The Bae Ceredigion (Cardigan Bay) Special Area of Conservation (SAC) constitutes an area of importance for the largest population of bottlenose dolphins Tursiops truncatus in the United Kingdom1. Any readers that have been following the #scallopgate discussion on Twitter will know that the Welsh Government is currently considering re-introduction of limited scallop dredging into some new areas of the Bae Ceredigion SAC beyond which they currently operate.

As a brief synopsis, I refer readers to the excellent blog of Sam Andrews :

So where are we now? I would say we are in a bit of a ‘no man’s land’ and stuck between the scientists who say their science is good and the conservationists who say it isn’t. This stalemate is down to a misunderstanding of what the other group is trying to say and the common tendency for humans to have short-sighted baselines. But I believe science has an answer that may help to resolve some of these issues. Let me explain.

Conservationists have been quick to argue that the Bangor University report is defunct because any recommendations based on its findings are starting from a non-natural baseline of what the seabed should be. The scientists involved have since been very open in defending against this ‘shifting baseline’ accusation2. Professor Michel Kaiser, of Bangor University, has on multiple occasions, quite rightly, pointed out that not all environments are biologically rich and diverse and that the ultimate climax community is very much dependent on environmental conditions. Prof Kaiser and other Bangor scientists have stated that owing to the dynamic environment found within the SAC the seabed would never return to a complex and 3D community as one never existed in the first place. The fauna found in these habitats are adapted for a turbulent and storm-ravaged ecosystem and that scallop dredging, if well managed and controlled, will have limited impact upon them.

There has been some suggestion that the seabed within the SAC may be too hard to be a suitable foraging environment in the way that it is for tropical bottlenose dolphins and so any impact on this food resource would have limited effect for the dolphins anyway. However the more robust and scratched rostrum found in the Bae Ceredigion SAC dolphins suggests that in fact they may be uniquely adapted for such a challenge and that it is indeed a key resource, a point that is critical to the conservationists argument. They argue that this food resource is especially important to mothers with calves that have limited ability to hunt fast moving fish and other prey.

Dolphin rostrum comparison
Tropical (left) bottlenose dolphin known for soft sediment feeding and Bae Ceredigion (right) dolphin. Notice the apparently more robust and heavily scratched rostrum of the Bae Ceredigion dolphins. Is this evidence for feeding in a harder sediment? Picture credits: Left – Right – CBMWC

If the scientists are right and the environmental conditions are such that recovery from scallop dredging can happen in less than a year then by extended logic we can deduce that the seabed conditions in Bae Ceredigion SAC now are, minus the effects of the endemic beam trawl fishery, as they were prior to industrialized fishing. I must stress that the effects of beam trawlers on a virgin seabed should not be underestimated but let’s put that aside for now and assume that the effects are minimal compared to those of scallop dredging. If that is the case and the habitat is (nearly) as healthy as it has always been then the top predators of that habitat – in this case the dolphins – should exhibit a stable population, especially if the key food resource for calving mothers (the breeding element of the population) is healthy. Now I understand that we may be foolish to call our marine environment healthy, especially in terms of other fish stocks that may be important food resources to the dolphins at other key life stages or the impacts of water pollution, but let’s not muddy the waters too much here. In a simplified system if our impact is minimal the number of dolphins in the population today will be the same as it was two hundred, three hundred or even a thousand years ago. If this is not the case then the conservationists may have a valid point that our baseline has shifted and the Bae Ceredigion SAC may need more protection, not less.

Fortunately science has given us a way to examine some of these hypotheses, we just have to take a rather different approach. In my opinion the population biology and ecology of the dolphins found in Bae Ceredigion SAC is poorly studied. I didn’t say unstudied or not studied, I mean poorly studied but that is for another post. Current research focusses mainly on photo identification (Photo ID) surveys that allow us to estimate the current size of the population. It gives us no real capacity to estimate past population sizes beyond 1989 (the oldest photo ID records of any real note), in many cases this is not beyond the current oldest living generation. However, modern genetic techniques allow us to do just that. Genetic bottleneck tests allow us to fundamentally examine declines in abundance of a population. In reality they actually test for signals of population decline in the effective population size (Ne) but for cases like the Bae Ceredigion SAC the general effect is still the same. They work by detecting departures from expected values under mutation-drift equilibrium.

Conducting these tests on the Bae Ceredigion SAC dolphins would be relatively straightforward, especially with modern sequencing methods and techniques. Having this information would allow us to infer just what impact man has had on the dolphin population of the SAC and that would have a lot of bearing on not only the current debate but many other future management decisions too such as those about marine renewables or sea defense construction. If the population of these top predators has remained stable for a long time then this would take substantial wind out of the conservationists’ sails. If their population has changed significantly then this would afford us the opportunity to re-examine the effectiveness of the Bae Ceredigion SAC and its management. Either way we can’t move forward without this kind of information.

So what is stopping us? The answer is gaining access to samples. Bottlenose dolphins are highly protected species and taking biopsy samples can only be done under strict regulations and license. If this could be gained the procedure is simple and involves experienced scientists using a crossbow or rifle (hence the title) to take a small skin and blubber tissue sample from dolphins at the surface. This procedure has been shown to have minimal effect on the animal’s wellbeing if done correctly6 and the information that could be gained would be substantial. Furthermore access to tissue samples would allow us to examine more closely the feeding ecology of the dolphins through stable isotope analysis. This would also be useful to the debate as it would give us information on just how important the benthic infauna is to the dolphins as a food resource.

Although it may be too late for this debate owing to political timescales, our data collection strategy must be progressive and must put the dolphins at the heart of the decision making process. We must not be afraid of new ways of approaching a problem and be prepared to cast off old strategies, particularly if we are continuing with a certain approach simply because that is ‘how it has always been done’.



  1. Parsons, K. M., Noble, L. R., Reid, R. J. & Thompson, P. M. Mitochondrial genetic diversity and population structuring of UK bottlenose dolphins (Tursiops truncatus): is the NE Scotland population demographically and geographically isolated? Biol. Conserv. 108, 175–182 (2002).
  2. Will Scallop Dredging in Cardigan Bay be an Environmental Disaster? CFOOD – Science of Fisheries Sustainability at <;
  3. JNCC. Cardigan Bay/ Bae Ceredigion – Special Area of Conservation – SAC – Habitats Directive. at <;
  4. Dayton, P. K., Thrush, S. F., Agardy, M. T. & Hofman, R. J. Environmental effects of marine fishing. Aquat. Conserv. Mar. Freshw. Ecosyst. 5, 205–232 (1995).
  5. Lambert, G. et al. Impact of scallop dredging on benthic communities and habitat features in the Cardigan Bay Special Area of Conservation. Bang. Univ. Fish. Conserv. Rep. No 59 (2015). at <;
  6. Tethys Research Institute. Biopsy sampling and intrusive research. (2013).

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s