Fisheries Release Mortality:

Identifying, Prioritizing, and 

Resolving Data Gaps

L. R. Benaka, L. Sharpe, L. Anderson, K. Brennan, J. E. Budrick, 

C. Lunsford, E. Meredith, M. S. Mohr, and C. Villafana

U.S. Department of Commerce

National Oceanic and Atmospheric Administration

National Marine Fisheries Service

NOAA Technical Memorandum NMFS-F/SPO-142

July 2014

Fisheries Release Mortality:

Identifying, Prioritizing, and Resolving Data Gaps

L. R. Benaka, L. Sharpe, L. Anderson, K. Brennan, J. E. Budrick,

C. Lunsford, E. Meredith, M. S. Mohr, and C. Villafana

NOAA Technical Memorandum NMFS-F/SPO-142

July 2014

U.S. Department of Commerce

Penny S. Pritzker, Secretary 

National Oceanic and Atmospheric Administration

Kathryn D. Sullivan, Administrator

National Marine Fisheries Service

Eileen Sobeck, Assistant Administrator for Fisheries
ii

Recommended citation:

Benaka, L. R., L. Sharpe, L. Anderson, K. Brennan, J. E. Budrick, C. Lunsford, E. Meredith, M. 

S. Mohr, and C. Villafana. 2014. Fisheries Release Mortality: Identifying, Prioritizing, and 

Resolving Data Gaps. U.S. Dep. Commerce, NOAA Tech. Memo. NMFS-F/SPO-142, 84 p.

Copies of this report may be obtained from:

National Marine Fisheries Service

National Oceanic and Atmospheric Administration 

National Observer Program (attn. Lee Benaka)

1315 East-West Highway, 12th Floor

Silver Spring, MD 20910

Or online at:

http://spo.nmfs.noaa.gov/tm/ 
iii

Table of Contents

Dedication.........................................................................................................................v

Executive Summary........................................................................................................... vi

1. Introduction..............................................................................................................1

2. Background..............................................................................................................3

3. NMFS-Funded Release Mortality Research by Region...........................................4

3.1 Northeast......................................................................................................4

3.2 Southeast....................................................................................................11

3.3 West Coast .................................................................................................23

3.4 Alaska ........................................................................................................27

3.5 Pacific Islands............................................................................................29

4. How Release Mortality Assumptions Are Incorporated into Stock Assessments.30

5. Approaches to Developing Revised Release Mortality Assumptions...................32

5.1 Delphi Technique.......................................................................................32

5.2 Model-Based Approach .............................................................................33

6. Identification and Prioritization of Data Gaps.......................................................36

7. Identification and Prioritization of Species-Specific Research Needs ..................39

7.1 West Coast Examples ................................................................................40

7.2 Southeast Examples...................................................................................42

7.3 Northeast Examples...................................................................................43

8. Best Practices and Techniques for Release Mortality Research............................45

8.1 Outreach.....................................................................................................45

8.2 Tagging ......................................................................................................46

8.3 Arrays.........................................................................................................47

8.4 Estimating Mortality Rates Using Chamber Studies, Cage Studies,

and Acoustic Tagging ................................................................................47

8.5 Application of Mortality Rates in Management ........................................48

9. Identifying Components of a National Release Mortality Science Strategy .........50

10. Conclusion: Next Steps for Addressing Broader Release Mortality Issues..........52

11. References..............................................................................................................53
iv

Appendix A Release Mortality Workshop Attendees (September 25-26, 2013)..............56

Appendix B Summary of NMFS-Funded Release Mortality Research by Region ..........57

Appendix C Compilation of Release Mortality Estimates Used by NMFS......................66
v

Dedication

The authors would like to dedicate this report to the memory of Karen M. Burns. Beginning in 

the 1990s, Dr. Burns conducted numerous helpful and influential studies of release mortality in 

Southeast reef fishes. She was missed during the development of this report, but her work 

continues to inspire release mortality research. 
vi

Executive Summary

Recreational and commercial fisheries face continued effort restrictions due to high fishing 

mortality and slow stock rebuilding processes. Regional fishery management councils have 

implemented short fishing seasons, closed areas, species-specific non-retention measures, and 

size limits in response to overfished declarations. Under these restrictive management systems, 

release mortality and barotrauma can occur, which impedes the rebuilding of overfished stocks. 

Some fishermen believe that the use of fishing practices and technologies designed to minimize 

barotrauma and post-release mortality should reduce overall fisheries mortality and in turn lead 

to increased fishing opportunities. 

This report describes research projects addressing release mortality that were funded by NOAA’s 

National Marine Fisheries Service (NMFS) from 1999 to 2013. The projects highlighted in this 

section are not a complete accounting of all NMFS-funded release mortality research during this 

timeframe, but these projects do reflect the large majority of projects funded and research areas. 

The number of NMFS-funded research projects varies by region: Northeast (17), Southeast (24), 

West Coast (8), Alaska (4), and Pacific Islands (1).

This report focuses on various approaches to incorporating release mortality assumptions into 

stock assessments, as well as techniques that have been used in the Northeast (Delphi Technique) 

and the West Coast (model-based approach) to develop revised release mortality estimates.

In September 2013, scientists from within and outside of NMFS attended a workshop to help 

NMFS identify and prioritize data gaps related to discard mortality estimates and related stock

assessment issues. Workshop attendees identified and prioritized several important release 

mortality data gaps, including:

• Development of baseline discard mortality information, including an understanding of 

underlying factors and their interactions.

• Measurement of release mortality in fishery, as opposed to lab, conditions.

• Development of reliable and robust proxies for mortality (both short- and long-term).

• Examination of unaccounted escapement mortality.

• Identification of optimal sampling designs for accuracy and precision of discard mortality 

estimates.

• Communication of how discard mortality estimates are calculated and used, and how they 

affect stock assessments, annual catch limits, and management.

Workshop participants agreed on a list of seven high-priority criteria that should help direct 

scientists and managers in focusing release mortality resources on particular species. This report 

discusses several species in terms of these high-priority criteria. This report also discusses best 

practices and techniques related to release mortality research, especially effective outreach 

efforts related to release mortality research, as well as tagging and the related issue of acoustic 

arrays. Finally, this report identifies some components of a national release mortality science 

strategy and describes next steps for addressing broader release mortality issues.
1

1. Introduction 

Recreational and commercial fisheries face continued effort restrictions due to high fishing 

mortality and slow stock rebuilding processes. The National Oceanic and Atmospheric 

Administration’s (NOAA) National Marine Fisheries Service (NMFS) is committed to rebuilding 

overfished fish stocks. The NMFS Status of Stocks 2012 Report identified several important 

recreational and commercial fish stocks as overfished, including: Atlantic cod; Northeast winter 

and yellowtail flounder stocks; various Atlantic marlin, tuna, and sharks; red snapper in the 

South Atlantic and Gulf of Mexico; and some Pacific rockfish stocks. Regional fishery 

management councils have implemented short fishing seasons, closed areas, species-specific 

non-retention measures, and size limits in response to overfished declarations. Under these 

restrictive management systems, barotrauma and release mortality can occur, which impedes the 

rebuilding of overfished stocks and can limit fishing opportunity. 

The term “release mortality” refers to the incidence of mortality after a fish has been discarded. 

(“Discard mortality” is often an interchangeable term.) A variety of factors can increase release 

mortality, including how the fish is handled and whether it is exposed to air, is injured during the 

fishing process, or experiences thermal shock during ascent. Release mortality can occur soon 

after discarding, due to severe injury or immediate post-release predation, or it can be prolonged;

for example, if a fish’s internal organs have been damaged prior to release, mortality caused by

starvation can take a week or longer. In addition, the concept of release mortality encompasses 

“boarding morality,” which occurs when a fish is dead or near-dead when it is brought on board 

and then subsequently discarded. 

“Barotrauma” results from a change in pressure as some deep-water fish, especially fish with 

physoclistous gas bladders, are rapidly brought to the surface. The symptoms of barotrauma, 

including stomach eversion and bulging eyes, have been described extensively in literature, 

especially for Pacific rockfish (for example, Jarvis and Lowe 2008, Hannah et al. 2012). 

Fishermen around the country have adopted various fishing practices, including venting and 

descending devices, which are designed to minimize the effects of barotraumas. These methods 

have only been tested for success or ease of use for a handful of species to date. 

Where they have been tested, descending devices have been shown to substantially reduce 

mortality due to barotrauma or predation and thus aggregate release mortality (Jarvis and Lowe 

2008, Hannah et al. 2012, PFMC 2012, PFMC 2013, PFMC 2014). This reduction in mortality 

has been quantified for three species of West Coast rockfish, and these mortality rates will be 

incorporated into recreational fisheries management systems in Washington, Oregon, and 

California for 2013 and beyond (PFMC 2014). Further research may lead to accounting for 

reduced mortality in additional species and deeper depths when a descending device is used.

The recreational fishing community has raised the issue of barotrauma and recreational release 

mortality as a concern over the past few years. Fishermen and managers have developed and 

promulgated best practices designed to reduce post-release mortality (e.g., through the FishSmart 

website www.fishsmart.org). Barotrauma and release mortality also are concerns in commercial 

fisheries. Some fishermen believe that the use of fishing practices and technologies designed to 
2

minimize barotrauma and post-release mortality should reduce overall fisheries mortality and in 

turn lead to increased fishing opportunities. 

Fisheries release mortality is a concern not only in the United States, but also in Europe. In 

response to a request from the European Commission, the International Council for the 

Exploration of the Sea established a Workshop on Methods for Estimating Discard Survival in 

January 2014. This Workshop was tasked to, among other things, (1) develop guidelines and, 

where possible, identify best practices for undertaking discard survival studies; (2) identify 

approaches for measuring and reducing, or accounting for, the uncertainty associated with 

mortality estimates; and (3) critically review current estimates of discard mortality (ICES 2014).

Fishermen and managers are asking what changes in management, especially related to quotasetting and fishery restrictions, should occur if best practices and technologies are being used to 

reduce post-release mortality and the effects of barotrauma. If more fish released or discarded in 

recreational and commercial fisheries are likely to survive, then long-standing release mortality 

assumptions used for fisheries management and stock assessments may need to be re-examined. 

Ultimately, fishermen expect that they should be allowed increased access to fish if their fishing 

practices lead to an improvement in survival rates for discarded or released fish. Alternatively,

reduced mortality will help rebuild stocks faster than otherwise, although using estimated 

conservation benefits for stock rebuilding or increasing fishing opportunities for healthy stocks 

that co-occur with overfished species is a policy decision for each regional fishery management 

council.

The intent of this paper is to review release mortality initiatives by region; identify, prioritize, 

and try to resolve data gaps; and identify components of a national post-release mortality science 

strategy. This paper also includes a discussion of best practices and techniques for release 

mortality research.
3

2. Background

NMFS has been increasingly focused on best fishing practices to reduce release mortality and 

barotrauma since the late 2000s. In June 2008, NMFS and the Gulf of Mexico Fishery 

Management Council implemented Amendment 27 to the Fishery Management Plan for the Reef 

Fish Resources of the Gulf of Mexico. This amendment required the use of non-stainless-steel 

circle hooks when using natural baits to fish for Gulf of Mexico reef fish, and it required the use 

of venting tools and dehooking devices for fishermen participating in the commercial and 

recreational reef fish fishery.

Outreach and education efforts regarding the use of descending devices to mitigate mortality of 

discarded West Coast rockfish started in 2007. Since then, more than 50,000 copies of the

“Bring That Rockfish Down” brochure, and hundreds of descending devices, have been 

distributed to anglers, tackle shops, and fishing clubs throughout California by the California 

Department of Fish and Wildlife, in collaboration with California Sea Grant and fishing clubs. 

Similar outreach was conducted soon after in Oregon and Washington, and efforts in all three 

states are expected to continue to educate the fishing public and increase documented rates of 

descending device use. 

In September 2009, NMFS initiated a Recreational Fisheries Initiative to strengthen its 

partnership with the saltwater recreational fishing community. This initiative led to an April 

2010 Recreational Saltwater Fishing Summit and an October 2010 Recreational Saltwater 

Fisheries Action Agenda. The Action Agenda included five “signature issues,” one of which 

focused on cooperative research and monitoring, including the engagement of the recreational 

community in addressing barotrauma issues through a joint NMFS–stakeholder workshop.

Beginning in 2011, NMFS funded an initiative called FishSmart—a sportfishing-driven program 

focused on communication with anglers, researchers, and partners. In March 2011, FishSmart 

held a National FishSmart Workshop on Improving the Survival of Angler-Caught and Released 

Fish, which focused on barotrauma. FishSmart subsequently held three regional workshops on 

improving survival of angler-caught and released fish in recreational fisheries for the Gulf of 

Mexico/South Atlantic (April 2012), Pacific (May 2012), and Mid-Atlantic/New England 

(March 2013).

In March 2013, the NMFS National Policy Advisor for Recreational Fishing provided resources 

to the NMFS Office of Science and Technology to develop this white paper. The development 

process for this white paper included a September 2013 workshop attended by scientists from 

within and outside of NMFS, which was designed to provide background information for this 

white paper. Appendix A lists the workshop attendees.
4

3. NMFS-Funded Release Mortality Research by Region 

This section describes research projects addressing release mortality that have been funded by 

NMFS since the late 1990s. This section’s projects are not a complete accounting of all NMFSfunded release mortality research during this timeframe, but these projects do reflect the large 

majority of projects funded and research areas. Appendix B summarizes these research projects 

in a table.

3.1 Northeast 

3.1.1 Past Projects

3.1.1.1 Discard Mortality Estimation of the Southern New England Flatfish Complex using 

Reflex Action Mortality Predictor (RAMP) Methods

This Cooperative Research Program project, completed in 2012, examined factors related to 

discard mortality for yellowtail flounder (Limanda ferruginea), winter flounder 

(Pseudopleuronectes americanus), and windowpane flounder (Scophthalmus aquosus). The 

Southern New England Mid-Atlantic yellowtail flounder stock has a history of substantial 

discards, and the current stock assessment assumes 100% discard mortality. This project used a 

controlled experimental trawl to test seven reflex actions from stressed and unstressed yellowtail 

flounder. Tow time and air exposure were tested to identify their effect on mortality. Mortality 

was significantly related to reflex impairment. Exposure to air was the more influential stressor 

in the survivability of yellowtail flounder, suggesting that the discard mortality could be reduced 

in the fishery by limiting the time the fish are exposed to air on deck. 

For winter flounder, investigators used a controlled experimental trawl to test seven reflex 

actions from stressed and unstressed winter flounder. Tow time and air exposure were tested to 

identify their effect on mortality. Mortality was significantly related to reflex impairment, but 

neither air exposure nor tow time significantly affected the survivability of winter flounder. 

Although air exposure did not significantly affect survival, none of the experimental fish exposed 

to air for 15 minutes or more survived, suggesting that the discard mortality could be reduced by 

limiting the length of time the fish are on a dry deck. 

Likewise, for windowpane flounder, investigators used a controlled experimental trawl to test 

seven reflex actions from stressed and unstressed windowpane flounder. Tow time and air 

exposure were tested to identify their effect on mortality. Mortality was not significantly related 

to reflex impairment, and neither air exposure nor tow time significantly affected the 

survivability of windowpane flounder. These results indicate that windowpane flounder are 

highly susceptible to the stresses of the commercial fishing process and are unlikely to survive 

discarding regardless of the sampling or handling method. A paper based on this research 

(Barkley and Cadrin 2012) applied RAMP monitoring to demonstrate a 42–73% range of

yellowtail flounder discard mortality estimates from the southern New England trawl fishery.
5

3.1.1.2 Optimizing the Georges Bank Scallop Fishery by Maximizing Meat Yield and 

Minimizing Bycatch

This Atlantic scallop research set-aside project, completed in 2012, attempted to determine 

discard mortality rates for yellowtail and winter flounder in the Georges Bank scallop fishery. 

This project’s estimates of yellowtail flounder RAMP score for the scallop fleet indicated that 

the estimated discard mortality rates ranged from 64 to 90%. The time series of discard mortality 

estimates and confidence intervals (excluding 3 months) showed a fairly stable estimate of 

discard mortality near 85%. Based on the RAMP results, and the possibility for additional 

sources of mortality not accounted for by the RAMP method, investigators agreed to assume a 

discard mortality of 90% for the southern New England/Mid-Atlantic yellowtail flounder stock 

assessment. 

Investigators also tested reflex actions on 586 winter flounder. The mean RAMP score was 0.57, 

which correlated to a discard mortality estimate of 36%, with lower and upper confidence 

intervals of 16% and 60%. This estimate of discard mortality for winter flounder in the scallop 

fishery (36%) is lower than the currently assumed 50% for all commercial fishing. The accepted 

value of 50% fell within the investigators’ confidence interval range, indicating that the 50% 

used in the stock assessments may not be an overestimate for the scallop fleet. Although the 

basis of the 50% discard mortality assumption is not well documented, it appears to be an 

approximation based on an estimate of discard mortality of yellowtail flounder off Canada. This 

project shows that the currently accepted value used in the winter flounder stock assessments 

may be an accurate representation of the true discard mortality rate for the scallop industry.

3.1.1.3 Evaluation of Summer Flounder Discard Mortality in the Bottom Trawl Fishery, Part II: 

A Study of the Offshore Winter Fishery

This Cooperative Research Program project, completed in 2012, was designed to determine 

summer flounder discard mortality relative to tow time, fish size, and the amount of time fish 

were on the deck of the vessel. Investigators conducted tows of 1, 2, and 3 hours in duration. 

Investigators culled fish both immediately (from 0 to 10 minutes on deck) and after being held 

on deck longer (25 to 35 minutes on deck). As soon as the fish arrived at the dock, investigators 

transferred live fish to a shore-side holding system and monitored them for mortality over a 21-

day period. Discard mortality rates were calculated based on the live/dead fraction of fish sorted 

on deck as well as the mortality rate of the live fish held in the holding system over the 21-day 

monitoring period. The main driving factor in all analyses of live/dead fraction on deck was cull 

time. The fraction live is clearly impacted by the time it takes to cull the fish. At and beyond the 

35 to 50 minute interval, fish begin to die off rapidly, no matter the tow time or catch weight. 

Jumbo-sized fish survived the best during the extended monitoring period, while small fish 

survived the worst. The on-deck original condition of fish was significant for mortality over 21 

days. Ambient on-deck air temperature at time of capture significantly impacted mortality 

during the extended monitoring period. Warmer on-deck air temperatures were associated with 

better survival. Overall median discard mortality was calculated to be 97.65%—much higher 

than the current assumed rate of 80% used in the stock assessment. Overall mean discard 

mortality was 80.4% and was nearly identical to the value assumed in recent summer flounder 
6

assessments. The discard mortality determined by this study should be considered a minimum 

mortality rate. 

3.1.1.4 Summer Flounder Discard Mortality in the Inshore Bottom Trawl Fishery

This Cooperative Research Program project, completed in 2011, was designed to evaluate actual 

trawl discard mortality of summer flounder (Paralichthys dentatus) within a research design for 

comparison to the assumed discard mortality rate currently used in the stock assessment. The 

study goal was to determine discard mortality relative to tow time, total catch, fish size, and the 

amount of time that fish were on deck. Initially, investigators conducted 10 scientific fishing 

trips consisting of tows of 1, 2, and 3 hours in duration. Investigators culled fish at consistent 

time intervals into live and dead on deck. Additionally, a sub-sample of live fish from the 

immediate cull and the delayed cull were held in an on-board live system and then transferred to 

an extended mortality monitoring net pen system. 

The overall summed discard mortality as determined by this project had a mean of 64.6% and a 

median of 78.7%. The mean discard mortality in the 1-hour tows was 58%, in the 2-hour tows 

61%, and in the 3-hour tows 77%. When comparing the parameter values of tow time, cull time,

and total catch as determined by this study, it is apparent that shorter tows, faster culling, and 

improved handling practices, while reducing per-tow total catch, can reduce summer flounder 

discard mortality. 

3.1.1.5 The Design, Development, and Field Testing of an Innovative Circular Net Pen to be 

Used to Assess Bycatch Mortality of Atlantic Cod at Sea

This Cooperative Research Program project, completed in 2010, involved the design and testing 

of an open-net system to study discard mortality at sea. The net pen was tested for a 24-hour 

period in September 2007. During this period, the net was deployed and retrieved 15 minutes 

later and then re-deployed for 24 hours before final retrieval. The pen was redeployed for 30 

hours in April 2008. During this experiment, 40 trawl-caught cod were placed in the net. A 

video camera was inserted into the pen, and cod were actively seen swimming within the net. 

Moreover, it appeared that individual cod were using the net at different depths to recover from 

the trawling process. During the deployment times, the structural integrity of the net was 

maintained, even when the sea wave-height increased to 2–4 feet for an extended period of time 

and with the tethering vessel anchored to the sea floor. 

Based on the success of the net design and the ability for cod to use the net to recover from the 

trawling process, the investigators concluded that the net can be deployed for any length of time 

under the same sea conditions to study discard mortality in a variety of fish species.

3.1.1.6 Discard Mortality in the Summer Flounder Fishery: A New Approach to Evaluation

This Cooperative Research Program project, completed in 2008, was designed to determine the 

discard mortality, including latent mortality, for summer flounder in the otter trawl fishery in the 

Mid-Atlantic Bight. At the time of this study, scientists assumed 80% summer flounder discard 

mortality from the commercial fishery. The investigators tested the effectiveness of motion-
7

sensitive tags in determining discard mortality in the laboratory, estuary, and ocean. The 

investigators found that motion-sensitive tags could provide another means for interpreting

mortality in tagged discards. Vertical movement has also shown to be potentially useful when 

determining mortality of a fish using acoustic telemetry over both field studies in 2009 and 2010. 

To test the assumption that it is possible to distinguish between live and dead tagged fish using 

telemetry, the investigators tracked fish in a preliminary effort in an estuary and evaluated their 

behavior in the laboratory. 

These studies showed that dead summer flounder (carcasses) can move substantial distances, and 

did so in synchrony with tidal currents. Live fish were much less mobile and more directed in 

their movements. In order to determine the mortality of these discarded fish, both live and dead 

summer flounder were tagged and released in a fixed hydrophone array on September 15, 2009,

at a location off Brigantine, New Jersey. Initial results from commercial fishery–length tows 

showed most fish in a poor to intermediate health condition. The initial on-deck mortality was 

32.7%. Mobile tracking efforts were able to re-detect both initially live and dead fish during 

tracking, and within the array for approximately 24 hours before a northeast storm event. Fish of 

poor initial health re-detected after the storm were found in a relatively concentrated area about 8 

km southwest of the release site, while live fish exited the array as they moved offshore as 

typical of the fall migration. These movement patterns provide a latent mortality estimate of 

50%. The final discard mortality estimate, combining on-deck mortality and latent mortality, is 

82.7%. 

3.1.1.7 Industry-Science Partnership Investigating the Short-Term and Long-Term Discard 

Mortality of Spiny Dogfish Using Hook Gear in Gulf of Maine Waters

This Cooperative Research Program project, completed in 2007, was a partnership between the 

Gulf of Maine Research Institute (GMRI), the Cape Cod Commercial Hook Fishermen’s 

Association (CCCHFA), and commercial fishermen. The primary research objective was to 

investigate the short-term discard mortality rate of dogfish from different commercial hook 

gears. Survivability was investigated through caging studies. A total of 2,418 dogfish were 

sampled between the two regions; of these 682 were caged by GMRI (45% males and 55% 

females) and 1,234 were caged by CCCHFA (27% males and 73% females). An overall regional 

difference in short-term discard mortality was observed; GMRI recorded significantly lower total 

mortality (7%) than CCCHFA (22%). Regional, averaged findings showed a sex effect with 

males demonstrating higher mortality (26%) than females (14%). The largest dogfish of each sex 

demonstrated greater resilience to mortality. Gear effects were found, with highest mortality 

resulting from longline gear (22%), while the different hand gear–related mortality ranged from 

8–17%. The relationship between hook removal treatment and hooking severity index was 

significant. Because this study’s long-term discard mortality assessments were aborted for

logistical reasons, these findings represent the range of likely short-term discard mortality from 

hook gears across the region.
8

3.1.1.8 Juvenile Bycatch and Survival Assessment of Spiny Dogfish (Squalus acanthias) in a 

Western Atlantic Trawl Fishery

This 2003 Saltonstall-Kennedy (S-K) Grant Program project, completed by the New England 

Aquarium Corporation in 2006, found that discard mortality in dogfish fell below 50% following 

trawl capture in the wild. The investigators concluded that, based on the relatively low 

percentage of dying animals following the 72-hour period and the acid-base recovery 

demonstrated by survivors, spiny dogfish are able to survive at a high percentage when faced 

with routine trawl-capture stress. Investigators suggested that additional work should address the 

effects of greater fluctuations in tow times, tow weights, seasonality, air and seawater 

temperatures, air exposure (in the lab and the field), capture modes (e.g., gillnetting), and 

physical and behavioral indices as primary study parameters. Investigators also felt the apparent 

influence of gender on dogfish mortality also required additional investigation under more 

controlled settings.

3.1.1.9 Increasing Survival of Juvenile Atlantic Cod (Gadus morhua) and Haddock 

(Melanogrammus aeglefinus) in the Northwest Atlantic Demersal Longline Fishery

This S-K Grant Program project, completed in 2004 by the New England Aquarium Corporation, 

was designed to build upon the selectivity work already conducted and investigate how different 

hauling strategies might affect wound size and juvenile groundfish survivability. Longline catch 

is usually removed from the hook by force: the fish is held in place with a gaff braced against 

two parallel steel cylinders placed vertically on the gunwale, allowing the hydraulic hauler to 

pull the hook through the fish’s flesh. This process can inflict severe injury to the fish. To 

minimize these injuries, an alternate protocol was investigated. A two-handed flip over the barb 

of circle hooks produced a single hole in the oral cavity of the fish. When this flip method was 

compared to the snub procedure, no difference in survival after 72 hours was observed in 

sublegal-sized cod bycatch. Biochemical data gathered on a similar subset of these fish suggested 

that the protocols chosen to judge survival may have added a level of stress that could have 

confounded the results. 

