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Estimates of historic changes in total mortality and selectivity for Eastern Atlantic skipjack (Katsuwonus pelamis)from length composition data

Published online by Cambridge University Press:  07 October 2009

Daniel Gaertner
Daniel Gaertner*
Affiliation:
UMR EME, Institut de Recherche pour le Développement (IRD) CRH, BP 171, 34203 Sète Cedex, France
*
[email protected]
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Abstract

Catch-at-size data of the eastern Atlantic skipjack were used to estimate changes in total mortality from 1969 to 2007. We used a transitional model of mean length that generalized the Beverton-Holt mortality estimator to allow change in mortality rate under nonequilibrium conditions. Then, from homogeneous periods of time, length-converted catch curves were used to access qualitative changes in selectivity patterns for two surface fisheries (the baitboat fishery operating from Dakar, Senegal, and the European and associated purse seine fisheries). To explore the impact of catch on the mortality rate, a Bayesian change-point analysis was conducted on the catch time series to detect concomitant variation between mortality rates and catch. Finally, potential causes of these changes are discussed in relation to the implementation of new fishing technology, such fish aggregating devices (FAD). The general pattern depicted by total mortality is in agreement with previous knowledge on this fishery: a state of complete or practically complete exploitation during the nineties followed by the decrease in nominal purse seine fishing effort in the last decade, combined with the effect of a seasonal moratorium on FAD fishing operations. There was no evidence of a change in selectivity between the two contrasted periods of time considered: 1969-1979 and 1986-1999; the second period being characterized by the introduction of new technology onboard vessels. In contrast, the covariation over time between total catch and mortality rate three years later highlights the effect of the fishing pressure on the stock of eastern Atlantic skipjack.

Keywords

Skipjack tunaMortality rateFADFishing strategiesBayesian change-point analysis
Type
Research Article
Information
Aquatic Living Resources , Volume 23 , Issue 1 , January 2010 , pp. 3 - 11
Copyright
© EDP Sciences, IFREMER, IRD, 2009

