Mean Size Of Females Research Articles

Age structure and body size of two Tibetan toad (Bufo tibetanus) populations from different elevations in China.

Understanding how age and body size vary across elevations can provide insights into the evolution of life-history traits in animals. In the present study, we compared the demographic (using skeletochronology) and morphological traits of the Tibetan toad (Bufo tibetanus) between two populations from different elevational habitats (2650 vs. 3930 m). We found that (1) the mean age and body size of females were significantly greater than those of males in both populations; (2) both sexes of toads from the higher elevation tended to be significantly older in age and larger in body size; (3) there was a significant positive relationship between age and body size within each sex of the toad at both elevations; and (4) growth rates varied between the two populations, with the higher rate observed in the lower-elevation population. Our results suggested that factors other than age, such as elevation-associated temperature, influence the observed differences in body size between the two populations. Future research at a broader range of elevations should focus on these factors and evaluate their influence on animal growth patterns.

Variations in age structure and growth in congeners Lacerta viridis and Lacerta media.

Determining the age of any species allows it to be analyzed from the ontogenetic, demographic, and ecological perspectives. In the present study, we tested the hypothesis that the age structure of congener species (Lacerta media and Lacerta viridis) with the same ecological niche may vary in different areas. In this context, we applied skeletochronology method to reveal various demographic parameters, such as age structure, longevity, age at sexual maturity, growth rate, survival rate, adult life expectancy, and the relationship between age and body size in the green lizard, L. viridis, and the medium lizard, L. media. In L. media and L. viridis, the maximum lifespan was 10 and 8 years, respectively. The mean age and body size of females were significantly greater than those of males in L. media. However, in the examined L. viridis population, no appreciable variation in mean age or body size was found to exist between the sexes. It was estimated that the green lizards reach maturity at the age of 2 or 3 years. However, the L. media reached sexual maturity approximately 1 year later than the congener. The body size markedly increased with age in males for both studied populations. However, in females, body size positively increased with age only in L. media. The approach of skeletochronology that we utilized in this study to assess age structure makes it simple to gather a variety of time-dependent ecological data for such ectothermic species.

Long-term changes in adult size of green turtles at Aldabra Atoll and implications for clutch size, sexual dimorphism and growth rates

Around the world, declines in the mean size of nesting sea turtles have been reported with concerns of a concomitant decrease in the reproductive output of populations. Here, we explore this possibility using long-term observations of green turtles (Chelonia mydas) at Aldabra Atoll, Seychelles. Based on > 4500 individual measurements over 21 years (1996–2016), we found the curved carapace length of nesting females declined by about 0.64 cm per decade, from 111.43 to 110.08 cm. For 391 individuals that were measured more than once with measurement interval of 2.8–19 years apart, the mean growth rate was 0.14 cm year−1. Comparisons between the size of adult females and males were based on 23 and 14 weight measurements, 107 and 33 carapace length measurements and 103 and 33 carapace width measurements, respectively, taken during 1981–1983. Adult females were larger than males, with the sexual dimorphism index, i.e. the ratio of size of the larger sex to the smaller, being 1.09 and 1.10 for carapace length and width, respectively, and 1.25 for weight. Smaller females tended to lay fewer eggs per clutch but the decrease in female mean size was accompanied by increases in numbers of turtles nesting annually, such that the estimated total numbers of eggs per year increased from 1.3 million to 2.0 million between 1996 and 2016. Therefore, a decrease in mean size of nesting females has not compromised egg production for this population.

Multiple paternity in the unisexual, haploid, leafy liverwort Porella platyphylloidea

We used isozyme markers to obtain an estimate of multiple paternity (mating of females with multiple males) in the unisexual, haploid leafy liverwort Porella platyphylloidea. From a sample of 119 plants, 15 (12.6%) were non-sex-expressing, 16 (13.4%) were females without sporophytes, 38 (31.9%) were males, and 50 (42.0%) were females bearing sporophytes. Thus, 87.4% of all plants expressed sex, and 73.5% of females bore sporophytes. The overall observed sex ratio was female-biased at 1.74:1. We extracted a total of 121 sporophytes from the 50 fertile females. Using the strict criterion that only female plants bearing two or more sporophytes with different multilocus genotypes represent cases of multiple paternity, our overall estimate is 56.8% (46 out of 81). Spearman rank-order correlation coefficients revealed that plants growing lower on trees were significantly larger than those higher on the tree and that female plants were significantly larger than male plants. Multivariate analysis showed, however, that the primary determinant underlying these correlations was the larger mean size of females.

