WWW.WA S .ORG • WORLD AQUACULTURE • MARCH 2022 21 term post-release survival without onerous post-release monitoring efforts. Releasing fish in habitats occupied by wild conspecifics does not guarantee effective stocking. Wild juvenile snook occupy tidal creeks over winter but a fall release would have minimal impacts on local snook populations. Specific release site features (e.g., habitat complexity) likely influenced post-release survival but additional environmental conditions need to be examined at a finer spatial scale to further refine release strategies. Juvenile snook may establish residency at small spatial scales, which translates to an increase in persistence and detectability, but was not consistently associated with improved survival. For more mobile or migratory estuarine species, survival could be underestimated if emigration is not considered, making it more important to monitor the full range of the species stocked. Further application will provide critical insights to guide future stock enhancement strategies, promote adaptive management of stock enhancement programs and maximize the benefits on receiving populations for large-scale stocking efforts. The feasibility of stock enhancement will improve with growing evidence that stocked fish survive and contribute to fisheries and monitoring that supports adaptive management will help ensure stocking of estuarine systems is conducted in a responsible and strategic manner. Artificial Propagation of Lamprey for Conservation and Control Mary L. Moser, Alexa N. Maine, John B. Hume, Kimmo K. Aronsuu, Ralph T. Lampman and Aaron D. Jackson There is a long history of artificial propagation of lampreys (Fig. 3), with recent developments driven by the need for research animals and for recovery of imperiled species. Lamprey culture initially produced specimens for the study of evolutionary development in vertebrates. More recently, artificially propagated larvae have been used to improve identification methods for native lampreys, study invasive sea lamprey Petromyzon marinus in the Laurentian Great Lakes, provide animals for genomic studies and for restoration and conservation. along the shoreline to detect fish throughout the water column (Fig. 2). Detections of tagged fish were used to generate resighting histories for the year following each release, and these were analyzed to estimate post-release survival and detectability using multistate open robust design models in programMARK (White et al. 2006), following an approach similar to that of Kendall et al. (2019). State-based models were needed to control for unequal detectability among individuals displaying residency and mobile post-release behaviors. Monitoring release sites with PIT tag antenna arrays resulted in a high proportion of unique fish resighted in this study (78 percent in fall, 80 percent in spring). For the fall release, 88 percent of the 135,332 detection events occurred within the first four weeks post-release and the number of fish detected decreased substantially during this time as only 64 individuals (6.7 percent) were detected after four weeks. In the first year after the spring release experiment, the decrease in the number of fish detected over time was not nearly as substantial as it was for the fall release, with 38 percent of the 127,525 detections occurring after four weeks, representing 192 individuals (20 percent of those released). Resighting histories generated from PIT tag antenna arrays were primarily explained by short-term differences in survival during the first few weeks after release and long-term patterns in detectability that reflect residency behaviors of juvenile snook. For both releases, apparent survival was a function of the interaction between a four- or five-week stocking effect and their post-release behavioral state, the region of release and the size of the fish at release, with time after release also being important for the spring release. Notably, over half of the mortality often occurred within the first week after release and survival of hatchery-reared snook was high beginning five to six weeks post-release. The highest survival rates were observed for individuals released in lower Phillippi Creek (Sarasota) in the spring, suggesting lower reaches of tidal creek systems provide ideal release locations for juvenile snook at this time. We demonstrated that monitoring stocking activities with PIT tag antenna arrays can be extended to open saline waters, models appropriately account for post-release behavioral states, and the results used to identify times and locations that promote short- ( C O N T I N U E D O N P A G E 2 2 ) FIGURE 3. Pacific lamprey Entosphenus tridentatus adult female (top), developing embryos (middle) and prolarva (bottom).
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