Discard Mortality of Sea Scallops Following Capture and Handling in the Sea Scallop Dredge Fishery - Final Report

The focus of sea scallop, Placopecten magellanicus, management over the past 20 years has been to encourage the harvest of larger animals. This has been accomplished through a series of management measures including gear modifications, effort controls, crew size limitations and spatial management to protect juvenile scallops. While these measures have been effective in reducing the harvest of small scallops, their capture does still occur. Central to fully understanding the impact of the fishery on the resource, is a comprehensive estimate of the non-harvest mortality associated with commercial operations. Non-harvest mortality can be broken down into a number of different processes, with discard mortality being a major category. Discard mortality (DM) is the rate of mortality associated with animals that are captured and subsequently released due to primarily market factors. The latest stock assessment for sea scallops assumes that 20% of all animals discarded will die. There is considerable uncertainty associated with this estimate that is based on a single older tagging study and studies examining a non-Placopecten species under different biotic and abiotic conditions

Discard Mortality of Sea Scallops Placopecten magellanicus Following Capture and Handling in the U.S. Dredge Fishery

Discard mortality can represent a potentially significant source of uncertainty for both stock assessments and fishery management measures. While the family Pectinidae is considered to be robust to the capture and handling process, understanding species-specific discard mortality rates is critical to characterize both population dynamics and to develop regulatory measures to meet management objectives. The discard mortality rate for the U.S. dredge fishery of sea scallop Placopecten magellanicus was estimated empirically via a retention study aboard industry vessels under commercial conditions. Over 16,000 sea scallops were assessed via a composite index of scallop vitality that consisted of semiqualitative measures of both overt trauma (shell damage) and response to stimuli. Results indicate that overall sea scallop discard mortality was 21% and consistent with the values currently assumed in the stock assessment. Survival mixture models support the utility of a simple metric of physical trauma as an effective predictor of mortality. Exposure time was also identified as a positively correlated factor that was important in describing the discard mortality process. Application of experimental results highlight the need to consider some operational characteristics of the fishery to reduce potential discard mortality

Cephalopods caught in the outer Patagonian shelf and its upper and medium slope in relation to the main oceanographic features

Ninety cephalopod specimens were collected in 71 of the 132 hauls (54%) during the bottom trawl survey ATLANTIS 2009 undertaken between 24 February and 1 April 2009. The surveyed area was the zone between parallels 44° and 48° South, east of the Argentinean Exclusive Economic Zone down to the 1500 m depth contour on the high seas of the Southwest Atlantic. The collection was composed of 16 species of squids and 5 of octopods. The best represented groups were Histioteuthidae (5 species) and Octopodidae (5). The most abundant species were Gonatus antarcticus (25.5%), Histioteuthis atlantica (11.1%), and Muusoctopus eureka (8.9%), which were also the most widely encountered. The geographic and/or bathymetric distribution ranges of 9 species are extended, and this is the first record of Galiteuthis glacialis outside circumpolar Antarctic waters. Our data show that several species, mainly of octopuses, penetrate the area studied as the plume of cold sub-Antarctic waters is pushed far into the Southwestern Atlantic by the Falkland (Malvinas) Current.Peer reviewe

On the influence of inlet perturbations on slug dynamics in horizontal multiphase flow—a computational study

When multiphase flows are modeled numerically, complex geometrical and operational features of the experiments, such as the phase mixing section, are often not resolved in detail. Rather simplified boundary conditions are prescribed, which usually cause less irregular dynamics in the system than present in reality. In this paper, a perturbation that randomly disturbs the secondary components of the velocity vector at the inlet is proposed in order to capture the experimentally observed instabilities at the interface between the phases. This in particular enhances the formation of slugs in the pipe. Different amplitudes of the perturbation are investigated. One observes that, the higher the perturbation amplitude, the earlier the slugs occur. On the other hand, sufficiently far away from the inlet, the flow pattern shows the same dynamics for different perturbation amplitudes. Hence, no specific frequency is imposed by the prescribed perturbation. The simulation results are validated by comparison with liquid level data from a corresponding experiment

Influence of parallel magnetic fields on a single-layer two-dimensional electron system with a hopping mechanism of conductivity

Large positive (P) magnetoresistance (MR) has been observed in parallel magnetic fields in a single 2D layer in a delta-doped GaAs/AlGaAs heterostructure with a variable-range-hopping (VRH) mechanism of conductivity. Effect of large PMR is accompanied in strong magnetic fields by a substantial change in the character of the temperature dependence of the conductivity. This implies that spins play an important role in 2D VRH conductivity because the processes of orbital origin are not relevant to the observed effect. A possible explanation involves hopping via double occupied states in the upper Hubbard band, where the intra-state correlation of spins is important.Comment: 10 pages, 4 jpeg figure

Universal Crossover between Efros-Shklovskii and Mott Variable-Range-Hopping Regimes

A universal scaling function, describing the crossover between the Mott and the Efros-Shklovskii hopping regimes, is derived, using the percolation picture of transport in strongly localized systems. This function is agrees very well with experimental data. Quantitative comparison with experiment allows for the possible determination of the role played by polarons in the transport.Comment: 7 pages + 1 figure, Revte

Decomposing the misery index: A dynamic approach

YesThe misery index (the unweighted sum of unemployment and inflation rates) was probably the first attempt to develop a single statistic to measure the level of a population’s economic malaise. In this letter, we develop a dynamic approach to decompose the misery index using two basic relations of modern macroeconomics: the expectations-augmented Phillips curve and Okun’s law. Our reformulation of the misery index is closer in spirit to Okun’s idea. However, we are able to offer an improved version of the index, mainly based on output and unemployment. Specifically, this new Okun’s index measures the level of economic discomfort as a function of three key factors: (1) the misery index in the previous period; (2) the output gap in growth rate terms; and (3) cyclical unemployment. This dynamic approach differs substantially from the standard one utilised to develop the misery index, and allow us to obtain an index with five main interesting features: (1) it focuses on output, unemployment and inflation; (2) it considers only objective variables; (3) it allows a distinction between short-run and long-run phenomena; (4) it places more importance on output and unemployment rather than inflation; and (5) it weights recessions more than expansions