Age and growth of ocellated icefish, Chionodraco rastrospinosus DeWitt and Hureau, 1979, from the South Shetland Islands

Age and growth of ocellated icefish, Chionodraco rastrospinosus, were investigated using counts of annual growth increments from sagittal otoliths. Samples were collected during research surveys by benthic trawl carried out around Elephant and South Shetland Islands in January–February 2002 and December 2006–January 2007. A total of 290 specimens were selected for the study, consisting of 120 females and 170 males. The age of fish was estimated by counting annuli on transverse sections obtained by grinding and polishing whole otoliths embedded in epoxy resin. The precision-of-age estimates within and between readers were tested applying both the average percent error (APE) and the coefficient of variation (CV). The estimated age-range was 1–12 for both sexes of C. rastrospinosus. Applying the von Bertalanffy growth function to the age–length data, a growth curve was obtained for each sex. The estimated values of VB growth parameters L _∞ and k were, respectively, 47.9 cm and 0.28 for females and 42.9 cm and 0.36 for males. Compared to other congeneric species, the growth performance of C. rastrospinosus was relatively high, being 2.82 and 2.81 in males and females, respectively. Age at sexual maturity was estimated to be about 4 years in both sexes. C. rastrospinosus captured in the studied area consisted mainly of adult specimens between 3 and 8 years, with few older fish.     

Two Bayesian methods for estimating parameters of the von Bertalanffy growth equation

The von Bertalanffy growth equation (VBGE) is commonly used in ecology and fisheries management to model individual growth of an organism. Generally, a nonlinear regression is used with length-at-age data to recover key life history parameters: L _∞ (asymptotic size), k (the growth coefficient), and t ₀ (a time used to calculate size at age 0). However, age data are often unavailable for many species of interest, which makes the regression impossible. To confront this problem, we have developed a Bayesian model to find L _∞ using only length data. We use length-at-age data for female blue shark, Prionace glauca, to test our hypothesis. Preliminary comparisons of the model output and the results of a nonlinear regression using the VBGE show similar estimates of L _∞ . We also developed a full Bayesian model that fits the VBGE to the same data used in the classical regression and the length-based Bayesian model. Classical regression methods are highly sensitive to missing data points, and our analysis shows that fitting the VBGE in a Bayesian framework is more robust. We investigate the assumptions made with the traditional curve fitting methods, and argue that either the full Bayesian or the length-based Bayesian models are preferable to classical nonlinear regressions. These methods clarify and address assumptions␣made in classical regressions using von Bertalanffy growth and facilitate more detailed stock assessments of species for which data are sparse.     

The uropod as a proxy for total length distribution in Antarctic krill: an assessment of different models

The properties of the regression of standard length on the length of the exopodit of the uropod of Euphausia superba as a method to estimate the distribution of the standard length from penguin stomach contents samples are explored. The distance between the estimated and observed distributions was measured with the Kolmogorov–Smirnov statistic. Sample variability was determined using resampling techniques. The ability of linear functions (Models I and II), allometric and non-parametric methods to recover the observed distributions was evaluated within samples and exchanging parameters between samples. Linear and allometric models proved inadequate to recover the distribution, while the differences obtained with non-parametric methods fall within the bounds of sample variability, suggesting that a linear equation does not capture the relation between total and exopodit length. The use of a non-parametric regression is recommended to increase the sample size when estimating the distributions of prey lengths in the stomach contents of Antarctic penguins.     

A geographically variable model of hemlock woolly adelgid spread

The hemlock woolly adelgid (HWA) (Adelges tsugae) has spread through the range of eastern hemlock (Tsuga canadensis) leaving dead hemlock trees in its wake. We combined county and previously unavailable township level infestation records with geographic variables including plant hardiness zone, elevation, forest cover type, urbanization, precipitation, temperature, and hemlock range in a geographic information system to build models linking HWA spread to the structure and characteristics of the environment. We explored the connections between site variables and spread rate using quantile regression, Tobit regression, a parametric model for heterogeneous error variance, and classification and regression tree modeling. The results show that since 1990 HWA has spread at a rate closer to 12.5 km/yr rather than the 20–30 km/yr previously estimated, however spread rates vary significantly with environmental variables. County-based data show a faster rate of range expansion in the south, 15.6 km/yr, and very slow spread in the northern part of the current range of HWA. The rate of spread based on township records for Pennsylvania and north is 8.13 km/yr. Our study suggests that HWA spreads more slowly in colder areas, with a mean minimum temperature of  − 26.1°C (plant hardiness zone 5B) delineating areas of slower range expansion. HWA also spreads more slowly during cold years, those with lower than average mean January temperatures. Our analysis demonstrates the value of quantile regression, Tobit regression, and classification and regression tree models for understanding the spread of invasive, exotic insects.     

Noncrossing quantile regression curve estimation

Since quantile regression curves are estimated individually, the quantile curves can cross, leading to an invalid distribution for the response. A simple constrained version of quantile regression is proposed to avoid the crossing problem for both linear and nonparametric quantile curves. A simulation study and a reanalysis of tropical cyclone intensity data shows the usefulness of the procedure. Asymptotic properties of the estimator are equivalent to the typical approach under standard conditions, and the proposed estimator reduces to the classical one if there is no crossing. The performance of the constrained estimator has shown significant improvement by adding smoothing and stability across the quantile levels.     

Femur length,body mass,and stature estimates of <Emphasis Type="Italic">Orrorin tugenensis</Emphasis>, a 6 Ma hominid from Kenya

To understand the palaeobiology of extinct hominids it is useful to estimate their body mass and stature. Although many species of early hominid are poorly preserved, it is occasionally possible to calculate these characteristics by comparison with different extant groups, by use of regression analysis. Calculated body masses and stature determined using these models can then be compared. This approach has been applied to 6 Ma hominid femoral remains from the Tugen Hills, Kenya, attributed to Orrorin tugenensis. It is suggested that the best-preserved young adult individual probably weighed approximately 35–50 kg. Another fragmentary femur results in larger estimates of body mass, indicative of individual variation. The length of the femur of the young adult individual was estimated, by using anthropoid-based regression, to be a minimum of 298 mm. Because whole-femur proportions for Orrorin are unknown, this prediction is conservative and should be revised when additional specimens become available. When this predicted value was used for regression analysis of bonobos and humans it was estimated to be 1.1–1.2 m tall. This value should, however, be viewed as a lower limit.     

Age, growth, and reproductive biology of the Waigieu seaperch Psammoperca waigiensis (Perciformes: Latidae) around Okinawa Island, Japan

Age, growth, and reproductive biology of the Waigieu seaperch Psammoperca waigiensis were studied using 291 specimens obtained around Okinawa Island, Japan. Otolith opaque zones that formed every year correlated with spawning activity and were thought to be annual rings. Growth of this species was rapid during the first 2 years, reaching 186.2–270.3 mm in standard length (SL). Females (196.6–334.0 mm SL) were larger than males (186.2–288.6 mm SL), caused by differential growth between sexes, which started before 2 years of age. Most of the specimens were 1–11 years old and accounted for 96% in total. Spawning season was estimated to be from April to October by gonadosomatic index (GSI) and histological observation. The smallest mature female and male were 217.0 mm SL (2 years) and 206.0 mm SL (2 years), respectively. After recruitment in rocky areas up to about 200.0 mm SL and 2 years of age, Psammoperca waigiensis were then found to soon mature.     

Does the early frog catch the worm? Disentangling potential drivers of a parasite age–intensity relationship in tadpoles

The manner in which parasite intensity and aggregation varies with host age can provide insights into parasite dynamics and help identify potential means of controlling infections in humans and wildlife. A significant challenge is to distinguish among competing mechanistic hypotheses for the relationship between age and parasite intensity or aggregation. Because different mechanisms can generate similar relationships, testing among competing hypotheses can be difficult, particularly in wildlife hosts, and often requires a combination of experimental and model fitting approaches. We used field data, experiments, and model fitting to distinguish among ten plausible drivers of a curvilinear age–intensity relationship and increasing aggregation with host age for echinostome trematode infections of green frogs. We found little support for most of these proposed drivers but did find that the parsimonious explanation for the observed age–intensity relationship was seasonal exposure to echinostomes. The parsimonious explanation for the aggregated distribution of parasites in this host population was heterogeneity in exposure. A predictive model incorporating seasonal exposure indicated that tadpoles hatching early or late in the breeding season should have lower trematode burdens at metamorphosis, particularly with simulated warmer climates. Application of this multi-pronged approach (field surveys, lab experiments, and modeling) to additional parasite–host systems could lead to discovery of general patterns in the drivers of parasite age–intensity and age–distribution relationships.     

Vertical distribution of fine roots in relation to soil factors in Pinus tabulaeformis Carr. forest of the Loess Plateau of China

Growth and vertical distribution of fine root closely depend on soil resource availability. Better understanding of relationships of root profile with vertical distribution of available soil resource and soil characteristics can allow ecologists to predict the fine root distribution on the scales ranging from individual plants to vegetation communities. The objective of the study was to understand the fine root mass density (FRMD), fine root length density (FRLD), fine root area density (FRAD), mean root diameter and specific root length (SRL), vertical distribution in soil profile and their relation with soil environment factors in semiarid and arid Loess Plateau of China. The vertical fine root distribution and soil bulk density, soil moisture and soil inorganic N in 0-60 cm soil profile (0–15, 15–30, 30–45 and 45–60 cm intervals) were investigated by soil coring methods in three Pinus tabulaeformis Carr. forests chosen at three locations. The fine root density parameters (FRMD, FRLD and FRAD) and SRL peaked in the most upper soil layer (0–15 cm interval) and decreased with increased soil depth. The results provided a strong support that soil water rather than soil inorganic N is a key control on fine root distribution in the Loess Plateau. With increased soil moisture, the root mass, length and SRL increased and the mean root diameter decreased. The effects of soil bulk density on the fine root parameters were consistent with those of the soil water. An unexpected result was obtained about the relationships between soil organic N and the root distributions and occurrences because of no differences among the soil depth intervals in soil inorganic N content. It might be associated with severe soil water deficit limiting soil nitrogen utilization efficiency in arid Loess Plateau.     

Carbon and nitrogen pools in a mangrove stand of <Emphasis Type="Italic">Kandelia obovata</Emphasis> (S., L.) Yong: vertical distribution in the soil–vegetation system

Attempts were made to quantify the carbon and nitrogen pools in a monospecific and pioneer mangrove stand of Kandelia obovata Sheue, Liu & Yong, Okinawa Island, Japan. The leaf C and N concentrations on a leaf area basis decreased with increasing PPFD (Photosysthetic Photon Flux Density). The total C and N stocks in foliage were estimated as 3.55 Mg ha^–1 and 0.105 Mg ha^–1, respectively. The bark (45.6–48.6% for C and 0.564–0.842% for N) contained significantly higher amount of C (P < 0.05) and N (P < 0.01) than wood (46.2–47.8% for C and 0.347–0.914% N). The total C stock of stem was 23.2 Mg ha^–1 in wood and 8.33 Mg ha^–1 in bark, and the total N stock was 0.222 Mg ha^–1 in wood and 0.116 Mg ha^–1 in bark. The root wood (37.1–45.0%) contained significantly higher amount of C than root bark (35.4–40.7%) (P < 0.01). The total C stock of root was 14.2 Mg ha^–1 in wood and 12.6 Mg ha^–1 in bark, and the total N stock of root was 0.157 Mg ha^–1 in wood and 0.155 Mg ha^–1 in bark. The soil organic C and total N stocks within 1 m soil depth were estimated as 57.3 Mg ha^–1 and 2.73 Mg ha^–1, respectively. The C pool in aboveground biomass (35.1 Mg ha^–1) was 1.3 times as large as that in belowground biomass (26.9 Mg ha^–1). However, the soil organic C pool (57.3 Mg ha^–1) was similar to the total C pool (62.0 Mg ha^–1) of vegetation, indicating that the mangrove stored a large part of production in the soil. About 50% of the C was in the soil. The N pool in aboveground biomass (0.442 Mg ha^–1) was 1.4 times as large as that in belowground biomass (0.312 Mg ha^–1). The soil N stock was 3.3 times as large as the biomass N stock (0.754 Mg ha^–1).     

Age and growth of the sandbar shark, Carcharhinus plumbeus, in Hawaiian waters through vertebral analysis

Age and growth estimates were determined for the sandbar shark, Carcharhinus plumbeus, from Oahu, Hawaii in the central Pacific Ocean. Age estimates were obtained through vertebral centra analysis of 187 sharks. We verified our age estimates through marginal increment analysis of centra and oxytetracycline marking methods of at liberty sandbar sharks. Sizes of sampled sharks ranged from 46 to 147 cm pre-caudal length. Four growth models were fitted to length-at-age data; two forms of the von Bertalanffy growth model, the Gompertz growth model, and a logistic growth model. Males and females exhibited statistically significant differences in growth, indicating that females grow slower and attain larger sizes than males. Growth parameter estimates revealed slower growth rates than previously estimated (based on captive specimens) for Hawaiian sandbar sharks. The von Bertalanffy growth model using empirical length-at-birth provided the best biological and statistical fit to the data. This model gave parameter estimates of L _∞ = 138.5 cm PCL and k = 0.12 year⁻¹ for males and L _∞ = 152.8 cm PCL, k = 0.10 year⁻¹ for females. Male and female sandbar sharks mature at approximately 8 and 10 years of age, respectively.     

Demographic characteristics of an intertidal bay goby (Lepidogobius lepidus)

Synopsis In a fourteen month study (May 1976 – June 1977) I examined the following characteristics of an intertidal bay goby (Lepidogobius lepidus) in Morro Bay, California, U.S.A.: annual and seasonal patterns of abundance, age composition and growth rates, survivorship and mortality patterns, and the reproductive cycle for female gobies. Fishes were collected with the aid of quinaldine and otoliths and ovaries removed. Age and growth rates were estimated from otolith annuli using a back calculation formula and a Brody-Bertalanffy growth curve. Mortality rates were derived using the methods of Heincke (1913), Robson & Chapman (1960), mean age, and a catch curve (Ricker 1975). A gonad index was used to describe the annual reproductive cycle. Results indicated that abundance fluctuated seasonally and that these fluctuations appeared to be caused by reproductive emigrations. Bay gobies reached an age of 7+ and a standard length of 87 mm. Growth was relatively constant (6 mm yr⁻¹) until age 5, at which point it began to decline. The mean rates of survivorship, mortality, and instantaneous mortality were 0.75, 0.25, and 0.29 respectively. Mortality rates for individual age classes ranged from 0.13 to 0.51 and increased with age. This stock appears to reproduce mainly during the winter.     

The LRRK2 Gly2385Arg variant is associated with Parkinson’s disease: genetic and functional evidence

Evidence of LRRK2 haplotypes associated with Parkinson’s disease (PD) risk was recently found in the Chinese population from Singapore, and a common LRRK2 missense variant, Gly2385Arg, was independently detected as a putative risk factor for PD in the Chinese population from Taiwan. To test the association between the Gly2385Arg variant in a large case-control sample of Chinese ethnicity from Singapore, and to perform functional studies of the wild type and Gly2385Arg LRRK2 protein in human cell lines. In a case-control study involving 989 Chinese subjects, the frequency of the heterozygous Gly2385Arg genotype was higher in PD compared to controls (7.3 vs. 3.6%, odds ratio = 2.1, 95% CI: 1.1–3.9, P = 0.014); these values yield an estimated population attributable risk (PAR) of ∼4%. In a multivariate logistic regression analysis with the disease group (PD vs. controls) as the dependent variable and the genotype as an independent factor with adjustments made for the effect of age and gender, the heterozygous Gly2385Arg genotype remained associated with an increased risk of PD compared to wild type genotype (odds ratio = 2.67, 95% CI: 1.43–4.99, P = 0.002). The glycine at position 2385 is a candidate site for N-myristoylation, and the Gly2385Arg variant replaces the hydrophobic glycine with the hydrophilic arginine, and increases the net positive charge of the LRRK2 WD40 domain. In transfection studies, we demonstrated that both the wild type and Gly2385Arg variant LRRK2 protein localize to the cytoplasm and form aggregates. However, under condition of oxidative stress, the Gly2385Arg variant was more toxic and associated with a higher rate of apoptosis. Our study lends support to the contention that the Gly2385Arg is a common risk factor for PD in the Chinese population. Our bioinformatics and in-vitro studies also suggest that the Gly2385Arg variant is biologically relevant and it might act through pro-apoptotic mechanisms.     

Identifying patterns in the diet of mackerel icefish (<Emphasis Type="Italic">Champsocephalus gunnari)</Emphasis> at South Georgia using bootstrapped confidence intervals of a dietary index

Ontogenetic, inter-annual and regional variations in diet were investigated for mackerel icefish, Champsocephalus gunnari, in three successive summer seasons around South Georgia. Stomach contents from 2239 C. gunnari (130–560 mm total length) were examined. A bootstrapping technique was used to calculate confidence intervals for an index of relative importance of prey categories (% IRI_DC). Diet varied significantly between years and age classes but there was little regional difference in diet. In general, diet was dominated by krill, Euphausia superba and by the amphipod Themisto gaudichaudii. Smaller (younger) fish tended to prey on a higher proportion of T. gaudichaudii and small euphausiids such as Thysanoessa sp. and took smaller quantities of E. superba. In a season of poor krill availability (summer of 2003–2004) the proportion of krill in the diet, stomach fullness and fish condition (indicated by length–weight relationships) were significantly lower than in the other summer seasons. A large reduction (>80%) in the estimated annual (2005) biomass of the C. gunnari stock directly followed the season of poor krill availability. This decline was largely because of mortality of 2+ and 3+ fish, which were more krill dependent than 1+ fish. Younger fish appear to have survived, leading to an increase in the estimated population biomass in 2006.     

Age and growth of the nototheniid fishTrematomus bernacchii Boulenger from Terra Nova Bay,Antarctica

Age and growth of the nototheniid fishTrematomus bernacchii Boulenger 1902 were estimated by reading the sagittal otoliths of 457 adult specimens caught off Terra Nova Bay (Ross Sea) in the austral summer 1990–1991. Annuli in ground and polished otoliths were examined using a dissecting microscope under reflected light. The Von Bertalanffy growth equation was L_t=273.5 [1 − e^{−0.109(t+2.10)}] for males (n=122) and L_t=422.2 [1 − e^{−0.055(t+1.92)}] for females (n=211) where L is total length in millimetres. Maximum estimated age was 21 years for females and 16 years for males. This is in agreement with the hypothesis that considers slow growth and old age as a typical feature of Antarctic fishes.     

Variation of mandible size in red deer<Emphasis Type="Italic">Cervus elaphus hispanicus</Emphasis> from southern Spain

An osteometric study was carried out on 126 mandibles of male and female deerCervus elaphus hispanicus Linnaeus, 1758 hunted between 1992 and 1998 in Sierra Morena (SE Spain). Age of animals was estimated in months using thin sections of the first lower molar (M1). Length measurements of the mandible were plotted against age. An analysis of variance was used to assess the influence of year of birth, sex, size of estates and deer abundance within each closed estate on mandible length. Results reveal a differential growth between males and females, along with differences in jaw morphology. Growth is complete at 55–56 months (4.5–5 years) in females and at 80–85 months (6.5–7 years) in males. The jaw angle, the condylar process and the coronoid process are larger in males. All measurements were larger in animals born in 1989 or earlier, and lower in animals born after 1993, revealing the strong influence of climatic conditions. A negative effect of the deer abundance on growth was also observed.     

Size composition and reproductive biology of the ornate jobfish <Emphasis Type="Italic">Pristipomoides argyrogrammicus</Emphasis> (Lutjanidae) off Ishigaki Island,Okinawa

The ornate jobfish Pristipomoides argyrogrammicus is an important lutjanid species for fisheries in the Okinawan region of Japan. The present study estimated the size composition and reproduction of this species in the waters around Ishigaki Island, Okinawa Prefecture. The length–frequency distribution indicated that males grow larger than females. The fork length (FL; mm)–whole body weight (BW; g) relationship and FL–total length (TL) relationship were as follows: BW = 1.048 × 10⁻⁵ FL^3.121 and TL = 1.101 × FL + 2.196, respectively. The main spawning season was estimated as between April and August, since higher gonadosomatic index (GSI) values were found for both sexes, and matured oocytes were observed in females during these months. The developmental stage of ovaries correlated with the GSI of females. Fecundity ranged from 9,530 to 98,260 oocytes in fish of 177.0 to 278.0 mm FL, and the FL–fecundity relationship was as follows: fecundity = 9.525 × 10⁻⁸ FL^4.903.     

Some biological characteristics of early larvae Dacodraco hunteri (Notothenioidei: Channichthyidae) in the western Ross Sea

Ichtyoplankton surveys were carried out in the western Ross Sea by the R/V Italica in the austral summer 1996 and 1997–1998 to study species composition and spatial distribution of larval stages of fish. One of the most abundant icefish caught was Dacodraco hunteri, a poorly known channichthyid inhabiting the high-Antarctic Zone. Based on 382 yolk-sac larvae and 13 preflexion larvae, the study was focused to estimate spatial distribution and abundance, as well as diet and growth rate. The pigmentation pattern and some morphometric measurements were also recorded for comparative purposes. The specimens were caught in relatively restricted areas located in Terra Nova Bay and north of the Ross Ice Shelf on the Challenger and Joides Basins. The standardized abundance of early larvae ranged between 0.03 and 1.72 individuals 10⁻³ m³ in 1996 and 0.16–4.53 individuals 10⁻³ m³ in 1997–1998, respectively. Fitting a linear model to the mean length increase in larvae collected in subsequent catch dates, the growth rate was estimated to be approximately 0.11 mm/day. Based on back calculation of growth rate and presumed hatch size of 11 mm, larval hatching probably took place in mid-December. Diet of preflexion larvae consisted exclusively of larvae of the pelagic nototheniid Pleuragramma antarcticum, a key species of the high-Antarctic pelagic food web. Hence, D. hunteri probably plays a more important role than previously thought in the pelagic community of the Ross Sea.     

Assessment of deep water stocks of pearl oysters at Takapoto Atoll (Tuamotu Archipelago, French Polynesia)

An assessment of natural stocks of the commercially important black pearl oyster, Pinctada margaritifera, was conducted in the lagoon of Takapoto Atoll, French Polynesia. The sampling methodology combined estimates of reef area from remote sensing, depth profiles across the lagoon, and in situ sampling using scuba. Confidence limits around estimates of mean oyster density began to stabilize after ten dives, and did not decrease further after 30. Densities of oysters increased steadily with depth, ranging from a mean of 1 per 100 m² at 0–10 m to 8/100 m² at 30–40 m. More than half of the stock occurred at depths greater than 30 m. The total stock was estimated to be 4.3 ± 0.67 million, equivalent to 834 metric tonnes (including shells). Accepted: 15 June 1999     

Growth and mortality of bigeye tuna <Emphasis Type="Italic">Thunnus obesus</Emphasis> (Scombridae) in the eastern and central tropical Pacific Ocean

Biological parameters such as age, growth and age (or size) at maturity are vital for stock assessment and management. Aging is essential in yielding such information. However, limited aging studies have been conducted for large tropical pelagic species in the eastern and central tropical Pacific Ocean. The objective of this study is to conduct a length frequency analysis for estimating growth and mortality of bigeye tuna in the eastern and central tropical Pacific Ocean using samples from the Chinese longline fishery during February to November 2006. The von Bertalanffy growth parameters of asymptotic fork length L _∞ and growth coefficient k were estimated at L _∞ = 207.4 cm fork length, k = 0.23 year^-1, and theoretical age at zero length t ₀ = −0.40 year. The total mortality rate (Z) was estimated to be 0.60; the fishing mortality rate (F) and the natural mortality rate (M) were 0.25 year^-1 and 0.35 year^-1, respectively. The exploitation rate (E) was 0.16. This study provides the estimates of growth and mortality rate for bigeye tuna in the eastern and central tropical Pacific Ocean, which can be used as biological input parameters in further stock evaluations in this region. However, age analysis, further validation of the age composition and stock structure are needed for future studies.