3.1.1.10 Increasing Juvenile Cod Bycatch Survival in a Northwest Atlantic Longline Fishery

This S-K Grant Program project, completed in 2004 by the New England Aquarium Corporation, 

was designed to (1) augment the survival data already collected on juvenile cod bycatch caught 

by demersal longlines, (2) quantify mitigated survival of juvenile cod bycatch when treated by 

immersion in solutions of potassium chloride, (3) quantify the degree of physiological stress 

experienced by juvenile cod bycatch through the analysis of biological parameters in the blood, 

and (4) continue to solicit advice from longline fishermen relative to increasing the survival of 

groundfish discards. Longline fishing practices often remove bycatch from the hook by force: the 

fish is held in place with a gaff braced against two parallel steel cylinders placed vertically on the 

gunwale, allowing the hydraulic winch to pull the hook through the fish’s flesh. This process can 

inflict severe injury to the fish and affect survival. In previous studies, fish dehooked by force 

were also found to have low serum levels of potassium ion. 
9

In this study, the importance of the potassium ion concentration in the blood was examined. 

Normal seawater enriched with granular potassium chloride was tested for its mitigating effect 

on survival. When the survival of snubbed sub-legal sized Atlantic cod treated with potassium 

ion was compared to untreated fish, no difference was found after 72 hours. Biochemical data 

gathered on a subset of similar fish were analogous to previous studies.

3.1.1.11 Selectivity and Survival of Atlantic Cod and Haddock in a Northwest Atlantic Longline 

Fishery

This S-K Grant Program project, completed in 1999 by the New England Aquarium Corporation, 

was designed to examine the selectivity of commercial hook gear to evaluate the claim that 

juvenile fish caught by hook have minimal stress and, consequently, better survival. Two studies 

were conducted. The first study compared the length frequencies of cod caught on 11/0 versus 

modified 15/0 circle hooks. The 15/0 circle hook was non-traditional because it was constructed 

of the same gauge wire as the 11/0 hook. This study found that the 15/0 circle hook retained the 

same number of legal cod yet caught few sub-legal cod. In the second study, juvenile cod were 

collected during experimental longline fishing operations during 1996 and 1997. Fish were 

removed from fishing gear either by a mechanical dehooking device (crucifier), or gently by 

hand. Survival rates were determined by placing the juvenile fish into large cages and returning 

them to the depth at which they were caught for a period of about 72 hours. The lowest survival 

figures were found for fish that were wounded by the crucifier.

The focus of the research in the second study was to assess the longline fishery and the rate of 

mortality of sub-legal catch after the fish were in the cages for 72 hours. The results showed high 

mortality associated with capture using the 11/0 circle hook when the cod had their jaws broken 

or torn after passing through the crucifer. Mortality increased when predation by herring gulls 

was considered.

3.1.2 Current Projects

3.1.2.1 Optimization of Gear Size and Post-Release Mortality Reduction in the New Jersey 

Summer Flounder Hook-and-Line Fishery

This 2013 Bycatch Reduction Engineering Program (BREP) project, to be carried out by 

Farleigh Dickenson University, is designed to quantitatively determine the optimal hook sizes for 

anglers to land legal summer flounder, reduce the number of sub‐legal flounder caught 

(discards), and reduce the incidence of deep hooking associated with catch and release. This 

technological research study has been designed to directly reduce the number of flounder 

discards and post‐release mortality through optimization of gear size for both the commercial 

and recreational hook and line fisheries. These “optimal” size(s) will result in fewer discards and 

increase stock biomass through reduction of stress and potential mortality. These data will then 

be used to recommend selective gear regulations to reduce future discard mortality.
10

3.1.2.2 Elucidating Post-Release Mortality and “Best Capture and Handling” Methods in 

Sublegal Atlantic Cod Discarded in Gulf of Maine Recreational Hook-and-Line Fisheries

This 2012 BREP grant project, being carried out by the New England Aquarium Corporation, is 

designed to estimate 30-day post-release mortality of Atlantic cod using ultrasonic telemetry. 

This project also is designed to determine and disseminate best angling and handling practices 

that minimize injury/stress and enhance survival in sub-legal (and barely legal) cod discarded in 

Gulf of Maine recreational hook and line fisheries. The work will first evaluate the condition of 

~400 cod immediately following capture by recreational angling during the summer of 2013. 

Prior to release, acoustic transmitters equipped with depth sensors will be affixed to a subsample 

of 150 individuals to detect any delayed fatalities for ~30 days post-release. Through pilot work, 

this project’s researchers have field-tested the application of this technology to estimate mortality 

in cod and have found a clear disparity in acoustically transmitted depth profiles between live 

and dead specimens monitored over a ~2-week period. 

These initial findings, coupled with the generally small-scale movements of juvenile cod, 

indicate that, with careful placement of an array of acoustic receivers, this technology can 

reliably estimate post-release mortality for this species and size class. By retrospectively 

evaluating the physical, biological, and other variables from the capture and handling process, 

this project’s researchers hope to establish a set of guidelines to reduce post-release mortality. 

3.1.2.3 Evaluating the Condition and Discard Mortality of Skates Following Capture and 

Handling in the Sea Scallop Dredge Fishery

This 2012 Atlantic Scallop Research Set-Aside project is designed to investigate the speciesspecific immediate and post-release mortality rates for little (Leucoraja erinacea), winter 

(Leucoraja ocellata), and barndoor (Dipturus laevis) skates. Mortality rates will be quantified 

using the combination of mortality predictors (i.e., condition and reflex impairment) and 72-hour 

mortality trials in an on-deck tank system (equipped with a chilling system to mimic bottom 

water temperatures). Condition index values will be based on visual assessment evaluating overt 

physical trauma on a scale from 1 to 3. Reflex impairment will be based on five reflexes scored 

on a present/absent scale (0 = reflex impairment; 1 = reflex exhibited) and then calculated into a 

vitality score as: 1 – (# of reflexes exhibited/total # of reflexes tested). In addition, this study 

will assess the effect of factors such as fishing conditions (e.g., season and depth) and practices 

(e.g., tow times, volume of catch, deck duration) on post-release mortality. 

Quantitative information gathered from this study on post-release mortality can be applied to 

overall discard morality estimates in the New England scallop dredge fishery, which in turn will 

strengthen the reliability of future management models. As of August 2013, 3,731 skates (little: 

2,292; winter: 1,184; barndoor: 255) had been sampled from five separate research trips (2012–

2013). Based on predictive condition and vitality (reflex-based) indexes, preliminary data 

suggest that a species-to-species difference exists in post-release mortality, such that barndoor 

skates are most vulnerable and winter skates are most resilient. 
11

3.1.2.4 Post-Release Survivability of Longline-Caught Large Coastal Sharks

This 2009 S-K Grant Program project, carried out by the University of Massachusetts, 

Dartmouth, was designed to increase the understanding of capture-related stress and the potential 

long-term effects on survival with a focus on sandbar and dusky sharks captured in the 

commercial demersal longline fishery. For each captured fish, blood and tissue samples would be 

gathered to quantify the capture-related physiological, biochemical, and molecular stress 

responses, with selected fish tagged to correlate stress parameters of a fish with its post-release 

movement patterns and long-term survival.

3.1.2.5 The Immediate and Short-Term Post-Release Mortality of Species in the Northwest 

Atlantic Skate Complex Captured by Gillnet and Otter Trawl

This 2008 S-K Grant Program project, carried out by the New England Aquarium Corporation, 

aimed to quantify the species-specific at-vessel and short-term discard mortality rates from trawl 

and gillnet capture for skates in the Northeast Skate Complex. The analyses were designed to 

consider not only the impacts of fishing conditions (e.g., season, depth, and seawater and air 

temperature), but also fishing practices (e.g., tow/soak times, sorting durations/deck times, and 

handling protocols (i.e., picking versus non-picking)). In addition to generating data of great 

interest to management of species in the complex, this study was designed to expand the limited 

body of field-oriented stress investigation in elasmobranch fish.

3.2 Southeast 

3.2.1 Past Projects

3.2.1.1 Fine-Scale Behavior and Mortality in Post-Release Carcharhinid Sharks in the Florida 

Recreational Shark Fishery

This 2011 Cooperative Research Program project, carried out by Mote Marine Laboratory, was 

designed to quantify post-release mortality and behavioral effects of capture on blacktip sharks 

(Carcharhinus limbatus) caught in the Florida recreational shark fishery, and empirically test the 

differential impacts of circle versus J hooks on physiology and mortality. Investigators recorded 

capture measures (e.g., fight time, animal condition, etc.); tested blood stress indicators; and 

applied acceleration data loggers (ADLs) to measure fine-scale swimming behavior of blacktip 

sharks (N=31) caught by recreational fishermen. Mortalities (N=3, 9.7%) all took place within 

2 hours (h) after release and were indicated by static depth data and the cessation of tail beat

activity. Surviving sharks were monitored for 7 to 72 h (30 ± 22 h, mean ± SD) using ADLs. 

ADL data were used to calculate 58 metrics of fine-scale swimming behavior and evaluate their 

ability to indicate a recovery period in surviving sharks. Investigators used nonlinear mixed 

modeling to fit a four-parameter logistic function to these metrics. Of the 58 metrics, 18 

displayed a significant logistic relationship with time after release, with mean recovery periods 

from each metric ranging from 7.4 to 14.4 h after release (9.9 ± 1.9 h, mean ± SD). 
12

Overall, results show the ability of accelerometers to provide definitive information on animal 

outcomes and the broad applicability of these data to the study of post-release mortality and 

recovery in coastal sharks. Further work is needed to determine relationships between ADLbased metrics of recovery and blood biochemistry. This study did not address differences in 

handling practices between fishermen, such as the practice of removing the shark from the water 

to remove the hook or take photographs before release. However, for sharks left in the water 

throughout the handling process, study findings indicate low mortality for blacktip sharks caught 

in the recreational fishery and little effect of hook type on mortality rate or other parameters.

3.2.1.2 Post-Release Survival and Habitat Utilization of Juvenile Swordfish in the Florida Straits 

Recreational Fishery

This 2010 Cooperative Research Program Project, carried out by Nova Southeastern University, 

was designed to investigate two main topics: (1) the post-release survival rates of juvenile 

swordfish after being released from the recreational rod and reel fishery and commercial 

swordfish buoy gear fishery in the Florida Straits, and (2) the habitat utilization of juvenile 

swordfish following release. High-resolution pop-up satellite archival tag technology was used 

to estimate the post-release survival of 16 individual juvenile swordfish captured with standard 

recreational or buoy fishing gear and techniques in the southeast Florida swordfish fishery. Five 

of the 14 reporting tags showed mortality within 48 hours, for a release mortality rate of 35.7%. 

However, no common thread could be found among the five mortalities. Results of the Release 

Mortality program indicated that if the true mortality rate was 35.7%, approximately 1,800 tags 

would need to be deployed to increase the precision of the mortality estimates to +/- 5% of the 

true value. 

3.2.1.3 Evaluating the Effect of Barotrauma on Regulatory Discards in the Red Snapper Fishery 

using Advanced Acoustic Telemetry and Hyperbaric Experimentation

This 2010 Marine Fisheries Initiative (MARFIN) project, carried out by Texas A&M 

University—Corpus Christi, was designed to: (1) examine the long term impacts of barotrauma 

on red snapper discards using state-of-the-art ultrasonic telemetry after single and multiple 

recompression events, determining the validity of mark and recapture experiments in this fishery; 

and (2) identify the impacts that multiple barotrauma events have on the biology of red snapper 

under experimental laboratory settings using hyperbaric chambers. Specifically, this study was 

designed to (1) compare behavior and mortality of red snapper experiencing barotrauma using 

acoustic telemetry; (2) determine the relationship between previous estimates of discard 

mortality and mortality rates derived from internally implanted acoustic telemetry tags; and (3) 

examine the impact of multiple decompression events on red snapper growth, mortality, 

reproductive potential, and behavior under laboratory settings. 

3.2.1.4 Collaborative Research to Quantify and Reduce Bycatch Mortality of Blacknose Sharks 

in Shrimp Trawls

During this 2010 Cooperative Research Program project, University of Georgia Marine 

Extension Service staff worked with Georgia Department of Natural Resources biologists and 

commercial shrimpers to (1) understand commercial trawler interactions with blacknose sharks 
13

using trained observers to collect data and (2) quantify the shark bycatch reduction potential of 

the newly certified Big Boy turtle excluder device (TED) with narrow 2” bar spacing compared 

to a Double Cover TED with standard 3.5” bar spacing (the industry standard), with fisheyes 

removed from both nets. This project was designed to involve commercial shrimpers throughout 

all stages of the project. Results indicate that the Big Boy TED with 2” bar spacing significantly 

reduces shark bycatch without affecting shrimp retention. 

Data collected on commercial shrimp trawlers indicate that blacknose sharks do not represent a 

large component of total shark bycatch in Georgia. The most common shark species captured 

were Atlantic sharpnose, bonnetheads, and scalloped hammerheads. On the commercial vessel 

with the most complete observer coverage (F/V Sundown, with 294 observed 2-hour trawls over 

a period of 2 years), the encounter rate for blacknose sharks was 11.9%. This vessel was fishing 

four nets simultaneously. The catch per unit effort was less than one blacknose shark per day 

(0.8). A total of 92 blacknose sharks were captured by this vessel in 2012–2013. Blacknose 

sharks were encountered primarily in May and June when Georgia state waters are newly opened 

to commercial shrimping (0-3 miles); this is the time of year when blacknose occur near shore 

within the small size range that makes them vulnerable to trawl gear. 

3.2.1.5 Release Mortality of Gulf of Mexico Greater Amberjack from Commercial and 

Recreational Hand-Line Fisheries

This 2009 MARFIN project, carried out by the University of Florida, yielded several results. 

During this study, greater amberjack were discovered to have a “self-venting” mechanism 

unheard of in other physoclistous reef fishes. Venting does appear to assist greater amberjack 

when captured from deeper depths, usually deeper than 150 ft. Amberjack may be good 

candidates for venting because their swim bladders are tough and are buttressed by their ribs.

Overall, greater amberjack seem to survive capture and release much more easily than most other 

reef fishes. This may be because they are really semi-pelagic, and although they aggregate 

around structure, similar to reef fish, they also use the water column from the surface to great 

depths in a matter of minutes. This project indicated a high acute survival rate for greater 

amberjack for some handline fisheries, and initially depth of capture and decompression do not 

appear to be major factors in release or discard mortality. 

There are several possible explanations as to why acute barotrauma may not be high in 

amberjack. First, greater amberjack cannot be brought up as quickly to the surface as other fish, 

such as gag grouper or red snapper, because they energetically resist being brought up (hence 

their attribute of being great fighting fish). This may give the fish time to re-absorb oxygen from 

the swim bladder into the blood stream. Second, the membrane of the swim bladder is very thick 

in amberjack and is internally baffled, which would provide greater structural support. Finally, 

the self-venting mechanism is the main contributor to off-gassing of the excess gases expanding 

in the swim bladder. 
14

3.2.1.6 Characterization of Recreational Discard Composition and Mortality Rates for Gray 

Snapper and Other Estuarine-Dependent Reef Fishes within a Gulf Coast Estuary and Nearshore 

Florida Waters

This 2009 Cooperative Research Program project, carried out by the Florida Fish and Wildlife 

Conservation Commission, was designed to characterize recreational discard mortality rates for 

gray snapper captured within a gulf coast estuary and nearshore Florida waters and to develop 

sampling methods to more effectively collect detailed recreational catch, effort, and disposition 

data for gray snapper and other estuarine-dependent reef fishes. Discard mortality experiments 

indicated that mortality rates for gray snapper (Lutjanus griseus) in the lower Tampa Bay estuary 

(inshore) and neighboring Gulf of Mexico waters (nearshore; ≤ 20 nm from shore) were 

relatively low. A total of 247 gray snapper were caught over nine inshore and nearshore 

experiments; 17 of these fish died within 48 hours, for an overall mortality rate of 6.9%. The 

inshore mortality rate (1.4%) was lower than the nearshore mortality rate (14.4%) and was 

probably related to depth of capture. 

Hook position and increasing depth significantly influenced the probability of mortality. Gag

(Mycteroperca microlepis) were also retained during inshore mortality experiments; a total of 

111 gag were caught over four experiments, and eight of these fish died within 48 hours leading 

to an overall mortality rate of 7.2%. Hook position and decreasing size of the individual 

significantly influenced the probability of gag mortality. For both species, individuals hooked in 

the lip were most likely to survive the catch and release event, while gray snapper hooked in the 

esophagus or gag hooked in the gills were the least likely to survive. The short-term mortality 

rates calculated during this study are relatively low and are conservative estimates due to 

responsible handling practices; these rates may increase depending on depth captured, fish size, 

and the position of the hook in each fish. 

Directed hook and line sampling was conducted each month in inshore and nearshore Tampa 

Bay waters from July 2009 to July 2011. The use of circle hooks during our study resulted in a 

high percentage of reef fish being hooked in shallow anatomical locations such as the lip or 

inside the mouth (94.6%). A large proportion (95.7%) of all fish caught was reported to be 

released in good condition.

3.2.1.7 Survival of Discarded Reef Fish Species in the Recreational Fishery Using At-Sea 

Observer Surveys and Mark-Recapture Methods off the Florida Coast in the Gulf of Mexico

This 2009 Cooperative Research Program project, carried out by the Florida Fish and Wildlife 

Conservation Commission, was designed to evaluate survival of discarded reef fish from 

recreational for-hire headboats operating in the Gulf of Mexico. Based on behavioral 

observations at the surface immediately upon release, the majority of reef fish discarded in this 

study were able to break the surface and swim out of sight immediately (good condition) or 

relatively quickly after some minor disorientation (fair condition). More than 90% of discarded 

gag and red grouper and more than 80% of scamp were released in good condition. Compared to 

grouper species, a higher percentage of red snapper and vermilion snapper were visibly 

struggling at the surface and were often unable to submerge (poor condition), or were 

unresponsive and presumed dead (dead condition) upon release. Red snapper caught on circle 
15

hooks are 1.3 times more likely to be lip-hooked when caught on circle hooks compared to other 

hook types. 

The results from this study indicate several key differences between regions and among trip 

types should be accounted for when applying discard mortality rates to the reef fish fishery as a 

whole. Regional differences in accessibility to deep water and the relative proportion of trips 

that take place at varied depths within each region should be considered when applying depthdependent discard mortality rates. The numbers of recaptured fish at the time this report was 

written were insufficient to evaluate relative survival of fish caught and released under variable 

conditions in the recreational hook-and-line fishery. Reports of recaptured fish were low during 

the peak fishing season in 2010 due to the large areal fishing closures in the Gulf of Mexico 

following the Deepwater Horizon incident.

3.2.1.8 Minimizing Discards in the Gulf of Mexico Recreational Red Snapper Fishery: Hook 

Selectivity and the Efficacy of a First Fish Rule

This 2009 Cooperative Research Program project, carried out by the University of West Florida, 

was designed to examine several aspects of the northern Gulf of Mexico charterboat reef fish 

fishery to identify possible measures to mitigate discarding. Two extensive hook selectivity 

experiments were conducted in which anglers fished with a range of circle hook sizes onboard 

boats to test the effect of circle hook size on reef fish catch rates and selectivity. Reef sites were 

video sampled with a micro remotely operated vehicle equipped with a red laser scaler to 

estimate fish community and size structure prior to fishing reefs with different sized circle hooks. 

In the first experiment (n = 69), three circle hook sizes (9/0, 12/0, and 15/0) were fished, while 

five hook sizes (adding 2/0 and 4/0 hooks) were examined in the second experiment (n = 52). 

Red snapper constituted 25.3 and 22.9% of fishery species individuals observed among reefs 

during experiments 1 and 2, respectively. However, red snapper constituted no less than 61% and 

as much as 89% of fish captured while fishing. Increasing hook size decreased catch rates 

among all fishes captured, and decreased estimated catchability for red snapper. 

Results indicate that increasing hook size does affect catchability and selectivity in the reef fish 

fishery, but potential conservation benefits of using larger hooks may be confounded by 

unintended effects given that the largest hooks used in the current study caught red snapper 

almost exclusively. Results from scientific observation of normal charterboat fishing activities 

during open and closed red snapper seasons indicate charterboat captains are able to avoid red 

snapper somewhat during closed seasons as the mean proportion of red snapper captured during 

closed season observer trips was 23.8% versus 88.6% during open seasons. Furthermore, mean 

number of red snapper discards was actually higher for open (19.8) versus closed (14.9) season 

trips. Observer data were collected on relatively few (n = 25) trips aboard only four Gulf of 

Mexico charterboats.
16

3.2.1.9 Discard Mortality of Red Snapper in the Northeastern Gulf of Mexico Recreational 

Fishery

This 2009 MARFIN project, carried out by Patzig Marine Services, Inc., was designed to

examine discard mortality in the recreational red snapper industry. Red snapper were caught 

using either a standard recreational 3-to-5 hook rig using #8/0 circle hooks with dead bait or a 1-

hook rig using #9 circle hooks with live bait. All fish were vented with a venting tool made from 

a 10 mL syringe with a 14 gauge hypodermic needle. Fish were initially held in a recirculating 

live well until 20 to 25 individuals were caught. While fish were in the live well, they were 

visually monitored for stress by the NMFS Field Biologist and the principal investigator. When 

20 to 25 fish were caught, they were dipped out of the live well with a net and placed in a 6-foot 

diameter by 12-foot length wire mesh holding pen deployed into the water. After a holding 

period of 2 to 3 hours, the cage was lifted to the surface and all dead fish removed and annotated 

by tag number as non-survivors. There were 1,486 red snapper sampled. An additional 11 fish 

were recaptures. Overall 204 (14%) of the total samples died in the cage and/or live well, and 

1,282 (86%) survived to be released. 

3.2.1.10 A Directed Study of the Recreational Red Snapper Fisheries in the Gulf of Mexico 

along the West Florida Shelf

This 2009 Cooperative Research Program project, carried out by the Florida Fish and Wildlife 

Conservation Commission, found several key differences between regions and among trip 

types that should be accounted for when applying discard mortality rates to the reef fish fishery 

as a whole. First, regional differences in accessibility to deep water and the relative proportion 

of trips that take place at varied depths within each region should be considered when applying 

depth-dependent discard mortality rates. Exposure studies indicate that depth-dependent 

mortality for various reef fishes is low at shallow depths (<20m), increases to between 20% -

40% (depending on the species) at capture depths below a threshold between 30 or 40 meters, 

and mortality exponentially increases beyond the threshold at deeper depths. Consequently, 

understanding where and how recreational fisheries operate is critical when assessing catch-andrelease mortality. If this information is known, depth-dependent discard mortality relationships 

described by studies such as this one may be applied to other recreational hook-and-line fisheries 

for which it is less feasible to measure discard mortality directly, such as the private boat fishery. 

Variable effects of circle hooks and release methods (venting versus releasing without venting) 

also demonstrate the importance of monitoring within a fishery, both for quantifying discard 

mortalities and changes in fishing behaviors in response to regulations. For species with high 

discard rates, even low percentage reductions for discards that suffer mortality can have a 

significant impact on total fishery removals. Except for a brief closure February-March during 

the years of this study, red grouper was open to recreational harvest year-round, and it is clear 

from the size distribution of discards that the majority of grouper that are vulnerable to capture 

are under the legal harvest size. Even small percentage reductions in mortality attributed to the 

use of circle hooks for species with high rates of discarding, such as red grouper, can equate to 

substantial reductions in total removals attributed to the fishery. Red snapper were discarded

during the years of this study at lower rates compared to red grouper, but discards are still a 

substantial portion of total removals, and this species appears to be more vulnerable to hook 
17

injuries. Therefore, this species may particularly benefit from larger reductions in discard 

mortality through the use of circle hooks. Results from this study also indicate that fish that can 

re-submerge on their own have a higher rate of survival if they are not vented, but may benefit 

from venting when it helps them re-submerge.

3.2.1.11 Determination of Alternate Fishing Practices to Reduce Mortality of Prohibited Dusky 

Shark in Commercial Longline Fisheries

This study aimed to understand the effects of longline hooking on dusky shark mortality, and to 

observe the effects of certain factors on longline mortality. Although other studies have found a 

correlation between soak time and mortality in dusky sharks (Romine et al 2009), this study was 

able to correlate time-on-hook and mortality in dusky sharks. This study showed that median 

mortality is reached after 6 hours on the hook, and 90% mortality is reached after 15 hours. This 

median mortality is shorter than that when soak time is used as a measure of mortality rates, 

when median mortality occurs after 13 hours. 

This study found that consideration of time-on-hook and mortality can lead to more effective 

management measures related to the restriction of soak time. Overall, this study’s results 

supported predictions that dusky sharks experience high levels of hooking mortality, and that 

time-on-hook is a more accurate measurement of mortality associated with bottom longline gear 

than soak time. This study also found water temperature to be an insignificant factor affecting 

mortality.

