Over the past few weeks, Sea Watch Foundation interns have been scanning New Quay harbour with eagle eyes, looking out for dolphins and other marine mammals. Last week saw the disappearance and re- emergence of ‘Stormy’ the solitary common dolphin, who decided to vacate New Quay and travel north. He was briefly seen in Aberystwyth a week ago but has not been since.
This week, we have been noticing certain individuals of the semi-resident bottlenose dolphin population, choosing to come closer into the harbour, and often around the same area between Traeth Gwyn beach and the Cardinal mark. In particular a mother, calf and juvenile have been spotted a number of times. There are a number of possible explanations for this apparent change in behaviour.
Throughout the year, gill nets are put out by recreational fishermen in the harbour. These are closely monitored and checked several times a day. According to local fishermen these are not species specific and can net bass, mackerel and herring; all fish which bottlenose dolphins are known to eat. One of the areas the nets are placed in New Quay is close to the harbour and around the same area that the mother, calf and juvenile have been spotted. It is possible that these dolphins could be attracted to the nets, as it offers an easy food source and ideal place for mother and calf to fatten up! Although some fishing nets are known to pose a threat to the dolphins through by-catch, thankfully since 1990 there is only one proven record of a by-caught bottlenose being washed ashore in Wales (Wildlife Trust 2003). According to UK Cetacean Strandings Investigation Programme (CSIP), very few bottlenose dolphins become stranded, perhaps because of the fact their muscle mass out-weigh’s their air storage capacity, and some therefore end up sinking instead of floating. CSIP also stated they had a ‘possible’ by-caught bottlenose in 2009, but unfortunately as the individual was in a state of moderate to advanced decomposition they were not able to be 100% certain of the species. There are also stories of fishermen catching bottlenose dolphins in Cardigan Bay and letting their carcasses go, so if this activity is indeed taking place, bottlenose dolphins are susceptible to by-catch like any other species. Although by-catch does happen through recreational fishing and with gillnets, most of the fishing in West Wales is potting.
As part of our daily ‘land watch’, Sea Watch interns monitor and record boat and vessel traffic travelling in and out of the harbour, with particular emphasis on interactions between boats and the dolphins. Apart from a few fishing boats, the main traffic is from wildlife tour operators like ‘Dolphin Spotting Boat Trips’ who give the public an ideal opportunity to spot the dolphins from sea. As we are in the low season at the moment, the number of tours and boats in general has been low, and lower still over the past week or so. This could also be a reason why the dolphins are choosing to venture closer. Boat traffic, particularly motor boat noise, has been reported to negatively impact the distribution and behaviour of coastal cetaceans, like dolphins. While this may be true, dolphins in New Quay bay do not seem to be negatively affected by the level of boat traffic here. Sea Watch Foundation continues to monitor dolphin-boat interactions and our studies show that unless the volume of boats suddenly increases, current levels of motor boat activity adhering to the harbours code of conduct is not a concern.
A final factor worth considering could be the influence of the change in weather, particularly the increase in wind strength blowing across the harbour. Wind is one of the major factors driving wave energy and swell. When there is an onshore wind coming off the sea – i.e. someone standing facing out to sea would have wind blowing toward them – wind stirs up the seabed by whipping up waves and causing the sea state to be rough and choppy (or potentially wild and stormy if it is a very strong wind). This disturbs marine worms out of their burrow, dislodges shellfish such as mussels, limpets and cockles from their home on rocks, and forces small fish, crabs and other forms of marine life out of weed beds. This creates a feast for larger predatory fish like bass, mackerel and herring which in turn forage inshore into shallower water to take advantage of the food which has become available. With more predatory fish in the shallows, dolphins could certainly be drawn closer, as not only would there be more biomass in the area, but also it can make catching the fish easier, as they get driven to the shore.
Whether it’s the easy pickings from local fisherman’s nets, lack of noisy boats in the bay or the weather and waves, something is causing this curious change in behaviour in our resident bottlenose dolphins!
Perhaps they are coming closer for one, or a combination of these drivers, or perhaps like many tourists……they simply can’t resist New Quay’s fish and chips!
Written by Charles H. J. McGibney (Sea Watch Foundation intern)