Evidence of spatial structuring of eastern South Pacific humpback whale feeding grounds

Humpback whales wintering in tropical waters along the Atlantic and Pacific coasts of the South American continent are thought to represent distinct populations or “stocks.” Here we present the first analysis of genetic differentiation and estimates of gene flow between these breeding stocks, based on both mitochondrial DNA (mtDNA) control region sequences (465 bp) and 16 microsatellite loci from samples collected off Brazil (n = 277) and Colombia (n = 148), as well as feeding areas near the western Antarctic Peninsula (n = 86). We found significant differentiation between Brazilian and Colombian breeding grounds at both mtDNA (FST = 0.058) and microsatellite (FST = 0.011) markers and corroborated previous studies showing genetic similarity between humpbacks from Colombia and those from Antarctic Peninsula feeding areas. Estimates of long‐term gene flow between Brazil and Colombia were low to moderate, asymmetrical, and mostly mediated by males. Assignment procedures detected some cases of interchange and individuals of admixed ancestry between breeding grounds, indicating limited mixing of individuals between these stocks. Overall, results highlight the differentiation of humpback whale breeding populations with adjacent feeding grounds. This appears to be a remarkable example of fidelity to seasonal habitat in the absence of any contemporary barriers.

supporting

confidence: 83%

“…, Acevedo et al . ), the heterogeneity between the wintering areas of this stock, and a higher similarity between Magellan Strait and the northernmost breeding areas (Acevedo et al . , Capella et al .…”

Section: Discussionmentioning

confidence: 99%

Genetic differentiation between humpback whales (Megaptera novaeangliae) from Atlantic and Pacific breeding grounds of South America

Cypriano-Souza

Engel

Caballero

et al. 2016

“…Currently, three discrete summer feeding areas have been identified for stock G (Acevedo et al . ) and include historically the waters of the western Antarctic Peninsula (Kellogg , Mackintosh ) and two new sites along the western coast of South America, the Magellan Strait, (53°30′S; Gibbons et al . , Acevedo ) and the Corcovado Gulf (43°53′S; Haro , Hucke‐Gaete et al .…”

mentioning

confidence: 99%

Population trends for humpback whales (Megaptera novaeangliae) foraging in the Francisco Coloane Coastal‐Marine Protected Area, Magellan Strait, Chile

Monnahan

Acevedo²,

Hendrix³

et al. 2019

In 2003 a feeding aggregation of southeastern Pacific humpback whales (Megaptera novaeangliae) was reported in the Magellan Strait. While Chile established its first marine national park in the Strait to protect humpback whale habitat, fatal ship strikes remain a concern because of overlap with a busy shipping lane. To better understand population risk, we estimated abundance and survival for this population using Bayesian robust‐design mark‐recapture models fit to photographic data from 2004 to 2016. Overall, the model estimated a total of 204 whales (95% CI: 199–210) during the last 12 yr, and 93 (95% CI: 86–100) in the 2016/2017 austral summer. The population grew at 2.3% (CI: 2.1%–3.1%), an annual increase of two whales. Annual survival (including calves) was estimated at 0.892 (CI: 0.871–0.910). Our results corroborate a persistent feeding population, but one that is increasing relatively slowly. Owing to its vulnerability stemming from its small size, coupled with significant overlap with a busy shipping lane, we argue this subpopulation is at significant risk from ship strikes and may be one of the few populations where anthropogenic mortalities could regulate population dynamics. We therefore encourage continued monitoring via photographic mark‐resighting surveys, and analyses explicitly investigating potential population‐level ship strike effects.

“…, Acevedo et al . ) and genetic structuring between breeding and feeding areas of BSG (Félix et al . ).…”

mentioning

confidence: 99%

Migratory preferences of humpback whales between feeding and breeding grounds in the eastern South Pacific

Acevedo

Aguayo‐Lobo

Allen

et al. 2017

Latitudinal preferences within the breeding range have been suggested for Breeding Stock G humpback whales that summer in different feeding areas of the eastern South Pacific. To address this hypothesis, humpback whales photo‐identified from the Antarctic Peninsula and the Fueguian Archipelago (southern Chile) were compared with whales photo‐identified from lower latitudes extending from northern Peru to Costa Rica. This comparison was performed over a time span that includes 18 austral seasons. A total of 238 whales identified from the Antarctic Peninsula and 25 whales from the Fueguian Archipelago were among those photo‐identified at the breeding grounds. Our findings showed that humpback whales from each feeding area were resighted unevenly across the breeding grounds, which suggests a degree of spatial structuring in the migratory pathway. Humpback whales that feed at the Antarctic Peninsula were more likely to migrate to the southern breeding range between northern Peru and Colombia, whereas whales that feed at the Fueguian Archipelago were more likely to be found in the northern range of the breeding ground off Panama. Further photo‐identification efforts and genetic sampling from poorly sampled or unsampled areas are recommended to confirm these reported connectivity patterns.