Filaments in Galactic Winds Driven by Young Stellar Clusters

The starburst galaxy M82 shows a system of H$\alpha$-emitting filaments which extend to each side of the galactic disk. We model these filaments as the result of the interaction between the winds from a distribution of Super Stellar Clusters (SSCs). We first derive the condition necessary for producing a radiative interaction between the cluster winds (a condition which is met by the SSC distribution of M82). We then compute 3D simulations for SSC wind distributions which satisfy the condition for a radiative interaction, and also for distributions which do not satisfy this condition. We find that the highly radiative models, that result from the interaction of high metallicity cluster winds, produce a structure of H$\alpha$ emitting filaments, which qualitatively agrees with the observations of the M82, while the non-radiative SSC wind interaction models do not produce filamentary structures. Therefore, our criterion for radiative interactions (which depends on the mass loss rate and the terminal velocity of the SSC winds, and the mean separation between SSCs) can be used to predict whether or not an observed galaxy should have associated H$\alpha$ emitting filaments.Comment: 10 pages, 6 Figures. ApJ Accepted, August 7, 200

An Assessment of American Plaice (Hippoglossoides platessoides) in NAFO Division 3M

The present assessment evaluates the status of the 3M American plaice stock. The catch at age matrix, EU survey abundance at age and the respective mean weights were updated. The XSA and a VPA-type Bayesian model were applied to this stock, but the XSA presented unrealistic results. The surveys and models indicate that the stock suffered a continuous decline, even with catches kept at a low level since 1996. A general decrease is observed in the biomass and abundance estimated by the several surveys. The EU survey and VPA-type Bayesian model indicates only poor recruitment from 1991 to 2005 year class. SSB recorded a minimum in 2009, in recent years SSB indices increase with the income of the strong 2006 year class in the SSB but in 2013 this increase seems to halt mainly as there were fewer older fish (ages 16+). There are no changes in the perception of the stock status from last assessment (2011). This stock continues to be in a poor condition, despite the apparent improvement of the recruitment since 2006 (mainly due to the 2006 year class). Although the level of catches is low since 1996, this stock has been kept at a low level

An ASPIC Based Assessment of Redfish (S. mentella and S. fasciatus) in NAFO Divisions 3LN (can a surplus production model cope with bumpy survey data?)

There are two species of redfish in Divisions 3L and 3N, the deep-sea redfish (Sebastes mentella) and the Acadian redfish (Sebastes fasciatus) that have been commercially fished and reported collectively as redfish in fishery statistics. Redfish in Div. 3LN is regarded as a management unit composed of two Grand Bank populations from those two very similar redfish species. The present ASPIC assessment is based on the logistic form of a non-equilibrium surplus production model (Schaeffer, 1954; Prager, 1994), adjusted to a standardized catch rate series (Power, 1997) and to most of the stratified-random bottom trawl surveys conducted in various years and seasons in Div. 3L and Div. 3N from 1978 onwards. These surveys were framed according to the input formulation previously adopted on the 2nd take of the ASPIC 2008 assessment (Ávila de Melo and Alpoim, 2010a). The assessment was preceded by an exploratory analysis to check the response of the model to the inclusion of the Spanish spring survey series on Div. 3N and to the 2010-2011 update of the remaining three Canadian survey series that are at present the backbone input of this assessment. Each of these series includes recently high points that are well above their overall increasing trends, observed 2002 onwards. The analysis point out that in terms of consistency with previous assessments and the past history of the redfish fishery, as well as performance of the model, the ASPIC 2012 option with the exclusion of the Spanish survey and the removal of the recent outliers from the respective Canadian series represents the better update of the survey data input framework. The chosen input formulation run afterwards with different last year survey results and different starting guesses for key parameters and different random number seeds, in order to test the robustness of ASPIC results to turbulence in the inputs used to initialize the model deterministic run. A 2012 versus 2010 ASPIC comparative assessment (both on FIT and BOT modes) and a 2012-2010 retrospective analysis were also carried out to check the consistency between the two last full assessments and the magnitude of bias on relative biomass and fishing mortality in response to the general increase of the still standing survey series. Regardless the input formulations, the starting guess region, the mode of the ASPIC runs or the retrospective patterns, the 2012 assessment reiterates the main conclusion of the previous ones: the biomass of redfish in Div. 3LN is above Bmsy , while fishing mortality is well below Fmsy . Most recent catches continue to be at a low level on the historical context of this fishery and the answer of the stock to a direct fishery of the magnitude of years between the mid 1960’s and the mid 1980’s is unknown. Projections were made on the short term, in order to select a 2013-2012 catch roof large enough to consolidate the reopening of a redfish direct fishery on divisions 3L and 3N but keeping a high probability of the stock staying above Bmsy. This high probability is defined by the lower 80% confidence limit of the projected relative biomass trajectory being at or above Bmsy in 2013-2015

