Abundance estimation of Northeast Atlantic mackerel based on tag recapture data—A useful tool for stock assessment?

In the present study we utilize tag recapture data to estimate year class abundance and spawning stock biomass of mackerel (Scomber scombrus L.) in the Northeast Atlantic for the period 1986–2008. On average 20,000 jigged mackerel have been tagged annually with internal steel tags in the spawning area west of Ireland and the British Isles, and the tags have been recaptured in commercial catches screened through metal detectors. The spawning stock biomass estimates derived from two different tag-based models were highly variable but were on average 2 and 2.3 times higher than the ICES official estimate. The official estimate is considered uncertain and most likely an underestimate of the actual biomass, due to unregistered mortality in the fisheries and lack of fishery-independent, age-disaggregated data. Hence, tag-based estimates could potentially improve the current assessment if included in the ICES stock assessment on a regular basis. These estimates also involve some uncertainty that needs consideration, especially related to variable tagging mortality, detector efficiency and migrations of the stock.     

The Effect of Cholesterol on the Long-Range Network of Interactions Established among Sea Anemone Sticholysin II Residues at the Water-Membrane Interface

Actinoporins are α-pore forming proteins with therapeutic potential, produced by sea anemones. Sticholysin II (StnII) from Stichodactyla helianthus is one of its most extensively characterized members. These proteins remain stably folded in water, but upon interaction with lipid bilayers, they oligomerize to form a pore. This event is triggered by the presence of sphingomyelin (SM), but cholesterol (Chol) facilitates pore formation. Membrane attachment and pore formation require changes involving long-distance rearrangements of residues located at the protein-membrane interface. The influence of Chol on membrane recognition, oligomerization, and/or pore formation is now studied using StnII variants, which are characterized in terms of their ability to interact with model membranes in the presence or absence of Chol. The results obtained frame Chol not only as an important partner for SM for functional membrane recognition but also as a molecule which significantly reduces the structural requirements for the mentioned conformational rearrangements to occur. However, given that the DOPC:SM:Chol vesicles employed display phase coexistence and have domain boundaries, the observed effects could be also due to the presence of these different phases on the membrane. In addition, it is also shown that the Arg51 guanidinium group is strictly required for membrane recognition, independently of the presence of Chol.     

Harvesting of leaf-hay shaped the Swedish landscape

The hypothesis that the harvesting of leaf-hay was of great importance in agriculture and consequently had a substantial impact on deciduous forest areas is verified. The main sources are ethnological records collected from elderly informants, mainly between 1920 and 1940. At many farmsteads, leaf-hay was the main, and sometimes only, fodder used for sheep and goats. Information is presented from different districts in Sweden on the number of leaf-sheaves normally harvested at farmsteads and consumed during winter per goat and sheep (the median is 200). It is estimated that nearly 200 million leaf-sheaves were consumed annually by sheep and goats in Sweden around 1850. Horses, cattle and swine were also given leaf-hay, but the amount consumed has not been estimated because of poorer sources. The harvested quantity indicates that the greater part of the Swedish deciduous forest landscape in populated areas was exploited in the 19th century; at least one million hectares of land covered by deciduous trees were exploited. In forested areas, most of the leaf-hay was harvested on outland, usually by felling trees. In plain areas in the southern half of Sweden, a larger part was harvested on the infields, where pollards were also more common. The use of leaf-hay declined during the 19th century Swedish agrarian revolution. During the first half of the 20th century, the practice was also abandoned in forested areas.This revised version was published online in May 2005 with corrections to the Cover Date.