Histology of dart tag insertion sites in the epaulette shark

Abstract

Samples of dermal and epidermal tissues of epaulette sharks Hemiscyllium ocellatum were examined histologically to assess damage caused by tagging. Tissues from around tag sites were removed at time intervals ranging from 100 min to 284 days post-tagging. These samples showed acute and chronic responses to tagging. Acute responses consisted of localized tissue breakdown and haemorrhaging, and occurred within the first few hours after tag insertion. At 10 h post-tagging, an intermediate response was apparent. This phase was characterized by further haemorrhaging and red and white blood cell movement into the wound area. The chronic response observed in the 10-284-day post-tagging samples was characterized by fibrous tissue formation to sequester the tag. This tissue presumably protects the adjacent musculature from further trauma produced by movement of the tag and provides a continuous barrier between the internal and external milieu. Tissue repair appeared to progress consistently in all specimens and no secondary infections at the tag site were seen. Tagging produced only localized tissue disruption and did not appear to be detrimental to the long term health of individual sharks. Our findings show that spaghetti style dart tagging is an acceptable method for marking individuals (40-75+ cm total length) of this species. 1997 The Fisheries Society of the British Isles

Preliminary observations of tag shedding, tag reporting, tag wounds, and tag biofouling for raggedtooth sharks (Carcharias taurus) tagged off the east coast of South Africa

“…A variety of encrusting organisms, such as filamentous algae, barnacles, sponges, and ascidians, have been found growing on recaptured tags (Davies and Joubert, 1966;Heupel and Bennett, 1997;Heupel et al, 1998). None of these studies, however, investigated the composition and magnitude of tag biofouling.…”

“…The tag wound associated with dart tags consisted of an open wound, which appeared to be irritated by the continual movement of the tag streamer at the point of tag insertion. Heupel and Bennett (1997) concluded that although plastic headed dart tags often caused localized tissue disruption, the wounds were free of infection even in sharks whose tags were heavily fouled with algae. A larger percentage of sharks tagged with dart tags by members of the ORI tagging programme exhibited tag wounds than those tagged by members of the PEM tagging programme.…”

Assessing the size, growth rate and structure of a seasonal population of whale sharks (Rhincodon typus Smith 1828) using conventional tagging and photo identification

“…Conventional tagging is increasingly used to estimate and assess shark populations and movement and since 1962 the National Oceanographic and Atmospheric Administration's National Marine Fisheries Service Laboratory (NOAA-NMFS) 0165 has implemented a cooperative shark tagging program with recreational anglers and commercial fishers leading to the tagging of over 87,000 sharks (Kohler et al, 1998). However tag shedding appears common in a range of shark species, undermining viable population estimates (Davies and Joubert, 1967;Gruber, 1982;Carrier, 1985;Heupel and Bennett, 1997). By comparison, photo identification is a non-invasive method of identifying individuals that relies on cataloguing distinctive scars or markings originally developed to identify terrestrial animals and marine mammals that can be clearly seen (Katona et al, 1979;Arnbom, 1987).…”

Use of natural marks on population estimates of the nurse shark,Ginglymostoma cirratum, at Atol das Rocas Biological Reserve, Brazil

“…In terms of individual identification, a great variety of methods have been used in fish population studies (Heupel & Bennett 1997). Artificial external marks such as tags are commonly used in shark studies (Ingram 1994, Kohler & Turner 2001.…”