Résultats de la recherche
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Length-based assessments revisited – why stock status and fishing mortality of long-lived species such as toothfish cannot be inferred from length-frequency data alone
/ Description: In many of CCAMLR’s new and exploratory fisheries, stock assessment techniques are still in ... development. The failure of the tag-recapture program to provide robust assessments in many areas and doubts ... and fishing mortality from length-frequency data alone. In this paper, a number of length-based stock ... assessment methods are revisited and some limitations in their ability to draw robust inferences about stock ... Reference year 2000 First year of projection 2001 Years to project stock in simulation 60 y Reference ... in regards to constant recruitment and mortality can introduce significant biases. A strong year ... (1991) who found that biases may occur even when the population was in equilibrium. Fur- ther ... start date in year 01/12 Increments within year 12 Reasonable upper bound for annual F 5.0 ...
Science Journal Paper : CCAMLR Science, Volume 18 (CCAMLR Science, Volume 18) : 57–73 : Auteur(s): Ziegler, P.E., D.C. Welsford and A.J. Constable
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Seabird interactions with longlining operations for Dissostichus eleginoides at the South Sandwich Islands and South Georgia
mortality was seen and only one bird was caught on a hook; nevertheless many species in these aggregations ... of birds are clearly potentially vulnerable to setting operations in daylight hours. Several species ... grey-headed albatrosses, whose populations are in serious decline at South Georgia, were rare; their ... vulnerability to longlining operations in the South Sandwich Islands may, therefore, be low. Quantitative data ... saving of $A4.9 million and 30 300 albatrosses annually. The Japanese tuna fishery is in the process ... but were 10 mm in diameter. Pieces of the squid Illex argentinus were used for bait, with roughly 20 ... completed in the 1992/93 season, a value for seabird mortality of 2 436 birds/year Seabird Interactions ... thank all those people in Chile and the United Kingdom who assisted in the planning and execution of ...
Science Journal Paper : CCAMLR Science, Volume 1 (CCAMLR Science, Volume 1) : 143–153 : Auteur(s): Ashford, J.R., J.P. Croxall, P.S. Rubilar and C.A. Moreno
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Editorial
Science coincides with the 30th meeting of the CCAMLR Scientific Committee. Over those 30 years, several ... -based decision-making by CCAMLR. One of the most striking changes over the past 30 years is the increase ... the Southern Ocean. In particular there is a suite of papers that address key aspects of improving ... of analysis of data gathered on fishing vessels to using trends in patents to predict the future for ... decision-making by CCAMLR. One of the most striking changes over the past 30 years is the increase in the ... coincides with the 30th meeting of the CCAMLR Scientific Committee. Over those 30 years, several thousand ... . In particular there is a suite of papers that address key aspects of improving assessment of the ... analysis of data gathered on fishing vessels to using trends in patents to predict the future for krill ...
Science Journal Paper : CCAMLR Science, Volume 18 (CCAMLR Science, Volume 18) : 167 : Auteur(s): Editors
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Length-based assessment for mackerel icefish (Champsocephalus gunnari) at South Georgia
(Champsocephalus gunnari) in Subarea 48.3 employs the CCAMLR mixture analysis program (CMIX) and generalised yield ... the given harvest control rule to set a two-year total allowable catch (TAC). One issue is the ... accurate identification of age cohorts from the survey data. In this paper a length-based approach is ... data which, in conjunction with the bootstrapped survey biomass data, yields an estimate of the ... 20 30 40 50 (b) Hillary et al. 134 In equation (6) the ... resultant two-year TAC), will be in a length- not an age-structured paradigm. In such a length-based ... , weight in kg) used in the analyses. Year a b 2006 6e-10 3.004 2007 6e-10 3.400 2008 5.47e-10 3.420 ... τ, there exists a (length) transition matrix Γij, which defines the probability of an animal in ...
Science Journal Paper : CCAMLR Science, Volume 17 (CCAMLR Science, Volume 17) : 129–137 : Auteur(s): Hillary, R.M., C.T.T. Edwards, R.E. Mitchell and D.J. Agnew
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A preliminary investigation of the possible effects of rhizocephalan parasitism on the management of the crab fishery around South Georgia
levels of infection by a rhizocephalan barnacle have been found in the population of the crab Paralomis ... to declines in spawning stock. The effects of harvesting both healthy and infected animals are ... animals from the population. The need is stronger when the population is sensitive to declines in spawning ... stock. Results highlight the importance of incorporating parasitism in the design of a management ... animal is in the size range where the chela has started growing at the higher adult growth rate. Data ... higher level of (constant) natural mortality than uninfected crabs. In each year the number of newly ... . * In each year the number of parasite larvae ('recruits') is proportional to the number of infected ... crabs in the previous year. Once a crab is infected it remains infected. Male crabs are harvested at ...
