Haul-out patterns and effects of vessel disturbance on harbor seals (Phoca vitulina) on glacial ice in Tracy Arm, Alaska

Abstract

Abstract-Tidewater glacial fjords provide important habitat for breeding harbor seals (Phoca vitulina) that rest, give birth, and nurse pups on icebergs. These fjords also attract tourist vessels that potentially disturb seals. In May and June during 2001-2006, we documented seal abundance, pupping phenology, and seal-vessel interactions in Tracy Arm, a glacial fjord in southeastern Alaska. We used randomized observations to determine the frequency at which seals entered the water in the presence and absence of vessels, and we estimated the reaction distances of seals to approaching vessels. Mean daily vessel counts varied from 10.2 (2001) to 2.0 (2006) (range: 1-33). Tour and power vessels were the most common types of vessels, but seals were most sensitive to cruise ships and kayaks. The odds of a seal entering the water were higher when vessels were present (>2 times) or within 100 m (3.7 times), and when a pup was present (1.3 times). The baseline, undisturbed, rate of seals entering the water was 0.06 (95% CI: 0.05-0.08) per 10 min. Seal births occurred during 30 May-25 June and peaked (4-8 per day) during 7-13 June. The maximum pup count (408) was observed on 24 June. Harbor seal fitness in Tracy Arm may be reduced by vessel disturbances during breeding and pupping.

Post‐disturbance haulout behaviour of harbour seals

“…Indeed, time-lapse photography indicated that at the two focal haulout sites no boat activity other than that used during trials caused animals to flush into the water, suggesting that seals in the Sound of Islay are not currently exposed to disturbance by boats that would be of concern. It may be that harbour seals in the Sound of Islay are already habituated to existing levels of boat traffic, as observed in other studies (Johnson & Acevedo-Gutierrez, 2007;Mathews et al, 2016).…”

“…It may be that harbour seals in the Sound of Islay are already habituated to existing levels of boat traffic, as observed in other studies (Johnson & Acevedo-Gutierrez, 2007;Mathews et al, 2016). The type and frequency of disturbance that seals were exposed to during trials represents the extreme scenario that all approaches by Transition probability (i.e.…”

Fractal analysis provides new insights into the complexity of marine mammal behavior: A review, two methods, their application to diving and surfacing patterns, and their relevance to marine mammal welfare assessment

“…; Isojunno and Miller ; Mathews et al . ). These issues are particularly relevant for marine mammals inhabiting urbanized coastal areas that have increasingly been exposed to a variety of potential human disturbances (Kelly et al .…”

“…All these disturbances have critical implications in terms of conservation of marine mammals (see Wartzok et al 2003, Trathan et al 2014) because even short-term behavioral responses to disturbance could have long-term consequences at both the individual and population levels (Bejder et al 2006, Lusseau andBejder 2007). Besides, these disturbances have widely been shown to impact a range of marine mammal species (Lessage et al 1999;Williams et al 2002aWilliams et al , b, 2006Scheidat et al 2004;Patenaude et al 2006;Hodgson and Marsh 2007;Brandt et al 2011;Andersen et al 2012;Thompson et al 2013;Isojunno and Miller 2015;Mathews et al 2016). These issues are particularly relevant for marine mammals inhabiting urbanized coastal areas that have increasingly been exposed to a variety of potential human disturbances (Kelly et al 2004), including the increase in the occurrence of recreational motorized vessels (Buckstaff 2006), recreational fishing (Powell and Wells 2010), dolphin watching (Mustika et al 2015) and swimwith-dolphin tourism (Peters et al 2013) over the last two decades (McCarty 2004, O'Connor et al 2009).…”

Harbor seal use of glacier ice and terrestrial haul‐outs in the Kenai Fjords, Alaska

“…; Mathews et al . ). Even in Glacier Bay, where vessel traffic is prohibited in Johns Hopkins Inlet during the pupping season and restricted at other times, and other human activities have been curtailed (including most commercial fishing and subsistence harvests of seals by Alaska Natives) numbers of seals in Glacier Bay declined, indicating the involvement of other factors (Womble et al .…”