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Seasonal differences in parasite infection of skipjack tuna in Madeira archipelago

Bárbara Cavaleiro1, Margarida Hermida1, 2, 3* and Aurélia Saraiva4, 5
  • 1 Centro de Ciências do Mar e do Ambiente (MARE), Portugal
  • 2 CIIMAR-Madeira, Interdisciplinary Centre of Marine and Environmental Research of Madeira, Portugal
  • 3 Observatório Oceânico da Madeira (OOM), Portugal
  • 4 Centro Interdisciplinar de Pesquisa Marine e Ambiental (CIIMAR), Portugal
  • 5 Faculdade de Ciências, Universidade do Porto, Biology Department, Portugal

Skipjack tuna (Katsuwonus pelamis) is an important tropical tuna species which is fished throughout its geographic range. It occurs seasonally in the waters around Madeira archipelago, typically in the warmer months (Hermida & Delgado 2016), and is usually the second most landed tuna species in the region (Gouveia et al. 2017). Despite its importance to fisheries, knowledge of its migration routes in the Atlantic is limited (Fonteneau 2015). In this study, we have attempted to apply parasites as biological tags to infer about its migration patterns in the southern North-east Atlantic, by conducting a seasonality analysis of skipjack caught in Madeira between April and October of 2017. Several parasites have been suggested as biological tags for skipjack. Lester (1985) distinguished between permanent parasites, such as Tentacularia coryphaenae and larval anisakids, semi-permanent parasites such as didymozoid digeneans, and temporary parasites such as Caligus spp. and adult intestinal acanthocephalans. Recently, Hermida et al. (2018) suggested that a promising strategy for migration studies of skipjack might involve using a conjunction of permanent and semi-permanent parasites, along with more temporary ones which might provide a useful snapshot of the recent whereabouts of the tunas. In this study, significant differences were detected in seasonality for Anisakis sp. larvae (surrounding the viscera), Rhadinorhynchus sp. (in the intestinal lumen), and Tentacularia coryphaenae (in the body cavity). While the abundance of the first two species declined from early to late season, T. coryphaenae’s abundance increased. There were no significant differences in the size of skipjack observed in different seasons. The gill parasite assemblages were also investigated, but there were no significant seasonal differences in the abundance of the most prevalent gill didymozoids: Didymocylindrus filiformis, D. fusiformis, D. simplex, and Didymozoon longicolle. This suggests that the study of gill parasite assemblages, on its own, may be insufficiently informative. The higher abundance of Anisakis sp. in early-season skipjack could indicate that these fish have migrated from spawning areas near the Gulf of Guinea, where Anisakis sp. prevalences of 100% have been detected in skipjack (Cissé et al. 2007), whereas late-season skipjack are more likely to be returning from feeding areas north of Madeira, possibly including western Mediterranean areas. Although there are no studies on skipjack infection by Anisakis sp. larvae in those regions, infection levels of this parasite in prey species such as Scomber colias (Ramos et al. 1995) are lower in Mediterranean when compared to Atlantic areas (Abattouy et al. 2011). The decrease in Rhadinorhynchus sp. abundance can reflect their loss from the host, since they are temporary parasites. In relation to the T. coryphaenae larvae, Lester et al. (1985) suggested that they are more common in tropical areas. These are long-lived parasites which are not usually lost from the host. Their increase from early to late season, however, suggests that they continue to be acquired by skipjack in the waters around Madeira, where Tentacularia are also abundant and occur in prey species such as Scomber colias (Costa et al. 2011). We should highlight that high Anisakis sp. infection levels were detected in skipjack, which is consistent with previous studies (Cissé et al. 2007; Hermida et al. 2018). Anisakis sp. infection levels in skipjack are much higher than in larger tuna species such as the bluefin (e.g. Mladineo et al. 2011; de la Serna et al. 2012). These results suggest the need for adequate food safety measures with regards to the consumption of skipjack tuna. In particular, skipjack should be properly cooked through or, alternatively, frozen prior to consumption in order to inactivate the parasites, if it is to be consumed in a raw or undercooked state.

Acknowledgements

B. Cavaleiro was financially supported by a research grant within the project OceanWebs (PTDC/MAR-PRO/0929/2014). M. Hermida was financially supported by a post-doctoral grant from ARDITI, Project M1420-09-5369-FSE-000001. This study was partially supported by the Oceanic Observatory of Madeira Project (M1420-01-0145-FEDER-000001-Observatório Oceânico da Madeira-OOM) and MARISCOMAC project (UE 2017-2020, Project MAC/2.3d/097).

References

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Keywords: katsuwonus pelamis, Madeira, Parasites, Skipjack, Tuna

Conference: IMMR'18 | International Meeting on Marine Research 2018, Peniche, Portugal, 5 Jul - 6 Jul, 2018.

Presentation Type: Oral Presentation

Topic: Fisheries and Management

Citation: Cavaleiro B, Hermida M and Saraiva A (2019). Seasonal differences in parasite infection of skipjack tuna in Madeira archipelago. Front. Mar. Sci. Conference Abstract: IMMR'18 | International Meeting on Marine Research 2018. doi: 10.3389/conf.FMARS.2018.06.00031

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Received: 26 Apr 2018; Published Online: 07 Jan 2019.

* Correspondence: PhD. Margarida Hermida, CIIMAR-Madeira, Interdisciplinary Centre of Marine and Environmental Research of Madeira, Funchal, Madeira, 9020-105, Portugal, margaridahermida@gmail.com