3.2.1 Evaluation for nature conservation

Figure 15.   The distribution of bottlenose dolphin sightings within Cardigan Bay

(Courtesy of SeaWatch Foundation Sightings Database)

The cSAC encloses the areas thought to contain physical and biological factors essential for the life of the bottlenose dolphins. However, bottlenose dolphins in Cardigan Bay may have a wide range and this is certainly known to extend beyond the boundary limits of the cSAC. Identified individuals known to occur within the site have been recorded further up and down the coast. Bottlenose dolphins are also occasionally seen well out in the Irish Sea and also over the intertidal zone when the tide is in [68].

Whilst the range of the population may be quite large, research suggests that the population size is not. Following a five year photographic study in Cardigan Bay in the early 1990’s, the population was estimated at about 127 individuals [69]. Populations of this size are generally acknowledged to be small and vulnerable to impacts. A population model developed for a similar number of bottlenose dolphins in the Moray Firth, Scotland, predicts that this apparently isolated Scottish population is declining.

This and other population viability analyses have demonstrated that adult survival has the greatest impact on population persistence. The loss of a only few individuals from a population of this size, particularly adult females, would represent a significant reduction in the capability of such a population to maintain itself in the long term [70].

3.2.1.2    Diversity

Whilst this site has been selected for a single species, the bottlenose dolphins, it does support a diverse variety of other marine species and habitats including many of considerable conservation value [71].

3.2.1.3    Naturalness

The naturalness of the Cardigan Bay bottlenose dolphins is a difficult value to assess. In comparison with terrestrial habitats, the marine environment is, in general, far more natural. One means of assessment is to consider the degree to which non-natural processes are present. Considering Cardigan Bay in these terms would indicate that it is quite natural; there is little in the way of industry, fishing activity is not highly intensive and most shipping movements occur outside the bay. There is not regular swimming with the dolphins nor are they fed. However, some human interaction with the dolphins is clearly significant and it would be naive to assume that it was not resulting in some change, however small, to their behaviour or lifestyle.

Analyses of tissues from dead strandings in the late 1980’s and early 90’s, have shown that the concentrations of some anthropogenically derived pollutants, including heavy metals and organochlorines (such as some polychlorinated biphenyls), were unnaturally high in the Bay’s bottlenose dolphins [72].

As predators at the top of food chains, the bottlenose dolphins are heavily reliant on a high degree of naturalness in their surrounding environment; impacts lower down in the food chain may be reflected, even magnified, in the condition of the bottlenose dolphins.

Maintenance of the current level of naturalness would require the prevention of ny further increase in anthropogenic influences on the bottlenose dolphins. An improvement in naturalness would require a reduction in the current levels of anthropogenic influences on the bottlenose dolphins.

3.2.1.4    Rarity

Although the bottlenose dolphin is not considered rare its status world wide is not known. Whilst not common in abundance, it is a cosmopolitan species, widespread in tropical and temperate waters around the world.

3.2.1.5    Fragility

Bottlenose dolphins are vulnerable not only to short term impacts but also to long term cumulative, chronic impacts. Impacts which appear insignificant may, over the long term or in combination with other impacts, result in significant and irreversible damage to the bottlenose dolphin’s status. This is exacerbated by the fact that we are largely unable, with current scientific methods, to detect the effects of impacts on the bottlenose dolphins and their causal links. Successful detection, if possible, is likely to take a considerable period of time unless blatantly obvious. Even if cause and effect have been identified, any management action may well be too late to remedy the situation.

As top predators, bottlenose dolphins are vulnerable to changes in their environment. Small insignificant impacts on what may appear to be an unrelated habitat or community may result in significant impacts on the bottlenose dolphins. In addition, their endearing nature attracts considerable human attention, often resulting in increased disturbance.

The relatively small numbers of bottlenose dolphins in Cardigan Bay makes them fragile to small losses in numbers. The loss of relatively few dolphins, in say a stranding event, may represent a sizable proportion of the overall numbers and significantly reduce the ability of the population to sustain itself.

