Low power laser generated ultrasound : signal processing for time domain data acquisition

The use of low power modulated laser diode systems has previously been established as a suitable method for non-destructive laser generation of ultrasound. Using a quasi-continuous optical excitation amplified by an erbium-doped fibre amplifier (EDFA) allows flexible generation of ultrasonic waves, offering control of further parameters such as the frequency content or signal shape. In addition, pseudo-random binary sequences (PRBS) can be used to improve the detected impulse response. Here we compare two sequences, the m-sequence and the Golay code, and discuss the advantages and practical limits of their application with laser diode based optical excitation of ultrasound

Low power laser generated ultrasound : signal processing for time domain data acquisition

The use of low power modulated laser diode systems has previously been established as a suitable method for non-destructive laser generation of ultrasound. Using a quasi-continuous optical excitation amplified by an erbium-doped fibre amplifier (EDFA) allows flexible generation of ultrasonic waves, offering control of further parameters such as the frequency content or signal shape. In addition, pseudo-random binary sequences (PRBS) can be used to improve the detected impulse response. Here we compare two sequences, the m-sequence and the Golay code, and discuss the advantages and practical limits of their application with laser diode based optical excitation of ultrasound

Game Refinement Relations and Metrics

We consider two-player games played over finite state spaces for an infinite number of rounds. At each state, the players simultaneously choose moves; the moves determine a successor state. It is often advantageous for players to choose probability distributions over moves, rather than single moves. Given a goal, for example, reach a target state, the question of winning is thus a probabilistic one: what is the maximal probability of winning from a given state? On these game structures, two fundamental notions are those of equivalences and metrics. Given a set of winning conditions, two states are equivalent if the players can win the same games with the same probability from both states. Metrics provide a bound on the difference in the probabilities of winning across states, capturing a quantitative notion of state similarity. We introduce equivalences and metrics for two-player game structures, and we show that they characterize the difference in probability of winning games whose goals are expressed in the quantitative mu-calculus. The quantitative mu-calculus can express a large set of goals, including reachability, safety, and omega-regular properties. Thus, we claim that our relations and metrics provide the canonical extensions to games, of the classical notion of bisimulation for transition systems. We develop our results both for equivalences and metrics, which generalize bisimulation, and for asymmetrical versions, which generalize simulation

Eledone cirrhosa and SPICT or why it is not easy to assess a short lived cephalopod species

Poster.-- Iberian Symposium on Modeling and Assessment of Fishery Resources, 19-22 October, Vigo, SpainAlthough some cephalopods have had always commercial value and others started to increase in value in recent years, unlike European Atlantic stocks of many commercially important finfish and crustaceans, they are not routinely assessed and no specific management measures are applied to fleets catching cephalopods, with the exception of some regional harvest control rules for artisanal fleets. Among the species that has been gaining importance in landings is the horned octopus Eledone cirrhosa. This octopus represents an important bycatch for several North Spanish otter trawl fisheries, appearing in landings but also in discards. Like other cephalopods, E. cirrhosa is a short-lived and fast growing species, and previous studies showed that its abundance varies in relation to physical and environmental conditions. As a first step towards its possible future inclusion in the ICES annual assessment system, a simple assessment model has been tested in the ICES Working Group on Cephalopod Fisheries and Life History (WGCEPH). The chosen model was SPICT (Surplus Production model in Continuous Time). Using landings and two abundance indices (from a commercial fleet and a scientific bottom trawl survey), preliminary results have been obtained. Overall, although the model converged and all the diagnostics were acceptable, the estimated parameters obtained very wide confidence intervals, suggesting that improvements in the model are needed. Further work, including testing other assessment models or selecting other tuning indices, will help in the assessment process for this speciesN

Trends in the pattern of discarding in the hake (Merluccius hubbsi and Merluccius australis) fishery in the SW Atlantic.

This paper presents results from the EC Study Project 99/016 “Data collection for stock assessment of two hakes (Merluccius hubbsi and M. australis) in international and Falkland waters of the SW Atlantic”. Historical fishery and biological data series available from IEO (1988 onwards) were used to describe and quantify patterns and spatio-temporal changes in catches and discards in the hake fishery. Data were collected by scientific observers on board Spanish fishing vessels operating in the study area. Data collected on fishing activity included effort, catches and discards of target and non-target species on a haul-by-haul basis. Biological information (size, sex, maturity, etc) on target species was recorded on a daily basis, while biological data on non-target species was recorded periodically. The “discards ratio” was calculated by each haul, defined as the total weight of fish discarded divided by the total catch weight. The most important by-catch species are hoki or whiptailed hake (Macruronus magellanicus), red cod (Salilota australis), southern blue whiting (Micromesistius australis), Patagonian toothfish (Dissostichus eleginoides) and kingclip (Genypterus blacodes). Discards included both target and non-target species. The most commonly discarded species were Patagonotothen spp. (almost 100% of the catch is discarded), whiptailed hake (Macruronus magellanicus) (25% discarded), southern blue whiting (12%) and red cod (6%). These percentages vary with area, year and fishing season. The four target species (Merluccius hubbsi, Merluccius australis, Illex argentinus and Loligo gahi) have discard ratios below 5%. In recent years discard ratios for all species except Patagonotothen spp. have fallen below 15%

The trophic relationships of several commercial finfish species from the southwest Atlantic.

