Estimated Sex Ratio Research Articles

GETTING PAST NATURE AS A GUIDE TO THE HUMAN SEX RATIO

Sex selection of children by pre-conception and post-conception techniques remains morally controversial and even illegal in some jurisdictions. Among other things, some critics fear that sex selection will distort the sex ratio, making opposite-sex relationships more difficult to secure, while other critics worry that sex selection will tilt some nations toward military aggression. The human sex ratio varies depending on how one estimates it; there is certainly no one-to-one correspondence between males and females either at birth or across the human lifespan. Complications about who qualifies as 'male' and 'female' complicate judgments about the ratio even further. Even a judiciously estimated sex ratio does not have, however, the kind of normative status that requires society to refrain from antenatal sex selection. Some societies exhibit lopsided sex ratios as a consequence of social policies and practices, and pragmatic estimates of social needs are a better guide to what the sex ratio should be, as against looking to 'nature'. The natural sex ratio cannot be a sound moral basis for prohibiting parents from selecting the sex of their children, since it ultimately lacks any normative meaning for social choices.

The human sex ratio: effects of maternal age

Previous studies suggest that stressful pregnancies may be associated with a lower proportion of male relative to female offspring. Low or high maternal age may represent stress for the fetus. Our aim was therefore to study whether the sex ratio differs by maternal age in all pregnancies, and in separate analyses, to assess the sex ratio in pregnancies complicated by pre-eclampsia, fetal death, preterm delivery or small for gestational age (SGA) offspring. Data from all births in Norway from 1967 through 2006, a total of 2 206 040 births, were used to estimate sex ratios (the number of male per 100 female offspring) according to maternal age. The analyses were done among all pregnancies, and within subgroups of complicated pregnancies. In addition, we estimated the odds ratio (OR) of having a male offspring by maternal age in all pregnancies with adjustment for pre-eclampsia, fetal death, preterm delivery or SGA offspring. Overall, there was no association of maternal age with the human sex ratio. In subgroups of complicated pregnancies (pre-eclampsia, fetal death, preterm delivery and SGA offspring) the sex ratio was increased. However in pregnancies with pre-eclampsia, the proportion of males decreased with increasing maternal age. In multivariable analyses including all pregnancies, with adjustment for complications, there was still no association of maternal age with offspring sex. However, in pregnancies with SGA offspring, the adjusted OR of delivering a boy at term was lower than expected (OR 0.87, 95% confidence interval 0.85-0.89). The lower proportion of male births at high maternal age in pregnancies with pre-eclampsia and in pregnancies with live born SGA offspring born at term, supports the hypothesis that male fetuses are more vulnerable to maternal stress than female fetuses. The main limitation of our findings is lack of statistical power due to small study subpopulations.

Effects of roads and crabbing pressures on diamondback terrapin populations in coastal Georgia

AbstractHuman activities, including the harvesting of natural resources and land development, place substantial pressure on wildlife. The diamondback terrapin (Malaclemys terrapin) is a small, estuarine species of emydid turtle in decline and at risk due to a suite of human activities. Vehicle‐induced mortality from increasing coastal traffic and bycatch mortality in crab pots have been recognized as 2 of the primary conservation concerns for terrapins. We used mark‐recapture estimates of terrapin density and sex ratio from repeated seining samples of 29 randomly stratified selected tidal creeks to evaluate the current relationships between road and crabbing pressures and the abundance, sex ratio, and size distribution of terrapin populations along the Georgia coast. We obtained 2005 captures of 1,547 individual terrapins among 29 tidal creeks sampled. Population density estimates ranged from 0 to 1,040 terrapins/km among tidal creeks with a median density of 65 terrapins/km. Among all sites, terrapin density declined with increasing crabbing activity within the creek, but was not related to proximity to roads. Sex ratios did not vary significantly with crabbing activity or proximity to roads; however, we found a significantly larger proportion of smaller‐sized terrapins in creeks with no crabbing activity. Although roads may have significant localized effects on terrapin populations, we found no measurable association between proximity to roads and current variation in terrapin density along the Georgia coast. However, we did find that terrapin density and the proportion of smaller sized individuals within the population were negatively associated with crabbing activities. Bycatch from commercial and recreational activities threaten many species. We add to a growing body of research showing crabbing activities are affecting diamondback terrapin populations across much of the species' range. States committed to the conservation of terrapins and coastal species should focus on reducing bycatch risk; for example by regulating soak times and locations, requiring the use of bycatch reduction devices, and removing abandoned or lost crab pots from coastal habitats. © 2011 The Wildlife Society.

