Egg production of Baltic cod (Gadus morhua) in relation to variable sex ratio, maturity, and fecundity

Observed fluctuations in relative fecundity of Eastern Baltic cod (Gadus morhua L.) were related to food availability during the main feeding period and were used to develop a predictive model that explained 72% of the interannual variations in fecundity. Time series of sex ratios, maturity ogives, and relative fecundity were combined with mean weights-at-age and stock sizes from an analytical multispecies model to estimate the potential egg production (PEP). Relationships between PEP and independent estimates of realized daily and seasonal egg production from egg surveys were highly significant. The difference between estimates of potential and realized seasonal egg production was of a magnitude corresponding to the expected loss of eggs as a result of atresia, fertilization failure, and early egg mortality. The removal of interannual variability in sex ratio, maturity, and fecundity on estimates of PEP deteriorated the relationships in all three cases. PEP proved to be superior to spawning stock biomass as measure of the reproductive potential in a stock-recruitment relationship of Eastern Baltic cod. PEP in combination with the reproductive volume explained 61% of the variation in year-class strength at age 2

Imaging Observations of Quasi-Periodic Pulsatory Non-Thermal Emission in Ribbon Solar Flares

Using RHESSI and some auxiliary observations we examine possible connections between spatial and temporal morphology of the sources of non-thermal hard X-ray (HXR) emission which revealed minute quasi-periodic pulsations (QPPs) during the two-ribbon flares on 2003 May 29 and 2005 January 19. Microwave emission also reveals the same quasi-periodicity. The sources of non-thermal HXR emission are situated mainly inside the footpoints of the flare arcade loops observed by the TRACE and SOHO instruments. At least one of the sources moves systematically both during the QPP-phase and after it in each flare that allows to examine the sources velocities and the energy release rate via the process of magnetic reconnection. The sources move predominantly parallel to the magnetic inversion line or the appropriate flare ribbon during the QPP-phase whereas the movement slightly changes to more perpendicular regime after the QPPs. Each QPP is emitted from its own position. It is also seen that the velocity and the energy release rate don't correlate well with the flux of the HXR emission calculated from the sources. The sources of microwaves and thermal HXRs are situated near the apex of the loop arcade and are not stationary either. Almost all QPPs and some spikes of HXR emission during the post-QPP-phase reveal the soft-hard-soft spectral behavior indicating separate acts of electrons acceleration and injection, rather than modulation of emission flux by some kinds of magnetohydrodynamic (MHD) oscillations of coronal loops. In all likelihood, the flare scenarios based on the successively firing arcade loops are more preferable to interpret the observations, although we can not conclude exactly what mechanism forces these loops to flare up.Comment: 22 pages, 10 figure

Impacts of Deepwater Horizon on Fish and Fisheries: What Have we Learned about Resilience and Vulnerability in a Coupled Human-Natural System?

The Deepwater Horizon (DWH) oil spill occurred in a region of the Gulf of Mexico (GoM) supporting abundant, diverse and valuable communities of fishes and fishers. The economy of the northern GoM is inextricably tied to the natural resource bases of the region (tourism, fishing, oil and gas, etc.) and thus the coupling between the human and ecological systems is tight and subject both feed-back and, to some extent, feed-forward controls. Management actions taken during the 87-day DWH spill incident included the closure of over 280,000 km2 of productive fishing area (about 1/3 of USA federal waters in the GoM), resulting in significant declines in catches and revenues for some critical species for several months after the spill. As well, a variety of oil spill countermeasures including the use of chemical dispersants (at the well head and the sea surface), releases of freshwater into marshes to staunch the progression of oil ashore, creation of sand berms, burning of oil at sea and mechanical pickup were employed. Because of the closures, fishers were compensated for lost fishing opportunities in a number of ways, including employment in oil spill response efforts (the VoO or Vessel of Opportunity program), accepting compensation payments from the Responsible Parties, and moving fishing areas and shifting to open areas of the GoM. Some fisheries were heavily impacted during 2010 (e.g., menhaden and inshore invertebrate fisheries), while for others, area shifting resulted in little change in GoM-wide fishery catches (e.g., red snapper, penaeid shrimps). In the 10 years since the DWH disaster, many fisheries have recovered, exhibiting patterns of inter-annual variability consistent with those seen prior to the spill, but other species have shown little to no recovery. One of the critical issues in understanding oil spill effects is that of causal inference given multiple simultaneous drivers and feedbacks, thus the appeal of viewing fish-fishery interactions as a coupled human and natural system. Results of long-term monitoring studies document a variety of responses of various taxa occupying diverse habitats from estuarine/coastal to open ocean. These impacts resulted both from oil contamination and from various response countermeasures. Differential recovery trajectories are mediated by life history aspects contributing to resilience and to some extent the degree of ongoing contamination from pools of residual oil and other chronic sources. Relatively resilient species were those exhibiting low to moderate modularity (near ubiquitous species or populations) and those with relatively short life cycles. Fishing community resilience to the spill was related to a variety of employment alternatives during closures and facilitated by the capacity of fishers to adapt to non-traditional opportunities in fishing and by financial assistance programs. Overall, the level of business failures during and just after DWH was lower than historical averages for important reef fish fisheries of the Gulf

