Assessing changes in size at maturity for the European hake (Merluccius merluccius) in Atlantic Iberian waters




North Atlantic Oscillation, life history, reproductive traits, relative condition factor, southern European stock


European hake (Merluccius merluccius) is a commercially important resource in Iberian Atlantic waters. Despite the recovery plan implemented in 2006 and the multiannual management plan for western waters, fishing mortality is still higher than that corresponding to the maximum sustainable yield for the southern European hake stock. The biological processes underlying the dynamics of this stock and its life history traits are essential for assessing population productivity and resilience, making them basic information for management. We analysed the temporal variability of size at maturity (L50) of this species and the main factors influencing it in Atlantic Iberian waters from 1982 to 2019. The annual variability of L50 for each sex was modelled with generalized additive models, considering explanatory environmental variables (Atlantic Multidecadal Oscillation, North Atlantic Oscillation and sea surface temperature) and biological variables (biomass, spawning biomass at length and relative condition factor). The results showed that the L50 of males decreased by a total of 12.9 cm and L50 of females decreased by a total of 10.9 cm from 1982 to 2019. For females the significant explanatory variables were year, spawning biomass at length, biomass and the North Atlantic Oscillation, while for males only year was an explanatory variable. These results are important for understanding the status of the European hake population, signalling that L50 is a good indicator for predicting future population dynamics.


Download data is not yet available.


Albo-Puigserver M., Pennino M.G., Bellido J.M., et al. 2021. Changes in life history traits of small pelagic fish in the western Mediterranean Sea. Front. Mar. Sci. 8: 1197.

Ali M., Nicieza A., Wootton R.J. 2003. Compensatory growth in fishes: a response to growth depression. Fish. Fish. 4: 147-190.

Ashton W.D. 1972. The logit transformation with special reference to its uses in bioassay. Haffner Publishing Co., INC., New York, 88 pp.

Barot S, Heino M, O'Brien L, Dieckmann U. 2004. Estimating reaction norms for age and size at maturation when age at first reproduction is unknown. Evol. Ecol. Res. 6: 659-678.

Cerviño S., Domínguez R., Jardim E., et al. 2013. Impact of egg production and stock structure on MSY reference points. Implications for Southern hake management. Fish. Res. 138: 168-178.

Dalgleish H.J., Koons D.N., Adler P.B. 2010. Can life-history traits predict the response of populations to changes in climate variability? J. Ecol. 98: 209-217.

Dominguez-Petit R. 2007. Study of reproductive potential of Merluccius merluccius in the Galician shelf. Doctoral Thesis. University of Vigo, Spain.

Dominguez-Petit R., Korta M., Saborido-Rey F., et al. 2008. Changes in size at maturity of European hake Atlantic populations in relation with stock structure and environmental regimes. J. Mar. Syst. 71: 260-278.

Dominguez-Petit R., García-Fernandez C., Leonarduzzi E., et al. 2022. Parental effects and reproductive potential of fish and marine invertebrates: Cross-generational impact of environmental experiences. In: Domínguez-Petit R. (ed). Impact of Environmental Stress on Reproductive Processes of Aquatic Animals. Fishes 7: 188.

Drinkwater K.F. 2005. The response of Atlantic cod (Gadus morhua) to future climate change. ICES J. Mar. Sci. 62: 1327-1337.

Engelhard G.H., Heino M. 2004. Maturity changes in Norwegian spring spawning herring Clupea harengus: compensatory or evolutionary responses? Mar. Ecol. Prog. Ser. 272: 245-256.

Fox J., Weisberg S. 2019. An R Companion to Applied Regression (Third). SAGE Publications Inc, pp. 608.

Godø O.R., Haug T. 1999. Growth rate and sexual maturity in cod (Gadus morhua) and Atlantic halibut (Hippoglosus hippoglossus). J. Northwest Atl. Fish. Sci. 25: 115-123.

Goikoetxea N., Irigoien X. 2013. Links between the recruitment success of northern European hake (Merluccius merluccius L.) and a regime shift on the NE Atlantic continental shelf. Fish. Oceanogr. 22: 459-476.

Greene C.H., Pershing A.J. 2000. The response of Calanus finmarchicus populations to climate variability in the Northwest Atlantic: basin-scale forcing associated with the North Atlantic Oscillation. ICES J. Mar. Sci. 57: 1536-1544.

