1. Recording of cetaceans during 1998 operations in UK waters and some adjacent areas, in compliance with the Guidelines for minimising acoustic disturbance to marine mammals from seismic surveys (April 1998), yielded a total of 518 sightings comprising 4,175 individuals. There were only four sightings of seals. The total time spent watching for marine mammals during seismic surveys in 1998 was 15,834 hrs 21 mins.

 

2. The most frequently seen species was the pilot whale. Fin whales, sperm whales, white-sided dolphins, common dolphins and minke whales were also seen in moderate numbers, with lower numbers of other species. Sightings of cetaceans peaked in July, with most occurring in waters to the north and west of the UK, which reflected the location and timing of surveys.

 

3. Allowing for factors such as geographical distribution, seasonal variations in sightings, weather conditions and the power output of the airguns, the sighting rate of all baleen whales combined was found to be higher when the airguns were firing during seismic surveys. It was thought that this could possibly reflect an increased tendency to remain near the water surface during periods of shooting, and thus be more visible. Sighting rates of fin whales, fin/ sei whales, sperm whales, pilot whales, all dolphins combined and white-sided dolphins did not differ significantly with seismic activity.

 

4. After taking account of weather conditions at the time of sighting, fin whales and all baleen whales combined were found to be significantly further from the airguns when they were firing than when they were not.

 

5. More subtle effects of seismic activity were observed in many of the species examined. Feeding was observed more often when the airguns were not firing than when they were firing. More cetaceans were seen heading away from the survey vessel when the airguns were firing, while more were heading towards or in the same direction as the vessel when the airguns were not firing. Positive interactions with the survey vessel occurred less frequently during periods of shooting. Baleen whales were more likely to dive when the airguns were not firing.

 

6. Behaviour indicating a 'startle' response was observed on two occasions when cetaceans were present as the soft-start commenced, once involving pilot whales and once involving a sperm whale.

 

7. Responses of cetaceans to seismic activity were generally less than has been demonstrated in previous years. Low sample sizes may have led to non-significant results. Alternatively, cetaceans may have tolerated seismic activity because it was of some benefit to them to remain in the area. Increased numbers of cetaceans observed feeding in 1998 suggested that the presence of prey in areas subject to seismic activity may have led to an increased tolerance of seismic activity when compared to previous years.

 

8. Sample sizes were too small to permit conclusions to be drawn regarding the effects of site surveys on cetaceans.

 

9. The proportion of seismic surveys during 1998 (in blocks licensed in the 16th and 17th rounds) for which JNCC received both notification and a report was 56%.

 

10. The duration of searches for marine mammals prior to shooting met or exceeded the required minimum of 30 minutes on 88% of occasions when the airguns were used during daylight hours in blocks licensed in the 16th and 17th rounds of offshore licensing. On 35 out of 926 occasions there was no search for marine mammals prior to shooting commencing during daylight hours in these blocks. There were a further 81 instances where the search in these blocks was shorter than the required 30 minutes. Reduced duration of searches was more common in blocks licensed prior to the 16th round of offshore licensing.

 

11. Excluding site surveys, where a soft-start was not always possible, most soft-starts were between 20 and 40 minutes duration. However, 14% of soft-starts in 16th/17th round blocks were either absent or shorter than the required minimum duration of 20 minutes. Absent or short soft-starts occurred much less frequently when dedicated marine mammal observers were on board the survey vessel.

 

12. Dedicated marine mammal observers were found to be more efficient at detecting marine mammals than other personnel - the mean sighting rate of dedicated marine mammal observers was more than seven times higher than that of other personnel.

 

13. Marine mammals were seen within 500 m of the airguns prior to shooting commencing on ten occasions in 16th/17th round blocks, requiring a delay in shooting in order to comply with the Guidelines for minimising acoustic disturbance to marine mammals from seismic surveys. Correct procedures were followed on two of these ten occasions. On the two occasions when correct procedures were followed, dedicated marine mammal observers were present.

 

14. Recommendations for future revisions to the guidelines are made. Such revisions might include a maximum duration of the soft-start, action to be taken if marine mammals are detected during the soft-start, prohibition of unnecessary shooting, extra protection for vulnerable species, and consideration of the effects of time-sharing.