摘要:

Winter flounder from known locations were sorted according to their reproductive status about 4 weeks before spawning. Five groups were then fed to satiation and three groups were not fed. The experiment was terminated at the end of the summer feeding season. At termination, only one of the recently spawned fish with restricted feeding showed gonad recrudescence. Conversely, all previously reproductive fish which had been fed to satiation showed gonad recrudescence. Fish fed to satiation included some which had been initially designated non‐reproductive post‐mature. These experiments indicate that a non‐reproductive post‐mature state is inducible and may be reversible, with the switch related to nutritional

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1987.tb05793.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

A simple method for distinguishing fish populations using monogenean sclerites is described. Monogeneans are left in a drop of 45% acetic acid on a microscope slide for a few minutes, and squashed under a cover slip to spread the hamuli and genital hooks in one plane. Hamuli and hooks are then measured with the aid of measuring eyepieces. Measurements of sclerites ofKuhniaandPseudokuhniafixed directly in 10% formalin or fixed in 10% formalin after freezing for several days gave the same results. Prerequisites for the use of the method are that monogeneans occur in sufficient numbers and show distinct geographical variation. The method is easiest to use if the size of sclerites does not change with body growth.Kuhnia scombri(Monogenea: Polyopisthocotylea) from the mackerel,Scomber australasicus, in New Zealand and New South Wales differ significantly in the length of the hamuli; it is concluded that there may be different populations of mackerel at the two localities. There also are different populations ofScomber japonicusin Japan and Ecuador, and sympatric populations ofS. japonicusandS. australasicusin Japan harbour identical populations of the monogeneansPseudokuhnia minorandKuhnia sprostonae.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1987.tb05794.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Pike were adapted to both fresh water and brackish water (salinity 2.2‰) conditions prior to measurements of blood pressure, electrolyte composition and renal function both before and after administration of either 3.75 μg calcitonin kg−1body weight or acetate saline. This protocol was designed to test the ability of calcitonin to affect significantly the fluid and electrolyte status of fish exposed to varying salinity. Whilst in freshwater‐adapted animals the plasma content of calcium and magnesium was significantly depressed following calcitonin injection, no corresponding effect was seen following 2.2‰ salinity brackish water‐adaptation. Moreover, no significant changes were apparent in renal function of pike adapted to either medium. It is concluded from these experiments that calcitonin in pike may play some part in extra‐renal control of plasma calcium and magnesium content in fresh water but that it is unable to affect significantly the measured plasma ion content of brackish water‐a

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1987.tb05795.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Naturally‐occurring acidified water was used in a factorial experiment to study the effects of acidity and duration of acidic conditions on short‐term survival of late larvae of perch. The analysis demonstrated that both factors influenced probability of survival. When the duration of acidic conditions exceeded 2 days, acidity alone could be used as a predictor of survival. At pH values below 4.5, and durations of 6–24 h, unexpectedly high survival rates were observed. Analyses of the concentration of total and soluble aluminium suggested that aluminium chemistry played a significant part in determining the observed survival pa

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1987.tb05796.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

A laboratory study of femaleG. aculeatusrevealed no conclusive evidence of active female mate choice on the basis of male aggression levels. However, highly aggressive males failed in 95% of all choice tests. The less aggressive ‘chosen’ males were generally successful again in subsequent trials with the same female, and certain males were consistently successful with different females. Females exhibited an increased readiness to spawn at the end of the reproductive season, although the same males were usually selected ag

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1987.tb05797.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The biology of two populations ofSpratelloides lewisi, one from the Ysabel Passage and the other from Cape Lambert, were studied during 1980 and 1981. A total of 2201 specimens ofS. lewisiwere collected from a regular sampling programme of tuna bait‐fish catches. The annual length frequency distributions for both populations indicated differences in the full recruitment length and maximum size attained between the two populations. The age and growth ofS. lewisiwas described at both locations by von Bertalanffy growth curves fitted to length‐at‐age data obtained by reading the daily growth increments of the sagittae. Ovarian maturation data suggested there was no distinct spawning seasonality for this species: spawning was either protracted or markedly reduced over several months. The total annual mortality rates for both populations ofS. lewisiwere high, but consistent with those of other short‐lived fishes. An estimate of the natural mortality rate for the Ysabel Passage population ofS. lewisiby an empirical method corresponded very closely to another estimate based on the relationship between total mortality and fishing

