Progress Meets Resistance: Modernizing Striped Bass Science

One number has quietly shaped striped bass management for nearly 30 years: 9% release mortality. As of summer 2026, the Striped Bass stock assessment benchmark process is in full swing and the implications of release mortality estimates have never been greater. The following blog examines the science behind catch-and-release mortality, why newer research is challenging long-held assumptions, and what that could mean for momentous assessment. If you’re looking to get technical and better understand how science drives management, look no further.

Our Association has long defended ASMFC scientists and staff for trying their best to balance a difficult situation of sector demands and an absurdly political (and downright volatile) striped bass management board. That being said, if they do not fully recommend integrating the most comprehensive striper release mortality research ever done, in place of a study that explicitly states it should not be used for management purposes, this staff will lose all credibility during one of the most critical moments for striped bass management. Now, let’s jump in…

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To establish a lay of the land, the benchmark process takes precedent as it provides the opportunity for the Striped Bass board, and technical committees to assess and consider methodologies that compose the framework to estimate and manage striped bass populations moving forward. Part of this process are discussions considering a change in stock assessment modeling framework, shifting from a statistical catch at age, Age Structured Assessment Program (ASAP) – a deterministic, fixed effects model historically used; to another statistical catch at age model, the Woods Hole Assessment Model (WHAM) – a probabilistic, multi-state model, that allows key parameters to be handled as random effects, i.e., allowing the model to treat these stochastically, accounting for spatial and temporal variance of human dimensions, environmental variables, and striped bass population dynamics that is absolutely present across the Striped Bass’ management range from Maine to North Carolina. 

This discussion builds on these topics discussing a prominent conversation occurring during the ongoing 2027 benchmark process. Rather than emphasizing stock assessment frameworks like ASAP vs. WHAM, this conversation shifts focus to a small, but mighty estimate known as post-release mortality rate, aka C&R mortality.

Now to provide a little background on this, we have to take a step back and remember that fish mortality is described by two broad categories, natural mortality (M), and fishing mortality (F), when combined you get total mortality (Z). At a finer scale, catch and release (C&R) mortality pertains to the hook and release interaction within the recreational fishery, where its estimate informs the maximum likelihood equation used to calculate overall fishing mortality (F) in applied statistical catch at age frameworks. Realistically, F cannot be described by a simple formula, but for the sake of this discussion, a conceptual equation where fishing mortality (F) as a function of catch can be observed as: 

F_Catch = Comm. Harvest + Discards + Rec. Harvest + C & R Mortality Rate (%) 

C&R Mortality = (Recreational Releases x estimated C&R mortality rate %)

Estimated C&R Mortality Rate (%) = 9% (Diodati and Richards, 1996)

Visualizing this conceptual formula provides the opportunity to understand that estimated C&R mortality rate (%) has a corresponding effect on the calculated F estimate used to inform stock assessment models, regardless of statistical framework, e.g., ASAP, WHAM, etc. 

Post-Release Mortality Studies

Diodati and Richards, 1996:

Historically, the ASMFC has estimated C&R mortality from a fixed assumed C&R mortality rate of 9% that is applied to estimates of released fish from the recreational sector. The fixed assumed 9% rate estimated is derived from the Diodati and Richards, (1996), Mortality of Striped Bass Hooked and Released in Salt Water study. The study obtained striped bass from a trap-net operator from Newport, Rhode Island. Three traps collected fish to be used as samples included in the study over a 20-day period, where netted fish were placed in holding tanks, then during transport to shore, internal Floy tags were inserted to each fish for unique identification. Once transported to shore, fish were then transferred to a second holding tank before being placed into a tank truck for delivery to the study site (Diodati and Richards, 1996). Average time of transport from collection area to study site was reported as 5hr (range, 4.5hr – 6hr), where a sub-set of collected fish (N=333) where then placed into a 3-m (9.8ft) deep net pen within the study area pond to assess mortality derived from transport and tagging efforts. These fish were then released into the study pond (impoundment), after a timeframe ranging from 24hr – 5 days creating a total sample size of striped bass released to the pond to (N=1,015). C&R mortality was then assessed from a hooking experiment that spanned five weeks and four days (June 21 – July 30) where fifty (N=50) volunteer anglers were selected to conduct rod and reel fishing. Angler avidity, gear type, fight-time, hook site, handling time, and released condition were recorded by on-site technicians accompanying anglers. 

