Cheney, B.J., Thompson, P.M. & Cordes, L.S. (2019) Increasing trends in fecundity and calf survival of bottlenose dolphins in a marine protected area. Scientific Reports.
Estimates of temporal variation in demographic rates are critical for identifying drivers of population change and supporting conservation. However, for inconspicuous wide-ranging species, births may be missed and fecundity rates underestimated. This paper addresses this issue by introducing a novel robust design multistate model to investigate changes in bottlenose dolphin fecundity and calf survival. The model allows for uncertainty in breeding status, and seasonal effects. This study presents a rare example of empirical evidence of a positive trend in reproduction and survival for a cetacean population using a Marine Protected Area.
Cheney, B., Thompson, P.M., Ingram, S.N., Hammond, P.S., Stevick, P.T., Durban, J.W., Culloch, R.M., Elwen, S.H., Mandleberg, L., Janik, V.M., Quick, N.J., Islas-Villanueva, V., Robinson, K.P., Costa, M., Eisfeld, S.M., Walters, A., Phillips, C., Weir, C.R., Evans, P.G.H., Anderwald, P., Reid, R.J., Reid, J.B. and Wilson, B. (2013) Integrating multiple data sources to assess the distribution and abundance of bottlenose dolphins Tursiops truncatus in Scottish waters. Mammal Review.
The distribution, movements and abundance of highly mobile marine species such as bottlenose dolphins are best studied at large spatial scales, but previous research effort has generally been focused on relatively small areas, occupied by populations with high site fidelity. In Scotland, the Moray Firth Special Area of Conservation has provided an important focus for conservation of bottlenose dolphins, however previously little was known about their broad scale distribution and abundance. This paper explores how data from multiple sources can be integrated to build a picture of the contemporary ranging patterns and abundances of mobile species.
Barbara Cheney’s Mammal Review paper presents the first comprehensive assessment of the distribution, movements and abundance of bottlenose dolphins in the inshore waters of Scotland. Historical data was reviewed, new collaborative studies were developed and data was integrated from ongoing photo-identification studies. The majority of sightings of dolphins were concentrated on the east and west coasts, but records were rare before the 1990s. A Bayesian multi-site mark-recapture model was used to estimate the size of two resident populations: one on the east coast from the Moray Firth to Fife, estimated at 195 individuals and a smaller population in the Hebrides, estimated at 45. This analysis also demonstrated that the dolphins off the east coast of Scotland are highly mobile, whereas those off the west coast form two discrete communities. This work suggests that a relatively small number of bottlenose dolphins occur regularly in Scottish coastal waters. On both coasts, re-sightings of identifiable individuals in this area indicate that these dolphins have been using these coastal areas since studies began.
Bailey, H., Parvin, S., Senior, B., Simmons, D., Rusin, J., Picken, G. & Thompson, P.M. (2010) Assessing underwater noise levels during pile-driving at an offshore windfarm and its potential effects on marine mammals. Marine Pollution Bulletin 60: 888-897.
Marine renewable developments have raised concerns over the impact of underwater noise on marine species, particularly from pile-driving. Environmental assessments typically use generic sound propagation models to assess potential impacts, but empirical tests of these models are lacking. As part of the Beatrice demonstration project, we measured pile-driving noise associated with the installation of the jacket sub-structures for the two 5 MW wind turbines that were installed in deep water off NE Scotland.
Helen Bailey's Marine Pollution Bulletin paper presents simultaneous calibrated recordings made close to the development site (100m from the piling operation) and at a series of different distances up to 80km from the site. At 100m, the maximum peak-to-peak sound level was 205 dB re 1 lPa, gradually reducing to background levels 80km away from the site. These measurements indicted that pile-driving noises could be detected by dolphins at ranges of up to 70 km. Comparison of these measured data with predictions from propagation models suggest that the models provide a reasonable estimate of received levels. But evaluation of these data in relation to published noise exposure criteria highlighted the uncertainty over how different marine mammal species might react to these received noise levels. This work has now led to further large-scale studies of behavioural reactions to anthropogenic noise that we are carrying out for DECC.