Long‐term trends in marine turtle size at maturity at an important Atlantic rookery

AbstractFor species reaching maturity at a range of ages or sizes, factors that influence juvenile growth and size at maturity may have lasting impacts on overall fitness. Assessing when animals reach maturity is especially challenging for species which are difficult to follow through time as a result of highly migratory behavior, long life spans, or both. We examined nesting female size in a reproductive assemblage of green turtles (Chelonia mydas) and loggerheads (Caretta caretta) on the east coast of Florida, USA. We used a long‐term dataset from 1982 to 2019 to estimate a minimum size at maturity interval on the basis of two standard deviations below mean female size for each species. The minimum size intervals for green turtles (81.4–89.3 cm) and loggerheads (68.1–79.1 cm) were lower than most previous estimates in the literature, many of which were simply the smallest individual ever observed. There was a significant decrease in the upper bound of the minimum size interval over the study period for both green turtles (1.6 cm) and loggerheads (4.1 cm). These shifts in size at maturity may be the result of changes in population demographics, habitat quality, and behavioral reactions to these changes. The development and periodic reassessment of robust estimators of maturity are an important part of programs centered around the monitoring and conservation of vulnerable wildlife populations.

Do hydroelectric dams affect the abundance and population structure of freshwater shrimps?

Freshwater shrimps play an important role in many ecological processes since they are epibenthic detritivores but also prey on other invertebrates and are predated by fishes. The knowledge about their biology allow the development of management strategies to improve the use of natural resources by avoiding overfishing and enhancing productivity. Here we evaluated the population structure of the shrimp Macrobrachium amazonicum in the river Rio Grande, upstream of the Água Vermelha hydroelectric dam. They were captured monthly from October 2017 until March 2018, in six sites along the river. The first site was ∿1000 m distant from the dam and the sixth was ∿4000 m distant. A sac-like sieve and traps were used to capture the shrimps. The sieve was dragged three times for 180o. The traps were left by the river margins for six hours. In the laboratory, the shrimps were sexed and measured (carapace length; CL). In total, 6455 individuals were captured: 4499 females (294 breeding), 1445 males, and 217 juveniles. Female mean size was 7.50 ± 3.47 mm, male mean size was 7.44 ± 2.40 mm, and juvenile mean size was 3.24 ± 1.10 mm. The smallest individual was found in site III and it was a juvenile of 1.08 mm. The largest had 20 mm and was found in site II. The smallest breeding female had 3.8 mm CL. The largest individuals were more abundant in the sites near the dam, whereas the smallest were more abundant in the farthest sites. The highest abundance was seen in sites III and IV, and the lowest, in site VI. Unlike males and juveniles, females (both breeding and non-breeding) were more abundant (Anova, p < 0.01) near the dam. By knowing the population structure of M. amazonicum it is possible to understand how they are being affected by the environmental changes caused by the hydroelectric dam

Reproductive biology of the shrimp Palaemon northropi (Rankin, 1898) (Caridea: Palaemonidae) from an estuary in the Brazilian northeastern

The objective of this study was to evaluate aspects of the reproductive biology of Palaemon northropi, a shrimp of the northeastern Brazilian estuarine region. The specimens were sampled between July and November 2017, with a hand net, and were identified to species level and sexed. We measured the carapace length (CL) of males and females and the second pleura length (PL) of females. A total of 85 individuals were collected, including 36 males and 49 females (24 non-ovigerous and 25 ovigerous). The sex ratio was 0.42, with a non-significant departure from the 1:1 ratio. Mean sizes (±SD) of males and females were 3.41±0.54 and 4.98±1.33 mm CL, respectively. The mean size of the PL (±SD) of females was 2.67±1.03 mm CL. Mean fecundity was 255±57.84 embryos. The CL was positively associated with fecundity, but the fecundity did not vary between embryo developmental stages. Palaemon northropi shows sexual dimorphism, with females being larger than males. The results indicate that the embryonic development of P. northropi occurs normally, even in an estuarine region, such as that of present study, since there was no significant loss of embryos during development. This study contributes to knowledge of the reproductive biology of P. northropi and help in our understanding of the ecological relevance of these shrimps in estuarine environments.

