Recreational fishing impacts on Dolphins: A study on prevalence in Gibraltarian waters and public perceptions on fishermen-dolphin interactions
The Strait of Gibraltar is known as a heavily used marine area with intense fishing operations. Gibraltarian waters are highly biodiverse, providing home to three dolphin species: the short-beaked common dolphin (Delphinus delphis), striped dolphin (Stenella coeruleoalba) and the common bottlenose dolphin (Tursiops truncatus). British Gibraltar Territorial Waters (BGTW) are a hotspot for recreational fishing, including tuna fishing. Fishermen are known to use the dolphin-tuna association to catch tuna, which has the potential to injure dolphins, sometimes even fully amputating dorsal fins. This study aims to 1) investigate fishing activities and fishermen-dolphin interactions in the Bay of Gibraltar, and 2) understand public perceptions on fishing impacts on dolphins and their conservation issues. This was attained following an extensive literature review, observational boat surveys and an online public questionnaire (n=116). Via boat surveys, illegal fishing activities were seen within the Dolphin Protection Zone (DPZ), and most recreational vessels weren’t following the cetacean protocol. The online survey showed an overall concern towards fishing impacts on dolphins though a lack of awareness of certain regulations already in place. There is also a trend in attitudes of Gibraltarians placing conservation responsibility on stakeholders and the Government. The conclusions of this study show that the public could benefit from a raise in awareness on existing methods of dolphin conservation in Gibraltar, in order to encourage public participation in marine management, which is essential for management success. Results of the public survey along with the field data collected on fishing impacts and fishermen behaviour could be combined in order to provide more appropriate and effective management measures to protect dolphins in BGTW.
Read more about Adrianna’s research here.
Keywords: Recreational Fishing Impacts, Dolphins, Injuries, Cetacean Conservation, Environmental Attitudes, Public Engagement, Marine Policy
Primary supervisor: Dr Awantha Dissanayake, University of Gibraltar
Secondary supervisor: Luisa Haasova, University of Gibraltar/MMIRC,
In conjunction with:
Stephen Warr, Department of Environment, Sustainability, Climate Change and Heritage (DESCCH)
Recreational fishing impact on dolphins in the Bay of Gibraltar
In recent years, the fishing industry has emerged as having a particularly negative impact on cetaceans, making it one of the first causes of death for these animals. While many studies have been conducted on commercial fishing, little is known about how recreational fishing affects cetaceans, and its role in management and conservation plans is still marginal. The Bay of Gibraltar is an area that supports a variety of marine-related activities. Recreational fishing is particularly popular as the only fishing activity permitted within the British Gibraltar Territorial Waters. Concurrently, the waters of the Bay, due to its oceanographic characteristics, are regularly used by three species of dolphin: the common dolphin (Delphinus delphis), the striped dolphin (Stenella coeruleoalba), and the bottlenose dolphin (Tursiops truncatus). Despite the fact that the Gibraltar’s Government has implemented several measures to protect dolphins, the Bay is known for the presence of individuals with human-related injuries and, at the same time, the persistence of fishermen in using illegal fishing techniques, such as popping. In order to assess the impact of recreational fishing on dolphins of the Bay of Gibraltar, boat-based surveys were conducted to collect data on dolphin sightings and recreational fishing vessels, before and during Bluefin tuna fishing. Data was analysed and graphically represented to show area most frequently visited by dolphins and to highlight potential spatial overlaps with recreational fishing vessel activities. The findings showed that there were no statistically significant differences in the occurrence of sightings and the number of recreational fishing vessels with the two fishing seasons. There was no statistical correlation between the number of pods observed and the number of recreational fishing vessels. The analysis of the behavioural status of dolphins, showed a higher rate of milling during the Bluefin tuna season as well as a decrease in feeding and resting. The risk assessment of dolphin-fishing interaction enabled to identify 30 potential incidences. Therefore, it was suggested that the already established Dolphin Protection Zone be updated based on these findings as well as the zoning of the Mobile Cetacean Conservation Area be reviewed. In addition, the implementation of a Bay surveillance plan to enforce existing regulations more strictly by recreational fishermen.
Cetacean-Vessel Interactions in the Strait of Gibraltar
The Strait of Gibraltar is a unique marine environment, due to the high number of oceanographic processes and anthropogenic activities that take place simultaneously in this small marine space. Its strategic geographical location (the only passage connecting the Atlantic Ocean to the Mediterranean Sea) and its very productive waters make it an important maritime and cetacean hotspot. As the second busiest channel in the world, shipping and commercial fishing are the most common activities, whilst recreational and whale watching vessels are increasingly present too. This heavily shared marine space inevitably creates potential for human-wildlife conflict, which, for the seven commonly seen species of cetaceans, may result in entanglement in fishing gear, disturbance and even ship strikes. This dynamic may be exacerbated in the summer months, with the start of recreational tuna fishing season, which adds pressure to an already exploited environment. Collisions, which mostly occur when cetacean habitats overlap with high density vessel areas, have been shown to affect marine mammals worldwide, to different extents, and, given the potentially catastrophic consequences on both individual or species population levels, this issue is increasingly becoming a priority for many conservation and management organisations. “Collision hotspots” have been identified worldwide and are continuosly monitored, with suitable mitigation measures being investigated. To better understand the complex vessel-cetacean interactions and identify potential for collision in the Strait, the present study combined field observations from a platform of opportunity, with a comparative analysis of ship strike hotspots worldwide. Fifteen, 2-hour trips were conducted onboard a whale watching vessel operating from Tarifa, Spain, during June and July 2022. These were split over three phases: before, during and after tuna season, with the aim of investigating any major differences between them. Observation parameters included cetacean species, abundance and behaviour, as well as vessel frequency, type and any interaction with the animals. In total, 650 cetaceans were recorded across six of the seven species regularly observed in the Strait, with pilot whales being the most common. The area’s heavy maritime traffic was confirmed by the 486 vessels encountered over the fifteen trips, the majority of which were, unsurprisingly, commercial (243), followed by recreational (155), 5 suggesting that the latter are becoming an increasingly important stakeholder. Vessels were the only variable that significantly differed across phases, as they were, on average, far more abundant during tuna season, highlighting the key role this stakeholder may play within collision scenarios, and potentially suggesting that cetacean distribution might not be affected by vessel presence/ numbers. Collision risk (with varying degrees of severity) was detected 73% of the time, and was primarily elicited by commercial ships, followed by the observation vessel. Risk affected 4 of the 6 observed species and, despite not being significantly different across the three phases, the high incidence of near miss events witnessed clearly highlights the large scale of the problem, and the urgent need for: 1) further, ongoing research on the topic; 2) more effective – and potentially new – collision mitigation measures, based on an economic impact assessment; 3) improved communication among local, relevant stakeholders to facilitate any lobbying attempts with regulatory bodies; and 4) wider awareness raising efforts, to highlight the significance of this issue in the Strait of Gibraltar, which often involves endangered or critically endangered cetacean species.
Review of Marine Management in UK Overseas Territories: A Roadmap for Gibraltar