摘要:

Life history strategy models in which female size depends on fecundity and male size on male‐male competition, are used to predict male and female size. Sperm competition alone—without any form of contest competition—cannot readily generate size ratios (male weight/female weight) greater than 1·0, and if sperm competition is very weak, small or even dwarf males are predicted. Increasing sperm competition increases male size, but only with high numbers of competing males can male size approach that of females. Size dimorphism is also affected by the ratio: growth rate/mortality rate in each sex. If this is higher in one sex, its size increases. Two trade‐offs in fish could affect this ratio but neither appears likely to yield size ratios above unity under sperm competition.Male‐male combat is capable of pushing male size beyond that of females, but male size seems never to exceed female size by more than one order of ten, whilst the reverse can proceed to many orders of ten (dwarf males), a pattern which applies generally in animals. Reasons for this asymmetry in size ratio include buffering effects of reducing growth rate (‘von Bertalanffy buffering’), and an asymmetry in the homeostatic effect of operational sex ratio (‘OSR buffering’). High adult male mortality and weak male‐male competition can generate dwarf males. A fundamental problem concerns why the sexes are often so similar in size: this may relate to sperm competition, size buffering effects, and many other features not considered i

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb03864.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb05643.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb05644.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Although typically life history and morphology are studied separately, they may evolve most often in concert. Therefore, a full understanding of the evolution of fish life‐history patterns may require exploration of the evolutionary interplay between components of life history and other aspects of phenotype. One of the most promising approaches to understanding phenotypic integration is population comparison. This approach is particularly effective when ancestralderived relationships are understood and when multiple populations can be inferred to have evolved derived character states independently. Here we provide an example of this approach using five allopatric populations of freshwater three‐spined stickleback (Gasterosteus aculcatusL.) that have diverged in response to differences in selection regimes among the lakes they inhabit. We demonstrate a relationship between one aspect of reproductive life history, clutch volume and relative body shape. The differences are consistent with those predicted on the basis of differences in trophic habit and overall body form. Finally, we discuss the value of particular groups of fish for use in comparative studies and explore the kinds of evolutionary issues that can be addressed through population compari

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb03865.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The effects of size‐selective fishing mortality on the growth of Atlantic cod (Gadus morhuuL.) in the southern Gulf of St Lawrence were investigated and compared between: (1) a period when fishing mortality was relatively high, growth was relatively rapid, and abundance low (1967–1972 year classes): and (2) a period when fishing mortality was lower, growth was slow, and density high (1977–1982 year classes). Cod first entered the fishery at age 3 during both periods. The 1967–1972 year classes (fast growing) were fully recruited to the fishery by age 5 or 6 and the fishery removed over twice as many fish from the lower than upper quartiles of length‐at‐age distributions for cod 4 to 10 years old (disproportionately high exploitation of slow‐growing fish). In contrast. the 1977–1982 year classes (slow growing) did not fully recruit to the fishery until age 9 or 10 and the fishery removed four times as many fish from the upper than lower quartiles of the length‐at‐age distributions for 4‐ to 10‐year‐old cod (disproportionately high exploitation of fast‐growing fish). The reduced mean lengths‐at‐age of the 1977–1982 year classes compared with the 1967–I972 year‐classes is consistent with the different patterns of exploitation of fast‐ an

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb03168.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The growth and changes in the standard deviation about mean length were measured for sole,Solea soleaL., and herring,Clupea harengusL., larvae from crosses of one or two males with one or two females. The sizes of sole larvae did not differ between crosses but the size variation increased faster with age when two females were used. Both maternal and paternal effects were detected for size at hatching in herring, but there was no parental influence on size variation. Size variation in herring larvae declined or was stable during the yolk sac stage and was not affected by the number of parents used for fertilizations.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb03866.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

In late November 1990 salmon parr,Salmo salarL., from the Girnock Burn in northern Scotland were either caught on their feeding territories (n=25) or trapped during downstream migration (n= 18). They were then housed in a laboratory rearing tank and their food intake and growth rates were tracked, until their smolting status was ascertained in the following May. Female fish were predominant in both groups; although the range of ages was the same, the total age of migrants was 2+ while that of residents was 1+. In November, compared to resident fish of the same year class, migrants were larger, heavier and in better condition. Although growth rates dropped during the winter in both groups before increasing in spring, migrants ate more and consistently grew faster than residents. In seawater tolerance tests conducted in May, more residents than migrants failed to adapt. These results confirm the suggestion that autumn migrants smolt in the following spring and suggest that they represent the faster‐growing component of their cohor

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb03867.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

In the pipefishSyngnathus typhleL. parental care is exclusively paternal. Males brood embryos in a brood pouch for about a month, providing nutrients and oxygen. The newborn juveniles are free‐swimming and no further care is provided. The influence of paternal length and number of newborn on juvenile weight and growth rate, and how in turn the latter relates to juvenile survival, were investigated. It was found, using partial correlations, that paternal length is significantly and positively correlated to weight of newborn, weight of a two‐week‐old juvenile and juvenile growth rate (weight increment day‐1). Furthermore, number of newborn is correlated negatively to weight of newborn, weight after two weeks and juvenile growth rate. In an experiment in which juvenile pipefish of different sizes were exposed to predation it was shown that larger juveniles survived better. It is concluded that, inS. typhle, large juvenile size and rapid juvenile growth positively influence offspring performance. Offspring performance is positively influenced by paternal length which, however, may be a consequence of larger males receiving larger eggs. The number of newborn, i.e. the number of siblings in the male's pouch, has a negative effect on offspring performance, independently of other factors. Thus, the results show that for males the benefits of having superior juveniles will be at the cost of having fewer of

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb03868.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Increasing circumstantial evidence indicates that the introduction of brown trout (Salmo truttaL.) to New Zealand has caused a widespread decline in native fish populations but few of the underlying mechanisms have been investigated. The possibility of spatial competition was investigated by comparing the microhabitat used by nativeGalaxias vulgarisStokell (Family Galaxiidae) that were sympatric and allopatric with brown trout. A range of microhabitat variables was measured from random locations whereG. vulgariswere present in the Shag River during the day.G. vulgarispreferred coarse substrates, using them as resting places, but showed no other microhabitat preferences. This pattern of microhabitat use did not change in the presence of brown trout although galaxiid densities were considerably lower. Experiments inin situstream channels confirmed that competition for space does not occur during the day even at high galaxiid densities. This situation changed dramatically at night, however, withG. vulgarisspending significantly more time in slower areas when trout were present.G. vulgarisfeeds on drifting invertebrates, so brown trout could affect the galaxiids deleteriously by forcing them to occupy less profitable feeding positions. Interspecific competition for space, perhaps combined with competition for food and predation by trout, could explain declines inG. vulgarispopulations.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb03170.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The relationship between metabolic rate of pike (Y, mgO2) and body weight (X, g) over the range 40–1291 gat 15° C is of the form: Y=aXb. For resting metabolic rate (Vo2, rest), the scaling coefficient,b, is 0.80 and for maximum metabolic rate measured after exhaustive swimming (V02, max),bis 0.99. Factorial metabolic scope (V02, max/ V02, rest) increases with body weight. Peak postprandial oxygen consumption (V02, ASDA) is a constant multiple of V02rest for any discrete meal (expressed as % of body weight) up to 10% body weight. V02ASDA after a single meal can utilize the entire metabolic scope (V02, max—V02, rest) of juvenile but not adult

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb03869.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY