The 2015-2016 El Niño increased infection parameters of copepods on Eastern Tropical Pacific dolphinfish populations

Abstract

The oceanographic conditions of the Pacific Ocean are largely modified by El Niño (EN), affecting several ecological processes. Parasites and other marine organisms respond to environmental variation, but the influence of the EN cycle on the seasonal variation of parasitic copepods has not been yet evaluated. We analysed the relation between infection parameters (prevalence and mean intensity) of the widespread parasitic copepods Caligus bonito and Charopinopsis quaternia in the dolphinfish Coryphaena hippurus and oceanography during the strong 2015-16 EN. Fish were collected from capture fisheries on the Ecuadorian coast (Tropical Eastern Pacific) over a 2-year period. Variations of sea surface temperature (SST), salinity, chlorophyll a (Chl-a), Oceanic Niño Index (ONI), total host length (TL) and monthly infection parameters of both copepod species were analysed using time series and cross-correlations. We used the generalised additive models for determine the relationship between environmental variables and infection parameters. The total body length of the ovigerous females and the length of the eggs of C. bonito were measured in both periods. Infection parameters of both C. bonito and Ch. quaternia showed seasonal and annual patterns associated with the variation of environmental variables examined (SST, salinity, Chl-a and ONI 1+2). Infection parameters of both copepod species were significantly correlated with ONI 1+2, SST, TL and Chl-a throughout the GAMLSS model, and the explained deviance contribution ranged from 16%-36%. Our results suggest than an anomaly higher than +0.5˚C triggers a risen in infection parameters of both parasitic copepods. This risen could be related to increases in egg length, female numbers and the total length of the ovigerous females in EN period. This study provides the first evidence showing that tropical parasitic copepods are sensitive to the influence of EN event, especially from SST variations. The observed behaviour of parasitic copepods likely affects the host populations and structure of the marine ecosystem at different scales.

Persistent companionships: The parasitic copepod community of the dolphinfish Coryphaena hippurus on the Ecuadorian coast

“…According to L. González and Carvajal (2003), fluctuations in environment variables, mainly temperature, modify the population dynamics and the distribution of parasitic copepods. This has been recently shown in C. bonito and B. quaternia in the Ecuadorian Pacific Ocean (Santana‐Piñeros et al, 2020), an area with wide temperature changes because of the arrival of the Humboldt current, which produces upwellings of cold, nutrient‐rich deeper water and an increase in trophic activity (Daneri et al, 2000; Graco et al, 2007; Jones, 1998; Okuda et al, 1983), thus favoring the dispersal and occurrence of infective stages of copepods and pelagic fish (ERFEN, 2011). On the other hand, these species of copepods have been recorded in more than a dozen hosts belonging to diverse fish families, such as Carangidae, Istiophoridae, Mugilidae, Sciaenidae, and mainly Scombridae (Cressey & Cressey, 1980; Kabata, 1979; Lester et al, 1985; Rohde et al, 1980; Williams & Bunkley‐Williams, 1996).…”

“…In Ecuador, C. bonito has been recorded previously in Cratinus agassizii Steindachner 1878 from the Galápagos Islands (Wilson, 1937). Also, Santana‐Piñeros et al (2020) recently reported C. bonito as parasite species of C. hippurus , with a PR fluctuating between 29% and 100%.…”

“…Conversely, Burnett‐Herkes (1974) observed negative relationships between PR and host size in C. bonito and B. quaternia , and positive relationships in five other copepod species in common dolphinfish from the Strait of Florida, central Atlantic. These differences suggest that the infection indices of copepods in C. hippurus could be more influenced by environmental conditions such as salinity, sea surface temperature, and chlorophyll (see Santana‐Piñeros et al, 2020), as well as by host availability at each locality, rather than by intrinsic factors such as immunity, sexual maturation, or host age (Costello, 2006). This idea is reinforced by the fact that dolphinfish is a short‐lived species, which tends to approach coastal waters and have a complex stock structure based on many small stocks with more localized migration circuits, rather than large stocks with large migratory routes (Oxenford, 1999).…”

“…The Ecuadorian fauna also differs from the Mediterranean fauna, where E. nympha (= E. nordmannii ) was reported to be a core species, B. quaternia a satellite species, and C. bonito , C. coryphaenae , and C. productus were rare species (Carbonell et al, 1999). The specific composition of the parasitic copepod community of common dolphinfish along its distributional range is very similar, but local oceanographic variables (e.g., temperature, salinity, and chlorophyll) are likely to have a considerable influence on host–parasite interactions (Santana‐Piñeros et al, 2020), thus producing variable species richness and abundances. The differences in the PR of E. nordmannii on C. hippurus in the Atlantic Ocean and Mediterranean Sea populations have been attributed to differences in water temperatures between these two areas (Carbonell et al, 1999).…”

Power spectra density and similarity analysis of COVID-19 mortality waves across countries

“…We did a search in the literature for biological variables related to this periodicity of every 11 and 4.5 months, and we only found that infections in aquatic parasitic copepods ( Ch. Quaternia ) are increased with a periodicity of every 11 and 3 months in the oceanographic conditions of the Pacific Ocean associated with the 2015-2016 El Niño (Santana-Piñeros et al, 2020). The reader may note the parallelism in the periodicity of infection parameters in Ch.…”