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

An ASPIC Based Assessment of Redfish (S. mentella and S. fasciatus) in NAFO Divisions 3LN (assuming that the highest apparently sustained historical average level of catch is a sound proxy to MSY)

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. Both CPUE and surveys were used with all observations of each series. This assessment is not a follow up of the previous ones (Ávila de Melo et al., 2012 and 2010). The logistic Schaefer production model (1954) incorporated in ASPIC operating model (Prager, 1994) can not cope anymore with the most recent biomass increases observed in both spring and (mainly) autumn Canadian 3LN surveys, unless it is allowed to provide unrealistic assessment results. And continuing to strip off the highs of each one of these series, in order to get a picture in line to what is the perception of the stock history from commercial and survey data trends, is no longer a valid option, as reflected on the last STACFIS research recommendation on this matter (NAFO, 2012). Being so, input has been reframed opening room to a new combination of Canadian autumn 3L and 3N surveys. The inclusion of the Spanish spring survey on Div. 3N and the removal of the historical CPUE series have also been considered. Two selected frameworks options have finally run with MSY kept constant at an initial starting guess, instead of being estimated by the model. Before entering the latest (2013) ASPIC Suite flow, the input selected from exploratory analysis was submitted to a sensitivity test in order to evaluate the robustness of the new framework against variability on random number seed, start user guesses for key model parameters and last year survey biomass. The consistency of the new ASPIC assessment with their predecessors was checked by comparison of biomass and fishing mortality fit trajectories against previous ones from the 2012 and 2010 assessments. A 2014-2012 retrospective analysis was also performed with good results (small retro bias on relative biomass and fishing 2 mortality in response to the general increase of the still standing survey series), and the assessment pursued successfully to bootstrap mode (again good consistency with previous results) and projections. A medium term management plan is finally proposed, based on bi-annual increases of the catch from the present TAC level of 6 500 t up to target catch/TAC of 18 100 t, the 2014 equilibrium yield from the present assessment, that should be in place by 2019-2020. This management plan allows, with a very high probability, that biomass is kept above Bmsy and fishing mortality below Fmsy

Selectivity of 130 mm Mesh Size in Deep Sea Bottom Trawl Fishery in NAFO Regulatory Area

In February 1995 the European Union carried out a selectivity survey on board a Spanish commercial trawler, using the codend-cover method. The objective was to study the selectivity of 130 mm mesh size for the deep sea trawl fisheries in the NAFO Regulatory Area. One hour and four hour hauls were carried out and results obtained for Greenland halibut (Reinhardtius hippoglossoides), American plaice (Hippoglossoides platessoides), roughhead grenadier (Macrourus berglax) and threebeard rockling (Gaidropsarus ensis). For the two flatfish species, the proportion of retention increased with the duration of the haul. This increase reflected in a decrease of the corresponding selection factor. It also varied with the size of fish. The selection factor was greater in smaller individuals, and this induced an asymmetry in the selectivity curve. For the groundfish species, data were enough only to fit the four hour selectivity curves, which appeared more symmetrical than the flatfish ones

Selectivity of 130 mm Mesh Size in Deep Sea Bottom Trawl Fishery in NAFO Regulatory Area

In February 1995 the European Community carried out .a selectivity campaign on board of a Spanish commercial trawler, using the codend cover method. The objective was to study the selectivity of 130 mm mesh size for the deep sea trawl fisheries in the NAFO Regulatory Area. One hour and four hour hauls were used and results obtained for Greenland halibut, American plaice, roughhead grenadier and theebeard rockling. For the two flatfish species the proportion of retention increase with the duration of the haul. This increase, reflected in a decrease of the corresponding selection factor, also varies with the size of fish, being greater in smaller individuals, and induces an asymmetry in the selectivity curve. For the roundfish species data were enough only to fit the four hour selectivity curves, both appearing more symmetrical than the flatfishes ones

GadCap: A GADGET multispecies model for the Flemish Cap cod, redfish and shrimp.

Since late 1980s, the demersal community of Flemish Cap (NAFO area 3M) has experienced large variations (including the collapse) in the abundance and population structure of its main fishing resources: cod Gadus morhua, redfish Sebastes sp. and shrimp Pandalus borealis, with alternation in their dominant role in the ecosystem. GadCap is an EU project dealing with the development of a GADGET multispecies model for the Flemish Cap cod, redfish and shrimp, as part of the NAFO roadmap for the EAF. The effect of fishing, trophic interactions (including cannibalism) and water temperature in the dynamic of these three major fishing resources has been modeled. The results highlight the interdependent dynamic of these stocks, and reveals strong interactions between recruitment, fishing and predation (including cannibalism), with marked changes in their relative importance by species-age-length over time. The multispecies model shows that disregarding the species interactions would lead to serious underestimates of natural mortality, overestimations of the exploitable biomass, and highlights the need to move beyond single-species management in this highly coupled ecosystem. Preliminary estimates of total SSB and MSY, under different combinations of fishing mortality for all the three stocks, are also presented.Postprint0,000