3.2.1.12 Examining the Efficiency of Modified Circle Hooks in Reducing the Bycatch of 

Undersized Lutjanid and Serranid Fishes

To examine the potential for reduction of post-release mortality of undersized snapper and 

groupers caught with circle hooks, the NMFS Southeast Fisheries Science Center tested the 

efficacy of modified circle hooks in further reducing incidences of gut hooking. The modified 

circle hook, or AP circle hook, incorporates a 40-mm wire extension (also referred to as an 

appendage) from the hook’s eye, thereby increasing the diameter of the hook while negligibly 

affecting its effective size and weight. As of the end of 2011, 1,286 fishes had been captured, 

representing 21 genera and at least 27 species. Black sea bass, red snapper, and vermilion 

snapper dominated the catch, constituting 48.5, 24.0, and 9.5% of landings, respectively. There 

was no evidence of size-related selectivity or reduced efficiency (50.04% captured with circle 

hooks and 49.96% captured on AP circle hooks for all fishes collected) between the two hook 

types, regardless of species. Of the captured fishes, 97% were lip hooked regardless of hook 

type. When comparing hooking location by hook type, over 95% of all fishes captured were 

hooked in the jaw; however, 98.75% of fishes captured on appendaged hooks were hooked in the 

jaw, compared to 95.79% of fishes captured on circle hooks. Of the 17 fishes hooked in the 

throat or alimentary canal, only one of these occurrences was on an appendaged hook.
18

3.2.1.13 Reducing Discard Mortality in Red Snapper Recreational Fisheries using Descender 

Hooks and Rapid Recompression

This 2007 Cooperative Research Program project, carried out by Texas Tech University, 

compared the survival of fish released at the surface, both vented and unvented, with fish 

released at the bottom using a device invented by a fisherman—the Shelton Fish Descender 

(SFD hook). To test the hook, investigators used two types of mark and recapture methods: 

passive tags returned by fishermen (with tag returns as a proxy for relative survival), and 

acoustic tags that recorded acceleration and depth of the fish for at least 4 days after release. 

Overall survival was substantially lower under warm, stratified water conditions (summer) than 

cooler, mixed water conditions (spring/fall/winter). With both methods, investigators found no 

significant differences in relative survival rates by release method (treatment), season, or fish 

condition at release within years or overall years combined, although depth, year, fish length, and 

the interaction of year and fish length were all significant. Results were confounded by changes 

in red snapper management that shortened the fishing season from 6 months to 6–8 weeks, thus 

reducing the likelihood of tag recapture, and by significant increases in the sizes of fish from an 

average of ~340 mm in 2007 to 579 mm in 2011. 

Trends in tag returns indicated that unvented surface-released fish had higher relative survival 

under mixed water conditions, while either vented or unvented surface-released fish had higher 

relative survival under summer water conditions. These results were supported by the acoustic 

tag study, which also showed higher survival in unvented surface-released fish in winter and 

vented surface-released fish in summer. The only condition under which bottom-released fish 

showed improved survival over surface-release methods was when dolphin predators were avidly 

foraging on discarded fish, although predation may have been underestimated for bottomreleased fish. These results suggest that different release methods may be appropriate under 

different temperature and predator conditions to increase survival of released fish, although more 

research is needed.

3.2.1.14 Size and Age Structure and Catch and Release Mortality Estimates of Sub-Adult and 

Adult Red Drum in the Tampa Bay Estuary and Nearshore Gulf of Mexico Waters

This 2005 MARFIN project, carried out by the Florida Fish and Wildlife Conservation 

Commission, was designed to, among other things, determine the catch-and-release mortality and 

the sizes of released red drum captured in Tampa Bay. A total of 251 red drum were collected 

during nine different experiments, of which 14 individuals died within 48 hours for a mortality 

rate of 5.6%. Logistic regression analyses indicated that both temperature and hook position 

significantly influenced the probability of mortality, with mortality rates increasing significantly 

with higher temperatures and among individuals hooked in the throat. No direct evidence of 

higher mortality using J-hooks was detected, although a higher proportion of individuals caught 

using J-hooks experienced deeper hooking. Results from this study will not significantly alter 

results from the existing Florida red drum assessment (as of 2009), which assumed a 5% postrelease mortality rate.
19

3.2.1.15 Cooperative Hook and Line Discard Mortality Study of Vermilion Snapper in the 

Northeastern Gulf of Mexico Commercial Fishery

This 2005 Cooperative Research Program project, carried out by Patzig Marine Services, was 

designed to collect information pertaining to the discard mortality of vermilion snapper using 

three common methods of air bladder puncture when fish were brought up rapidly from depth. 

Fish were tagged, measured, and placed in a holding pen, where underwater cameras filmed

them for a minimum of 3 hours. Investigators released survivors back into the Gulf. Predation 

of discarded fish was also documented. A total of 30 trips were made, providing 1,912 samples. 

Overall, 34% of the samples captured died in the cage and 66% survived to be released. Results 

showed that survival of vermilion snappers was greater when swim bladders are punctured with a 

hypodermic needle and that no venting was only slightly worse (1%) than using a fillet knife for 

venting. The investigator found that predation from porpoises, sharks, and other species was a 

significant factor in the mortality of discarded vermilion snappers. Through observations and 

some photographic evidence, the added effects of predation by sharks, porpoises, wahoo, king 

mackerel, and greater amberjack on discard mortality may be far greater than shown by this 

study’s recorded data.

3.2.1.16 The Capture Depth, Time, and Hooked Survival Rate for Bottom Longline-Caught 

Large Coastal Sharks

This 2005 Cooperative Research Program project, carried out by the University of Florida, used 

bottom longline gear, hook timers, and time depth recorders to collect data pertaining to the

relationship between soak time (the time longline gear is actively fishing) and capture depth on 

fishing mortality and catch per unit effort (CPUE) of individual shark species and shark species 

aggregates. Analyses showed that the majority (93.4%) of animals were caught while the 

longline was fishing on the bottom, two-thirds of the tripped timers had animals attached to the 

hook, and the majority of sharks were caught within the first 6 hours of a longline set. The catch 

consisted primarily of nurse (Ginglymostoma cirratum) (25.7% shark catch and 23.8% total 

catch), sandbar (22.4% shark catch and 20.7% total catch), blacktip (14.1% shark catch and 13% 

total catch) and Atlantic sharpnose (Rhizoprionodon terraenovae) (10.5% shark catch and 9.7% 

total catch) sharks. The bycatch species most commonly encountered were red grouper 

(Ephinephelus morio) (44.3% bycatch catch and 3.3% total catch). The mortality rates for the 

Atlantic sharpnose (100%) and nurse (0%) sharks were not dependent on the amount of time

spent on a hook. The sandbar shark mortality rate increased when time on hook increased, and 

the blacktip shark suffered its highest mortality after being on a hook for 4 hours or longer. Data 

analysis suggested that the majority of shark species bit the hook within the first 6 hours of the 

set. Mortality rates for several species of shark increased with the amount of time animals were 

hooked on the longline, and the majority of shark species were caught in water deeper than 100 

ft. 

3.2.1.17 Decompression and Delayed Mortality: Effects of Barotrauma on Red Snapper 

(Lutjanus campechanus)

This 2004 MARFIN project, carried out by Texas Tech University, was designed to (1) evaluate 

the effects of barotrauma in a controlled setting using a hyperbaric chamber to simulate capture 
20

from a variety of depths, (2) assess the effects of barotrauma on internal organs and establish 

correlations between tissue damage and release mortality, (3) test the visual acuity of red snapper 

and relate any changes in vision caused by decompression to survival, and (4) create a condition 

index that would allow observers to easily associate external signs of stress with delayed 

mortality. 

The investigators demonstrated that as the level of the stressors applied increased, the number of 

barotraumas experienced increased, reflex response capabilities decreased, circulating plasma 

cortisol increased, and swimming performance decreased. These observations suggested that the 

stress associated with rapid thermal change and decompression causes a significant decline in the 

ability of red snapper to recognize, react, and evade potential threats upon release.

3.2.1.18 Estimates of Catch-and-Release Mortality for Red Drum, Sciaenops ocellatus, in the 

Recreational Fishery of South Carolina

This 2003 Cooperative Research Program project, carried out by the South Carolina Department 

of Natural Resources, employed the most popular hook (J-hooks, non-offset circle hooks, and 

offset circle hooks) and natural bait types in two fishery-independent hooking studies 

representing the major targets (sub-adults and adults) of the South Carolina red drum fishery. 

Findings were compared to a fishery-dependent logbook study using fishing guides as well as a 

long-term dataset for adult red drum maintained by South Carolina Department of Natural 

Resources. Fishing in shallow habitats revealed that the smallest proportion of sub-adult red 

drum died when fishing with non-offset circle hooks. The largest number of sub-adult red drum 

were deep hooked (gills or gut) when J-hooks were used. The largest proportion of sub-adult fish 

died as a result of being deep hooked on offset circle hooks. A bottom longline study for adult 

red drum found fewer fish died when caught on non-offset circle hooks than on J-hooks. The 

large hook study also indicated that long-term impacts of catch and release may exist for 

reproductively active adults. The investigators concluded that non-offset circle hooks of the 

appropriate size should be used to maintain the lowest level of catch and release mortality for 

both sub-adult and adult red drum fisheries.

3.2.1.19 Removing Gas from the Distended Swim Bladder of Reef Fish: Does It Really Increase 

Post-Release Survival?

This S-K Grant Program project, completed by the South Carolina Department of Natural 

Resources in 1999, was designed to determine whether puncturing the distended swim bladder of 

reef fish in the southeastern United States would increase post-release survival. The benefits of 

deflating reef fish swim bladders were investigated by capturing fish by hook and line, deflating 

203 fishes using a 16 gauge hypodermic needle, deflating 223 fishes with a 3 mm steel canula, 

and not deflating 227 fishes acting as control subjects. Benefit was measured by survival over the 

first 24 hours after release. This study found that black sea bass benefited significantly from 

deflation and that vermilion snapper also benefitted, but not to the same extent as black sea bass. 

Survival of fish deflated by the hypodermic needle and the 3 mm canula was approximately 

equal. The largest increase in survival was in black sea bass caught at 43–55 meter depth and 

deflated with the hypodermic needle. Control specimens exhibited a 61% survival rate while 
21

100% of the specimens deflated by needle survived. Therefore, study results indicated that

released black sea bass should be deflated.

3.2.2 Current Projects

3.2.2.1 Testing an Alternative Method for the Safe Release of Reef Fishes Caught on Hook-andLine Gear in the Recreational Fishery in the Gulf of Mexico

This 2013 BREP project, being carried out by the Florida Fish and Wildlife Conservation 

Commission, is designed to: (1) assess whether rapid recompression for reef fishes in the Gulf 

of Mexico is a viable alternative to surface release when fish require venting and/or when 

venting is deemed unnecessary, (2) determine an optimum depth range for recompression and 

reduced predation, and 3) quantify potential reductions in post‐release mortalities if new release 

methods are prescribed. Principal investigators will work cooperatively with the recreational 

for‐hire industry to assess the practical application of recompression in the recreational fishery. 

Experimental treatments will compare the current practice—where fish are vented at the 

discretion of anglers and released at the surface—to an alternative method where fish are 

returned rapidly to depth and recompressed without the need for venting. The primary species of 

interest are red snapper, gag, and red grouper. Experiments will be conducted from recreational 

for‐hire vessels in northern and central portions of the west coast of Florida from June through 

September—the period of highest stress and vulnerability for discarded reef fish. Experiments 

will be conducted in depths between 30 and 60 meters where recreational fishing takes place and 

barotrauma is a concern. Fish will be tagged and recapture rates among treatment groups will be 

compared to assess relative survival rates.

3.2.2.2 Evaluation of the Effects of Recreational Catch-and-Release Angling on the Survival of 

Gag Grouper (Mycteroperca microlepis)

This 2013 project, funded by MARFIN, is being carried out by the Florida Fish and Wildlife 

Conservation Commission. The project is designed to identify the effects of catch and release 

angling (i.e., regulatory discards) on the survival and behavior of gag grouper across a range of 

depths and to evaluate the effectiveness of gear and tactics used to return fish to depth. Acoustic 

telemetry will be used to assess survival of gag grouper after recreational angling and release, as 

well as the efficacy of strategies employed to reduce pressure-related fishing trauma. Gag 

grouper will be caught during all seasons of the year over a range of depths (5–50 m) using 

standard reef fish recreational fishing tactics. Fish will be fitted with pressure-sensitive acoustic 

tags so their position within the water column may be monitored after release. Fish will be 

evaluated for signs of barotrauma and then returned to depth via venting or, alternatively, 

through submersion using a weighted crate or dropline. 

Permanently deployed acoustic receivers will continuously monitor sites and record fish 

presence and position within the water column, quantifying immediate, short-term (days–weeks)

survival and fine-scale behavioral patterns after a catch and release event. Permanently deployed 

receivers allow for the collection of data over extended periods, and can provide information 

regarding long-term (months–years) survival, behavior patterns, and residence times of 

acoustically tagged gag grouper. Movement and behavioral data collected after fish release will 
22

not only allow for a realistic indication of acute fish survival after an angling event, but can also 

provide an evaluation of the effectiveness of traditional and alternative methods used to return 

fish to depth.

3.2.2.3 Discard Mortality of Carcharhinid Sharks in the Florida Commercial Shark Fishery

This 2013 Cooperative Research Program project is being carried out by Mote Marine 

Laboratory. The project is designed to quantify post-release mortality and behavioral aspects of 

capture on sandbar (Carcharhinus plumbeus) and blacktip sharks (C. limbatus) caught in the 

Florida commercial shark fishery. This work will be accomplished by working with Florida 

commercial shark fishermen to tag animals with acceleration data loggers (ADLs), which record 

animal movements and body posture at sub-second intervals and therefore provide highresolution information about mortality, swimming abnormalities, and recovery time. ADL data 

will be compared to capture indices and blood-based stress indicators and used with hook timers 

to quantify the effect of hooked time on physiology and post-release swimming behavior in these 

two species.

3.2.2.4 To Vent or Descend? Evaluating Seasonal Release Mortality of Gag and Red Grouper in 

Recreational Fisheries of the Eastern Gulf of Mexico

This 2012 project, funded by MARFIN, is being carried out by the University of Florida. The 

project is designed to compare the acute, short- and long-term release mortality of gag and red 

grouper (Epinephelus morio) caught in recreational hook and line fisheries in the eastern Gulf of 

Mexico that have been released either after venting or by using descenders during winter and 

summer. The investigators plan to determine seasonal (winter versus summer) acute and shortterm release mortality rates for gag and red grouper caught in recreational fisheries and released 

after venting or through use of a descender device, using both surface and underwater 

observations and short-term caging experiments. The investigators also plan to compare surface 

and underwater observations of released gag and red grouper for behavioral and motor deficits 

based on either being vented or returned to depth using a descender device. In addition, the 

investigators plan to model the effect of season as a potential factor contributing to release 

mortality in gag and red grouper through integration with other factors previously known to 

contribute to release mortality, such as capture depth and time on deck.

3.2.2.5 Examining Hook Selectivity in the Northern Gulf of Mexico Recreational Reef Fish 

Fishery

This 2012 Cooperative Research Program project is being carried out by the University of South 

Alabama. It is designed to collect fishery observer data onboard northern Gulf of Mexico 

charterboats and conduct offshore hook selectivity experiments in spring and summer 2013. 

Two observer trips were made in fall 2012, during which 93 reef fish were sampled. The size 

distribution for red snapper discards reflected the fact that the red snapper recreational season 

was closed. The mode of the age distribution of red snapper discards was 5 years, although a 

third of the discards were 3 years old or younger.
23

3.2.2.6 An Evaluation of the Effects of Catch and Release Angling on Survival and Behavior of 

Goliath Grouper (Epinephelus itajara)

This 2010 MARFIN project, carried out by the Florida Fish and Wildlife Conservation 

Commission, was designed to identify the effects of catch and release angling on the survival and 

behavior of goliath grouper across a range of depths and to provide information on the 

abundance, size distribution, and residency of goliath grouper at specific sites within a defined 

region of the central eastern Gulf of Mexico. The investigators plan to use acoustic telemetry to 

assess immediate effects of catch and release angling for this species via both manual and 

passive tracking of animal movements. Diver surveys at sampling sites directly following fish 

release will allow initial confirmation of fish survival and condition as well as a description of 

the abundance and size distribution of other goliath grouper present. Manual tracking 

immediately following fish tagging will provide information regarding short-term survival and

fine-scale movement patterns after a catch and release event. Long-term behavioral data will be 

collected via passive acoustic telemetry and will provide data regarding the long-term survival, 

behavior, and residence of fish at specific sites.

3.3 West Coast

3.3.1 Past Projects

3.3.1.1 The Effects of Decompression and the Efficacy of Recompression as a Bycatch Mortality 

Reduction Tool for Rockfish

This 2008 S-K Grant Program project, completed by Oregon State University, evaluated the 

efficacy of using recompression to reduce bycatch mortality in rockfish species. The 

investigators evaluated the response of six species of Pacific rockfish to forced decompression at 

the histological level (heart ventricle, rete mirabile, head kidney, liver, gill, and eye) and 

macroscopic level to determine if differences in the macroscopic barotrauma response between 

species also extended to tissues. In addition, they investigated whether “baseline” levels (i.e.,

shortly after capture) of plasma cortisol differed between species. Tissue injuries as a result of 

forced decompression included emphysema in the heart ventricle, emboli in the vessels of the 

rete mirabile, and emboli in the vessels of the head kidney. No injury was observed at the 

histologic level in the liver, gill or eye due to barotrauma. Baseline cortisol levels ranged 

between 0 to 54.1 ng/ml and showed no differences among species. The investigators also 

induced barotrauma in adult black rockfish (Sebastes melanops) from a simulated depth of 35 m, 

followed by recompression. Blood and selected tissues (eye, heart ventricle, head kidney, liver, 

rete mirabile, and gonad) were sampled at days 3, 15, and 31 post-barotrauma to evaluate the 

tissue-level response during recovery. No mortality from barotrauma occurred during the 

experiments. The majority of both treatment and control fish resumed feeding by day 31. The 

only macroscopic injuries observed in treatment fish were the presence of a ruptured 

swimbladder and/or a ruptured tunica externa (outer layer of swimbladder). Organ histology 

showed injury in the rete mirabile of 7% of treatment fish. Plasma analyses indicated no strong 

effects due to barotrauma, suggesting overall handling stress outweighed any effects from 

barotrauma.
24

3.3.1.2 Reducing Post-Release Mortality for Common Thresher Sharks Captured in the Southern 

California Recreational Fishery

The common thresher shark (Alopias vulpinus) is the focus of a popular southern California 

recreational fishery that typically captures individuals by hooking them in the caudal fin. This 

technique reduces the ability for forward locomotion and the capacity for ram ventilation. This 

multi-year BREP project used pop-up satellite archival tags (PSAT tags) to assess the postcapture survivorship of tail-hooked adult and sub-adult common thresher sharks using. 

Survivorship estimates were based on 19 common thresher sharks captured in southern 

California from 2007 to 2009 using recreational stand-up tackle. Five mortalities were observed 

over the course of the study, resulting in an overall post-release mortality estimate of 26% 

(Heberer et al 2010). All mortalities occurred in large individuals with fight times of > 85 min. 

The study indicated that large tail-hooked common thresher sharks with prolonged fight times 

exhibit a heightened stress response that may contribute to an increased mortality rate. These 

results suggest that for larger individuals, caudal-based capture methods used in the California 

recreational fishery may not be suitable for an effective catch and release–based strategy. 

Subsequent studies funded by NMFS identified several techniques that may result in higher 

survival rates for mouth-hooked individuals, including the use of non-offset circle hooks, dead 

drifting, drop-back troll techniques, and drifting with artificial lures.

3.3.1.3 Incidental Take and Post-Release Mortality of Blue Sharks in the U.S. West Coast Drift 

Gillnet and Longline Fisheries for Swordfish

The California drift gillnet (CADGN) fishery targets swordfish in the California Current. With 

the exception of ocean sunfish, blue sharks are caught in greater numbers than any other fish 

species taken in this fishery. Nearly all blue shark are discarded at sea due to lack of market 

value. A 2009 analysis of the 1990–2008 observer data revealed that 32% of blue sharks 

captured were released alive, and an additional 5% were discarded with their disposition 

unknown. The remaining 63% were discarded dead. In 2007, the NMFS Southwest Fisheries 

Science Center and Southwest Regional Office began deploying PSAT tags on sharks released 

from the CADGN fishery to assess survivorship in order to determine more accurate estimates of 

fishery mortality for use in a blue shark stock assessment. As a part of the study, a set of criteria 

was developed to document the condition of all live blue sharks released: released: good, fair, or 

poor. Prior to the 2011–2012 season, 12 blue sharks (100–200 cm fork length (FL), median 149 

cm) had been tagged by fishery observers. Three of the 12 sharks were released in good 

condition, while the remaining 9 were released in fair condition.

Satellite tag records suggest that all animals survived the acute effects of capture in the CADGN 

fishery. During the 2011–2012 season, fishery observers deployed three survivorship Pop-up 

Archival Transmitting (sPAT) tags—new, more economical tags that record daily minimum and 

maximum depths and temperatures and are programmed to pop off if the tag exceeds a certain 

depth or remains at a constant depth for several days. These tags are effective for determining 

the fate of tagged fish. Of the three sharks tagged (two females of 134 and 162 cm FL, and one 

161 cm FL male), two were in poor condition when released and one was considered in fair 
25

condition. Two of the three sharks died immediately and the third \ died after 8 days. These 

results, combined with the results from the prior years, suggest that sharks that are released in 

good condition are likely to survive, whereas those released in poor condition are likely to die.

Science Center scientists are compiling the data on the condition of all sharks released to more 

accurately apply the survivorship estimates to the discarded population.

3.3.1.4 Ability of Southern California Deepwater Rockfish to Survive Barotrauma Following insitu Recompression

This 2011–2012 BREP project examined the long-term survival rate of deep-water rockfish 

species captured from depths of 80 to 180 m and subsequently recompressed and released using 

a weighted cage or other commercially available recompression device. Rockfish survival and 

behavior were monitored for up to 4 months following release using newly developed 

accelerometer and pressure-sensitive acoustic transmitters that were attached to each fish upon 

capture. Fifty tags were deployed on five different species, and of the fish that remained within 

detection range, 92.9 percent survived in the short term (up to 2 days), with 76.7 percent 

surviving long-term. The two deep-dwelling depleted species tagged in this project, bocaccio 

(Sebastes paucispinis) and cowcod (S. levis), both showed high long-term survival following 

recompression and release (90.0% and 100% respectively). 

Several types of commercially available “recompression” or “descending” devices can be used 

by recreational and commercial fishermen to release rockfish bycatch. A long-term survival rate 

of over 75 percent suggests that these devices should be considered in future management 

decisions as options to reduce bycatch mortality. Further studies are now needed to test the 

relative feasibility of the use and the success of different device types in the various fisheries that 

encounter rockfishes as bycatch. 

This study showed that rockfish caught deeper than 125 m should be recompressed to a 

minimum depth of 40 to 45 m. Such details are crucial in developing the future technology and 

protocols needed to properly implement recompression practices on a large scale. The results of 

this work were used to inform long-term mortality estimates for all depths and aggregate 

mortality estimates in depths greater than 50 fathoms. These estimates along with data from 

other West Coast research efforts were used by the Groundfish Management Team of the Pacific 

Fishery Management Council to derive mortality rates reflecting the use of descending devices. 

3.3.1.5 Post-Release Mortality in the Central California Ocean Recreational Salmon Fisheries

Assessments for West Coast ocean recreational salmon fisheries assume a post-release mortality 

rate of 14%, except in the case of the Central California fisheries (Salmon Technical Team

2000). Beginning in the early 1990s, a light tackle method of fishing known as “California-style 

drift mooching” became popular in Central California. This method results in a much higher 

proportion of gut-hooked fish than the standard method of trolling, and thereby a significantly 

higher post-release mortality rate of sublegal-size fish. 

To assess the post-release mortality rate for these fisheries, the California Department of Fish 

and Wildlife, supported and assisted by the NMFS Southwest Regional Office and Southwest 
26

Fisheries Science Center, held 276 drift-mooch caught Chinook salmon at sea in large onboard 

holding tanks for 96 hours (Grover et al. 2002). The control-adjusted 4-day mortality rates were 

found to depend strongly on hook wound location, ranging from 4% for maxillary-hooked fish to 

85% for gut-hooked fish. These wound location–specific mortality rates were weighted by the 

distribution of hook wound locations for drift-mooch caught fish determined by fishery onboard 

observers to obtain an overall post-release mortality rate of 42% for drift-mooch caught and

released fish. For the fishery as a whole, a weighted average of the 14% troll-caught and 42% 

drift-mooch-caught rates is assessed based on the prevalence of these two methods in the fishery, 

which varies by area and month, but typically has yielded an overall post-release mortality rate 

for the Central California salmon fisheries in the range of 20 to 25%. 

Although the required use of barbless circle hooks for drift-mooch fishing beginning in the late 

1990s has reduced the post-release mortality rate in this fishery by reducing the fraction of guthooked fish, the mortality rate is still relatively high. If other modifications to the drift-mooch 

technique or angler education is successful in further reducing the fraction of gut-hooked fish, 

the overall post-release mortality rate for these fisheries could be readily reassessed using the 

methods outlined above.

3.3.1.6 A Device for Greatly Reducing Fishing Mortality for Protected Giant Seabass 

(Stereolepis gigas) and Jewfish (Epinephelus itajara)

This S-K Grant Program project, completed in 2002 by the Pfleger Institute of Environmental 

Research, addressed release mortality of California’s giant sea bass and Florida’s goliath grouper 

(formerly referred to as jewfish), which are both very large protected species that are incidentally 

caught by recreational and commercial hook and line anglers. When these fish are brought to the 

surface, the air in their swim bladders expands greatly, making the fish so buoyant that they

cannot swim back to the bottom when released. A release device was designed and manufactured 

to allow commercial and recreational anglers a means of safely releasing large bottom fish with 

swim bladders. A prototype was built from which changes were made before a final product was 

produced. The final product was tested in the field on giant seabass and goliath grouper. Fish 

captured and released with this device were shown to survive through the use of acoustic tagging 

and tracking. Twenty-five of these devices were manufactured for distribution to commercial and 

party boats that routinely encounter these large protected species.