Haug T., Tjemsland T. 1986. Changes in size and age distribution and age at sexual maturity in Atlantic Halibut, Hippoglossus hippoglossus, caught in North Norwegian waters. Fish. Res. 4: 145-155.

Hidalgo M., Rouyer T., Bartolino V., et al. 2012. Context-dependent interplays between truncated demographies and climate variation shape the population growth rate of a harvested species. Ecography 35: 637-649.

Hidalgo M., Rouyer T., Molinero J.C., et al. 2014. Contrasting evolutionary demography induced by fishing: The role of adaptive phenotypic plasticity. Ecol. App. 24:1101-1114. PMid:25154099

Hixon M.A., Johnson D.W., Sogard S.M. 2014. BOFFFFs: on the importance of conserving old-growth age structure in fishery populations. ICES J. Mar. Sci. 71: 2171-2185.

Hjermann D.Ø., Stenseth N.C., Ottersen G. 2004. Indirect climatic forcing of the Barents Sea capelin: a cohort effect. Mar. Ecol. Prog. Ser. 273: 229-238.

Hobday A.J., Smith A.D.M., Stobutzki I.C., et al. 2011. Ecological risk assessment for the effects of fishing. Fish Res. 108: 372-384.

Hollins J., Thambithurai D., Koeck B., et al. 2018. A physiological perspective on fisheries-induced evolution. Evol. Appl. 11: 561-576. PMid:29875803 PMCid:PMC5978952

ICES. 2019. Working Group for the Bay of Biscay and the Iberian Waters Ecoregion (WGBIE). ICES Sci. Rep. 1:31.

ICES. 2021. Working Group for the Bay of Biscay and the Iberian Waters Ecoregion (WGBIE).ICES Sci. Rep. 3:48.

Jørgensen C., Enberg K., Dunlop E.S., et al. 2007. Ecology: Managing Evolving Fish Stocks. Sci. 318: 1247-1248. PMid:18033868

Junquera S., Roman E., Paz X., Ramilo G. 1999. Changes in Greenland halibut growth, condition and fecundity in the Northwest Atlantic (Flemish Pass, Flemish Cap and southern Grand Banks). Variations in maturation, growth, condition and spawning stock biomass production in groundfish. J. Northwest Atl. Fish. Sci. 25: 17-28.

Kell L.T., Pilling G.M., O'Brien C.M. 2005. Implications of the climate change for the management of North Sea cod (Gadus morhua). ICES J. Mar. Sci. 62: 1483-149.

Korta M., Domínguez-Petit R., Murua H., Saborido-Rey F. 2010. Regional variability in reproductive traits of European hake Merluccius merluccius L. populations. Fish. Res. 104: 64-72.

Korta M., García, D., Santurtún M., et al. 2015. "European Hake (Merluccius merluccius) in the North-east Atlantic," in Hakes: biology and Explotation, ed. H. Arancibia (Hoboken: John Wiley & Sons, Ltd), 1-37.

Köster F.W., Möllmann C. Hinrichsen H.H., et al. 2005. Baltic cod Recruitment - the impact of climate variability on key processes. ICES J. Mar. Sci. 62: 1408-1425.

Law R. 2000. Fishing, selection, and phenotypic evolution. ICES J. Mar. Sci. 57: 659-668.

Le Cren E.D. 1951. The length-weight relationship and seasonal cycle in gonad weight and condition in the perch. J. Anim. Ecol. 2: 201-219.

Liermann M., Hilborn R. 2001. Depensation: evidence, models and implications. Fish. Fish. 2: 33-58.

Lorenzen K., Camp E.V. 2019. Density-dependence in the life history of fishes: when is a fish recruited?. Fish. Res. 217: 5-10.

Marshall S., Elliott M. 1998. Environmental influences on the fish assemblage of the Humber estuary. U.K. Estuar. Coast. Shelf Sci. 46:175-184.

Marteinsdottir G., Begg G.A. 2002. Essential relationships incorporating the influence of age, size and condition on variables required for estimation of reproductive potential in Atlantic cod Gadus morhua. Mar. Ecol. Prog. Ser. 235:235-256.

