Stock composition of the rough scad, Trachurus lathami Nichols in South American Atlantic waters: geographical patterns of parasite community structure as discriminating tools

BRAICOVICH, P. E.; LUQUE J.L.; TIMI J.T.

Viña del Mar

Congreso; VIIth International Symposium on Fish Parasites; 2011

The aims of this study were: 1) to evaluate the effect of short- and long-term variability of parasite communities of T. lathami in a single locality and 2) to identify the existence of different stocks in three zones of south-west Atlantic waters. In total 273 specimens of T. lathami were examined. To assess the effect of both short term and long term variability on parasite burdens, three monthly samples were obtained from Miramar (MI) and two samples from Villa Gesell separated by a period of one year (VG) (Buenos Aires province, Argentina), respectively. To reveal differences between zones a third sample from Cabo Frio (CF) (Brazil) was analized. Differences across localities were analyzed after pooling fish from each Argentinean locality. All rough scad were parasitized by at least one of 27 parasite species. Similarity-based multivariate analysis showed no significant variability among the assemblages between both monthly and annual samples, but highly significant differences among localities. Comparisons of both prevalence and abundance between zones showed that the lower and higher number of differences occurred for the pairs MI-VG and CF-MI, respectively. A canonical analysis of principal coordinates showed significant differences among samples. Grillotia carvajalregorum was the most important species in determining the position of Argentinean samples, especially those from MI, while Ectenurus virgulus, Raphidascaris sp. and Hysterothylacium sp. were the most important species related to fish from CF. The parasite assemblage of T. lathami showed a notable persistence at both short- and long-term temporal scales within the same locality and a high variability at spatial scale, constituting an evidence of the existence of three independent stocks of T. lathami in South Atlantic waters.