A review of fish identification methods applied on small fish

Abstract Most of the research on marking of aquatic organisms has been done using large organisms since they tend to have better retention rates, their swimming behaviour is less affected by the size of the tag, they have less trauma due to injectable tags or from the injector itself and they are easier to handle and able to withstand the stress of tagging and recapture. The development of small tags has grown from a necessity to study smaller fish species, earlier life stages of fish and to study other small aquatic organisms. As an endangered species, delta smelt ( Hypomesus transpacificus ) are being intensively studied in the upper San Francisco Estuary ( CA , USA ). A crucial part of many of these studies is tracking delta smelt, which requires a distinctive mark on each individual or group of fish. Unfortunately, many of the experimental fish suffer inadvertent mortality, as delta smelt are very sensitive to environmental and handling stress. The purpose of this review was to synthesize the different tagging and marking studies on small fish and aquatic organisms and to evaluate the advantages and disadvantages of each method for applications on sensitive species such as delta smelt. This review suggests the most effective methods for tracking delta smelt are visible implant alphanumeric ( VIA ) tagging and adipose fin clips for subadult to adult fish and calcein marks for young life stages. Among these methods, only VIA tagging currently provides individual organism identification.