Differential migration in the polygynandrous Alpine Accentor Prunella collaris

Capsule Differential migration by sex and age occurs in the Alpine Accentor Prunella collaris. Aims To characterize the wintering phenology of migrating Alpine Accentors, and to test for differences in sex and age ratios between wintering sites. Methods Alpine Accentors wintering at low elevation, in Mediterranean France, were monitored (census, ringing) over four winters. Individual arrival date, duration of stay and departure dates were analysed according to sex and age. Within‐day use of the site was characterized. Results were combined with previously published data to test for differential migration. Results Post‐breeding migration was recorded in November. Yearlings arrived 22 days later than adults at the wintering site. Females stayed longer (108 days) than males (77 days). The study site – a picnic place – was mainly used by the birds in the afternoon. Males departed earlier (22 February) than females (7 March). The inter‐annual return rate was 0.61 (without transients). Conclusion Combining these results with available estimates of age and sex ratios from other wintering populations revealed that female and yearling Alpine Accentors are more prone to migrate than adult males. Differential migration probably results from the ecological selective pressures faced by the species, particularly their high‐altitude breeding grounds and their polygynandrous mating system.

Bias associated with baited camera sites for assessing population characteristics of deer

AbstractCamera surveys often involve placing bait in front of the camera to capture animals more frequently, which could introduce biases in parameter estimates. From September 2008 to March 2009, we monitored cameras placed at random, along game trails, and at feed stations to determine if camera placement influenced measures of population demographics in a herd of white‐tailed deer (Odocoileus virginianus). There was no time period in which cameras placed at feed stations provided sex ratio and recruitment estimates similar to those acquired from randomly placed cameras. Trail‐based camera surveys provided population estimates similar to those from random sites and may provide a feasible alternative to using baited camera stations. © 2011 The Wildlife Society.

The effect of the predicted air temperature change on incubation temperature, incubation duration, sex ratio and hatching success of loggerhead turtles

Abstract Marine turtles are sensitive to temperature changes and thus are likely to be impacted by the predicted climate change. This study assesses the effect of the predicted air temperature change on incubation temperature, incubation duration, sex ratio and hatching success of the loggerhead turtle Caretta caretta at the Mediterranean nesting sites of Dalyan and Fethiye, Turkey. We recorded sand temperatures and used air temperatures at two nesting sites to estimate the sex ratio of hatchlings. The data showed that hatchling production was 59.1% and 77.7% at Dalyan in 2004 and 2009, respectively, and 72.2% and 72.3% at Fethiye at 2008 and 2009, respectively. Incubation temperature was positively correlated with both air temperature and distance to sea. Sex ratio estimation and incubation duration between the years 1993 and 2009 in Fethiye show polynomic trend lines. The best predictors of hatching success were distance to vegetation and wet depth of nest. We modelled the effects of incremental increases in the future air temperature of up to 10°C. We suggest that clutch death is not likely to begin until 3°C of warming, increasing from 5.3% to 100.0% with warming between 4°C and 10°C.

Sample Size Requirement in the Study of Subterranean Termite (Isoptera: Rhinotermitidae) Sex Ratio

The choice of an appropriate sample size is a neglected topic in termite sex ratio research because the literature contains a variety of sample sizes with most < 50 individuals. We compared the effect of sample size (from 25 - 800) on matching the ratio obtained from several Reticulitermes flavipes (Kollar) populations of 1600 individuals. This study showed that a sample size of < 50 is too small to estimate the actual sex ratio of a population. A sample size of at least 100 termites is required to provide ±10% error in a census of Reticulitermes sex ratios. The results should improve confidence in estimates of termite colony sex ratios, and we propose a standard sample size for such studies.

