摘要:

Seasonal variations in energy content of liver. gonads and muscle, and the condition factor (K) of mature hake, were investigated. High energy content values were found in the liver after spawning and during thegonadal restingperiod. Lowenergycontent valuesin liverand highenergycontent values in gonads were observed during the gonadal growth period. In some periods of the reproductive cycle, low values of energy content of muscle were found.The condition factor profile was similar to the energy content profile of liver and muscle. Physicochemical and biochemical properties of actomyosin were monitored by reduced viscosity and Mg2+‐ATPase activity. The profiles of these properties were similar to that of the condition facto

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb03587.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The growth dynamics of red, pink and white fibres of the caudal and pectoral fin muscles are described inCaransmalabaricus (Cuv.&Val.) in relation to their somatic growth. In all three fibre types growth occurred by an increase in fibre number and diameter in small size classes of fish and by an increase in diameter only in larger fish. The growth dynamics of the three fibre types were similar to those of the myotomal muscle fibres and paralleled the somatic growth pattern of this fish.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb03588.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Variation in growth rate, age at maturity, reproductive life span and reproductive investment was investigated in females only in seven populations of roach, Rutilus rutilus, in Norway. The growth rates of mature female roach were low, varying for most populations between 10 and 14 mm year.1At the most northern locality the growth rate was only 5.6 mm year1. Individual fecundity and gonadosomatic index (GSI) varied unsystematically between populations, but it was evident that the population with the lowest growth rate also had the lowest individual fecundity and GSI. Egg weight also varied between populations, the most northern population had a medium egg weight, thus, in harsh climatic conditions egg number is sacrificed for a relatively high egg weight. We found no further evidence for a trade‐off between egg number and egg size. Fecundity increased with length in all populations, whereas the variation in egg size and GSI for most populations did not covary with length or age. This fact, together with the high age at maturity in all populations and the long reproductive life spans supports the bet‐hedging theory of life‐history evolution. This is further supported by the fact that we did not find any correlation between the growth rates and the different descriptors of fi

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb03589.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The eggs of rainbow smelt were incubated at pHc. 4.5,c. 5.5 andcontrol (c. 6.8) for durations of 2–14 days to assess their vulnerability to acid precipitation. These eggs are likely to be exposed to marked pH depressions during their incubation in small streams owing to run‐off from snow melt and spring rains. Survival after 48 h exposure was not related to pH, although longer exposure to low pH significantly decreased survival. The developmental stage at initial exposure was also important in determining survival. Overall egg survival varied from 0–87% at pHc. 4.5,0–89% at pHc. 5.5, and 44–100% at control pH levels,

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb03590.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Blood lysozyme activity was determined in rainbow trout that were stressed by handling and transport, or suffered from acute ammonia poisoning. To optimize the lysoplate assay, the pH dependence of the lysozyme activity was studied. For serum and kidney lysozyme, the pH optimum was 5.5 to 6.0. Ventilation frequency and plasma glucoseconcentration of the fish were used as stress indicators. Less severely stressful situations, such as 30 min of handling, brought about either a stimulation or a suppression of the lysozyme activity. Strong stressors, such as transport lasting 2 h or acute water pollution, reduced the lysozyme level significantly. The decrease of lysozyme activity due to handling and transport persisted for 24 h, but the activity returned to normal within 2 weeks following confrontation with the stressor.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb03591.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

We analysed the effects of L‐amino acid combinations, tested at the same relative concentrations as in 500 mgl1of a filtrated Tubifex extract, on attraction and exploratory behaviour of juvenile carp, Cyprinus curpio L., in an olfactometer. Tubifex filtrate was significantly active in the range of concentrations tested (5 mgl−1, 50 mgl−1, 500 mgl−1, 5 gl−1). Maximum attraction was obtained in response to a concentration of 500 mg l−1. Soluble TCA fraction and a mixture of the 17 synthetic amino acids found in this fraction also showed significant effects on attraction and exploratory behaviour. Tests of the four chemical groups of amino acids gave the following results: acidic amino acids (aspartic and glutamic) did not produce significant activity. Basic amino acids (histidine, arginine and lysine) and polar, uncharged amino acids (glycine, serine, threonine, tyrosine, asparagine and glutamine) were ineffective as attractants but significantly increased exploration. Non‐polar amino acids (alanine, valine, leucine, isoleucine, phenylalanine, and methionine) showed significant effects on both attraction and exploration. In tests where different pairs of these amino acid groups were mixed it was shown that a combination of non‐polar amino acids and polar uncharged amino acids was the most effective in inducing both attraction and exploration. The simplest combination to have a significant effect on both attraction and exploration was alanine, valine and glycine.These results are discussed in the light of recent data on the role of free amino acids in the beha

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb03592.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The effects of interspecific competition from roach on gonad development in O+ and 1+ perch were studied in a pond experiment by varying the roach density between treatments. The proportion of mature O+ males first increased and, thereafter, decreased with increasing roach density and increasing somatic weight. O f females were immature and all I+ males were mature. The proportion of mature 1+ females decreased with increasing roach density and decreasing somatic weight. The gonad weight of O+ and 1+ males as well as 1+ females decreased with increasing roach density and decreasing somatic weight. For 1+ males, which were individually marked, both start weight as well as somatic end weight were positively related to gonad weight. One possibleexplanation for the hump shaped relationship between the proportion of mature O+ males and somatic weight is that behavioural interactions between O+ and I+ males in the absence of roach affected maturing in O+ males. This study supports previous suggestions that annual variation in resource availability may give rise to variance in fecundity‐body size relationship

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb03593.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Actinomycin‐D reduced gill Na+‐K+ATPase activity of chinook salmonOncorhynchus ishawytswha(Walbaum), smolts and saltwater‐adapted juveniles but had no significant effect on the enzyme activity of parr in fresh water. The similarity in response suggests that even though smolts are found in fresh water, their enzyme system is more characteristic of saltwater‐adapted juveniles than freshwater‐dwelling parr. A greater reduction in enzyme activity was found when fish were treated with actinomycin‐D in salt water than in fresh water, suggesting that the enzyme degradation rate wasgreater in salt water than in

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb03594.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The maximum growth rate of juvenile perch, PercaJuviatilis L., at different constant temperatures and in naturally changing day‐lengths was studied in the laboratory. Standard metabolic rate was studied in starvation experiments at constant temperatures under short‐ and long‐day conditions. Growth occurred in temperatures above 8 to 10°C. In winter, from mid‐October until mid‐April, maximal growth was considerably reduced and was relatively slow but constant. The standard metabolic rate was reducedc. 50% under short‐day conditions. The seasonal change in metabolic rates, presumably controlled by an endogenous rhythm, was considered to be an adaptation to low food availability during the short

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb03595.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Behavioural and metabolic reactions ofPomatoschistus minutus(Pallas) exposed to various degrees of hypoxia were studied. At 15°C and 20‰ mortality was 50% at 15.2% oxygen saturation. Avoidance and oxygen saturation showed a linear inverse relationship. At levels lower than 60% saturation increased activity occurred; avoidance was significant at 30% saturation. Active, routine and standard MO2correlated linearly with weight at 6 and 15°C (salinity = 19‰). During hypoxia at 15°C routine MO2rose significantly at 60–50% and 40–30% saturation expressed either as MO2during longer periods at night or MO2at shorter intervals during the day. Standard MO2was unaffected by hypoxia at 15°C. Haemoglobin concentration was significantly increased whenP. minutuswas acclimatized to 35%

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb03596.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY