Growth Parameters of Sentani Gudgeon Fish (Oxyeleotris heterodon) in Sentani Lake, Papua

ABSTRACTThe Sentani Gudgeon Fish (Oxyeleotris heterodon, Weber 1907) from the family Butidae with the general name Sentani Gudgeon is known locally as Gabus Malas and Himen. Sentani Snakehead Fish is one source of animal protein that is very important for the community around Lake Sentani. The population of the Sentani Gudgeon Fish species is at a crucial level. The issue could be affected by environmental pressures, continuous catches, competition with introduced species from outside Papua, intensive predation systems, and imbalances in ecological systems. The condition made a decline in population size until it became extinct. Gudgeon Sentani fish is the main target of catching in the lake. This condition significantly affects stock, size when first captured, population decline, reproductive cycle, and average catch. Until now, data and information on the growth of snakehead fish as the basis for fisheries management in the waters of Lake Sentani are not widely known. Considering the importance of preserving the native species of Lake Sentani, especially the Snakehead Fish, efforts to manage the fisheries in Lake Sentani's waters are urgent. This research was conducted in March - October 2020, located at Lake Sentani. The specimens were obtained from the catch of fishers with various gill nets and chopsticks. Enumerators or field assistants assisted the recording of the number and measurement of the total length of fish caught by fishermen daily. The results of the analysis showed: asymptotic size (L?) 46.20 cm, growth coefficient (K) 0.29, the total mortality rate (Z) 0.80 per year, natural mortality (M) 0.74 per year, the mortality rate due to fishing (F) 0.06 per year and exploitation rate (E) 0.075 per year.

Robust inference in deconvolution

Kotlarski's identity has been widely used in applied economic research based on repeated‐measurement or panel models with latent variables. However, how to conduct inference for these models has been an open question for two decades. This paper addresses this open problem by constructing a novel confidence band for the density function of a latent variable in repeated measurement error model. The confidence band builds on our finding that we can rewrite Kotlarski's identity as a system of linear moment restrictions. Our approach is robust in that we do not require the completeness. The confidence band controls the asymptotic size uniformly over a class of data generating processes, and it is consistent against all fixed alternatives. Simulation studies support our theoretical results.

Age, growth, and mortality of silver carp Hypophthalmichthys molitrix (Valenciennes, 1844) in the middle and lower reaches of the Pearl River, and implications for management and conservation

This study aimed to determine the age, growth, mortality, and population structure of the economically important cyprinid silver carp Hypophthalmichthys molitrix (Valenciennes, 1844) in the middle and lower reaches of the Pearl River. A total of 297 silver carp were sampled quarterly from the catches of gillnet fishermen, at six sites, between June 2019 and September 2020. Standard length of the specimens ranged from 130 to 585 mm, and body weight ranged from 45.5 to 3930 g. The length–weight relationship parameter b values reached 3.015. Age was determined through examination and measurements of fish scales, and the age composition of the sampled silver carp varied from 0+ to 4+. Fitting the new data to the von Bertalanffy growth model, we obtained an asymptotic size (L∞) of 1107 mm, k of 0.135, and t0 of −0.666 for silver carp in this stretch of the river. The calculated growth performance index ϕ and estimated longevity tmax were 5.22 and 21.56, respectively. The rates of total mortality, natural mortality, and fishing mortality were calculated as 0.4997, 0.1621, and 0.3377, respectively, while the exploitation ratio was evaluated as 0.6757. The overall results confirm overexploitation of this resource in the middle and lower reaches of the Pearl River. It was concluded that this species should be protected from capture until at least 790 mm in standard length, representing an optimal minimum size for capture to benefit conservation of the species and to sustainably develop this valuable fishery.

Simultaneous Inference for High-Dimensional Approximate Factor Model

This paper studies simultaneous inference for factor loadings in the approximate factor model. We propose a test statistic based on the maximum discrepancy measure. Taking advantage of the fact that the test statistic can be approximated by the sum of the independent random variables, we develop a multiplier bootstrap procedure to calculate the critical value, and demonstrate the asymptotic size and power of the test. Finally, we apply our result to multiple testing problems by controlling the family-wise error rate (FWER). The conclusions are confirmed by simulations and real data analysis.

