Spatial and temporal variations in parasite communities of an overexploited fish species: the Argentine hake, Merluccius hubbsi Marini (Gadiformes: Merluciidae)

CANTATORE, D.M.P.; LANFRANCHI, A.L.; TIMI, J.T.

Melbourne

Congreso; XIIth International Congress of Parasitology (ICOPA); 2010

The Argentine hake is main target of Argentine fishery, representing the Patagonian stock(south of 41°S) near 85% of the estimated biomass. Its overexplotation had produced a severedecline in population size, spatial changes in spawning aggregations and a more scattereddistribution. These changes could affect the structure of parasite populations, especially formonoxenous and specific parasites, which require a minimum threshold of host populationsize/density to ensure transmission and sustaining viable populations. A decade ago, parasiteswere successfully used to discriminate between Patagonian and Bonaerense (north of 41ºS)stocks. Although the actual number of stocks in Patagonian waters remains controversial, nocomparisons among samples from the former were carried out. Three samples of hake (twoPatagonian separated by 1° latitude one Bonaerense) were examined for parasites and comparedwith previous Patagonian samples. The aims of this study were; 1) to determine ifdifferentiation among Bonaerense and Patagonian stock persists after decade; 2) to search forvariations between zones within the Patagonian regions; 3) to asses whether these variations arecaused primarily by changes in abundance or composition of parasite communities, and 4)evaluate if temporal changes in parasite populations are linked with the decline of hakepopulations. Univariate and multivariate analyses of parasite abundance and compositionshowed that: 1) clear discrimination of both stocks still exists, given mainly by compositionaldifferences; 2) Patagonian samples showed significant differences in parasites abundances atspatial and temporal scales, which were more important over space, but constituted anhomogeneous group in relation to Bonaerense hakes; 3) temporal variability was mainly due toan increase in unspecific larval parasites abundance. So, variability at large spatial scale wasmainly compositional, while smaller spatial scale and temporal variation were driven bychanges in relative abundance, particularly by numerically dominant taxa, instead of specifichake parasites.