Promiscuous Expression of α-Tubulin II in Maturing Male and Female Plasmodium falciparum Gametocytes

BackgroundAntimalarial interventions designed to impact on the transmissible sexual stages of Plasmodium falciparum are evaluated by measurement of peripheral gametocyte carriage in vivo and infectivity to mosquitoes. Drug or vaccine-elicited effects may differentially affect the relative abundance of mature male and female sexual forms, and this can be measured by estimation of sex ratios before and after intervention in vivo and in vitro. Measuring the impact of anti-gametocyte drugs on sexual commitment of immature gametocyte stages in vitro is not currently possible as male and female parasites cannot be distinguished by morphology alone prior to stage IV.Methodology/Principal FindingsWe have modified an existing immunofluorescence-based approach for distinguishing male and female gametocytes during development in vitro, by using highly synchronised magnetically-enriched gametocyte preparations at different stages of maturity. Antibodies recognising α-tubulin II (males) and Pfg377 (females) were used to attempt to discriminate the sexes. Transcription of these two proteins was not coordinated during in vitro development, with pfg377 transcripts accumulating only late in development, immediately prior to immunofluorescent signals from the PfG377 protein appearing in stage IV gametocytes. Contrary to previous descriptions of this protein as male-specific in P. falciparum, α-tubulin II recognised both male and female gametocytes at stages I to IV, but evidence of differential expression levels of this protein in late stage male and female gametocytes was found. Using antibodies recognising PfG377 as the primary marker and α-tubulin II as a secondary marker, robust estimates of sex ratio in in vitro cultures were obtained for gametocytes at stage IV or later, and validated by light microscopic counts. However, sex ratio estimation was not possible for early stage gametocytes due to the promiscuity of α-tubulin II protein expression, and the relatively late accumulation of PfG377 during the development process.Conclusions/SignificanceThis approach is a feasible method for the evaluation of drug impacts on late-stage gametocyte sex ratio in in vitro studies. Additional sex-specific antigens need to be evaluated for sex ratio estimation in early stage gametocyte preparations.

Life-history traits of Amur sleeper, Perccottus glenii, in the invaded Vistula River: early investment in reproduction but reduced growth rate

In recent decades, Amur sleeper is one of the most invasive fish species in Eastern and Central Europe. Generally, it is assumed that success of an invasive species can largely depend on the plasticity of its life-history traits, e.g., indicated by higher investment in reproduction in the initial stage of its invasion. On the other hand, such energy allocation to production of gonads should negatively impact somatic growth rate. The aim of this article was to explore this phenomenon in a non-native population of Amur sleeper inhabiting artificial reservoir on a large lowland river in Central Europe. Through analysis of the population age structure, sex-dependent growth rate and life-history traits we assessed investment in reproduction and its possible relationship with growth pattern as well as compared the results with literature data from native and introduced range. Samples collected monthly from April 2005 to March 2006 were used to estimate sex ratio, GSI, fecundity, eggs diameter frequency over the year, duration of spawning season, and mode of spawning. Age structure was calculated from scales and the same data were also used to back-calculate standard length (SL) at age. The population in the Włocławski Reservoir was represented by eight age groups, and its life span was one of the longest recorded both in its natural range and introduced areas. The weight–length relationship showed that the Amur sleeper grew isometrically and there was no difference between females and males. Although the Amur sleeper growth rate was relatively slow in the Włocławski Reservoir, its increment in the first year of life was comparable to that in other introduced areas and higher than in its natural range. The female age of maturation (1+) found in the reservoir was earlier than observed in its natural range as well as in most introduced areas (2+, 3+). Female length at maturation was similar to that reported elsewhere. The back-calculated standard length (SL) of females and males showed that in the first two age classes (1 and 2) males achieved larger SL than females. Meanwhile, at age 3, 4 and 5, females were larger than males but these differences were insignificant, except for class 5. For both sexes the average annual increment of SL decreased with age but in females the increment was always higher than in males (P < 0.05). The growth rate differences between females and males resulted possibly from their unequal investment in reproduction. Multiple spawning in the Włocławski Reservoir lasted from April to the end of August and was almost 3 months longer than in other regions. Thus, this higher investment in reproduction displayed by, e.g., earlier maturation of females and longer spawning season in the Włocławski Reservoir, may contribute to invasive success of Amur sleeper in newly colonized areas; however, the costs of this strategy result in slower growth in older age classes.

Sex Ratio, Fecundity, and Models Predicting Length at Sexual Maturity of Redband Trout in Idaho Desert Streams

AbstractFactors affecting length at maturity and other important reproductive characteristics have not been investigated for Idaho redband trout Oncorhynchus mykiss gairdneri residing in desert streams. Prespawning redband trout were collected from nine streams, and estimates of length at sexual maturity, median age at maturity, sex ratio, and fecundity were developed along with models predicting length at maturity from physical stream conditions. Males first matured 1–2 years prior to females in seven of nine streams, while in the remaining two populations a few fish of both sexes first matured at the same age. Total length (TL) was strongly related (P &lt; 0.0004; n = 49) to fecundity (F) via the curvilinear function F = 0.0002TL2.5989. Redband trout residing in Idaho desert streams appeared to be less fecund than several other stream‐dwelling populations of Pacific salmon Oncorhynchus spp. The best estimate of sex ratio for all fish, including immature fish, was 1:1. The best two‐variable logit model for predicting length at maturity in males included stream order and conductivity, whereas the best model for females included drainage area above the sample site and stream gradient. These models can be used by fishery managers to estimate the total number of mature redband trout present in Idaho streams and, in combination with other data, can be used to approximate effective population sizes across southwestern Idaho desert stocks.

