From Chilean Patagonia to Galapagos, Ecuador: novel insights on blue whale migratory pathways along the Eastern South Pacific

Abstract

BackgroundThe most traditional scheme for migration among baleen whales comprises yearly migrations between productive waters at high latitude summer feeding grounds and warmer waters at lower latitudes where whales calve and mate, but rarely feed. Evidence indicates, however, that large departures from this scheme exist among populations and individuals. Furthermore, for some populations there is virtually no information on migratory pathways and destinations. Such is the case of Chilean blue whales throughout the Eastern South Pacific; hence, the goal of this study was to assess its migratory behavior.MethodsDedicated marine surveys and satellite tagging efforts were undertaken during the austral summer and early autumn on blue whale feeding grounds off Chilean Northern Patagonia (CNP) during 2013, 2015 and 2016. Positional data derived from satellite tags regarding movement patterns and behavior were analyzed using Bayesian switching first-difference correlated random walk models.ResultsWe instrumented 10 CNP blue whales with satellite transmitters and documented individual variation in departure time, northbound migratory routes and potential wintering grounds. The onset of migration occurred from mid/late austral autumn to well into the austral winter. Blue whales moved in various directions, but ultimately converged toward a general NW movement direction along a wide corridor exceeding 2,000 km. Area-Restricted Search behavior was exhibited within fjords and channels of CNP and also South of Galapagos Archipelago (GA) and northern Peru, but never during migration. Interestingly, dive profiles for one whale that reached GA showed a sharp and consistent increase in depth north of 5°S and extreme deep dives of up to 330 m.DiscussionInformation derived from satellite tagged blue whales in this study is the first of its kind off the Eastern Southern Pacific. Our results provide valuable information on their migratory timing, routes and behavior on their northbound migration, particularly regarding the varied migratory plasticity for this particular population. Our results also highlight the first record of two complete migratory paths between CNP and GA and strengthen the hypothesis that GA waters correspond to a potential wintering destination for CNP blue whales. We further hypothesize that this area might be selected because of its biological productivity, which could provide feeding opportunities during the breeding season. Our results suggest that special efforts should be put forward to identify blue whale critical areas and understand key behavioral aspects in order to provide the basis for their conservation on a regional context (i.e., reducing potential ship strike and promote Marine Protected Area (MPA) implementation in Chile, Ecuador and Peru). Indeed, we suggest joint blue whale conservation efforts at the regional level in order to identify and determine potential threats and impacts and, most importantly, implement prospective management actions.

Satellite derived offshore migratory movements of southern right whales (Eubalaena australis) from Australian and New Zealand wintering grounds

“…The deployment of satellite telemetry devices has provided critical information on the distribution, migration and seasonal movements of many species of large whales [28][29][36][37][38][39][40]. Such information is required to assess and manage potential impacts of anthropogenic activities on highly migratory species and to identify potential drivers that may be hindering recovery [10].…”

Occurrence of blue whales (Balaenoptera musculus) in offshore waters of southeastern Brazil

“…Blue whale populations in the Southern Hemisphere were depleted by commercial whaling (IWC (International Whaling Commission) 2006) and their numbers have yet to recover (Branch et al 2004;Branch et al 2007). Furthermore, the species tends to inhabit deep offshore waters during the breeding season (Double et al 2014;Torres-Florez et al 2015;Lesage et al 2017;Hucke-Gaete et al 2018) and the limited cetacean-oriented survey efforts in deep waters of the western South Atlantic (e.g. Di Tullio et al 2016) translates in few chances of blue whale encounters.…”

Body size data collected non-invasively from drone images indicate a morphologically distinct Chilean blue whale (Balaenoptera musculus) taxon

“…Furthermore, hundreds of blue whales have been observed off the coasts of Chile, Peru, and Ecuador during the austral summer when Antarctic and pygmy blue whales are mainly located farther south in or near the Southern Ocean off Antarctica (Williams et al 2011, Galletti Vernazzani et al 2017, which suggests that this area is occupied by another blue whale population with a unique distribution. This distribution may include the southern portion of the eastern tropical Pacific (ETP), as Chilean blue whales migrate from the Gulfo Corcovado to the Galapagos Archipelago during the austral winter (Hucke-Gaete et al 2018, Torres-Florez et al 2015. Using body length measurements collected by whaling operations, Branch et al (2007) found sexually mature Chilean blue whales to be intermediate in size between pygmy and Antarctic blue whales.…”