Estimating Fish Mortality Rates Using Telemetry and Multistate Models

Abstract

We simulated and evaluated multistate capture–recapture models to estimate mortality rates using telemetry data. Four field designs were considered: (A) fixed receivers to estimate total instantaneous mortality (Z), (B) manual searches to estimate instantaneous fishing (F) and natural (M) mortality, (C) fixed receivers combined with external high‐reward tags to estimate F and M, and (D) manual searches combined with external high‐reward tags to estimate M and fishing mortality rates associated with harvest (Fh) and catch‐and‐release death (Fcr) as well as the probability of death due to catch and release (α). Estimates generally appeared to be unbiased for a simulated study with five periods and releases of telemetered fish at the start of periods 1–4. Compared to estimating Z, larger sample sizes are needed to achieve reliable estimates of component rates (F and M). Estimates of component rates were more precise when that source of mortality was directly observed (M in design B, F in design C). The field design using fixed receivers and high‐reward tags should be especially useful in practice, because manual searches are not required to estimate F and M. Multistate models are useful for clarifying the connection between field observations and ecological processes. Reliable estimates of mortality rates, coupled with information on behavior, habitat use, and movement, make telemetry a highly valuable tool for improving fisheries management and stock assessment.

Using Radiotelemetry to Evaluate Poststocking Survival and Behavior of Large Fingerling Walleye in Three Iowa, USA, Lakes

“…An understanding of poststocking behaviors (e.g., depth use, dispersal, and home range) across a range of lakes with variable habitat and predator assemblages could provide insights into fish acclimation to natural environments under a range of conditions. Telemetry is a useful tool for understanding behavior and survival of fish (Hightower and Harris ) and is commonly used for adult Walleye (e.g., Eberts et al. ; Faust et al.…”

Estimates of Red Drum Mortality via Acoustic Telemetry

“…However, tags that are not within a fish or tags that are present within fish carcasses could move as a result of water flow, as has been shown in other studies (Muhametsafina et al. ; Hightower and Harris ). These tidal rivers do not experience high flow rates from rainfall or tidal influences, and two fish tags that were inferred surgery mortalities were detected constantly on a single receiver for the duration of the study.…”

“…Total mortality ( Z ) must be divided into natural mortality ( M ) and fishing mortality ( F ) for exploited species, and using telemetry studies as extensions of traditional mark–recapture designs is one way to obtain these mortality components (Hightower et al. ; Hightower and Harris ). This method can provide benefits over traditional tagging studies because (1) fish do not have to be physically recaptured and (2) multiple fish fates, including M and F , may be inferred from detection data (Hightower et al.…”

“…This method can provide benefits over traditional tagging studies because (1) fish do not have to be physically recaptured and (2) multiple fish fates, including M and F , may be inferred from detection data (Hightower et al. ; Hightower and Harris ). Furthermore, mortality estimation across multiple spatial and temporal scales may be possible, elucidating seasonal, regional, and environmental drivers of mortality (Bacheler et al.…”

Symposium Review: Using Electronic Tags to Estimate Vital Rates in Fishes

“…Since Hightower et al. (), Joseph Hightower has continued to develop new and exciting field and analytical approaches to estimate fish vital rates using electronic tags (e.g., Hightower and Harris ). Other researchers have built on the work of Hightower et al.…”