Length–girth relations of fishes from a Mediterranean lagoon system

Abstract

Moutopoulos D.K., Dimitriou N., Nystas T., Koutsikopoulos C. 2017. Length-girth relations of fishes from a Mediterranean lagoon system. Acta Ichthyol. Piscat. 47 (4): 397-400.Abstract. We estimated the relations between total length (TL) and opercular (G ope ) and maximum (G max ) girths, for the eight most representative lagoon fish species in Mesolonghi-Etolikon lagoons within 2015-2017 (June through December). The following species were studied: Chelon saliens (Risso, 1810); Chelon auratus (Risso, 1810); Chelon ramada (Risso, 1827); Mugil cephalus Linnaeus, 1758; Diplodus puntazzo (Walbaum, 1792); Diplodus sargus (Linnaeus, 1758); Sparus aurata Linnaeus, 1758; Dicentrarchus labrax (Linnaeus, 1758). For five of these species (C. saliens, C. auratus, C. ramada, S. aurata, and D. labrax) LGR estimates were not available. Results showed that both G ope and G max increased significantly linearly with TL for all studied species with all r 2 values being higher than 0.862. When G max values were plotted against TL for all species combined, two significant (ANCOVA, P < 0.05) length-girth relations were identified corresponding to different body shapes. The implications of girth measurements for lagoon gear selectivity estimates are also discussed. Keywords: fish girth, fish morphology, barrier traps, Mesolonghi-Etolikon lagoons, Greece In the majority of the Mediterranean lagoons (Cataudella et al. 2015) fisheries exploitation is conducted using permanent fishing devices made of reinforced concrete, the barrier traps that are installed at the interface between the lagoon and open sea. Fisheries based on seasonal on-going migrations of fry and adult fish species for spawning, foraging, and shelter between open sea and lagoons (Franco et al. 2010) during June to February (Katselis et al. 2003). The multispecies nature of the lagoon fisheries, which in turn implied the exploitation of numerous species with different growth, maturity, behaviour, and body shape are increasing the uncertainty on the determination of gear-specific efficiency.The aim of the presently reported study was the estimation of LGR for eight fish caught in the MesolonghiEtolikon lagoon system. The following species were studied: Chelon saliens (Risso, 1810); Chelon auratus (Risso, 1810); Chelon ramada (Risso, 1827); Mugil cephalus Linnaeus, 1758; Diplodus puntazzo (Walbaum, 1792); Diplodus sargus (Linnaeus, 1758); Sparus aurata Linnaeus, 1758; Dicentrarchus labrax (Linnaeus, 1758). Moutopoulos et al. 398The studied species (Table 1) (Koutrakis et al. 2007). Total length (TL) and body girth were measured to the nearest millimetre for 1168 individuals. Girth measurements were obtained using a digital calliper and were measured from the height and width of opercular (G ope ) and of maximum (G max ) girths. The perimeter of the ellipse (where minor and major radii are the maximum height and width, respectively) was estimated for each of the above proxies using the formula proposed by Ramanujan in 1914 (Arfken and Weber 2000) and applied in similar s...

Length-girth relationships of 24 marine fishes in the northern Aegean Sea (eastern Mediterranean Sea)

“…Despite their importance in fisheries research and management, studies focusing on total length -body girth relationships for marine fish species in the Mediterranean Sea and the adjacent seas are limited (Greece: STERGIOU & KARPOUZI, 2003;Portugal: MENDES et al, 2006;SANTOS et al, 2006; Saudi Arabia /Red Sea: GABR & MAL, 2018). More often, LGRs are used as a mean to assess fishing gear selectivity (FABI et al, 2002;ÖZEKINCI, 2005;MOUTOPOULOS et al, 2017;ILKYAZ, 2018), since length-based selectivity models are justified when a linear relationship between fish girth and fish length is established (KURKILAHTI et al, 2002). Occasionally, the estimation of LGRs is included in morphometric-biometric analyses of single species (GARCIA-RODRIGUEZ & ESTEBAN, 1998) and in the estimation of girth by applying different models (RAGONESE & BERTOLINO, 1994).…”