Estimating life history parameters of European hake using Bayesian models

Sustainability and Maximum Sustainable yield (MSY) are nowadays the main fishery management goals, which are mainly addressed through single stock assessment models. However, there is a need of increasing the number of stocks assessed and improve the quality of existing assessments. The stock assessment is based on models that link the fishing activity to population dynamics based on biological processes. A common problem when starting to develop a stock assessment model for a specific species is that the biological knowledge for some processes is poor or even absent (frequently for M but also growth). In these cases, the lack of prior knowledge can be replaced with empirical estimates. The theory of life history invariants states (in general) that for a similar taxa, k/M and Lm/Linf tend to be relatively constant. This theory highlights two helpful considerations: one that whether you know one parameter you can estimate the other and two that those parameters cannot vary since they are correlated. Within this frame, life history invariants theory and hierarchical Bayesian models can be combined to better understand biological processes needed in most stock assessment models (maturity, growth and natural mortality) providing the required parameters together with their statistical structure (posterior distributions). In order to perform this meta-analysis, bibliographic life history parameters for different hake species all over the world have been collected and analysed. The results of these parameters could be useful to help in the configuration of biological processes of hake stock assessment models

Biphasic in vitro maturation with C-type natriuretic peptide enhances the developmental competence of juvenile-goat oocytes

In vitro embryo production success in juvenile animals is compromised due to their intrinsic lower oocyte quality. Conventional in vitro maturation (IVM) impairs oocyte competence by inducing spontaneous meiotic resumption. A series of experiments were performed to determine if maintaining meiotic arrest during a pre-maturation culture phase (pre-IVM) prior to conventional IVM improves oocyte competence of juvenile-goat (2 months old) cumulusoocyte complexes (COCs). In experiment 1, COCs were cultured with C-type natriuretic peptide (CNP; 0, 50, 100, 200 nM) for 6 and 8 h. Nuclear stage was assessed, revealing no differences in the incidence of germinal vesicle (GV) breakdown. In experiment 2, the same CNP concentrations were assessed plus 10 nM estradiol, the known upstream agonist activating expression of NPR2, the exclusive receptor of CNP. CNP (200 nM) plus estradiol increased the rate of oocytes at GV stage at 6 h compared to control group (74.7% vs 28.3%; P<0.05) with predominantly condensed chromatin configuration. In experiment 3, relative mRNA quantification revealed NPR2 expression was down-regulated after pre-IVM (6 h). In experiment 4, analysis of transzonal projections indicated that pre-IVM maintained cumulus-oocyte communication after oocyte recovery. For experiments 5 and 6, biphasic IVM (6 h pre-IVM with CNP and estradiol, plus 24 h IVM) and control IVM (24 h) were compared. Biphasic IVM increased intra-oocyte glutathione and decreased ROS, up-regulated DNA-methyltransferase 1 and pentraxin 3 expression and led to an increase in rate of blastocyst development compared to control group (30.2% vs 17.2%; P<0.05). In conclusion, a biphasic IVM, including a pre-IVM with CNP, maintains oocyte meiotic arrest for 6 h and enhances the embryo developmental competence of oocytes from juvenile goats

Assessing sex dimorphic species using Stock Synthesis: the case of the Atlantic southern hake stock

Southern European hake (Merluccius merluccius) is a quite relevant stock in social and economic terms in Iberian waters. Even though there are some knowledge gaps that have complicated the implementation of a data rich model to provide a sound catch advice and it is currently assessed with a data limited model. Due to the need for a new assessment model, it was decided to use Stock Synthesis (SS) (Methot and Wetzel (2013), as it is one of the main models currently used for age- and length-based species (such as the South Atlantic hake stock). As an integrated model, SS allows the input of incomplete trends of data from different sources, such as catch data, catch per unit effort (CPUE) and survey indices. Among the multiple configurations of SS, we can find the alternative of single biology (sex, growth and natural mortality), as established in the previous stock assessment model, or separate sexes. In addition, this model allows to indicate that each stock entity starts to grow in the first month of the year, but also different recruitment peaks can be specified. It is important to mention that i) European hake is a highly dimorphic species as females are considerably larger than males, ii) this stock presents different spawning peaks throughout the year and iii) information on the sex-separated size distribution and hence the sex ratio of the stock has been recently obtained from oceanographic surveys. For these reasons, alternative SS models with various configurations have been tested for this species. Results are presented and discussed together in order to find the best alternative for the assessment of this stock

Biphasic in vitro maturation with C-type natriuretic peptide enhances the developmental competence of juvenile-goat oocytes

In vitro embryo production success in juvenile animals is compromised due to their intrinsic lower oocyte quality. Conventional in vitro maturation (IVM) impairs oocyte competence by inducing spontaneous meiotic resumption. A series of experiments were performed to determine if maintaining meiotic arrest during a pre-maturation culture phase (pre-IVM) prior to conventional IVM improves oocyte competence of juvenile-goat (2 months old) cumulus-oocyte complexes (COCs). In experiment 1, COCs were cultured with C-type natriuretic peptide (CNP; 0, 50, 100, 200 nM) for 6 and 8 h. Nuclear stage was assessed, revealing no differences in the incidence of germinal vesicle (GV) breakdown. In experiment 2, the same CNP concentrations were assessed plus 10 nM estradiol, the known upstream agonist activating expression of NPR2, the exclusive receptor of CNP. CNP (200 nM) plus estradiol increased the rate of oocytes at GV stage at 6 h compared to control group (74.7% vs 28.3%; P<0.05) with predominantly condensed chromatin configuration. In experiment 3, relative mRNA quantification revealed NPR2 expression was down-regulated after pre-IVM (6 h). In experiment 4, analysis of transzonal projections indicated that pre-IVM maintained cumulus-oocyte communication after oocyte recovery. For experiments 5 and 6, biphasic IVM (6 h pre-IVM with CNP and estradiol, plus 24 h IVM) and control IVM (24 h) were compared. Biphasic IVM increased intra-oocyte glutathione and decreased ROS, up-regulated DNA-methyltransferase 1 and pentraxin 3 expression and led to an increase in rate of blastocyst development compared to control group (30.2% vs 17.2%; P<0.05). In conclusion, a biphasic IVM, including a pre-IVM with CNP, maintains oocyte meiotic arrest for 6 h and enhances the embryo developmental competence of oocytes from juvenile goats.Sandra Soto-Heras, Irene Menéndez-Blanco, Maria-Gracia Catalá, Dolors Izquierdo, Jeremy G. Thompson, Maria-Teresa Parami

Kinks in the Hartree approximation

The topological defects of the lambda phi^4 theory, kink and antikink, are studied in the Hartree approximation. This allows us to discuss quantum effects on the defects in both stationary and dynamical systems. The kink mass is calculated for a number of parameters, and compared to classical, one loop and Monte Carlo results known from the literature. We discuss the thermalization of the system after a kink antikink collision. A classical result, the existence of a critical speed, is rederived and shown for the first time in the quantum theory. We also use kink antikink collisions as a very simple toy model for heavy ion collisions and discuss the differences and similarities, for example in the pressure. Finally, using the Hartree Ensemble Approximation allows us to study kink antikink nucleation starting from a thermal (Bose Einstein) distribution. In general our results indicate that on a qualitative level there are few differences with the classical results, but on a quantitative level there are some import ones.Comment: 20 pages REVTeX 4, 17 Figures. Uses amsmath.sty and subfigure.sty. Final version, fixed typo in published versio