Accidental Whale Portraits And Soundtraps!

We have had some pretty good whale days over the last week. Alongside getting fin shots I have also once or twice lucked out and managed to get some beautiful whale shots as they have surfaced to breathe. Two of my favourites are below. It was pure luck that I managed to get the images in such clear focus that they almost don’t look real. The moment frozen in time with the tidal wave of water is pretty awe worthy I think!

KW_20150226_BeautifulWater_WM

Soundtrap

SoundTrap by Ocean Instruments New Zealand. Image: Ocean Instruments New Zealand

Alongside photo-id images we are trying to gather acoustic recordings. A new tool which we have been using for that this week is a soundtrap.This is an autonomous underwater recording device that we have rigged up to allow us to tow it behind the vessel when we move at slow speeds. This is in a new attempt to get recordings of the killer whales acoustically communicating without having to stop the vessel. We are excited to listen to and view our recordings to see if we have picked up any calls. So far it seems that flow (water) and engine noise are at a minimum when recording in out current set up which is very good news for picking up biological sounds.

I’ll leave you with one final image that is a later image from a different individual of the same pod during the same surfacing This individual looks like they are wearing a bubble mask!

KW_20150226_BeautifulWater_2_WM

Many thanks to Naturaliste Charters and Riggs Australia for allowing us space on their vessels. Further thanks to the Centre for Marine Science and Technology at Curtin University for equipment loan and support.


You can also follow along on the Deep Blue Conversations Facebook Page. I post interesting articles related to marine conservation, share awesome stories as well as photos from the marine conservation and environmental world in general. Come on over and have a look!

Impact of Marine Dredging on Marine Mammals – New Paper

Fascinating new paper out reviewing the likely impacts that dredging may have on marine mammals. The paper by Dr. Victoria Todd and colleagues can be read here.

It is a great review of the effects both positive and negative that dredging can have on marine life. I like that is has done this as I would have gone all BAD, BAD, BAD! However there are some positives. The paper focuses mainly on marine dredging although it is important to remember it also occurs in rivers and lakes.

Marine Dredger. Photo: United States Environmental Protection Agency (EPA) (http://water.epa.gov)

Marine Dredger. Photo: United States Environmental Protection Agency (EPA) (http://water.epa.gov)

Start with the bad…

The paper delves into the direct and indirect impacts of dredging on marine mammals and the potential severity of those.

The direct impacts are interactions that cause physical injury to mortality. These include Noise Pollution, Turbidity and Collision.

Noise pollution occurs at lots of different levels and in areas that are already heavily trafficked. Our knowledge of the hearing range of marine mammals is still limited so we can not be sure of all the effects. However it is possible that the noise emitted could cause masking of marine mammal calls particularly cetaceans. I talk about this more in this blog post. The effects are likely to be over the short to medium term and occur as behavioural changes such as area avoidance and call masking. All this will occur concurrently with other industrial activities so it is hard to tease out the specific impacts of just dredging.

In regards to collision, the slow speed of active dredgers means that there is low risk of collisions taking place especially if managed well and avoids critical habitat and calving areas. The bigger risk would be when dredging vessels are in transit but if this is occurring in an already heavily transmitted area as tends to be the case for dredging this won’t significantly add to the risk already in place.

The seabed disturbance caused by dredging leads to increased turbidity and sediment suspension. However, many marine mammals are use to turbid environments and limited vision is not an issue even for species that do not use echolocation for prey detection.

Indirectly marine mammals can be affected by changes to their environment and also to prey availability due to dredging. The paper lists the possibilities as:

  • Entrainment,
  • Habitat degradation,
  • Noise,
  • Remobilization of contaminants,
  • Sedimentation, and
  • Increases in suspended sediment concentrations.

Entrainment is the removal of species from their environment and while no data is available on this impact on marine mammals it has been noted that it can affect their prey species by removing them and their eggs along with the sediment. Therefore along as dredging is restricted during important egg and larval stages of prey species then effects are unlikely to be detrimental.

The degradation of marine habitats is something that I would be really worried about as dredgers go about their process especially since “45 case studies worldwide found that 21 023 ha of seagrass beds were lost as a result of 26 dredging projects over a 50-year period”. Sirenians (e.g. manatees and dugongs) are entirely dependent on seagrass beds while other marine mammals utilise them for prey and they are an important habitat for prey species. However, from this review I am enlightened to the fact that due to mitigation measure the impact on seagrass habitats has been reduced and that as long as mitigation is followed and planning is conducted with care the effects are minimal.

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The WA Shark Cull Has To End

It was all over the news for a while and Facebook and probably your Twitter feed too. The Western Australia (WA) shark cull.

It all started because of a high number of shark attacks in quick succession in WA, causing the government to act quickly and rashly, imposing a trial lethal drum-line programme. Now after the end of the trial period (January 25th – April 30th 2014) the WA government are proposing to extend it to a 3-year lethal drum line programme. This time however they need to pass a federal environmental assessment unlike the trial which was granted temporary exemption under national environmental law because it was apparently deemed in the “national interest” of protecting public safety.

The outcomes from a similar 16 year lethal long-line programme operated in Hawaii (1959-1976) were ignored. At the end of the Hawaiian cull scientist concluded that it made no difference to shark attacks. It didn’t matter though as the Australian government decided to go ahead with the 13 week trial despite all the facts stacked against them. Using baited drum lines there were horrific scenes as sharks were baited and hooked then dragged out to sea alive and killed.

Over the 13 week trail 172 sharks were killed 163 of these were tiger sharks (Galeocerdo cuvier) while zero were white sharks (Carcharodon carchariasthe species believed to be those involved in the recent attacks.

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