3.3.2 Current Projects

3.3.2.1 Field Validation of the RAMP Approach for Determining Crab Bycatch Mortality

This 2012 BREP grant project, which was ongoing as of mid-2013, is designed to determine 

mortality rates for bycaught Dungeness crab (Cancer magister) in Oregon’s commercial and 

recreational crab pot fisheries and indirectly in commercial bottom trawling. (Only male crab 

over a set size may be retained in pot fisheries, and no crab may be retained by trawling.) These 

morality rates will be accomplished using a tag-return study and the Reflex Action Mortality 

Predictor (RAMP) approach, which relates reflex impairment of discarded crab to a probability 

of mortality. The combination of these two methods should allow for an evaluation of both 

immediate and longer-term mortality rates, and will allow for the identification of variables that 
27

can be adjusted to reduce these rates. Investigators tagged and released crab from October 2012 

to April 2014. The investigators will offer rewards for tag returns until August 2014. Fishermen 

have been and will continue to be encouraged to report recaptured crab through extensive 

outreach efforts. Data will be analyzed in the summer of 2014, and results will be submitted in a 

final report to BREP in October 2014 and then disseminated to the fishing community through 

flyers and a workshop.

3.3.2.2 Examining Environmental Effects of Rockfish Catch-and-Release Survival: Does Low 

Oxygen Contribute to Mortality Following Barotrauma?

This 2013 BREP project, to be carried out by the University of California, San Diego, is 

designed to determine the effects of low levels of dissolved oxygen on rockfish recovery from 

barotrauma following catch and release. Specifically this will include: (1) determination of 

oxygen concentrations typically experienced by rockfish in the wild using oxygen-sensing 

acoustic transmitters, (2) determination of rockfish voluntary movements in relation to changing 

oxygen concentrations using acoustic transmitters and a three‐dimensional positioning system,

(3) determination of rockfish resting metabolic rates and the critical oxygen concentration at 

which aerobic demands cannot be met both prior to and while recovering from barotrauma, and, 

(4) examination of rockfish survival and recovery at varying dissolved oxygen levels following 

barotrauma. Field and laboratory studies will be implemented to understand the effects of low 

levels of dissolved oxygen on rockfish recovery from barotrauma. Fieldwork will involve a 

tagging study to examine rockfish sensitivity and movements in relation to dissolved oxygen in 

vivo. Laboratory studies will include determination of rockfish oxygen demands and the critical 

oxygen concentration causing stress following simulated capture using a hyperbaric chamber.

3.4 Alaska 

3.4.1 Past Projects

3.4.1.1 Mortality Rates for Crab Bycatch in Trawls

In 2009, scientists from the NMFS Alaska Fisheries Science Center collected data to estimate the 

mortality rates of red king crab (Paralithodes camtsactcus) after passage under the groundgear of 

commercial bottom trawls. This followed the methods of similar research on Tanner and snow 

crabs in 2008. Crabs were recaptured after passing under the central and side sections of a trawl 

footrope, as well as after contacting the sweeps ahead of the trawl. Crabs were also assessed 

after capture by a similar net fished ahead of the trawl, to estimate and account for the effect of 

capture and handling. The scientists also evaluated the effectiveness of modifications to sweeps 

and footrope that were expected to reduce crab mortality. More than 3,700 crabs from 73 trawl 

hauls were assessed for reflex impairments, while more than 738 were assessed and then held in 

onboard tanks to establish the association between these impairments and the probability of 

mortality. Estimates of crab mortality rates after trawl encounters were generated for all major 

Bering Sea crab species. Sweep modification reduced all of those rates.
28

3.4.1.2 Trawl Codend Mesh Size and Shape Investigations to Reduce Catch and Discard of 

Undersized Pollock

This S-K Grant Program project, completed by the Alaska Fisheries Development Foundation in 

2000, was designed to test the survival of small pollock that escape through codend and 

intermediate trawl meshes. At-sea experiments were conducted in the Gulf of Alaska by 

replacing top panels of the trawl codend and extensions with escape panels for selectivity and 

escape mortality trials. Escapees from the meshes were herded via a specially designed top panel 

cover into a specially designed caging system and recaptured. Collection units were towed to a 

cage-staging site and secured to the bottom. Captured pollock were monitored daily by divers 

over 14 days to determine mortality. Results indicated that most of the mortality took place 

during the first four post-escape days. Thereafter, mortality was low but continued until the 

experiment was terminated. 

Mortality was clearly related to fish size, with large fish more likely to survive the trawling and 

escape process. Results suggested lower mortalities for fish escaping meshes in the extension 

than fish escaping through the codend. Fourteen-day mortality caused by escapement and the 

caging/holding processes ranged from 46–84% for pollock that escaped through the codend 

meshes and from 47–63% for fish that escaped through intermediate meshes.

3.4.1.3 Practical Application of Fishing and Handling Techniques in Estimating the Mortality of 

Discarded Trawl-Caught Halibut

This S-K Grant Program project, completed by the Alaska Fisheries Development Foundation in 

1998, was designed to evaluate the practical application of two estimates of mortality for 

discarded trawl-caught halibut. Halibut bycatch mortality was estimated via two models: the 

International Pacific Halibut Commission (IPHC) model, which relates halibut condition to 

halibut mortality; and the University of Washington (UW) model, which considers mortality as a 

function of fishing and handling practices. The results indicate that trawl-caught halibut 

mortality can be reduced through modified fishing and handling practices, and that current 

observer sampling practices lead to overestimates of mortality when the IPHC method is 

employed.

3.4.2 Current Projects

3.4.2.1 Use of Digital Imaging Technology to Reduce Released Halibut Mortality in Alaska’s 

Recreational Fishery

This 2013 BREP project, to be carried out by the Alaska Charter Association, is designed to 

develop digital imaging technology for the recreational fishery to measure halibut lengths. This 

project will test the use of digital imaging technology, which should reduce handling times and 

physical injury to fish, thereby reducing release mortality. This project’s planned development 

of an at-sea means to validate trophy-sized halibut also should reduce halibut mortality by 

encouraging the release of more halibut. Specifically, this project will (1) determine the 

relationship between morphometric features on the head of a halibut to its fork length and (2) 
29

develop and field test a Smartphone digital imaging application that will display length and 

weight of halibut after capturing an image of a halibut’s head.

3.5 Pacific Islands 

3.5.1 Current Projects

3.5.1.1 Estimating Post-Release Mortality in Istiophorid Billfish

This BREP-funded project, which began in 2010 and is ongoing, is using PSATs to estimate the 

post-release survival of large Pacific blue marlin (Makaira nigricans) and striped marlin (Kajikia 

audax) released from pelagic longline gear. These data will provide important information about 

post-release survival of marlin bycatch in the Hawaii-based tuna longline fishery. This study 

also plans to establish biochemical predictors of morbidity and mortality from tissue plugs and 

blood. This approach conducts comprehensive pathophysiological analyses of large numbers of 

fish (including tagged fish) to diagnose primary factors that account for the fish condition, as 

well as secondary factors that might change dramatically but have little impact on survivability. 

Integration of PSATs and pathophysiological analyses generates predictive power. The primary 

benefit expected from this project is to generate robust estimates of post-release survival of 

striped and blue marlin released from longline fishing gear that targets tuna.
30

4. How Release Mortality Assumptions Are Incorporated into Stock Assessments

In most cases, stock assessment models rely on the most accurate estimates possible of total 

removals from a population. In addition to harvest, total removals must include mortality 

associated with discarded individuals. Incorporating the rate of release mortality into stock 

assessments is possible, but has proven difficult because accurate estimates of release mortality 

are often unavailable. Numerous factors affect mortality following release, but estimates of 

mortality rates are often unavailable. Further, incorporating estimates derived from controlled 

studies into stock assessments may be overly simplistic due to the complex influences affecting 

release mortality. 

When mortality rates are undetermined, some stock assessments take a conservative approach 

and assume a 100% release mortality rate. Thus, all released fish, along with the harvest by the 

fishery, are assumed to represent the total removals by the fishery. Applying a constant 

mortality rate to all discards simplifies the estimation of total removals because it occurs outside 

of the assessment model. However, applying constant mortality rates as a proxy may be 

inappropriate because of the range of factors and interactions that affect the true discard 

mortality. Although constant discard mortality rates may be appropriate for some stocks, it is 

likely that adopting proxy values for these estimates may be misrepresentative in many cases, 

and use of a constant discard mortality rate may be unrealistic. Stock assessments that include 

some data about mortality rates are sometimes able to apply gear-specific mortality rates.

To effectively account for varying release mortality rates within a stock, absolute estimates of 

mortality rates should be available for all factors that may influence the release mortality, such as 

fish size, gear type, or environmental factors. When absolute rates are unavailable for all factors, 

innovative approaches must be employed, and buffers for uncertainty may be invoked to ensure 

that mortality rates are not underestimated when attempting to account for mortality rates 

estimated to be less than 100%. Alternative approaches to mortality rates include:

1. Constant rate: Commonly used in stock assessment, this method applies a constant 

mortality rate, which could be 100% or a lesser number, to all discards.

2. Modified Delphi method: An iterative decision-making process designed to come to 

agreement on divergent or disparate opinions or data and often assumes a constant rate, 

but one that may be less than 100%. This approach strives to reach consensus agreement, 

but its results may be no more accurate than existing prior assumptions regarding discard 

mortality rates.

3. Mortality assessment predictor: A viability ranking system is developed and applied at 

the stock assessment level to estimate mortality among major factors. This approach 

applies a viability technique, as opposed to directly sampling fish, at the stock assessment 

level (e.g., making proxy estimates for different sources of mortality such as estimates for 

fish caught in trawls versus pots).

4. Mortality models: Bayesian or other methods incorporate the best available data to create 

plausible mortality curves that can be applied in the stock assessment model.

5. Viability assessment: Detailed viability indices are developed and recorded for a subsample of the total discards. This approach involves actually sub-sampling fish and 

applying a viability predictor for the sample and then extrapolating it to the whole 
31

population (e.g., using viability estimates derived from fisheries observers to estimate 

mortality rates for separate gear types).

The appropriate approach for estimating mortality following release will depend on the 

variability in release mortality rates, as well as the data and resources available to inform the 

assessment model. The impact of discard mortality on assessments can range widely depending 

on the size of the discard component relative to the overall removals, as well as the mortality 

rate(s) used.

Methods for estimating discard mortality rates and accounting for total mortalities in assessments 

are not always complementary. For example, the total number of fish caught in recreational 

fisheries is estimated by the Marine Recreational Information Program (MRIP). The MRIP 

classifies fish into three categories:

1. Retained for harvest

2. Dead but not brought to dock (i.e., used as bait or released dead)

3. Released alive

In stock assessments, total numbers of dead removals include fish that are harvested or released 

dead (not brought to dock). Constant discard mortality rates, which are determined in separate 

studies, are applied to the number of live releases. However, these discard mortality studies 

often include both mortality of live releases plus fish that died immediately. Unless immediate 

mortalities can be separated out of an estimate of discard mortality rate, a fish that died 

immediately may get counted twice: once as a dead fish in the MRIP survey, and then again as a 

discard mortality rate applied to live releases.
32

5. Approaches to Developing Revised Post-Release Mortality Assumptions

Developing appropriate release mortality assumptions is a complicated task, often fraught with 

uncertainties arising from lack of reliable information on various capture and release scenarios as 

well as variability among the factors affecting release mortality. The task is further complicated 

by the fact that post-release mortality does not always occur immediately, when fishermen or 

observers can observe it. Due to injury, physiological stress from the capture and handling 

experience, increased predation risk, and various other (often subtle) sub-lethal impacts, 

mortality can result shortly after a fish is discarded, or in the longer term, days to even months 

after the initial capture event. Finally, mortality also may differ significantly among species; the 

type of fishery (e.g., trawl vs. non trawl methods, commercial vs. recreational methods); how the 

fish are handled (e.g., time on deck, expertise of handlers, whether any re-acclimation efforts are 

made); the habitat from which the fish are caught (e.g., water temperature and depth); the 

characteristics of the fish themselves (e.g., sex, size); and as a function of several other factors. 

Complicating matters, many of these factors are compounding or interactive. For the broadest 

possible application, the design and interpretation of release mortality investigations should 

therefore account for the broadest possible conditions relevant to that species and/or fishery. 

Although much work is being done to study the impact of these factors on release mortality 

estimates, most often those who develop mortality rate estimates have limited information to 

work with. The information limitations can be grouped into two broad categories. First, for 

many species there is either no information available, or only anecdotal information along with 

expert opinion. Second, when peer-reviewed studies of release mortality are available, they 

often do not fully characterize the release mortality experienced in the fishery. For example, a 

study may employ experimental conditions that do not accurately reflect actual fishing behavior, 

or the study design many not address longer-term mortality, or it may evaluate only a subset of 

the fishing methods used in the fishery. Because of the variability in methodologies and the lack 

of information available for robust discard mortality estimates in the literature, stock assessment 

scientists often must adopt alternative approaches for identifying mortality discard estimates 

applicable to individual stocks. In New England the Delphi Technique has been used. On the 

West Coast a three-step, model-based approach is being employed. 

These alternative approaches do not always yield more robust estimates of discard mortality. In 

addition, managers should consider using a precautionary approach to account for uncertainty 

when applying such estimates.

5.1 Delphi Technique

The Delphi Technique is a decision-making process that brings together a group of experts and 

aims to reach a consensus through an iterative process of anonymous questionnaires and 

discussions of the questionnaire results. 

In New England, the Gulf of Maine Research Institute conducted an anonymous online 

questionnaire that invited industry members, scientists, and fishermen to provide their opinions 

on the percentage of discarded Atlantic cod that die during commercial otter trawl, commercial 

gill net, commercial hook and line/longline, and recreational hook and line activities. After the 
33

online questionnaire was completed, a workshop was held that brought together scientists, 

fishermen, fisheries managers, and others. Workshop participants discussed the questionnaire 

results, worked through available discard information, and heard input from industry members. 

Participants then completed a second anonymous questionnaire and had a final discussion 

reviewing questionnaire results and reaching consensus on the assumed mortality rates for the 

different fishing activities. 

During the course of the workshop, industry representatives and scientists shifted their opinions 

based on the discussions and the information presented. Although the results of the initial 

questionnaire showed large differences in the rates thought to be appropriate by the two groups 

of participants, by the end of the workshop the group was in agreement about the rates they 

would recommend adopting in future cod stock assessments. 

The Delphi Technique has a number of strengths. Stakeholders are comfortable with the process, 

the process itself results in more informed participants, and its participatory nature means that 

stakeholder knowledge, which is rarely codified in the scientific literature, can be used to inform 

the decision. Perhaps most importantly, it provides a way to arrive at agreed-upon values for the 

assumed mortality rate. 

But the Delphi Technique also has weaknesses. It takes a significant amount of time and 

resources to properly conduct the exercise, and even more time and resources are needed if the 

exercise must be conducted separately for each species. In addition, it is unclear how the various 

issues under discussion during the process actually ended up influencing the agreed-upon 

assumed rates, which can make it difficult for those not involved in the process to understand 

how the final decisions were reached. In addition, it can be unclear whether the final agreed 

discard mortality rates are a better approximation of the true discard mortality compared to the 

status quo. That is, the technique does not yield formal estimates of the mortality rate with 

known statistical properties, including measures of statistical bias and uncertainty. Rather, it 

yields values agreed upon by those who took part in the exercise, but the relationship of these 

values to the truth is unknown and unquantifiable.

5.2 Model-Based Approach

The Groundfish Management Team (GMT) of the Pacific Fishery Management Council (PFMC) 

developed methods for estimating mortality of groundfish species discarded at the surface 

(PFMC 2008), as well as methods for estimating mortality that reflect release with descending 

devices for a sub-set of rockfish species (PFMC 2012, PFMC 2013, PFMC 2014). Estimates of 

groundfish mortality that were based on accounting for three types of discard mortality: (1) 

“surface” mortality that is observed during the catch, handling, and release of the fish; (2) shortterm, below-surface mortality that has been observed in research trials; and 3) longer-term, 

below-surface mortality for which little or no information is available. 

Estimates of surface mortality were created by developing a generalized linear model of the 

proportion of fish released dead by depth and by species based on information from observer 

program data (PFMC 2008). For those species for which a species-specific model could not be 

developed due to an insufficient amount of observer data, a guild-based method was used to base 
34

the mortality rate by depth on species with similar depth distribution and vertical orientation in 

the water column. The surface mortality estimates were then treated as baseline mortality rates. 

To account for the short-term, below-surface mortality, those initial rates were increased by a 

different amount depending on whether the species was shallow- or deep-dwelling, according to 

research by Albin and Karpov (1996). The GMT used its expert judgment to apply an additional 

5% mortality per 10 fathoms of depth to account for a lack of data regarding longer-term, belowsurface mortality. Future revisions may utilize more recent data regarding long-term mortality 

rates from acoustic tagging studies (Wegner et al. in prep) to better inform long-term mortality 

estimates in future iterations of surface release mortality estimation.

The GMT subsequently estimated mortality rates reflecting release with descending devices for 

cowcod, canary, and yelloweye rockfish management. These rates accounted for reduced 

mortality as a result of being rapidly returned to depth, which mitigated barotrauma, sun 

exposure, and surface predation–related mortality. The mortality estimation method 

incorporated short-term mortality rates from cage studies (Jarvis and Lowe 2008, Hannah et al. 

2012) and long-term mortality rates from acoustic tagging studies (Wegner et al. in prep). The 

mortality estimates and associated confidence intervals in each depth bin were estimated using a 

Bayesian Hierarchical Method, which accounted for variation between species and the sample 

size of each species using data from the latitude of the focal species (PFMC 2012, PFMC 2013, 

PFMC 2014). 

The assumptions, biases, and uncertainties associated with the estimates were fully vetted, 

discussed, and addressed to the extent possible given available data. Proxy species were used to 

bolster the sample size in each depth bin because the focal species were uncommon in some 

depth bins. The PFMC adopted buffers for uncertainty based on the upper 90% confidence 

interval estimate of short-term mortality given the sample size in each 10-fathom depth bin. The 

proposed mortality estimates were reviewed and approved by the PFMC Scientific and Statistical 

Committee (SSC) and adopted by the PFMC for use in management with retrospective 

application in 2013 and in the years to come. Future research to increase the sample size of 

focal species, evaluate seasonal fluctuations in mortality rates, determine mortality rates in 

depths greater than 100 fathoms, and provide a generalized or proxy estimate of mortality for 

application to other rockfish species would improve estimates and allow application of mortality 

rates reflecting use of descending devices to a broader suite of species. 

This model-based approach has many strengths. It specifically takes into account immediate, 

short-term, and longer-term mortality, allowing for explicit consideration of the different types of 

damage that can be inflicted when a fish is captured. There are clear explanations for how each 

aspect of the mortality estimate is produced. Finally, this method can produce estimates for 

multiple species. Stakeholders with valuable insights and information had the opportunity to 

participate in review of the methods within the PFMC process over two years of development, 

but were not directly involved in determining the rates themselves, removing subjectivity. 

However, there are a few weaknesses associated with this type of process as well. The method 

employs some data from sources that have not been peer-reviewed, although methods were 

reviewed and approved by the SSC. Scientific expert opinions were used to fill in gaps in longterm mortality for surface mortality estimates where there was little scientific information 
35

available. When estimating mortality reflecting use of descending devices, proxy data from 

other species and estimates for the same species in deeper depth bins were used when data for 

the focal species were unavailable or sparse.
36

6. Identification and Prioritization of Data Gaps

In September 2013, a workshop attended by scientists from within and outside of NMFS was 

held to help NMFS identify and prioritize data gaps related to discard mortality estimates and 

related stock assessment issues. (Appendix A lists the workshop attendees.) The workshop 

attendees identified four data gap categories:

1. Understanding the factors affecting discard mortality estimates

2. Developing discard mortality estimates

3. Improving and refining existing discard mortality estimates

4. Enhancing outreach regarding discard mortality estimates

For each data gap category, workshop participants listed specific data gaps and then identified 

the data gaps they felt were most important. Each person was limited to three “votes.” Each of 

the listed gaps was important to at least one workshop attendee, by virtue of its eligibility for 

votes, but some gaps were more important than others. Listed below are data gaps by category, 

with number of votes received indicated in parenthesis.

Understanding the Factors Affecting Discard Mortality Estimates

1. Collect spatially explicit discard data (4).

2. Understand the impact of best versus actual practices on mortality (3).

3. Understand the relationship of initial to long-term mortality (3).

4. Consider mortality estimate impacts on long-term management and rebuilding goals (3).

5. Quantify impacts and efficiency of best practices (1).

6. Increase commercial and recreational discard observations (1).

7. Identify when mortality estimates can be generalized and when a species or fishery needs 

to be looked at individually (1).

8. Identify factors that have a strong impact on survival (1).

9. Conduct laboratory experiments on best-practice efficacy (0).

10. Understand how shifts in mortality rates impact stock assessments (what causes 

sensitivity or lack thereof) (0).

11. Capture the diversity of methods people use to catch fish, as well as the impacts these 

methods have on mortality (0).

12. Capture the range of individual behavior occurring in a single type of fishery (e.g., 

skipper behavior) (0).

13. Conduct laboratory experiments to identify and quantify factors that influence mortality 

(0).

Developing Discard Mortality Estimates

1. Develop baseline discard mortality information, including an understanding of underlying 

factors and their interactions (12).

2. Measure release mortality in fishery, as opposed to lab, conditions (11).

3. Develop reliable and robust proxies for morality (both short- and long-term) (11).

4. Conduct research on unaccounted escapement mortality (10).

5. Examine longer-term impacts of venting and descending devices (5).

6. Explore the sub-lethal effects of capture (4).

7. Determine the impacts of repeated capture (4).
37

8. Conduct longer-term holding studies (3).

9. Establish better controls for catch-and-release studies (2).

10. Determine more creative tagging practices and options (2).

11. Identify discarded species more accurately (2).

12. Distinguish among mortality estimates that result from different types of trauma (e.g., 

barotrauma vs. hooking vs. handling) (2).

13. Conduct research on the effects of fishing location (e.g., inshore, offshore) on mortality 

(2).

14. Conduct fish health studies (2).

15. Quantify and investigate unaccounted sources of mortality (1)

16. Conduct research on the effects of temperature on mortality (1).

17. Identify species-specific mortality rates (0).

18. Identify depth(s) to which fish should be returned (0).

19. Identify fish behavior changes post-capture (0).

20. Conduct research on ghost gear mortality (0).

21. Conduct submergence studies (i.e., studies focusing on the ability or inability of a 

released fish to submerge) (0).

22. Conduct research on the effects of fishing depth on mortality (0).

Improving and Refining Existing Discard Mortality Estimates

1. Identify optimal sampling designs for accuracy and precision of discard mortality 

estimates (7).

2. Collect a wider range of recreational data including hook type, depth, and discard 

condition (5).

3. Use sensitivity analyses to identify which discard mortality rates need to be more 

accurate and/or precise (4)

4. Validate volunteer and self-reported discard data (2)

5. Examine how mortality estimates are currently used in stock assessment models (e.g., are 

estimates developed before the stock assessment process or as part of the process?) and 

whether this usage can be improved (1).

6. Identify mortality estimates based on insufficient information (0).

7. Conduct laboratory experiments that more accurately reflect fishery conditions (0).

8. Determine if discard mortality rates vary based on whether the discarded species is a 

target species or not (0).

Enhancing Outreach regarding Discard Mortality Estimates

1. Communicate how discard mortality estimates are created, used, and impact stock 

assessments, annual catch limits, and management (6).

2. Identify behaviors that fishermen would consider changing, as well as the barriers to 

change (1).

3. Quantify how often best practices are used in various fisheries (1).

4. Incentivize best behaviors and high-quality reporting back (0).

5. Identify to what extent best practices are able to be employed (0).

6. Identify mortality factors that fishers can control (0).

7. Quantify compliance with regulations and enforcement (0).
38

The following data gaps from the four identified categories received at least three votes and 

could be considered the most important data gaps identified at the workshop:

• Develop baseline discard mortality information, including an understanding of underlying 

factors and their interactions (12).

• Measure release mortality in fishery, as opposed to lab, conditions (11).

• Develop reliable and robust proxies for mortality (both short- and long-term) (11).

• Conduct research on unaccounted escapement mortality (10).

• Identify optimal sampling designs for accuracy and precision of discard mortality 

estimates (7).

• Communicate how discard mortality estimates are created, used, and impact stock 

assessments, annual catch limits, and management (6).

• Examine longer-term impacts of venting and descending devices (5).

• Collect a wider range of recreational data including hook type, depth, and discard 

condition (5).

• Explore the sub-lethal effects of capture (4).

• Determine the impacts of repeated capture (4).

• Use sensitivity analyses to identify which discard mortality rates need to be more 

accurate and/or precise (4)

• Collect spatially explicit discard data (4).

• Understand the impact of best versus actual practices on mortality (3).

• Understand the relationship of initial to long-term mortality (3).

• Consider mortality estimate impacts on long-term management and rebuilding goals (3).

• Conduct longer-term holding studies (3).

Although workshop participants identified a large number of data gaps, some of the above gaps 

could be lumped together (e.g., by focusing on all effects of capture, as opposed to sub-lethal 

effects or repeated-capture effects). Likewise, some of the gaps identified above are very 

specific gaps that could be nested within other more generally described gaps.

Development of reliable and robust proxies for mortality is especially important because of the 

high cost of release mortality studies and the need to increase the power of studies. In addition, 

workshop participants identified the need for well-designed baseline studies using robust 

methodologies that can be applied to multiple scenarios, with an emphasis on long-term studies 

that accurately depict a fish’s mortality in the wild. Such long-term studies could include 

creative tagging options, dual-frequency identification sonar, and other methods.

Providing effective outreach regarding discard mortality is also important because fishermen 

need to appreciate and understand the relevant science when science-based management 

measures require them to change their practices. Outreach requires an understanding of where 

fishermen receive information about their fisheries and willingness to devote substantial effort to 

change fishermen’s attitudes.
39

7. Identification and Prioritization of Species-Specific Research Needs

At the September 2013 workshop, scientists from within and outside of NMFS identified and 

prioritized criteria related to species-specific research needs. However, when prioritizing 

research, one should always ask whether the research is likely to yield significant gains. For 

example, in some fisheries 100% of discards are presumed to be dead. Additional costly 

research may result in this estimate being revised downward somewhat, but perhaps not to a 

large degree. In that case, scarce resources might be better spent on species where research is 

likely to have a larger impact, that is, where the anticipated delta between status quo and 

anticipated revised estimates is large.

In addition, some species may require extensive study; for example, multiple studies may be 

needed to address the same research question so that different stakeholders can have confidence 

in the results. In these cases, prioritization of research needs may not be practical.

Participants at the 2013 workshop identified a list of questions (in no particular order) that 

managers and scientists should ask when attempting to prioritize the most important speciesspecific research needs:

• Is the species economically and/or ecologically valuable, both alone and in terms of its 

impacts on other species?

• What is the magnitude of discards as a proportion of catch and harvest of the overall 

stock size (that is, Fdiscards as a fraction of FMSY)?

• Is the species highly restricted by managers?

• If the species is highly restricted, do these restrictions result in a large amount of 

discards?

• Is the species a “sentinel” species that is iconic, popular, “political,” or has a high 

economic value (e.g., red snapper in the Gulf of Mexico)?

• Does the fishery (recreational or commercial) that targets the species have a strong 

interest in sustainability or formal certification or ecolabeling (e.g., by the Marine 

Stewardship Council)?

• How receptive and helpful are the fishery stakeholders regarding discard mortality 

reduction?

• Are current discard estimates (both magnitude and mortality rates) for the species highly

uncertain?

• What is the species’ stock status?

• How sensitive to uncertainty is the determination of the species’ stock status 

benchmarks?

• What is the species’ life history characteristics (e.g., productivity) and susceptibility (e.g., 

catchability, habitat availability) in the context of its fishery (either single- or multispecies)?

• When subjected to a Productivity-Susceptibility Analysis (PSA) (Patrick et al. 2009), 

does the species receive a low productivity score and a high susceptibility score?

• Do handling practices make a significant difference in survival for the species?

• Is the species listed under the Endangered Species Act or is it otherwise rare?

• To what extent is the species being recreationally or commercially utilized?
40

• Has the species been subject to the stock assessment process, either through a formal 

data-rich process or a less formal data-poor process?

• Is the species a constraining species, that is, do discards of the species restrict the ability 

of fishermen to target other valuable species?

• Are scientists and/or managers able to determine that they have enough data on the 

species to make sound management decisions?

Workshop participants discussed these questions further and mostly agreed on a list of seven 

high-priority criteria that should help direct scientists and managers in focusing release mortality 

resources on particular species:

1. The species’ status as restricted, rare, and/or iconic.

2. The species’ life history and/or PSA results.

3. The species’ economic impact and/or marginal value.

4. Assumed Fdiscards as a fraction of FMSY.

5. The level of stakeholder engagement and/or political sensitivity regarding the species.

6. The amount of available data on the species.

7. The extent to which release mortality is an emerging concern for the species.

Workshop participants also had some general thoughts about species-specific release mortality 

research. One participant felt that such research should focus on a balance of short- and longterm efforts, keeping in mind the issue of “bang for the buck” and political considerations. 

Another participant felt it was important to not prioritize research efforts based on currently 

identified low release mortality rates, because those rates need to be considered in relation to the 

species’ overall biological context. For example, even though a species’ estimated release 

mortality rate may seem low, the species could be highly endangered and worthy of resources to

further reduce the release mortality rate.

After identifying the list of seven high-priority criteria related to the identification of speciesspecific research needs, workshop participants discussed select important species in several 

regions of country in terms of the seven criteria. The following sections summarize these 

discussions.

7.1 West Coast Examples

Workshop participants identified West Coast rockfish as a type of fish with several research 

needs. For example, yelloweye rockfish (Sebastes rummerimus) is an overfished species for 

which harvest limits can constrain the landings of other non-overfished species. Yelloweye 

rockfish can live for over 100 years and have a high marginal economic value. Yelloweye 

rockfish must be discarded when caught, and yelloweye rockfish discard mortality alone is 

sufficient to limit fishing seasons and create depth restrictions for a number of co-occurring 

healthy stocks in mixed-stock fisheries in Washington, Oregon, and California. The fish is 

somewhat iconic, and fishery stakeholders are engaged in the management of yelloweye 

rockfish. 

Although great strides have been made regarding mortality rates for yelloweye rockfish, in terms 

of surface release and fish released at depth with descending devices, several data gaps remain. 
41

Short-term mortality rates reflecting surface release are well-informed (PFMC 2008), but 

yelloweye rockfish long-term mortality rates are less known. Additional data on long-term 

mortality rates would improve estimates of mortality. Currently, long-term surface release 

mortality rates are informed by expert knowledge, with a precautionary 5% of additional 

mortality per 10 fathoms of depth. This may be excessive in depths greater than 30 fathoms

given recent estimates of 15% mortality for proxy species in Wegner et al. (in prep) for fish 

caught in 50-100 fm.

Mortality rates reflecting release at depth with a descending device are less complete (PFMC 

2012, PFMC 2013, PFMC 2014). Data are available from depths of less than 50 fathoms, but 

little is known about mortality in deeper depths; the assumed mortality estimates used for 

management currently are informed by proxy data from other species. Current estimates indicate 

significant reduction in mortality when fish are descended back to depth (27% mortality in 30 to 

50 fathoms and 57% mortality in 50 to 100 fathoms) as compared to surface release (100%

mortality in greater than 30 fathoms). Yelloweye rockfish exhibit low short-term mortality when 

descended, as do many other species of rockfish for which data currently are available (Jarvis 

and Lowe 2008, Hochhalter and Reed 2011, Hannah et al. 2012, PFMC 2012, PFMC 2013, 

PFMC 2014, Wegner et al. in prep). Further research regarding long-term mortality and 

mortality in deeper depths reflecting release with a descending device would reduce uncertainty 

related to the estimates, increase precision, narrow confidence intervals, and reduce mortality 

estimates because the Pacific Fishery Management Council decided to adopt rates based on 

upper 90% confidence interval estimates to provide a buffer against management uncertainty. 

Pacific salmon are iconic fish, and their life history is well-known. However, researchers know 

little regarding salmon release mortality rates across various types of gears. Bycatch of certain 

salmon species can constrain commercially important non-overfished fisheries. Because of these 

potential economic impacts, release mortality studies should focus on the type of salmon 

encountered in these fisheries as bycatch. Fishery stakeholder engagement regarding salmon 

management and research is high, as evidenced by the fishing industry’s pursuit of Marine 

Stewardship Council certification for salmon. This stakeholder engagement could improve 

fishing practices.

Pacific halibut (Hippoglossus stenolepis) is a well-studied groundfish that encounters a variety of 

gear types. Managers are concerned with halibut release mortality from trawl fisheries, and 

observer programs are collecting data on halibut release condition. Release mortality rates seem 

to be highly influenced by the amount of time taken to get halibut back into the water. Nontrawl release mortality rates for halibut can be low, but for trawls the rate is almost 100%. 

Related to this high mortality rate, one workshop participant mentioned that it is important to 

focus on immediate mortality as well as longer-term release mortality. Halibut excluder devices 

have the potential to reduce these mortality rates. Pacific halibut are iconic, and Pacific halibut 

bycatch can constrain directed fisheries for other species. Species abundance for Pacific halibut 

has been dropping in recent years, but bycatch levels have not. Bycatch mortality represents 

approximately 20% of Pacific halibut removals.
42

7.2 Southeast Examples

The federal waters of the Southeast United States are inhabited by numerous commercially and 

recreationally important species. Chief among these are members of the snapper-grouper 

complex, a group of physoclistous fishes that inhabit deep-water areas and are subject to 

considerable pressure trauma after being pulled from reef habitats. These species include red 

snapper (Lutjanus campechanus), vermilion snapper (Rhomboplites aurorubens), black sea bass 

(Centropristis striata), gag grouper (Mycteroperca microlepis), and red grouper (Epinephelus 

morio). Discard estimates for these species have been derived from numerous studies. The 

snapper-grouper complex also includes other managed reef fishes, such as red porgy (Pagrus 

pagrus), gray triggerfish (Balistes capriscus), and white grunt (Haemulon plumieri), for which 

estimates of discard mortality are either imprecise or non-existent. 

Workshop participants identified vermilion snapper as a species relevant to the seven highpriority criteria. Landings of vermilion snapper are not restricted. The species is neither rare nor 

iconic, although it is often mistaken for red snapper. The vermilion snapper stock has been 

rebuilt in recent years and is not undergoing overfishing. Vermilion snapper has a resilient life 

history, maturing early and spawning frequently. Vermilion snapper is not a particularly datarich species, but scientists have identified regional differences between vermilion snapper from 

the Gulf of Mexico and the South Atlantic. Stakeholders are generally not particularly attentive 

to vermilion snapper issues unless the stock becomes overfished. This species has been studied 

to determine rates of post-release survival after both venting and non-venting treatments over a 

wide range of depths off the U.S. Southeast coast (Collins et al. 1999).

In comparison to the less-studied vermilion snapper, the iconic and overfished red snapper is 

characterized by much study and a large amount of available data. However, managers are 

challenged to focus the data so they can be used to make helpful management decisions. Red 

snapper management is highly dynamic, and managers do not always know precisely where the 

fishery will operate. Red snapper seasons are very short and are characterized by high levels of 

discards. Estimated release mortality rates also are highly variable and depend on capture depth 

and other factors. As the red snapper stock rebuilds, they are appearing in shallow areas and 

other areas where they have not been observed previously. Workshop participants felt that range 

and effort information are key data gaps. In addition, workshop participants felt that future 

research should refine the existing variability in release mortality rate estimates. Workshop 

participants also felt that baseline research related to release mortality may be adequate, but a 

larger region-wide study is needed to align red snapper research results to stock assessment 

needs, building on smaller projects that have already been completed (see Appendix B).

Workshop participants also discussed the deep-water snapper-grouper complex, a well-known 

group of fish that includes snowy grouper (Epinephelus niveatus), Warsaw grouper (Epinephelus 

nigritus), speckled hind (Epinephelus drummondhayi), and golden tilefish (Lopholatilus 

chamaelonticeps). These species are generally long-lived and slow-maturing. These species 

also can be constraining for other directed fisheries in some instances. Stock assessments for 

these species assume a 100% release mortality rate, although recent use of decompression 

devices suggests this assumption should be reexamined. Stakeholder engagement is not high, 

but it could be increased with the promise of increased angler access to these species or, 
43

conversely, as managers examine the use of marine protected areas to help ensure the 

sustainability of these species by eliminating bycatch mortality over a portion of the range of 

each of these deep-water species. Engagement of stakeholders as research partners during the 

testing of descending devices also could increase stakeholder engagement.

Black sea bass, like vermilion snapper, are not iconic, restricted, or rare. This species recently 

has been studied to determine rates of post-release survival after capture using traps and hook

and line gear. That research project established a group of true control fish by tagging fish on 

the sea bottom so that pressure trauma could be accurately accounted for in estimating rates of 

discard mortality for fish caught over a variety of depths and conditions (Rudershausen et al. 

2014). Black sea bass is of some interest to stakeholders because the population is increasing. 

Black sea bass are not overfished. Discard percentages for this species can be quite high when 

commercial and recreational seasons close due to annual catch quotas being reached, which 

forces fishermen to discard black sea bass. Spatially explicit release mortality research is needed 

for black sea bass, because its geographical range may be expanding. Scientists have been able 

to provide some basic advice to fishermen regarding venting black sea bass. Venting does not 

appear necessary to increase post-release survival of this species over the wide range of depths

where it is commonly encountered in this region (Rudershausen et al. 2014). Tagging projects 

are appropriate for black sea bass because the fish do not move a great deal and get recaptured 

frequently, often from the same location (Rudershausen et al. 2014). Additional research on 

black sea bass would be helpful in determining where black sea bass are being discarded. If 

black sea bass are being caught and released in shallow water, barotrauma is not a large issue, 

but if black sea bass are being caught and released in deeper water, then barotrauma is a factor. 

Even though the accepted barotrauma rate for this fish is relatively low, the large number of 

released fish (millions per year) could result in a large number of dead discards. In addition, 

black sea bass could serve as a vehicle for learning about release mortality characteristics that 

could be applied to other, similar species, such as gag grouper and red grouper.

7.3 Northeast Examples

Workshop participants considered skates (as a species group) in relation to the seven highpriority criteria. Managers had assumed that skates exhibit a large variety of reactions to 

capture, and short-term scientific studies have confirmed this. Longer-term studies may yield 

different results. One of the skate species, thorny skate (Amblyraja radiate), is of conservation 

concern because its biomass is at a historically low level. Studies have shown that thorny skates 

experience low levels of short-term release mortality. However, researchers suspect that longterm mortality rates for thorny skates may be much higher. The thorny skate and the other skate 

species are not iconic, and fishery stakeholders are not highly involved with skate research. 

Skate bycatch does not constrain fisheries, and skate management is a challenge because data 

collection efforts do not always differentiate among the various species. The fraction of Fdiscards

to FMSY is unknown.

Workshop participants also discussed striped bass (Morone saxatilis) in terms of the highpriority criteria. Striped bass are iconic in New England, and striped bass populations can be 

found in the waters of several states. Striped bass fisheries have large economic impacts on 

states where they are fished. Discard rates are high due to large catch and release fisheries. 
44

Stakeholder engagement is substantial in some states. Release mortality research has been 

limited and has occurred mostly in impoundments and reservoirs. Striped bass are exposed to 

the air when caught because anglers like to photograph them. Fishing methods can impact 

striped bass release mortality. In addition, striped bass life stage can have an important impact 

on release mortality rates.
45

8. Best Practices and Techniques for Release Mortality Research

Participants at the September 2013 release mortality workshop spent some time discussing best 

practices and techniques related to release mortality research, especially effective outreach 

efforts related to release mortality research, as well as tagging and the related issue of acoustic

arrays. Workshop participants felt that knowing the pros and cons of various techniques can help 

scientists and management agencies write better research proposals. Knowing the pros and cons 

of various research techniques also can help scientists new to the field of release mortality 

research develop high-quality research proposals. 

8.1 Outreach

Workshop attendees felt that outreach efforts should carefully consider the needs of the audience. 

For example, release mortality experts who create videos should try to ensure the videos are 

high-quality and even high-definition, because many fishermen watch such videos on their 

phones. Attendees felt that underwater video camera footage is especially meaningful to 

fishermen when they consider modifying their fishing practices. Although workshop attendees 

felt that brevity was important to video outreach (e.g., a 3-minute video is usually more effective 

than a 9-minute video), workshop attendees also thought that longer-format versions can be 

effective in certain situations. For example, fishermen might be able to watch a 15-minute video 

at home on their personal computers, or a commercial boat’s crew could watch a 15-minute 

video on safe-release practices while on a fishing trip. Shorter videos may be more effective on 

party boats where cabins can be cramped and anglers are busy setting up gear and identifying 

fishing sites. Additional video content could be made available for passengers with special 

interest beyond the initial shorter video message. Short videos available online for viewing on 

smartphones may be more engaging than videos shown on a TV on a crowded boat.

Attendees cited several different methods to communicate best practices to fishermen. Agencies 

that have contact information can reach out directly to fishermen. This outreach can be more 

successful when local fishing clubs are involved in the dissemination of information. Some 

fishing clubs have even provided descending devices to their members. Fishing clubs also can 

post videos on their websites. Workshop attendees thought that sport fishing talk shows are a 

good outlet for messages regarding fishing practices and fisherman behavior. Trade shows also 

represent a good opportunity to provide information regarding best fishing practices and 

techniques through trade show booths staffed by experts as well as presentations provided by 

experts to trade show attendees. Workshop attendees felt that studies to determine whether these 

communication efforts really change practices are important. 

It is important to note differences in communication approaches for commercial versus 

recreational fishermen. In commercial fisheries, individual contact information is available as 

part of fishing license records, and this can facilitate direct contact with fishermen. Recreational 

fisheries sometimes are less centrally managed and require broader, mass communication 

techniques.
46

One workshop participant commented that the typical annual research funding process is not 

conducive to conducting sustained, long-term outreach efforts, which usually are most effective. 

Another participant mentioned a study he helped conduct of recreational salmon angler 

preferences for receiving information (Nguyen et al. 2012). The study grouped anglers into three 

categories in terms of receiving information on responsible fishing:

1. Traditional anglers, who obtain most of their information informally through other 

anglers or through their fishing network.

2. Investigative anglers, who independently and actively seek out information from a wide 

variety of sources.

3. Networking anglers, who obtain most of their information from tackle shops and by 

reading brochures.

The study concluded that fisheries managers will need a mix of outreach approaches to 

effectively reach all anglers.

Finally, outreach can be crucial to the effectiveness of tag studies. Outreach can help ensure that 

people who encounter tagged fish know how to report the required information, which is 

important to studies of long-term mortality.

8.2 Tagging

Tagging allows researchers to establish a group of control fish with which the discard survival of 

fish in various conditions can be compared (Heuter et al. 2006; Pollock and Pine 2007).

Workshop attendees spent a great deal of time discussing tagging, beginning with the question of 

whether tags are worth their expense. Tagging can encompass conventional “mark-recapture” 

tagging as well as more sophisticated electronic tagging methods. Deploying enough tags to 

obtain a large sample size can be expensive. Workshop attendees generally felt tags were worth 

the expense, especially when compared to the cost of not having the type of information that can 

be derived from tagging. One attendee suggested negotiating with tag manufacturers when 

considering a large purchase, in order to avoid paying face value for electronic tags. 

Workshop attendees were concerned with issues related to the tagging process and retention of 

tags on fish, such as establishing a control population and identify normal behavior for a fish 

after it has been caught, handled, and tagged during the course of a research project. Tagging 

fish in situ could help address this issue, although not all workshop attendees felt that tagging 

processes resulted in adverse impacts to fish. Another attendee expressed interest in 

geomagnetic tags, which could be effective when deployed on bottom-dwelling fish species.

Another attendee pointed out that some fish naturally digest and/or absorb and then expel 

transmitters. For example, fish tagging at an Oregon aquarium has demonstrated that external 

tags can eventually be extruded by fish after 6 to 8 months. Researchers would not be able to 

notice such phenomena if they monitored fish for only 2 to 3 months. Using a “relative risk” 

type of approach to estimate discard mortality of fish in various categories (Heuter et al. 2006) 

can address this problem by assuming that fish across all treatments experience similar rates of 

tag-shedding.
47

Other fish shed transmitters when they encounter hazards in the water. One attendee stated that 

he uses external wire tags for halibut tagging studies involving trawl gear and hook and line gear, 

and he has experienced an approximate 20% loss rate for these tags. Another attendee has 

placed tagged fish in a tank with hazards to try to determine a tag-shedding rate. In addition, 

workshop attendees felt that a combination of laboratory and field studies could examine the 

physical effects of sutures and tag attachment on fish. Researchers need to ensure variability 

between tagging trips, even if they are deploying tags over multiple trips. Among-trip variability 

in accounting for the influences of tagging in studies of post-release mortality can be addressed 

by incorporating abiotic data (e.g., water temperature, deck time) into models estimating discard 

mortality.

8.3 Arrays

Workshop attendees felt that acoustic and/or passive tags can be useful, but these tags create 

challenges when fish move out of the acoustic array field and the tags fail to report. In addition,

some attendees felt that maintaining arrays is costly and labor-intensive. Researchers have 

trouble determining whether a tag stopped reporting due to movement from an array, or due to 

fish mortality. Researchers need to estimate these types of failure rates and incorporate them 

into uncertainty estimates for research projects. 

Carefully planning a tagging study to ensure the array can detect emigrants relative to a fish 

being removed is important here (Bacheler et al. 2009). Kerns et al. (2012) describe a study that 

estimates instantaneous catch-and-release morality using high-reward conventional tags and 

acoustic tags. It is assumed that a fisherman will call in to report the high-reward tag and let the 

researcher know whether the fish was kept or not. This allows the researcher to determine 

whether a fish was a harvest mortality or, if released and found to stop moving soon after a 

capture event, a discard mortality. 

Some attendees felt that scientists have difficulty establishing the extent of array fields for some 

fish when the scientists are unsure of the target fish’s home range. In addition, mortality 

estimates may become inflated if live fish leave an array field while dead fish remain in the array 

field. To overcome obstacles related to arrays, researchers should share tag data so that other 

arrays can pick up fish tag data once a fish leaves its original array field. Underwater gliders and 

autonomous underwater vehicles sometimes have sensors attached that can be used to listen for 

fish that have left their original array fields. In addition, scientists could pick up fish tag signals 

by integrating acoustic sensors into submarines that service oil platforms in the Gulf of Mexico.

8.4 Estimating Mortality Rates using Chamber Studies, Cage Studies, and Acoustic Tagging

Barometric chamber studies, acoustic tagging, and cage studies provide a means of 

approximating mortality rates for fish released using a descending device. Although barometric 

chamber studies provide insight into the effects of barotrauma on survival and condition (Parker 

2006, Smiley and Drawbridge 2006, Rogers et al 2011, Pribyl et al. 2012), cage studies and 

acoustic tagging may provide more representative estimates of discard mortality reflecting the 

use of descending devices. The degree of thermocline, time on deck, air temperature, handling,

and hook location may affect survival (Jarvis and Lowe 2008, Hannah et al. 2012), but these 
48

factors are not reflected in barometric chamber studies. Cage and barometric chamber studies do 

not account for sub-surface predation after release (i.e., lingcod on rockfish and dolphins on red 

snapper), although acoustic tagging would account for such mortality (Wegner et al. in prep). In 

instances where post-release predation rates are expected to contribute significantly to overall 

discard mortality, acoustic tagging may provide more accurate estimates of mortality, or it can be 

used to help determine the rate of predation to be added to the results of cage studies, through

which a greater number of samples can be collected at less cost.

Note that the duration of observation pertinent to mortality rate estimates can be determined 

using acoustic tagging, to set the minimum duration of a cage study. Cage studies can be 

conducted at a lower cost, increasing sample sizes needed to analyze variation due to treatments 

or environmental correlates. Cage studies may also be viewed as being subject to less 

uncertainty than acoustic tagging studies because the fate of individuals that leave the array is 

often unknown, and the fate of those in the array can be difficult to determine definitively 

without controls and visual confirmation. 

Each of these three methods can provide estimates subject to varying biases, assumptions, and 

uncertainties. Buffers can be invoked to ensure the estimates do not underestimate mortality 

rates, but these buffers should be within reason so as not to negate the perceived benefit from use 

of descending devices. The Groundfish Management Team of the Pacific Fishery Management 

Council provided a detailed analysis of such considerations in estimating mortality rates 

reflecting the use of descending devices on cowcod, canary, and yelloweye rockfish, as well as 

buffers for uncertainty (PFMC 2012, PFMC 2013, PFMC 2014).

8.5. Application of Mortality Rates in Management

Although estimating mortality rates that accurately reflect mortality of discarded fish presents a 

formidable task, the application of these rates can present further difficulties given the limitations 

of data currently available from fishery sampling programs. Mortality rates are likely to be gear 

specific, so separate estimates may be needed for different sectors, although mortality rates 

derived for the recreational fishery may act as a proxy for rod and reel commercial fisheries. If 

mortality estimates are depth dependent, sampling programs may need to collect additional data 

on depth of capture and intensify sampling to provide a suitable sample size informing the 

proportion of catch by depth in each depth bin. For species that are rarely encountered due to 

depletion or restrictions intended to minimize encounters, proportions of catch by depth may be 

estimated with a relatively low sample size unless sampling is intensified or data is pooled over 

time to increase the sample size used in each estimate.

In accounting for the use of descending devices, estimates of total mortality from a given fishery 

sector require determination of the proportion of fish released at the surface or with a descending 

device. To obtain data necessary to apply mortality rates reflecting the use of descending 

devices, samplers must inquire as to the disposition of discarded fish in the field, that is, 

determine whether fish are released with or without a device and the fate of fish released on the 

surface. This determination takes time from other data collection priorities and must be weighed 

in light of the importance of this information to possible additional fishing opportunities and/or 

more accurate stock assessments. Therefore, additional sampling or data elements may be 
49

required to collect the data needed to apply depth-dependent mortality rates reflecting surface 

release or release using descending devices. Efficacy of descending devices in returning fish to 

the bottom may vary. Mortality rates assume successful descent of fish, and questions regarding 

fish disposition must be phrased to elicit a response indicating whether descent was successful. 

Application of buffers for uncertainty may be warranted to prevent underestimation of mortality, 

which may have adverse effects on fish stocks over time if additional fishing opportunities are

allowed as a result of decreased mortality estimates. 
50

9. Identifying Components of a National Release Mortality Science Strategy

Although post-release mortality studies have been funded by NMFS since the late 1990s, and 

although such research has expanded outside of NMFS in recent years, post-release mortality 

studies have lacked an overarching strategy or framework. This paper identifies several postrelease mortality science data gaps, and these gaps can serve as components of a national postrelease mortality science strategy.

A national post-release mortality science strategy could include several major components, as 

suggested by scientists and managers who gathered at the September 2013 NMFS release 

mortality workshop. One major component would be to develop baseline discard mortality 

information, including an understanding of underlying factors and their interactions. Managers 

and scientists have difficulty determining whether alternative gear and fishing practices truly 

reduce post-release mortality without a full understanding of how a variety of factors—including 

air exposure, gear type, and temperature—affect different fish species. Gathering baseline data 

related to post-release mortality for different fish species could be labor-intensive in the short

term, but it could create long-term research efficiencies and more effective solutions.

