Fisheries Research 96 (2009) 252–258 Contents lists available at ScienceDirect Fisheries Research journal homepage: www.elsevier.com/locate/fishres Time series analysis of flatfish landings in the Portuguese coast Célia M. Teixeira ∗ , Henrique N. Cabral Universidade de Lisboa, Faculdade de Ciências, Centro de Oceanografia, Campo Grande, 1749-016 Lisboa, Portugal article info Article history: Received 4 July 2008 Received in revised form 29 November 2008 Accepted 1 December 2008 Keywords: Flatfish Landings Stock assessment Environmental factors Fisheries management Portugal abstract Flatfish fisheries are widely spread over the Portuguese coast and traditionally have a high social and economical relevance in some coastal communities. The artisanal multi-gear fleet is responsible for the largest share of flatfishes landings. However, only a fraction of these vessels actively target flatfishes, since many other species are caught in these multi-species fisheries. To explain the variability of flatfish landings we used the data set of official landings of commercially important flatfish species (monthly landings values, from 1992 to 2005) and applied generalized linear models (GLM) using the NAO index (NAO), sea surface temperature (SST), scalar wind (WIND), rainfall (RAIN) and month as explanatory variables. Flatfish landings did not showed a common trend for different species group between 1992 and 2005. For the majority of the species, significant relationships were found between month and SST and landings per unit effort (LPUE). The seasonal pattern in LPUE reflected migrations to spawning grounds, when flatfishes concentrate in some areas of the continental shelf and become more vulnerable to fishery. Temporal closures should be implemented for the stocks that evidence overexploitation. More studies focused in species abundance and fishing effort estimation are necessary on Portuguese flatfish fisheries in order to determine the status of stocks and adopt adequate management measures. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Fishing is a traditional and culturally important activity in Por- tugal, being dominated by small fishing vessels (Baeta and Cabral, 2005). Flatfish fisheries are widely spread over the Portuguese coast and traditionally have played and important socio-economic role. Flatfish landings account for less than 4% of all the fish biomass landed in the Portuguese coast. However, the importance of flat- fish fisheries is considerable higher due to the high commercial value of flatfish species, accounting for almost 11% of the economi- cal value of all landings (source: DGPA). The most important species, in terms of landings, are the soles, Solea solea (Linnaeus, 1758), Solea senegalensis Kaup, 1858, and Solea lascaris (Risso, 1810), the bastard sole, Microchirus azevia (Capello, 1868), the flounder, Platichthys flesus (Linnaeus, 1758), the spotted flounder, Citharus linguatula (Linnaeus, 1758), the wedge sole, Dicologlossa cuneata (Moreau, 1881), the turbot, Scophthalmus maximus (Linnaeus, 1758), the brill, Scophtahlmus rhombus (Linnaeus, 1758), and the megrims, Lepidorhombus boscii (Risso, 1810) and Lepidorhombus whiffiagonis (Walbaum, 1792). The artisanal multi-gears fleet is responsible for the largest share of flatfishes landings. However, only a fraction of these vessels actively target flatfishes, since many other species are caught in this multi-species fishery. The main fishing gears used in flatfish fisheries are trammel and gill nets and bottom trawl. ∗ Corresponding author. Tel.: +351 217 500 826; fax: +351 217 500 207. E-mail address: cmteixeira@fc.ul.pt (C.M. Teixeira). Regular fluctuations in the stocks and catches of abundant fish species have been documented in many of the world’s oceans (e.g. Cushing, 1996; Klyashtorin, 1998; Ménard et al., 2007). Climatic oscillations, anomalies or changes clearly affect population dynam- ics and several ecological processes in marine ecosystems (e.g. Walther et al., 2002; Stenseth et al., 2004; Duffy-Anderson et al., 2005). The wind regime (e.g. Schwartzlose et al., 1999; Borges et al., 2003) and changes in sea surface temperature (e.g. Fox et al., 2000; Zuur and Pierce, 2004; Désaunay et al., 2006) play a key role in the ecological effects of climate fluctuations. But variations in popula- tion abundance are very often associated with large-scale climate indices such as the North Atlantic Oscillation (NAO) or the Southern Oscillation Index (SOI) (Ottersen et al., 2001; Stenseth et al., 2004). They do not have necessarily a strong link with local weather con- dition (Stenseth et al., 2003), but they can be good predictors of ecological processes (Hallett et al., 2004). The main aim of this work is to analyse the main trends in com- mercial flatfish landings in the Portuguese coast, their relationships with key environmental factors and to evaluate possible implica- tions for the management of these resources. 2. Material and methods 2.1. Data source The data set use in this study was composed of LPUE monthly data, by flatfish species group, from 1992 to 2005, obtained from 0165-7836/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.fishres.2008.12.004