Sex Ratio Patterns Research Articles

Population dynamics and reproductive features of the Amazon River prawn Macrobrachium amazonicum (Heller, 1862) in Neotropical reservoirs under drought events

Here, we describe population and reproductive dynamics of four populations of Macrobrachium amazonicum in reservoirs during drought events. Additionally, we analyze possible phenotypic changes in this species promoted by fish predation. Two populations had a large-size phenotype (with large body proportions and morphotypes in males) while a small-size phenotype (with reduced sizes and no morphotypes) was found in the two other populations. Overall, females were larger than males and there were varying sex ratios among the four studied populations. All populations had bimodal or polymodal patterns in their monthly size-class frequency, suggesting a seasonal influence and a potentially great capacity of these populations to adapt to adverse environmental conditions. No major changes were found in the patterns of sex ratio, recruitment, frequency of (larger) male morphotypes and female ovarian development stages during drought events. Macrobrachium amazonicum is a resilient species and undergoes continuous reproduction. Females with immature ovaries were predominant in all populations, performing multiple spawns and exhibiting rapid ovarian development cycles. In males, the initial morphotype (TC - translucent claw) was predominant in populations with a social hierarchy. Males of dominant morphotypes (GC1 and GC2 - green claw 1 and 2) use more energy to carry out and maintain metabolic processes, which could probably one of the explanations why their number in populations are limited. We did not find any clear evidence that fish predation affected phenotypes, suggesting that phenotypic plasticity could be more related to intrinsic factors, which would have to be further investigated.

Hydroelectric dam impacts shorten and delay the reproductive periods of female leaf-nosed bats in Western Amazonia

Abstract The life cycles of bats are constrained by availability of resources such as food and shelter. Disruptions limiting otherwise naturally regulated access to these resources ultimately affect the fitness of bat populations and may eventually lead to local extinctions. We sampled bats before and after an Amazonian mega-dam water filling and retrieved data on their reproductive phenology, testing if and how sex ratio, seasonal abundance, and reproductive patterns respond to impacts of the newly operating hydroelectric dam. We analyzed data from 3,298 bat captures of 49 species. Females outnumbered males, previously and after the dam implementation, and we observed seasonal variations in the abundance of bats, which was lower after the implementation of the dam for most species. All species had at least 1 reproductive peak of pregnancy and/or lactation beginning at a variable time across seasons. Most species and functional ensembles were reproductively bimodal, with exceptions being the polymodal Artibeus obscurus and unimodal Phylostomus elongatus. Operations of the hydroelectric dam affected the abundance of both sexes equally, and effects were stronger in the rainy season, altering the timing of reproduction for females, delaying and shortening pregnancy and lactation. These changes expressed in female reproductive activity may be related to the shortfall of resources because of loss of irreplaceable vegetation caused by the dam filling. As we cannot predict the roles of variation of reproductive patterns observed after the filling in the long run we reinforce the importance of long-term, continuous monitoring and management to safeguard the reestablishment of reproductive patterns of females in order to repopulate and keep bat populations healthy in remaining areas along following dam construction.

Patterns of Sex Ratio and Child Sex Ratio: Global to National Level Scenario of Last Few Decades

An effort has been made to examine the patterns of sex ratio and child sex ratio from last few decades in the world with special reference to India. This study is based on secondary data which is obtained from United Nations Population Division, Department of Social and Economic Affairs, World Population Prospects: 1992, 2002 and 2015 Divisions and Census of India. The study identifies the driving factors responsible for global to national level variations in terms of sex ratio and child sex ratio. It has been found that the sex ratio and child sex ratio of the Asian continent are skewed as compared to other parts of the world. Moreover, the present study pointed out that these adverse trends of sex ratio and child sex ratio of Asia are attributable to the introduction of sex-determination technologies, their widening supply and highly practiced sex-selective abortions. It has been observed that the strong patriarchal culture of Asia also contributes towards the widening of this gender gap. In India, the study shows that the north-eastern, eastern and southern parts of the country have reported relatively high child sex ratio as compared to northern, north-western and western parts.

Climate warming and sea turtle sex ratios across the globe.

