Fisheries Research 97 (2009) 95–102 Contents lists available at ScienceDirect Fisheries Research journal homepage: www.elsevier.com/locate/fishres Research article Selectivity of diamond, hexagonal and square mesh codends for three commercial cephalopods in the Mediterranean Zafer Tosuno˘ glu a,∗ , Celalettin Aydın a , Alp Salman a , Paulo Fonseca b a Ege University, Faculty of Fisheries, 35100 Bornova, Izmir, Turkey b INRB/L-IPIMAR, National Institute of Biological Resources/Laboratory of Fisheries and Sea Research, Ave Brasilia, P-1449006 Lisbon, Portugal article info Article history: Received 4 June 2008 Received in revised form 14 January 2009 Accepted 19 January 2009 Keywords: Codend selectivity Mesh shape Size-selection Bycatch Loligo vulgaris Illex coindetii Sepia orbignyana Aegean Sea Eastern Mediterranean abstract Undersized and immature commercially important cephalopods are often inadvertently caught by trawlers in the eastern Mediterranean. To evaluate the effectiveness of different mesh codends (diamond, hexagonal and square) to reduce bycatch of juvenile commercially important Mediterranean cephalopods (European squid Loligo vulgaris, broadtail shortfin squid Illex coindetii and pink cuttlefish Sepia orbignyana), a series of selectivity experiments was undertaken with a modified bottom trawl. The covered codend technique was used to capture escapees. For the broadtail shortfin squid and the pink cuttlefish, the square-shaped mesh displayed the highest 50% retention lengths (L 50 ) compared to diamond and hexag- onal mesh. For the European squid, selectivity could only be measured by pooling the data from all hauls for each mesh shape. For all three species, the L 50 values of square and hexagonal mesh codends were significantly different (p < 0.01). Beyond the mesh variability, species catch was found to have a significant impact in the selection range of the broadtail shortfin squid. Furthermore, for the cuttlefish, total catch and haul duration likely account for variability of L 50 attributed to mesh configuration. For all species, regardless of the mesh shape, L 50 values were substantially lower than the minimum landing size or length at first maturity. Therefore, the current legal minimum mesh size and codend configurations for demersal trawling are not suitable for the management of these species. As such, sustainability in Mediterranean cephalopod fisheries would profit from more selective gears. This could be achieved both by an increase in codend mesh size and change in codend shape; however, being part of a mixed fishery, when these changes are being practiced, the impact on the fish catches of target species will have to be taken into consideration. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Cephalopods comprise approximately 700 species worldwide and many ecologically important cephalopods have Atlantic origins (Mangold and Boletzky, 1987). Both as direct human consump- tion and as a principal food for top predators (Clarke, 1983), these cephalopods constitute one of the most important dem- ersal fishery resources in the Mediterranean (Worms, 1983). Cephalopod fisheries production in Mediterranean was 53800 t in 2001, constituting 1.6% of the total world cephalopod catch (Jereb and Roper, 2005). Because of the economic and ecological importance of cephalopods, the factors affecting the sustainabil- ity of the cephalopod fisheries of the Mediterranean must be understood. In addition to catches by trammel, fyke nets, seiners, specially designed longlines and hand-jigging, cephalopods also constitute a valuable by-catch in the trawl fishery (Jereb and Roper, 2005). ∗ Corresponding author. Tel.: +90 535 5927692; fax: +90 232 3883685. E-mail address: zafer.tosunoglu@ege.edu.tr (Z. Tosuno˘ glu). However, different Mediterranean nations deal with the by-catch differently. In Turkish waters, codends with a minimum dia- mond mesh size of 44 mm are required for demersal fish trawling (Anonymous, 2006). In contrast, European Union Mediterranean countries are enforcing the use of 40 mm square mesh codends as of 2008 (E.C., 2006). Although a considerable amount of trawl selectiv- ity research has been carried out for finfish and crustacean species in the Mediterranean, selectivity data for commercial cephalopods are only available for the European squid Loligo vulgaris (Ordines et al., 2006) and the broadtail shortfin squid Illex coindetii (Sala et al., 2008). Understanding the size ranges and maturation stages of these species will reveal if mesh shape (and size) are capturing these species at important life stages. Considering the commercial rel- evance of cephalopods and the need for sustainable management, we conducted a preliminary investigation on the codend selectiv- ity of different mesh shape (diamond, hexagonal and square) for the three most important species, the European squid, the broad- tail shortfin squid and the pink cuttlefish Sepia orbignyana. Potential benefits from an improved codend were matched against the length at first maturity (LFM), i.e., the length corresponding to a 50% pro- 0165-7836/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.fishres.2009.01.006