on ventral midline from the anus caudally to the pelvic symphysis cranially and locate the pouches internally on each side of the coelom. Place stay sutures in the gravid pouch and elevate it from the rest of the coelom. Make an incision with scissors where the tail of a fry is visible and exteriorize the fry through the incision. Other fry in the same pouch can be gently manually expressed through the same incision. Close each incubation pouch with a simple continuous pattern or a continuous inverting pattern using absorbable suture. If possible, remove air trapped in the incubation pouches prior to closure of the coelom, otherwise, the fish may be positively buoyant postoperatively.
In batoids species, position the fish in ventral recumbency and make a longitudinal incision 2 cm lateral to the lumbar muscles, similar to the approach used for ovariectomy. Enter the coelomic cavity after elevating the peritoneum. Locate the uterus and incise its wall, paying attention not to contaminate the coelomic cavity with uterine contents including the embryonic histotroph. After removing the young from the uterus and handing it to a team dedicated to young recovery, close the uterus in two layers with a continuous inverting suture pattern using monofilament suture. Lavage the coelomic cavity before routine closure (Sladky and Clarke 2016).
Urinary Surgery
Renal biopsies are performed in fish to obtain cultures from the posterior kidney in fish with a systemic infection or to investigate renal disease. For instance, a renal biopsy would be indicated to investigate a renal mass displacing the swim bladder ventrally on radiographs (Figure 5.19): this can be due to polycystic kidney disease in goldfish. To access the posterior kidney, make a paramedian coelomic incision midway between the lateral line and pelvic fin. Retract the gonads and the digestive tract. Gently dissect the swim bladder away from the kidney (Harms and Wildgoose 2001). Obtain a wedge biopsy of the underlying kidney. Possible complications include hemorrhage and nephrocalcinosis at the site of biopsy (Harms and Wildgoose 2001).
Figure 5.19 Whole body right lateral radiograph (a) and ultrasound image (b) from a goldfish (Carassius auratus) presenting with a cystic renal mass displacing the caudal chamber of the swim bladder ventrally.
Source: Photo courtesy: Companion Avian and Exotic Pet Medicine Service, University of California, Davis.
Some fish species have a urinary bladder and calcium phosphate uroliths have been reported (Osborne et al. 2009). The removal of bladder stones from a bridled burrfish (Chilomycterus antennatus) by Howard Krum, Veterinary Medicine Doctor, aired during a Public Broadcasting Service of Scientific America in 1998.
Digestive Tract Surgery
Gastrointestinal foreign bodies have been reported in various fish species (Clark 1988; Lecu et al. 2011; Lloyd and Lloyd 2011) and are a common finding in captive and wild sharks (Lloyd and Lloyd 2011). When foreign body removal manually per os or via endoscopy is not possible, gastrotomy or enterotomy is performed. Depending on the fish species and location of the foreign body, use a ventral midline approach cranial to the pectoral fins or between the pectoral and anal fins (Lloyd and Lloyd 2011). Gently exteriorize the intestine (Figure 5.20) and place stay sutures. Digestive tract layers are the same as those of terrestrial vertebrates (Dos Santos et al. 2015). Make a full thickness enterotomy as close as possible to the object in a relatively healthy segment. Multiple foreign objects can often be removed through one enterotomy. If vascular integrity of the digestive segment has been compromised, a resection and anastomosis should be performed, if possible (Sladky and Clarke 2016). In large fish, close the digestive tract in two layers with a monofilament absorbable suture material (Lloyd and Lloyd 2011). Close the second layer using an inverting or simple continuous suture pattern. In smaller fish, use a single inverting suture pattern taking care to include all layers. Lavage the coelomic cavity with sterile saline and then use sterile instruments to close the coelomic wall.
Figure 5.20 A goldfish (Carassius auratus) showing its impacted intestine exteriorized from the coelom and placed on wet gauze.
Source: Photo courtesy: Zoological Medicine Service, Université de Montréal.
Minimally Invasive Surgery
Endoscopy has been described in catfish (Ictalurus punctatus) (Boone et al. 2008), trout (Oncorhynchus mykiss) (Moccia et al. 1984), wolf fish (Hoplias aimara) (Weber 2011b), eel (Anguilla Anguilla) (Macri et al. 2014), and sturgeon (Hernandez‐Divers et al. 2004; Divers et al. 2013; Falahatkar and Poursaeid 2014) among others, to determine sex, evaluate coelomic organs, remove ingested foreign bodies, and obtain biopsies (Boone et al. 2008; Stetter 2010; Divers et al. 2013). Celioscopy may be performed with the endoscope inserted directly into the coelomic cavity or within the swim bladder (Stetter 2010; Stevens et al. 2019). Deflation of the swim bladder may facilitate coelomic organ visualization depending on the species and procedure performed (Hernandez‐Divers et al. 2004). Celioscopy has been used to perform minimally invasive surgical procedures in fish, such as gastrointestinal foreign body removal, organ biopsy, (Stetter 2010; Weber 2011b), and gonadectomy (Hernandez‐Divers et al. 2004).
Telemetry and Microchip Implantation
Sonic or radio transmitters weighing less than 2% of the fish body weight may be implanted in free‐ranging fish and because of the absence of antenna, a small celiotomy is used (Harms and Wildgoose 2001). More recently, injectable sonic transmitters that do not require surgical implantation have become available (Deng et al. 2015). Radiotelemetry transmitters are implanted with a similar technique as in other vertebrates (Wargo Rub et al. 2014). The antenna should exit through another incision rather than the incision used for insertion. It can be threaded through a cannula placed through the lateral body wall. To position the transmitter away from the surgical incision and avoid pressure on the coelomic organs, suture the transmitter to the pectoral girdle (Snelderwaard et al. 2006).
References
1 Adamovicz, L., Lewbart, G., and Gilger, B. (2015). Phacoemulsification and aspiration for cataract management in a dollar sunfish, Lepomis marginatus (Holbrook) – a case report. Journal of Fish Diseases 38: 1089–1092.
2 Andrews, M., Stormoen, M., Schmidt‐Postahaus, H. et al. (2015). Rapid temperature‐dependent wound closure following adipose fin clipping of Atlantic salmon Salmo salar L. Journal of Fish Diseases 38: 523–531.
3 Ang, J., Pierezan, F., Kim, S. et al. (2021). Use of topical treatments and effects of water temperature on wound healing in common carp (Cyprinus carpio). Journal of Zoo and Wildlife Medicine 52 (1): 103–116.
4 Angelidis, P., Vatsos, I., and Karagiannis, D. (2006). Surgical excision of skin folds from the head of a goldfish Carassius auratus (Linnaeus 1758). Journal of the Hellenic Veterinary Medical Society 58: 299.
5 Bakal, R.S., Love, N.E., Lewbart, G.A., and Berry, C.R. (1998). Imaging a spinal fracture in a Kohaku koi (Cyprinus