Climate warming and the feminization of populations due to temperature-dependent sex determination may threaten sea turtles with extinction. To identify sites of heightened risk, we examined sex ratio data and patterns of climate change over multiple decades for 64 nesting sites spread across the globe. Over the last 62 years the mean change in air temperature was 0.85°C per century (SD = 0.65°C, range = -0.53 to +2.5°C, n = 64 nesting sites). Temperatures increased at 40 of the 64 study sites. Female-skewed hatchling or juvenile sex ratios occurred at 57 of the 64 sites, with skews >90% female at 17 sites. We did not uncover a relationship between the extent of warming and sex ratio (r62 = -0.03, p = .802, n = 64 nesting sites). Hence, our results suggest that female-hatchling sex ratio skews are not simply a consequence of recent warming but have likely persisted at some sites for many decades. So other factors aside from recent warming must drive these variations in sex ratios across nesting sites, such as variations in nesting behaviour (e.g. nest depth), substrate (e.g. sand albedo), shading available and rainfall patterns. While overall across sites recent warming is not linked to hatchling sex ratio, at some sites there is both is a high female skew and high warming, such as Raine Island (Australia; 99% female green turtles; 1.27°C warming per century), nesting beaches in Cyprus (97.1% female green turtles; 1.68°C warming per century) and in the Dutch Caribbean (St Eustatius; 91.5% female leatherback turtles; 1.15°C warming per century). These may be among the first sites where management intervention is needed to increase male production. Continued monitoring of sand temperatures and sex ratios are recommended to help identify when high incubation temperatures threaten population viability.

Heat-induced female biased sex ratio during development is not mitigated after prolonged thermal selection

BackgroundThe negative impacts of climate change on biodiversity are consistently increasing. Developmental stages are particularly sensitive in many ectotherms. Moreover, sex-specific differences in how organisms cope with thermal stress can produce biased sex ratios upon emergence, with potentially major impacts on population persistence. This is an issue that needs investigation, particularly testing whether thermal selection can alleviate sex ratio distortions in the long-term is a critical but neglected issue. Here, we report an experiment analyzing the sex ratio patterns at different developmental temperatures in Drosophila subobscura populations subjected to long-term experimental evolution (~ 30 generations) under a warming environment.ResultsWe show that exposure to high developmental temperatures consistently promotes sex ratio imbalance upon emergence, with a higher number of female than male offspring. Furthermore, we found that thermal selection resulting from evolution in a warming environment did not alleviate such sex ratio distortions generated by heat stress.ConclusionsWe demonstrate that heat stress during development can lead to clear sex ratio deviations upon emergence likely because of differential survival between sexes. In face of these findings, it is likely that sex ratio deviations of this sort occur in natural populations when facing environmental perturbation. The inability of many insects to avoid thermal shifts during their (more) sessile developmental stages makes this finding particularly troublesome for population subsistence in face of climate warming events.

Men. Male-biased sex ratios and masculinity norms: evidence from Australia's colonial past.

We document the historical roots and contemporary consequences of masculinity norms-beliefs about the proper conduct of men. We exploit a natural experiment in which convict transportation in the and centuries created a variegated spatial pattern of sex ratios across Australia. We show that in areas with heavily male-biased convict populations, relatively more men volunteered for World War I about a century later. Even at present these areas remain characterized by more violence, higher rates of male suicide and other forms of preventable male mortality, and more male-stereotypical occupational segregation. Moreover, in these historically male-biased areas, more Australians recently voted against same-sex marriage and boys-but not girls-are more likely to be bullied in school. We interpret these results as manifestations of masculinity norms that emerged due to intense local male-male competition. Once established, masculinity norms persisted over time through family socialization as well as peer socialization in schools. The online version contains supplementary material available at 10.1007/s10887-023-09223-x.

Masai giraffe population change over 40 years in Arusha National Park

AbstractA population of Masai giraffes (Giraffa camelopardalis tippelskirchi) occurs in Arusha National Park (ANP), which is not part of the regular Tanzanian national wildlife monitoring scheme. Urban development of Arusha city and agricultural expansion have contributed to the increasing isolation of ANP from other protected areas in northern Tanzania. The only published data on the Masai giraffe population of ANP were individual‐based data collected in 1979 and 1980. Here, we used individual‐based data from 2021 to 2022 to provide an update on the current population size, population sex and age structure, movements and genetic connectivity of giraffes in ANP. We documented a 49% population decline and changes in the age distribution, adult sex ratio, reproductive rate and movement patterns relative to the previous study. Mitochondrial DNA analysis revealed genetic connectivity between ANP and other populations east of the Gregory Rift Escarpments in northern Tanzania and south‐eastern Kenya, evidence that Masai giraffe once moved widely across the landscape.

