Since the International Pacific Halibut Commission (IPHC) began tagging in 1925, over 462,000 tagged Pacific halibut have been released and more than 51,000 of these releases have been recovered. Pacific halibut are tagged to study migration, age, growth, and mortality. A reward is offered for recovered tags released by the IPHC.
The IPHC has deployed a variety of tag types over the years, from simple metal straps or plastic-coated wire opercular tags to complex satellite and electronic archival tags capable of collecting and storing a variety of data. Almost all tags have been applied to the head on the eyed side, but some tags have been applied to different parts of the body, including the dorsal musculature, body cavity, tail, and near the corner of the mouth on the blind side. Descriptions of older tagging studies are summarized in Kaimmer 2000 and Trumble et al. 1990.
Some of the more recent tag types used in IPHC experiments are outlined below.
Fig. 1 A wire tag looped through the opercular bone
The IPHC has used plastic-coated wire tags (also referred to as “wire tags” or “cheek tags”) for more than 50 years. Plastic-coated wire tags are applied to the eyed-side operculum; a hole that passes under the opercular bone is made with a tagging needle, and the tag is inserted through the hole and twisted into a loop around the opercular bone (Fig 1). Over 230,000 Pacific halibut have been tagged with wire tags, and nearly 20,000 of those tags have been recovered. The plastic tubing covering the wire comes in a variety of colors. Most recently, the IPHC has used fluorescent yellow, hot pink, light pink, two-toned orange, and neon green. The colored plastic tubing is printed with IPHC’s contact information and a tag number and for some experiments, a reward amount. In some cases, wire tags have been used to help test the efficacy of other kinds of tags (described below). In these cases, wire tags were applied to the same fish as another tag type, to evaluate retention of new tag types and other factors.
In 2015, IPHC began wire-tagging small halibut encountered on the National Marine Fisheries Service (NMFS) groundfish trawl surveys and on the IPHC fishery-independent setline survey in 2016. These tagged fish may be recovered in trawl fisheries as well as commercial longline fisheries. Colors used for this tagging effort include fluorescent yellow, light pink, and two-toned orange. In 2017, a longline discard mortality study is planned in the western Gulf of Alaska, during which Pacific halibut will be released from longline gear using different removal methods and tagged. Recoveries from each treatment group will provide additional information on discard mortality rates by removal method.
Pop-up archival transmitting (PAT) tags
Fig. 2 A pop-up archival transmitting tag
Pop-up archival transmitting tags, also called satellite tags, or PAT tags, are a type of electronic tag attached externally to the fish by a dart and leader assembly (Fig 2). Instrumentation in the tag body collects and stores data such as depth and temperature at frequent time intervals. Data can be retrieved without physically recovering the PAT tag. The tag body is attached to the leader with a pin that releases on a pre-programmed date, at which point the buoyant tag body floats to the surface where it transmits its location and accumulated data to a satellite. A number of PAT tag experiments have been conducted on Pacific halibut beginning in 2002, with over 400 PAT tags deployed. Most of these experiments were designed to look at movement: seasonal spawning migrations, dispersal, and site fidelity for summer feeding grounds (Loher 2008; Loher and Blood 2008; Loher and Seitz 2006, 2008; Seitz and Loher 2006; Seitz et al. 2007, 2008, and 2016). In 2016, the IPHC was part of a collaborative effort to investigate discard mortality rates (DMRs) of trawl-caught Pacific halibut in the Bering Sea following expedited release. A total of 160 Pacific halibut were tagged with PAT tags capable of detecting movement (swimming), which could in turn be interpreted as evidence of fish survival.
Electronic archival tags
Electronic archival tags collect and store data on temperature, depth, and in some cases, light levels. These tags are either internally implanted in the abdominal cavity or attached externally to the fish. Several types of electronic archival tags have been deployed on Pacific halibut in experiments in 2008 and 2011 (Fig 3a,b). Unlike PAT tags, the electronic archival tags must be physically recovered to retrieve the stored data (Loher and Rensmeyer 2009, Loher and Nielsen 2012).
Fig. 3a An externally-mounted tag
Fig. 3b Electronic tag indicators
Dummy archival tags (test of method tags)
“Dummy” archival tags were deployed in 2009 and 2013 to test methods of external archival tag attachment (Fig 4). Since electronic tags are expensive, it is important to ensure that the tags will remain attached to the fish and also not negatively impact the fish’s health or marketability of the flesh. In most cases, these fish were also wire tagged to help increase the probability of recovery. Results of dummy tag experiments (number of recoveries by attachment method) will guide the attachment protocols used in future archival tag deployments (Loher and Geernaert 2011, 2014).
Passive integrated transponder (PIT) tags
Fig. 5 An IPHC sampler scans for a PIT tag
Passive integrated transponder (PIT) tags were used by the IPHC between 2001 and 2004. PIT tags are about the size of a grain of rice and contain a microchip with a unique code that can be read with an electronic reader without removing the tag from the fish (Fig 5). Several small pilot studies using PIT tags were conducted in 2001 and 2002 to test different body sites for tag placement, including the eyed-side cheek muscle, the tongue, caudal peduncle, and behind the dorsal eye. The final site chosen for PIT tag implantation was under the skin on the white (blind) side of the head over the opercular plate. Over 67,000 Pacific halibut were implanted with PIT tags in a coastwide study in 2003 and 2004. The tagging was followed by seven years of portside scanning of commercially landed Pacific halibut, during which over 3,000 tags were detected. Because PIT tags were not visible in tagged fish, recoveries from the PIT experiment were not subject to reporting biases observed in studies using external marking. Results of the PIT tag study showed that Pacific halibut continue to migrate between regulatory areas at larger sizes; not just as small fish as previously thought (Kaimmer et al. 2012, Webster et al. 2013).
Chen, D.G., and Xiao, Y. 2006. A general model for analyzing data from mark-recapture experiments with an application to the Pacific halibut. Environ. Ecol. Stat. 13:149-161. DOI 10.1007/s10651-005-0002-4
Kaimmer, S. M. 2000. Pacific halibut tag release programs and tag release and recovery data, 1925 through 1998. Int. Pac. Halibut Comm. Tech. Rep. 41.
Kaimmer, S. M., Geernaert, T. O., and Forsberg, J. E. 2012. Development of deployment and retrieval protocols for Passive Integrated Transponder (PIT) tags: Application to Pacific halibut (Hippoglossus stenolepis). Int. Pac. Halibut Comm. Tech. Rep. 56.
Loher, T. 2008. Homing and summer feeding site fidelity of Pacific halibut (Hippoglossus stenolepis) in the Gulf of Alaska, established using satellite-transmitting archival tags. Fish. Res. 92:63-69.
Loher, T. and Blood, C. 2008. Using Pop-up Archival Transmitting (PAT) tags to assess early spring dispersion of halibut tagged in Areas 2A and 2B. Int. Pac. Halibut Comm. Report of Assessment and Research Activities 2007:451-461.
Loher, T. and Geernaert, T. O. 2011. Archival tagging to study halibut migration and behavior: captive holding to develop external tagging protocols, and deployment of internal and external dummy tags off Kodiak Island. Int. Pac. Halibut Comm. Report of Assessment and Research Activities 2010: 521-535.
Loher, T., and Geernaert, T.O. 2014. Captive holding to study halibut migration and behavior: captive holding to develop long-term tagging protocols, and deployment of external dummy tags in IPHC Regulatory Area 3A. Int. Pac. Halibut Comm. Report of Assessment and Research Activities 2013:369-378.
Loher, T., and Nielsen, J. K. 2012. Test deployment of geomagnetic-sensing electronic archival tags in IPHC Regulatory Areas 2C and 3A. Int. Pac. Halibut Comm. Report of Assessment and Research Activities 2011:483-490.
Loher, T., and Rensmeyer, R. 2009. Archival tagging to study halibut migration and behavior: surgical techniques for internal implantation, and deployment of externally-mounted tags in Area 2B. Int. Pac. Halibut Comm. Report of Assessment and Research Activities 2008:439-460.
Loher, T., and Seitz, A. 2006. Seasonal migration and environmental conditions experienced by Pacifi c halibut Hippoglossus stenolepis, elucidated from pop-up archival transmitting (PAT) tags. Mar. Ecol. Prog. Ser. 317:259-271.
Loher, T., and Seitz, A.C. 2008. Characterization of active spawning season and depth for eastern Pacifi c halibut (Hippoglossus stenolepis), and evidence of probable skipped spawning. J. Northw. Atl. Fish. Sci. 41:23-36.
Myhre, R. J. 1966. Loss of tags from Pacific halibut as determined by double-tag experiments. Int. Pac. Halibut Comm. Rep. 41.
Myhre, R. J. 1967. Mortality estimates from tagging experiments on Pacific halibut. Int. Pac. Halibut Comm. Rep. 42.
Peltonen, G. J. 1969. Viability of tagged Pacific halibut. Int. Pac. Halibut Comm. Rep. 52.
Pollock, K. H., Chen, H., Brownie, C., and Kendall, W.L. 1998. Age dependent tag recovery analyses of Pacific halibut data. Int. Pac. Halibut Comm. Tech. Rep. 38.
Seitz, A. C., and Loher, T. 2006. Seasonal migration and environmental conditions experienced by Pacific halibut in the Gulf of Alaska, elucidated from Pop-up Archival Transmitting (PAT) tags. Int. Pac. Halibut Comm. Sci. Rep. 82.
Seitz, A. C., Loher, T., and Nielsen, J. L. 2007. Seasonal movements and environmental conditions experienced by Pacific halibut in the Bering Sea, examined by pop-up satellite tags. Int. Pac. Halibut Comm. Sci. Rep. 84.
Seitz, A. C., Loher, T., and Nielsen, J. L. 2008. Seasonal movements and environmental conditions experienced by Pacific halibut along the Aleutian Islands, examined by pop-up satellite tags. Int. Pac. Halibut Comm. Sci. Rep. 85.
Seitz, A. C., Loher, T., and Norcross, B. L. 2016. Further investigation of seasonal movements and environmental conditions experienced by Pacific halibut in the Bering Sea, examined by pop-up satellite tags. Int. Pac. Halibut Comm. Sci. Rep. 86.
Sullivan, P. J., Geernaert, T. O., St-Pierre, G., and Kaimmer, S. M. 1993. Mark-recapture methods for Pacific halibut assessment: a feasibility study conducted off the central coast of Oregon. Int. Pac. Halibut Comm. Sci. Rep. 76.
Trumble, R. J., McGregor, I. R., St-Pierre, G., McCaughran, D. A., and Hoag, S. H. 1990.Sixty years of tagging Pacific halibut: a case study. American Fish. Soc. Symp. 7: 831-840.
Webster, R. A., Clark, W. G., Leaman, B. M., and Forsberg, J. E. 2013. Pacific halibut on the move: a renewed understanding of adult migration from a coastwide tagging study. Can. J. Fish. Aquat. Sci. 70(4): 642-653.