Measuring post-release mortality in fishery conditions, as opposed to laboratory conditions, 

could be another major component of a national post-release science strategy. Conducting such 

research in the field can present logistical challenges and can be expensive, but field research can 

also reduce bias and account for important fishery factors such as post-release predation.

Developing reliable and robust proxies for short- and long-term post-release mortality could be 

another major component. Conducting research on every fish species to develop post-release 

mortality estimates is resource-intensive and inefficient. If scientists and managers focus on 

certain species that are part of a complex or otherwise have similar traits to several other species, 

then limited research resources could have a larger impact.

Because post-release mortality research has been largely uncoordinated in recent years, 

identification of optimal sampling designs for accuracy and precision of post-release mortality 

estimates would be an important component of a national science strategy. As shown in Section 

8.0 of this paper, scientists from the United States and Canada already have a good sense of what 

does and does not work in the area of post-release mortality outreach and research. If scientists 

and managers can reach a consensus on the most effective sampling designs, as well as outreach 

practices, then precision and communication of post-release mortality estimates can be 

optimized.

Any national post-release mortality science strategy must involve a communication and outreach 

component, because partnerships with recreational and commercial fishing communities are 

critical to the reduction of post-release mortality. A national science strategy should focus on 

communication of how post-release mortality estimates are created and used, as well as how 

such estimates impact stock assessments and catch limits or quotas. Effective communication 

ultimately could provide managers and scientists with a better understanding of the impacts of 

best practices versus actual practices on post-release mortality.
51

Finally, a national post-release mortality science strategy should focus on a variety of emerging 

technical aspects of post-release mortality, including the collection of a wider range of 

recreational data regarding hook types, capture and release depths, seasonal effects, and discard 

condition. Other technical aspects that could be a component of a national science strategy 

include determination of sub-lethal effects of capture and the effects of repeated capture, as well 

as the collection of more spatially explicit discard data. The expanded use of sensitivity analyses 

in stock assessments also could help identify which post-release mortality rates need to be more 

accurate and precise.

As with any interesting and challenging scientific problem, there is no shortage of data gaps or 

directions for additional research. Although this section identifies some major components of a 

possible national post-release mortality science strategy, Section 6 of this paper includes many 

other data gaps identified by at the September 2013 workshop that could be folded into a national 

strategy.
52

10.0 Conclusion: Next Steps for Addressing Broader Release Mortality Issues

NMFS, through its various research programs and its Recreational Fisheries Initiative, is 

committed to understanding post-release mortality, determining post-release mortality rates, 

developing best fishing practices to reduce those rates, and incorporating those rates into stock 

assessment and other processes that determine fishing quotas for recreational and commercial 

fishers. In addition, NMFS has funded, and continues to fund, research projects (see Section 3.0

and Appendix B) around the United States to examine and reduce post-release mortality rates. 

Results of those projects are incorporated into the stock assessment process in different ways, as 

shown in Sections 4.0 and 5.0.

Although these efforts have been productive and have helped scientists and managers understand 

and identify the importance of post-release mortality—and in some cases resulted in reduced 

post-release mortality estimates—NMFS should consider a more coordinated, national approach 

to post-release mortality science to make the most effective use of limited resources. NMFS 

could allocate resources in a variety of ways, including the use of a matrix approach. Table 1 

presents a simplified way to think about resource allocation by focusing on some of the specific 

high-priority criteria listed in Section 7.0.

Table 1. Matrix for prioritizing release mortality research resources.

Mortality well-studied Mortality not well-studied

Sufficient discard data Low Medium

Insufficient discard data Medium High

Using this approach, species for which there are high-quality mortality studies, and for which 

sufficient discard data are available, would be prioritized lower than species that have not been 

the subject of high-quality mortality studies and that lack sufficient discard data. Using this 

system, high-priority species might require some research to improve fishery discard data before 

focusing on discard mortality studies. On the other hand, if discard data are sufficient, then the 

applied power of mortality estimates would be maximized. Therefore, perhaps release mortality

studies involving species or fisheries with high-resolution discard data should be prioritized.

Moving forward effectively will require the right partners as well. These partners include states 

where post-release mortality issues are important. Partnerships with the eight regional fishery 

management councils and three marine fishery commissions, including their technical staff and 

committees such as scientific and statistical committees and SouthEast Data, Assessment, and 

Review (SEDAR), also will be critical. Other important partners include analytical end-users

(e.g., stock assessment scientists), as well as post-release mortality technical experts with study 

design expertise.

In addition, and perhaps most importantly, partnerships with fishery stakeholders including 

anglers, commercial fishermen, and members of non-governmental organizations—especially 

those involved in science processes—will be critical partners. Finally, outreach and 

communication specialists must be embedded within this endeavor to ensure that solutions to 

post-release mortality challenges are used by those who can make the greatest difference.
53

11.0 References

Albin, D. and K. A. Karpov. 1996. Mortality of lingcod, Ophiodon elongatus, related to capture 

by hook and line. Marine Fisheries Review 60(3):29-34.

Bacheler, N. M., J. A. Buckel, J. E. Hightower, L. M. Paramore, and K. H. Pollock. 2009. A 

combined telemetry-tag return approach to estimate fishing and natural mortality rates of an 

estuarine fish. Canadian Journal of Fisheries and Aquatic Sciences 66:1230-1244.

Barkley, A. S., and S. X. Cadrin. 2012. Discard mortality estimation of yellowtail flounder 

using reflex action mortality predictors. Transactions of the American Fisheries Society 

141(3):638-644.

Collins, M. R., J. C. McGovern, G. Sedberry, H. S. Meister, and R. Pardieck. 1999. Swim 

bladder deflation in black sea bass and vermilion snapper: potential for increasing postrelease 

survival. North American Journal of Fisheries Management 19:828-832.

Grover, A. M., M. S. Mohr, and M. L. Palmer-Zwahlen. 2002. Hook-and-release mortality of 

Chinook salmon from drift mooching with circle hooks: management implications for 

California’s ocean sport fishery. Pages 39-56 in J. A. Lucy and A. L. Studholme, editors. Catch 

and release in marine recreational fisheries. American Fisheries Society, Symposium 30, 

Bethesda, Maryland.

Hannah, R. W., P. S. Rankin, and M. T. O. Blume. 2012. Use of a novel cage system to 

measure postrecompression survival of northeast Pacific rockfish. Marine and Coastal Fisheries 

4(1):46-56.

Heberer, C., S. A. Aalbers, D. Bernal, S. Kohin, B. DiFiore, and C. A. Sepulveda. 2010. 

Insights into catch-and-release survivorship and stress-induced blood biochemistry of common 

thresher sharks (Alopias vulpinus) captured in the southern California recreational fishery. 

Fisheries Research 106:495-500.

Heuter, R. E., C. A. Manire, J. P. Tyminski, J. M. Hoenig, and D. A. Hepworth. 2006. 

Assessing mortality of released or discarded fish using a logistic model of relative survival 

derived from tagging data. Transactions of the American Fisheries Society 135:500-508

Hochhalter, S. J. and D. J. Reed. 2011. The effectiveness of deepwater release at improving the 

survival of discarded yelloweye rockfish. North American Journal of Fisheries Management 

31(5):852-860.

ICES (International Council for the Exploration of the Sea). 2014. Report of the workshop on 

methods for estimating discard survival (WKMEDS), 17-21 February 2014, ICES HQ, 

Copenhagen, Denmark. ICES CM 2014/ACOM:51. 114 pp.
54

Jarvis, E. T., and C. G. Lowe. 2008. The effects of barotrauma on the catch-and-release survival 

of southern California nearshore and shelf rockfish (Scorpaenidae, Sebastes spp.). Canadian 

Journal of Fisheries and Aquatic Sciences 65:1286-1296. 

Kerns, J. A., M. S. Allen, and J. E. Harris. 2012. Importance of assessing population-impact of 

catch-and-release mortality. Fisheries 37:11:502-503.

Nguyen, V. M., M. A. Rudd, S. G. Hinch, and S. J. Cooke. 2012. Differences in information 

use and preferences among recreational salmon anglers: implications for management initiatives 

to promote responsible fishing. Human Dimensions of Wildlife 17:248-256.

Parker, S. J., H. I. McElderry, P. S. Rankin, and R.W. Hannah. 2006. Buoyancy

regulation and barotrauma in two species of nearshore rockfish. Transactions

of the American Fisheries Society 135:1213–1223.

Patrick, W. S., P. Spencer, O. Ormseth, J. Cope, J. Field, D. Kobayashi, T. Gedamke, E. Cortés,

K. Bigelow, W. Overholtz, J. Link, and P. Lawson. 2009. Use of productivity and susceptibility

indices to determine stock vulnerability, with example applications to six U.S. fisheries. U.S.

Department of Commerce, NOAA Technical Memorandum NMFS-F/SPO-101, 90 p.

PFMC (Pacific Fishery Management Council). 2008. Final environmental impact statement for 

the proposed acceptable biological catch and optimum yield specifications and management 

measures for the 2009-2010 Pacific Coast groundfish fishery. Pacific Fishery Management 

Council, Portland, OR, Chapter 4: 276-290. http://www.pcouncil.org/wpcontent/uploads/chp4_0910.pdf

PFMC (Pacific Fishery Management Council). 2012. Groundfish Management Team progress 

report on developing mortality rates for rockfish released using descending devices. Pacific 

Fishery Management Council, Portland, OR. November Council Meeting, Agenda Item I.3. 

http://www.pcouncil.org/wp-content/uploads/I3b_GMT_NOV2012BB.pdf

PFMC (Pacific Fishery Management Council). 2013. Groundfish Management Team report on 

proposed discard mortality for cowcod, canary rockfish, and yelloweye rockfish released using 

descending devices in the recreational fishery. Pacific Fishery Management Council, Portland, 

OR. April Council Meeting, Agenda Item D.5, http://www.pcouncil.org/wpcontent/uploads/D5b_GMT_APR2013BB.pdf

PFMC (Pacific Fishery Management Council). 2014. Groundfish Management Team report on 

proposed discard mortality for cowcod, canary rockfish, and yelloweye rockfish released using 

descending devices in the recreational fishery. Pacific Fishery Management Council, Portland, 

OR. March Council Meeting, Agenda Item D.3, http://www.pcouncil.org/wpcontent/uploads/D3b_SUP_GMT_RPT2_MAR2014BB.pdf

Pollock, K. H., and W. E. Pine III. 2007. The design and analysis of field studies to estimate 

catch-and-release mortality. Fisheries Management and Ecology 14:123-130.
55

Pribyl, A. L., C. B. Schreck, M. L. Kent, M. Kelley, and S. J. Parker. 2012. Recovery potential of 

black rockfish, Sebastes melanops Girard, recompressed following barotrauma. Journal of Fish 

Diseases 35(4):275-286.

Rogers, B. L., C. G. Lowe, and E. Ferńandez-Juricic. 2011. Recovery of visual performance in 

rosy rockfish (Sebastes rosaceus) following exophthalmia resulting from barotrauma. Fisheries 

Research 112(1-2):1-7. 

Romine, J. G., J. A. Musick, and G. H. Burgess. 2009. Demographic analyses of the dusky 

shark, Carcharinus obscurus, in the Northwest Atlantic incorporating hooking mortality 

estimates and revised reproductive parameters. Environmental Biology of Fishes 84:277-289.

Rudershausen, P. J., J. A. Buckel, and J. E. Hightower. 2014. Estimating reef fish discard 

mortality using surface and bottom tagging: effects of hook injury and barotrauma. Canadian 

Journal of Fisheries and Aquatic Sciences 71(4):514-520.

Smiley, J. E. and M. Drawbridge. 2007. Techniques for live capture of deepwater fishes with 

special emphasis on the design and application of a low-cost hyperbaric chamber. Journal of Fish 

Biology 70:867-878. 

STT (Salmon Technical Team). 2000. STT recommendations for hooking mortality rates in 2000 

recreational ocean Chinook and coho fisheries. March supplemental report B2. Pacific Fishery 

Management Council, 7700 NE Ambassador Place, Suite 101, Portland, Oregon.
56

Appendix A. Release Mortality Workshop Attendees (September 25-26, 2013)

Attendee Affiliation

Leif Anderson NMFS Northwest Fisheries Science Center

Lee Benaka NMFS Office of Science and Technology

Hugues Benoit Fisheries and Oceans Canada

Ken Brennan NMFS Southeast Fisheries Science Center

Jeff Buckel North Carolina State University

John Budrick California Department of Fish and Wildlife

Patrick Campfield Atlantic States Marine Fisheries Commission

Paul Caruso Massachusetts Division of Marine Fisheries

Chip Collier North Carolina Department of Environment and Natural Resources

Steven Cooke Carleton University, Ontario, Canada

Andy Danylchuk University of Massachusetts Amherst

Robert Hannah Oregon Department of Fish and Wildlife

Erica Jarvis Orange County (California) Sanitation District

Chris Lunsford NMFS Alaska Fisheries Science Center

John Mandelman New England Aquarium

Earl Meredith NMFS Northeast Fisheries Science Center

Michael Mohr NMFS Southwest Fisheries Science Center

Michael Palmer NMFS Northeast Fisheries Science Center

Terrance Quinn University of Alaska Fairbanks

Danielle Rioux NMFS Office of Sustainable Fisheries

Paul Rudershausen North Carolina State University

Beverly Sauls Florida Fish and Wildlife Commission

Leah Sharpe NMFS Office of Science and Technology

Greg Stunz Harte Research Institute at Texas A&M University-Corpus Christi

Charles Villafana NMFS West Coast Regional Office

Gregg Williams International Pacific Halibut Commission

Dan Wolford Coastside Fishing Club
57

Appendix B. Summary of NMFS-Funded Release Mortality Research by Region (NE = 

Northeast, SE = Southeast, WC = West Coast, AK = Alaska, PI = Pacific Islands

Region Year Recipient Title Funding 

($)

Funding 

Source*

Complete 

or 

Ongoing?

Target 

Species

Results

NE 2013 Farleigh 

Dickinson 

University

Optimization of Gear Size 

and Post-Release Mortality 

Reduction in the New 

Jersey Summer Flounder 

Hook-and-Line Fishery

122,911 BREP Ongoing Summer 

flounder

NE 2012 New England 

Aquarium 

Corporation

Elucidating Post-Release 

Mortality and “Best 

Capture and Handling” 

Methods in Sublegal 

Atlantic Cod Discarded in 

Gulf of Maine Recreational 

Hook-and-Line Fisheries

248,659 BREP Ongoing Atlantic cod

NE 2012 VA Institute 

of Marine 

Science

Evaluating the Condition 

and Discard Mortality of 

Skates Following Capture 

and Handling in the Sea 

Scallop Dredge Fishery

1,092,642 Scallop 

RSA

Ongoing Skates

NE 2009 University of 

MA, 

Dartmouth

Post-Release Survivability 

of Longline-Caught Large 

Coastal Sharks

362,294 S-K Ongoing Sandbar 

sharks, 

dusky sharks

NE 2008 New England 

Aquarium 

Corporation

The Immediate and ShortTerm Post-Release 

Mortality of Species in the 

Northwest Atlantic Skate 

Complex Captured by 

Gillnet and Otter Trawl

222,618 S-K Ongoing Skates

NE 2011 Coonamessett 

Farm

Optimizing the Georges 

Bank Scallop Fishery by 

Maximizing Meat Yield 

and Minimizing Bycatch

1,847,700

***

NE CRP Complete Yellowtail, 

winter 

flounder

Investigators 

concluded an 

assumed discard 

mortality rate of 

90% for the 

southern NE/MidAtlantic 

yellowtail 

flounder stock 

assessment; 

confirmed that a 

discard mortality 

estimate of 50% 

for winter 

flounder may be 

accurate for the 

scallop fishery. 
58

Region Year Recipient Title Funding 

($)

Funding 

Source*

Complete 

or 

Ongoing?

Target 

Species

Results

NE 2009 Cornell 

Cooperative 

Extension

Evaluation of Summer 

Flounder Discard Mortality 

in the Bottom Trawl 

Fishery, Part II: A Study of 

the Offshore Winter 

Fishery

376,650 MidAtlantic 

RSA

Complete Summer 

flounder

Overall median 

discard mortality 

was calculated to 

be 98%, much 

higher than the 

80% rate used in 

the stock 

assessment at the 

time. Overall 

mean discard 

mortality rate was 

calculate to be 

80.4%, nearly 

identical to the 

rate used for stock 

assessments.

NE 2008 National 

Fisheries 

Institute

Discard Mortality in the 

Summer Flounder Fishery: 

A New Approach to 

Evaluation

148,719 MidAtlantic 

RSA

Complete Summer 

flounder

Project’s discard 

mortality 

estimate, 

combining ondeck and latent 

mortality, was 

82.7%

NE 2008 University of 

MA, 

Dartmouth

Discard Mortality 

Estimation of the Southern 

New England Flatfish 

Complex using Reflex 

Action Mortality Predictor 

(RAMP) Methods

75,529 NE CRP Complete Yellowtail, 

winter, 

windowpane 

flounder

A paper based on 

this research 

applied RAMP 

methods to 

demonstrate a 42-

73% range of 

yellowtail 

flounder discard 

mortality 

estimates from the 

southern New 

England trawl 

fishery.

NE 2007 Cornell 

Cooperative 

Extension

Summer Flounder Discard 

Mortality in the Inshore 

Bottom Trawl Fishery

284,800 MidAtlantic 

RSA

Complete Summer 

flounder

Mean discard 

mortality was 

64.6%; median 

mortality rate was 

78.7%. Tow time 

and cull time were 

important factors.

NE 2006 University of 

New England

The Design, Development, 

and Field Testing of an 

Innovative Circular Net 

Pen to be Used to Assess 

Bycatch Mortality of 

Atlantic Cod at Sea

$25,000 NE CRP Complete Atlantic cod
59

Region Year Recipient Title Funding 

($)

Funding 

Source*

Complete 

or 

Ongoing?

Target 

Species

Results

NE 2005 Gulf of 

Maine 

Research 

Institute

Industry-Science 

Partnership Investigating 

the Short-Term and LongTerm Discard Mortality of 

Spiny Dogfish Using Hook 

Gear in Gulf of Maine 

Waters

78,807 NE CRP Complete Spiny 

dogfish

Gear effects were 

found, with 

highest mortality 

resulting from 

longline gear 

(22%), while 

different hand 

gear mortality 

ranged from 8 to 

17%.

NE 2004 New England 

Aquarium 

Corporation

Increasing Survival of 

Juvenile Atlantic Cod and 

Haddock in the Northwest 

Atlantic Demersal 

Longline Fishery

163,244 S-K Complete Atlantic cod, 

haddock

NE 2004 New England 

Aquarium 

Corporation

Increasing Juvenile Cod 

Bycatch Survival in a 

Northwest Atlantic 

Longline Fishery

99,457 S-K Complete Atlantic cod

NE 2004 New England 

Aquarium 

Corporation

Selectivity and Survival of 

Atlantic Cod and Haddock 

in a Northwest Atlantic 

Longline Fishery

200,000 S-K Complete Atlantic cod, 

haddock

NE 2003 New England 

Aquarium 

Corporation

Juvenile Bycatch and 

Survival Assessment of 

Spiny Dogfish in a 

Western Atlantic Trawl 

Fishery

169,580 S-K Complete Spiny 

dogfish

Less than 50% 

mortality 

following trawl 

capture in the 

wild.

SE 2013 FL Fish and 

Wildlife 

Conservation 

Commission

Testing an Alternative 

Method for the Safe 

Release of Reef Fishes 

Caught on Hook-and-Line 

Gear in the Recreational 

Fishery in the Gulf of 

Mexico

185,843 BREP Ongoing Reef fish

SE 2013 FL Fish and 

Wildlife 

Conservation 

Commission

Evaluation of the Effects of 

Recreational Catch-andRelease Angling on the 

Survival of Gag Grouper

113,749 MARFIN Ongoing Gag grouper

SE 2013 Mote Marine 

Laboratory

Discard Mortality of 

Carcharhinid Sharks in the 

Florida Commercial Shark 

Fishery

235,847 SE CRP Ongoing Atlantic 

sharks

SE 2012 University of 

FL

To Vent or Descend? 

Evaluating Seasonal 

Release Mortality of Gag 

and Red Grouper in 

Recreational Fisheries of 

the Eastern Gulf of Mexico

113,537 MARFIN Ongoing Gag 

grouper, red 

grouper
60

Region Year Recipient Title Funding 

($)

Funding 

Source*

Complete 

or 

Ongoing?

Target 

Species

Results

SE 2012 University of 

South 

Alabama

Examining Hook 

Selectivity in the Northern 

Gulf of Mexico 

Recreational Reef Fish 

Fishery

202,636 SE CRP Ongoing Reef fish

SE 2010 FL Fish and 

Wildlife 

Conservation 

Commission

An Evaluation of the 

Effects of Catch and 

Release Angling on 

Survival and Behavior of 

Goliath Grouper

100,000 MARFIN Ongoing Goliath 

grouper

SE 2011 Mote Marine 

Laboratory

Fine-Scale Behavior and 

Mortality in Post-Release 

Carcharhinid Sharks in the 

Florida Recreational Shark 

Fishery

192,325 SE CRP Complete Blacktip 

sharks

Mortalities (N=3, 

9.7%) all took 

place within 2 h 

after release and 

were indicated by 

static depth data 

and the cessation 

of tail beat

activity.

SE 2011 NMFS 

SEFSC

Examining the Efficiency 

of Modified Circle Hooks 

in Reducing the Bycatch of 

Undersized Lutjanid and 

Serranid Fishes

37,000 BREP Complete Snappers, 

groupers

SE 2010 Texas A&M 

University—

Corpus 

Christi

Evaluating the Effect of 

Barotrauma on Regulatory 

Discards in the Red 

Snapper Fishery using 

Advanced Acoustic 

Telemetry and Hyperbaric 

Experimentation

135,000 MARFIN Complete Red snapper

SE 2010 University of 

GA Research 

Foundation

Collaborative Research to 

Quantify and Reduce 

Bycatch Mortality of 

Blacknose Sharks in 

Shrimp Trawls

59,330 SE CRP Complete Blacknose 

sharks

The Big Boy 

turtle excluder 

device with 2” bar 

spacing 

significantly 

reduced shark 

bycatch without 

affecting shrimp 

retention. Data 

indicates that 

blacknose sharks 

do not represent a 

large component 

of total shark 

bycatch in 

Georgia. 
61

Region Year Recipient Title Funding 

($)

Funding 

Source*

Complete 

or 

Ongoing?

Target 

Species

Results

SE 2010 Nova 

Southeastern 

University

Post-Release Survival and 

Habitat Utilization of 

Juvenile Swordfish in the 

Florida Straits Recreational 

Fishery

183,768 SE CRP Complete Atlantic 

swordfish

Limited tagging 

resulted in an 

estimated release 

mortality rate of 

35.7%.

SE 2010 NMFS 

SEFSC

Determination of Alternate 

Fishing Practices to 

Reduce Mortality of 

Prohibited Dusky Shark in 

Commercial Longline 

Fisheries

39,357 BREP Complete Dusky shark 90% mortality 

after 15 hours onhook.

SE 2009 Patzig Marine 

Services, Inc.

Discard Mortality of Red 

Snapper in the 

Northeastern Gulf of 

Mexico Recreational 

Fishery

148,150 MARFIN Complete Red snapper 14% mortality 

rate.

SE 2009 University of 

FL

Release Mortality of Gulf 

of Mexico Greater 

Amberjack from 

Commercial and 

Recreational Hand-Line 

Fisheries

244,867 MARFIN Complete Greater 

amberjack

This project 

indicated a high 

acute survival rate 

for greater 

amberjack for 

some 

handline fisheries, 

and initially depth 

of capture and 

decompression do 

not appear to be a 

major factors in 

release or discard 

mortality. 

SE 2009 University of 

West FL

Minimizing Discards in the 

Gulf of Mexico 

Recreational Red Snapper 

Fishery: Hook Selectivity 

and the Efficacy of a First 

Fish Rule

268,545 SE CRP Complete Red snapper

SE 2009 FL Fish and 

Wildlife 

Commission

Survival of Discarded Reef 

Fish Species in the 

Recreational Fishery using 

At-Sea Observer Surveys 

and Mark –Recapture 

Methods off the Florida 

Coast in the Gulf of 

Mexico

185,427 SE CRP Complete Reef fish
62

Region Year Recipient Title Funding 

($)

Funding 

Source*

Complete 

or 

Ongoing?

Target 

Species

Results

SE 2009 FL Fish and 

Wildlife 

Conservation 

Commission

Characterization of 

Recreational Discard 

Composition and Mortality 

Rates for Gray Snapper 

and Other EstuarineDependent Reef Fishes 

within a Gulf Coast 

Estuary and Nearshore 

Florida Waters

222,495 SE CRP Complete Gray 

snapper

Overall mortality 

rate of 6.9% 

estimated for gray 

snapper; overall 

mortality rate of 

7.2% estimated 

for gag.

SE 2009 FL Fish and 

Wildlife 

Conservation 

Commission

A Directed Study of the 

Recreational Red Snapper 

Fisheries in the Gulf of 

Mexico along the West 

Florida Shelf

999,000 SE CRP Complete Red snapper Red snapper may 

particularly 

benefit from 

larger reductions 

in discard 

mortality through 

the use of circle 

hooks; fish that 

can re-submerge 

on their own have 

a higher rate of 

survival if they 

are not vented, but 

may benefit from 

venting when it 

helps them resubmerge.

SE 2007 TX Tech 

University

Reducing Discard 

Mortality in Red Snapper 

Recreational Fisheries 

using Descender Hooks 

and Rapid Recompression

262,369 SE CRP Complete Red snapper

SE 2005 FL Fish and 

Wildlife 

Conservation 

Commission

Size and Age Structure and 

Catch and Release 

Mortality Estimates of 

Sub-Adult and Adult Red 

Drum in the Tampa Bay

132,059 MARFIN Complete Red drum 5.6% mortality 

rate (compared to 

5% used in 2009 

FL red drum 

assessment).