Abundance and population structure of Plesionika narval (Fabricius, 1787) in the Northeastern Atlantic

Analysis of abundance and population structure of Plesionika narval was performed on data concerning 5,255 specimens obtained from 62 fishing sets carried out off the Madeira archipelago (Northeastern Atlantic) between 2004 and 2008 in a depth range from 101 to 350 m. Abundance ranged from 0.01 to 19.74 specimens-per-trap and significant differences were found between seasons, probably as a result of an increment of population in the spring during the recruitment season. The analysis of size distribution revealed that the carapace length (CL) ranged from 2.45 to 28.61 mm and that mean female size consistently exceeded that of males. Differences in mean CL were statistically significant between depth strata and seasons. Of the specimens sampled, 57.00% were males, 41.88% females and 1.42% undetermined. Sex ratio also differed significantly between seasons according to depth strata, consolidating the hypothesis of the existence of seasonal migrations related with the reproductive cycle of this species. Ovigerous females showed larger sizes and occurred all year around and remain in shallow waters in winter, summer and autumn and move to deeper waters in spring. The highest frequency of ovigerous females was recorded in summer, between 151 and 200 m deep supporting the hypothesis that spawning of this species occurs in shallow waters, especially in late summer.

Reproductive biology of Plesionika narval in the SE Aegean Sea (Eastern Mediterranean)

Plesionika narval is a widespread species of the Pandalidae family, of particular high economic importance for small-scale shrimp trap fisheries in the Dodecanese Islands (SE Aegean Sea). Understanding its biology and reproduction are crucial for stock management. Reproductive biology aspects were studied through data collected during monthly experimental surveys with baited shrimps traps from November 2014 to October 2015 at a depth range of 10 - 150m. A total of 3436 individuals within the size range of 6.46 to 20.20 mm carapace length (CL) was analyzed. Overall, mean female size was significantly higher than mean male size, while the mean size of ovigerous females was higher than that of non-ovigerous females. Mean carapace length of ovigerous and non-ovigerous females was significantly correlated to depth. Ovigerous females were observed throughout the study period; however, monthly proportions revealed April to October as the main reproductive period of the species in the area. The sex ratio showed a clear predominance of females in the shallow depth zone (10-25 m) and was found to be affected by sampling area and depth zone. Immature females were found from November to March. Mature females were found all year round, exhibiting higher percentages in March, June, July and September, coinciding with the main reproductive period. P. narval seemed to spawn more than one time within the annual reproductive cycle. Gonadosomatic index obtained its highest mean values in May, June and September, thus revealing the main reproductive period. Size at first maturity for females was estimated at CL50=11.7 mm.

Effects of maternal influences and timing of spawning on intraspecific variations in larval qualities of the Kuruma prawn Marsupenaeus japonicus

Decreases in intraspecific variations in offspring qualities resulting from reductions in female body size in harvested populations can reduce the ability of these species to adapt to variations in environmental conditions. This, in turn, may result in greater fluctuations in recruitment of resources. In species in which offspring quality differs by female parent size, preserving differences and preventing limitations in female size among populations would be important. The effects of maternal factors on intraspecific variations in larval quality of the Kuruma prawn (Marsupenaeus japonicus) were analyzed by determining the relationships between larval variability (body size and resistance to starvation) and maternal variability (maternal body size, spawning timing, and maternal body condition) in the laboratory from June to October 2015. In addition, temporal variations in parental body size of fished M. japonicus stock were examined by field investigation for ten years between 1996 and 2010 in Bungo-suido Channel, Japan. Body size and starvation resistance of hatched larvae varied by spawning timing (spawning date) and corresponded with seasonal availability of food for larvae in the field. Larger females produced larger larvae with stronger starvation resistance. The mean size of harvested female prawns has decreased significantly over time. Stocks of M. japonicus with reduced mean female size would show reductions in intraspecific variations in quality and quantity of larvae at the population level, resulting from observed maternal influences and size-dependent female reproductive potential. If fishing activity reduces body size, marine reserves can be used as a possible management option.

