Effects of Smart Position Only (SPOT) Tag Deployment on White Sharks Carcharodon carcharias in South Africa

Abstract

We present 15 individual cases of sub-adult white sharks that were SPOT tagged in South Africa from 2003–2004 and have been re-sighted as recently as 2011. Our observations suggest SPOT tags can cause permanent cosmetic and structural damage to white shark dorsal fins depending on the duration of tag attachment. SPOT tags that detached within 12–24 months did not cause long term damage to the dorsal fin other than pigmentation scarring. Within 12 months of deployment, tag fouling can occur. After 24 months of deployment permanent damage to the dorsal fin occurred. A shark survived this prolonged attachment and there seems little compromise on the animal's long term survival and resultant body growth. This is the first investigation detailing the long term effects of SPOT deployment on the dorsal fin of white sharks.

Gauging the Threat: The First Population Estimate for White Sharks in South Africa Using Photo Identification and Automated Software

“…Thus, this aggregation site provided an ideal area to collect dorsal fin images of a range of age classes and both sexes without seasonal paucities. Additionally, several individual white sharks from this region have been identified at other aggregation sites, with connectivity documented between False Bay, Mossel Bay, KwaZulu Natal, and Western Australia [1], [19], [27]. This suggests that Gansbaai is a major aggregation area for white sharks in the Southern African region allowing for an accurate population estimate from a single site.…”

“…This method is particularly appropriate when examining vulnerable species or populations, from invertebrates [11], [12] to tigers [13], marine mammals [14]–[16] and sharks [17]–[19]. The first dorsal fin of white sharks is often characterised by distinctive shapes, notches, scaring and pigmentation patterns, which can be used to recognise individuals over many years [7], [19]. From such photo ID data, mark recapture methods can be applied to estimate population sizes, given that the model’s basic assumptions are met adequately [14], [20].…”

Considering the fate of electronic tags: interactions with stakeholders and user responsibility when encountering tagged aquatic animals

“…For example, in one study area, satellite tags mounted to dorsal fins of white sharks ( Carcharodon carcharias ) were found to cause fin damage, although the actual sublethal fitness impacts (if any) on these animals remain unknown (Jewell et al . ). Conversely, sublethal impacts on fitness have been detected in other species; tags on king penguins ( Apteno dytes patagonicus ) have been found to negatively affect breeding success in resource‐poor years (Saraux et al .…”

“…long-term sublethal impacts) of aquatic animals (Wilson & McMahon 2006). For example, in one study area, satellite tags mounted to dorsal fins of white sharks (Carcharodon carcharias) were found to cause fin damage, although the actual sublethal fitness impacts (if any) on these animals remain unknown (Jewell et al 2011).…”

Tracking sharks without teeth: a non-invasive rigid tag attachment for large predatory sharks

“…Additionally, some communities are dependent on white sharks for ecotourism, so there are sensitivities to the risk (or perceived risk) of damage to dorsal fins from attaching data loggers [15]. Therefore, attaching tags to the dorsal fin [16] could have significant biological and economic consequences that must be limited.…”