An Assessment of Beaked Redfish (S. mentella and S. fasciatus) in NAFO Division 3M (With a Revised Approach to Quantify the Increase on Redfish Natural Mortality Determined by the Increase on Cod Predation Observed Over Recent Years, 2006-2012)

The 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, and the Flemish Cap cod fishery reopened in 2010. These new realities implied a revision of catch estimates, in order to split recent redfish commercial catch and by-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 1989-2012 EU survey. 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. The most likely hypothesis to justify this unexpected downward trend on stock size is an increase in natural mortality by cod predation. From the sensitive analysis, natural mortality at 0.4 was applied on ages 4-6 through 2006-2010, and extended to ages 7 plus on 2009 and 2010. It has been kept constant through all ages on 2011 and 2012, but with an overall decline to 0.125.This is the highest possible level of natural mortality giving assessment results in line with the recent survey trends and at the same time with key diagnostics very close to the best ones, obtained with the return on 2011-2012 to the “standard” redfish natural mortality of 0.1. A 2013-2009 retrospective XSA was also carried out, being this assessment very much in line with their immediate predecessors (2012-2011). Above average year classes coupled with low fishing mortalities allowed a rapid growth of biomass and abundance since 2003 that pushed the stock to a 2008-2009 high. Between 2009 and 2011 biomass and abundance of exploitable and 7 plus female stock went down for causes other than fishing. These declines were halted at well above average levels on the terminal year and, at least for biomass, there was some improvement on 2012. The recruitment at age 4 increased from 2002 till 2006 and was kept at a high level until 2009, with 2005 year class as the most abundant year class of the assessment interval. Recruitment to exploitable stock declined since then and is approaching the level of the weak year classes from the 1990’s. Short and medium term stochastic projections were obtained for female spawning stock biomass (SSB) under Fstatusquo , together with SSB and yield medium term probability profiles. As it was documented on the 2011 assessment F0.1 is an unacceptable management option at the current beaked redfish stock status. Keeping on 2014 and 2015 fishing mortality at its present low level will sustain on the short term a high level of female spawning biomass. But on the long term it will be natural mortality to determine the future of beaked redfish as a fishery resource

Measurement of the cosmic ray spectrum above 4×10184{\times}10^{18} eV using inclined events detected with the Pierre Auger Observatory

A measurement of the cosmic-ray spectrum for energies exceeding $4{\times}10^{18}$ eV is presented, which is based on the analysis of showers with zenith angles greater than $60^{\circ}$ detected with the Pierre Auger Observatory between 1 January 2004 and 31 December 2013. The measured spectrum confirms a flux suppression at the highest energies. Above $5.3{\times}10^{18}$ eV, the "ankle", the flux can be described by a power law $E^{-\gamma}$ with index $\gamma=2.70 \pm 0.02 \,\text{(stat)} \pm 0.1\,\text{(sys)}$ followed by a smooth suppression region. For the energy ($E_\text{s}$) at which the spectral flux has fallen to one-half of its extrapolated value in the absence of suppression, we find $E_\text{s}=(5.12\pm0.25\,\text{(stat)}^{+1.0}_{-1.2}\,\text{(sys)}){\times}10^{19}$ eV.Comment: Replaced with published version. Added journal reference and DO

Energy Estimation of Cosmic Rays with the Engineering Radio Array of the Pierre Auger Observatory

The Auger Engineering Radio Array (AERA) is part of the Pierre Auger Observatory and is used to detect the radio emission of cosmic-ray air showers. These observations are compared to the data of the surface detector stations of the Observatory, which provide well-calibrated information on the cosmic-ray energies and arrival directions. The response of the radio stations in the 30 to 80 MHz regime has been thoroughly calibrated to enable the reconstruction of the incoming electric field. For the latter, the energy deposit per area is determined from the radio pulses at each observer position and is interpolated using a two-dimensional function that takes into account signal asymmetries due to interference between the geomagnetic and charge-excess emission components. The spatial integral over the signal distribution gives a direct measurement of the energy transferred from the primary cosmic ray into radio emission in the AERA frequency range. We measure 15.8 MeV of radiation energy for a 1 EeV air shower arriving perpendicularly to the geomagnetic field. This radiation energy -- corrected for geometrical effects -- is used as a cosmic-ray energy estimator. Performing an absolute energy calibration against the surface-detector information, we observe that this radio-energy estimator scales quadratically with the cosmic-ray energy as expected for coherent emission. We find an energy resolution of the radio reconstruction of 22% for the data set and 17% for a high-quality subset containing only events with at least five radio stations with signal.Comment: Replaced with published version. Added journal reference and DO