Preliminary results of modified dvideo-id technique and applied to Peale's dolphins, Lagenorhynchus australis (Peale, 1848) at Añihué Reserve, Chile

Abstract

Located on the continental shore of Chilean Patagonia at the northernmost limit of Aysén Region (43°47.93'S; 72°58.43'W), Añihué Reserve has approximately 17 nautical miles of marine coastline containing highly diverse habitats. Two small natural elevation sites, R1 (43°47.78'S; 72°58.72'W) and R2 (43°48.76'S; 72°58.78'W), were selected as observatories on Tonina Beach from where graphic material was produced during 2011with the collaboration of volunteers, during daylight and sea state lower than force four (Beaufort), using/testing several SLR camera models, occasionally a Sony HDRFX7 camcorder and a Hero GoPro underwater camera. Digikam, a Linux/KDE photographic management application, was used as a graphic SQLite database to classify the frames and run dataset queries based on "tags" selections of natural marks. Tonina Beach in Añihué Reserve is visited by at least 68 individuals of L. australis, patrolling and foraging in very shallow waters in small groups that may fuse occasionally. Despite recording effort being highly concentrated during summer, the collected graphic material included: dolphins in all seasons; distributed among 10 of 15 possible seasonal combinations (66.67 %); with re-identified individual in all four seasons; several re-identifications in winter of individuals sighted during summer (N=11; 26.19 %); and more than third of the individuals (N=25) were identified between mid-autumn and mid-spring. These first results suggest that the coastal L. australis populations, at least in front of Añihué Reserve, present a high fidelity to the site not supporting previous hypothesis of significant seasonal/migratory movements for the species and, provide alternative explanations to seasonal variations of recorded abundance. DVideoID, an individual identification protocol based on graphic records of natural marks produced during chase from moving platforms, proved to be reliable also under "sit and wait from the shore" mode of data production. The method, entirely based on free opensource applications, was modernized by switching from a traditional database client to a tagged graphic database approach, simplifying the process for managing information and is presented in recognition of the need for method standardization. The most useful tags to identify Peale's dolphin individuals were skin marks from bites, especially on the dorsal fin; the presence of dorsal nicks (whose origins are also related to bites); and marks due to skin pathologies. Añihué Reserve proved to be a site suitable for long term cetacean studies even when collecting data directly from the shore, avoiding potential impacts of mobile observation platforms. The extremely low number of juveniles (N=5) and calves (N=1) from a total of 68 dolphins and, the high prevalence of skin diseases (N=35; 51.47 %), are a source of special concern. Their potential relationship with the local salmon farming industry, which has facilities on both coastal boundaries of the reserve, needs to be evaluated.