Facultative and persistent offspring sex-ratio bias in relation to the social environment in cooperatively breeding red-winged fairy-wrens (Malurus elegans)

Females should facultatively bias offspring sex ratio when fitness returns vary among sexes. In cooperative breeders, where individuals help raise others’ young, overproducing the philopatric sex will be adaptive when helpers are absent, whereas overproducing the dispersive sex may be adaptive to reduce intrasexual competition. Thus, fitness returns are expected to vary with the social environment. However, any offspring sex-ratio biases may also result from consistent among-female differences (e.g. quality) and/or environmental variables (e.g. food availability). Yet, few studies have disentangled facultative from persistent biases. We investigated offspring sex-ratio biases in relation to the social environment in cooperatively breeding red-winged fairy-wrens (Malurus elegans). Repeated observations of the same females over nine years allowed for disentanglement of facultative from persistent biases. Females without help did not overproduce daughters, despite female helpers being associated with higher fledgling survival (resource enhancement hypothesis). Instead, females without helpers facultatively overproduced sons —the slower dispersing sex— thereby ensuring long-term helper availability. Furthermore, offspring sex ratio was not biased towards the rarer sex of helpers present in the group or population (resource competition hypothesis). However, females with sex-biased helping produced similarly skewed offspring sex ratios. This among-female association may not be surprising, because helpers are previous seasons’ offspring. Thus, in addition to facultative responses to prevailing social conditions, we found evidence for persistent biases among females. This could potentially explain previous evidence for resource competition/enhancement that have typically been interpreted as facultative responses, highlighting the need for a within-female approach to better understand the adaptiveness of sex-ratio biases.Significance statementUnder certain conditions, females may benefit from producing a biased offspring sex ratio, but evidence for such effects in vertebrates is weak and inconsistent. Here, using observations of the same females under different social conditions, we show that cooperatively breeding red-winged fairy-wrens facultatively biased offspring sex ratio towards sons when living in pairs, thereby ensuring the availability of a workforce to assist in raising future offspring. However, biased offspring sex ratio patterns may also be the result of consistent differences among females. Indeed, we also found evidence for such patterns and suggest that this could be an explanation for previous findings which are often interpreted as facultative responses.

Correlation between caste-based female literacy and child sex ratio in Alipurduar district of West Bengal

The present paper examines the correlation between the caste-based female literacy rate and child sex ratio in the Alipurduar District of West Bengal in 2011. The study is secondary data based which is collected from the Census of India. The study aims to analyze the spatial pattern of female literacy rate and child sex ratio and to find out the correlation between the caste-based female literacy rate and child sex ratio in Alipurduar District. Pearson’s correlation method is used to identify the correlation between female literacy rate and child sex ratio. The result of the study reveals that there is a wide disparity in the spatial distribution of caste-based female literacy rate and child sex ratio in the Alipurduar district. The study shows that the correlation between the caste-based female literacy rate and the child sex ratio is not equal. Correlation is positive in the case of General Caste but negative for both the Scheduled Caste and Scheduled Tribe in Alipurduar District. The study also highlights that the correlation between the Scheduled Caste female literacy rate and child sex ratio is significant at the 95 percent level.

Gendered mortality of children and adolescents in nineteenth-century Denmark. Exploring patterns of sex ratios and mortality rates

ABSTRACT The relationship between gender and mortality in nineteenth-century Europe has been highly debated. In particular, historians disagree about the manner and degree to which gender discrimination affected the mortality risk of the female population. This article contributes by examining the evidence of gendered mortality differences among children and adolescents in nineteenth-century Denmark. It makes use of both child sex ratios and mortality rates to explore the prevalence of excess female mortality. We show that the female mortality rate in Denmark was higher than that of males starting from around age four and lasting until adulthood, for the majority of the nineteenth century. This mortality gap, while initially narrow, was systematic and most pronounced in rural areas and during late adolescence. The gap was produced by a faster mortality decline among males. This pattern is clear both in time, as the gap widened during the nineteenth century, and during the life course, as the male mortality rate declined faster and reached lower levels during late childhood and early adolescence. While it is possible that various forms of gender discrimination slowed the mortality decline of females, the aggregated nature of the data limits our interpretation. However, by comparing the two mortality measures employed, we argue that in a low child-mortality setting such as Denmark, sex ratios are not always sensitive enough to measure excess female mortality in childhood. Further, since sex ratios primarily excel at measuring ‘hidden’ or unregistered mortality, they may be a suboptimal measure of mortality differences in the presence of a thorough and reliable vital registration system.