The status of redfish (S. mentella and S. fasciatus) in Divisions 3LN at present and the likelihood its follow up in the near future (under the ongoing the Management Strategy or a status quo TAC scenario)

There are two species of redfish in Divisions 3L and 3N, the deep-sea redfish (Sebastes mentella) and the Acadian redfish (Sebastes fasciatus) that have been commercially fished and reported collectively as redfish in fishery statistics. Both species, occurring on Div. 3LN and managed as a single stock, don’t belong to isolated local populations but, on the contrary, are part of a large Northwest Atlantic complex ranging from the Gulf of Maine to south of Baffin Island. The ASPIC assessment of this stock is based on the logistic form of a non-equilibrium surplus production model (Schaeffer, 1954; Prager, 1994), adjusted to a standardized catch rate series (Power, 1997) and to all stratified-random bottom trawl surveys conducted in various years and seasons in Div. 3L and Div. 3N from 1978 onwards. Both CPUE and surveys were used with all observations within each series. The 2018 assessment proceed on the threshold of the new 2014 approach, the main features of the previous input framework were kept, with MSY fixed at 1960-1985 average catch and the rest of the approved 2014 assessment framework updated. Despite its poor performance the 3L Spanish survey has been kept in the analysis due to its high correlation with the autumn 3LN Canadian survey, one of the two backbone series of the assessment. ASPIC results confirm a stable stock from the 1960’s to the first half of the 1980’s, sustaining an average yield of 21 000t. Stock declined with a sudden rise of the catch over the late 1980’s first half of the 1990’s, and started to gradually recover after catches fell to a residual level when the stock collapse. The maximum observed sustainable yield (MSY) of 21 000 t can be a long term sustainable yield if fishing mortality stands at 0.11/year, exploiting a correspondent Bmsy at 187 000 t. From assessment results there is a high probability (CL’s 80%) that the stock was at the beginning of 2018 above Bmsy, after crossing 2017 under a fishing mortality most likely below 34% Fmsy

An assessment of beaked redfish (S. mentella and S. fasciatus) in NAFO division 3M (with an approach to the likely impact of recent 3M cod growth on redfish natural mortality)

