Influence of Thermal Regimes on the Relationship between Parasitic Load and Body Condition in European Sardine along the Catalan Coast

Abstract

The small pelagic European sardine presents high commercial and ecological values. Due to its cold-temperate water affinity, stocks are affected by global warming. Water temperature rise may change primary productivity patterns, negatively affecting fish condition and increasing parasite incidence. In this context, sardine health status was evaluated through the annual cycle on the Catalan Coast using thermal regimes comparison. Morphogravimetric parameters, sex and gonadal stages were assessed; infection by nematodes was characterised, and body condition was estimated by the Le Cren Factor and lipid content measured using a fish fat meter. Significant statistical differences were observed in spawning dynamics, body condition, and parasite infection between thermal regimes. Sardines from the colder north area had better condition and an earlier spawning, with lower parasite incidence (in terms of total prevalence, mean intensity and abundance) than those from the southern coast. Hysterothylacium spp. was the most abundant nematode, while Anisakis spp. prevalence was null in the two locations. Seasonal differences in nematode load were observed along the Catalan Coast, with lower prevalence during the summer and higher in winter-spring. Although previous studies have underestimated parasite influence on sardine health status, parasite abundance and sardine condition were negatively correlated. Seawater temperature and primary productivity are the proposed factors promoting differentiation in nematode infection and fish condition throughout the annual cycle and between locations.

Ascaridoid parasites in European sardine throughout the annual cycle: Variability in parasitic load according to host stock features

“…and Hysterothylacium spp. have been previously reported in sardines from the Atlantic and Mediterranean basin ( Rello et al, 2008 ; Gutiérrez-Galindo et al, 2010 ; Mladineo and Poljak, 2014 ; Serracca et al, 2014 ; Cavallero et al, 2015 ; Molina-Fernández et al, 2015 ; Bušelić et al, 2018 ; Frigola-Tepe et al, 2022 ). The comparison of these results reveals variable prevalence in sardines originating from different fishing areas, as confirmed by our study, in which, despite the differences among stocks, parasitic indices were generally low for both genus throughout the analysed area.…”

“…In this line, no Anisakis spp. were characterised in sardines from the Northern Spanish Coast ( 6), supported by previous studies in the area ( Rello et al, 2008 ; Gutiérrez-Galindo et al, 2010 ; Frigola-Tepe et al, 2022 ), and contradicting analyses based on morphological identification ( Biton-Porsmoguer et al, 2020 ). Nevertheless, H. aduncum was observed throughout the whole year, except in winter in this location, and with much lower total prevalence and mean intensity than the 25.21% and the 2.10 obtained by Rello et al (2008) .…”

“…In this context, our work has attempted to shed light on the condition of the stocks and their relationship with parasitism, as well as to study whether the individual condition of the individuals in each area can be linked to the presence of ascaridoids. In the clupeoid anchovy, lower lipid content is related with a higher intensity of certain parasites as digeneans and nematodes ( Ferrer-Maza et al, 2016 ), also found by Frigola-Tepe et al (2022) in sardine. Moreover, the body condition of infected cod was lower than that of those free of parasites and declined with the intensity of infection; the condition of most infected fish was up to 20% lower than that of uninfected individuals ( Horbowy et al, 2016 ).…”

“…Nevertheless, as parasitism may affect host physiology, morphology, reproduction and behaviour ( Timi and Poulin, 2020 ), it must be considered as a potentially determining factor in the state of health and population dynamics of the stocks, and especially the context of vulnerability in which sardines are found. Similarly, the inverse relationship between parasitism and sardine condition has been suggested, as healthier fish stocks could be considered more resistant to parasite infections ( Pennino et al, 2020 ; Frigola-Tepe et al, 2022 ). Furthermore, the current state of the habitats is being altered by environmental pressures derived from global change, which could also be conditioning and altering the dynamics and life cycles of ascaridoid nematodes.…”

A new threat to Sardina pilchardus in the northwestern Mediterranean: Genetic validation of the presence of lethal parasites in pelagic eggs and ovaries

“…Climate change (Ramírez et al, 2018;Fernández-Corredor et al, 2021), overfishing (Van Beveren et al, 2014;Ramírez et al, 2021), changes in phytoplankton and zooplankton composition (Van Beveren et al, 2014;Albo-Puigserver et al, 2021), pollution, parasite infections (Pennino et al, 2020;Frigola-Tepe et al, 2022;Caballero-Huertas, 2023), and the combined effects of these factors (Caballero-Huertas et al, 2023) have all become major threats to European sardine populations in the northwestern Mediterranean Sea. The cumulative impact of these stressors has resulted in unsustainable biomass levels and impaired health status (FAO, 2022).…”