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

Abstract

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.

A decade of humpback whale abundance estimates at Bermuda, an oceanic migratory stopover site

“…Detection probability p is likely to vary between years as a function of seasonal survey effort (Marucco et al, 2009;Monnahan et al, 2019). However, in terms of explaining detection probabilities, the number of survey days is a coarse and perhaps naïve estimate of effort, given that a) the number of whales present changes during a season, with a consistent peak in sightings in March and April across all years; and b) the temporal distribution of effort varies between seasons (Figure 2).…”

“…To minimize bias of abundance estimates, analyses may account for heterogeneity in survival and detection, including features such as: transient animals, which are only available within the study system once across the study period (Pradel et al, 1997;Madon et al, 2013); temporal heterogeneity due to variable sighting effort (Marucco et al, 2009;Monnahan et al, 2019); and individual detection heterogeneity (IDH), where detection varies as a function of individual attributes and habitat features (Hammond, 1990;Cubaynes et al, 2010). CR methods have been used to construct humpback whale abundance time series at local, regional, and basin scales (e.g., Barlow et al, 2011;Madon et al, 2013;Monnahan et al, 2019). These have been used to inform conservation status for the global and regional populations (Bettridge et al, 2015;Cooke, 2018) and to inform species management (International Whaling Commission, 2009).…”

Distribuição espacial de avistamentos de baleias jubarte Megaptera novaeangliae (Borowski: 1781) (Cetacea: Balaenopteridae) na zona costeira do Brasil

“…A análise de densidade de Kernel é um método eficaz utilizado para estimar em mapas os padrões de distribuição de avistamentos de cetáceos (Derville et al, 2019;K. Findlay et al, 2020;Monnahan et al, 2019). O mapa plotado (Figura 5), mostra que M. novaeangliae ocorre em todo o litoral, mas concentra-se principalmente nas regiões de Abrolhos e na plataforma nordeste-leste.…”

Active Whale Avoidance by Large Ships: Components and Constraints of a Complementary Approach to Reducing Ship Strike Risk

“…Yet each of these approaches has limitations. Modifying shipping lanes will only be as effective as the spatial persistence of whale aggregations, can require considerable regulatory effort, or may be impractical in narrow straits or for ships arriving into ports of call (Webb and Gende, 2015;Monnahan et al, 2019). Speed restrictions can generate resistance from the shipping industry owing to economic implications of the additional at-sea time that results from lower speeds, particularly when applied over large areas, which may be one reason voluntary reductions in speeds tend to have low compliance (McKenna et al, 2012).…”