Consistent patterns of male mate preference in the laboratory and field

Mate preference by males is a widely observed phenomenon; however, it is not well understood how these preferences are expressed in wild populations. Most studies that describe the expression of male mate preference in the wild tend to observe assortative mating, where higher quality males express a strong preference for high quality females while low quality males express either no preference or a preference for low quality females. We examined male mate preference in Bolitotherus cornutus, the forked fungus beetle, a system that exhibits male–male combat and protracted male courtship. We conducted no-choice trials in the laboratory and monitored male courtship in a wild population. In the laboratory, we found a strong preference for larger, more fecund females across all sizes of males. Results from the field were similar to those in the lab; larger females were courted more often, and there was no relationship between the size of a male and the mean size of females he courted (i.e., no assortative mating). This study documents an unusual pattern of expression of male mate preference in the wild and suggests that mate preference by males may be underappreciated in species with intense male–male competition and non-assortative mating. While males of many species express a preference for high-quality females, their preferences can change in complex social situations such as those in wild populations, often resulting in pairing for quality. However, recent mathematical theory suggests that male preference could evolve in a variety of social contexts. We studied the mate preferences of male forked fungus beetles in the laboratory and a wild population. In the lab, males of all sizes preferred larger females. In the complex social environment of a wild population, males still preferred larger females even though there was a strong male-male competition. There was no pairing for quality as often observed in other species. These results suggest that male mate preferences may evolve in a variety of systems not just those with flexible preferences and pairing for quality.

Sexual traits plasticity of the potentially invasive limpet Bostrycapulus odites (Gastropoda: Calyptraeidae) within its natural distribution in South America

AbstractThe slipper limpet Bostrycapulus odites has recently been reported as an introduced species on the Spanish Mediterranean coast. Another species in the family Calyptraeidae, Crepidula fornicata, is a problematic invasive species in the Northeast Atlantic, which makes the closely related Bostrycapulus introduction a matter of concern. Information on the biology of B. odites in its natural environment can facilitate predictions on where the species could find favourable conditions for settlement and expansion. Size and sex were recorded for individuals in four populations over 2600 km of the Southwestern Atlantic shoreline, in Argentina and Brazil, covering the whole native latitudinal range of this widely distributed species. Animals were collected by hand in the intertidal or by SCUBA in subtidal locations; specimens were examined to determine shell length, sex, and the presence and number of brooded egg capsules in females. Mean shell length for the whole population did not differ significantly among populations. However, this species experiences sequential hermaphroditism (protandrism), and the size at sexual maturity (minimum male size) increased significantly with latitude. The fecundity of females at all sites increased with size, and the number of brooded egg capsules as well as the average size of capsules was larger in bigger individual females; however, mean fecundity varied among sites independent of mean female body size. This limpet species modifies its reproductive traits with local conditions, and sexual characters develop earlier in more temperate localities.

Geographic and environmental drivers of fecundity in the European lobster (Homarus gammarus)

Abstract Fecundity in the European lobster (Homarus gammarus) has been shown to exhibit extensive spatial variation across northern Europe. Previously, this has been attributed to a lack of methodological standardization among samples. Instead, we show significant correlations between fecundity and both geographical and environmental drivers. We use linear mixed-effect models to assess the contribution of latitude, longitude, and measures of sea surface temperatures on the size–fecundity relationships of 1058 ovigerous females from 11 locations in the UK, Ireland, and Norway. We include new data for 52 lobsters from Falmouth, UK, the southwest limit of existing samples. Fecundity at mean female size correlated positively with eastings and greater annual ranges in sea surface temperature, but not with mean temperature or latitude. This contradicts the established latitudinal and mean temperature dependence reported for the closely related H. americanus. We postulate that proximity to stable Atlantic currents is the most likely driver of the relationship between fecundity and longitude. Mechanisms are discussed by which egg production or retention may be influenced by temperature range rather than by mean temperature. With further validation, we propose that temperature-correlated fecundity predictions will provide a valuable tool in ensuring that management thresholds are appropriate for the reproductive characteristics of lobster populations.

She's a femme fatale: low-density larval development produces good disease vectors.

Two hypotheses for how conditions for larval mosquitoes affect vectorial capacity make opposite predictions about the relationship of adult size and frequency of infection with vector-borne pathogens. Competition among larvae produces small adult females. The competition-susceptibility hypothesis postulates that small females are more susceptible to infection and predicts frequency of infection should decrease with size. The competition-longevity hypothesis postulates that small females have lower longevity and lower probability of becoming competent to transmit the pathogen and thus predicts frequency of infection should increase with size. We tested these hypotheses for Aedes aegypti in Rio de Janeiro, Brazil, during a dengue outbreak. In the laboratory, longevity increases with size, then decreases at the largest sizes. For field-collected females, generalised linear mixed model comparisons showed that a model with a linear increase of frequency of dengue with size produced the best Akaike’s information criterion with a correction for small sample sizes (AICc). Consensus prediction of three competing models indicated that frequency of infection increases monotonically with female size, consistent with the competition-longevity hypothesis. Site frequency of infection was not significantly related to site mean size of females. Thus, our data indicate that uncrowded, low competition conditions for larvae produce the females that are most likely to be important vectors of dengue. More generally, ecological conditions, particularly crowding and intraspecific competition among larvae, are likely to affect vector-borne pathogen transmission in nature, in this case via effects on longevity of resulting adults. Heterogeneity among individual vectors in likelihood of infection is a generally important outcome of ecological conditions impacting vectors as larvae.

