Abstract

An endangered Hawaiian monk seal (Monachus schauinslandi) was stranded on the island of Kauai with approximately 5 m of monofilament line trailing from its mouth. The seal was identified as TT40, a 20-year-old male that the National Oceanic and Atmospheric Administration was tracking via a satellite-linked dive recorder (SDR). Approximately four incidences of seals becoming entangled with fishing line or hooked have occurred each year since 2000. Initial examination revealed that the monofilament line extended beyond the oropharynx and that a thorough diagnostic workup was necessary. The seal was captured and transported to the island of Oahu.

Anesthesia for both the endoscopy and subsequent surgery followed a very similar plan. TT40 was premedicated with Atropine (0.02mg/kg IM). Intravenous diazepam was given (0.15mg/kg) for sedation prior to induction. Once sedated the seal was rolled into surgery for mask induction with isoflurane. A large animal anesthetic machine was utilized, and manual ventilation was performed at a rate of 5 breaths min^-1 for the duration of the procedure. Physiologic parameters monitored during both procedures included respiratory rate, heart rate, oxygen saturation, core body temperature, and end tidal CO₂ levels.

Gastroscopy revealed 2 m of 50-lb test monofilament main line tied to a 2-cm diameter brass "stop" ring and barrel swivel in the mid-esophagus. The barrel swivel was connected by 50 cm of 300-lb test monofilament to an 11-cm-long circle hook that was imbedded in the distal esophagus midway between the heart and the lower esophageal sphincter. Attempts to retrieve the foreign body via the endoscope were unsuccessful, so abdominal exploratory surgery was performed 24 hr after the endoscopic procedure.

A ventral midline abdominal incision was made from just caudal to the xiphoid process to the umbilicus. The stomach was located by palpation, stay sutures were placed, and the stomach was partially exteriorized. A 12-cm incision was made in the body of the greater curvature. The surgeon reached through the gastrotomy incision, through the cardiac sphincter, and located the large circle hook in the esophageal mucosa. The hook was then removed from the esophageal mucosa and the associated hardware pulled through the esophagus and out through the gastrotomy. The stomach was closed in three layers: muscle wall, subcutaneous tissue, and subcuticular tissue and skin. The total anesthetic time of the surgery was approximately 5.5 hr, during which the seal appeared stable.

Twenty-four hours after recovery from anesthesia, the seal was returned to a coral filtered seawater pool with a haul-out area. Whole fish were offered and the seal began to eat approximately 30 hr after the procedure, which allowed for oral administration of antibiotics. The seal's appetite remained excellent, and the incision site healed without complication. Periodic hematology and serum biochemistry analysis were performed to monitor the seal post operatively. Three weeks after the procedure, the seal's wound had sufficiently healed, and the seal was deemed healthy for release. A new SDR was attached to the dorsal pelage, and the seal was released near the original capture site on the island of Kauai exactly 21 days after the surgery was performed. The SDR data obtained both before and after the foreign body removal provided an assessment of this seal's diving and haul-out behavior. Most dives were less than 40 m deep and 4 min long both prior to and after surgery, though a great number of deeper dives were performed after surgery. The return to previously observed dive behavior and subsequent sightings of TT40 in good condition indicate a successful recovery and reintroduction.