Sex ratio variation in an exploited population of common octopus: ontogenic shifts and spatio-temporal dynamics
- 352 Downloads
Sex ratio is a fundamental demographic parameter with major implications for the dynamics, management, and conservation of animal populations. The objective was to study the main factors affecting the post-settlement population sex ratio (SR) of Octopus vulgaris off the NE Atlantic. We investigated the spatio-temporal dynamics in SR using more than 115,000 individual records obtained from onboard observers over a 14-year period. Generalized linear models were used to evaluate the abiotic and biotic factors affecting the variation in SR. The probability of catching a female decreased with size. Seasonal differences in SR resulted in a female-biased ratio in autumn and male dominance in summer. SR also varied along the bathymetric gradient with larger female proportion at deeper waters in winter and spring. The probability of catching a female was lower in hard substrates mainly in summer. Upwelling intensity and sea surface temperature did not show substantial effects on SR. The analysis neither revealed an influence of local density on SR. The spatio-temporal patterns of SR in O. vulgaris are likely based on differences in sexual behavior and life history which may affect catchability rates. Understanding the causes in SR patterns will provide valuable knowledge for future assessment and management plans.
KeywordsSex ratio Life history Fisheries Octopus vulgaris NE Atlantic
This study is indebted with all the onboard observers that carried out the sampling, and with the UTPB that runs the monitoring program of the artisanal fishery sector in Galician waters. Many thanks to David Villegas-Ríos for reviewing the manuscript and providing general advice and fruitful discussions. This study was financed by the research project CASGASS (http://www.ices.dk/community/icessciencefund/Pages/default.aspx) under the ICES Science Fund program (2014), and also by the Agreement between CSIC and Xunta de Galicia to analyze fisheries-dependent data from the monitoring program of small-scale fisheries in Galicia (Agreement No. 070401150009). Jaime Otero was supported by a “Junta para la Ampliación de Estudios” Fellowship (JAE-Doc programme 2011) from the CSIC and ESF.
Compliance with Ethical Standards
Conflict of interest
The authors declare that they have no conflict of interest and consent was obtained from all participants of the study.
All the animals have been sampled from regular operations of the artisanal fishery under the regional monitoring program of the fishing activity.
- Amor, M. D., M. D. Norman, A. Roura, T. S. Leite, I. G. Gleadall, A. Reid, C. Perales-Raya, C.-C. Lu, C. J. Silvey, E. A. G. Vidal, F. G. Hochberg, X. Zheng & J. M. Strugnell, 2016. Morphological assessment of the Octopus vulgaris species complex evaluated in light of molecular-based phylogenetic inferences. Zoologica Scripta. doi: 10.1111/zsc.12207.Google Scholar
- Arkhipkin, A. I. & D. A. J. Middleton, 2002. Sexual segregation in ontogenetic migrations by the squid Loligo gahi around the Falkland Islands. Bulletin of Marine Science 71: 109–127.Google Scholar
- Bakun, A., 1973. Coastal upwelling indices, west coast of North America, 1946–71 NOAA Technical report. vol NMFS-671. NOAA NMFS-671, 103.Google Scholar
- Bloor, I. S. M., V. J. Wearmouth, S. P. Cotterell, M. J. McHugh, N. E. Humphries, E. L. Jackson, M. J. Attrill & D. W. Sims, 2013. Movements and behaviour of European common cuttlefish Sepia officinalis in English Channel inshore waters: First results from acoustic telemetry. Journal of Experimental Marine Biology and Ecology 448: 19–27.CrossRefGoogle Scholar
- DeMartini, E. E., J. H. Uchiyama & H. A. Williams, 2000. Sexual maturity, sex ratio, and size composition of swordfish, Xiphias gladius, caught by the Hawaii-based pelagic longline fishery. Fishery Bulletin 98: 489–506.Google Scholar
