Hooking Mortality and Behavior of Striped Bass Following Catch and Release Angling

PHILLIP W. BETTOLI* AND RANDALL S. OSBORNE1
Abstract.—Concerns over the use of minimum-size regulations to increase the average weight of harvested striped bass Morone saxatilis in Tims Ford Reservoir, Tennessee, prompted this study of hooking mortality. To estimate mortality and examine behavior, striped bass longer than 508 mm total length were caught with conventional angling gear, tagged externally with ultrasonic transmitters equipped with floats, and released back into Tims Ford Reservoir. Over a 15-month period 89 fish were tagged and tracked for a minimum of 3 d. Mortality rates ranged from 14% in November and December 1993 to 67% in both August 1993 and July 1994. Although the confounding effects of tagging could not be separated from the effects of being hooked and released, disparate mortality rates among seasons, as well as observations of feeding and swimming behavior of tagged fish that survived, suggested that tagging effects were modest compared to hooking effects. Mortality rates were linearly related to air temperature (P ?? 0.012) but not to landing time, handling time, bait type, fish total length, or water temperature. Characteristics that differed between striped bass that survived and those that did not were air temperature at capture (t-test; P ?? 0.007) surface water temperature (t-test; P ?? 0.081), and handling time (t-test; P ?? 0.06). Nine striped bass were caught, tagged, and tracked intensively following release in late August 1994 to document their short-term behavior. All six fish that survived remained in warm surface waters for about 2 h following release before descending to the top of metalimnion. The three fish that died, surfaced within 1.5 h, from which we inferred that they were unable to regulate air bladder pressure. We concluded that a proposed year-round size limit of 610 mm total length would probably not improve the size structure of the population because of the high mortality of released fish that occurred during summer months.