Sistema de reprodução em populações de Eschweilera ovata (Cambess.) Miers Mating system in Eschweilera ovata (Cambess.) Miers populations

O sistema de reprodução de duas populações de Eschweilera ovata foi quantificado por análise de isoenzimas em estrutura de progênies usando os modelos misto de reprodução e cruzamentos correlacionados. Desvios do modelo misto de reprodução foram evidenciados entre as freqüências alélicas dos óvulos e do pólen e pela heterogeneidade nas freqüências alélicas do pólen que fecundou as diferentes árvores. A taxa de cruzamento multilocos foi alta em ambas populações Camarugipe (t m =0,999&plusmn;0,004) e Itaparica (t m=0,985&plusmn;0,023). A alta variação na taxa de cruzamento individual (t variando de 0,320 a 1,000) indicou que a espécie não é auto-incompatível. Diferenças positivas e significativamente diferentes de zero foram detectadas entre a taxa de cruzamento multiloco e uniloco, indicando cruzamentos endogâmicos em ambas populações Camarugipe (t m-t s =0,066&plusmn;0,014) e Itaparica (t m-t s =0,073&plusmn;0,016) e possível estruturação genética espacial. Valores altos de cruzamentos biparentais foram detectados nas populações (Camarugipe, r p=0,577&plusmn;0,088; Itaparica r p =0,423&plusmn;0,070), demonstrando que as progênies são constituídas principalmente por misturas de meios-irmãos e irmãos-completos. O coeficiente de coancestria nas progênies de ambas as populações (Camarugipe, tetaxy=0,211; Itaparica tetaxy =0,191) foi superior ao esperado em progênies de meios irmãos (0,125). Os resultados foram discutidos sob a ótica de amostragens para melhoramento, conservação genética e coleta de sementes para recuperação ambiental.<br>The mating system of two populations of Eschweilera ovata was studied by allozymes analysis of progeny arrays using the mixed-mating model and correlated mating model. Deviations from mixed-mating model were evident from differences in pollen and ovule allele frequencies and allele frequency heterogeneity of pollen pools that fertilized the different trees. The multilocus outcrossing rate was high in both Camarugipe (t m=0.999&plusmn;0.004) and Itaparica populations (t m=0.985&plusmn;0.023). The high variation in individual outcrossing rate (t ranged from 0.320 to 1.000) indicated that the species is not self-incompatible. Positive differences and significantly different from zero between multilocus and single locus outcrossing rate were detected, indicating biparental inbreeding in both Camarugipe (t m - t s=0.066&plusmn;0.014) and Itaparica populations (t m - t s=0.073&plusmn;0.016) and possible spatial genetic structuring. Higher values of correlated mating were detected in the populations (Camarugipe, r p=0.577&plusmn;0.088; Itaparica r p=0.423&plusmn;0.070), showing that the families consisted mainly of half-sib and full-sib mixtures. The coancestry coefficient within families from both populations (Camarugipe, thetaxy=0.211; Itaparica thetaxy=0.191) was higher than the expected in half-sib families (0.125). The results were discussed from the point of view of sampling for improvement, genetic conservation and seed collection aiming at environmental recovery