Sex Ratios and Sexual Dimorphism Among Recently Transformed Sea Lampreys, Petromyzon marinus Linnaeus

1965 ◽  
Vol 22 (3) ◽  
pp. 695-711 ◽  
Author(s):  
Vernon C. Applegate ◽  
M. L. H. Thomas
Keyword(s):  
Sex Ratio ◽  
Seasonal Changes ◽  
Sex Ratios ◽  
Petromyzon Marinus ◽  
Similar Data ◽  
Effective Prevention ◽  
Rate Of Increase ◽  
Sea Lampreys ◽  
The Mean ◽  
Average Size

The sex, length, and weight were determined of nearly all recently transformed sea lampreys migrating downstream in the Carp Lake River, Michigan, in the fall, winter, and spring of 1960–61. Similar data were collected from samples of an earlier run in the Carp Lake River and of runs in three other tributaries of Lakes Huron and Michigan. The sex ratio of the 1960–61 migrants in the Carp Lake River was 324 males:100 females. Sex ratios of migrants in the other runs varied from 77 to 86 males:100 females. The high proportion of males in the 1960–61 run in the Carp Lake River is attributed to the effective prevention of recruitment of sea lampreys in the river and transformation of the females at an earlier age than is characteristic of the males. A near equal sex ratio among recently transformed migrants is considered normal for the species. The sex composition of a run changed during the period of migration. The proportion of males among the migrants was greatest at the beginning of the run and declined steadily thereafter. The average size was smaller for males than for females. Differences in the mean lengths and weights of the sexes were statistically significant. The length–weight relation differed for the sexes and showed a slower rate of increase of weight with increase in length than is characteristic of other stages of the animals' life cycle. Seasonal changes in the length–weight relation had a trend toward lower weights among the migrants coming downstream in the later months of the run.

Sex Ratios and Lengths of Adult Sea Lampreys (Petromyzon marinus) from a Lake Ontario Tributary

1974 ◽  
Vol 31 (1) ◽  
pp. 122-124 ◽  
Author(s):  
I. C. Potter ◽  
F. W. H. Beamish ◽  
B. G. H. Johnson
Keyword(s):  
Narrow Range ◽  
Sex Ratios ◽  
Petromyzon Marinus ◽  
Lake Ontario ◽  
Sea Lamprey ◽  
Adult Males ◽  
Sea Lampreys ◽  
Males And Females ◽  
The Mean ◽  
Humber River

The mean lengths of adult males and females of the sea lamprey (Petromyzon marinus) migrating into the Humber River from Lake Ontario in each of the years 1968–1972 varied little, and were similar to those found by other workers in recently established populations in the upper lakes. In contrast, the ratio of males to females, which lay within the narrow range of 1:1 to 1.26:1, was similar to those reported for long-established populations.

Biased sex ratios and parasite mating probabilities

Parasitology ◽  
1993 ◽  
Vol 107 (3) ◽  
pp. 287-295 ◽  
Author(s):  
R. M. May ◽  
M. E. J. Woolhouse
Keyword(s):  
Population Dynamics ◽  
Sex Ratio ◽  
Mating System ◽  
Sex Ratios ◽  
Theoretical Framework ◽  
Main Body ◽  
Female Mating ◽  
The Mean ◽  
Mated Female

SummaryAn earlier paper (May, 1977) developed a theoretical framework for exploring the consequences of dioecy for the population dynamics of schistosomes, assuming an unbiased sex ratio. This paper extends the analysis to biased sex ratios, as have been reported in practice. We consider the relationships of the mean number and distribution of worms among hosts, the sex ratio, and the mating system (monogamous or polygamous) to: (i) the female mating probability, Φ the prevalence of mated female worms. Ω: and (iii) the mean number of mated female worms per host, ξ. Among other results, we show how high values of Φ are associated with male-biased sex ratios and polygamous mating; that Ω is independent of the mating system and is relatively unaffected by the sex ratio; and that ξ is maximal for unbiased sex ratios given monogamous mating, and for female-biased sex ratios if mating is polygamous. These results, together with the confounding effects of the mean number and distribution of worms, are described in detail in the main body of the paper.

scholarly journals Variance-effective population number: the effects of sex ratio and density on the mean and variance of offspring numbers in the flour beetle, Tribolium castaneum

1984 ◽  
Vol 43 (3) ◽  
pp. 249-256 ◽  
Author(s):  
Michael J. Wade
Keyword(s):  
Experimental Study ◽  
Sex Ratio ◽  
Tribolium Castaneum ◽  
Sex Ratios ◽  
Effective Number ◽  
Effective Population ◽  
Population Number ◽  
Flour Beetle ◽  
Mean And Variance ◽  
The Mean

