Basic HTML Version
Int'l Journal of Marine Science 2012, Vol.2, No.8, 57
-
61
http://ijms.sophiapublisher.com
60
coefficient is a ratio calculated as follow:
(Octopus effort)/(Overall effort)
The use of the coefficient of correction is only
practiced for inshore activities because some of them
are known to be selective for other species than
octopus. For the trawling fishing, the effort is used
without corrections because they are not selective and
able to catch octopus if it is accessible.
3.2 Models
Data are available on the yield and the effort expended
over a sufficient number of years (12 years).
According to Laloe (1995) we cannot give definitive
answer about the number of years may be appropriate,
but Hilborn (2003) outlines that generally, stock
assessments are new developments within the last
10~20 years.
The fishing effort has undergone substantial changes
over the period covered and standardized.
The application of surplus production models permits
to determine the optimum level of effort, which
corresponds to the effort that produces the maximum
yield that can be sustained without affecting long-term
productivity of the stock, the so-called maximum
sustainable yield (MSY), which is estimated from
these input data:
f(i)=effort in year i, i=1,2,...,n
Y/f=yield (catch in weight) per unit of effort in year i
Y/f may be derived from the yield, Y(i), of year i for
the entire fishery and the corresponding effort, f(i), by
Y/f=Y(i)/f(i), i=1,2,...,n
The most common production models are Schaefer
model (linear model, 1954) and Fox model
(exponential model, 1970).
The expressing of yield per unit of effort, Y/f, as a
function of the effort, f, using exponential model is
written as: Y(i)/f(i)=exp[c + d*f(i)] and linear one as
Y(i)/f(i)=a+b*f(i) if f(i)≤a/b
The comparison between coefficient of correlation (R
2
)
for Scheaffer and Fox models allows the choice of the
model with the greatest value to be used in stock
assessment.
Authors’ contributions
KW collected data drafted the manuscript, JC participated in the collection
of data and revised the design of the manuscript and BA participated by
coordination funding of the study. All authors read and approved the final
manuscript.
Acknowledgements
We express our thanks to the Laboratory of Analysis, Treatment and
Valorization of Products and Pollutants of the Environment for supporting
of our work. As we are grateful to agent of DGPA (Direction Générale de la
Pêche et l’Aquaculture) and CRDA (Commissariat Régionale
développement Agricole ) in Monastir to made fishery data available. We
acknowledge also the manuscript improvement by anonymous reviewers
and English improvement by Afifa (ISBM Monastir, Tunisia)
References
Ben Youssef S., 2006, Contribution à l’étude discriminatoire du poulpe
commun (
Octopus vulgaris
. Cuvier, 1797) du golfe de Gabès
(Méditerranée Centrale): analyses biométriques et biochimiques.
Thesis for M.S., Superior Institute of Biotechnologies of Monastir,
University of Monastir, Supervisor: Ezzeddine-Najai S., pp. 117
Boyle P., and Rodhouse P., eds., 2005, Cephalopods: Ecology and Fisheries,
Blackwell Science, Oxford, pp. 452 PMid:16030496
Caddy J.F., eds., 1983, The cephalopods: factors relevant to their population
dynamics and to the assessment and management of stocks, pp.
416–452
COM, 2008, The Role of the CFP in Implementing An Ecosystem Approach
to Marine Management. No. 187, pp. 10
Ezzeddine-Najai S., 1992, Biologie et pêche du poulpe
Octopus vulgaris
Cuvier, 1797 (Céphalopoda, Octopoda) du golfe de Gabès, Bulletin de
l’Institut National des Sciences et Technologies Océanographiques et
de Pêche à Salammbô, 19: 5-19
Ezzeddine-Najai S., and El Abed A., 2004, Potential biological and
environmental influences on the
Octopus vulgaris
population of the
Gulf
of
Gabès
(south-eastern
Tunisian
coast),
GCP/RER/010/ITA/MSM-TD-02, MedSudMed Technical Documents,
2 : 42-47
FAO, 1987, Rapport du 3
ème
groupe de travail ADHOC sur l’évaluation des
stocks de Céphalopodes dans la région nord du COPACE. Rome, FAO.
COPACE/PACE SERIES 86/41, pp. 88
Faure V., Caverivière A., Thiam M., and Jouffre D., eds., 2002,
Environnement et variabilité des populations de poulpes
Octopus
vulgaris
en Afrique de l’Ouest. IRD, Paris, pp. 129 -142
Guerra Á., Allcockb L., and Pereira J., 2010, Cephalopod life history,
ecology and fisheries: An introduction, Fisheries Research, 106:
117–124
http://dx.doi.org/10.1016/j.fishres.2010.09.002
Hermosilla C.A., Rocha F., Fiorito G., Gonzalez Á.F., and Guerra Á., 2010,
Age validation in common octopus
Octopus vulgaris
using stylet
increment analysis, International Council for the Exploration of the Sea
Journal of Marine Science, 67: 1458–1463
Hilborn R., 2003, The state of the art in stock assessment: where we are and
where we are going? Scientia Marina, 67: 15-20
ICES WGCEPH, 2010, International Council for the Exploration of the Seas
Working Group for Cephalopods, Report of the Annual Meeting at
AZTI old in Sukarietta, Spain
Jabeur C., Khoufi W., El Moatamri N., Trigui M., and Bakhrouf A., 2007,