This study aims to quantify the trophic relationships of seven commercially valuable predatory fish species (Argentine hake Merluccius hubbsi, southern hake Merluccius australis, Patagonian toothfish Dissostichus eleginoides, southern blue whiting Micromesistius australis australis, red cod Salilota australis, kingclip Genypterus blacodes and hoki Macruronus magellanicus) over a two-year period. A total of 1590 stomachs from these species was collected from the high seas of the southwest Atlantic and in the waters around the Falkland Islands. The percentage similarity index shows that all species except southern hake occupy very similar trophic positions, with a high percentage dietary overlap. Despite this, niche breadths were relatively narrow, with the majority of feeding occurring on locally abundant prey items (notothiniid fish and the squids Illex argentinus and Loligo gahi). In the two species for which sample size was largest, Argentine hake and kingclip, geographical differences in diet were found, which may be related to regional variation in prey abundance. The results are discussed in relation to the seasonal migrations of predators and prey and the hydroclimate regime

The spatio-temporal pattern of hake (M. hubbsi) abundance and environmental influence in the Patagonian shelf area

The Argentine hake (Merluccius hubbsi) is one of the most important fishery resources in the Southwest Atlantic. This species is widely distributed in the Patagonian shelf area and it is a major target species by international fleets in this South West Atlantic area. This paper presents results on the spatio-temporal distribution pattern of hake M. hubbsi abundance and environmental influence in the Patagonian shelf area. Spanish commercial fisheries data from 1989 to 1999 were used in the analysis. Data were collected by observers deployed by the IEO, Vigo (Instituto Español de Oceanografía, Vigo). The data include 15343 fishing haul records. CPUE (Catch Per Unit Effort, kg⋅hr-1) was used as an abundance index. The analyses of the general spatio-temporal pattern of fish abundance, and the influence of environmental factors, such as SST, SBT, depth, moon phase and cloud cover, on fish abundance and distribution, were based on correlation, variograms, and timeseries maps created using GIS. Hake-targeted fishing by Spanish fleets was mainly focused on the shelf-edge area between 44.5°S – 47.0°S outside the Argentinean EEZ and in the area northwest of the Falkland Islands. The centre of high abundance is located in the shelf-edge area between 44.5°S – 47.0°S, particularly in the west part (i.e. in shallower waters) and in winter. The correlations between fish abundance and cloud cover are overwhelming negative, indicating that higher catches usually occur in cloudy weather conditions. In the major hake-targeted fishing area between 44.5°S – 47.0°S, the negative relationship between fish abundance and sea surface temperature in most months may suggest that high fish abundance is related to the strong northward cold Falklands current, and abundance is positively related to sea depth in summer

Fisheries interactions of Delphinus delphis in the north-east Atlantic with an emphasis on Galicia, north-west Spain.

Bycatch from interactions with fisherie s remains the biggest global threat to marine mammals. Galicia, north - west Spain, is one of the world’s main fishing regions and a high level of cetacean - fisheries interactions has been reported from on - board observers, interviews with fisheries stakeholde rs and analysis of stranded and by - caught carcasses. Delphinus delphis is the most abundant cetacean in the area and since 1990 necropsies of over 1800 stranded and by - caught Delphinus have been conducted. Life history data (age, maturity, and pregnancy ra te data) from stranded and by - caught cetaceans can be used to construct life tables and to estimate overall mortality and fisheries mortality rates. Age and maturity were determined from stranded and by - caught Delphinus between 1990 and 2009. Males and fem ales reach sexual maturity at 8.5 and 7.5 years of age, respectively, and no temporal difference in age at sexual maturity was observed. Results indicate 13% annual mortality in the Delphinus delphis north - east Atlantic population and necropsy data suggest s that 60% of mortality (i.e. 7.2% annual mortality) is attributable to fisheries interactions, predominantly from pair trawls and gillnets. By - caught Delphinus were found to die significantly younger than non - by - caught animals (p=<0.001) although no sex - r elated difference in bycatch rate was observed (p=0.051). The estimated annual mortality due to fisheries interactions greatly exceeds the 2% limit set by ASCOBANS and the IWC and high bycatch rates are also reported for other countries e.g. the UK, France and Portugal. Although Delphinus delphis in the north - east Atlantic is one continuous population, the high level of bycatch occurring in parts of the range is most likely unsustainable and will be discussed. There is a need to carry out on - board monitorin g, notably in the north - west Iberian Peninsula (Galicia and Portugal), to incorporate cetacean bycatch into fisheries advice and, above all, to start introducing mitigation measures

Are there climatic signals in fishery data for sardine (Sardina pilchardus) along the Iberian Atlantic coast?

The Iberian sardine (Sardina pilchardus) is distributed along the whole shelf of the Iberian Peninsula with the highest catches being taken from southern Galician waters and northern Portugal. The fishery is dependent on the strength of the recruitment in this area and recruitment processes seem to be driven by a combination of oceanographic (local) and climatic (global) events. In an exploratory analysis we examined whether the variability observed in landings from ICES areas VIIIc (northern) and IXa (western Iberia) from 1940 to 2005, and in estimated annual recruitment and spawning stock size for the whole stock could be related to environmental conditions at large and local scales, taking into account temporal autocorrelation in the response variables. Landings for areas VIIIc and IXa show differing trends and were most strongly related, respectively, to the multi-decadal Atlantic oscillation (AMO) and to SST (with an optimum around 15o C). Recruitment was negatively related to air temperature (AT). We stress the need for taking into account time lagged effects, non linear relationships, autocorrelation in response variables and collinearity between explanatory variables. We discuss possible mechanisms underlying these observed patterns and whether the apparent climatic relationships have any predictive value

Microplastics in the stomach contents of common dolphin (Delphinus delphis) stranded on the Galician coasts (NW Spain, 2005–2010)

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