摘要:

The life history, food habits, feeding and locomotory activity rhythms of the upland bully,PhilypnodonbrevicepsStokell were investigated (February 1969‐March 1970) as a basis for studying the relationships between food consumption, biomass and production of the species in a small, moderately eutrophic lake (one of a pair of adjacent lakes at an altitude of 610m in the South Island, New Zealand, known collectively as Spectacles Lakes). Annuli formed on the scales during August and September and could be used as valid indicators of age, although small fish could be aged simply by length frequency analysis. The maximum life‐span for both sexes was observed to be 4.5 years but growth of males considerably exceeded that of females. Because females matured at a smaller size than males, mature females were in excess of mature males (3.7: 1). Each female laid only one batch of eggs during a short breeding season in spring (October‐December) but several females contributed eggs to each nest. Fecundity ranged from 60–440 eggs per female; the relationship between egg number (F) and length (l) was logF=–1.609+2.314 logland between egg number and age (A)wasF=–93.51+109.93A.Larvae hatched in approximately one month (water temperature 14.4‐17.5°C) and the yolk sac became absorbed after a further eight days. Some fry remained pelagic for up to six months. Fry fed predominantly on Crustacea, but the diet changed to larger insect larvae and young of its own species with increasing age and size of the fish. The diet also varied, but to a lesser extent, with season and the time of day. All age groups showed diel rhythms of feeding and locomotory activity which, however, exhibited complex seasonal phase shifts throughout the year. In general, periods of higher feeding intensity appeared to follow closely the periods of increased locomotory activity. The activity level of larger fish was higher than that o

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1975.tb04573.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Estimates of the basic population parameters for the upland bully,Philypnodon brevicepsStokell, in Spectacles Lakes from February 1969 to March 1970 are presented. The study population in Small Spectacles could be defined as a discrete, freely‐mixed unit bounded by the edge of the lake, within which individual fish moved extensively in all seasons. Individual fish were regularly spaced with respect to their nearest neighbours but samples taken with both push and trap nets exhibited clumped dispersion. In summer older fish were in deeper water by day but moved to the edge of the lake at night, whereas in winter older fish inhabited deeper water by night. Population numbers and densities were high, ranging from 1.95 million fish (208/m2) in February 1969 to 124 thousand (21/m2) in March 1970. Annual mortality averaged 93 % for all age groups combined but was higher during the early stages of life. Mortality also increased during summer. Recruitment in Small Spectacles was low due to egg resorption by maturing females prior to the 1969 breeding season. Spawning, however, occurred normally in the adjacent lake, Large Spectacles, and egg survival was estimated to be 43.5 %, The growing season, as measured by the monthly change in mean length, extended for seven months of the year (October‐April). No growth occurred in winter. Growth of males exceeded that of females and growth within a year‐class was negatively correlated with the numerical strength of the

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1975.tb04574.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Estimates of production, food consumption and efficiency of food utilization for a population of the upland bully,Philypnodon brevicepsStokell, in Small Spectacles (the smaller of two lakes known as Spectacles Lakes) are given for the period February 1969 to March 1970. Length: weight relations were similar among age groups within any one month but a seasonal variation in the ‘condition’ offish, as well as in calorific content of body tissue, was recorded. The mean population biomass was estimated as 21.98 g/m2(21.85 kcal/m2) over the study period; maximum biomass of younger age groups occurred during the late summer but little seasonal change occurred in older groups. Total annual production was 39.78 ±8.25 g/m2(39.55 kcal/m2), but this estimate did not include any fish in their first 1.5 months of life because of the lack of recruitment during the 1969 breeding season. Approximately 70% of production occurred during three months in late spring and summer, and 97% resulted from the two youngest age groups. In fish over one year old, male production doubled that of females, a difference which could be attributed to the greater number and faster growth of male fish. Production due to sexual products amounted to less than 1% of the total production. Annual food consumption was approximately 302.8 g/m2(249.7 kcal/m2) and the gross efficiency of food utilization was in the order of 16%. Efficiency was similar between sexes of the same age group; faster growth and production of males, therefore, resulted from a greater food consumption rather than a difference in utilization of food. Efficiency was highest during spring and summer and, for most of the year, decreased with age. Efficiency was low in autumn when, although food consumption was relatively high, little production resulted. These seasonal and age differences are discussed with respect to Paloheimo&Dickie'sK‐line