ROBUST TESTS FOR WHITE NOISE AND CROSS-CORRELATION

Commonly used tests to assess evidence for the absence of autocorrelation in a univariate time series or serial cross-correlation between time series rely on procedures whose validity holds for i.i.d. data. When the series are not i.i.d., the size of correlogram and cumulative Ljung–Box tests can be significantly distorted. This paper adapts standard correlogram and portmanteau tests to accommodate hidden dependence and nonstationarities involving heteroskedasticity, thereby uncoupling these tests from limiting assumptions that reduce their applicability in empirical work. To enhance the Ljung–Box test for non-i.i.d. data, a new cumulative test is introduced. Asymptotic size of these tests is unaffected by hidden dependence and heteroskedasticity in the series. Related extensions are provided for testing cross-correlation at various lags in bivariate time series. Tests for the i.i.d. property of a time series are also developed. An extensive Monte Carlo study confirms good performance in both size and power for the new tests. Applications to real data reveal that standard tests frequently produce spurious evidence of serial correlation.

Tests for nonlinear restrictions under misspecified alternatives with an application to testing rational expectation hypotheses

Summary This paper develops generalized method of moments-based (GMM-based) Lagrange multiplier tests for nonlinear hypotheses that are robust to locally misspecified possibly nonlinear alternatives. The procedure is based on an initial consistent GMM estimator of the parameters under a given set of nonlinear restrictions. The new test for one particular set of nonlinear hypotheses is consistent and has correct asymptotic size independently of whether the other, also nonlinear hypotheses, are correct or locally misspecified. To illustrate the usefulness of our proposed tests we consider testing rational expectations hypotheses using U.S. data.

Growth and development of North Pacific gray whales (Eschrichtius robustus)

Understanding variability in growth patterns of marine mammals provides insights into the health of individuals and status of populations. Body growth of gray whales (Eschrichtius robustus) has been described for particular life stages, but has not been quantified across all ages. We derived a comprehensive growth equation for gray whales by fitting a two-phased growth model to age-specific length data of eastern North Pacific gray whales that were captured, stranded, or harvested between 1926 and 1997. To predict mass-at-age, we used the allometric relationship between mass and length. We found that on average (± SD), calves were 4.6 ± 0.043 m and 972 ± 26 kg at birth, and reached 8.5 ± 0.095 m and 6,019 ± 196 kg by the end of their first year of life (n = 118). Thus, calves almost double (2×) in length and octuple (8×) in mass while nursing, and are effectively about two-thirds of their asymptotic adult length and one-third of their maximum mass when weaned. The large sample of aged individuals (n = 730) indicates that gray whales live up to ~48 years and have a life expectancy of < 30 years. Adult females attain a mean (± SD) asymptotic size of 13.1 ± 0.048 m and 20,758 ± 222 kg, while the smaller males average 12.6 ± 0.048 m and 19,938 ± 222 kg at ~40 years of age. Females are thereby ~4% longer and heavier than males. These age-specific estimates of body size can be used to estimate food requirements and assess nutritional status of individuals.

The hidden army: corallivorous crown-of-thorns seastars can spend years as herbivorous juveniles

Crown-of-thorns seastar (COTS) outbreaks are a major threat to coral reefs. Although the herbivorous juveniles and their switch to corallivory are key to seeding outbreaks, they remain a black box in our understanding of COTS. We investigated the impact of a delay in diet transition due to coral scarcity in cohorts reared on crustose coralline algae for 10 months and 6.5 years before being offered coral. Both cohorts achieved an asymptotic size (16–18 mm diameter) on algae and had similar exponential growth on coral. After 6.5 years of herbivory, COTS were competent coral predators. This trophic and growth plasticity results in a marked age–size disconnect adding unappreciated complexity to COTS boom–bust dynamics. The potential that herbivorous juveniles accumulate in the reef infrastructure to seed outbreaks when favourable conditions arise has implications for management of COTS populations.