Advances in Fish Tagging and Marking Technology

<i>Abstract</i>.—Atlantic salmon <i>Salmo salar </i>smolts are stocked in the Penobscot River, Maine to supplement declining populations. Since 2000, approximately 550,000 hatchery smolts are annually released into the river, of which 32% of these (175,000) were marked with visual implant elastomer (VIE) tags indicating release time and location. Our study found that tag colors of adult returns were often misread due to confusion between green and yellow marks and between red and pink marks. Using data collected on mark readings in a controlled hatchery environment, we corrected for tag identification errors made in the field, thereby allowing adjustments to be made in the marked returns to accurately assess the number of returns from multiple stocking groups. When adult returns from multiple stocking groups were compared, significant differences were detected between stocking groups, including a three-fold difference between two of the stocking groups. Hence, a simple change in smolt stocking locations and times may be of value in the recovery of the Penobscot River salmon population.

Advances in Fish Tagging and Marking Technology

<i>Abstract</i>.—Large-scale fish tagging programs are becoming more popular as fishery managers realize the importance of including spatial structure in assessment and management models. Two recent EU-funded projects on plaice and cod have shown how information from electronic tags can be used to gain new insights and add value to historic tagging data. Highlights have been the demonstration of unexpected population sub-structuring in plaice, and the realization that cod behavior is very variable in response to regional environments. Success does not come without planning and management of staff, of data, and of expectations. We share our experiences from the last 10 years of electronic tagging to provide an up-to-date analysis of what makes a good tagging program, and how to get the most from it.

Advances in Fish Tagging and Marking Technology

<i>Abstract</i>.—Tagging studies have been a fundamental tool in fisheries science for over 100 years. During this time tags have progressed from simple markers through to sophisticated miniature computers capable of storing large amounts of data. Making sense of large amounts of spatial and temporal tagging data lends itself well to graphical interpretation. The Electronic Tag Support Systems (ETSS) team at CSIRO has developed a comprehensive visualization system to suit researcher and stakeholder (funding agencies, fishers, public) needs. Researchers are able to access and visualize the data through a proprietary (MapInfo) GIS package; stakeholders can visualize the data without the need for prior GIS knowledge through a menu-driven graphical web portal.

Advances in Fish Tagging and Marking Technology

<i>Abstract</i>.—In designing research programs, scientists may constrain development of sequential hypotheses because of perceptions about logistical constraints to using new technologies in monitoring or experimental design. Using trusted, familiar methods can supersede asking which hypotheses would have the greatest impact and what method(s) are required to test them. To help maintain a ‘problem-oriented’ approach, rather than a ‘methods oriented’ one, we could strive to remain aware of new innovations and applications in research; this is particularly so for tagging technology, when new methods emerge. Research enabled by recent innovations can be incorporated through collaborations with other scientists or by working directly with vendors to implement and refine new tag technologies and applications. Some tagging studies can be improved by using multiple marking methods (e.g. see recent applications of various tag technologies with common snook <i>Centropomus undecimalis </i>and red drum <i>Sciaenops ocellatus </i>in Florida to evaluate recruitment, mortality, and habitat use of different life stages; Adams et al. 2006; Bennett 2006; Marcinkiewicz, 2007; Brennan et al. 2008; Tringali et al. 2008). Here we consider a few case studies that have implemented a variety of tagging methods to explore poorly understood factors that mediate growth and survival and the effectiveness of hatchery releases to help replenish depleted marine fish stocks.

Advances in Fish Tagging and Marking Technology

<i>Abstract</i>.—A micro-controlled fish tag which records post-tagging lifespan was developed, tested as a prototype, and then evaluated in field applications for measuring survey life. The method of constructing the Tilt-Tag and the results of tank test trials on Chinook salmon <i>Oncorhynchus tshawytscha</i>, preliminary field trials on chum salmon <i>Oncorhynchus keta </i>are reviewed, and full-scale field applications on sockeye salmon <i>Oncorhynchus nerka </i>are presented. Survey life (SL) is an essential component for area-under-the-curve (AUC) estimation of Pacific salmon <i>Oncorhynchus </i>spp. spawning escapements. However, direct estimates of SL are often unavailable because the estimates mostly require extensive and costly tag-recapture programs. In this study, the Tilt-Tag was used to estimate SL by measuring the elapsed time from tagging until the fish came to rest permanently on its lateral or dorsal surface. Tilt-Tag derived estimates of SL, combined with specification of survey rules that were based on historical run-timing and stream temperature, reduced survey costs by approximately 50% when compared to conventional tag-recapture methods. Abridged details on how to construct the Tilt-Tag are provided so that researchers will be able to make their own tags.