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1975.tb04575.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Some observations on the biology ofCirrhinus reba(Cuvier) from Muzaffarnagar (U.P., India) have been made during the period July 1966 to June 1969. InC. rebaboth males and females mature simultaneously. The gonads attain the maximum weight in June and minimum in November. There is a definite seasonal cycle in relative condition. The relative condition in both male and female is highest in June preceeding the period of breeding. It is the gonad weight which influences the fluctuations of the relative condition. The visceral weight does not exert any significant effect on it. It is found possible to determine the spawning season and its extent, from the seasonal fluctuations of the relative condition. The present studies have also thrown light on the maturation and spawning habits ofC. reba. The fish has only one spawning season of short duration, running from July to early September. In a mature ovary, the mature ova form only one mode which is sharply distinguished from the immature stock.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1975.tb04576.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Galeus piperatusSpringer&Wagner, the peppered shark, is a dwarf shark found in the Gulf of California north of the City of Guaymas, Sonora. It has been taken in June and August 1971 and in February and March 1972, and is found from 130–550 m with maximum abundances from 170–420 m deep. Numbers are higher in June and August (up to 110 individuals/ha) than in February and March. In June and August 1971 the area of distribution included all the waters north of Isla Tiburón and Isla Angel de la Guarda, and below the 130 m isobath. During these monthsGaleus piperatuswas found at 12 and 33 stations respectively, but was taken at only one station in the same area during February and March 1972. The fishing effort expended during these periods was 16, 42 and 60 units respectively. It seems likely that a strong migratory movement causes these differences in abundance and distribution.Galeus piperatushas been taken from 50–100 m off the bottom in mid‐water trawls at night and is clearly a mid‐water and demersal form. Sexually mature females carrying olive green egg cases were taken in large numbers in June 1971 and were also present in reduced numbers in August 1971. Only females 18 cm or more in total length carried egg cases. The migration ofGaleus piperatusinto the North Gulf of California appears to coincide with sexua

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1975.tb04577.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

A population ofMerluccius angustimanusGarman has been discovered in the south‐east Gulf of California, where it is found at 80–120 m in the south of its range (Mazatlan to Altata) and down to 500 m at the northern end of its range (Isla San Pedro Nolasco, north of Guaymas). Studies of the otoliths and catch curves ofM. angustimanusshow that it lives up to seven years, and may reach 39 cm long (one fish) although it does not usually exceed 32 cm. Using the notation of Beverton&Holt (1959) the following parameters were estimated:L∞= 32.7 cm,K= 0.35,t∞= 0.016,t∞= 7years,Lm= 22.0 cm,Mfor 3–7 years of age = 0.79,Mfor 2–3 years of age = 0.79‐0.89. The von Bertalanffy equation forM. angustimanuswas:and was shown to give a reasonably close fit to the re

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1975.tb04578.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1975.tb04579.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

GuppiesPoecilia reticulata(Peters) were subjected to repeated measures of 5 min duration, on an open field test. The major measures were the number of times a fish changed sections, the number of different sections entered regardless of how many times they entered a section and the ratio of inner to outer sections entered. The activity scores were on a continuous distribution from fish to fish and for the males correlated highly with the ratio of inner to outer movements, but not so for the females. All fish showed a preference for the outer rings compared to the inner rings. There was a non–significant tendency for the male activity to increase during each test, but to wane as the number of tests increased. The females showed a variation of activity which may be associated with their ovarian cycle, but the various activity measures tended not to correlate with each other during the cycle and also failed to correlate with various published cycles of physiological ovarian activit

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1975.tb04580.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Growth and survival of sea bream,Archosargus rhomboidalis(L.) larvae were affected by both abundance of eggs that were initially stocked in 75 1 rearing systems and by the concentration of copepod nauplii and copepodites that were fed to larvae. Stocking levels were 2, 4, 8,16 or 32 per litre while food abundance was maintained at approximately 100, 500, 1500 or 3000 per litre. Experiments were of 16 days duration at 26° C. Survival was best, often exceeding 60%, when food levels were 1500 or 3000 per litre and when stocking density did not exceed 8 eggs per litre. Growth was best at the lowest stocking densities and highest food levels. The highest total yields in wet weight occurred at 8 per litre stock density and 3000 per litre food level. Mean wet weight per survivor and yield per stocked egg were greatest at the lowest stocking densities and highest food levels. A 500 per litre food level was marginal for growth and survival, and 100 per litre produced significant survival only at the 2 per litre stocking density. Two experiments at 6000 and 10 000 per litre food levels at 4 per litre stock density gave the best observed growth, and survival as good as in any other experiments. Possible relations between sea bream larvae and their food supply in the natural environment are discussed. Results also are discussed in terms of their possible contribution to aquaculture efforts

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1975.tb04581.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

The fine structure of an unusual cell, the ‘Stäbchendriisenzellen’ (the so‐called foliaceous or rodlet cells of several authors), associated with the endothelium of the vascular system of marine and freshwater fishes was studied in the goldfishCarassius auratus(L.). The bulbus arteriosus was fixed with either a 6 % solution of buffered glutaraldehyde or with one part of a 3 % solution of lanthanum nitrate plus two parts of a 3 % solution of buffered glutaraldehyde and then post‐fixed in a 1.2% solution of osmium tetroxide. Electron micrographs of the vascular tissue show four cell forms which appear to be phases in the life cycle of the endothelium‐associated cell. Two of the phases are not encased and are characterized by their inclusions: in one cell these are crystalline, while in the second, they are amorphous and granular. In the other phases the cell is encased partially or completely within an apparently contractile fibrous wall surrounded by the plasmalemma. In the encased phases, the arrangement and condition of the cell organelles appears to have been changed, and in the fully‐encased phase mitochondrial activity seems to have decreased. This apparent change in the mitochondrial activity is accompanied by a thickening of the mitochondrial membrane from 48 to 109 Å. The micrographs seem to indicate that this cell in question behaves as a foreign body and, in some way, may be interacting with the epithelial tissue of the bulb

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1975.tb04582.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY