Increased proximity of vessels reduces feeding opportunities of blue whales in the St. Lawrence Estuary, Canada

Abstract

Blue whales Balaenoptera musculus occur seasonally in the St. Lawrence Estuary, Canada, where they spend most of their time foraging. Their recurrent presence has stimulated the development of a large whale-watching industry. Here, we examine the effect of vessel distance on blue whale foraging behaviour by measuring changes in surface and diving patterns. Vessels were within 2000 m of blue whales during 70% of 33 follows, and 59% of total observation time. At vessel distances ≤400 m, surface and dive times were on average 49 and 36% shorter, respectively, and the number of breaths taken by the whales was reduced by 51% compared to control observations without vessel presence within 2000 m of whales. The consequent reduction in foraging time was likely greater than 36%, given that transit time is incompressible and foraging depth is dictated by where krill densities are located. We showed that the relative proportion of lost foraging time from vessel exposure increased exponentially with prey depth. Whales were unable to compensate for lost feeding opportunities by increasing diving rate or swim speed, except when feeding within 10 to 15 m of the surface. Our results indicate that preventing vessels from entering within a 400 m radius around blue whales can help reduce the negative effects of marine recreational activities on blue whale foraging.

Defining priority areas for blue whale conservation and investigating overlap with vessel traffic in Chilean Patagonia, using a fast-fitting movement model

“…6 ). This area holds the largest number of human settlements in the NCP and the main port pertaining to the regional capital, Puerto Montt, raising concerns for potential collisions, behavioral disturbance and/or heavy noise exposure 38 , 94 , 98 – 101 for blue whales there. Although, no systematic monitoring or registering protocol exists in this region, local authorities’ statements and the local press have documented at least three large whale mortality events linked to vessel collisions in the NCP (two blue whales and one sei whale), with two occurring nearby Puerto Montt and the other one at CGMC (Fig.…”

“…Vessel collisions with cetaceans have become recognized worldwide as a significant source of anthropogenic mortality and serious injuries 38 – 41 . Empirical work on this issue has been conducted in a few areas and populations, mostly in the northern Hemisphere 32 , 39 , 42 , 43 , with little effort conducted in South America 32 , 44 .…”

Ecological correlates of blue whale movement behavior and its predictability in the California Current Ecosystem during the summer-fall feeding season

“…Blue whale mortality due to ship strikes has been a growing concern for the recovery of the ENP population [28–31], which is currently estimated at 1647 animals (CV = 0.07) [32], and is listed as Endangered under both the USA’s Endangered Species Act and the International Union for Conservation of Nature’s Red List [33]. Recent studies have shown that while actively engaged in feeding, whales may be less responsive to anthropogenic threats such as approaching ships [34] and military sonar operation [35], while the persistent proximity of vessels and shipping noise can result in a reduction in feeding opportunities [36, 37]. Therefore, an ecosystem-wide understanding of whale foraging behavior and its drivers would fill a critical information gap toward mitigating ship strikes and other impacts from interactions with human activities [29, 31, 38, 39].…”

Humpback Whale Movements and Behavior in Response to Whale-Watching Vessels in Juneau, AK

“…Similarly, fin whales (Balaenoptera physalus) off the coast of Maine exhibited higher respiration rates and reduced dive durations, surface durations, and number of blows per surfacing sequence when whale-watching vessels were nearby (Stone et al, 1992). A decrease in IBI during interactions with whale-watching vessels can be of particular concern when it indicates a relative decrease in foraging efficiency, as seen in minke (B. acutorostrata) and fin whales (Christiansen et al, 2013b;Lesage et al, 2017).…”