Sarah J. Dolman

Comparative Review of the Regional Marine Mammal Mitigation Guidelines Implemented During Industrial Seismic Surveys, and Guidance Towards a Worldwide Standard

Marine mammals rely on sound for all of the fundamental biological and ecological aspects of their lives including navigation, prey location and capture, predator avoidance, and communication (including during migration and reproduction). There is increasing concern regarding the potential effects of the airgun sound produced during geophysical seismic surveys on marine mammals. Airgun arrays typically produce high amplitude sound with source levels in the region of 220–248 dB re. 1 μPa @ 1 m. The acoustic output has highest energy at relatively low frequencies of 10–200 Hz, which overlaps extensively with the low frequency sound produced by baleen whales in the 12–500 Hz bandwidth. Airgun arrays may alsoproduce significant highMarine mammals rely on sound for all of the fundamental biological and ecological aspects of their lives including navigation, prey location and capture, predator avoidance, and communication (including during migration and reproduction). There is increasing concern regarding the potential effects of the airgun sound produced during geophysical seismic surveys on marine mammals. Airgun arrays typically produce high amplitude sound with source levels in the region of 220–248 dB re. 1 μPa @ 1 m. The acoustic output has highest energy at relatively low frequencies of 10–200 Hz, which overlaps extensively with the low frequency sound produced by baleen whales in the 12–500 Hz bandwidth. Airgun arrays may alsoproduce significant high

Comparative review of marine mammal guidance implemented during naval exercises.

This article reviews the types and effectiveness of marine mammal mitigation measures used during some naval activities worldwide. The three main standard methods used to mitigate the potential impacts of naval sonar sound on marine mammals are (1) time/area planning (of exercises/active sonar use) to avoid marine mammals; (2) implementation of operational procedures (e.g. soft start - where sound levels are gradually increased over time); and (3) monitoring of animals for the purpose of maintaining an exclusion zone around the sound source. Suggestions towards a minimum worldwide mitigation standard are made.

Spatio-Temporal Restrictions as Best Practice Precautionary Response to Ocean Noise

Despite the increasing reports of atypical cetacean strandings and subsequent deaths that have been associated with military sonar, the mechanism of injury remains unknown. While this may remain the case for some time, there is emerging evidence regarding the nature of the damage and the sound levels that induce it. It is increasingly apparent that tissue damage and strandings may be induced at received sound levels that are lower than had previously been anticipated. In particular, at levels lower than those that can induce auditory damage, and, most significantly, lower than those currently being used as an acceptable level for management guidance.

Fulfilling EU Laws to Ensure Marine Mammal Protection During Marine Renewable Construction Operations in Scotland.

Large-scale offshore renewable energy infrastructure construction in Scottish waters is anticipated in coming decades. An approach being pursued, with a view to preventing short-range marine mammal injury, is the introduction of additional noise sources to intentionally disturb and displace animals from renewable sites over the construction period. To date, no full and transparent consideration has been given to the long-term cost benefits of noise reduction compared with noise-inducing mitigation techniques. It has yet to be determined if the introduction of additional noise is consistent with the objectives of the EU Habitats Directive and the Marine Strategy Framework Directive.

Harbour porpoises (Phocoena phocoena) and minke whales (Balaenoptera acutorostrata) observed during land-based surveys in The Minch, north-west Scotland

The waters off north-west Scotland are known to provide important habitat for the harbour porpoise ( Phocoena phocoena ) and the minke whale ( Balaenoptera acutorostrata ). Between October 2008 and April 2011, systematic land-based surveys were carried out to assess the seasonal occurrence, group size and group behaviours of both species in a study area located off Melvaig, near Gairloch. Data were collected on 47 separate days, with a total of 4543xa0minutes of survey effort (in sea states ≤3) recorded during the spring months and 8204xa0minutes of effort during the autumn. A total of 189 sightings of marine fauna were recorded, comprising 126 cetacean sightings, 50 seal sightings and 13 sightings of basking sharks ( Cetorhinus maximus ). Six species of cetacean were identified, with most sightings comprising harbour porpoise (Nxa0=xa072) or minke whale (Nxa0=xa038). Harbour porpoise abundance was higher in autumn than in spring and there was a variation between years in numbers of minke whales sighted. In porpoises, sea state and cloud cover both influenced sightings and increasing sea state influenced survey area. Foraging behaviour was exhibited in 13% of harbour porpoise sightings and 34% of minke whale sightings. Results demonstrate a regular occurrence of harbour porpoises and minke whales in nearshore waters off Gairloch. Densities are comparable to boat surveys in the region and so support the use of land-based watches as a potential longer-term monitoring method for these species in coastal waters. Given the regular use of this area by these two European Protected Species, as well as the occurrence of a range of human activities potentially affecting them in the region, it may be appropriate to consider protecting this area for their conservation.

A note on the unprecedented strandings of 56 deep-diving whales along the UK and Irish coast

In the first seven months of 2008, eighteen Cuviers beaked whales ( Ziphius cavirostris ), four Sowerbys beaked whales ( Mesoplodon bidens ), five unidentified beaked whales and twenty-nine long-finned pilot whales ( Globicephala melas ) were reported stranded in the UK and Ireland. Decomposition of those animals investigated puts the predicted time of death at mid-January. Concerns that an unusual mortality event had taken place prompted further investigations. Most carcasses were too decomposed for necropsy. A summary of findings is presented here. Although the initial stranding of five Cuviers beaked whales in Scotland shared some similarities with atypical mass stranding events linked in time and space to mid-frequency naval sonars, there were two important differences with the remaining strandings during this period. First, the geographical range of the event was very wide and second, the strandings occurred over a prolonged period of several months. Both of these factors could be related to the fact that the mortalities occurred offshore and the carcasses drifted ashore. The cause(s) of this high number of strandings of mixed offshore cetacean species during this period remain undetermined.

THE WORLDWIDE EXTENT OF SEISMIC EXPLORATION, 1994–2004

the ships may alter course without constraint. Additional mitigation under these circumstances may be required. Clearly, further research is required to better understand the mechanisms of how sonar might potentially impact on beaked whales. This remains unclear despite a number of theories. Until this time, the RAN will continue to use a precautionary approach. The consultative and innovative approach used by the RAN in managing potential marine mammal interactions demonstrates that meeting environmental compliance standards is possible without undue impact on training. It demonstrates that both the environment and the Navy can be winners.