SE 2005 Patzig Marine 

Services, Inc.

Cooperative Hook and 

Line Discard Mortality 

Study of Vermillion 

Snapper in the 

Northeastern Gulf of 

Mexico Commercial 

Fishery

114,072 SE CRP Complete Vermillion 

snapper

34% mortality 

rate within ~3 

hours.

SE 2005 University of 

Florida

The Capture Depth, Time, 

and Hooked Survival Rate 

for Bottom LonglineCaught Large Coastal 

Sharks

144,264 SE CRP Complete Nurse, 

sandbar, 

blacktip, and 

Atlantic 

sharpnose 

sharks
63

Region Year Recipient Title Funding 

($)

Funding 

Source*

Complete 

or 

Ongoing?

Target 

Species

Results

SE 2004 TX Tech 

University

Decompression and 

Delayed Mortality: Effects 

of Barotrauma on Red 

Snapper

100,184 MARFIN Complete Red snapper

SE 2003 SC 

Department 

of Marine 

Resources

Estimates of Catch-andRelease Mortality for Red 

Drum in the Recreational 

Fishery of South Carolina

90,000 SE CRP Complete Red drum

SE 1999 SC 

Department 

of Marine 

Resources

Removing Gas from the 

Distended Swim Bladder 

of Reef Fish: Does It 

Really Increase PostRelease Survival?

38,196 S-K Complete Reef fish 100% of 223 

fishes deflated 

with a needle 

survived over first 

24 hours after 

release, compared 

to 61% survival 

rate for controls.

WC 2013 University of 

CA, San 

Diego

Examining Environmental 

Effects of Rockfish Catchand-Release Survival: 

Does Low Oxygen 

Contribute to Mortality 

Following Barotrauma?

183,997 BREP Ongoing Rockfish

WC 2012 Oregon State 

University

Field Validation of the 

RAMP Approach for 

Determining Crab Bycatch 

Mortality

68,289 BREP Ongoing Dungeness 

crab

WC 2011 NMFS 

SWFSC

Ability of Southern 

California Deepwater 

Rockfish to Survive 

Barotrauma Following insitu Recompression

104,290 BREP Complete Pacific 

rockfish

90% of bocaccio, 

and 100% of 

cowcod, survived 

long-term. 93% 

of 5 different 

species survived 

in the short-term 

(up to 2 days)

WC 2008-

2011

NMFS 

SWFSC and 

SWRO

Reducing Post-Release 

Mortality for Common 

Thresher Sharks Captured 

in the Southern California 

Recreational Fishery

229,265 BREP Complete Thresher 

shark

26% mortality 

rate.

WC 2009 NMFS 

SWFSC

Incidental Take and PostRelease Mortality of Blue 

Sharks in the U.S. West 

Coast Drift Gillnet and 

Longline Fisheries for 

Swordfish

46,615 BREP Complete Blue shark

WC 2008 Oregon State 

University

The Effects of 

Decompression and the 

Efficacy of Recompression 

as a Bycatch Mortality 

Reduction Tool for 

Rockfish

61,374 S-K Complete Rockfish
64

Region Year Recipient Title Funding 

($)

Funding 

Source*

Complete 

or 

Ongoing?

Target 

Species

Results

WC 1996 CA 

Department 

of Fish and 

Wildlife

Post-Release Mortality in 

the Central California

Ocean Recreational 

Salmon Fisheries

40,000 NMFS 

Southwest 

Regional 

Office

Complete Chinook 

salmon

4% mortality rate 

for maxillaryhooked fish and 

84% for guthooked fish; 42% 

mortality rate for 

drift-mooch 

caught-andreleased fish; 14% 

mortality rate for 

troll-caught fish. 

Overall mortality 

rate for CA 

salmon fisheries 

of 20-25%.

WC 2002 Pfleger 

Institute of 

Environmenta

l Research

A Device for Greatly 

Reducing Fishing 

Mortality for Protected 

Giant Seabass and Jewfish 

19,211 S-K Complete California 

giant sea 

bass and 

goliath 

grouper

AK 2013 AK Charter 

Association

Use of Digital Imaging 

Technology to Reduce 

Released Halibut Mortality 

in Alaska’s Recreational 

Fishery

186,725 BREP Ongoing Halibut

AK 2009 NMFS AFSC Mortality Rates for Crab 

Bycatch in Trawls

159,642** BREP Complete Red king 

crab

Estimates of crab 

mortality rates 

after trawl 

encounters were 

generated for all 

major Bering Sea 

crab species.

AK 2000 AK Fisheries 

Development 

Foundation

Trawl Codend Mesh Size 

and Shape Investigations to 

Reduce Catch and Discard 

of Undersized Pollock

675,000 S-K Complete Pollock 14-day mortality 

caused by 

escapement and 

the 

caging/holding 

processes ranged 

from 46-84% for 

pollock that 

escaped through 

codend meshes 

and 47-63% for 

fish that escaped 

through 

intermediate 

meshes.

AK 1998 AK Fisheries 

Development 

Foundation

Practical Application of 

Fishing and Handling 

Techniques in Estimating 

the Mortality of Discarded 

Trawl-Caught Halibut

154,452 S-K Complete Halibut
65

Region Year Recipient Title Funding 

($)

Funding 

Source*

Complete 

or 

Ongoing?

Target 

Species

Results

PI 2010-

2012

NMFS PIFSC 

and Queen’s 

University 

(Ontario, 

Canada)

Estimating Post-Release 

Mortality in Istiophorid 

Billfish

385,039 BREP Ongoing Pacific blue 

marlin, 

Pacific 

striped 

marlin

*BREP = Bycatch Reduction Engineering Program; S-K = Saltonstall-Kennedy Grant Program; RSA = Research 

Set-Aside Program; CRP = Cooperative Research Program; MARFIN = Marine Fisheries Initiative

**Only a portion of the indicated funding was used for release mortality research.

***BREP funding constitutes a small portion of overall project funding; additional funds came from other NMFS 

sources.
66

Appendix C. Compilation of Release Mortality Estimates Used by NMFS

* = different estimates used by different 

regions

Region Species Type of Estimate Used Data supporting the estimate Estimates Citations

New England

Cod (Gulf of 

Maine)

multiple estimates based 

on type of fishery unclear

Large-mesh otter 

trawl: 75%; Smallmesh otter trawl: 

75%; Large-mesh 

gillnet: 80%;

Extra-large-mesh 

gillnet: 80%; 

Longline: 33%; 

Shrimp trawl: 75%; 

Recreational: 30% none

New England

Cod (Georges 

Bank)

multiple estimates based 

on type of fishery unclear

Large-mesh otter 

trawl: 75%; Smallmesh otter trawl: 

75%; Large-mesh 

gillnet: 80%; 

Longline: 33%; 

Scallop dredge: 

100%; 

Recreational: 30% none

New England

Haddock (Gulf 

of Maine)

multiple estimates based 

on type of fishery unclear

Commercial gear: 

100%; 

Recreational: 0% none

New England

Haddock 

(Georges Bank)

assumption of 100% 

mortality unclear none

New England

Winter Flounder 

(Georges Bank)

assumption of 100% 

mortality unclear none

New England

Winter Flounder 

(Southern New 

England)

multiple estimates based 

on type of fishery single study

Large-mesh otter 

trawl: 50%; 

Scallop dredge: 

50%; Recreational: 

15%

Durso and Iswanowicz 

1983

New England

Winter Flounder 

(Gulf of Maine)

assumption of 100% 

mortality unclear none
67

* = different estimates used by different 

regions

Region Species Type of Estimate Used Data supporting the estimate Estimates Citations

New England

Yellowtail 

Flounder 

(Georges Bank)

assumption of 100% 

mortality unclear none

New England

Yellowtail 

Flounder 

(Southern New 

England)

assumption of 90% 

mortality unclear none

New England

Windowpane 

Flounder 

(northern and 

southern)

assumption of 100% 

mortality unclear none

New England Pollock

assumption of 100% 

mortality

single study plus precautionary 

principle 100% Clay et al. 1989

New England American Plaice

assumption of 100% 

mortality unclear none

New England Witch Flounder

assumption of 100% 

mortality unclear none

New England Atlantic Halibut

assumption of 100% 

mortality unclear none

New England White hake

assumption of 100% 

mortality unclear none

New England Redfish

assumption of 100%

mortality unclear none

New England Ocean pout

assumption of 100% 

mortality unclear none

Mid Atlantic

Summer 

Flounder one estimate multiple studies 10%

Lucy and Holton 

1998, Malchoff and 

Lucy 1998, Malchoff 

et al. 2001

Mid Atlantic Black Sea Bass* one estimate single study plus Delphi analysis 25%

Bugley and Shepherd 

1991

Mid Atlantic Scup one estimate

single study plus additional 

unpublished work 15%

Howell and Simpson 

1985, Terceiro 2011
68

* = different estimates used by different 

regions

Region Species Type of Estimate Used Data supporting the estimate Estimates Citations

Mid Atlantic Bluefish one estimate

single study modified by a Council 

technical committee 15% Malchoff 1995

Mid Atlantic Spiny Dogfish one estimate unclear 25% none

South Atlantic Black Sea Bass* one estimate multiple studies 15%

Low 1981, Vaughn et 

al. 1995, Collins et al. 

1999

South Atlantic Red Snapper*

multiple estimates based 

on type of fishery multiple studies

Private 

recreational: 39%, 

For-hire 

recreational: 41%, 

Commercial: 48% Burns et al. 2004

South Atlantic

Vermillion 

Snapper* one estimate unpublished data 25% none

South Atlantic Mutton Snapper one estimate studies on other species 15% none

South Atlantic Goliath Grouper

incorporated into the 

overall model unclear n/a none

South Atlantic Red Grouper* one estimate

multiple studies (one of which is the 

same one used for the Gulf of 

Mexico estimate) 20% none

South Atlantic Black Grouper one estimate unclear 20% none

South Atlantic Gag Grouper* one estimate multiple studies 25%

Wilson and Burns 

1996, Burns et al. 

2002, Overton and 

Zabawski 2003, 

McGovern et al. 2005, 

Rudershausen et al. 

2005

South Atlantic Red Drum* one estimate

multiple studies plus sensitivity 

analysis 8%

Aguilar et al. 2002, 

Gearhart 2002, 

Murphy 2005, 

Vecchio and Warner 

2007
69

* = different estimates used by different 

regions

Region Species Type of Estimate Used Data supporting the estimate Estimates Citations

South Atlantic

Spanish 

Mackerel none insufficient data 100% none

South Atlantic King Mackerel

multiple estimates based 

on type of fishery single study plus observer data

Headboat fishery: 

33%; Recreational 

fishery: 20% Edwards 1996

South Atlantic

Greater 

Amberjack one estimate

anecdotal information and sensitivity 

analyses 20% none

South Atlantic Red Porgy one estimate single study 8% Collins 1996

Atlantic coast Striped Bass one estimate multiple studies 8%

Diodati and Richards 

1996

Atlantic coast Red Drum* one estimate single study 5% Murphy 2005

Atlantic coast Tautog one estimate single study 2.50%

Simpson and Gates 

1999

Atlantic coast Weakfish one estimate multiple studies 10%

Murphy et al. 1995, 

Malchoff and Heins 

1997, Swihart et al. 

2000, Gearhart 2002

Atlantic coast

Atlantic 

Croaker one estimate unclear 10% none

Gulf of Mexico Red Snapper*

multiple estimates 

varying by geographic 

region and depth multiple studies

East of the 

Mississippi/20-

40m: 15%, West of 

the 

Mississippi/40m: 

40%

personal 

communication

Gulf of Mexico

Vermilion 

Snapper*

multiple estimates based 

on type of fishery

anecdotal information and sensitivity 

analyses

Private 

recreational: 10-

40%, Headboat: 

40-60%, 

Commercial handline: 40-75% none
70

* = different estimates used by different 

regions

Region Species Type of Estimate Used Data supporting the estimate Estimates Citations

Gulf of Mexico Gag Grouper*

multiple estimates 

varying by geographic 

region and depth multiple studies

Panhandle/10m: 

11%, 

Panhandle/20m: 

18%, 

Panhandle/40m: 

42%, Peninsula & 

Keys/10m: 11%, 

Peninsula & 

Keys/30m: 29%

personal 

communication

Gulf of Mexico Red Grouper* one estimate single study 10%

Wilson and Burns 

1996

Gulf of Mexico

Greater 

Amberjack one estimate

anecdotal information and sensitivity 

analyses 20% none

West Coast Black Rockfish

multiple estimates 

varying by depth; sectors 

include recreational, rod 

and reel commercial 

nearshore

multiple sources of data are 

combined: 1) observed data and/or a 

guild-based model to estimate 

surface mortality; 2) single study to 

estimate short-term, below-surface 

mortality; 3) expert opinion to 

estimate long-term, delayed 

mortality

0-10 fm: 11%; 11-

20 fm: 20%, 21-30 

fm: 29%, >30 fm: 

63%

Albin and Karpov 

1996, PFMC 2008, 

Hannah et al. 2012

West Coast

Black and 

Yellow 

Rockfish

multiple estimates 

varying by depth; sectors 

include recreational, rod 

and reel commercial 

nearshore

multiple sources of data are 

combined: 1) observed data and/or a 

guild-based model to estimate 

surface mortality; 2) single study to 

estimate short-term, below-surface 

mortality; 3) expert opinion to 

estimate long-term, delayed 

mortality

0-10 fm: 13%; 11-

20 fm: 24%, 21-30 

fm: 37%, >30 fm: 

100%

Albin and Karpov 

1996, PFMC 2008, 

Hannah et al. 2012

West Coast Blue Rockfish

multiple estimates 

varying by depth; sectors 

include recreational, rod 

and reel commercial 

nearshore

multiple sources of data are 

combined: 1) observed data and/or a 

guild-based model to estimate 

surface mortality; 2) single study to 

estimate short-term, below-surface 

mortality; 3) expert opinion to 

estimate long-term, delayed 

mortality

0-10 fm: 18%; 11-

20 fm: 30%, 21-30 

fm: 43%, >30 fm: 

100%

Albin and Karpov 

1996, PFMC 2008, 

Hannah et al. 2012
71

* = different estimates used by different 

regions

Region Species Type of Estimate Used Data supporting the estimate Estimates Citations

West Coast Bocaccio

multiple estimates 

varying by depth; sectors 

include recreational, rod 

and reel commercial 

nearshore

multiple sources of data are 

combined: 1) observed data and/or a 

guild-based model to estimate 

surface mortality; 2) single study to 

estimate short-term, below-surface 

mortality; 3) expert opinion to 

estimate long-term, delayed 

mortality

0-10 fm: 19%; 11-

20 fm: 32%, 21-30 

fm: 46%, >30 fm: 

100%

Albin and Karpov 

1996, PFMC 2008, 

Hannah et al. 2012

West Coast Brown Rockfish

multiple estimates 

varying by depth; sectors 

include recreational, rod 

and reel commercial 

nearshore

multiple sources of data are 

combined: 1) observed data and/or a 

guild-based model to estimate 

surface mortality; 2) single study to 

estimate short-term, below-surface 

mortality; 3) expert opinion to 

estimate long-term, delayed 

mortality

0-10 fm: 12%; 11-

20 fm: 22%, 21-30 

fm: 33%, >30 fm: 

100%

Albin and Karpov 

1996, PFMC 2008, 

Hannah et al. 2012

West Coast Calico Rockfish

multiple estimates 

varying by depth; sectors 

include recreational, rod 

and reel commercial 

nearshore

multiple sources of data are 

combined: 1) observed data and/or a 

guild-based model to estimate 

surface mortality; 2) single study to 

estimate short-term, below-surface 

mortality; 3) expert opinion to 

estimate long-term, delayed 

mortality

0-10 fm: 24%; 11-

20 fm: 43%, 21-30 

fm: 60%, >30 fm: 

100%

Albin and Karpov 

1996, PFMC 2008, 

Hannah et al. 2012

West Coast

Canary 

Rockfish

surface release: multiple 

estimates varying by 

depth; release with 

descending device: 

multiple estimates 

varying by depth; sectors 

include recreational, rod 

and reel commercial 

nearshore

Surface release: multiple sources of 

data are combined: 1) observed 

discard data and GLM model to 

estimate surface mortality with 

depth; 2) single study to estimate 

short-term, below-surface mortality; 

3) expert opinion to estimate longterm, delayed mortality; Release with 

descending device: 1) 90% upper 

confidence interval estimate of shortterm mortality estimates from cage 

studies, 2) long-term mortality 

estimates from an acoustic tagging 

study of descended fish.

Surface release: 0-

10 fm: 21%; 11-20 

fm: 37%, 21-30 

fm: 53%, >30 fm: 

100%; Release 

with descending 

device: 0-10 fm: 

21%, 10-30 fm: 

25%, 30-50 fm: 

48%, 50-100 fm: 

57%, >100 fm: 

100%

surface release: Albin 

and Karpov 1996; 

PFMC 2008; release 

with descending 

device: Jarvis and 

Lowe 2008, Hannah et 

al. 2012, Wegner et al. 

unpublished raw data, 

PFMC 2012, PFMC 

2013, PFMC 2014
72

* = different estimates used by different 

regions

Region Species Type of Estimate Used Data supporting the estimate Estimates Citations

West Coast China Rockfish

multiple estimates 

varying by depth; sectors 

include recreational, rod 

and reel commercial 

nearshore

multiple sources of data are 

combined: 1) observed data and/or a 

guild-based model to estimate 

surface mortality; 2) single study to 

estimate short-term, below-surface 

mortality; 3) expert opinion to 

estimate long-term, delayed 

mortality

0-10 fm: 13%; 11-

20 fm: 24%, 21-30 

fm: 37%, >30 fm: 

100%

Albin and Karpov 

1996, PFMC 2008, 

Hannah et al. 2012

West Coast

Copper 

Rockfish

multiple estimates 

varying by depth; sectors 

include recreational, rod 

and reel commercial 

nearshore

multiple sources of data are 

combined: 1) observed data and/or a 

guild-based model to estimate 

surface mortality; 2) single study to 

estimate short-term, below-surface 

mortality; 3) expert opinion to 

estimate long-term, delayed 

mortality

0-10 fm: 19%; 11-

20 fm: 33%, 21-30 

fm: 48%, >30 fm: 

100%

Albin and Karpov 

1996, PFMC 2008, 

Hannah et al. 2012

West Coast Cowcod

surface release: multiple 

estimates varying by 

depth; Release with 

descending device:

multiple estimates 

varying by depth; sectors 

include recreational, rod 

and reel commercial 

nearshore

Surface release: multiple sources of 

data are combined: 1) observed 

discard data from deep demersal 

guild proxy species and GLM model 

to estimate surface mortality with 

depth 2) single study to estimate 

short-term, below-surface mortality; 

3) expert opinion to estimate longterm, delayed mortality; Release with 

descending device: 1) 90% upper 

confidence interval estimate of shortterm mortality estimates from cage 

studies, 2) long-term mortality 

estimates from an acoustic tagging 

study of descended fish.

Surface release: 0-

10 fm: 21%, 11-20 

fm: 35% , 21-30 

fm: 52%, >30 fm: 

100%; Release 

with descending 

device: 0-10 fm: 

21%, 10-20 fm: 

35%, 20-30 fm: 

52% , 30-50 fm: 

57% , 50-100: 

57%, >100 fm: 

100%

surface release: Albin 

and Karpov 1996, 

PFMC 2008; release 

with descending 

device: Jarvis and 

Lowe 2008, Hannah et 

al. 2012, Wegner et al. 

unpublished raw data, 

PFMC 2012, PFMC 

2013, PFMC 2014

West Coast

Gopher 

Rockfish

multiple estimates 

varying by depth; sectors 

include recreational, rod 

and reel commercial 

nearshore

multiple sources of data are 

combined: 1) observed data and/or a 

guild-based model to estimate 

surface mortality; 2) single study to 

estimate short-term, below-surface 

mortality; 3) expert opinion to 

estimate long-term, delayed 

mortality

0-10 fm: 19%; 11-

20 fm: 34%, 21-30 

fm: 49%, >30 fm: 

100%

Albin and Karpov 

1996, PFMC 2008, 

Hannah et al. 2012
73

* = different estimates used by different 

regions

Region Species Type of Estimate Used Data supporting the estimate Estimates Citations

West Coast Grass Rockfish

multiple estimates 

varying by depth; sectors 

include recreational, rod 

and reel commercial 

nearshore

multiple sources of data are 

combined: 1) observed data and/or a 

guild-based model to estimate 

surface mortality; 2) single study to 

estimate short-term, below-surface 

mortality; 3) expert opinion to 

estimate long-term, delayed 

mortality

0-10 fm: 23%; 11-

20 fm: 45%, 21-30 

fm: 63%, >30 fm: 

100%

Albin and Karpov 

1996, PFMC 2008, 

Hannah et al. 2012

West Coast Kelp Rockfish

multiple estimates 

varying by depth; sectors 

include recreational, rod 

and reel commercial 

nearshore

multiple sources of data are 

combined: 1) observed data and/or a 

guild-based model to estimate 

surface mortality; 2) single study to 

estimate short-term, below-surface 

mortality; 3) expert opinion to 

estimate long-term, delayed 

mortality

0-10 fm: 11%; 11-

20 fm: 19%, 21-30 

fm: 29%, >30 fm: 

100%

Albin and Karpov 

1996, PFMC 2008, 

Hannah et al. 2012

West Coast Olive Rockfish

multiple estimates 

varying by depth; sectors 

include recreational, rod 

and reel commercial 

nearshore

multiple sources of data are 

combined: 1) observed data and/or a 

guild-based model to estimate 

surface mortality; 2) single study to 

estimate short-term, below-surface 

mortality; 3) expert opinion to 

estimate long-term, delayed 

mortality

0-10 fm: 34%; 11-

20 fm: 45%, 21-30 

fm: 57%, >30 fm: 

100%

Albin and Karpov 

1996, PFMC 2008, 

Hannah et al. 2012

West Coast

Quillback 

Rockfish

multiple estimates 

varying by depth; sectors 

include recreational, rod 

and reel commercial 

nearshore

multiple sources of data are 

combined: 1) observed data and/or a 

guild-based model to estimate 

surface mortality; 2) single study to 

estimate short-term, below-surface 

mortality; 3) expert opinion to 

estimate long-term, delayed 

mortality

0-10 fm: 21%; 11-

20 fm: 35%, 21-30 

fm: 52%, >30 fm: 

100%

Albin and Karpov 

1996, PFMC 2008, 

Hannah et al. 2012
74

* = different estimates used by different 

regions

Region Species Type of Estimate Used Data supporting the estimate Estimates Citations

West Coast Tiger Rockfish

multiple estimates 

varying by depth; sectors 

include recreational, rod 

and reel commercial 

nearshore

multiple sources of data are 

combined: 1) observed data and/or a 

guild-based model to estimate 

surface mortality; 2) single study to 

estimate short-term, below-surface

mortality; 3) expert opinion to 

estimate long-term, delayed 

mortality

0-10 fm: 20%; 11-

20 fm: 35%, 21-30 

fm: 51%, >30 fm: 

100%

Albin and Karpov 

1996, PFMC 2008, 

Hannah et al. 2012

West Coast Treefish

multiple estimates 

varying by depth; sectors 

include recreational, rod 

and reel commercial 

nearshore

multiple sources of data are 

combined: 1) observed data and/or a 

guild-based model to estimate 

surface mortality; 2) single study to 

estimate short-term, below-surface 

mortality; 3) expert opinion to 

estimate long-term, delayed 

mortality

0-10 fm: 14%; 11-

20 fm: 25%, 21-30 

fm: 39%, >30 fm: 

100%

Albin and Karpov 

1996, PFMC 2008, 

Hannah et al. 2012

West Coast

Vermillion 

Rockfish

multiple estimates 

varying by depth; sectors 

include recreational, rod 

and reel commercial 

nearshore

multiple sources of data are 

combined: 1) observed data and/or a 

guild-based model to estimate 

surface mortality; 2) single study to 

estimate short-term, below-surface 

mortality; 3) expert opinion to 

estimate long-term, delayed 

mortality

0-10 fm: 20%; 11-

20 fm: 34%, 21-30 

fm: 50%, >30 fm: 

100%

Albin and Karpov 

1996, PFMC 2008, 

Hannah et al. 2012

West Coast

Widow 

Rockfish

multiple estimates 

varying by depth; sectors 

include recreational, rod 

and reel commercial 

nearshore

multiple sources of data are 

combined: 1) observed data and/or a 

guild-based model to estimate 

surface mortality; 2) single study to 

estimate short-term, below-surface 

mortality; 3) expert opinion to 

estimate long-term, delayed 

mortality

0-10 fm: 21%; 11-

20 fm: 36%, 21-30 

fm: 52%, >30 fm: 

100%

Albin and Karpov 

1996, PFMC 2008, 

Hannah et al. 2012
75

* = different estimates used by different 

regions

Region Species Type of Estimate Used Data supporting the estimate Estimates Citations

West Coast

Yelloweye 

Rockfish

surface release: multiple 

estimates varying by 

depth; release with 

descending device: 

multiple estimates 

varying by depth; sectors 

include recreational, rod 

and reel commercial 

nearshore

Surface release: multiple sources of 

data are combined: 1) observed 

discard data and a GLM model to 

estimate surface mortality with 

depth; 2) single study to estimate 

short-term, below-surface mortality; 

3) expert opinion to estimate longterm, delayed mortality; Release with 

descending device: 1) 90% upper 

confidence interval estimate of shortterm mortality estimates from cage 

studies, 2) long-term mortality 

estimates from an acoustic tagging 

study of descended fish.

