Length–weight relationships for 22 fish species of the Mar Menor coastal lagoon (western Mediterranean Sea) By D. Verdiell-Cubedo, F. J. Oliva-Paterna and M. Torralva Department of Zoology, University of Murcia, Murcia, Spain Summary Length–weight relationships were estimated for 22 species of the Mar Menor coastal lagoon (south-eastern Spain): Lipoph- rys dalmatinus, Salaria pavo, Callionymus pusillus, Aphanius iberus, Engraulis encrasicolus, Gobius cobitis, G. niger, G. paganellus, Pomatoschistus marmoratus, Symphodus cinereus, Chelon labrosus, Liza aurata, L. ramado, L. saliens, Mugil cephalus, Diplodus puntazzo, D. sargus sargus, Lithognathus mormyrus, Sarpa salpa, Sparus aurata, Hippocampus guttulatus and Syngnathus abaster. The captures were made in shallow areas of the lagoon during 2002–2004. Significant length– weight relationships were found for all species. Introduction Length–weight relationships for fish have been used exten- sively to provide information on the condition of fish, their isometric or allometric growth, in the analysis of ontogenic changes, to compare life histories of fish species between regions as well as other aspects of fish population dynamics. In fisheries biology, length–weight relationships are useful for the conversion of growth-in-length equations to growth-in-weight for use in stock assessment models and to estimate stock biomass from limited sample sizes (Binohlan and Pauly, 1998; Koutrakis and Tsikliras, 2003; Valle et al., 2003; Ecoutin et al., 2005). In this study we report the length–weight relationships for 22 fish species collected from the Mar Menor coastal lagoon (south-eastern Spain). Included are the most common species of shallow areas as well as juvenile fish species of commercial interest that use the coastal lagoon as a nursery area. Materials and methods Study area The Mar Menor is a hypersaline coastal lagoon located in a semiarid region of the south-eastern Iberian Peninsula. It is one of the largest coastal lagoons in the Mediterranean region and in Europe, with a surface area of 135 km 2 and average depth of 3–4 m. It is separated from the Mediter- ranean Sea by a 22 km long sandbar, with three narrow channels connecting it to the sea. The lagoon shows a salinity range of 39–45 with a temperature varying from 10°C in winter to 32°C in summer. The bottom is principally covered with dense meadows of the invasive macroalga Caulerpa prolifera, although shallow areas are covered with meadows of Cymodocea nodosa. The lagoon supports important commercial fisheries, mainly fishes such as eel (Anguilla anguilla), grey mullets (Liza spp. and Mugil cephalus), gilthead bream (Sparus aurata), sea bass (Dicentrarchus labrax) and striped bream (Lithognathus mor- myrus) (Pe´rez-Ruzafa et al., 2004). Sampling design Field studies were conducted in the period of 2002–2004 in the shallow areas of the Mar Menor coastal lagoon. Samples were collected using a 10-m long bag seine net with 0.5 mm mesh size, which allowed the collection of juvenile fish and adults of small size species. Specimens were preserved in 7% formaldehyde, identified and measured for total length (TL) to the nearest 0.1 cm and weighed (total weight, TW) to the nearest 0.01 g. The relationship was established using linear regression analysis, TW vs TL (log-transformed): TW ¼ log(a)+ blog (TL), where a is the intercept of the regression curve (coefficient related to body form) and b the regression coefficient (exponent indicating isometric growth when equal to 3). The significance of the regression was assessed by ANOVA ANOVA, and the b-value for each species was tested by t-test to verify that it was significantly different from the isometric growth (b ¼ 3) (Sokal and Rohlf, 1981). Results and discussion Overall, 11 158 specimens of 22 different species belonging to nine families were weighed and measured. During the course of the study, Mugilidae and Gobiidae were the most abundant families. The length–weight relationships are summarized in Table 1. Linear regressions were significant for all species (P < 0.001). The sample size ranged from 2955 for L. aurata to 17 for Engraulis encrasicolus. Values of b equal to 3 indicate that the fish grows isometrically; values different from 3 indicates allometric growth. The exponent b varied between 2.36 for Callionymus pusillus and 3.36 for M. cephalus. It was also low (b ¼ 2.68) for E. encrasicolus, whereas all remaining values of b were higher than 2.91 (Table 1). Nine species showed isometric growth (b 3): Lipophrys dalmatinus, Salaria pavo, Aphanius iberus, E. encrasicolus, Gobius niger, Chelon labrosus, L. ramado, Sarpa salpa and Hippocampus guttulatus; two species showed negative allometric growth (b < 3): Ca. pusillus and Syngna- thus abaster; all remaining species showed positive allometric growth (b > 3): G. cobitis, G. paganellus, Pomatoschistus marmoratus, Symphodus cinereus, L. aurata, L. saliens, M. cephalus, Diplodus puntazzo, D. sargus sargus, Li. mormyrus and Sp. aurata. J. Appl. Ichthyol. 22 (2006), 293–294 Ó 2006 Blackwell Verlag, Berlin ISSN 0175–8659 Received: July 1, 2005 Accepted: November 10, 2005 U.S. Copyright Clearance Centre Code Statement: 0175–8659/2006/2204–0293$15.00/0 www.blackwell-synergy.com