Biogeographic patterns of Pacific white-sided dolphins based on long-term passive acoustic records

Abstract

Aim

This study investigates the biogeographic patterns of Pacific white-sided dolphins (Lagenorhynchus obliquidens) in the Eastern North Pacific based on long-term passive acoustic records. We aim to elucidate the ecological and behavioural significance of distinct echolocation click types and their implications for population delineation, geographic distribution, environmental adaptation and management.

Location

Eastern North Pacific Ocean.

Time Period

2005–2021.

Major Taxa Studied

Pacific white-sided dolphin.

Methods

Over 50 cumulative years of passive acoustic monitoring (PAM) data from 14 locations were analyzed using a deep neural network to classify two distinct Pacific white-sided dolphin echolocation click types. The study assessed spatial, diel, seasonal and interannual patterns of the two click types, correlating them with major environmental drivers such as the El Niño Southern Oscillation and the North Pacific Gyre Oscillation, and modeling long-term spatial-seasonal patterns.

Results

Distinct spatial, diel and seasonal patterns were observed for each click type. Significant biogeographical shifts in presence were observed following the 2014–2016 marine heatwave event.

Main Conclusions

Distinct spatial distributions of the two click types support the hypothesis that Pacific white-sided dolphins produce population-specific echolocation clicks. Seasonal and diel patterns suggest spatiotemporal niche partitioning between the populations in Southern California. Interannual changes, notably initiated during the 2014–2016 marine heatwave, indicate climate-driven range expansions and contractions related to gradual tropicalization of the Southern California Bight.