Charla IRSE 09/05/2023 Maria Souto - 11:30h PT (12:30h CET)
Marta Rufino
Este jueves (quinta feira) un poquito antes de la comida (almoço), Maria Soto nos va hablar de su trabajo.
Así seguimos con las palestras del ‘Iberian Research of Statistics in Ecology’ (IRSE) para hablarnos un poquito de lo que estamos haciendo en este canto del mundo Ibérico,
(esta charla será en formato on-line apenas).
Hasta jueves,
Marta y Maria Grazia
El link para el evento:
https://videoconf-colibri.zoom.us/j/91404148973?pwd=THBLL2xjeFlsRU5RSy9jdHY4UFljUT09
Meeting ID: 914 0414 8973
Password: 583275
09/05/2023 Maria Souto - 11:30h PT (12:30h CET)
Effects of misreporting landings, discards, and Catch Per Unit of Effort index in state-space production models: the case of black hake in northwest Africa
Recently various state-space implementations of Surplus Production Models (SPMs) have been developed for data-limited stocks. Often, catches and fishing effort are underestimated and discards ignored. This results in biased estimates of stock status and reference points. Therefore, we conduct a sensitivity analysis for different under-reporting scenarios (due to non-declared landings, by-catch and discards) on model estimates and thus advice for the black hake species in North West Africa. Two modelling frameworks were used, namely a stochastic surplus production model in continuous time (SPiCT) and Just Another Bayesian Biomass Assessment (JABBA). A common set of diagnostics was developed to allow comparison across modelling frameworks. Scenarios correspond to hypothesis about misreporting, and assumptions and priors which were kept consistent. The ratio of current fishing mortality over the fishing pressure that gives the maximum sustainable yield, F/FMSY, is most affected by under-reporting. Results are sensitive to the prior assumed for the initial depletion level, B0/K, and research is needed. If the misreporting is changing over time, relative quantities (e.g. F/FMSY) and trends are biased, while if misreporting (or at least a part of misreporting) is constant relative quantities are unbiased. Therefore, the nature of any trend in misreporting should be investigated.
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Portuguese Institute for the Sea and the Atmosphere (IPMA)
Centre of Statistics and its Applications (CEAUL)
Faculty of Sciences, Univ. of Lisbon, Portugal
Marta Rufino
Este jueves (quinta feira) un poquito antes de la comida (almoço), Maria Soto nos va hablar de su trabajo.
Así seguimos con las palestras del ‘Iberian Research of Statistics in Ecology’ (IRSE) para hablarnos un poquito de lo que estamos haciendo en este canto del mundo Ibérico,
(esta charla será en formato on-line apenas).
Hasta jueves,
Marta y Maria Grazia
El link para el evento:
https://videoconf-colibri.zoom.us/j/91404148973?pwd=THBLL2xjeFlsRU5RSy9jdHY4UFljUT09
Meeting ID: 914 0414 8973
Password: 583275
11/05/2023 Maria Souto - 11:30h PT (12:30h CET)
Effects of misreporting landings, discards, and Catch Per Unit of Effort index in state-space production models: the case of black hake in northwest Africa
Recently various state-space implementations of Surplus Production Models (SPMs) have been developed for data-limited stocks. Often, catches and fishing effort are underestimated and discards ignored. This results in biased estimates of stock status and reference points. Therefore, we conduct a sensitivity analysis for different under-reporting scenarios (due to non-declared landings, by-catch and discards) on model estimates and thus advice for the black hake species in North West Africa. Two modelling frameworks were used, namely a stochastic surplus production model in continuous time (SPiCT) and Just Another Bayesian Biomass Assessment (JABBA). A common set of diagnostics was developed to allow comparison across modelling frameworks. Scenarios correspond to hypothesis about misreporting, and assumptions and priors which were kept consistent. The ratio of current fishing mortality over the fishing pressure that gives the maximum sustainable yield, F/FMSY, is most affected by under-reporting. Results are sensitive to the prior assumed for the initial depletion level, B0/K, and research is needed. If the misreporting is changing over time, relative quantities (e.g. F/FMSY) and trends are biased, while if misreporting (or at least a part of misreporting) is constant relative quantities are unbiased. Therefore, the nature of any trend in misreporting should be investigated.