SUMMARYI report the results of an experimental study of the effects of sex ratio and density on the mean and variance in offspring numbers in both sexes of the flour beetle, Tribolium castaneum. The variance-effective number is estimated from the observed variance in offspring numbers using the methods of Crow & Morton (1955).Both the mean and the variance in offspring numbers were found to vary with sex ratio and density; as was found in previous studies (Wade, 1980), males were generally more variable in offspring numbers than females. The ratio of variance to mean progeny numbers in each sex was approximately unity at all sex ratios.

scholarly journals SEBARAN UKURAN PANJANG DAN NISBAH KELAMIN IKAN MADIDIHANG (Thunnus albacares) DI SAMUDERA HINDIA BAGIAN TIMUR

2015 ◽  
Vol 7 (3) ◽  
pp. 175
Author(s):  
Arief Wujdi ◽  
Bram Setyadji ◽  
Budi Nugraha
Keyword(s):  
Sex Ratio ◽  
Size Composition ◽  
Thunnus Albacares ◽  
Chi Square ◽  
Resources Management ◽  
Fisheries Resources ◽  
The Mean ◽  
Average Size ◽  
Chi Square Analysis ◽  
Size Mode

Ikan madidihang atau tuna sirip kuning (Thunnus albacares) merupakan salah satu komoditas penting bagi industri perikanan di Indonesia dengan hasil tangkapan tertinggi dibandingkan jenis tuna lainnya. Sebagai dasar pengelolaan sumberdaya ikan yang berkelanjutan, diperlukan data dan informasi tentang komposisi ukuran layak tangkap yaitu membandingkan proporsi rata-rata ikan tertangkap (Lc) dan matang gonad (Lm), serta nisbah kelamin sebagai indikator pendugaan kemampuan memijah. Pengumpulan data dilakukanmelalui program observasi diatas kapal rawai tuna yang berbasis di Benoa, Pelabuhanratu dan Bungus dari bulan Agustus 2005 hingga November 2013. Penghitungan nisbah kelamin menggunakan uji Chi-Square (X2) dengan tingkat kepercayaan 95%. Hasil penelitian menunjukkan bahwa distribusi ukuran panjang cagak ikan madidihang berkisar antara 30-179 cm, modus ukuran 106-110 cm dan rata-rata 101,65 cm. Sebanyak 81,03% madidihang yang tertangkap berukuran lebih besar daripada Lm yang berarti telah layak tangkap. Nisbah kelamin betina:jantan adalah 1:1,45 mengindikasikan dominansi ikan jantan. Hubungan antara nisbah kelamin dengan panjang ikan menunjukkan signifikansi dimana ikan betina semakin berkurang pada ukuran 120-180 cm, serta tidak ditemukan lagi pada ukuran lebih dari 170 cm. Korelasi nisbah kelamin dan panjang cagak dapat dideskripsikan dengan persamaan regresi sebagai berikut: 1,8013 - 0,0099 FL dengan nilai R2=0,8058.Yellowfin tuna or YFT (Thunnus albacares) is one of the important commodity for the fishing industry in Indonesia because it has the highest catches compared with other tunas. In order to fisheries resources management, it was necessary to monitor the size composition compared between proportion average size captured (Lc) and maturity size (Lm) to meets the size eligibility, as well as the sex ratio as an indicator to estimate the ability of spawn. Data collected by scientific observers program which was following tuna longline operation mainly based in Benoa, Palabuhanratu and Bungus Fishing Port, from August 2005 to November 2013. Chi-Square analysis with 95%confidence level also implemented to determine sex ratio between female and male. The result indicated that YFT were caught has size ranged between 30-179 cm, size mode ranged between 106-110 cm and the mean was 101,65 cm.Mostly YFT (81,03%) was greater than its maturity size (Lm) and that’s mean have been worthy to be captured. Sex ratio of (F:M) 1:1,45 was observed which indicates male was dominant. Correlation between sex ratio and length proved to be significant where the female was diminishing in size between 120-180 cm, even female was no longer found in size more than 170 cm. Correlation between sex ratio and length can described as a regression equation=1,8013 - 0,0099 FL; R2=0,8058.

