Abstract

Tagging fish for studies to estimate demographics, survival, recruitment, abundance, and habitat use is becoming increasingly important as fish populations decline and habitat decreases with coastal development and urbanization.¹ Fish implanted with intracoelomic tags are typically released promptly after surgery, making choice of incision closure an important consideration. Studies in fish have shown synthetic monofilament absorbable suture induces the least amount of inflammation and is associated with faster wound healing compared to other suture materials.^2,3 In this study, coelomic passive integrated transponder (PIT) tags were placed in juvenile American eels (Anguilla rostrata) (n=23) in a lab-based incision closure study to help determine what technique to employ in field studies. Eels were too small for safe use of PIT tag needle injectors, so PIT tags were inserted into the coelomic cavity through incisions just large enough to accommodate the PIT tag (<3 mm). Although surgical procedures entering the body cavity should routinely be closed to prevent herniation or infection, the small size of both the incision and the eels made it reasonable to evaluate whether benefits of avoiding tissue trauma and foreign body reaction with closure could outweigh potential adverse effects of leaving the incision open to heal by second intention. Incisions were closed with a stainless steel staple (n=8), or a simple interrupted suture (4-0 Monocryl) (n=8), or not closed (n=7). Incisions were evaluated for gross inflammation and given a grade (1–3) prior to euthanasia. Eels were humanely euthanized 29 days after coelomic PIT tag implantation surgery. Histologic samples were collected from the surgical incision site and graded based upon the degree of inflammation present (0–4). Grading results showed good agreement with a significant association between gross incision and histopathology inflammation scores. When histopathology scores for surgical site closure techniques were compared, scores for no closure with healing by secondary intention were significantly lower compared to both staple and suture treatment groups. This study supports the conclusion that suture and staples induce greater inflammation than no closure, and no closure may be the preferred treatment choice for small incisions in American eels, provided that the incision is too small to allow herniation of internal organs.

Acknowledgments

The authors thank Jeffrey Merrell for eel acquisition and husbandry, Greg Lewbart and Emily Christiansen for assistance during procedures, and veterinary students enrolled in Advanced Fish Medicine and Surgery for conducting the PIT tag insertions during their instructional laboratory.

* Presenting author
+ Student presenter

Literature Cited

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2.  Thorstad EB, Okland F, Westerberg H, Aarestrup K, Metcalfe JD. 2013. Evaluation of surgical implantation of electronic tags in European eel and effects of different suture materials. Mar Freshwater Res. 64:324–331.

3.  Hurty CA, Brazik DC, Law JM, Sakamoto K, Lewbart GA. 2002. Evaluation of the tissue reactions in the skin and body wall of koi (Cyprinus carpio) to five suture materials. Vet Rec. 151:324–328.