65 páginas, 12 tablas, 10 figuras.-- Scientific Council MeetingThe 3M redfish assessment is focused on the beaked redfish, regarded as a management unit composed of two populations from two very similar species: the Flemish Cap S. mentella and S. fasciatus. The reason for this approach is the historical dominance of this group in the 3M redfish commercial catch until 2005. However a new golden redfish fishery (S. marinus) started on September 2005 on shallower depths of the Flemish Cap bank above 300m. This new reality implied a revision of catch estimates, in order to split recent redfish commercial catch from the major fleets on Div. 3M into golden (S. marinus) and beaked (S. mentella and S. fasciatus) redfish catches. An Extended Survivor Analysis (Shepherd, 1999) was used with the same framework of previous assessments and with the tuning of the 1989-2010 EU survey. Recent survey results suggest that the beaked redfish stock has not been able to hold its growth and sustain an above average level, suffering instead a severe decline on the second half of the 2000’s. For several reasons, the most likely hypothesis to justify this unexpected downward trend on stock size is an increase in mortality other than fishing mortality. From the sensitive analysis, carried out for a set of natural mortality options, a natural mortality of 0.4 (fixed for ages 4-6 through 2006-2010, and ages 7+ on 2009 and 2011) was adopted. This is the lowest possible level of natural mortality giving assessment results in line with the recent survey declines and at the same time with key diagnostics very close to the best ones, obtained with a higher natural mortality of 0.55. A 2011-2007 retrospective XSA was also carried out. When compared to previous assessments, these retrospective present more consistent trends namely as regards female spawning biomass and average fishing mortality, coupled with a non systematic bias signal. Very high fishing mortalities until 1996 forced a rapid decline of abundance, biomass and female spawning biomass. With lower fishing mortalities since then, the stock decline was halted. The weak 1991-1997 year classes kept the stock size at a low level till 2003, basically sustained by the survival and growth of the existing cohorts. Recruitment at age 4 increased from 2002 till 2006, when the 2002 year class was at an historical high, and from 2006 to 2008 fell as fast as it went up, still continuing to decrease on most recent years and being on 2010 just bellow average. Above average year classes coupled with fishing mortalities in the vicinity of F0.1 or even lower allowed a rapid growth of biomass and abundance since 2003 and sustained the stock at a high level on 2007-2008. However the stock decreased on the last couple of years despite low catch and, being still above average level, there are no signs that the present decline rate is slowing down. Female spawning stock component experienced a similar decline. Short and medium term stochastic projections were obtained for female spawning stock biomass (SSB) under Fstatusquo (average 2008-2010 fishing mortality), together with SSB and yield medium term probability profiles. Keeping fishing mortality at its present low level well below F0.1 will sustain on the short term the female spawning stock biomass above the SSB interval from where all the abundant year classes from the past decade where generated. But on the long term it will be natural mortality to determine the future of beaked redfish as a fishery resource. The average 2012-2013 Fstatusquo catch for beaked redfish will be 2 of 3,200 tons. According to 2008-2010 observed catch data from the Portuguese, Spanish and Russian National Sampling Programmes on board, a beaked redfish annual catch of 3,200 tons would correspond to an overall 3M redfish catch (including the shallower golden redfish catches) near 7,000 tons (6,840 tons)This assessment is part of a EU research project supported by the European Commission (DG XIV, Program for the collection of data in fisheries sector), IPIMAR, CSIC, IEO and AZT

A Revised Update of the 2014 ASPIC Assessment of Redfish (S. mentella and S. fasciatus) in Divisions 3LN (how the the stock is coping with the actual Management Strategy and its likely impact on the next coming years).

There are two species of redfish in Divisions 3L and 3N, the deep-sea redfish (Sebastes mentella) and the Acadian redfish (Sebastes fasciatus) that have been commercially fished and reported collectively as redfish in fishery statistics. Both species, occurring on Div. 3LN and managed as a single stock, don’t belong to isolated local populations but, on the contrary, are part of a large Northwest Atlantic complex ranging from the Gulf of Maine to south of Baffin Island. The present ASPIC assessment of this stock is based on the logistic form of a non-equilibrium surplus production model (Schaeffer, 1954; Prager, 1994), adjusted to a standardized catch rate series (Power, 1997) and, for the first time, to all stratified-random bottom trawl surveys conducted in various years and seasons in Div. 3L and Div. 3N from 1978 onwards. Both CPUE and surveys were used with all observations within each series. In order to proceed on the threshold of the new 2014 approach, and taking into account that since then no substantial changes appear to have occurred on the state of the stock, the main features of the previous input framework were kept, with MSY fixed at 1960-1985 average catch and the rest of the approved 2014 assessment framework updated. The 3L Spanish survey, the only ongoing survey so far outside the analysis, has now been successfully included on this assessment framework (relative inter-quartile range from bootstrap analysis for the last two assessments highlight the higher consistence of most of the 2016 assessment results when compared with the ones from 2014). ASPIC assessment results confirm a stable stock from the 1960’s to the first half of the 1980’s, sustaining an average yield of 21 000t. Stock declined with a sudden rise of the catch over the late 1980’s first half of the 1990, and increased since then, after catches fell to a residual level with the stock collapse. Assessment results also confirm that the maximum observed sustainable yield (MSY) of 21 000 t can be a long term sustainable yield if fishing mortality stands at 0.11/year, exploiting a correspondent Bmsy at 190 000 t. 2 There is a very high probability that the stock was at the beginning of 2016 at or above Bmsy , after crossing 2015 under a fishing mortality most likely at or below 50% Fmsy. There is also a very high probability that catch on 2016 at 10 400 t TAC and on 2017 and 2018 at the predicted increases approved in the 2014 Risk‐Based Management Strategy for 3LN Redfish, will keep fishing mortality on 2018 below Fmsy and biomass at the beginning of 2019 above Bmsy.Postprint0,000

