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Introduction Statutory mandates define the restoration responsibilities of the U.S. Fish and Wildlife Service with regard to anadromous salmonids (Anadromous Fish Conservation Act, Fish and Wildlife Act of 1956, Atlantic Sahnon Conservation Act, and others). Consequently, it is important that those dealing with the population dynamics, restoration efforts, and ecology of these fish remain apprised of advances inlong-term fish mazking methods. Since man began exploiting anadromous sahnonids, there has been a need to identify individual fish and stocks of fish. Today the science of fish tagging and stock identification has evolved into a sophisticated art that assimilates input from varied disciplines, including electrical and mechanical engineering, genetics, mathematics, and fishery biology. For this report, we define along-term tagging method as one that can be detected at least 1 yr after application. Tag application, tag retention, and recovery or detection of the mark were evaluated by reviewing the literature. In addition to discussing conventional methods in which a physical mazker is applied to individuals, we reviewed several newer methods of stock identification. Computer literature seazches for 19837 were conducted by using the BIOSIS and U.S. Fish and Wildlife Reference Service. We also solicited information .from Canadian and United States reseazchers who are involved in fish marking or identification projects. An in depth review of nontag marking methods by Moring and Fay (1984) and an extensive bibliography of aquatic animal tagging by Emery and Wydoski (1987) provided summarized information for the years before 1984. Our intent was not to review critically all the various methods available, but to discuss those being used or that have application to the anadromous sahnonid fishery and to update the information base with recent findings. In other words, we concentrated on tags that can be applied quickly to a large number of fish and that are retained at reasonably high percentages for at least 1 yr. Coded Wire Tags A method of mazking fish by implanting a coded wire tag (CWT) into the snout was developed by Jefferts et al (1963). Coded wire tags are bits of stainless steel wire etched with a binary code consisting of four longitudinal rows accounting for 262,144 possible numerical combinations. Standard tags are round, i mm long, and 0.25 mm in diameter; smaller tags (0.5 mm) aze also available for small fish. Coded wire tags are implanted with an automated injection assembly that enables a biologist to tag 500 to 800 fish per how. An adipose fin clip is often added as an external confirmation marker. The fish is then typically passed through a quality control unit (magnetic field to determine the presence of the tag in the snout) and released. Elrod and Schneider (1986) reported losses of less than 1% during their work with these tags on lake trout (Salvelinus namaycush). Moring and Fay (1984) summazized extensive CWT research and tag loss in Atlantic salmon (Salmo salary and Pacific salmon (Oncorhynchus spp.). Fish aze ultimately identified as carrying a CWT by the recognition of the adipose clip or detection of the tag with magnetic field. The fish must then be sacrificed to allow for removal of the tag from the snout and decoding, which means reading the tag under a microscope. The manufacturers of CWT's estimate that 200 tags can be decoded per person per day. Moberly et al. (1977) reviewed vazious procedures required to insert, detect, retrieve, and process the CWT's. In 1984, the general consensus among some CWT users was coho salmon (Oncorhynchus kisutch) weighing 2.27 g (200/lb) were the smallest fish that would accommodate the tags. At the same time, some users believed that fish as small as 0.38 g (1,200/lb) could be successfully implanted by an experienced tagging crew. Opdyke and Zajec (1980) tagged chum salmon (Oncorhynchus keta) as small as 0.8 g. Northwest Marine Technology, a commercial vendor, has advertised that fish as small as 0.25 g (1,800/Ib) can be routinely tagged. The basis for this claim was a tagging study by Thrower and Smoker (1984) in which emergent Alaskan pink salmon (Oncorhynchus gorbuscha) were implanted with half-length CWT's. In this study the authors developed an injector head mold smaller than anything available then, which enabled them to implant these small fish at rates of 800/h with more than 90% tag retention. Of the total of 9,338 emergent pink salmon they tagged in April 1982, 17 adults were recovered in August 1983. Their estimate of return (0.4%) was similar to that for other local untagged stocks during the same period. Advances were made in the field of binary coded wire tagging in the early 1980's. An alternative method of tag decoding was developed that did not require sacrificing the fish. Flat tags (1.5 mm long) with the binary code etched along the edge could be read by using an X-ray machine that transmitted an image of the tag (while in the fish's snout) to a television screen. This technology, which has just recently become commercially available, makes it possible to identify fish many times, or at least eliminate the time-consuming tag retrieval process (Moring and Fay 1984). The flat tags and X-ray detection equipment require a considerably greater initial investment than the round tag system; however, the system eliminates the cost of tag retrieval and is nondestructive. Based on price quotations provided by Northwest Marine Technology, individual tag cost in mid-1987 ranged from $0.03 to $0.07, depending on the quantity ordered.