Biased sex ratio and niche restriction in Baruscapillaria obsignata (Madsen 1945) (Nematoda, Capillariidae) from Columba livia (Aves, Columbidae)

2011 ◽  
Vol 86 (4) ◽  
pp. 401-405 ◽  
Author(s):  
S. D'Ávila ◽  
E.C.A. Bessa ◽  
S. Souza-Lima ◽  
M.L.A. Rodrigues
Keyword(s):  
Sex Ratio ◽  
Negative Binomial ◽  
Sex Ratios ◽  
Columba Livia ◽  
Nematode Species ◽  
Intensity Of Infection ◽  
Factors Influencing ◽  
Biased Sex Ratio ◽  
The Mean ◽  
Male Sex

AbstractIn the present study populations of the avian nematode species Baruscapillaria obsignata are described from Columba livia. Male and female individuals were obtained from 27 birds, fixed in alcohol/formalin/acetic acid (AFA) and preserved in 70% ethanol. Nematodes were identified and then counted under a stereoscopic microscope. Baruscapillaria obsignata were much more frequent in the anterior third of the small intestine, and females were more abundant than males in all infra populations. The prevalence was 55.6%, mean intensity was 11.8 (median 11.0; range 1–31) and abundance 6.56. In the present study, we observed an aggregated distribution of parasite infrapopulations, as demonstrated by the value of the exponent of the negative binomial distribution, K = 0.2773; by the discrepancy index, D = 0.656 and by the variance/mean ratio, 12.44. The female/male sex ratios found in all infrapopulations were always greater than 1, showing a bias in favour of female abundance. This tendency was especially marked in infrapopulations containing fewer individuals. The sizes of infrapopulations ranged from 5 to 31 individuals. The mean sex ratio observed was 2.69 ± 3.28 (median 1.83; range 0–11). In infrapopulations with 5–15 individuals, the sex ratios observed varied from 2.6 to 11, while in those with 17–31 individuals, the sex ratios were lower, ranging from 1.7 to 2.4. There was a negative correlation between the intensity of infection and the sex ratio of infrapopulations. Results are discussed in terms of possible factors influencing the processes that lead to niche restriction and biased sex ratios in parasite infrapopulations.

Returns of Hatchery-Reared Lake Trout in Southern Lake Superior, 1955–62

1967 ◽  
Vol 24 (2) ◽  
pp. 281-298 ◽  
Author(s):  
Richard L. Pycha ◽  
George R. King
Keyword(s):  
Lake Trout ◽  
Lake Superior ◽  
Petromyzon Marinus ◽  
Salvelinus Namaycush ◽  
Osmerus Mordax ◽  
Commercial Fishery ◽  
Sea Lampreys ◽  
Average Size ◽  
Better Than ◽  
Made In

Experimental plantings of fin-clipped lake trout (Salvelinus namaycush) of various ages have been made in southern Lake Superior since 1952. The catch of planted lake trout by the commercial fishery was used to measure the success of stocking. Estimates of total returns were based on samples of 8.2 to 21.2% of the Wisconsin catches in 1955–62 and 36.4 to 46.8% of the Michigan catches in 1959–62. Marked lake trout were assigned to various plantings according to the fin mark, length of fish, readings of age from scales, and locations of capture.Estimated returns from Wisconsin plantings of 9-month-old lake trout varied from 2.1 to 6.4%. Wisconsin releases of 16-month-old fish yielded returns of 5.7 to 37.3%. Returns from plantings in Michigan were 0.3% for 9-month-old fish and 1.5 to 3.8% for 16-month-old fish. The ratios of the returns from plantings of 16-month-old fish to those of 9-month-old fish were 3.9:1 for Wisconsin releases and 6.7:1 for Michigan releases. Lake trout planted in Wisconsin generally survived better than those released in Michigan. Returns from fish planted at ages of 17 to 40 months in Michigan in 1958–59 were far greater than those from 16-month-old fish released in Michigan, but were not as high as from the most successful plantings of 16-month-old fish in Wisconsin. Lake trout released in 1960 from shore and from boats survived equally well.Average size of lake trout at release was more closely related to survival than any other factor. All except 1 of 10 highly successful releases were of fish larger than 22 per lb, and all 6 poor releases were of fish smaller than 34 per lb. Fish that ran 22 to 33 per lb survived only moderately well. A size of 17 to 20 fish per lb appears to be close to optimum.Abundance of native lake trout, American smelt (Osmerus mordax), and sea lampreys (Petromyzon marinus) all appeared to be unrelated to stocking success. The only apparent method of rapidly improving the success of stocking is to rear all lake trout to an average size of 17 to 20 per lb.

