were isolated from skin lesions of airbreathing fishes. The bacterial culture in mixed condition induced severe ulcers in healthyAnabas testudineus. Pure cultures of each of two pseudomonads and an aeromonad separated from the mixture induced superficial ulcer formation.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb05631.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Three components of the energy budget, consumption (C), production (P) and respiration (R) in juvenile roach and bleak kept under controlled food (Anemia salina, 2400 ind. l−1) and temperature (20° C) conditions were measured in a study aimed at defining differences between the two species and elucidating the patterns of energy partitioning during ontogeny.Daily food consumption rates (J day−1fish−1) increased allometrically (C=aWb) with body size (W, mg dry weight) in both species. Covariance analysis indicated no differences in slope or intercept for the two regression lines (P≤ 0.05,n= 82). However, the two species grew at significantly different rates, roach faster than bleak.The dependence of the respiration rate (μmol h−1fish−1) on body weight (W) can be described by an allometric function:R= aWb, where a ± 95% C.L. = 0.17 ± 0.15 for roach and 0.18 ± 0.20 for bleak. The slope for roach (b ± 95% C.L. = 0.78 ± 0.01) is slightly higher than that for bleak (0.69 ± 0.03).Assimilation efficiency [AE = (P+R)C−1] was significantly higher in roach than in bleak. Different levels of AE correlated with differences in relative gut length (gut length as percentage of body length). Due to the shorter relative gut length above a weight of 5 mg, bleak has lower powers of digestion, which may explain lower production rates. These differences in energetic performance between the two species indicate mechanisms leading to niche differentiation in the early life

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb05632.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The territorial behaviour of a small rock‐dwelling cichlid,Pseudotropheus aurora, was studied at Thumbi Island West at the southern end of Lake Malawi.P. aurorais one of several species that have been introduced to an already diverse fish community. Many of the endemic and introduced species are highly territorial. The coexistence of an introduced territorial species within a speciesrich community of other territorial species is examined. Territories from whichP. auroraindividuals were removed were invariably re‐occupied by conspecifics. Similarly, when all territories of a certain area were emptied of all territory owners of any existing species, the formerP. auroraterritories were re‐occupied by conspecifics.The possible roles of site specificity, competitive exclusion and behaviourally transmitted traditions regarding territories are disc

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb05633.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Drinking was measured by the rate of uptake of tritiated dextran in fresh water by the alevins and fry of rainbow trout at various stages of development during a 40‐day post‐hatch period. Drinking increased almost S‐fold during the initial 16 day yolk‐sac stage. Drinking rate increased most between 16 and 23 days, the transitional period between yolk‐sac absorption and first feeding. The maximum weight‐specific drinkingrateof 3.24μlg−1h−1recorded for 40‐day‐old fry was higher than previously recorded for adults. Abrupt transfer from an adaptation temperature of 10 to 19° C increased drinking significantly (Q10= 1.2), but sudden transfer to 1 1‰ salinity sea water caused a substantial fall in drinking rate in 23‐day fry. A 24‐h period of adaptation to 1 1‰ and 15‰ salinity restored drinking to a rate similar to that in fresh water. The water drunk by 31‐day fry fed to satiation was initially higher than by unfed fry, but drinking rates subsequently fell below the control level. The results are discussed in terms of osmoregulation and the uptake of dissolved or suspended substances by the intestinal trac

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb05634.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Dominance relationships between pairs of Atlantic salmon parr of known size were assessed at various times during their first year of life. In tests conducted between first feeding and early July, the larger of two fish was dominant in only 54% of pairs, regardless of the magnitude of the size difference between the fish. In September, there was a stronger association between size and status, especially in pairs with a large size differential, where the dominant was larger in 72% of cases. In groups of parr tested in April of the following year, there was no relationship between size and status, the larger of two fish being dominant in 48% of cases, regardless of the magnitude of the size differential. This result suggests that status in early social interactions may depend on behavioural properties rather than size and that the larger size of dominant fish reported in a number of salmonids might be a consequence and not a cause of high status.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb05635.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

A review is made of the literature on the back‐calculation of fish body length from marks on scales or other hard parts (otoliths, vertebrae, fin rays, etc.). Though the technique is widely used it does not appear to be well understood. Regression methods are commonly used, apparently in ignorance of the more realistic proportional methods. It is not generally recognized that there are two equally plausible back‐calculation hypotheses which can lead to significantly different back‐calculated lengths. The Fraser‐Lee equation, the most commonly used back‐calculated formula, follows neither of these hypotheses but is based on a misuse of linear regression. It is recommended that back‐calculation be restricted to procedures following one of the proportional hypotheses; that the difference between lengths calculated using the two hypotheses is a useful measure of the minimum uncertainty in back‐calculation lengths; and that more attention be paid to validating back‐calculation hypotheses by comparing observed and back‐calculated lengths for individual fish. The pattern of heteroscedasticity in body length–scale radius plots is noted as a useful diagnostic in evaluating back‐c

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb05636.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The South American livebearing toothcarp tribe Cnesterodontini is discussed, and a description of the gonopodium of each of the species of the four genera is given, together with a figure and a synonymy.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb05637.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY