Yr For Females Research Articles

Crecimiento del cangrejo Callinectes danae (Decapoda: Portunidae) de la Isla de Margarita, Venezuela

Callinectes danae is a common species captured with crab traps in nearby areas of coastal lagoons in Margarita Island. Although its considerable economic importance as a fishery resource, few studies have been done on population dynamics and its fishery potential in local coastal environments to support decision making in fishery administration. We present growth pattern details of Callinectes danae to better estimate its population size and exploitation feasibility. For this, we analyzed a total of 3 623 specimens that were monthly captured in crab pots by artisanal fishermen in Las Marites lagoon, from October 2007 to September 2008. The length-weight ratio was determined, and growth parameters estimated from both length and weight curves of the von Bertalanffy model. The general sex ratio showed no significant difference between males and females (chi2 = 0.04, p > 0.05). However, values of slopes b between males and females were significantly different (t(s) = 2.75, p < 0.05), as well as intercepts a (t(s) = 2.44, p < 0.05). Thus, the length-weight ratio was determined separately: W = 7.48e(-5)*L(2.98) for males and W = 1.21e(-4)*L(2.87) for females, indicating a negative allometric growth in both sexes. Growth parameters were established as: L(infinity) =134.80mm, W(infinity) = 166.04g and k = 0.86/yr for males; L(infinity) = 122.35mm, W(infinity) = 118.45g and k = 0.63/yr for females. Lifespan was estimated at 3.05 years for males and 4.24 years for females. We concluded that Callinectes danae is a species with short lifespan and moderately rapid growth. The coefficient of variation values (CV), of the phi-prime growth performance index (Ø'), showed a different growth pattern compared to those obtained in other regions. We propose that a management strategy will be the periodical review of the minimum capture size for fishing area, after the great variability found in growth parameters.

Body Size and Age Structure of a Breeding Population of the Japanese Common Toad, Bufo Japonicus Formosus (Amphibia: Bufonidae)

Abstract: The body size and age structure of a breeding population of the Japanese common toad, Bufo japonicus formosus, was studied at Yamakitamachi in Kanagawa Prefecture for three breeding seasons from 1992 to 1994. Yearly variation in snout-vent length (SVL) was not significant, but the difference in SVL between the sexes was highly significant; the mean SVL of males and females was 125.8 and 134.2 mm, respectively. The breeding adults were aged successfully by skeletochronology using phalanges. The breeding adults were 1-8 yr old. The mean and median ages were 4.5 and 4 yr in males, and 5.2 and 5 yr in females, respectively. The males were estimated to begin to breed when one to four yr old, with a mean of 2.4 yr, while the females were estimated to breed when two to four yr old, with a mean of 2.7 yr. Age at first reproduction was significantly younger for males than females. We discuss the sexual size dimorphism of B. j. formosus in relation to the difference in age structure of the breeding popula...

Two-Year-Old Nesting Behavior and Extra-Pair Copulation in a Reintroduced Osprey Population

ABSTRACT A reintroduced population of Ospreys (Pandion haliaetus) in eight counties surrounding Minneapolis/St. Paul, MN was monitored from 1984–2005. We recorded the behavior of marked birds at 306 occupied nests. Two-yr-old Ospreys were involved in nest attempts more often than previously reported. Twelve were observed; eight of these (five males and three females) occupied nests, and the remaining four were floaters. Readily available nest sites and abundant food resources may have been factors in breeding attempts by these young Ospreys. Age at first known occupied nest averaged 4.13 yr for males (N = 38) and 3.36 yr for females (N = 11). Age at first known successful nest averaged 4.39 yr for males (N = 38) and 3.64 yr for females (N = 11). In 2003, two 2-yr-old males fledged chicks. We also observed Ospreys copulating with more than one partner in the same breeding season on 14 occasions (10.52% of nests where eggs were laid). All but one extra-pair visit was observed between 2003 and 2005, ...

LIFE-HISTORY TRAITS OF PLETHODON CINEREUS IN THE NORTHERN PARTS OF ITS RANGE: VARIATIONS IN POPULATION STRUCTURE, AGE AND GROWTH

The life history of red-backed salamanders (Plethodon cinereus) has been intensively studied in the United States, but little information exists for Canadian populations, which limits the ability to perform analyses of latitudinal trends in this species. To investigate variations in body size, age structures, longevity, and growth, we used drift fences to sample populations in four habitats (from mixed to deciduous forests) within a 12 km radius in the Mastigouche Reserve located in Quebec, Canada. During the active season of 1997, we captured, measured and sexed (except neonates) a total of 775 salamanders, and estimated the age of 330 of these specimens using skeletochronology. The population characterized by highest mean body size and/or mean age was from a mixed forest that also harbored the greatest abundance of salamanders. For all populations combined, body size (SVL) ranged from 12–46 mm for males and 12–54 mm for females, and longevity reached 8 yr in females and 9 yr in males. Adult males showed...

Demographic and Female Life History Parameters of Free-Ranging Chimpanzees at the Chimpanzee Rehabilitation Project, River Gambia National Park

We analyzed fertility and mortality records for 113 provisioned, free-ranging chimpanzees at the River Gambia National Park, The Gambia. The chimpanzees are rehabilitated orphans released by the Chimpanzee Rehabilitation Project (CRP), and their descendants born in a natural environment. Females experienced their 1st births at an average age of 14.3 yr, with average interbirth intervals of 68 mo. Despite limited provisioning, reproductive parameters in both released and 1st-generation females resembled those of wild chimpanzees and showed seasonal fluctuations. Mortality rates were low compared to those for wild chimpanzees, particularly for infants and juveniles; life expectancy at birth was 23.6 yr for females and 18 yr for males. The results have implications for our understanding of variation in reproductive parameters between captive and wild chimpanzees. We also discuss issues related to chimpanzee conservation and captive rearing.

P.3.c.045 Treatment of agitation caused by severe mental illness: data from the South London and Maudsley intensive care units trial evaluation (SLAMICUTE) study

Dual-energy X-ray absorptiometry (DXA) assessment of body fat mass is precise and highly correlated with under water weighing. In view of ethnic differences, we undertook this study to prepare normative data for body fat mass in apparently healthy adult Indians and correlate it with body mass index (BMI). This cross-sectional population-based study included 2347 subjects (male: 924; female: 1423) aged >20 yr who participated in a general health examination. They were evaluated for anthropometry and body fat mass by DXA. All subjects were categorized as overweight and obese based on standard BMI criteria. Mean age and BMI were 49.1 ± 18.2 yr and 25.0 ± 4.7 kg/m2, respectively. Mean percent total and regional fat (trunk, arm, and leg) reached maximum in the age group of 30–40 yr in males and 50–60 yr in females. Females had significantly higher total and regional fat mass compared with males. Fat mass was positively correlated with age (r = 0.224; p < 0.00001) and BMI (r = 0.668; p < 0.00001). Prevalence of overweight and obesity was seen in 2119 (46.1%) and 536 (13.8%), respectively, according to World Health Organization definition and 64.0% and 31.1%, respectively, as per Indian guidelines. Percent total body fat mass (PTBFM) of 25% in males and 30% in females corresponds to BMI of 22.0 kg/m2 with sensitivity of >80% and specificity of >70% in receiver operating characteristic curve analysis. Body fat mass in Indians is higher than that in Western populations for a given age and BMI. PTBFM of 25% in males and 30% in females corresponds to BMI of 22 kg/m2 in Indians.

Growth and population structure of the Moorish Tortoise ( Testudo graeca graeca) in Westcentral Morocco: possible effects of over-collecting for the tourist trade

We studied growth of 284 live Moorish tortoises ( Testudo graeca graeca) from the central Jbilet Mountains, the Admine Forest, and near Essaouira in westcentral Morocco in 2001. Size structures, but not age structures, differed significantly among populations. No very old tortoises were found at any site. Most populations of tortoises suffered over-collecting for the tourist trade in the past, and some collecting still continues, which probably explains the lack of older tortoises. Of tortoises remaining in the populations we studied, both males and females grew relatively quickly for 10–12 yr in all three populations, after which their growth rates deceased markedly. Females in all three populations had greater asymptotic sizes than males, and CL and log mass differed significantly between sexes by age 9 yr for the three populations, except for log mass of tortoises from Essaouira, which differed by age 6. Mean CLs and log masses were significantly greater in Admine and Essaouira tortoises than in tortoises from Jbilet. Estimated mean age at maturity varied from 5.8 to 7.6 yr for males and 7.7–10.5 yr for females. Although past over-collecting of tortoises has probably depressed population abundances and eliminated the larger, older tortoises at all three sites, the current differences in population structure and growth pattern may be the result of geographic variation in environmental conditions, suggesting different selective mechanisms for the three populations.

Growth in peak aerobic power during adolescence.

To model the growth of peak aerobic power during adolescence in both sexes followed longitudinally from 10 to 18 yr. Peak aerobic power (peak VO2) was measured annually during a maximal treadmill test with the Bruce protocol. Height and weight were measured semiannually. The Preece-Baines Model I growth function was used to fit curves to data for individuals with >/= six observations for peak aerobic power to estimate age at peak velocity (PV) for peak VO2 (age at PVPVO2), PVPVO2 (L x min(-1) x yr(-1)), and value at PVPVO2 (L x min(-1)) for each individual. Curves were successfully fitted for 83 individuals (48 males, 35 females). The model was also fitted to individual data for height and weight to estimate ages at peak height velocity (PHV) and peak weight velocity (PWV). Age at PVPVO2 was compared with ages at PHV and PWV. Pearson correlation coefficients were calculated between ages at PV and PV for peak VO2, height, and weight. Mean ages at PVPVO2 are 12.3 +/- 1.2 yr for females and 14.1 +/- 1.2 yr for males. Peak VO2 increases in both sexes throughout adolescence, with males having higher values than females at all ages. Age at PVPVO2 occurs nearly coincident with PHV and before PWV in both sexes. Correlation coefficients among ages at PHV, PWV, and PVPVO2 suggest a general maturity factor for body size and aerobic power. Growth in peak VO2 exhibits a clear growth spurt in both sexes during adolescence. The growth spurt occurs earlier in females but is of greater magnitude in males.

The influence of intensive physical exercise on bone acquisition in adolescent elite female and male artistic gymnasts.

Physical exercise enhances bone acquisition during adolescence. The aim of the study was to evaluate the influence of intensive physical exercise on bone acquisition in adolescent elite artistic gymnasts. The study included 262 athletes (93 males and 169 females, aged 13-23 yr) participating in the 24th European Championship held in Greece. Bone age compared with chronological age was delayed by 2 yr for females (n = 120) and 1 yr for males (n = 68). For both sexes, the growth chart of bone mineral density (BMD) followed a normal pattern when estimated according to bone age rather than chronological age. For females, BMD was positively correlated with bone age, chronological age, height, body weight, body mass index, body fat, lean body mass, and with age of onset of training, and negatively with duration of exercise and intensity of training (P values range from <0.05 to <0.0001). Multiple regression analysis revealed that age of onset of training was the major parameter attenuating the effect of exercise on BMD (P < 0.001). The latter was related to the stage of puberty (P < 0.05). For males, BMD was correlated positively with bone age, height, body weight, and lean body mass (P values range from <0.01 to 0.0001). Multiple regression analysis revealed that the more powerful factor influencing BMD was weight (P < 0.01). In conclusion, bone acquisition in adolescents under intensive physical training follows the normal pattern only when estimated according to bone age. The age of onset, the duration, and the intensity of exercise attenuate the bone acquisition, at least in female artistic gymnasts.

SKELETOCHRONOLOGICAL ANALYSIS OF VARIATION IN AGE STRUCTURE, BODY SIZE, AND LIFE HISTORY IN THREE SPECIES OF DESMOGNATHINE SALAMANDERS

We evaluated age structure in three species of desmognathine salamanders at Coweeta Hydrologic Laboratory, North Carolina, for comparison with the results of an earlier study of age structure in these species at a nearby locality (Wolf Creek, North Carolina). At Coweeta, both Desmognathus quadramaculatus and D. monticola attain larger adult body sizes and greater ages than their Wolf Creek counterparts. The differences appear to stem in part from greater ages at sexual maturation in both species at Coweeta versus Wolf Creek. This disparity is most pronounced in D. quadramaculatus, where the estimated ages at first reproduction are 7–8 yr in males and 9–10 yr in females. The Coweeta populations of D. quadramaculatus and D. monticola may also have higher survivorship and higher rates of post-maturational growth than those at Wolf Creek. In contrast, in the third and smallest species, D. ocoee, the Coweeta population did not differ in size and age attributes from that at Wolf Creek. We hypothesize that the m...

Life expectancy and mortality differences between migrant groups living in Amsterdam, the Netherlands

There is an apparent contradiction between the high level of morbidity and the low level of mortality observed in certain groups of migrants living in Europe. This observation should have some consequences for health policy development and the targeting of resources in a city like Amsterdam. In this paper a number of hypotheses to explain the low mortality in migrant groups are discussed. An analysis is made of mortality in Amsterdam using data from the civil registry as to mortality according to age, sex and nationality group of the deceased. Standard demographic techniques such as the standardised mortality ratio (SMR) and life table analysis were employed. Life table analysis shows that life expectancy in Amsterdam is lowest among residents of Dutch descent (73.3 yr for males and 79.1 yr for females) and highest among those of Mediterranean origin (77.6 yr for males and 86.1 yr for females). This appears to contradict previous research based on the SMR, which showed high mortality in migrant groups. To find the cause of this contradiction, the SMR and risk ratios by age are studied. The conclusion of this paper is that on the basis of life table analysis it appears that some immigrant groups living in Amsterdam have a remarkably high life expectancy. Since the SMR is sensitive to demographic differences between groups compared, questions can be raised about previous studies using the SMR. It has been suggested that the high life expectancy in migrant groups is not really caused by good health but by ‘spurious’ phenomena, such as problems in mortality registration. However, in view of the available data it seems likely that some migrant groups do in fact have high life expectancy, although the morbidity in these groups can be quite high. These findings should inform health-related policy.

Long‐term demographic fluctuations of the spur‐thighed tortoise Testudo graeca in SW Spain

We assessed the dynamics of a population of spur‐thighed tortoises, Testudo graeca. placed under long‐term protection from human interference. We estimated demographic parameters and constructed vertical life tables based on age structures for two different study periods separated by a 12‐yr interval. Average age at maturity was 6.9 yr for males and 8.5 yr for females. Clutch size varied with female size, but tended to be constant among years. Average annual female fecundity over 9 yr was 8.4 eggs and decreased significantly in years of high rainfall. Females seemed to reproduce yearly, but with a constantly low output, probably maximising both their long‐term reproductive potential and the probability of producing offspring during favourable years for hatchling survival. Adult survival was high and constant between periods. Juvenile survivorship from egg to 6 yr and recruitment into the 5 8‐yr‐old cohorts were significantly higher in the second period. Life tables indicated a predominantly negative demographic trend for the first period, with an average population increase rate of 0.977. and an overall positive tendency for the second period, with an average increase rate of 1.091. These figures suggest that the population experienced a variation that was closer to the maximum estimates for the first period, mediated mainly by an increase in juvenile recruitment. The data indicate that, besides high adult survival rates, occasional high juvenile recruitment bouts may have an important regulatory effect on the population dynamics of Testudo graeca.

THE ENERGY COST OF MODERN BALLROOM DANCING

Modern ballroom dancing is a widely performed physical activity which is starting to be considered an actual sport discipline, though few studies on the argument are reported in literature. To get further insight on the functional model of this discipline six competitive modern ballroom dancing couples performed a simulated competitive standard sequences of modern ballroom dancing (MBDseq), consisting of 5 different dances (W: waltz; T: tango; VW: viennese waltz; FT: fox trot; QS: quick step). Anthropometric and physiological characteristics of subjects were: age 19.3 ± 2.3 yr for males and 19.3 ± 2.9 yr for females, height 175.8 ± 6.6 cm for males and 162.5 ± 4.5 cm for females, weight 69.1 ± 5.8 kg for males and 52.9 ± 7.3 kg for females, VO2max 60.9 ± 6.0 mlkg−1min−1 for males and 53.7 ± 5.3 mlkg−1min−1 for females. Heart rate and oxygen uptake (VO2) were recorded along all dances by a telemetric system (Q4 b2, Cosmed, Italy). Blood lactate concentration ([La]) was measured at rest, at the and of each dance, at the and of MBDseq and along recovery period. Each dance of the MBDseq lasted 1'45ö, recovery period between dances lasted 30ö. MBDseq values are referred to the active periods only: mean VO2 resulted 45.8 ± 6.0 mlkg−1min−1 (75.7 ± 10.6% of VO2max) for males and 38.0 ± 8.5 mlkg−1min−1 (70.8 ± 13.8% of VO2max) for females; mean energy cost deriving from aerobic metabolism resulted 566.2 ± 89.5 kJ for males and 360.8 ± 77.7 kJ for females. [La] peak reached 8.5 ± 2.3 mM for males and 8.3 ± 3.9 mM for females. When single dances were analyzed separately VO2 was found to increase up to the third dance (VW), decrease in the fourth (FT) and increase again in the last one (QS), the highest VO2 being found in the third dance for males (81.3 ± 8.1% VO2max) and in the last one for female (80.1 ± 10.7% VO2max). Lactate accumulation followed the same course. A high [La] production was reported in the first dance (1.83 mM/dance), probably due to the inertia of activation of aerobic metabolism, afterward [La] production decreased up to the fourth dance (−0.86 mM/dance), and then rose again in the last dance up to a peak value (1.82 mM/dance). Therefore, in the last but one dance (FT) a low [La] production and a low VO2 were found. In conclusion the present results suggest that the energy cost of modern dancing ranges from medium to high, both for the aerobic and anaerobic metabolism along MBDseq, according to the dance performed, relying W mostly on the aerobic metabolism and QS on both aerobic and anaerobic metabolism.

A twelve year study of the incidence of childhood type 1 diabetes mellitus in the Eastern Province of Saudi Arabia.

Study of the incidence of childhood type 1 diabetes in the Eastern Province of Saudi Arabia. Analysis included all children eligible for care in our hospital who had type 1 diabetes diagnosed before their 15th birthday between 1986 and 1997. A total of 46 children (27 girls and 19 boys) were identified, with a median age at diagnosis of 10.3 yr. The overall age-adjusted incidence rate was 12.3 x 10(5)/yr; it was 9.9 x 10(5)/yr for males and 14.8 x 10(5)/yr for females. The number of patients increased significantly (relative risk of 46) over the study period (p=0.01), more significantly in females (p=0.007) and in the 10-14 year age group (p=0.01). The incidence of type 1 diabetes increased markedly over the past 12 years, mainly in females and children over 10 years of age. The data confirm the need to develop a national registry and the need for further epidemiological research.

Age and Growth of the Blacknose Shark, Carcharhinus acronotus, in the Eastern Gulf of Mexico

Age and growth of the blacknose shark, Carcharhinus acronotus, from the eastern Gulf of Mexico was estimated by counting bands on the vertebral centra from 123 individuals. Back-calculated von Bertalanffy growth functions were constructed for populations in northwest Florida and Tampa Bay, Florida. Von Bertalanffy growth function parameters for males in northwest Florida (L, = 963.1 mm FL, K = 0.59, to = -0.754 yr) were significantly different from those in Tampa Bay (L, = 801.0 mm FL, K = 0.771, to = -0.797 yr), as were those for females (L, = 1136.5 mm FL, K = 0.352, to = -1.212 yr in northwest Florida; L, = 1241.3 mm FL, K = 0.237, to = -1.536 yr in Tampa Bay). Theoretical longevity, estimated as the age at which 95% of L, is reached, varied from age 10-16 yr for females and 4.5-9.0 yr for males, depending on geographic area. The oldest sharks aged were 4.5+ yr. Centrum edge and marginal increment analyses lent support to the hypothesis that narrow dark bands are formed during winter months. Length-frequency analysis verified back-calculated size at ages 0, 1, and 2. The growth dynamics of blacknose sharks are similar to those of other relatively small, fast-growing, short-lived species of sharks.

Age, Growth, and Reproduction of the Pelagic Thresher Shark, Alopias pelagicus in the Northwestern Pacific

Age, growth, and reproduction of Alopias pelagicus are described based on 831 specimens (508 females and 323 males) collected from September 1993 to August 1995 in waters off northeastern Taiwan. Alopias pelagicus embryos are oophagous. Five developmental stages (two encapsulated and three posthatching) are recognized. The number of embryos per litter is two, and size at birth is between 158 cm and 190 cm total length (TL). The sex ratio of embryos is 1:1. Total length at maturity is 282-292 cm for females and 267276 cm for males, which corresponds to age of 8.0-9.2 yr and 7.0-8.0 yr, respectively. Gestation period could not be determined from present data because females were in various stages of pregnancy throughout the year. Based on marginal increment analysis and verified by length-frequency analysis, annuli in precaudal vertebrae form once a year and numbered up to 16 and 14 for females and males, respectively. However, extrapolating the growth rates for the largest sharks would yield maximum ages of 28.5 yr and 17.5 yr for females and males, respectively. The von Bertalanffy growth equations in PCL were estimated as Lt = 197.2(1 e-0.085(t+7.67)) for females, and L, = 182.2(1 e-0118(t+5.48)) for males.

Gender performance in a cultivated cohort of the cycad Zamia integrifolia (Zamiaceae)

A progeny of the native Florida cycad Zamia integrifolia grown from seeds planted in 1986 was monitored until 1995 to record mortality and the nature and time of expression of primary and secondary sex characters. In addition to gender‐specific cone morphologies, males and females differed in secondary sex characters such as age at first cone production, frequency of cone production, mean cone numbers in second and later coning episodes, and, in older plants, mean leaf and branch numbers. Gender differences expressed themselves at different stages in the life history: their nature and extent varied during the years following sexual maturation. By 1995, 46% of the plants in the progeny had died, most of them before producing cones. Prior to 1988 the mean leaf number of plants that died did not differ from that of survivors, but the mean leaf number of plants dying between 1988 and 1989 was 0.4 times that of the survivors during that period, suggesting reduced vigor prior to death. Mean age at first cone production was 5.8 yr for males and 6.6 yr for females. Mean dry masses of individual male cones increased between the first and second coning episodes, but not between the second and third coning episodes. Mean dry masses of the entire cone crop of individual males increased through the third coning episode due to an increase in mean cone number per episode, but mean cone number was unchanged between the third and fourth coning episodes. Mean dry mass of unpollinated female cones did not change between the first and second coning episodes; mean cone numbers did not change between the first and third coning episodes. After the first coning episode, males produced higher mean cone numbers than females. By 1995, the mean dry mass of an individual male's cone crop was greater than that of a female. Coning frequency of males was 1.7 times greater than that of unpollinated females, suggesting a gender difference in the genetic control of coning frequency. Coning frequency of females pollinated 1 or 2 yr previously was reduced compared with that of unpollinated females. Cone production did not affect subsequent leaf production by either gender. Mean leaf numbers increased in some years and not in others. Mean leaf numbers of males and females did not differ prior to cone production. After cone production mean leaf numbers of males were greater than of females. Mean age of males producing first branches was 6.3 yr, with a mean of 2.5 first branches per plant. Mean age of females producing first branches was 7.7 yr, with a mean of 2.5 first branches per plant. By 1995 the mean branch number of males was 5.7 per plant and of females was 2.7 per plant. Between 1993 and 1995 the mean branch number of males and females increased incrementally, but mean leaf numbers did not change. In early years of branching, leaf number increased with branch number; higher mean leaf numbers of males of an age class thus reflected their earlier branching. Males produced first cones earlier than females. Since branch production was associated with cone production, higher branch numbers of males in an age class reflected their earlier first cone production. In 1995 the sex ratio of known males and females in the progeny was 1:1, with a few individuals not having produced cones by that year.

