SPATIAL AND TEMPORAL VARIATION IN THE CONDITION FACTOR OF SMALL PELAGIC TELEOSTS IN THE GULF OF LIONS (NW MEDITERRANEAN) D. Banaru *, T. Ballerini , C. Michelot , B. Le Bourg and C. Saraux MIO (Mediteranean Institute of Oceanography), Aix-Marseille University, Campus de Luminy, case 901, 13288 Marseille, France - Daniela.Banaru@univ-amu.fr IFREMER, UMR 212 EME (Ecosystèmes Marins Exploités), Av. Jean Monnet, 34203 Sète, France Abstract This paper presents data on the condition factor for sardines, anchovies and sprats in the Gulf of Lions in 2011. The condition factor was estimated through both morphometric measures and C/N ratios. Globally, sprats exhibited a better condition than sardines and anchovies. Sprats showed a better condition in the coastal area, while anchovies presented the best condition on the continental shelf and on the shelf break. The central area was the most favorable for sardines and the most unfavorable for sprats. All species presented a better condition in June than in July. These results suggest an important influence of habitat and feeding resources on small pelagic teleosts condition. Keywords: Biometrics, Teleostei, Coastal waters, Gulf of Lyon, Trophic relations 1 1 1 1 2 1 2 Introduction The study area is situated in the Gulf of Lions (42.4-43.5° N; 3.0-5.4° E) where sardines (European pilchard, Sardina pilchardus (Walbaum, 1792)) and anchovies (European anchovy, Engraulis encrasicolus (Linnaeus, 1758) were traditionally the most important species in terms of both biomass and fishery landings (about 50%) [1, 2]. However in recent years the biomass of sprats (European sprat, Sprattus sprattus (Linnaeus, 1758)), a non-commercial species, has strongly increased while the biomass of sardines and anchovies has decreased causing an important fishery crisis (Bigot J. L., pers. comm.). The three species potentially compete for food and habitat. Individual condition, a strong proxy for fitness and a good indicator of the population health are thought to be strongly related to their feeding environment. Here we tested the hypothesis that the condition factor is species-, space-, and time-dependent. Materials and methods A total of 1181 samples of sardines (334), anchovies (365) and sprats (482) varying in size between 3.5 and 16.5 cm, were collected in the Gulf of Lions, covering the western, central and eastern areas, and comprising the coastal area (0-50 m), the continental shelf (50-200 m) and the shelf break (>200 m) (Fig. 1). Sampling was carried out during the IFREMER scientific surveys MEDITS and PELMED in June and July 2011 onboard of the N/O Europe. Fig. 1. Sampling stations in the Gulf of Lions The condition factor was estimated by means of morphometric measures and C/N ratios (related to the lipid content). Individual body-length and wet-weight were used to calculate the relative condition factor Kn (see formula in [3]). Sub- samples of muscle (sardines 10-12 cm, n=31; anchovies 10-11 cm, n=44; sprats 9-10 cm, n=35) were analyzed for C/N ratios using continuous flow mass spectroscopy (CF-IRMS). Data were tested for normality and homogeneity of variance and the effects of different factors (species, area, depth, month) on Kn and C/N values were tested using parametric (Independent T-test (T) or one- way ANOVA (F)) and non-parametric (Mann-Whitney (U) or Kruskal-Wallis (H)) analyses of variance. Results and discussion C/N values indicated a better condition for sprats (4.33 + 0.60) compared to sardines (3.22 + 0.11) and anchovies (3.17 + 0.06) (H = 72.2; p= 0.000). Sardines had the best condition in the central area according to C/N values. Contrarily, sprats showed here the lowest condition according to Kn values (Table 1). Anchovies’ condition increased with depth, i.e. it was higher on the continental shelf and shelf break than in the coastal area. On the contrary, sprats appeared to be in better condition in the coastal area. All species exhibited a better condition in June than in July (Table 1). The condition factor varied according to the species considered and in space and time. These results might be explained by environmental conditions, potential differences in the composition of plankton assemblages, and individual diet. More data and further analyses are needed in order to better understand the effect of the habitat on these three species of small pelagic teleosts in the NW Mediterranean. Tab. 1. Kn et C/N values according to species, area, depth and month. For the meaning of T, F, U, H see text, p is the p-value, *p < 0.05, **p < 0.01, ***p < 0.001, ns = nonsignificant. References 1 - Palomera I., Olivar M.P., Salat J., Sabates A., Coll M., Garcia A. and Morales-Nin B., 2007. Small pelagic fish in the NW Mediterranean Sea: an ecological review. Prog. Oceanogr., 74: 377-396. 2 - Banaru D., Mellon-Duval C., Roos D., Bigot J.L., Souplet A., Jadaud A., Beaubrun P. and Fromentin J.M., 2013. Trophic structure in the Gulf of Lions marine ecosystem (north-western Mediterranean Sea) and fishing impacts. J. Mar. Syst., 111-112: 45-68. 3 - Banaru D. and Harmelin-Vivien M., 2009. Trophic links and riverine effects on food webs of pelagic fish of the north-western Black Sea. Mar. Fresh. Res., 60: 529-540. 732 Rapp. Comm. int. Mer Médit., 40, 2013 View publication stats View publication stats