Advances in Fish Tagging and Marking Technology

<i>Abstract</i>.—We deployed archival temperature loggers on juvenile and adult coho salmon <i>Oncorhynchus kisutch </i>and steelhead (anadromous rainbow trout) <i>O. mykiss </i>over both the freshwater and marine portions of their lifecycle in order to study their movements and thermal preferences. Beginning in 2003, loggers were deployed on juvenile coho salmon and juvenile and adult steelhead in a small central California coastal stream. A tag recovery from a coho salmon indicates the fish experienced variable temperatures on a daily to weekly basis in the marine environment (mean 13.3°C, range 10–18°C). Tags recovered from steelhead indicate use of a cooler, more stable, thermal habitat window in the marine environment (mean 11.0°C, range 8–14°C), often with little fluctuation over a period of weeks to months, and most thermal changes occurring at the seasonal time scale. Comparisons of steelhead data with sea surface temperature data suggest a northern migration out of the California Current to a narrow band of habitat that fluctuates between the southern boundary of the Bering Sea and north of the 40th parallel. In the shallow freshwater environment, steelhead appeared to be at the mercy of stream temperatures. However, in the estuary, where thermally variable habitats were available, steelhead used a surprisingly broad temperature range, including entering water thought to challenge their thermal tolerances (>20°C) even when cooler waters were available. Temperature loggers recovered on a local beach and island indicate tagged fish were consumed in the estuary by warm-blooded predators. All of these data coupled with a larger number of passive integrated transponder (PIT) tags, are helping to identify discrete habitats fish are using, exact dates of ocean entry and return, and enhance our understanding of marine survival and predation. Finally, archival tags may be useful in understanding habitat use of pelagic long-migrating species like steelhead, by tracking individuals in areas where other tagging technologies are poorly suited.

Advances in Fish Tagging and Marking Technology

<i>Abstract</i>.—This study describes an improved method that decreases tracking time but increases accuracy and precision for the fine-scale location of radio tags by reducing the receiving antenna efficiency. Test tags (48–49 MHz) were hidden in a lowland river and independently located by boat tracking using both the antenna reduction method and standard triangulation techniques. The antenna reduction method was found to be faster and more accurate, locating transmitters to within 0.19 ± 0.13 m (mean ± SE) of their actual location (error range 0–1.50 m) compared to 19.53 ± 4.81 m (error range 0–70.00 m) using triangulation. This simple approach can be applied to a wide range of radio telemetry studies and avoids many of the major sources of location error associated with triangulation including minimising the distance between the transmitter and receiver and avoiding the potential need for mapping.

Advances in Fish Tagging and Marking Technology

<i>Abstract</i>.—Radio telemetry is now considered a standard tool for fisheries professionals studying fish in freshwater systems. However, interest in radio telemetry technology may be waning in popularity relative to other technologies such as acoustic telemetry and passive integrated transponders, which have recently become popular for tracking studies in freshwater. The purpose of this paper is to identify the unique characteristics of radio telemetry that continue to make it an extremely powerful tool for elucidating the fundamental biology of aquatic organisms, particularly those living in shallow, fluvial habitats, and in providing information to enable effective management and conservation of aquatic resources. By evaluating the peer-reviewed literature on radio telemetry in aquatic systems over a ten year period, we summarized the advances in fisheries science owing to radio telemetry and identified trends related to study design, tagging techniques, and tracking strategies. We also identified research questions and management needs that cannot be effectively addressed using technologies other than radio telemetry, with main emphasis on hydropower development, microhabitat use and movements, mortality, predation, winter biology, natural history studies of imperiled fish in developing countries, and studies in habitats where physical characteristics restrict the usefulness of other techniques. We emphasize that it is important for radio telemetry practitioners to not dismiss simple manual tracking studies where individual tagged fish are discriminated by using discrete frequencies. Indeed, such an approach can yield insight that is not possible with fixed stations alone, and is particularly useful for developing countries where capacity and finances may not exist for deployment of fixed stations. By characterizing and clarifying the actual and potential role for radio telemetry within the broader landscape of tagging and telemetry technologies, we hope to enable telemetry practitioners to make informed decisions regarding the optimal choice of tagging technology when designing and executing telemetry studies in freshwater systems. We submit that radio telemetry is not getting washed downstream, but there are now simply more technological options for researchers interested in the study of freshwater fish.