System Simulation of the Predatory Activities of Sea Lampreys (Petromyzon marinus) on Lake Trout (Salvelinus namaycush)

1975 ◽  
Vol 32 (5) ◽  
pp. 623-631 ◽  
Author(s):  
Patrick F. Lett ◽  
F. W. H. Beamish ◽  
G. J. Farmer
Keyword(s):  
Lake Trout ◽  
Petromyzon Marinus ◽  
Salvelinus Namaycush ◽  
Commercial Fishing ◽  
Stochastic Dynamic ◽  
Age Classes ◽  
Trout Population ◽  
Sea Lampreys ◽  
Population Structures ◽  
The Mean

A stochastic dynamic model was developed to evaluate the simulated and empirical interactions between sea lampreys (Petromyzon marinus) and two lake trout (Salvelinus namaycush) population structures, one without and the other with previous lamprey predation.An arithmetic increase in lampreys induced a geometric decline in trout, which was dependent on the number of age-classes and the mean weight of trout. Large trout, when present, were subject to most of the lamprey predation allowing survival of smaller trout. Lethality increased exponentially with lamprey size resulting in peak lake trout mortality during fall near the end of the lamprey’s feeding period. Lake trout scarring data could be used only as an index of lamprey abundance when trout:lamprey ratios and trout population structures were known. The simulation suggested that sea lampreys and lake trout could coexist if large trout are not removed by commercial fishing and if some exogenous factor controlled lamprey abundance.

Observations on reproduction in a pedigree herd of Large White pigs

1956 ◽  
Vol 47 (3) ◽  
pp. 332-343 ◽  
Author(s):  
J. S. Perry
Keyword(s):  
Litter Size ◽  
Average Duration ◽  
Ordinal Number ◽  
Gestation Period ◽  
Similar Data ◽  
Large White ◽  
Apparent Relationship ◽  
The Mean ◽  
Average Size ◽  
Duration Of Pregnancy

1. The information analysed in this report is taken from records of the Compton herd of Large White pigs over a period of about 4 years.2. Length of gestation period: close concentration about the mean of 114·17 days; no apparent relationship between litter size and extremely long or short gestation period. There was no difference in the average duration of pregnancy as between old and young sows, nor was there any evidence of a characteristic tendency to long or short pregnancies in individuals. The incidence of stillbirths appears to be independent of the length of the gestation period.3. The number of pigs born, alive or dead, ranged from 3 to 24, the average being 13·12. The average number of pigs born alive was 12·4 and the average number weaned was 8·1.4. The average number of pigs born rose with successive pregnancies to a maximum of more than 15 in the 6th and 7th litter and declined thereafter. The average number born alive reached a maximum of more than 14 in the 5th litter and declined thereafter, the decline being less marked among pigs born alive than among all pigs including stillbirths, apparently because embryonic mortality (before parturition) bears more heavily on the litters of older sows, whereas the incidence of stillbirths is not related to age (or to the ordinal number of the litter).5. The incidence of stillbirths was studied in relation to litter size, the data being compared with similar data recorded elsewhere. The proportion of stillbirths was higher among female piglets than among males. The reverse was true in litters of less than average size, and the possible significance of this difference between smaller and larger litters is discussed.6. The foetal sex ratio appears to bear no relation to the ordinal number of the litter or to its size.7. The reasons for discard of sows which have been culled during the period under review have been recorded and are briefly discussed.

Effect of density and individual variation on growth of sea lamprey (Petromyzon marinus) larvae in the laboratory

1992 ◽  
Vol 70 (1) ◽  
pp. 184-188 ◽  
Author(s):  
Scott P. Murdoch ◽  
Margaret F. Docker ◽  
F. William H. Beamish
Keyword(s):  
Sex Ratio ◽  
Standard Error ◽  
Individual Variation ◽  
Petromyzon Marinus ◽  
Sea Lamprey ◽  
High Density ◽  
Initial Length ◽  
Subcutaneous Injections ◽  
Length Standard ◽  
The Mean

Sea lamprey (Petromyzon marinus) larvae were individually marked with subcutaneous injections of latex dye and maintained in the laboratory from June 1988 to February 1989 at tank densities of 10, 50, and 100 larvae per 0.3 m2 of substrate. Growth, measured as change in total length and weight, varied widely among individuals: change in length during a 3-month period differed by as much as 17.0 mm within one tank of 10 larvae. Despite individual variation, growth decreased significantly with increasing density: the mean increase in length (± standard error) over the 8-month period was 17.3 ± 3.0, 4.3 ± 1.5, and −1.4 ± 1.0 mm at low, medium, and high density, respectively. The initial length or the sex of an individual at the end of the experiment had little or no effect on growth. Mortality was negligible (1.6%), and could not be significantly correlated with density, size, or sex. The overall sex ratio was 33% male, and did not vary significantly with tank or density.

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