Ultimately, the study estimated striped bass hooking mortality ranged from 3-26%, with an estimated overall post-release mortality rate of 9%. Notably out of the 1,015 striped bass that were released into the pond, just 17% of the total study population (N=173 hooked fish) was included in the logistic regression model fit with maximum likelihood estimation to develop the post-release mortality estimates. Condition of non-hooked and hooked fish was reported decline within the pond throughout the study timeframe suggesting that while it was suggested that hooking events influence condition decline in fish, the environmental variables associated with the study design itself further exacerbated these observations, especially when considering the study was conducted during the heat of summer, forage availability was reported a limiting factor, and the pond provided zero thermal refugia for stressed fish to properly recover, further failing to replicate realistic responses of fish to catch and release interactions that would occur in nature. Additionally, striped bass are an anadromous fish, migratory fish that is managed from the states of Maine to North Carolina. Diodati and Richards, 1996 report the limitations of the extreme spatial and temporal constraints of the study by stating: 

“Hooking mortality estimated from an experiment cannot predict population mortality unless experimental conditions represent those encountered in the wild. For species with a broad geographic range, such as anadromous Atlantic striped bass, it seems unlikely that mortality recorded from an experiment would equal that of the population over a time period of interest (typically a year).”

“To estimate population mortality, information would be needed on regional patterns in recreational fishing over the time period of interest. One could collect such information by adding questions regarding significant hooking parameters to existing creel surveys (e.g., USDOC 1991).”

“Our present model would not be sufficient for estimating coastwide hooking mortality of striped bass, as it does not include effects of such factors as fish size and environmental variables (temperature, salinity) on mortality. Developing a comprehensive model and applying it to coastal populations could be useful in shaping appropriate management strategies for important recreational species such as striped bass.”

Diodati and Richards, 1996 conducted an influential study establishing literature on striped bass estimated C&R mortality rates. This discussion does not discredit their work in any capacity, but rather is intended to challenge those that have used it beyond its timeframe of being reasonably described as best available science. Once again, this is not a knock to their work, but rather a nod to the deductive scientific framework itself – ask questions, form and test hypotheses, and gain biological inference to advance understanding. Diodati and Richards’ work laid the foundation for this discussion, but as they described: further hypotheses, and broader studies are critical to effectively understand realistic population level striped bass post-release characteristics. Considering the extent, and number of variables that can – and do change over time (several decades in this case), including ecological variables (e.g., habitat availability, water temperature, predator-prey interactions, population dynamics, i.e., variable annual recruitment and spawning success, etc.), and social variables (e.g., angling effort, gear types, recreation-commercial user group interactions, etc.) it is paramount to build upon Diodati and Richards’ efforts with modern scientific methods and applications to more accurately understand the responses of striped bass subjected to modern fishery practices, and environmental conditions.

Nelson et al., 2025 (Final Report Prepared for NOAA):

Considering the Chesapeake Bay’s role in supporting a dominant portion of the Atlantic striped bass spawning stock, Nelson et al. 2025 set objectives to estimate C&R mortality of Chesapeake Bay striped bass through realistic catch and release interactions, and additionally aimed to determine the effect temperature has on seasonal variability of C&R mortality. In an effort to realistic reflect interactions of the recreational fishery, the study utilized a recreational charter captain for rod and reel sampling. Fishing occurred across three seasons: Spring (N=50 fish), Summer (N=28 fish), and Fall (N=22 fish) comprising the study’s total sample size of N=100 fish. Both active and passive acoustic telemetry data were collected to assign observed weekly fish statuses after released. Bayesian multi-state mark recapture models were used to estimate C&R mortality, and detections from active and passive tracking of acoustic telemetry tagged fish were used to establish observation histories and known states of tagged individuals at a given week post-release. 