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References

Ariz J., Delgado A., Fonteneau A., Gonzalez Costas F., Pallares P., 1999, Logs and tunas in the eastern Tropical Atlantic. A review of present knowledge and uncertainties. In: Scott M.D., Bayliff W.H., Lennert-Cody C.E., Schaefer K.M. (Eds.). Proc. International Workshop on fishing for tunas associated with floating objects, La Jolla, CA, February 11–13, 1992. Inter-Am. Trop. Tuna Comm., Spec. Rep. 11 21–65.
Bannerman P.O., Bard F.-X., 2001, Recent changes in exploitation patterns of tunas in the Ghanaian fishery and their effects on commercial catch at size. Col. Vol. Sci. Pap. ICCAT 52, pp. 466-479
Bard F.-X., Antoine L., 1986, Croissance du listao (Katsuwonus pelamis) dans l'Atlantique est. In: Symons PEK, Miyake PM, Sakagawa GT (Eds.). Proc. ICCAT Conf. Int. Skipjack Year Prog. ICCAT Madrid, pp. 301–308.
Barry, D., Hartigan, J.A., 1993, A Bayesian analysis for change point problems. J. Am. Stat. Assoc. 88, 309–319.
Beverton, R.J.H., Holt, S.J., 1956, A review of methods for estimating mortality rates in exploited fish populations with special reference to sources of bias in catch sampling. Rapp. P.-V. Réun. CIEM 140, 67–83.
Burnham K.P., Anderson D.R., 2002, Model selection and inference: a practical information-theoretic approach, 2nd edition. Springer-Verlag, New York.
Cayré P., Farrugio H., 1986, Biologie de la reproduction du listao (Katsuwonus pelamis) de l'océan Atlantique. In: Symons, P.E.K., Miyake, P.M., Sakagawa, G.T. (Eds.), Proc. ICCAT conference on the international skipjack year program, Madrid, pp. 252–272.
Chassot E., Amande M.J., Chavance P., Pianet R., Dédo R.G., 2008, A preliminary attempt to estimate tuna discards and by-catch in the French purse seine fishery of the eastern Atlantic Ocean. ICCAT Sci. doc. SCRS/2008/117.
Erdman, C., Emerson, W.J., 2007, bcp: An R package for performing a Bayesian analysis of change point problems. J. Stat. Software 23, 1-13, http://www.jstatsoft.org/ CrossRef
Fonteneau, A., Diouf, T., 1994, An efficient way of bait-fishing for tunas recently developed in Senegal. Aquat. Living Resour. 7, 139–151. CrossRef
Fonteneau A., Gaertner D., Nordstrom V., 1999, An overview of problems in the catch per unit of effort and abundance relationship for the tropical purse seine fisheries. Col. Vol. Sci. Pap. ICCAT 49, pp. 258–278.
Gaertner D., Ariz J., Hallier J.P., Herrera Armas M.A., 2000, Le point de vue des pêcheurs thoniers à la senne sur l'augmentation des prises de patudo dans l'Atlantique Est et sur les conditions d'utilisation du sonar. Col. Vol. Sci. Pap. ICCAT 51, pp. 553–570.
Gaertner, D., Bard, F.-X., Hallier, J.-P., 2006, Are natural and fishing mortalities comparable from tropical tunas? A multispecies approach with tagging data. Col. Vol. Sci. Pap. ICCAT 59, 421–430.
Gaertner, D., Delgado de Molina, A., Ariz, J., Pianet, R., Hallier, J.-P., 2008, Variability of the growth parameters of the skipjack tuna (Katsuwonus pelamis) among areas in the eastern Atlantic: analysis from tagging data within a meta-analysis approach. Aquat. Living Resour. 21, 349–356. CrossRef
Gaertner, D., Fonteneau, A., Laloë, F., 2001, Approximate estimate of the maximum sustainable yield from catch data without detailed effort information: application to tuna fisheries. Aquat. Living Resour. 14, 1–9. CrossRef
Gaertner, D., Laloe, F., 1986, Etude biométrique de la taille à première maturité sexuelle de Geryon maritae Manning et Holthuis, 1981 du Sénégal. Oceanol. Acta 9, 479–487.
Gaertner D., Pallares P., 2002, The European Union Research Project, Efficiency of Tuna Purse-Seiners and Effective Effort (ESTHER): Scientific report of project. SCTB15, Working Paper FTWG-3.
Gedamke, T., Hoenig, J. M., 2006, Estimating mortality from mean length data in nonequilibrium situations, with application to the assessment of goosefish. Trans. Am. Fish. Soc. 135, 476–487. CrossRef
Goujon M., Labaisse-Bodilis C., 2001, Effets des plans de protection des thonidés de l'Atlantique depuis 1997 d'après les observations faites sur les thoniers senneurs gérés par les armements Français. Col. Vol. Sci. Pap. ICCAT 52, pp. 575–589.
Hallier, J.-P., Gaertner, D., 2008, Drifting fish aggregation devices could act as an ecological trap for tropical tunas. Mar. Ecol. Prog. Ser. 353, 255–264. CrossRef
Hervé A., Bard F.X., Gonzalez Costas F., 1991, Facteurs d'accroissement potentiels de la puissance de pêche des senneurs tropicaux français et espagnols entre 1985 et 1989. Col. Vol. Sci. Pap. ICCAT 35, pp. 8–13.
Itano D., 2003, Documentation and classification of fishing gear and technology on board tuna purse seine vessels. SCTB16 Working Paper FTWG–3.
Moreno, G., Dagorn, L., Sancho, G., Garcia, D., Itano, D., 2007, Using local ecological knowledge (LEK) to provide insight on the tuna purse seine fleets of the Indian Ocean useful for management. Aquat. Living Resour. 20, 367–376. CrossRef
Morón J., Areso J., Pallarés P. 2001, Statistics and technical information about the Spanish purse-seine fleet in the Pacific. 14th Standing Committee on Tuna and Billfish, Working Paper FTWG-11.
Pianet R., Norström V., Dewals P., Delgado A., Ariz J., Saralde R., Gnegoury Dédo R., Diatta, Y., 2008, Statistiques de la pêcherie thonière européenne et assimilée durant la période 1991-2006. Col. Vol. Sci. Pap. ICCAT 62, pp. 289–314.
Restrepo V.R., Ortiz de Urbina J., Fromentin J.-M., Arrizabalaga H., 2007, Estimates of selectivity from eastern Atlantic bluefin tuna from catch curves. Col. Vol. Sci. Pap. ICCAT 60, pp. 937–948.
Sparre P., Ursin E., Venema S.C., 1989, Introduction to tropical fish stock assessment. Part 1 Manual, FAO Fish. Tech. Pap. N° 306.1, Rome FAO.
Ssentongo, G.W., Larkin, P.A., 1973, Some simple methods for estimating mortality rates of exploited fish populations. J. Fish. Res. Board Can. 30, 695-698. CrossRef