Gender regimes, reproductive strategies and child sex preferences: A comparative study of villages in Jammu and Leh

ABSTRACT Much of the literature on sex ratio imbalances in India has focused on the North–South divide or exclusively on the North-western states of India. In this paper, we draw on ethnographic research on the erstwhile state of Jammu and Kashmir, where the child sex ratio (0–6 years) plummeted in the 2011 census. We study two villages in the Hindu dominated district of Jammu and two in largely Buddhist Leh (in Ladakh) to understand how the gender preference for children is shaped in this culturally heterogeneous state. Our findings reiterate the importance of context in understanding sex ratio patterns and gender preferences for children, especially in the wake of declining fertility, which in some regions has led to intensified discrimination against girl children. We examine features such as the organization of kinship and marriage structures that entail diverse forms of post-marital residence, old-age support, workforce participation, household division of labor and political participation in the four villages. By engaging in detailed comparison, we propose that when underlying reasons for the devaluation of women in general, and daughters in particular, are absent (as in case of the Leh villages), the availability of sex-selective technologies does not have an adverse effect on demographic outcomes.

Conditions of sex ratio and growth patterns of craft (Portunus pelagicus) in the waters of Kawal village, Bintan Regency, Riau Island Province

Business Crab (Portunus pelagicus) Kawal Village waters are waters located in the Gunung Kijang area, Bintan Regency, Riau Islands Province. High market demand for crab fishery commodities that triggers excessive exploitation so that it can have an impact on the sustainability of crab resources. This study aims to determine the condition of the sex ratio and the pattern of crab growth in the waters of Kawal Village, Bintan Regency. The method used in this study is a survey method. The sampling technique was carried out using a random census, in which the researcher immediately went down to the field to take a sample of 176 crabs. The results showed a good sex ratio for female crabs at 52% and male crabs at 48%, which has calculated the Chi-square test which between females and males has a balanced ratio, which results in: X2 count of 33, 2 while X table is 74,975 which if X2 count < X table: male and female sex ratio is balanced. The growth pattern of both female and male crabs in the waters of Kawal Village, Bintan Regency has a negative allometric character where the growth pattern of carapace width is greater than weight growth.

Spatial and temporal patterns in the sex ratio of American lobsters (Homarus americanus) in southwestern Nova Scotia, Canada

An approximate 1:1 sex ratio of American lobsters can be skewed due to environmental factors or fisheries management. Substantial skewness can impact mating behaviour and lower reproduction which could have far-reaching ecological and economic consequences. The aim was to investigate the sex ratio patterns of lobsters in two lobster fishing areas (LFAs) in southwestern Nova Scotia, Canada and identify factors associated with skewed sex ratios. This study analyzed biological data from more than 270,000 lobsters sampled over ten years (2010–2019) by the Fishermen and Scientists Research Society. A mixed effect logistic regression model evaluated the effect of spatial, temporal and environmental factors as well as size on the sex ratio of lobsters. There were significant temporal patterns in sex ratios that differed by LFA. After the effects of sampling month, year and LFA were accounted for, lower bottom temperature and deeper water depth were associated with a higher prevalence of females, especially in larger lobsters. We present the first long term analyses of sex ratio patterns in H. americanus in Atlantic Canada’s most commercially important region for this species and provide evidence that these patterns are influenced by environmental factors and fisheries. In view of future climate change scenarios, monitoring the population dynamics of this iconic fishery species is crucial to ensure sustainable fisheries and healthy lobster stocks.

Linked supergenes underlie split sex ratio and social organization in an ant

Sexually reproducing organisms usually invest equally in male and female offspring. Deviations from this pattern have led researchers to new discoveries in the study of parent-offspring conflict, genomic conflict, and cooperative breeding. Some social insect species exhibit the unusual population-level pattern of split sex ratio, wherein some colonies specialize in the production of future queens and others specialize in the production of males. Theoretical work predicted that worker control of sex ratio and variation in relatedness asymmetry among colonies would cause each colony to specialize in the production of one sex. While some empirical tests supported theoretical predictions, others deviated from them, leaving many questions about how split sex ratio emerges. One factor yet to be investigated is whether colony sex ratio may be influenced by the genotypes of queens or workers. Here, we sequence the genomes of 138 Formica glacialis workers from 34 male-producing and 34 gyne-producing colonies to determine whether split sex ratio is under genetic control. We identify a supergene spanning 5.5 Mbp that is closely associated with sex allocation in this system. Strikingly, this supergene is adjacent to another supergene spanning 5 Mbp that is associated with variation in colony queen number. We identify a similar pattern in a second related species, Formica podzolica. The discovery that split sex ratio is determined, at least in part, by a supergene in two species opens future research on the evolutionary drivers of split sex ratio.

