Using Acoustic Telemetry to Estimate Weakfish Survival Rates along the US East Coast

The Weakfish Cynoscion regalis, an economically important species, has declined over the last 30 years, corresponding with an increase in total mortality according to the most recent stock assessment. We estimated estuarine-specific and coastwide apparent survival of Weakfish by using a Cormack-Jolly-Seber model to provide insights into the spatiotemporal component of mortality. Telemetered Weakfish (n = 342) were released across five estuaries ranging from North Carolina to New Jersey between 2006 and 2016. In estuaries from Delaware Bay and northward, egress peaked around the third week of September; in North Carolina, egress peaked by the first week of November. For three estuaries with adequate sample sizes, apparent survival estimates were similar and a joint model including all telemetered Weakfish estimated an extremely low annual apparent survival rate of 0.001 (95% credible interval [CrI] = 0.002-0.0003) or annual apparent instantaneous total mortality of 7.25 (95% CrI = 6.28-8.05). At a minimum, 61% of telemetered Weakfish emigrated in the fall, but only 2 of 149 fish with long-lived transmitters were detected as returning to estuaries the following year. This is a small proportion for a fish that exhibits spawning site fidelity. We conclude that the disappearance of telemetered Weakfish represents mortality that occurs between emigration and the spring spawning period, potentially during overwinter periods on the continental shelf. Our study provides insights into the magnitude, timing, and location of Weakfish loss and facilitates an improved understanding of Weakfish population dynamics for use in stock rebuilding.