- FAO, 2016. The State of World Fisheries and Aquaculture 2016. Contributing to food security and nutrition for all. Food and Agriculture Organization of the United Nations Fisheries and Aquaculture Department. Fisheries and Aquaculture Department Rome, Italy, 200.Google Scholar
- Fournier, D. A., H. J. Skaug, J. Ancheta, J. Ianelli, A. Magnusson, M. N. Maunder, A. Nielsen & J. Sibert, 2012. AD Model Builder: using automatic differentiation for statistical inference of highly parameterized complex nonlinear models. Optimization Methods and Software 27: 233–249.CrossRefGoogle Scholar
- Fuentes, L. & J. Iglesias, 2010. Release experiments with Octopus vulgaris Cuvier, 1797 in Galicia, NW Spain. First results on recapture rate, distribution. Vie et Milieu 60: 65–71.Google Scholar
- Han, Y.-S. & W.-N. Tzeng, 2006. Use of the sex ratio as a means of resource assessment for the Japanese Eel Anguilla japonica: a case study in the Kaoping river. Taiwan. Zoological Studies 45: 255–263.Google Scholar
- Hanlon, R. T. & J. B. Messenger, 1996. Cephalopod behaviour. Cambridge University Press, Cambrige.Google Scholar
- Hatanaka, H., 1979. Studies on the fisheries biology of common octopus off the northwest coast of Africa. Bulletin Far Seas Fisheries Research Laboratory 17: 13–124.Google Scholar
- Jereb, P., A., L. L. Allcock, E., U. Piatkowski, L. C. Hastie & G. J. Pierce, 2015. Cephalopod Biology and Fisheries in Europe: II. Species Accounts, vol 325, Denmark.Google Scholar
- Kennedy, J. S., 1985. Migration, behavioral and ecological. In Rankin, M. A. (ed.), Migration: Mechanisms and Adaptive Significance, Vol. 27. Contributions in Marine Science, Port Aransas: 5–26.Google Scholar
- Meisel, D., R. Byrne, M. Kuba, U. Griebel & J. Mather, 2003. Circadian rhythms in Octopus vulgaris. Berliner Paläobiol Abh 3: 171–177.Google Scholar
- Morais, P. & F. Daverat, 2016. Definitions and concepts related to fish migration. In Morais, P. & F. Daverat (eds), An introduction to fish migration. CRC Press, Boca Raton, USA: 14–19.Google Scholar
- Otero, J., X. A. Álvarez-Salgado, A. F. González, A. Miranda, S. B. Groom, J. M. Cabanas, G. Casas, B. Wheatley & A. Guerra, 2008. Bottom-up control of common octopus Octopus vulgaris in the Galician upwelling system, northeast Atlantic Ocean. Marine Ecology Progress Series 362: 181–192.CrossRefGoogle Scholar
- Pierce, G. J., L. Allcock, I. Bruno, P. Bustamante, A. González, A. Guerra, P. Jereb, E. Lefkaditou, S. Malham, A. Moreno, J. Pereira, U. Piatkowski, M. Rasero, P. Sánchez, B. Santos, M. Santurtún, S. Seixas & R. Villanueva, 2010. Cephalopod biology and fisheries in Europe, Vol. 303. ICES Cooperative Research Report No, Denmark: 175.Google Scholar
- Plummer, M., N. Best, K. Cowles & K. Vines, 2006. CODA: convergence diagnosis and output analysis for MCMC. R News 6: 7–11.Google Scholar
- R Development Core Team, 2014. R: A Language and Environment for Statistical Computing, Vienna. Austria, R Foundation for Statistical Computing.Google Scholar
- Sakaguchi, H., T. Hamano & A. Nakazono, 2000. Population structure of Octopus vulgaris estimated from catch size Composition in Northeastern Iyo-Nada of the Seto Inland Sea, Japan. Bulletin of the Japanese Society of Fisheries Oceanography 64: 224–234.Google Scholar
- Silva, L., I. Sobrino & F. Ramos, 2002. Reproductive biology of the common octopus, Octopus vulgaris Cuvier, 1797 (Cephalopoda: Octopodidae) in the Gulf of Cádiz (SW Spain). Bulletin of Marine Science 71: 837–850.Google Scholar
- Skaug, H., D. Fournier, B. Bolker, A. Magnusson & A. Nielsen, 2014. Generalized Linear Mixed Models using AD Model Builder. R package version 0.8.0, http://glmmadmb.r-forge.r-project.org/.
- Westermann, G. E. G., 1969. Sexual Dimorphism, migration, and segregation in living Cephalopods. In: Westermann C.E.G., ed. Dimorphism in Fossil Metazoa and Taxonomic Implication. International Palaeontological Union, Committee on Evolution 1: 18-20.Google Scholar