Surface release: 0-

10 fm: 22%; 11-20 

fm: 39%, 21-30 

fm: 56%, >30 fm: 

100%; Release 

with descending 

device: 0-10 fm: 

26%, 10-30 fm: 

26%, 30-50 fm: 

27%, 50-100 fm: 

57% , >100 fm: 

100%

surface release: Albin 

and Karpov 1996, 

PFMC 2008; release 

with descending 

device: Jarvis and 

Lowe 2008, Hannah et 

al 2012, Wegner et al. 

unpublished raw data, 

PFMC 2012, PFMC 

2013, PFMC 2014

West Coast

Yellowtail 

Rockfish

multiple estimates 

varying by depth; sectors 

include recreational, rod 

and reel commercial 

nearshore

multiple sources of data are 

combined: 1) observed data and/or a 

guild-based model to estimate 

surface mortality; 2) single study to 

estimate short-term, below-surface 

mortality; 3) expert opinion to 

estimate long-term, delayed 

mortality

0-10 fm: 10%; 11-

20 fm: 17%, 21-30 

fm: 25%, >30 fm: 

50%

Albin and Karpov 

1996, PFMC 2008, 

Hannah et al. 2012

West Coast

Shallow Pelagic 

Rockfish Guild 

Proxy (applied 

to rockfishes in 

this guild 

without species 

specific data)

multiple estimates 

varying by depth; sectors 

include recreational, rod 

and reel commercial 

nearshore

multiple sources of data are 

combined: 1) observed discard data

from proxy species and guild-based 

GLM model to estimate surface 

mortality; 2) single study to estimate 

short-term, below-surface mortality; 

3) expert opinion to estimate longterm, delayed mortality

0-10 fm: 11%; 11-

20 fm: 19%, 21-30 

fm: 29%, >30 fm: 

100%

Albin and Karpov 

1996, PFMC 2008
76

* = different estimates used by different 

regions

Region Species Type of Estimate Used Data supporting the estimate Estimates Citations

West Coast

Deep Pelagic 

Rockfish Guild 

Proxy (applied 

to rockfishes in

this guild 

without species 

specific data)

multiple estimates 

varying by depth; sectors 

include recreational, rod 

and reel commercial 

nearshore

multiple sources of data are 

combined: 1) observed discard data 

from proxy species in the guild and 

guild-based GLM model to estimate 

surface mortality with depth; 2) 

single study to estimate short-term, 

below-surface mortality; 3) expert 

opinion to estimate long-term, 

delayed mortality

0-10 fm: 18%; 11-

20 fm: 30%, 21-30 

fm: 45%, >30 fm: 

100%

Albin and Karpov 

1996, PFMC 2008

West Coast

Shallow 

Demersal 

Rockfish Guild 

Proxy (applied 

to rockfishes in 

this guild 

without species 

specific data)

multiple estimates 

varying by depth; sectors 

include recreational, rod 

and reel commercial 

nearshore

multiple sources of data are 

combined: 1) observed discard data 

from proxy species in the guild and 

guild-based GLM model to estimate 

surface mortality with depth; 2) 

single study to estimate short-term, 

below-surface mortality; 3) expert 

opinion to estimate long-term, 

delayed mortality

0-10 fm: 13%; 11-

20 fm: 24%, 21-30 

fm: 37%, >30 fm: 

100%

Albin and Karpov 

1996, PFMC 2008

West Coast

Deep Demersal 

Rockfish Guild 

Proxy (applied 

to rockfishes in 

this guild 

without species 

specific data)

multiple estimates 

varying by depth; sectors 

include recreational, rod 

and reel commercial 

nearshore

multiple sources of data are 

combined: 1) observed discard data 

from proxy species in the guild and 

guild-based GLM model to estimate 

surface mortality with depth; 2) 

single study to estimate short-term, 

below-surface mortality; 3) expert 

opinion to estimate long-term, 

delayed mortality

0-10 fm: 11%; 11-

20 fm: 20%, 21-30 

fm: 29%, >30 fm: 

100%

Albin and Karpov 

1996, PFMC 2008

West Coast Cabezon

proxy; sectors include 

recreational, rod and reel 

commercial nearshore

proxy for species without swim 

bladder based on survival of lingcod 

accounting for hooking and handling 

mortality 7%

Albin and Karpov 

1996, PFMC 2008, 

Hannah et al. 2012

West Coast

California 

Scorpionfish

proxy; sectors include 

recreational, rod and reel 

commercial nearshore

proxy for species without swim 

bladder based on survival of lingcod 

accounting for hooking and handling 

mortality 7%

Albin and Karpov 

1996, PFMC 2008, 

Hannah et al. 2012
77

* = different estimates used by different 

regions

Region Species Type of Estimate Used Data supporting the estimate Estimates Citations

West Coast Kelp Greenling

proxy; sectors include 

recreational, rod and reel 

commercial nearshore

proxy for species without swim 

bladder based on survival of lingcod 

accounting for hooking and handling 

mortality 7%

Albin and Karpov 

1996, PFMC 2008, 

Hannah et al. 2012

West Coast Lingcod

1. one estimate; sectors 

include recreational, rod 

and reel commercial 

nearshore; 2. one 

estimate; sectors include 

trawl

1. single study accounting for 

hooking and handling mortality 

assessed during holding for an 

average of 15 days. no swim bladder 

thus no barotrauma or depth 

dependence of mortality; 2. 

estimated mortality from field 

studies. 1. 7%; 2. 50%

1. Albin and Karpov 

1996, PFMC 2008; 2. 

Parker et al. 2003

West Coast Pacific Cod

proxy; sectors include 

recreational, rod and reel 

commercial nearshore

multiple sources of data are 

combined: 1) observed data and/or a 

guild-based model to estimate 

surface mortality; 2) single study to 

estimate short-term, below-surface 

mortality; 3) expert opinion to 

estimate long-term, delayed 

mortality

0-10 fm: 5%; 11-20 

fm: 32%, 21-30 

fm: 53%, >30 fm: 

97%

Albin and Karpov 

1996, PFMC 2008, 

Hannah et al. 2012

West Coast Flatfish

proxy; sectors include 

recreational, rod and reel 

commercial nearshore

proxy for species without swim 

bladder based on survival of lingcod 

accounting for hooking and handling 

mortality 7%

Albin and Karpov 

1996, PFMC 2008, 

Hannah et al. 2012

West Coast Sharks

proxy; sectors include 

recreational, rod and reel 

commercial nearshore

proxy for species without swim 

bladder based on survival of lingcod 

accounting for hooking and handling 

mortality 7%

Albin and Karpov 

1996, PFMC 2008, 

Hannah et al. 2012

West Coast Skates

proxy; sectors include 

recreational, rod and reel 

commercial nearshore

proxy for species without swim 

bladder based on survival of lingcod 

accounting for hooking and handling 

mortality 7%

Albin and Karpov 

1996, PFMC 2008, 

Hannah et al. 2012
78

* = different estimates used by different 

regions

Region Species Type of Estimate Used Data supporting the estimate Estimates Citations

West Coast Spiny Dogfish

1. proxy; sectors include 

recreational, rod and reel 

commercial nearshore; 

2. single value informed 

by multiple studies; 

sectors include trawl; 3. 

proxy; sectors include 

fixed gear

1. proxy for species without swim 

bladder based on survival of lingcod 

accounting for hooking and handling 

mortality; 2. estimated mortality 

from field studies; 3. proxy value for 

trawl applied fixed gear fishery 

assuming it is conservative compared 

to trawl

1. 7%; 2. 50%; 3. 

50%

1. Albin and Karpov 

1996, PFMC 2008; 2. 

Mandelman and 

Farrington 2007, 

Rulifson 2007; 3. 

Proxy of 2. above.

West Coast Sablefish

1. single value informed 

by multiple studies; 

sectors include trawl; 2. 

single value informed by 

multiple studies; sectors 

include fixed gear

1. estimated mortality from field and 

laboratory studies; 2. estimated 

mortality from field and laboratory 

studies 1. 50%; 2. 20%

1. Erickson et al. 

1997, Olla et al. 1997, 

Olla et al. 1998, Davis 

et al. 2001, Davis and 

Olla 2002, Davis and 

Parker 2004, Davis 

2005, Davis and 

Ottmar 2006.

West Coast Longnose Skate

single rate based on 

preponderance of 

multiple studies; sectors 

include trawl and fixed 

gear

multiple skate mortality research 

studies considered and conservative 

estimate adopted. 50%

Laptikhovsky 2004, 

Stobutzki et al. 2002, 

Benoit 2006, Benoit et 

al. 2010, Enever et al. 

2009, Mandelman et 

al. 2012
79

* = different estimates used by different 

regions

Region Species Type of Estimate Used Data supporting the estimate Estimates Citations

West Coast

Chinook 

Salmon

multiple estimates by 

fishery and gear type multiple studies were combined

Commercial: 26% 

(barbless J-hook). 

Recreational north 

of Point Arena, 

CA: 14% (barbless 

J-hook). 

Recreational south 

of Point Arena, 

CA: troll caught 

14% (barbless Jhook), driftmooch-caught 42% 

(barbless circle 

hook), resulting in 

overall rate for 

fishery of 20-25%. 

All fisheries: apply 

an additional 

"dropoff mortality 

rate" of 5% to 

account for dropoff 

mortality, 

predation loss, noncompliance, etc.

Stohr and Fraidenburg 

1986, Salmon 

Technical Team 2000, 

Grover et al. 2002
80

* = different estimates used by different 

regions

Region Species Type of Estimate Used Data supporting the estimate Estimates Citations

West Coast Coho Salmon

multiple estimates by 

fishery and gear type multiple studies were combined

Commercial: 26% 

(barbless J-hook). 

Recreational north 

of Point Arena, 

CA: 14% (barbless 

J-hook). 

Recreational south 

of Point Arena, 

CA: troll caught 

14% (barbless Jhook), driftmooch-caught 42% 

(barbless circle 

hook), resulting in 

overall rate for 

fishery of 20-25%. 

All fisheries: apply 

an additional 

"dropoff mortality 

rate" of 5% to 

account for dropoff 

mortality, 

predation loss, noncompliance, etc.

Stohr and Fraidenburg 

1986, Salmon 

Technical Team 2000, 

Grover et al. 2002

Alaska

Demersal Shelf 

Rockfish

assumption of 100% 

mortality

single study (additional studies are 

recently completed) 100% Brylinsky et al. 2009

Alaska Pacific Halibut

multiple estimates for 

different gear single study

Circle hooks: 

3.5%; "J" hooks: 

10% Meyer 2007

Alaska

Chinook 

Salmon

multiple estimates by 

size and gear type multiple studies were combined

Commercial: legal 

size 21.2% and 

sublegal: 25.5% 

(barbed J-hook); 

legal size 18.5% 

and sublegal 22.0% 

(barbless J-hook), 

Recreational: 

>33cm 12.3% and 

<33cm 32.2% 

(barbless J-hook)

Chinook Technical 

Committee 1997
81

References

Aguilar, R., P. S. Rand, and G. H. Beckwith. 2002. Quantifying the catch-and-release mortality rate of adult red drum in the Neuse River estuary. North Carolina Fisheries Resource 

Grant Program, 01- FEG-07. Raleigh, North Carolina.

Albin D., and K. Karpov. 1996. Northern California sport fish project lingcod hooking mortality study. California Department of Fish and Game Cruise Report.

Benoît, H. P. 2006. Estimated discards of winter skate (Leucoraja ocellata) in the southern Gulf of St. Lawrence, 1971–2004. Can. Sci. Adv. Sec. Res. Doc., 2006/002.

Benoît H. P., T. Hurlbut, and J. Chassé. 2010. Assessing the factors influencing discard mortality of demersal fishes using a semi-quantitative indicator of survival potential. 

Fisheries Research 106 436–447.

Brylinsky, C., J. Stahl, D. Carlile, and M. Jaenicke. 2009. Assessment of the demersal shelf rockfish stock for 2010 in the southeast outside district of the Gulf of Alaska. Chapter 14 in 

Stock Assessment and Fishery Evaluation report, North Pacific Fishery Management Council.

Bugley, K., and G. Shepherd. 1991. Effect of catch-and-release angling on the survival of black sea bass. N Am J Fish Mgmt. 11: 468-471.

Burns, K. M., R. R. Wilson, and N. F. Parnell. 2004. Partitioning release mortality in the undersized red snapper bycatch: comparison of depth vs. hooking effects. Mote Marine 

Laboratory Tech. Rept. No. 932 funded by NOAA under MARFIN Grant # NA97FF0349.

Burns, K. M., C. C. Koenig, and F. C. Coleman. 2002. Evaluation of multiple factors involved in the release mortality of undersized red grouper, gag, red snapper, and vermilion 

snapper. Mote Marine Laboratory Technical Report No. 790.

Chinook Technical Committee. 1997. Incidental mortality of Chinook salmon: mortality rates applicable to Pacific Salmon Commission fisheries. Pacific Salmon Commission. 

Vancouver B.C. Report TCCHINOOK (97)-1. 53 p.

Clay, D., W. T. Stobo, B. Beck, and P. C. F. Hurley. 1989. Growth of juvenile pollock (Pollachius virens L.) along the Atlantic coast with inferences of inshore-offshore movements. 

J Northwest Atl Fish Sci. 9:37-43.

Collins, M. R. 1996. Survival estimates for demersal reef fishes released by anglers. Proceedings of the 43rd Annual Gulf and Caribbean Fisheries Institute, Nassau, Bahamas, 

November 1991.

Collins, M. R., J. C. McGovern, G. R. Sedberry, H. S. Meister, and R. Pardieck. 1999. Swim bladder deflation in black sea bass and vermilion snapper: potential for increasing post 

release survival. N. Am. J. Fish. Manage. 19:828-832.

Davis M. W., and B. L. Olla. 2001. Stress and delayed mortality induced in Pacific halibut Hippoglossus stenolepis by exposure to hooking, net towing, elevated sea water 

temperature and air: implications for management of bycatch. N. Am. J. Fish. Manage. 21: 725–732.

Davis M. W., B. L. Olla, and C. B. Schreck. 2001. Stress induced by hooking, net towing, elevated sea water temperature and air in sablefish: lack of concordance between mortality 

and physiological measures of stress. J. Fish Biol. 58: 1–15.

Davis, M. W., and B. L. Olla. 2002. Mortality of lingcod towed in a net is related to fish length, seawater temperature and air exposure: a laboratory bycatch study. N. Am. J. Fish. 

Manage. 22: 1095–1104.

Davis, M. W., and S. J. Parker. 2004. Fish size and exposure to air: potential effects on behavioral impairment and mortality rates in discarded sablefish. N. Am. J. Fish. Manage. 24: 

518-524.

Davis, M. W. 2005. Behavior impairment in captured and released sablefish: ecological consequences and possible substitute measures for delayed discard mortality. J. Fish. Biol. 

66: 254-256.

Davis, M. W., and M. L. Ottmar. 2006. Wounding and reflex impairment may be predictors for mortality in discarded or escaped fish. Fish. Res. 82: 1-6.

Diodati, P.J., and A.R. Richards. 1996. Mortality of striped bass hooked and released in saltwater. Transactions of the American Fisheries Society 125:300-307.

Durso, V., and H. Iwanowicz. 1983. Hooking mortality of winter flounder Pseudopleurocnectes americanus in coastal Massachusetts waters. MA Div. Marine Fisheries. 88p.
82

Edwards, R .E. 1996. King mackerel hooking mortality assessment. National Marine Fisheries Service Report No. 92-SER-035, St. Petersburg, Florida.

Enever, R., T. L. Catchpole, J. R. Ellis, and A. Grant. 2009. The survival of skates (Rajidae) caught by demersal trawlers fishing in UK waters. Fisheries Research 97: 72–76.

Erickson D., E. Pikitch R. Methot, E. Babcock, and J. Wallace. 1997a. Survival of trawl-caught and discarded sablefish (Anoplopoma fimbria) during summer trials. Cruise Report 26 

August - 10 September 1997.

Erickson D., E. Pikitch, R. Methot, E. Babcock, T. Builder, J. Wallace , P. Crone, J. Brodziak, and R. Conser. 1997b. Survival of trawl caught and discarded sablefish (Anoplopoma 

fimbria) off the U.S. West Coast. 1997. ICES Annual Science Conference Theme Session: Fisheries Technology CM 1997/FF:06.

Gearhart, J. 2002. Hooking mortality of spotted seatrout, weakfish, red drum, and southern flounder in North Carolina. Morehead City (NC): DENR Division of Marine Fisheries. 

Completion Report for Cooperative Agreement No. NA 87FG0367/2. Documentation and Reduction in Bycatch in North Carolina, Job 3.

Gertseva, V. 2008. Status of the longnose s kate (Raja rhina) off the continental US Pacific Coast in 2007. Pacific Fishery Management Council, Portland, Oregon. 

http://www.pcouncil.org/groundfish/stock-assessments/by-species/longnose-skate/

Gertseva, V. ,and I. Taylor. 2012. Status of the spiny dogfish shark resource off the continental U.S. Pacific Coast in 2011. Pacific Fishery Management Council, Portland, Oregon. 

http://www.pcouncil.org/groundfish/stock-assessments/by-species/spiny-dogfish/

Grover, A. M., M. S. Mohr, and M. Palmer-Zwahlen. 2002. Hook-and-release mortality of Chinook salmon from drift mooching with circle hooks: management implications for 

California's ocean sport fishery. In J.A. Lucy and A.L. Studholme, editors, Catch and release in marine recreational fisheries., Symposium 30, pp. 39-56. American Fisheries Society, 

Bethesda, Maryland.

Hannah, R. W., P. S. Rankin, and M. T. O. Blume. 2012. Use of a novel cage system to measure postrecompression survival of Northeast Pacific rockfish. Marine and Coastal 

Fisheries: Dynamics, Management and Ecosystem Science 4:46-56.

Howell, P. T., and D. G. Simpson. 1985. A study of marine recreational fisheries in Connecticut. March 1, 1981 - February 28, 1984. CTDEP, Fed Aid to Sport Fish Restoration 

F54R. Final Rep. 60 p.

Jarvis, E. T., and C. G. Lowe. 2008. The effects of barotrauma on the catch-and-release survival of southern California nearshore and shelf rockfish (Scorpaenidae, Sebastes spp.). 

Canadian Journal of Fisheries and Aquatic Sciences 65:1286-1296.

Laptikhovsky, V. 2004. The survival rates of rays discarded by the squid-targeting bottom trawl fishery off the Falkland Islands. Fish. Bull., 102(4), 757-

759.

Low, R. A., Jr. 1981. Mortality rates and management strategies for black sea bass off the southeast coast of the United States. N. Am. J. Fish. Manage. 1:93-103.

Lucy, J.A., and T. D. Holton. 1998. Release mortality in Virginia’s recreational fishery for summer flounder, (Paralichthys dentatus) VA Mar Res Rep. 97-8. 48 p

Malchoff, M.H., and S. W. Heins. 1997. Short-term hooking mortality of weakfish caught on single-barb hooks. N Am J Fish Manage. 17:477-481.

Malchoff, M. H., and J. Lucy. 1998. Short-term hooking mortality of summer flounder in New York and Virginia. Interim report for Cornell Univ/DEC Project MOU 000024. 6 p.

Malchoff, M., J. Gearhart, and J. Lucy. 2001. Short-term hooking mortality of summer flounder in New York, Virginia, and North Carolina (ASMFC 2001).

Malchoff, M. H. 1995. Effects of catch and release on important northeast marine fishers: mortality factors and applications to recreational fisheries. NY Sea Grant Extension 

Program, Cornell Cooperative Extension Report, Riverhead, NY.

Mandelman, J. W., and M.A. Farrington. 2007. The estimated short-term discard mortality of a trawled elasmobranch, the spiny dogfish (Squalus acanthias). Fisheries Research 83: 

238–245 

Mandelman, J. W., R. A. Morrison, J. M. Cavin, and M. A. Farrington. 2012. The blood chemical status of Atlantic cod, Gadus morhua, following capture by jig and demersal 

longline with differential hook removal methods. J. Fish Biol. 81: 1406-1414.

McGovern, J. C., G. R. Sedberry, H. S. Meister, T. M. Westendorff, D. M. Wyanski, and P. J. Harris. 2005. A tag and recapture study of gag, Mycteroperca microlepis, off the 

Southeastern U.S. Bulletin of Marine Science, 76(1): 47-59.
83

Meyer, S. 2007. Halibut discard mortality in recreational fisheries in IPHC Areas 2C and 3A. Discussion paper. Alaska Department of Fish and Game Division of Sport Fish Homer, 

Alaska.

Murphy, M.D., R. F. Heagey, V. H. Neugebauer, M. D. Gordon, and J. L. Hintz. 1995. Mortality of spotted seatrout released from gill-net or hook-and-line gear in Florida. N Am J 

Fish Manage. 15:745- 753.

Murphy, M. D. 2005. A stock assessment of red drum, Sciaenops ocellatus in Florida: status of the stocks through 2003. Report to the Florida Fish and Wildlife Conservation 

Commission from the Fish and Wildlife Research Institute, St. Petersburg. FWRI In-House Report 2005-006.

Olla, B. L., M. W. Davis, and C. B. Schreck. 1997. Effects of simulated trawling on sablefish and walleye pollock: the role of light intensity, net velocity and towing duration. J. Fish 

Biol. 50: 1181–1194.

Olla B. L., M. W. Davis, and C. B. Schreck. 1998. Temperature magnified postcapture mortality in adult sablefish after simulated trawling. J. Fish Biol. 53: 743–751.

Overton, A. S., and J. Zabawski. 2003. Release mortality of undersized fish from the snapper/grouper complex off the North Carolina coast. NC Sea Grant 03-FEG-21.

Parker, S.J., P. S. Rankin, R. W. Hannah, and C. B. Schreck. 2003. Discard mortality of trawl-caught lingcod in relation to tow duration and time on deck. N. Am. J. Fish. Manage. 

23: 530-542.

PFMC (Pacific Fishery Management Council). 2008. Final environmental impact statement for the proposed acceptable biological catch and optimum yield specifications and 

management measures for the 2009-2010 Pacific Coast groundfish fishery. Portland, OR: Pacific Fishery Management Council. Chapter 4: 276-290. http://www.pcouncil.org/wpcontent/uploads/chp4_0910.pdf

PFMC (Pacific Fishery Management Council). 2012. Groundfish Management Team progress report on developing mortality rates for rockfish released using descending devices. 

Pacific Fishery Management Council, Portland, OR. November Council Meeting, Agenda Item I.3. http://www.pcouncil.org/wp-content/uploads/I3b_GMT_NOV2012BB.pdf

PFMC (Pacific Fishery Management Council). 2013. Groundfish Management Team report on proposed discard mortality for cowcod, canary rockfish, and yelloweye rockfish 

released using descending devices in the recreational fishery. Pacific Fishery Management Council, Portland, OR. April Council Meeting, Agenda Item D.5, 

http://www.pcouncil.org/wp-content/uploads/D5b_GMT_APR2013BB.pdf

PFMC (Pacific Fishery Management Council). 2014. Groundfish Management Team report on proposed discard mortality for cowcod, canary rockfish, and yelloweye rockfish 

released using descending devices in the recreational fishery. Pacific Fishery Management Council, Portland, OR. March Council Meeting, Agenda Item D.3, 

http://www.pcouncil.org/wp-content/uploads/D3b_SUP_GMT_RPT2_MAR2014BB.pdf

Rudershausen, P. J., A. Ng, and J. A. Buckel. 2005. By-catch, discard composition, and fate in the snapper/grouper commercial fishery, North Carolina. NC Sea Grant 04-FEG-08.

Rulifson, R.A. 2007. Spiny dogfish mortality induced by gill-net and trawl capture and tag and release. North American Journal of Fisheries Management 27:279–285.

Salmon Technical Team. 2000. STT recommendations for hooking mortality rates in 2000 recreational ocean Chinook and coho fisheries. STT report B.2. March 2000. Pacific 

Fishery Management Council, Portland, OR. 18p.

Simpson, D. G., and M. Gates. 1999. Studies in Conservation Engineering, Job 4. In: A Study of Marine Recreational Fisheries in Connecticut. Final Report. Pp 121 – 127. CT DEP 

Marine Fisheries Office, Old Lyme, CT.

Stobutzki, I. C., M. J. Miller, D. S. Heales, and D. T. Brewer. 2002. Sustainability of elasmobranchs caught as bycatch in a tropical prawn (shrimp) trawl fishery. Fish. Bull. 100, 

800–821.

Stohr, A. J. M., and M .E. Fraidenburg. 1986. A Delphi estimate of chinook and coho salmon hooking mortality. State of Washington, Department of Fisheries. Technical Report 

No. 94. 91p.

Swihart G. L., J. I. Galvez, L. B. Daniel, and M. L. Swihart. 2000. Evaluation of hook and release mortality from a recreational hook and line fishery on weakfish (Cynocsion regalis). 

Gloucester (MA): US Fish and Wildlife Service Office of Fishery Assistance. 4 p.
84

Terceiro, M. 2011. Stock assessment of scup for 2011. NOAA National Marine Fisheries Service Northeast Fisheries Science Center Reference Document 11-21. October 2011. 

104p.

Vaughan, D. S., M. R. Collins, and D. J. Schmidt. 1995. Population characteristics of the black sea bass Centropristis striata from the southeastern U.S. Bull. Mar. Sci. 56:250-267.

Wegner, N. C., A. L. Pribyl, and J. R. Hyde, J.R. 2012-2014. Rockfish barotrauma study. Unpublished raw data.

Vecchio, J. L., and C. A. Wenner. 2007. Catch-and-release mortality in sub-adult and adult red drum captured with popular fishing hook types. N. A. J. Fish. Manage. 27:891–899.

Wilson, Jr., R. R., and K. M. Burns. 1996. Potential survival of released groupers caught deeper than 40m based on shipboard and in-situ observations, and tag recapture data. Bull. 

Mar. Sci. 58: 234-247.