Animal husbandry between the Roman times and the High Middle Ages in central Europe: a biometrical analysis of cattle, sheep and pig

This paper presents a meta-analysis of biometrical data of cattle (Bos taurus), sheep (Ovis aries), and pig (Sus domesticus), with a diachronic, long-term approach (first–twelfth centuries AD) and at a large regional scale (Switzerland and adjacent areas of France), with the aim of looking at changes in animal husbandry during the transition between Roman times and the Early Middle Ages. With this in mind, a comprehensive biometrical analysis is carried out, on the basis of the log-ratio technique (or logarithmic size index — LSI). The results show an increase of the size of domesticates during the Late Roman period, as well as a long period of size decrease in the subsequent centuries. The possible reasons behind this size decrease are discussed, focusing on three factors: a genetic change, less direct control over feeding and breeding, and changing patterns of herd sex ratios. We argue that these changes should be seen as an efficient adaptation of animal husbandry strategies to broader social, economic, and political transformations.

Blow flies, synanthropy and sex ratio: Are the deviations in the sex proportion linked to human transformation of landscapes?

In most species, several factors like time of emergence, age at maturation, reproductive life span, survival of males and females, mating behavior, differential resource use, and migration patterns may affect the adult sex ratio. Anthropogenic landscape transformation is known to change diversity, favoring colonization by exotic species but other populational parameters, such as the sex ratio, have not been assessed. The aim of the present study was to describe the sex-ratio patterns of adult necrophagous blow flies captured using carrion-baited traps along habitats representing different levels of human impact. We describe the sex bias for four species: the exotic Chrysomya albiceps, Chrysomya megacephala, Chrysomya putoria, and the native Cochliomyia macellaria. Three types of habitats were selected: highly anthropized (urbanized), moderately anthropized (rural), and native forest (natural) within a humid subtropical ecoregion in Northeastern Argentina. We found an overall trend to female bias among the four species when considering the total number of each sex. However, our study showed a changing sex-ratio pattern along the gradient of human influence. Our results indicate that a higher likelihood of trapping more males in unsuitable habitats seems to be widespread among blow flies. Urban exploiters, such as Ch. megacephala and Ch. putoria, locally shifted their trends, becoming male-biased in natural habitats. The opposite trend was detected in the urban avoider Co. macellaria (which shifted to male-biased in urban habitats). The exception was Ch. albiceps, whose sex proportion did not shift to a male-biased sex ratio. The results of this study highlight the changing sex-ratio patterns displayed by Calliphoridae in response to different conditions along a human-influence gradient. The biological traits and underlying mechanisms promoting the intraspecific changes of the sex ratio are discussed.

Male-biased effective sex ratio across populations of the threatened Zamia boliviana (Zamiaceae)

Populations of dioecious plants commonly exhibit dissimilarities to the equilibrium expectation of a 1:1 sex ratio. Differential expenditure for reproduction between genders is cited as the primary mechanism responsible for a male-biased sex ratio, with increased effects on long-living species, but these mechanisms are still poorly understood. We explore the sex ratio in the endemic gymnosperm Zamia boliviana (Zamiaceae) populations from the Brazilian savanna (the Cerrado). We aim to investigate what the Z. boliviana sex ratio is, and whether population density and ecological correlates lead to variation in the sex proportion among Cerrado habitats. The study was conducted on ten in situ populations of Z. boliviana at sexual maturity (tertiary sex ratio). We estimated the populations’ sex ratio and performed a redundancy analysis to assess the relationship between biotic traits, such as sex ratio, and associated environmental features. Soil texture classes were used to classify the cycad habitats and were expressed in a ternary phase diagram. The results show a significant male-biased sex ratio in seven of the ten populations surveyed. Environmental factors did not explain the redundancy in the reproductive characteristics. However, the cycad occurs in different habitats in their endemic zone. Our study provides new biological data for Z. boliviana, suggesting that the differential reproductive expenditure of sexes in reproduction is governing the mechanisms of sex ratio variation, compared to local environmental factors in this cycad. The pattern of effective sex ratio found here improves our understanding of mechanisms causing biased sex ratios in cycads and other dioecious species from tropical ecosystems.

Plasticity in life features, parasitism and super-parasitism behavior of Bracon hebetor, an important natural enemy of Galleria mellonella and other lepidopteran host species.

