Striped Bass Catch and Release Mortality

Circle Hooks

 MDDNR studies with American shad, hickory shad, yellow perch, white perch , summer flounder and striped bass have shown that there are two main factors that cause mortality among released fish: physical injury from hook wounds and stress from the physiological exertion from fighting.

Deep-hooking can be influenced by fishing method (bait vs. artificial lures), hook configuration (J-style vs. circle hook), fish behavior and angler experience.

Stress-related mortality can be influenced by temperature (both water and air), salinity and fish size.

When fishing with bait, deep-hooking can be reduced 60-80% by using non-offset circle hooks instead of J-style hooks.

Results of DNR Circle Hook Studies

Deep-Hooking Rate

            Year                             J-Hooks                       Circle Hooks               % Reduction

            1999                            17.2%                          3.4%                            80%

            2000                            15.0%                          5.0%                            67%

            2001                            17.1%                          6.6%                            60%

            2002                            12.3%                          2.4%                            80%

Even if a striped bass is deep-hooked with a non-offset circle hook it will die approximately 50% less often than one deep-hooked with a J-style hook.                           

Results of DNR Circle Hook Studies

Deep-Hooking Mortality

            Year                             J- Hooks                      Circle Hooks               % Reduction

            1999                            53.1%                          23.5%                          57%

            2000                            58.3%                          33.3%                          43%

Approximately 90% of the striped bass caught in these studies were less than the 18-inch size limit in place at the time.

Results of DNR Circle Hook Studies

Striped Bass less than 18 inches

                        Deep-Hooking            Deep-Hooking            Projected Mortality

                              Rate                                   Mortality (approx.)

            Year    J-Hooks   Circle Hooks           J-Hooks   Circle Hooks           J-Hooks   Circle Hooks

            1999      15.2%      2.0%                       50%              25%                  7.6%                0.5%

            2000      10.9%      3.3%                         50%             25%                  5.4%                0.8%

            2001      14.8%      3.2%                         50%              25%                 7.4%                0.8%

            2002       9.7%        2.4%                        50%              25%                 4.8%                0.6%

These studies show that mortality among striped bass that must be released because they are too small can be reduced by about 90%.

STRESS RELATED MORTALITY

Environmental factors such as temperature (both water and air) and salinity, while not under the control of the angler, should be considered as potential contributors  to release mortality.

Studies have shown that in fresh water (no salinity) such as the Susquehanna Flats, increasing water temperature will increase release mortality among shallow-hooked striped bass.

Susquehanna Flats Catch-and-Release Study- 1998

                        Water Temperature (F)                                                Mortality Rate

                                    57-59F                                                                         0.15%

                                    61-62F                                                                         4.2%

                                    64-71F                                                                         16.4%

A summary of seven catch-and-release studies  conducted with striped bass in fresh water (including ours) was published in the North American Journal of Fisheries Management in 2000 by Wilde et al. They reported that the average mortality of striped bass caught in fresh water with artificial lures was 8% at 60F and 18% at 70F.

Studies done in Maryland’s Chesapeake Bay have shown when salinity is present at levels of 2 parts per thousand (ppt, 0.2%) or greater water temperature does not influence stress related mortality of striped bass. Statistical analysis of more than 1300 striped bass used in MDDNR studies (1996-2000) in which water temperature ranged from 59F to 83F did not detect an influence of water temperature on mortality. All of these studies were conducted in water with at least 2 parts per thousand salinity.. A study in California with fresh water acclimated striped bass showed enhanced recovery if they were placed in brackish water (Cech et al. 1996).

Time out of water, particularly during hot weather, also increases stress related mortality. High air temperatures have been shown to increase release mortality in both fresh and salt water.

Mortality Rate of Shallow-Hooked Striped Bass

                        Chesapeake Bay 1999                         Fresh Water in Tennessee 1998 *

                        Air Temp. (F)   Mortality Rate                        Air temp. (F)   Mortality  Rate

                        <95F                  0.8%                                      59F                  14%

                        >95F                17.2%                                     88F                  67% 

• (Bettoli and Osborne 1998)

HOOK STYLE COMPARISONS

(deep hooking rates and catch rates)

J-hooks vs. circle Hooks :

Deep hooking rate – J-hooks: 15-17%

Deep-hooking rate – non-offset circle hooks : 3%

Catching efficiency (% of fish landed per strike)

J-hooks: 41.7%

Non-offset circle hooks: 27.4%

Kahle vs. non-offset circle hooks vs .offset circle hooks

Deep hooking rate – Kahle :12.3%

Deep hooking rate – offset circle hooks: 2.8%

Deep hooking rate  – non-offset: 2.4%

Catching efficiency (% of fish landed per strike)

Kahle: 41%

Offset circle hooks: 21%

Non-offset circle hooks: 26%