Parasites of the Argentine shortfin squid Illex argentinus as biological tags for stock discrimination: advantages and limitations.

BRAICOVICH, PAOLA E.; LANFRANCHI, ANA L.; IRIGOITIA, MANUEL M.; GUTIÉRREZ, MARÍA PAZ; IVANOVIC, MARCELA; PRANDONI, NICOLÁS; ELENA, BEATRIZ; TIMI, JUAN T.

Copenhague

Congreso; 15th International Congress of parasitology; 2022

World Federation of Parasitologists

Introduction: The Argentine shortfin squid (I. argentinus) sustains a major fishery in the southwestern Atlantic. Its lifespan lasts around one year and its recruitment and density largely depend on environmental conditions. Four stocks are recognized with the Southpatagonic (SPS) and Summer Spawning (SSS) Stocks, overlapping their distributions in northern Patagonian waters during summer. Aim: to assess the value of parasites of I. argentinus as indicators of stock structureMethods: A total of 187 squids (5 samples) were caught at the region where SPS and SSS overlaps, measured, assigned to each stock according their gonadal maturity index and examined for parasites. A sample of 41 squids from a third stock (Bonaerensis-northpatagonic-BNPS) was included in the analyses. The structure of parasite infracommunities was compared across samples and across stocks by mean of multivariate methods.Results: Thirteen parasitic taxa were found. Infracommunities were similar among the 5 samples of SPS-SSS, but significantly different from BNPS. When grouped by stock, assemblages of SPS-SSS were similar each other and different from BNPS.Conclusions: Since most parasites, especially those numerically dominant, were short-lived and trophically transmitted, they can only indicate recent feeding history. Therefore, they were unable to discriminate squids of two stocks mixing for a period. Those squids geographically distant and living in different oceanographic conditions were clearly discriminated. Squid parasites are suitable indicators for stock assessment of spatially discrete unities, however, its usefulness for discrimination of temporarily mixing stocks is limited by the transitory condition of the parasite communities. Acknowledgement: Grant PICT 2019-3376Keywords: Shortfin squid, stock assessment, biological tags, Fishery