کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
4543001 1626810 2014 6 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Estimation of time-varying selectivity in stock assessments using state-space models
ترجمه فارسی عنوان
ارزیابی انتخابی متغیر زمان در ارزیابی سهام با استفاده از مدل های فضای حالت
موضوعات مرتبط
علوم زیستی و بیوفناوری علوم کشاورزی و بیولوژیک علوم آبزیان
چکیده انگلیسی


• We present a stock assessment model that allows for time-varying fishing selectivity.
• This is obtained via correlated random walk assumptions on F between ages.
• Smoothness selection is objective through ML-estimation of variance parameters.
• The traditional separability assumption is a special case of the proposed model.

Time-varying selectivity is one of the main challenges in single species age-based assessment models. In classical deterministic VPA-type models the fishing mortality rates are unfiltered representations of the observed catches. As a consequence the selectivity becomes time-varying, but this representation is too fluctuating, because it includes the observation noise. In parametric statistical catch at age models a common assumption is that the selectivity is constant in all years, although time-varying selectivity can be introduced by splitting the data period in blocks with different selectivities, or by using smoothing splines and penalized time-deviances. However, these methods require subjective choices w.r.t. the degree of time-varying allowed. A simple state-space assessment model is presented as an alternative, which among other benefits offers an objective way of estimating time-varying selectivity pattern. The fishing mortality rates are considered (possibly correlated) stochastic processes, and the corresponding process variances are estimated within the model. The model is applied to North Sea cod and it is verified from simulations that time-varying selectivity can be estimated.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Fisheries Research - Volume 158, October 2014, Pages 96–101
نویسندگان
, ,