J Appl Ichthyol. 2017;1–4. wileyonlinelibrary.com/journal/jai | 1 © 2017 Blackwell Verlag GmbH Received: 15 May 2017 | Accepted: 4 July 2017 DOI: 10.1111/jai.13459 ORIGINAL ARTICLE Weight-length relationships of 3 demersal fish species from Lebanese marine waters, eastern Mediterranean S. Lelli 1,2,3,4 | M. Lteif 1 | S. Jemaa 1 | G. Khalaf 1 | M. Verdoit-Jarraya 2,3,4 1 Lebanese National Council for Scientific Research – National Center for Marine Sciences (CNRS-L/CNSM), Batroun, Lebanon 2 Centre de Formation et de Recherche sur les Environnements Méditerranéens, UMR 5110, Université de Perpignan Via Domitia, Perpignan, France 3 UMR 5110, CNRS, Centre de Formation et de Recherche sur les Environnements Méditerranéens, Perpignan, France 4 Centre de Recherche sur les Ecosystèmes Marins (CREM), Port-Barcarès, France Correspondence Stefano Lelli, National Center for Marine Sciences (CNRS-L/CNSM), Batroun, Lebanon. Email: stefano.lelli@cnrs.edu.lb Funding information Italian Ministry of Foreign Affairs and International Cooperation; Grant Research Programme of the CNRS-L Summary Weight-length relationships (WLRs) were estimated for 3 demersal species, from the Lebanese marine waters, eastern Mediterranean, namely Coelorinchus caelorhincus (Risso, 1810), Scorpaena elongata Cadenat, 1943 and Stephanolepsis diaspros Fraser- Brunner, 1940. The specimens were collected using trammel and gill nets from June 2012 to October 2014. The values of parameter b of the WLRs W = aL b ranged from 2.922 to 3.708. Pronounced sexual dimorphism in WLR was observed for S. diaspros and none showed a WLR-based geographical pattern of distribution. WLRs reported in this study should be applied only within the observed length ranges. 1 | INTRODUCTION Length and weight data are useful in fisheries management and stan- dard results of fish sampling programs. Weight–length relationships (WLRs) are used for estimating the weight corresponding to a given length, and condition factors are used for comparing the condition, fatness, or well-being (Tesch, 1968) of fish, based on the assumption that heavier fish of a given length are in better condition. Both con- cepts have been used in fisheries research since the beginning of the 20th century (Froese, 2006). WLRs are only known for a restricted number of species, which hampers efforts to model aquatic ecosys- tems. On the one hand WLRs are used to predict the weight from the length of a fish, which is particularly useful for computing the biomass of a sample of fish from the length-frequency of that sample. On the other, WLR for a given population can be compared to average param- eters taken from other regions, in different years in order to identify the relative condition or robustness of the population (Le Cren, 1951). Hence, WLR is considered an important tool in fisheries management (Froese, Tsikliras, & Stergiou, 2011). Eastern Mediterranean halieutic species are poorly studied and very little biological information is available, notably for most of the commercially relevant species. There is an urgent need to manage and regulate small-scale coastal fisheries in the region to ensure the long- term sustainability of fishery resources, and this requires basic popu- lation dynamics information for the target species (Santos, Hawkins, Monteiro, Alves, & Isidro, 1995). In this paper, WLRs were estimated for 3 coastal species, i.e. Coelorinchus caelorhincus (Risso, 1810), Scorpaena elongata, Cadenat 1943, Stephanolepsis diaspros Fraser-Brunner, 1940. We are providing wider size ranges than those found in science literature and to the best of our knowledge, this study presents the first estimation of WLRs for S. elongata. Specimens were captured in Lebanese waters in the framework of a multiannual fisheries-independent data collection for the assessment of demersal coastal species. Sex and geographic distri- bution effects on WLRs was also examined. 2 | MATERIALS AND METHODS The specimens were collected from June 2012 to October 2014 in the Lebanese marine waters, Levantine Sea (eastern Mediterranean). Lebanese coastal line (220 km) was broken down into 4 regions (Figure 1) to allow geographical-based analysis. Specimens were sam- pled using trammel and gill nets with different mesh sizes lowered by