Recreational value of Southern Bluefin Tuna fishing

Southern bluefin tuna (Thunnus Maccoyii) is a global resource, which is critically endangered. The Committee for the Conservation of Southern Bluefin Tuna sets commercial quota levels for member nations, including Australia, each year. However, southern bluefin tuna is also a popular “trophy” fish with recreational anglers. The size of the total recreational catch, which is not included in the quota, is unknown but thought to be significant. This paper reports the findings of a study designed to estimate the recreational value of the non-commercial southern bluefin tuna catch at Portland, in southwest Victoria. The results indicate that the size of the recreational catch at Portland is considerable and therefore significant in terms of the management of the fishery. Furthermore, the non-market recreational values associated with the fishery are substantial with the on-site recreational use value (consumer surplus) per person per visit estimated to be between $33 and $132 and the on-site annual recreational use value of the fishery for one season is estimated to be between $449,533 and $1,325,124.

Controlling morphology and porosity of porous siloxane membranes through water content of precursor microemulsion

Here we report a facile method for controlling the morphology and porosity of porous siloxane membranes through manipulation of the water content of precursor microemulsions. The polymerizable microemulsion precursors consisted of a methacrylate-terminated siloxane macromonomer (MTSM) as the oil phase, nonionic surfactant (Teric G9A8), water, and cosurfactant (isopropanol). Photo-polymerization of the oil phase in the parent microemulsion solutions resulted in polymeric solids, and subsequent removal of the extractable components yielded porous PDMS membranes. The pre-cured parent microemulsion solutions and post-cured polymers were characterized by small angle X-ray scattering (SAXS) while the nanostructures of extracted porous polymer membranes were characterized by SAXS, scanning electron microscopy (SEM) and mercury porosimetry. The results indicated that nano- and micro-structures of the membranes could be modulated by the water content of the precursor microemulsions. Further, in situ photo-rheometry was used to follow the microemulsion polymerization process. The rate of polymerization and the mechanical properties of the resulting PDMS membranes also depend on the water content of precursor microemulsions. This study demonstrates a simple approach to the fabrication of a variety of novel porous PDMS membranes with controllable morphology and porosity.

Hybridization of Southern Hemisphere blue whale subspecies and a sympatric area off Antarctica : impacts of whaling or climate change?

Understanding the degree of genetic exchange between subspecies and populations is vital for the appropriate management of endangered species. Blue whales (Balaenoptera musculus) have two recognized Southern Hemisphere subspecies that show differences in

Variation in body condition during the post-moult foraging trip of southern elephant seals and its consequences on diving behaviour

Mature female southern elephant seals (Mirounga leonina) come ashore only in October to breed and in January to moult, spending the rest of the year foraging at sea. Mature females may lose as much as 50% of their body mass, mostly in lipid stores, during the breeding season due to fasting and lactation. When departing to sea, post-breeding females are negatively buoyant, and the relative change in body condition (i.e. density) during the foraging trip has previously been assessed by monitoring the descent rate during drift dives. However, relatively few drift dives are performed, resulting in low resolution of the temporal reconstruction of body condition change. In this study, six post-breeding females were equipped with time-depth recorders and accelerometers to investigate whether changes in active swimming effort and speed could be used as an alternative method of monitoring density variations throughout the foraging trip. In addition, we assessed the consequences of density change on the swimming efforts of individuals while diving and investigated the effects on dive duration. Both descent swimming speed and ascent swimming effort were found to be strongly correlated to descent rate during drift dives, enabling the fine-scale monitoring of seal density change over the whole trip. Negatively buoyant seals minimized swimming effort during descents, gliding down at slower speeds, and reduced their ascent swimming effort to maintain a nearly constant swimming speed as their buoyancy increased. One per cent of seal density variation over time was found to induce a 20% variation in swimming effort during dives with direct consequences on dive duration.