Bottlenose dolphin (Tursiops truncatus) presence and incidental capture in a marine fish farm on the north-eastern coast of Sardinia (Italy)

Abstract

On the north-eastern coast of Sardinia, from November 2004 to January 2006, the first attempt in the Mediterranean basin to obtain information on encounter rate, group size and incidental capture of bottlenose dolphins in a marine fish farm was assessed, combining direct observations from fish farm boats with photo-identification studies. During 15 months of research, 79 d (65.3% of the total monitored days) were spent in direct observation of 146 groups of bottlenose dolphins around the fish farm cages. There was a peak in bottlenose dolphin presence during winter. Photographs were taken in the fish farm area during 79 encounters on 61 different days (totalling 34 marked individuals). The regular occurrence of some dolphins suggests individual preferences for the fish farm area. The incidental bottlenose dolphin capture observed in large, loose predator nets (1 dolphin per month) is cause for concern, as it is questionable whether or not the bottlenose dolphins in the area can sustain incidental capture of this magnitude. The information gained from this study shows the necessity for further regulations to be established, both in the use of predator nets and management of marine fish farms.

Aggregations of wild Atlantic Bluefin Tuna (Thunnus thynnus L.) at Mediterranean offshore fish farm sites: Environmental and management considerations

“…Bacher et al, 2012), as well as some marine mammals whose populations are deemed "critically endangered" in the Mediterranean, such as Bottlenose Dolphin (Tursiops truncatus) (criterion A3bcd; C1), and Monk Seal (Monachus monachus) (criterion A2abc; C2a(i); E) (e.g. Güç lüsoy and Savas, 2003;Díaz-López and Bernal-Shirai, 2007;Piroddi et al, 2011).…”

Whistle characteristics in free-ranging bottlenose dolphins (Tursiops truncatus) in the Mediterranean Sea: Influence of behaviour

“…Additionally, human activities influence the distribution of food resources and dolphins behaviour (Díaz López, 2006a,b;Díaz López, 2009), which promote the evolution of social organizations (Díaz López and Shirai, 2008) and individual preferences for the area (Díaz López and Shirai, 2007).…”

Long-term acoustic monitoring of bottlenose dolphins, Tursiops truncatus, in marine protected areas in the Spanish Mediterranean Sea

“…Two fish farms operated a total of 30 floating cages in Serra Gelada during the study period. Open cage aquaculture in the Mediterranean Sea has been shown to benefit bottlenose dolphins by making it easier for them to catch prey near the cages (Díaz L opez and Bernal Shirai, 2007;Piroddi et al, 2011), therefore, we expected to find a high % DPH in Serra Gelada due to the attraction effect of fish farming operations. Furthermore, Raga & Pantoja (2004) suggested that a resident population of bottlenose dolphins might be present in this region based on the spatial and temporal distribution of sightings obtained in their study.…”