The wasp, Bracon hebetor Say, is an important potential biocontrol agent of a wide range of lepidopteran insect species. The current study was subjected to compare these ectoparasitoid fitness traits on different host species belonging to the order Lepidoptera. Moreover, we determine the population dynamic with different host densities, sex ratio patterns, super-parasitism, longevity, paralysis success, and reproductive potential under laboratory conditions. Our results revealed that oviposition increased with an increase in host density, while the adult emergence and egg hatching were decreased due to the super-parasitism on host larvae. A higher male and female-biased population were observed when virgin and mated females offered fresh hosts. Adults' longevity was recorded more in females than males when kept only with bee honey + royal jelly + host larvae. The mean duration of egg-adult development was recorded higher on Galleria mellonella and lowest on Busseola fusca. The parasitization rate, super-parasitism, and cumulative fecundity of mated and virgin female wasps with different host species were observed higher on specific host Galleria mellonella while it was lower on Phthorimaea operculella. Furthermore, the parasitoids having mating experience preferred fresh, while the parasitoids' lack of mating experiences preferred paralyzed host under olfactometer test. Besides, this research has produced novel facts on the biology of parasitic wasp, B. hebetor that may guide the advancement of sustainable biological control programs to control lepidopteran pests.

Length-weight relationship (LWR) of mud crabs (Scylla sp.) in mangrove waters Peukan Bada Aceh Besar as the basic for waters resources development

Mud crab (Scylla sp.) is one of the aquatic resources that has high economic value so that the information on length-weight relationships is important for sustainable fisheries management. The objectives of this study were to determine the abundance of mud crab (Scylla sp.), the sex ratio of mud crab (Scylla sp.) and to analyze the length-weight relationship of mud crabs (Scylla sp.). This study was conducted in April 2019. Sampling of mud crabs (Scylla sp.) was carried out by using a bubu crab trap with the random sampling method. The bubu size is in length 47 cm, width 31 cm and height 19 cm. The sampling at ach station was repeated three times during low tide conditions. Sampling location was determined by using the stratified random sampling method. The results of the analysis showed that sampled number of mud crabs (Scylla sp.) in the mangrove waters of Peukan Bada were 90 individu, consisting of 50 ind female mud crabs and 40 ind male mud crabs. Therefore, sex-ratio in mud crabs (Scylla sp.) shows that the sex ratio between male and female individuals is still in a balanced state. The growth pattern were negative allometric (b<3), which means that the growth pattern of carapace length is faster than the body weight of mud crabs. The results also showed that the correlation coefficient (r) values for male and female mud crabs were 0.89 and 0.94, respectively. This indicates a close relationship between length and weight of mud crabs. Environmental parameter factors such as salinity and temperature greatly affect the growth pattern of mud crabs and sex ratio in the mangrove waters Peukan Bada, Aceh Besar.

Alewife and Blueback Herring Captured by Intertidal Weirs of the Inner Bay of Fundy, Canada, Display Seasonal Demographics that Suggest Multiple Migrating Stocks

AbstractLittle information is available concerning the seasonal demographics of marine migrating Alewife Alosa pseudoharengus and Blueback Herring A. aestivalis, reported in commercial fisheries as “gaspereau” in Canada and “river herring” in the USA. Once adults and age‐0 juveniles depart from coastal spawning rivers, they migrate along the North American Atlantic coast and are difficult to access for scientific analysis. During June–October 1985, a total of 3,785 Alewife and 2,343 Blueback Herring were examined for length, sex, and gonadal stage from commercial intertidal fishing weirs in Minas Basin and Cobequid Bay, Bay of Fundy, Nova Scotia. Of these, 999 adults were subsampled for total weight and body cavity fat deposits. Both species first appeared in the weirs during June, when Blueback Herring generally dominated catches. By July, catches were evenly divided between the two species, and Alewife dominated after mid‐August. Most adults were mature, and there was no discernable sex ratio pattern during the sampling period. Sampled fish exhibited abrupt changes in length, gonadal stage, condition factor, and abdominal wall and visceral mesentery fat deposits in relation to season (week), moon phase, and time of low tide. Sudden shifts in average lengths and fat deposits suggested that migrating Alewife were from different stocks. For Blueback Herring, the condition and status of fat deposits during June suggested that they were probably long‐distance adult migrators. Blueback Herring in Cobequid Bay weirs during July were probably from local stocks. Results from a total of 12,422 tagged adults that were released in Minas Basin and Cobequid Bay during 1985 supported these findings. We propose that shifts in condition and fat deposits can be used to estimate migration distance, discriminating among local, regional, and long‐distance movements.