Blind Count Surveys of White-Tailed Deer and Population Estimates Using Bowden's Estimators

Conducting surveys from blinds when supplemental feed (bait) has been provided has not been evaluated for estimating parameters of ungulate populations. We conducted blind count surveys of white-tailed deer (Odocoileus virginianus) in a 214-ha enclosure in central Texas, USA, in 2007 and 2008 to address 2 main objectives: 1) to evaluate a blind count survey protocol developed for use on small parcels of land, and 2) to use data collected from blind count surveys to conduct simulations to evaluate the reliability of abundance and sex ratio estimates obtained from Bowden's estimator. In each year population abundance (2007: 60; 2008: 48) and sex ratio (M:F, 2007: 0.58; 2008: 0.71) were known as were sighting frequencies of every animal. The enclosure had 5 blinds and we baited each blind with corn. We encountered many deer during surveys because there were only 2 deer in 2007 and 1 deer in 2008 that we did not view from blinds ≥1 time. To evaluate bias and precision of abundance and sex ratio estimates we conducted 10,000 bootstrap simulations. We evaluated both parameters in relation to the percentage of each population marked, number of surveys conducted from blinds, and whether surveys were conducted in the morning, evening, or both morning and evening. Also, we evaluated abundance in relation to whether we identified animals with unique marks to individual, and we evaluated sex ratio in relation to intersexual distribution of marks. Abundance estimates were less biased and more precise when we uniquely identified all marked animals and 40–70% of the population was marked. Sex ratio estimates were less biased when 40–70% of the population was marked and surveys were conducted in the morning and evening. Sex ratio estimates, however, were less precise than abundance estimates. Unbiased estimates of white-tailed deer population parameters can be obtained from blind count surveys conducted on small parcels of enclosed land and when animals are baited.

Blind Count Surveys of White‐Tailed Deer and Population Estimates Using Bowden's Estimators

Abstract: Conducting surveys from blinds when supplemental feed (bait) has been provided has not been evaluated for estimating parameters of ungulate populations. We conducted blind count surveys of white‐tailed deer (Odocoileus virginianus) in a 214‐ha enclosure in central Texas, USA, in 2007 and 2008 to address 2 main objectives: 1) to evaluate a blind count survey protocol developed for use on small parcels of land, and 2) to use data collected from blind count surveys to conduct simulations to evaluate the reliability of abundance and sex ratio estimates obtained from Bowden's estimator. In each year population abundance (2007: 60; 2008: 48) and sex ratio (M:F, 2007: 0.58; 2008: 0.71) were known as were sighting frequencies of every animal. The enclosure had 5 blinds and we baited each blind with corn. We encountered many deer during surveys because there were only 2 deer in 2007 and 1 deer in 2008 that we did not view from blinds ≥1 time. To evaluate bias and precision of abundance and sex ratio estimates we conducted 10,000 bootstrap simulations. We evaluated both parameters in relation to the percentage of each population marked, number of surveys conducted from blinds, and whether surveys were conducted in the morning, evening, or both morning and evening. Also, we evaluated abundance in relation to whether we identified animals with unique marks to individual, and we evaluated sex ratio in relation to intersexual distribution of marks. Abundance estimates were less biased and more precise when we uniquely identified all marked animals and 40–70% of the population was marked. Sex ratio estimates were less biased when 40–70% of the population was marked and surveys were conducted in the morning and evening. Sex ratio estimates, however, were less precise than abundance estimates. Unbiased estimates of white‐tailed deer population parameters can be obtained from blind count surveys conducted on small parcels of enclosed land and when animals are baited.

