Relationships between tuna catch and variable frequency oceanographic conditions

Abstract

Abstract. Skipjack (Katsuwunus pelamis), yellow fin (Thunnus albacares) and albacore (Thunnus alulunga) tunas landed in the Eastern Pacific Ocean (EPO) countries and Ecuador were correlated to the Indexes Oceanic El Niño (ONI) and Multivariate Enso Index (MEI). The temporal series 1983–2012, and 1977–1999 (warm Pacific Decadal Oscillation, PDO), and 2000–2012 (cold PDO) were analyzed. Linear correlation showed that at least 11 % of the total landings were associated with the MEI, with a slightly negative gradient from cold to warm conditions. When non-linear regression (n = 6), the R2 was higher up to 0.304 (MEI, r = 0.551). The correlation shows high spread from −0.5 to +0.5 for both MEI/ONI; the highest landings occurred at 0.34–0.45; both indexes suggested that at extreme values < −1.0 and > 1.1 total landings tend to decrease. Landings were associated up to 21.9 % (MEI) in 2000–2012, 1983–1999 rendered lower R2 (< 0.09); i.e., during cold PDO periods there was a higher association between landings and oceanographic conditions. For the non-linear regression (n = 6) a R2 of 0.374 (MEI) and 0.408 (ONI) were registered, for the 2000–2012, a higher R2 was observed in 1983–1999, 0.443 and 0.711 for MEI and ONI respectively, suggesting that is better to analyze split series (1983–1999, 2000–2012) than as a whole (1983–2012), due to noise produced by the transition from hot to cold PDOs. The highest landings were in the range −0.2 to 0.5 for MEI/ONI. The linear regression of skipjack landings in Ecuador gave an R2 of 0.140 (MEI) and 0.066 (ONI) and the non-linear were 0.440 and 0.183 respectively. Total landings in the EPO associated to oceanographic events of high and low frequencies could be used somehow as predictors of the high El Niño o La Niña. There is a clear evidence that tuna fish biomass are at higher levels when the PDO is on cold phase (2000–2030) and vice versa on warm phase (1980–1999). The analysis of the skipjack catch per unit effort (CPUE) on floating aggregating devices (FADs) suggests higher CPUE on FADs (around 20 mt set−1) when oceanographic indexes ONI/MEI are below −0.5. Findings of this work suggest that fishing and management of commercial fish must be analyzed under the light of oceanographic conditions.

Comparative study of skipjack tuna <em>Katsuwonus pelamis</em> (Scombridae) fishery stocks from the South Atlantic and western Indian oceans

“…As a result, the quantitative oscillations of the catch reflect more directly the abundance and occurrence of the resource. Indeed, landings declined with an increase in the NOI, similarly to the findings of Ormaza-González et al (2016). Without the use of ENSO indexes, the different attributes of which are not discussed here, Hafiz and Anderson (1994) found that abrupt drops in skipjack catches by the Maldivian fleet were correlated with El Niño years.…”

“…A negative NOI indicates the occurrence of El Niño, while the opposite is associated with La Niña. Median yearly catch values were calculated for the time series and then plotted against the NOI indices for the same year, based on the methodology proposed by Ormaza-González et al (2016). Polynomial regression curves were obtained using locally estimated scatterplot smoothing (LOESS), and R-squared values were calculated from the curve parameterization.…”

Low mercury, cadmium and lead concentrations in tuna products from the eastern Pacific

“…Around 44 % (2009–2016) of tuna captured in the eastern Pacific Ocean is skipjack ( Ormaza-González et al., 2016 ; IATTC, 2018 ), particularly along the equatorial line (outside of marine reserves) that roughly covers from 80–150W, 10N–20S ( Figure 3 ). In this area the biogeochemistry de Hg, Cd and Pb has not been determined yet, however, concentrations of some ocean regions can be found in the literature.…”

Coastal El Niño 2017 or Simply: The Carnival Coastal Warming Event?

“…Environmental impact is huge in terms of diluvial rain episodes [3], release of gases to the atmosphere as their solubility decreases because the sea surface temperature (SST) increases nutrient depletion [4] and reduction of photosynthesis [5]. The whole marine trophic chain is negatively affected: this include important fish stocks as small and big pelagic fish [6,7]. El Niño [8,9] is a relatively low frequency (inter-annual) and non-cycled oceanographicatmospheric coupled process whose definition is referred to the area Niño 3.4 ( Figure 1).…”