1 ASSESSMENT OF THE MEDITERRANEAN SWORDFISH BASED ON THE ITALIAN HARPOON FISHERY DATA Teresa Romeo, Francesco Ferretti, Pierpaolo Consoli, Simone Canese, Franco Andaloro Contact Authors: Teresa Romeo; ISPRA High Institute for Protection and Environmental Research, STS Palermo, Laboratory of Milazzo, Via dei Mille 44, Milazzo (ME), ITALY; phone: +390909224872; fax: +390909241832; email:t.romeo@icram.org Abstract The Mediterranean Sea has a millenarian history of exploitation. Today most of its stocks are overexploited with large predators at extremely low levels of population abundance. For the Mediterranean swordfish (Xiphias gladius), historical and recent status of population abundance are quite uncertain due to the lack of standardized fishery data. Catch statistics are available from few countries despite the species is targeted by a large international long-line fleet. In the Strait of Messina, swordfish is also target of a traditional small-scale harpoon fishery whose catch and effort data are available since 1976 in a systematic fashion. By using generalized linear models (GLM) and their extensions, we analyzed catches registered in harpoon fishers’ logbooks to detect long-term trends of swordfish population abundance. Data were available in different formats, from daily catches with information on fishing position, date, time, fishing vessel, to aggregated annual landings. Accordingly, we carried out multiple analyses with different probabilistic strategies within the GLM framework. Both aggregated and more detailed data were able to show a significant decline of swordfish in the last 30 years. Nonetheless, there is evidence of a recent recovery. We will discuss causes and implications of the observed patterns, and the importance of small-scale fisheries to detect dynamics of fish populations in the absence of conventional data. Introduction The Mediterranean Sea has a millenarian history of exploitation. Today most of its stocks are overex-ploited with large predators at extremely low levels of population abundance (Tudela et al., 2005; Ferretti et al., 2008). Swordfish, Xiphias gladius (Linnaeus 1758), is a large pelagic predator characteristic of oceanic waters, occasionally found close to the coasts. It is a migratory fish with a worldwide distribution in tropical, subtropical and temperate oceans, including the Mediterranean Sea (Palko et al., 1981). Here the species is represented by a single population distinct from those of the of Atlantic Ocean (De Metrio et al., 1989; Kotulas et al., 1995; Di Natale at al., 1996; Tserpes and Tsmenides, 1995; Pujolar et al., 2002; Canese et al., 2007) with a little genetic exchange (Magoulas et al., 1993; Kotoulas et al., 1995; Alvarado Bremer et al., 1999). In the Mediterranean sea swordfish has been object of target fishing at least since Roman time. Today it is being targeted all over the basin by a large international fleet, mainly with long- lines (47% of the total catch, ICCAT, 2004) and driftnets (ICCAT, 2007), though the latter has been banned by the European community in 2002 for its high impact on by-catch species (Silvani et al., 1999; Rogan and Mackey, 2007). The biggest producers of swordfish (1997- 2001) are Italy (44%), Morocco (23%), Greece (10%), and Spain (9%). Catch and effort statistics are uncertain, being available from few countries and very discontinuous in time and ICES CM 2008/K:16