The relationship between C&R mortality and temperature was tested through the implementation of another Bayesian multi-state mark recapture model where instead of a season variable like what was included in the initial model, temperature covariates were incorporated using both mean weekly temperatures post-release and temperature at release to determine if C&R mortality was significantly related to temperature. Additionally, the relationship of temperature and the sum of modeled covariates were also evaluated. 

Ultimately, the study suggested an overall C&R mortality estimate of 6.9%. Additionally, seasonal trends were identified with summer exhibiting the highest C&R mortality rate (11.3%), followed by spring (4.9%), and lastly fall (0.7%). Results regarding the effect of temperature on C&R mortality rate further supported literature, suggesting 25°C (77°F) as an identified likely temperature threshold for striped bass stress, and suggests increasing temperature >25°C exacerbates C&R mortality rates.

Dean et al., under review (UR):

A three-phase approached was used for this study where acoustic telemetry tagging, citizen science, and a coastwide angler survey were all applied. Fish were caught by scientist with various rod and reel gear types, then uniquely identified with an acoustic telemetry tag, and reported to be handled for on average less than three minutes before being released back into the water. Acoustic telemetry tagging (N=349 fish) was used to estimate C&R mortality rate as a function of a described condition score based on assessment of injury and vitality. Citizen science provided observations of release conditions (N=8,349 fish) paired with biological, environmental, and fishing variables, informed a developed machine learning model to estimate and predict C&R mortality rate. Fishery-scale patterns were described for each predictor by assembling representative datasets, including a coastwide angler survey (N=4,964 anglers) that quantified regional patterns in tackle configuration. 

The study found that C&R mortality as a function as a size and age exhibited a strong relationship, and further supported prior literature reporting that natural baits and lures with treble hooks also led to significantly elevated C&R mortality rates. Results suggested that the C&R mortality rate for the recreational fishery is on average 4%, a rate 56% less than the historically assumed 9%. 

Management Implications

Assuming a higher C&R mortality rate estimate, e.g., 9% (Diodati and Richards, 1996) compared to a lower estimated rate, e.g., 4% (Dean et al., UR), or 6.9% (Nelson et al., 2024) statistically suggests recreational anglers contribute to a significantly greater amount of striped bass deaths, than what realistically occur in nature as a product of responsible catch and release interactions. Suggested results from these recent studies strongly support the idea that historical overestimation of C&R mortality has occurred, significantly skewing manager’s understandings of striped bass population dynamics and associated fishery human dimensions. Considering how this applies both ecologically and to the active management of Striped Bass in a primarily catch-and-release fishery: if catch-and-release mortality rates are significantly lower than historically assumed by a wide margin, this likely suggests several possible scenarios: 

(1) The estimated Striped Bass Spawning Stock Biomass (SSB) is likely more inaccurate than previously assumed.

(2) Overestimation of recreational C&R mortality rates could mask the realistic effects of other striped bass mortality variables occurring in both (M) and (F). 

(3) There is a high probability, consecutive failed spawns, minimal recruitment, and critical habitat availability are greater drivers of coast-wide population dynamics than previously assumed.

(4) The fixed constant 9% C&R mortality rate historically assumed, fails to account for modernization of the Atlantic striped bass fishery, and spatial-temporal variation across the fishery range – including angler effort across region and time, environmental covariates, and fish size classes.

Despite the logical, and ecologically relevant topics discussed, the ASMFC’s technical committees appear rather reluctant to incorporate best available science, and in some cases – even acknowledge it (Nelson et al. 2025 has not been recognized during any technical committee meeting minutes). The Dean et al. UR, study has been incorporated into the benchmark process to be reviewed for possible implementation in the stock assessment moving forward, but a large – and highly concerning question mark remains if it actually will. Throughout several meetings, Dean et al. UR, has endured scrutiny on the only thing the striped bass technical committee could form a conversation on – uncertainty. While uncertainty is a very real, and necessary topic to be discussed when regarding any quantitative technique, it should be understood when dealing with applied research encompassing both ecological, and statistical methods, uncertainty will always be inherent in some capacity. Walters and Martell 2004, note that part of advancing quantitative techniques to better understand realistic interactions in nature is working towards methods that increase inference, and reduce uncertainty. Now, it is also understood that no amount of modelling or measurement can offset certain vectors of uncertainty especially when considering natural variation through spatial and temporal components, but relatively robust inference can still be gained and applied to management if adequate study design, data acquisition, and quantitative methods and assumptions were conducted. 