The status of redfish (S. mentella and S. fasciatus) in Divisions 3LN and two medium term scenarios (when recruitment is low, Risk Based Management Strategy or common sense?)

There are two species of redfish in Divisions 3L and 3N, the deep-sea redfish (Sebastes mentella) and the Acadian redfish (Sebastes fasciatus) that have been commercially fished and reported collectively as redfish in fishery statistics. Both species, occurring on Div. 3LN and managed as a single stock, don’t belong to isolated local populations but, on the contrary, are part of a large Northwest Atlantic complex ranging from the Gulf of Maine to south of Baffin Island. The ASPIC assessment of this stock is based on the logistic form of a non-equilibrium surplus production model (Schaeffer, 1954; Prager, 1994), adjusted to a standardized commercial catch rate series (Power, 1997) and to all stratified-random bottom trawl surveys conducted in various years and seasons in Div. 3L and Div. 3N from 1978 onwards. Both CPUE and surveys were used with all observations within each series. The 2020 assessment proceed on the threshold of the new 2014 approach, with MSY fixed at 1960- 1985 average catch and the rest of the approved 2014 assessment framework updated. ASPIC results present a stock stable from the 1960’s to the first half of the 1980’s while sustaining an average yield of 21 000t. Stock declined with a sudden rise of the catch over the late 1980’s first half of the 1990’s, and started to gradually recover after catches fell to a residual level in response to stock collapse. The maximum observed sustainable yield (MSY) of 21 000 t is linked to a Fmsy at 0.11/year and a Bmsy at 185 000 t. There is a high probability (>90%) that the stock was at least 38% above Bmsy at the beginning of 2020, after crossing 2019 under a fishing mortality not higher than 46% Fmsy

Winds from clu\sters with non-uniform stellar distributions

We present analytic and numerical models of the `cluster wind' resulting from the multiple interactions of the winds ejected by the stars of a dense cluster of massive stars. We consider the case in which the distribution of stars (i.e., the number of stars per unit volume) within the cluster is spherically symmetric, has a power-law radial dependence, and drops discontinuously to zero at the outer radius of the cluster. We carry out comparisons between an analytic model (in which the stars are considered in terms of a spatially continuous injection of mass and energy) and 3D gasdynamic simulations (in which we include 100 stars with identical winds, located in 3D space by statistically sampling the stellar distribution function). From the analytic model, we find that for stellar distributions with steep enough radial dependencies the cluster wind flow develops a very high central density and a non-zero central velocity, and for steeper dependencies it becomes fully supersonic throughout the volume of the cluster (these properties are partially reproduced by the 3D numerical simulations). Therefore, the wind solutions obtained for stratified clusters can differ dramatically from the case of a homogeneous stellar distribution (which produces a cluster wind with zero central velocity, and a fully subsonic flow within the cluster radius). Finally, from our numerical simulations we compute predictions of X-ray emission maps and luminosities, which can be directly compared with observations of cluster wind flows.Comment: 10 pages, 11 figures. MNRAS - Accepted 2007 June 29. Received 2007 June 28; in original form 2007 May 2