Physical and biological drivers of pelagic fish distribution at high spatial resolution in two Patagonian Gulfs

LUZENTI, ELVIO AGUSTÍN; SVENDSEN, GUILLERMO MARTÍN; DEGRATI, MARIANA; CURCIO, NADIA SOLEDAD; GONZÁLEZ, RAÚL ALBERTO; DANS, SILVANA LAURA

FISHERIES OCEANOGRAPHY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2021

1054-6006

The North Patagonian gulfs, Argentina, support an important population of small pelagicfish (SPF) that play a key role in the marine ecosystem. Here, we assessed theseasonal SPF distribution in Nuevo gulf and San Matías Gulf concerning several environmentalvariables and the nautical area scattering coefficient (NASC) of Munidagregaria using generalized additive models (GAMs). We collected biological data by a38/200 kHz echosounder along zigzag transects in all four seasons. The echoes of fishwere separated from other targets using a dB difference algorithm. Then, we calculatedthe mean NASC of pelagic fishes every 0.5 nm. Satellite-derived data were usedto characterize the environment at study sites. GAMs were built in two stages foreach gulf considering all season in a single model in one hand, and each season separatelyin the other one. In the first stage, we modeled the probability of presence as afunction of predictors. In the second stage, we used the NASC of fish as the responsefor presence data only. In general terms, the probability of fish presence increaseswith bottom depth, and the fish density was higher in cold waters and zones withhigher chlorophyll-a concentration. The relative importance of the variables was differentaccording to the season. The formation and rupture of the thermocline and itssubsequent spatial heterogeneity observed in spring and autumn could be importantdrivers of SPF distribution. Squat lobsters? distributions related positively with SPF inSan Matías Gulf summer and negatively in Nuevo Gulf summer.K