Commit 1fd9d6cf authored by pfreon's avatar pfreon
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Changes in the content of Help files mostly related to stock structure

Major changes related to stock structure after the incorporation of the metatpopulation concept.
parent 27ac284e
Does the data applies to the full metapopulation or at least to one of its sub-stocks
with limited connectivity?
The degree of connectivity between sub-stocks of the metapopulation is to be assessed
to answer this question. Connectivity patterns range from a well-mixed larval pool
(maximal connectivity) at one extreme to a collection of closed self-sustaining populations
(minimal connectivity) at the other. However, most situations are intermediate to these
two extremes (MSC, 2020).
Answer YES if the considered stock exploited by the fleet(s) is either:
1) a full metapopulation with reasonably high connectivity. Note that according to
your previous answers, all these eventual sub-stocks must be exploitedby the fleet(s)
corresponding to your data-set. This case is not in contradiction with the fact that
you answer YES to the question "Does the data-set apply to a unit stock";
2) or if it is only one of its substocks with limited connectivity with
the rest of the metapopulation.
MSC (2020) MSC Guidance to the Fisheries Certification Process v2.2. MSC Document: 89 pp.
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Is the sub-stock considered well isolated (with few exchanges) from
the others ?
Does the data applies to the full metapopulation or at least to one of its sub-stocks
with limited connectivity?
The degree of connectivity between sub-stocks of the metapopulation is to be assessed
to answer this question. Connectivity patterns range from a well-mixed larval pool
(maximal connectivity) at one extreme to a collection of closed self-sustaining populations
(minimal connectivity) at the other. However, most situations are intermediate to these
two extremes (MSC, 2020).
Answer YES if the studied sub-stock has few exchanges with the other
sub-stocks of the area, in terms of migration and recruitment.
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Answer YES if the considered stock exploited by the fleet(s) is either:
1) a full metapopulation with reasonably high connectivity. Note that according to
your previous answers, all these eventual sub-stocks must be exploitedby the fleet(s)
corresponding to your data-set. This case is not in contradiction with the fact that
you answer YES to the question "Does the data-set apply to a unit stock";
2) or if it is only one of its substocks with limited connectivity with
the rest of the metapopulation.
MSC (2020) MSC Guidance to the Fisheries Certification Process v2.2. MSC Document: 89 pp.
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Does the data-set apply to metapopulation?
The concept of metapopulation was first proposed by Levins (1968).
It was then enriched with new ideas and summarised by McQuinn (1997) and
can be defined as : ‘The population structure of many species can be
considered as an array of local populations linked by variable degrees
of gene flow’.
According to Sale et al. (2006), in some cases, stocks may be structured
as “metapopulations” – systems in which local populations (namded sub-
populations or sub-stocks, or components) inhabit discrete habitat patches
and inter-patch dispersal is neither so low as to negate significant demographic
connectivity, nor so high as to eliminate any independence of local population
dynamics.
Levins R (ed.). 1968. Evolution in changing environments. Princeton,
New Jersey: Princeton University Press.
McQuinn IH. 1997. Metapopulations and the Atlantic herring. Reviews
in Fish Biology and Fisheries 7: 297–329.
Sale PF, Hanski I, Kritzer JP (2006). The merging of metapopulation theory and marine ecology: establishing the historical context. In: Kritzer JP, Sale PF (Eds) Marine Metapopulations. Chapter 1. Elsevier, Amsterdam: 3-28
Number of significantly exploited year-classes?
Number of significantly exploited year-classes?
Indicate the number of year-classes significantly exploited by the fishery.
An arbitrary threshold of a contribution to 5% of the catches in weight can be
......
......@@ -5,5 +5,4 @@ Answer YES if you want to use a linear relationship between the CPUE and
the fishing effort. This choice will force the software to choose a Schaefer
model (and then multivariate models of the same family) which would lead to a
more pessimistic management than the exponential models.

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......@@ -2,5 +2,7 @@ Strong instability in the CPUE time-series?
Answer YES if the CPUE time-series presents large fluctuations in a short
time (over 100%, not autocorrelated, providing an erratic aspect of the plot).
This case is in favour of linear production models.
This case is in favour of linear production models (please note that this
question is only partly duplicating a previous question regarding four time
series: "Is interannual variability too strong?").

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Does the data-set apply to a single stock?
Does the data-set apply to a unit stock?
Answer YES if the stock is not subdivided into various geographical
sub-stocks.
From the fisheries management point of view, a unit stock can be defined as
a group of fish that can be treated as a stock and managed as an independent unit,
as long as the results of the assessment and the impact of management measures
do not differ significantly from what they would be in the case of a truly
independent stock (Gulland, 1983, MSC, 2020).
Answer YES if the stock is made of a single species and not subdivided into various
geographical sub-stocks independant from each other.
Gulland, J.A. (1983). Fish stock assessment. A manual of basic methods.
Chichester, John Wiley and Sons, FAO/Wiley series on food and agriculture.
Vol. 1: 223 pp
MSC (2020) MSC Guidance to the Fisheries Certification Process v2.2. MSC Document: 89 pp.
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