Climate change selects for heterozygosity in a declining fur seal population.

Global environmental change is expected to alter selection pressures in many biological systems, but the long-term molecular and life history data required to quantify changes in selection are rare. An unusual opportunity is afforded by three decades of individual-based data collected from a declining population of Antarctic fur seals in the South Atlantic. Here, climate change has reduced prey availability and caused a significant decline in seal birth weight. However, the mean age and size of females recruiting into the breeding population are increasing. We show that such females have significantly higher heterozygosity (a measure of within-individual genetic variation) than their non-recruiting siblings and their own mothers. Thus, breeding female heterozygosity has increased by 8.5% per generation over the last two decades. Nonetheless, as heterozygosity is not inherited from mothers to daughters, substantial heterozygote advantage is not transmitted from one generation to the next and the decreasing viability of homozygous individuals causes the population to decline. Our results provide compelling evidence that selection due to climate change is intensifying, with far-reaching consequences for demography as well as phenotypic and genetic variation.

A priori assessment of reintroduction strategies for a native ungulate: using HexSim to guide release site selection

Reintroduction of native species to unoccupied portions of their historical range is a common management strategy to enhance the future viability of animal populations. This approach has met with mixed success, due to unforeseen impacts caused by human or other factors. Some of these impacts could potentially be mitigated through the use of anticipatory modeling coupled with appropriate management strategies prior to release. As part of an ongoing restoration program, we evaluated a portion of the former range of the tule elk (Cervus elaphus nannodes) in the Central Valley of California for potential reintroduction of a free-ranging herd. We used a new spatially explicit population model (HexSim) to analyze four different elk release scenarios. Each scenario corresponded to a different release location, and the model was used to compare simulated elk movement and population dynamics 25 years into the future. We also used HexSim to identify likely locations of human–elk conflict. Population forecasts after the 25-year period were highest (mean female population size of 169.6 per iteration) and potentially harmful barrier interactions were lowest (mean 8.6 per iteration) at the East Bear Creek site. These results indicate the East Bear Creek site release scenario as the most likely to result in a successful elk reintroduction, producing the most elk and generating the fewest human conflicts. We found HexSim to be a useful tool for this type of reintroduction planning and believe that other reintroduction efforts could benefit from this type of anticipatory modeling.

Diet and reproductive dynamics of Trachelyopterus lucenai (Siluriformes: Auchenipteridae) in subtropical coastal lagoons in southern Brazil

This study analyzed the diet and reproductive dynamics of Trachelyopterus lucenai Bertoletti, Pezzi da Silva & Pereira, 1995, an allochthonous fish species in the subtropical coastal lagoons of the Tramandai River, Rio Grande do Sul, Brazil. The fecundity of the species is described for the first time. Specimens were captured in the interconnected lagoons Itapeva, Quadros and Malvas, on a monthly basis, from November 2008 to April 2010, with gillnets of different mesh sizes. The food items identified were assessed for abundance and frequency of occurrence. The sex ratio, reproductive period for males and females, for mature females, fecundity, were estimated. These results were analyzed with respect to seasonal variation. We captured 135 individuals, including 82 females and 53 males, especially in months with high temperatures (October 2009 to March 2010). Females were more abundant than males in all months. There was no difference between the mean size of females and males, and both sexes showed allometric growth. The feeding analysis showed a generalist-opportunist food habit; 26 items were consumed, with a predominance of autochthonous items (insects and fish). Temporal variations in diet were associated with variations in water and air temperature and rainfall in the region, but these variations did not differ between males and females. The sex ratio differed significantly from 1:1, with 1.5 females per male. The reproductive period occurred from October to March, with most activity in November and December, and showing no variation between the peaks of gonadal development of males and females. The mean fecundity of mature females was 1,536 oocytes per spawning (n = 17). The feeding habits and reproductive behavior of the species in the study site are similar to those described for where the species is native. Although clearly seasonal, the reproductive period was long, in spite of the low fecundity. These features facilitate the establishment of T. lucenai and make it a good competitor in the new environment.