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1987.tb05798.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Crowding for 3 weeks significantly reduced the coefficient of condition of both brown trout and rainbow trout. However, acclimation of the hypothalamic‐pituitary‐interrenal (HPI) axis, as assessed by changes in plasma cortisol levels, occurred within 6 days for brown trout and within 10 days for rainbow trout. Blood lactate levels were significantly reduced in the crowded fish of both species throughout the experiment. Sexual maturation of the male fish significantly elevated the number of circulating red blood cells in both species, reduced the lactate levels in brown trout and elevated cortisol levels in the rainbow trout. Despite the relatively rapid interrenal acclimation, the numbers of thrombocytes and lymphocytes in the blood of both species were significantly reduced during the period of crowding and it is concluded that changes in the composition of circulating blood cells are more reliable indicators of chronic crowding stress than are plasma cortisol levels. These findings are discussed in relation to the role of the HPI axis in suppressing the defence systems of salmonid fish during periods of chronic str

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1987.tb05799.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The dispersal and migration of farmed Atlantic salmon,Salmo salar, allowed to escape during the summer was studied. Three groups of 4–year–old fish of the River Imsa stock were released in coastal waters off south‐western Norway: one group, with functional olfactory organs, was released at a fish farm 4 km away from the R. Imsa; two other groups, one with transected olfactory nerves and the other with functional olfactory organs, were released in the sea 90 km from the R. Imsa. To compare them with the migration pattern of reared, large smolts of the Imsa stock, a group of 3 + smolts was released in the R. Imsa.Adults of salmon released as 3–year–old smolts homed with high precision to the R. Imsa. Four– year–olds released in the sea were recaptured in the fjord and in the coastal current, the majority north of the places of release. Immatures migrated to feeding areas in the North Atlantic. Matures seemed to enter rivers at random when ready to spawn. There was no difference in migration pattern between anosmics and controls. The olfactory sense was not mandatory for entering fresh water. The results indicate that the homing behaviour of Atlantic salmon is not a direct consequence of a single imprinting of the smolts, and that there is not a direct genetic link for return to a particular river. The present results support the sequential imprinting hypothesis proposed by Harden

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1987.tb05800.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Transfer of immunity to horse erythrocytes (HRBC) by immune lymphoid cells was performed to analyze the kinetics of adoptive immunity in the clonal ginbuna crucian carp,Carassius auratus langsdorfti. Immune lymphoid cells were intravascularly transferred to the unprimed recipients and then recipients were evaluated by measuring the antibody titre of the plasma. Antibody productivity was most successfully conferred by splenic cells, followed by pronephric and mesonephric cells, taken from immune donors 7 days post‐immunization, while transferability by thymic cells was lacking or very low, even if possible. Peak response of plaque‐forming cells (PFCs) was observed at 5–7 days after the first injection, and the maximum number of PFCs at peak response was almost the same in all organs examined, such as the pronephros, mesonephros, spleen and the thymus. Direct correlation between transferability and number of PFCs was not observed on individuals, although the peak of transferability corresponded to that of the PFC response. Preliminary experiments of cell transfer by separated pronephric cells showed that the lymphocyte‐rich fraction was more effective than the bottom fraction containing fewer lymphocytes in transferring immune reactivity. These results suggest that cells involved in transferring immune reactivity are B lymphocytes, composed of different developmental stages and distributed differently in the different lymphoid

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1987.tb05801.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The size at maturity in many male poeciliid fish is believed to be controlled by ‘social control mechanism’, and post‐maturation growth is insignificant. In the Clear Creek gambusia,Gambusia heterochir. post‐maturation growth in male fish is limited. Male G.heterochirmatures at a fixed size, and age of maturation is dependent on environmental factors (e.g. temperature). In the presence of an adult male, the maturation size of a young male is largely determined by genetic factors rather than ‘social control’ factors. A male can switch its status as a ‘dominant’ or ‘subordinate’ male, depending on the relative size of rival males in mating competition. Mating success of a large (dominant) male reduces as the number of competing small (subordinate) males increases. These unique reproductive tactics may explain in part why ‘social control mechanism’ does not play a key role in determining the maturation si

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1987.tb05802.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY