The Relationship between Vessel Traffic and Noise Levels Received by Killer Whales (Orcinus orca)

Abstract

Whale watching has become increasingly popular as an ecotourism activity around the globe and is beneficial for environmental education and local economies. Southern Resident killer whales (Orcinus orca) comprise an endangered population that is frequently observed by a large whale watching fleet in the inland waters of Washington state and British Columbia. One of the factors identified as a risk to recovery for the population is the effect of vessels and associated noise. An examination of the effects of vessels and associated noise on whale behavior utilized novel equipment to address limitations of previous studies. Digital acoustic recording tags (DTAGs) measured the noise levels the tagged whales received while laser positioning systems allowed collection of geo-referenced data for tagged whales and all vessels within 1000 m of the tagged whale. The objective of the current study was to compare vessel data and DTAG recordings to relate vessel traffic to the ambient noise received by tagged whales. Two analyses were conducted, one including all recording intervals, and one that excluded intervals when only the research vessel was present. For all data, significant predictors of noise levels were length (inverse relationship), number of propellers, and vessel speed, but only 15% of the variation in noise was explained by this model. When research-vessel-only intervals were excluded, vessel speed was the only significant predictor of noise levels, and explained 42% of the variation. Simple linear regressions (ignoring covariates) found that average vessel speed and number of propellers were the only significant correlates with noise levels. We conclude that vessel speed is the most important predictor of noise levels received by whales in this study. Thus, measures that reduce vessel speed in the vicinity of killer whales would reduce noise exposure in this population.

Predicting the acoustic exposure of humpback whales from cruise and tour vessel noise in Glacier Bay, Alaska, under different management strategies

“…Cruise ship speed was the dominant factor affecting whale noise exposure in Glacier Bay, as has been reported elsewhere (Houghton et al 2015). The statistical model results demonstrated that greater ship speed explained most of the variation in the increased MSPL, CSEL and CSET metrics.…”

The Grand Challenges in Researching Marine Noise Pollution from Vessels: A Horizon Scan for 2017

“…As discussed, the findings shown in Table 3 appeared to be at odds with the findings of the Horizon scan, see Figure 4. However, when we considered the content of the articles identified, it was notable that although there were a significant number of publications the research effort appears to center around only a few species: for example, killer whales (Erbe, 2002;Morton and Symonds, 2002;Holt et al, 2009;Wieland et al, 2010;Williams et al, 2014b;Samarra et al, 2015;Houghton et al, 2015; and bottlenose dolphins Buckstaff, 2004;Nachtigall et al, 2004;Luis et al, 2014;Bas et al, 2015;Gospić and Picciulin, 2016). Perhaps un-coincidentally these are also two species that we have more knowledge pertaining to their hearing capabilities due to research conducted on captive animals.…”

“…However, the articles we assessed in general also agreed with another of the Williams et al (2014b) findings in that the majority of the papers concentrated on ecological impacts, management, and policy rather than physical interests. For example, Maccarrone et al (2015) and Farcas et al (2016), both considered best practices for assessing marine noise, while studies such as those carried out by Pine et al (2016) and Houghton et al (2015) consider the direct ecological impacts of anthropogenic noise producing activities on specific species and in particular areas. Although some journals such as Marine Mammal Science or JASA may have been more strongly represented than others in our literature search, this could perhaps largely be attributed to the key words used during our search.…”

Noise levels received by endangered killer whales Orcinus orca before and after implementation of vessel regulations

“…The data collection protocol during focal follows is described in detail in Houghton et al (2015). For the current investigation, whale data collection included a date/time stamp, latitude/longitude to determine country (either USA or Canada), and individual ID from photo-ID records to determine age class (either adult or juvenile) and sex (either male or female) variables.…”

“…Given these documented effects and recognized risk factors, federal vessel regulations were established to protect the southern resident population from interference and noise. The regulations, effective in May 2011, make it unlawful for vessels to approach within 400 yards (yd) (366 m) of any killer whale's path or within 200 yd (183 m) from other directions in US waters corresponding to critical habitat (NOAA 2011 A recent related study using digital acoustic recording tags (DTAGs) found that of 8 variables attributed to nearby vessels, the number of propellers and especially operating speed best predicted noise levels received by southern residents (Houghton et al 2015). In the current investigation, we compared received noise levels before and after vessel regulations came into effect, also using DTAG data but involving additional field effort and a separate analysis from that of Houghton et al (2015).…”