Science Journal Paper : CCAMLR Science, Volume 1 (CCAMLR Science, Volume 1) : 175–192 : Auteur(s): Basson, M
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Estimating the impact of depredation by killer whales and sperm whales on longline fishing for toothfish (Dissostichus eleginoides) around South Georgia
whales have been more frequently encountered in recent years, occurring in larger pod sizes, whereas ... 3.8% and sperm whales on 17.7% of lines. Killer whales appear in pod sizes normally of 4 to 10 animals ... toothfish, usually depressing CPUE by about 50%. Sperm whales occur in smaller pod sizes, normally between 1 ... and 4 animals, and have a relatively lower impact on catches, depressing CPUE by up to 20%. Sperm ... , followed by two years of low interaction, and finally another year of very high interaction in 20009. The ... where T is the corrected total catch in year y for observed sets, Cy,n is the declared catch in year y ... on observed sets which had no cetacean interactions, Cy,l is the declared catch in year y on ... °S 36.5°W); (b) the five fine-scale rectangles with the highest CPUE in any one year. The results ...
Science Journal Paper : CCAMLR Science, Volume 17 (CCAMLR Science, Volume 17) : 163–178 : Auteur(s): Moir Clark, J. and D.J. Agnew
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Comparison of age readings from scales and otoliths of the Patagonian toothfish (Dissostichus eleginoides) from South Georgia
region (Subarea 48.3). In 44% of specimens, age readings from both structures were identical. A Wilcoxon ... test for paired data (Ts = 0.256, n = 59) conducted on the remaining 56% showed that differences in age ... which relates maximum observed age to natural mortality. In this case we used M = 0.13, which is the ... 24 years. This is very close to the maximum age of 22.8 years calculated from Taylor's formulae ... soaked for one week in a solution of 20% alcohol (96"), 5% glycerin, a few drops of domestic detergent ... , 1992 (SC-CAMLR-SSPI9). CCAMLR, Hobart, Australia: 21-30. (In Spanish) North, A.W. 1988. Age of ... . eleginoides is 223 cm. Sexual maturity is reached at about 90 to 100 cm total length (TL) (9-10 years) in ... about seven years, followed by a period when an increase in thickness is the main result of growth ...
Science Journal Paper : CCAMLR Science, Volume 5 (CCAMLR Science, Volume 5) : 191–203 : Auteur(s): Cassia, M.C
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Acoustic estimates of krill density at South Georgia, 1981 to 1998
from year to year over that time, ranging from ≈ 2 to ≈ 150 g m-2 (fresh mass). The 1982, 1991 and ... separate density estimates for northeastern and northwestern South Georgia, and in four of these seasons ... years; by convention the year given refers to the year in which the season ended) BAS has conducted ... given year is less than p - o for all years, then the year in Acoustic estimates of krill density ... ), four years exhibited greater density in the east. The year deviating from this pattern, 1994, was ... the year in which krill density at the island was the lowest of all years for which data are ...
Science Journal Paper : CCAMLR Science, Volume 6 (CCAMLR Science, Volume 6) : 47–57 : Auteur(s): Brierley, A.S., J.L. Watkins, C. Goss, M.T. Wilkinson and I. Everson
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Estimation of natural mortality using catch-at-age and aged mark-recapture data: a multi-cohort simulation study comparing estimation for a model based on the Baranov equations versus a new mortality equation.
process error in predicted catch-at-age numbers. Simulations assumed 1 000 releases per year over 12 years ... obtained by integrating an ordinary differential equation (ODE) for within-year population dynamics. The ... ; constant catch ODE (CCODE) model uses a new total mortality ODE with constant within-year catch per unit ... perturbation by observational error were also carried out for each model in order to investigate the effect on ... fishing years. In order to apply equations (3) and (4) recursively from the start of fishing at year y ... response random variable is defined as the number of recaptures of ,iy aR in ith year of fishing years ... 12 fishing years starting in calendar year 2010, with this number of fishing years chosen to reflect ... the age-structured population for each fishing year by ‘tracking’ all cohorts in the population over ...
Science Journal Paper : CCAMLR Science, Volume 18 (CCAMLR Science, Volume 18) : 1–27 : Auteur(s): Candy, S.G.
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Using ecosystem monitoring data to detect impacts
an observed value in an unimpacted system, or (ii) the frequency of values below a fixed reference ... point. The second approach allows inference criteria based on changes in this frequency rather than by ... decline in Antarctic fur seal (Arctocephalus gazella) pup production at South Georgia from the early 1990s ... within a few years of its onset, but a fixed reference point method could have provided this sustained ... if at ≤ acrit in two or more years of a four-year refer- ence period. Summary of methods: anomalies ... : Method 4 with inference based on changes in frequency: the observed proportion of years in an n-year ... baseline PDF were then used to test for impacts in 20 more obser- vations drawn from the baseline period ... system. An n-year reference period can be thought of as a series of Bernoulli trials in which the ...
Science Journal Paper : CCAMLR Science, Volume 17 (CCAMLR Science, Volume 17) : 197–212 : Auteur(s): Hill, S.L., J. Forcada, P.N. Trathan and C.M. Waluda