Long-Term Changes in Population Dynamics of the Shrimp Palaemon longirostris in the Gironde Estuary

Spanning 20 years (1979–2007), this study is the longest time series pertaining to the resident shrimp species Palaemon longirostris in a European estuary. Data from monthly faunal surveys undertaken across the middle part of the Gironde estuary from April 1979 along with data from a statistical analysis of the commercial catches throughout the entire estuary and river were considered in order to explore their inter and intra-annual variability and long-term trends. Long-term densities series as well as environmental series (salinity, discharge, temperature and NAO) were decomposed and the effects of environmental variables were also examined using statistical models (GAMs). This revealed important spatio-temporal variability and a significant overall decrease in abundance of this species in the Gironde estuary since the beginning of the 1980s. This long-term decrease in abundance corresponded significantly to long-term decreases in both discharge and the NAO index, as well a long-term increase in temperature and salinity in the middle part of the estuary. However, models showed that environmental factors explained only a small part of the variability. The upstream shift of the population highlighted in this study, probably due to the intrusion of marine waters into the middle section of the estuary, may also have contributed to its decrease in abundance. Inter-annual variability of densities was also significantly linked with inter-annual fecundity fluctuations, and a significant decrease in both mean female size and fecundity was shown for preserved samples from 1992. Moreover, the breeding period has been temporally stretched out and began earlier in more recent years, potentially due to the increase in spring temperature.

Intraspecific Variation of Reproductive Traits in a Mediterranean Lizard: Clutch, Population, and Lineage Effects

Widely distributed terrestrial ectotherms from the southern European peninsulas show patterns of subdivision (related to isolation in temperate refugia) that allow us to test the relative importance of phylogeographic lineage, population of origin and familial effects as sources of variation for life-history traits. We collected gravid females from 15 geographically separated populations of the lacertid lizard Psammodromus algirus, a widely distributed species with well differentiated eastern and western lineages. We incubated eggs under two treatments of constant (28°C) and fluctuating (28 ± 4°C) temperature, and we examined clutch, population, and lineage effects on several traits of females, eggs, and hatchlings. Incubation time was mainly explained by differences between lineages, but it was also influenced by population and female effects. Within each lineage, incubation was shorter at cooler and wetter sites, and for a given climate it was shorter for eastern than for western populations, suggesting that countergradient variation has evolved independently in the two lineages. Female size, clutch size, and relative fecundity were primarily influenced by inter-population differences, a pattern that seemed attributable to environmental differences in productivity, because mean female size was positively correlated with a gradient of increasing precipitation and decreasing temperature. Clutch size was mainly, but not entirely, dependent on female SVL, suggesting both a proximate effect of local conditions and intrinsic differences among populations. Females from drier and warmer sites produced larger hatchlings. Mean egg mass was mainly determined by familial effects. Eggs incubated at a constant temperature hatched earlier than did their siblings incubated at fluctuating temperatures, a fact that could be explained by considering that in Mediterranean environments developmental rate might increase at a lower speed above average incubation temperature than it does decrease below it.

Sexual development, sex ratio and morphometrics of Pteria penguin (Bivalvia: Pteriidae), in north-eastern Australia

Pteria penguin were collected at Orpheus Island, north-eastern Queensland to observe sexual development, sex ratio and changes in morphometric relationships during growth. P. penguin are protandrous hermaphrodites, with all sexually mature oysters below 88.8 mm dorso-ventral height (DVH) being males. Evidence of male primary gonad development was seen in oysters with a DVH of ≥33.9 mm. Sexual maturity of males was first seen in oysters at ≥56.0 mm DVH, but was common in oysters at ≥70.0 mm DVH. Mean female size was 150.1 (±3.6) mm DVH, and mean male size was 111.3 (±2.2) mm DVH. In oysters <170 mm DVH, males outnumbered females. The female to male sex ratio in the population tended towards 1:1 with increasing size. Female to male sex ratio of oysters between 170-180 mm DVH was 1:1, and females outnumbered males in oysters 180 mm DVH. Significant linear correlations were found between anterior-posterior length of the shell (APL) and DVH (r2 = 0.97, p <0.001) and between shell thickness (ST) and DVH (r2 = 0.95, p <0.001), and a curvilinear relationship was recorded between adductor muscle weight (AW) and DVH (r2 = 0.93, p <0.001). These findings have industry applications for collection of juvenile stock, spawning induction procedures and determining optimal shell size for pearl nucleus implanting.