3.2.1.6    Typicalness

The characteristics of bottlenose dolphin populations around the world are quite varied, from size and diet to habitat preference and extent of home range. Whilst similarities exist with other bottlenose dolphin populations, the dolphins of Cardigan Bay can only be regarded as typical in that they vary in these and other aspects as much as any other dolphin group.

Within the UK the Cardigan Bay dolphins, like those of the Moray Firth in Scotland are clearly special in that the area is constantly in use and the same individuals regularly occur within the same areas.

3.2.1.7    Recorded history

The history of bottlenose dolphins in Cardigan Bay is unclear. During the 1920's and 1930's there were numerous references to bottlenose dolphins in the west Wales area [73]. Strandings records (provided by the Institute of Zoology, Regent's Park, London) for the whole of the Welsh coast show that bottlenose dolphins have been present there since soon after the Natural History Museum (NHM) strandings scheme was initiated in 1913 (with 2 animals stranded in Gwynedd in 1916). Although it has been suggested that this species may not have been present in the area until the late 19th or early 20th century, it is difficult to be sure.

The UK Mammal Society Cetacean Group established recording of voluntary sightings in 1973. This is now maintained by Sea Watch Foundation. Since 1997 a regional copy of the Sea Watch Foundations sightings database has been established within west Wales.

In more recent years a variety of research, some of it long term but mostly short term, has been conducted on the dolphins within the bay. A list of literature pertaining to cetacean related projects conducted within Cardigan Bay is given in Appendix 3.

3.2.1.8    Ecological position

The bottlenose dolphin is a large carnivorous predator and sits at the top of marine food chains within Cardigan Bay. As a result, it is very reliant on the success of the trophic levels beneath it.

As both the dolphin and its prey can be highly mobile, there will be a wide spatial spread of the dolphin’s ecological unit (i.e. the spread of the marine food web and environmental processes on which the bottlenose dolphin depends). This means that impacts some distance outside the Cardigan Bay cSAC may affect the bottlenose dolphins.

It will be important for management decisions to consider potential indirect impacts to the bottlenose dolphins even when the issue at hand may appear unrelated.

3.2.1.9    Potential for improvement or restoration

There is considerable potential to reduce the current levels of anthropogenic impacts to raise the current level of naturalness of both the dolphins and their habitat. This is particularly the case in those areas which are of greatest importance to the dolphins.

Further research is required to identify the costs and benefits of reducing certain impacts. This should include consideration of long term, short term , cumulative and synergistic effects.

[68] Arnold et al (1997); Evans (1992)

Baines, M., Pierpoint, C. And Earl, S. 1997. A Cetacean sightings database for Wales and an evaluation of Impacts on Cetaceans from the Sea Empress Oil Spill, CCW Sea Empress Contract Report No. 227. pp 1-66. ( Re: sightings records since 1928 + records outside SAC + offshore)

[69] Arnold et al (1997)

[70] Sanders-Reed, C.A., Hammond, P.S., Grellier, K., Thompson, P.M. 1999. Development of a population model for bottlenose dolphins. Scottish Natural Heritage Research, Survey and Monitoring Report No. 156, Inverness.

[71] See note in the Preface regarding recent proposed additions to the list of selected features for the site.

[72] Law, R.J. and Allchin, C.R. 1994. Organochlorines in the blubber of bottlenose dolphins (Tursiops truncatus) and harbour porpoise (Phocoena phocoena) from Cardigan Bay (Wales) and the Moray Firth (Scotland). ICES CM 1994/(E+N) 9:8pp.

Law, R.J., Allchin, C.R. and Morris, R.J. 1995. Uptake of organochlorines (chlorobiphenyls, dieldrin; total PCB and DDT) in bottlenose dolphins from Cardigan Bay, West Wales. Chemosphere, 30:547-560.

[73] Evans & Scanlan (1988)