Macromolecular reserves content in relation to condition index of Zygochlamys patagonica in the SW Atlantic

CAMPODÓNICO S; GARAFFO GV; SCHWARTZ M; VITTONE M

Workshop; 19th International Pectinid Workshop; 2013

Introducction The patagonian scallop (Zygochlamys patagonica) fishery is conducted since 1996 in the SW Atlantic (Lasta and Bremec, 1998), with an annual catch of 47.325 tons of commercial size scallops that produce 6.628 tons of adductor muscle landing (Campodónico and Herrera, 2012). Considering the commercial importance of this species and the importance of the knowledge on reproductive biology for developing a proper management, little information concerning its reproduction is available. Like several scallop species, the Z. patagonica presents a seasonal variation in gonad weight and adductor muscle in relation to reproductive season (Campodónico et al, 2001; Robinson et al., 1981). For Z. patagonica, spawning occurs from early spring to early fall at Management Unit B (MU, ex Banco Reclutas, Campodónico et al, 2008), and maximum muscle development occurs during fall (Valero, 2002). The reproductive cycles of marine bivalves are strongly related to energy storage-utilization cycles and environmental parameters such as water temperature and food availability (Gabbott, 1983). In addition, gonad maturation leads to mobilization of macromolecular (i.e. glycogen) reserves from somatic tissues in many scallops. The objective of the study is to examine the seasonal variations of the relative gonadal condition index (RGCI) and relative muscle condition index (RMCI) of Z.patagonica in relation to macromolecular reserves (glycogen, protein and lipids) and reproductive stages. Materials and methods Sampling of Z. patagonica were performed in MU D (between 41°24 and 42°17?S along to the 100-m isobath, SW Atlantic Ocean). Samples were obtained on board of commercial vessels fleet between January 2010 and August 2011. Shell height (umbo to ventral axis, SH) was measured for each individual to the nearest 1 mm and gonadal and muscle mass were registered (GM, MM; ± 0.01 g). Gonadal maturity was determined macroscopically mainly based on colour, external appearance and size of testes and ovaries following Campodónico et al., 2008. Gonadal (RGCI) and muscle (RMCI) relative condition index were estimated based on Campodónico et al. (2008): A two-way analysis of variance was performed to examine differences in the RGCI and RMCI between months and sexes. Given the RGCI data heteroscedasticity (Cochran´s C, P < 0.01), ANOVA was still performed since this test is robust to heterogeneity of variance; however, the level of significance was set at α = 0.01 to reduce the risk of Type I error (Underwood, 1997). Biochemical composition of the tissues was estimated from the percentages composition. Glycogen was determined by colorimetric method with Antrona reactive (Fraga, 1956). Proteins were determined by Kjeldhal method. Lipids were determined by Randall method. Results and discussion RMCI reached its maximum during summer and its minimum in winter. On the other hand, RGCI presents a seems to be inverse pattern with maximum and minimum yields in winter and summer, respectively (RGMI: F = 47.38, p