Age and growth of the alfonsino Beryx splendens over the seamounts off New Caledonia

Age and growth of the alfonsino Beryx splendens from New Caledonia seamounts were determined by examination of whole and sectioned otoliths. One growth-ring (annulus) in the otoliths appears to be laid down each year. It consists of one opaque (summer, fast-growing) zone and one hyaline (winter, slowgrowing) zone. Thin-sections of otoliths revealed daily rings which allowed us to estimate that the formation of the nucleus takes ∼10 mo. The first annulus following the nucleus is incomplete. Females have a higher growth rate than males. Sexual maturity is reached at the age of 7 to 8 yr for males and 6 yr for females. Maximum age attained would be ∼20 yr for alfonsino >50 cm in fork length. the results are compared with those from the few other studies on the growth of alfonsino.

Distribution, growth and life cycle of the mesopelagic amphipod Primno abyssalis (Hyperiidea: Phrosinidae) in the southern Japan sea

The vertical distribution, growth, maturation, brood size and life cycle of the hyperiid amphipod Primno abyssalis (formerly P. macropa) were investigated using seasonal samples collected from Toyama Bay, southern Japan Sea, during the period June 1986 to September 1992. Over four different seasons of the year, P. abyssalis was most abundant in the 200 to 350 m strata at night and the 350 to 400 m strata during the day, indicating 100 to 150 m as the general distance of diel vertical movement. Some differences in vertical migrating behavior were noted among juveniles, adult males and females. Population-structure analysis revealed the occurrence of three cohorts aged 0+, 1+ and 2+ yr. Growth as body length in this species is linear with time. Estimated time to complete one life cycle is 1.8 to 2.5 yr for females, but only 0.8 yr for males. Maximum longevity is 2.8 yr. Instar analysis based on the segment number of pleopod rami indicated that newly hatched juveniles molt ten times to reach adult male, and four more times to reach adult female. Adult instar number was found to be only 1 for males and 5 for females. Ovigerous females occurred throughout the year, but the annual peak of release of juveniles from the female's marsupium is estimated to be arly March. Brood size was not correlated with female size, a maximum brood size of 214 eggs was recorded. The dry and ash-free dry weights of instars suggested that juveniles in the female marsupium, adult males, and older adult females are less active feeding or non-feeding stages. Except for the reduced growth rate and the occurrence of small, short-lived males, most characteristics of P. abyssalis are consistent with the present view of the life modes of mesopelagic animals, including linear growth in length, aseasonal reproduction, and smaller brood size coupled with larger eggs.

Validation of otolith-increment age estimates for a deepwater fish species, the warty oreo Allocyttus verrucosus, by radiometric analysis

Otolith increment age estimates for a deepwater species, Allocyttus verrucosus, were validated by comparison with the results from 210Pb:226Ra radiometric analysis. Transverse sectioning and subsequent grinding of otoliths to a thickness of ≃ 0.2 mm revealed increments which provided age estimates for a range of fish sizes. Age estimates ranged from 7 yr for an immature fish of 15.2 cm total length (TL) to 130 yr for a female fish of 36.5 cm TL. Age at maturity was estimated as 28 yr for females and 24 yr for males. In comparison, radiometric analysis of whole otoliths, using a single linear otolith-mass growth-rate model suggested maximum ages of 130 to 170 yr for fish of 34 to 35 cm TL. Radiometric ages were also recalculated using a two-phase otolith-mass growth-rate model in which the growth rate was assumed to slow after maturity to 90% of the pre-maturity rate. This reduced the maximum age to 132±15 yr for a mean fish length of 34.5 cm. Age at maturity for females was estimated at 34 yr. The similarity between age estimates from otolith-increment counts and radiometric analysis strongly supports the accuracy of results from both methods, and encourages further use of such comparisons as an alternative to traditional validation techniques.