Population structure and stock assessment of Hoplias malabaricus (Characiformes: Erythrinidae) caught by artisanal fishermen in river-reservoir transition area in Brazil

Hoplias malabaricus is a viable economic alternative for artisanal fishermen who used to live on the banks of rivers that now are dammed in Brazil. In order to preserve the species' natural stock, the main objectives of this study were to obtain bio-ecological information on this species reproduction, feeding dynamics and the description of the extent of its exploitation in river-reservoir transition area in Brazil. This way, from January to December 2005, different fishery catches were made with gill nets by artisanal fishermen, and a total of 426 individual H. malabaricus were obtained and sampled. From each specimen, the following biometric and biological data were analyzed: standard length, total weight, stomach contents, reproductive data such as sex, weight and gonadal maturation stage; with these data we estimated sex ratio, reproduction period and feeding habits. To assess growth parameters and infer on the degree of exploitation, the standard length frequency data were analysed using the FISAT (ELEFAN I) computer program. Data revealed a sex ratio of 0.8:1 (M:F), that reproduction occurs all year around, being more intense during spring and summer; it also showed that H. malabaricus is piscivorous. The growth parameters and mortality were estimated at: L(infinity) = 35.18 cm, k = 0.32 year, longevity = 9.3 years, Z = 1.25 years, M = 0.63 year and F = 0.62 year. The weight-length relationship was: In Wt = -3.1663+2.7456 In Lp. The yield-per-recruit analysis produced the following values: E = 0.496, E(max) = 0.916, E0.1 = 0.701 and E0.5 = 0.378. Overall, our data suggest that the stock of H. malabaricus is not yet overfished in the studied area.

Age and sex-specific variation in detectability of moose (Alces alces) during the hunting season: implications for population monitoring

The sustainability of wild ungulate harvests can be greatly enhanced if monitoring data are available to permit an adaptive management approach. Utilising data provided by hunters is potentially the most cost-effective approach. In Scandinavia, observations recorded by moose (Alces alces) hunters provide a range of indices of population density, composition and reproductive performance. These are routinely used in practical management, but there are still many questions about their accuracy and precision. In this study, we availed of the fact that virtually all individual moose on the island of Vega in central Norway were marked during the period 1992–2005. Thus, we were able to compare the observation indices provided by hunters to the known size and composition of the population. The results indicate that the hunter observation indices provided accurate estimates of variation in moose cow recruitment and twinning rates. The estimates of sex ratio closely followed the pattern of annual variation but showed a consistent pattern of over-estimating the proportion of males. Thus, males seem to visually expose themselves more often for hunters than do females. The density index, measured as number of moose seen per hunter day did not to the same extent follow the variation in population density, possibly because moose were more naive in the first years after hunting was introduced or because of reduced detection conditions due to increasing scrub and tree encroachment during the study period. The results are discussed in light of their application to management and the evolutionary pressures in moose anti-predator behaviour.

A novel approach to estimating the cost of male fertility restoration in gynodioecious plants

*In many gynodioecious plants, sex is determined by cytoplasmic male sterility genes (CMS) and nuclear male fertility restorers (Rf). Models predict that the costs of restoration are important determinants of population sex ratios. However, current approaches to the estimation of these costs require prior identification of CMS genotypes, information that is available for few species. *We tested a novel approach to estimating the cost of restoration in natural populations without determining CMS or Rf genotypes. We used estimates of pollen viability and offspring sex ratios from open- and hand-pollinated families of Lobelia siphilitica to test whether the cost of restoration, expressed as low pollen viability, is higher in populations with more females. *Among populations with CMS, we found that variation in pollen viability was higher in small populations with more females, as expected if the proportion of females within populations increases with the maximum cost of restoration. In controlled crosses, families with low pollen viability also produced fewer females, suggesting that variation in viability is primarily determined by the number and frequency of Rf alleles carried. *This approach to estimating the cost of restoration can be applied to other cytonuclear gynodioecious species, offering new opportunities for testing gynodioecy models in the wild.

Balanced Sex Ratio at Hatch in a Greater Sage-Grouse (Centrocercus urophasianus) Population

Only one estimate of sex ratio at hatch exists for Greater Sage-Grouse (Centrocercus urophasianus). Managers typically assume a ratio at the population level of approximately 2:1 (female:male), primarily on the basis of sex ratio in the harvest. We determined the sex of newly hatched young and unhatched Greater Sage-Grouse by amplifying a portion of the sex-linked CHD gene. Sex ratio for Greater Sage-Grouse in east-central Nevada was 0.51 ± 0.03 (SE; n = 272). We found no substantial difference in size between eggs that produced male chicks and those that produced females (44.5 ± 0.2 mm3 vs. 44.3 ± 0.3 mm3) or between the masses of male and female chicks (25.8 ± 0.3 g vs. 26.3 ± 0.3 g), which suggests that energetic cost investments by females were similar between offspring of different sexes. We also found no effect of female condition on differential investment in male versus female offspring. Given that adult survival does not differ substantially between the sexes in our study population (J. S. Sedinger unpubl. data), we suggest that this population may not contain 2 adult females to 1 adult male and that any bias in adult sex ratio is likely attributable to differential survival from hatch to first breeding.