When considering how uncertainty relates to this discussion, when comparing study designs, Diodati and Richards 1996 methods least mimic realistic interactions in nature between recreational anglers and striped bass. Additionally, the incorporated study design failed to mimic spatial and temporal variation effectively occurring to the natural striped bass management unit that the estimated mortality rate of 9% has been long applied to – even after the prior mentioned limitations explicitly described in the manuscript’s discussion section. It can be argued that the relatively small sample size of only (N=173 fish) were used to inform the maximum likelihood logistic regression model used to estimated the now famous C&R mortality rate estimate. In contrast, both Dean et al. UR, and Nelson et al. 2025 studies applied Bayesian mark-recapture methods to assess C&R mortality of striped bass fit with acoustic telemetry tags. Both studies employed methods that very similarly mimic realistic interactions of recreational anglers and striped bass in nature while capturing both spatial and temporal variation that influenced predictor variables associated with estimated C&R mortality estimates. When considering estimates and their application to management of the striped bass fishery, based upon study design and sample sizes, it can be strongly suggested that Dean et al. UR, and Nelson et al. 2025 have much lower inherent uncertainty associated with estimated C&R mortality rates compared to Diodati and Richards 1996. Additionally, considering the level of concern ASMFC exhibited on uncertainty regarding Dean et al. UR, an argument can be made for how uncertain MRIP estimates have been historically, and their choice to use fish scales (which fall off, regenerate, and are regarded in the literature as one of the most uncertain methods to age fish), rather than otoliths to inform age-growth calculations and the age-length keys that form a central foundation of quantitative fishery science and management. 

It should be understood, this discussion is part of a critical examination of the ASMFC technical committees’ actions, both historically and throughout the current benchmark process. Its purpose is to present accountability within a governing body charged with stewardship of a billion-dollar fishery. Unfortunately, it is not uncommon for technical scrutiny to be misread as ad hominem attacks. That misreading itself is revealing: exposing a lack of humility and unwillingness to engage differing viewpoints. When those responsible for management refuse to distinguish legitimate accountability from personal attack, they close off the very dialogue needed to advance understanding – and, ultimately, to manage resources responsibly.

Next Steps

Looking ahead, the scheduled MRIP recalibration and discussed potential shift from the ASAP stock assessment framework to WHAM could significantly alter current fishery assumptions, reshaping our understanding of the realistic status of the Atlantic striped bass population, based on the new estimates and methods. With this consideration, in order to effectively, and accurately assess fishery status moving forward, it is pertinent that managers consider, and incorporate objective, best available science to guide the future applied management framework of the Atlantic striped bass fishery. Our Association will continue to be present in scheduled ASMFC meetings, and provide transparent, up to date reports of ongoing benchmark discussions to the public. 

Literature Review: 

Dean, Micah J., et al. “Revisiting the Recreational Release Mortality of Atlantic Striped Bass.” Manuscript submitted for publication to Fisheries, 2026. SSRN, 3 July 2026.

Diodati, Paul J., and R. Anne Richards. “Mortality of Striped Bass Hooked and Released in Salt Water.” Transactions of the American Fisheries Society, vol. 125, no. 2, 1996, pp. 300–07. https://doi.org/10.1577/1548-8659(1996)1252.3.CO;2.

Nelson, T. Reid, et al. “Estimating recreational catch and release mortality of Striped Bass”. NOAA Technical Memorandum, National Oceanic and Atmospheric Administration, 2025

Walters, Carl J., and Steven J. D. Martell. Fisheries Ecology and Management. Princeton University Press, 2004.