Meiners-Mandujano C.G. 2007. Importancia de la variabilidad climática en las pesquerías y biología de la merluza europea Merluccius merluccius (Linnaeus, 1758) de la costa Noroccidental Africana. PH.D. Thesis. Universitat Politècnica de Catalunya (UPC) (Spain). 207 pp.

Moritz S., Bartz-Beielstein T. 2017. Imputets: Time Series Missing Value Imputation in R. R J. 9: 207-218.

Murua H. 2010. The biology and fisheries of European hake, Merluccius merluccius, in the north-east Atlantic. Adv. Mar. Biol. 58: 97-154. PMid:20959157

Nye J.A., Link J.S., Hare J.A., Overholtz W.J. 2009. Changing spatial distribution of fish stocks in relation to climate and population size on the Northeast United States continental shelf. Mar. Ecol. Prog. Ser. 393, 111-129.

Nye J. A., Baker M.R., Bell R., et al. 2014. Ecosystem effects of the Atlantic Multidecadal Oscillation. J. Mar. Syst. 133, 103-116.

Öckinger E., Schweiger O., Crist T.O., et al. 2010 Life-history traits predict species responses to habitat area and isolation: a cross-continental synthesis. Ecol. Lett. 13: 969-979. PMid:20482577

Olsen E.M., Heino M., Lilly G.R., et al. 2004. Maturation trends indicative of rapid evolution preceded the collapse of northern cod. Nature. 428: 932-935. PMid:15118724

Olsen EM, Lilly GR, Heino M, et al. 2005. Assessing changes in age and size at maturation in collapsing populations of Atlantic cod (Gadus morhua). Can. J. Fish. Aquat. Sci. 62:811-823.

Ottersen G., Planque B., Belgrano A., et al. 2001. Ecological effects of the North Atlantic Oscillation. Oecologia. 128: 1-14. PMid:28547079

Oven L.S. 2004. Resorption of Vitellogenous Oocytes as an Indicator of the State of the Black Sea Fish Populations and Their Environment. Journal of Ichthyology, 44: 115-119.

Pepin P. 2015. Reconsidering the impossible - linking environmental drivers to growth, mortality, and recruitment of fish. Can. J. Fish. Aquat. Sci. 73: 205-215.

R Core Team. 2021. R: A language and environment for statistical computing. R Foundation for Statistical Computing, Version 4.1.2. Vienna, Austria.

Sullivan M.C., Cowen R.K., Steves B.P. 2005. Evidence for atmosphere-ocean forcing of yellowtail flounder (Limanda ferruginea) recruitment in the Middle Atlantic Bight. Fish Oceanogr. 14: 386-399.

Torrejón-Magallanes E.J.2020. sizeMat: Estimate Size at Sexual Maturity. R package version 1.1.2.

Trippel E.A. 1995. Age at maturity as a stress indicator in fisheries. Bioscience. 45:759-771.

Trippel E.A., Kjesbu O.S., Solemdal P. 1997. Effects of adult age and size structure on reproductive output in marine fishes. In Chambers R.C., Trippel E.A. (eds), Early life history and recruitment in fish populations. Chapman and Hall, London, U.K, pp. 31-62.

Wei T., Simko V., Levy M., et al. 2017. Package 'corrplot'. J. Am. Stat. 56: 316-324.

Wood S.N. 2006. Generalized Additive Models: An Introduction with R. Chapman & Hall/CRC. Series: Chapman & Hall/CRC. Texts in Statistical Science.

Wood S.N. 2011. Mgcv: GAMs with GCV/AIC/REML smoothness estimation and GAMMs by REML/PQL.

Wood S.N. 2017. Generalized Additive Models: An Introduction with R (2nd edition). Chapman and Hall/CRC, New York, 496 pp.

Zuur A.F., Ieno E.N., Elphick C.S. 2010. A protocol for data exploration to avoid common statistical problems. Methods. Ecol. Evol.1: 3-14.



How to Cite

Lojo D, Cousido-Rocha M, Cerviño S, Dominguez-Petit R, Sainza M, Pennino MG. Assessing changes in size at maturity for the European hake (Merluccius merluccius) in Atlantic Iberian waters. Sci. mar. [Internet]. 2022Dec.14 [cited 2024Apr.20];86(4):e046. Available from:




Funding data

Ministerio de Ciencia, Innovación y Universidades
Grant numbers RTI2018-099868-B-I00

Most read articles by the same author(s)