The safety zone for this survey was very large (7.7 km) so while the airguns were firing our visual watches consisted of rotation between Big Eyes and naked eye/small binoculars every 15 minutes to ensure we didn’t tire from constantly looking through binoculars. We also utilized a PAM (Passive Acoustic Monitoring) system (CIBRA Workstation) to acoustically detect marine mammals. We listened for marine mammal calls and kept watch for those out of our hearing range using the PAM monitor at the PAM station, which shows the sound spectrograph, in the main lab. Once the guns were at the full sound level we did not need to clear the area again, unless they were shut down due to a marine mammal sighting or they were turned off for more than 9 minutes i.e. for maintenance, but we maintained watch of the area to ensure no marine mammals entered the safety zone. Our full watches consisted of 9 hours of visual and PAM spread throughout the day which meant we spent a lot of time running up and down between the tower and the main lab. To entertain myself when I wasn’t on watch I usually checked my email on the very slow internet connection, read or watched a movie in the ship’s theatre.
One of a pair of hitchiking wrens who appear to have come offshore with us from the coast
The deck crew busy cleaning around the stacks in rolling seas!
John and Meghan on visual watch
Joe on visual watch
The sunsets were beautiful when the fog and clouds cleared!
Moonrise at Endeavour MPA
And another beautiful sunset!
The MMO tower at sunset
The Big Eyes...at sunset!
Fortunately for the science crew we didn’t need to shut down the airguns due to sightings; the guns functioned well throughout the survey and we had no marine mammal sightings. This was good because it meant that no marine mammals were likely within range of the 160 dB zone of the airguns but it is possible that our lack of sightings was also due to behavioural avoidance of the area (paper on impacts of anthropogenic noise). In addition to following mitigation measures set by both the Canadian and US government August and September were chosen as survey months because it is the time of year endangered species, such as the Blue Whale (Balaenoptera musculus), would be least likely to occur in the area. In fact, one of the science techs with Scripps showed me some interesting data. Normally, he extracts whale calls from hydrophone recordings of the area, from the NEPTUNE project, to hear earthquakes but decided to do the opposite and remove earthquake sounds to listen for whale calls. From that data he has found that blue and fin whale calls in the area occur from October through the winter; which means it was very unlikely there were Endangered blue whales or Threatened fin whales (Balaenoptera physalus) around the MPA during the survey.
Although we had no marine mammal sighting during the survey we did have some sightings of other wildlife; we saw a few more sunfish (Mola mola), on a couple of the calmer days we could see Blue sharks (Prinocae glauca) swimming underwater or at the surface near the ship and a Peregrin Falcon (Peregrinus falco) stayed around the ship for a day. We even saw it attack and kill another bird, which we think was a petrel, and eat it while in flight around the ship!
Above 4 photos: we were lucky to have a juvenile peregrine falcon (Falco peregrinus) join the ship for a day...which made things more interesting for us in the MMO tower!
John and Megan on the old heli-deck. The airgun array can be seen being towed behind the ship.
Above 4 photos: our Peregrine friend caught another bird a ways out from the ship and proceeded to circle us while eating it in flight!
What else is there to say...the beautiful moon
Another beautiful sunset
Above 3 photos: on a rare flat calm day we had a few Blue sharks (Prinocae glauca) swimming at the surface near the ship
During survey time the crew and science techs were also lucky enough to learn more about the research being conducted by the PIs and each of them gave us a talk about their research (info on Doug Toomey’s research, info on William Wilcock’s research).
From William Wilcock’s website (see link above) this survey was designed to:
“...image the 3-D seismic structure of the crust and topmost mantle along an 80-km-long section of the Endeavour ridge. The experiment will image four targets: (1) crustal thickness variations within 25 km of the axial high (0 to 900 kyr); (2) the 2-D (i.e., map view) structure of the uppermost mantle beneath the spreading axis; (3) the 3-D structure of the crustal magmatic system and (4) the detailed 3-D, shallow crustal thermal structure beneath the Endeavour vent field. The results of imaging will define the recent history of magma supply, the pattern of melt delivery from the mantle to the crust and the structure and segmentation of the subseafloor magmatic and hydrothermal systems.”
thank you for posting these beautiful pictures, and for your articulate commentary regarding this particular study. What is your opinion about all this?
ReplyDeleteIt seems, for example, strange to read your own description of a scientist telling you about using seismic devices to determine that whales are not present until October. But you and others stood in nine hour shifts gazing at the wine dark see, scanning the horizon for whales that, it seems, you knew also would not be there. That tower standing over the middle of the boat—it seems all kinda silly, much ado about not(h)ing), no?
Thanks for your comment Denny and I'm glad you appreciated the posting. Sorry it has taken me a while to reply…I was at the Marine mammal conference in Quebec last week and am now visiting family on the east coast of Canada. In terms of my opinion on these mitigation measures, well to be honest I'm still fairly new to seismic mitigation and am still sorting out my thoughts. Of course there's no denying that seismic exploration would impact on marine life but the extent of that impact and the effectiveness of mitigation is still in the development stage. After the airguns were turned off I was tempted to think that all the sightings occurred because the seismic was shut down but after discussing this with an MMO colleague (who has done ship based marine mammal surveys for 36 years) I realized that it is a very complex issue and there are a lot of variables, such as weather and observer experience, that need to be accounted for. The sightings that occurred the day after the guns were shut down were likely more a result of the calm sea state rather than the lack of airguns although the lack of seismic activity may have contributed. Typically most marine mammal research surveys have fewer sightings data, and as a result remove it, when the sea state is greater than a Beaufort 3 (scattered white caps). We also had some nearly, equally calm days with no sightings after the airguns were turned off.
ReplyDeleteSightings rates are also species dependent because airgun frequency is not necessarily in the hearing range of many marine mammals. During other surveys MMOs have observed some species actually approaching the ship when seismic airguns are in operation.
When dealing with environmentally sensitive issues managers and scientists prefer to take the precautionary approach; this would be the main reason for all this visual and acoustic effort even if it seems excessive. Although the blue and fin whale recordings suggested very low or no presence of these whales at this time of year, this year could have been an exception and it is important to consider that variation. We also need to account for the fact that detectable marine mammals may not always be vocalizing and detections could have be missed in previous years. In addition, the acoustic data used to detect the blue and fin whales only detected low frequency calls so we need to account for other marine mammal species that communicate at higher frequencies, but still within airgun range.
Take care and I hope that answers your question about all this search effort seeming to be for nothing!
ah, yes, all this is well said (I didn't find these later posts in the October archive at the time I commented on an earlier one!)
ReplyDeleteFrom all indications, whales stay away if they need to/want to. so even if you had higher Beaufort seas some days and couldn't easily see the full 7km zone, chances are they stayed a healthy distance away.
I look forward to more reports like these from you as your Whale Nerd life continues to unfold!
Jim Cummings, http://AEInews.org