A comparison of sex ratio, birth periods and calf survival among Serengeti wildebeest sub‐populations, Tanzania

AbstractAlthough adaptation and environmental conditions can easily predict demographic variation in most savannah ungulates, no study on demographic consequences arising from natural and anthropogenic factors among Serengeti wildebeest (Connochaetes taurinus) sub‐populations in Tanzania has been carried out. Here, I report estimates of annual sex ratio, calf and yearling survival rate and birth seasonality between resident and migratory sub‐populations to explore demographic patterns arising from the different age and sex structure. The results indicate significantly higher female‐biased sex ratios in the resident and almost even sex ratios among individual migrants. The calf recruitment estimated as mother: offspring ratios indicate a more synchronous birth in the migrant than the resident sub‐population. Also, birth seasonality in the migratory sub‐population coincided with seasonal variability of rainfall and the timing of the birth peak was more variable in the migrants than the resident sub‐population. The migratory sub‐population had a higher annual proportional mean calf survival estimate (0.84) than that of the residents (0.44) probably due to higher mortality resulting from predation in the western corridor. However, the proportion of yearling survival estimates was much lower (0.31) in the migrants and relatively higher (0.39) in the residents. Different demographic outcomes resulting from environment, predation, movements and ecological factors including resource competition have conservation implications for the two sub‐populations.

Methods of estimating natural sex ratios of sea turtles from incubation temperatures and laboratory data

In laboratory experiments, we determined pivotal temperature (29.6°C), i.e. the constant temperature yielding 50% of each sex, and pivotal incubation duration (57.3 d) for hawksbill turtles Eretmochelys imbricata (Agassiz, 1857) nesting on Mona Island, Puerto Rico. Based on the laboratory curves for sex ratio, predictions were made about sex ratio in field conditions. Temperature of natural nests provided a better prediction of the actual independently verified sex ratios than incubation duration. Predictions made from temperature were not highly sensitive to the exact specification of the thermosensitive period within incubation. Recommendations are made for estimating sex ratios of hatchlings on beaches for which there is currently no information. The pivotal temperatures for Mona Island hawksbill turtles were similar to those obtained previously for hawksbills nesting in Antigua and in Brazil, suggesting some conservatism in this characteristic. If pivotal temperatures are similar for different areas, then sex ratios of turtles hatching on thermally different beaches are likely to vary considerably. Implications for the impacts of global warming on sea turtles are also discussed.

First molecular estimate of sex-ratio of southern right whale calves, Eubalaena australis, for Brazilian waters

The southern right whale (Eubalaena australis) was one of the most intensively hunted whales between the 17th and 20th centuries in the southern hemisphere. Recent estimates indicate that today there are around 7000 whales, representing 5 to 10% of its original population. On the other hand, recent studies estimated that the population that migrates to the Brazilian coast grew by 14% from 1987 to 2003. However, there is no information about sex-ratio for adults or for calves in this region, which is an important parameter for understanding the biology of the species. We present here the first estimate of calves' sex-ratio of southern right whales found along the southern Brazilian coast, one of the most important wintering grounds for the species. Sex was molecularly indentified for 21 biopsies collected from calves between 1998 and 2002, along the coast of Rio Grande do Sul and Santa Catarina States, in southern Brazil. The sex-ratio was two females for one male, however, it was not statistically different (χ2 test, α = 0.05; df = 1) from the expected ratio of 1:1. This result is in accordance with the sex-ratio estimated for the species of all ages using external morphology (and behaviour information), as well as for most species of baleen whales.

Red King Crab Mating Success, Sex Ratio, Spatial Distribution, and Abundance Estimates as Artifacts of Survey Timing in Bristol Bay, Alaska

Red King Crab Mating Success, Sex Ratio, Spatial Distribution, and Abundance Estimates as Artifacts of Survey Timing in Bristol Bay, Alaska