World Aquaculture Magazine -December 2021

60 DECEMBER 2021 • WORLD AQUACULTURE • WWW.WA S .ORG cavity for tag implantation without injury to the visceral mass (Mahapatra et al. 2018). Before tagging, fingerlings are anaesthetized with a 250- 350 ppm tricaine methane sulphonate (MS-222) (Ross and Ross 2008), depending on size. Initial length and weight of anaesthetized fish is recorded before tagging. The needle of the tag implanter loaded with a tag is injected beneath the scale, reaching the root of the scale. For intraperitoneal (IP) placement, the tag is implanted in the abdominal cavity of the fingerling using the implanter held at a 45-degree angle so that the needle reaches just below the abdominal muscle. When the tip of needle is inserted below the muscle, the implanter must be brought back to a horizontal position without further pushing before releasing the tag into the abdominal cavity. Care must be taken when inserting the needle to avoid internal organ injury. The tag number is noted using the portable tag reader for recordkeeping. After tagging, tagged fingerlings are placed in well- aerated tanks for recovery. After complete recovery, tagged fish are dipped in 2-5 ppm potassium permanganate solution for about one minute and then released back in the tank with aeration (Fig. 4). Tagged fish are monitored for one night to check for any possible mortality. After 24 hours of observation, tagged fingerlings are stocked in well-prepared grow-out ponds for communal rearing. The Effect of PIT Tags on Growth and Physiology The benefit and applicability of PIT tags for a variety of species have been successfully illustrated in mark and recapture, movement, survival, distribution and behavioral studies. Depending on life stage, sex or tag placement, the retention rates of PIT tags vary within and among species (Dieterman and Hoxmeier 2009, Mamer and Meyer 2016). Wagner et al . (2011) recommended standardized techniques for implantation depending on type and size classes of animals. This would not only minimize tissue damage and infection used and proved to be most convenient, suitable and effective for identification and long-term retention (Mahapatra et al. 2001). These tags are being utilized in the current selective breeding program for catla at ICAR-CIFA as well. Components of PIT Tag Systems A PIT tag consists of a glass-encased integrated circuit chip, antenna coil and capacitor (Roussel et al . 2000). Tags differ in size and shape depending on the animal model and exist both in cylindrical and disk shapes. Generally, the tags are about 8-32 mm long with diameters of about 1-4 mm and the large size PIT tags cost less in comparison to small ones. PIT tags for fish and animals and are manufactured and marketed by various firms like Biomark (USA), FoxBase Technologies Pvt. Ltd. (Bengaluru, India), Das &Kumars (Uttar Pradesh, India) (Fig. 1). Small PIT tag readers are portable and compact and can be powered with conventional batteries or directly from an AC source. Readers can detect PIT tags with 125 kHz to 135 kHz frequency (Fig. 2). The tag can be easily identified through hard and soft tissue, glass, liquid, plastic and with difficulty through metals. Marking with a PIT tag is long-lasting and tags can be retained inside the body cavity as long as desired without any harm to the organisms. Tags can be recovered after sacrificing the specimen and reused. A PIT tag implanter is constructed of aluminum tubing with 12-gauge needle attached to a spring. A syringe style implanter with a corrosion-resistant stainless steel spring and hardware is also used. Tags are secured inside the needle, which prevents damage of tags before implantation. Recently, gun-shaped tag implanters have become available in the market and are being widely used (Fig. 3). Protocol for PIT Tagging of Fish Before tagging, fingerlings are collected from nursery ponds and kept overnight in well-aerated water without feeding, so that the digestive tract was cleared. This creates more space in the fish body FIGURE 2. PIT tag readers. FIGURE 3. PIT tag implanters. Before tagging, fingerlings are collected from nursery ponds and kept overnight in well-aerated water without feeding, so that the digestive tract was cleared. This creates more space in the fish body cavity for tag implantation without injury to the visceral mass. Before tagging, fingerlings are anaesthetized with a 250-350 ppm tricaine methane sulphonate (MS-222), depending on size. Initial length and weight of anaesthetized fish is recorded before tagging.