Short-term Hooking Mortality and Movement of Adult Red Drum (Sciaenops ocellatus) in the Neuse River, North Carolina.
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Date
2003-08-21
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Abstract
Despite the increasing importance of the red drum Sciaenops ocellatus recreational fishery, little is known about mortality rates of caught and released adult red drum. In this study, short-term hooking mortality rates (3-d) of adult red drum caught on 7/0 j-style hooks and 16/0 circle ('tuna') hooks from the Neuse River, North Carolina were determined via ultrasonic telemetry (2000) and confinement in field enclosures (2001). From June to September 2000, 22 red drum (928-1180 mm fork length; FL) were angled, tagged with ultrasonic transmitters, and released. An overall short-term mortality rate of 5.7% was determined for 17 fish. Due to the limited sample size, no attempt was made to model the factors associated with mortality. From June to September 2001, 112 red drum (880-1250 mm FL) were angled and held in net pens for 3 d to assess short-term mortality. An overall mortality rate of 6.7% was determined for 104 fish. Logistic regression analysis indicated that hook position (P = 0.012) and surface salinity (P = 0.002) were significantly related to mortality However, fish size (FL), sex, surface water temperature, depth, landing time, handling time, transport time, and hook type were not significantly related to mortality. Logistic regression analysis also indicated that hook position was dependent on hook type (P = 0.002) and sex (P = 0.015), but not fork length, surface water temperature, and depth. Approximately 52% percent of fish caught with j-style hooks were deep hooked, compared with 4.2% of those caught with circle hooks. A larger percentage of fish deep hooked with j-style hooks died compared to those deep hooked with circle hooks (15.9% vs. 0%, respectively). Necropsy analysis of five mortalities (all deep hooked) indicated extensive internal hemorrhaging and damage to tissues and organs. These data suggest the conservation goal of reducing post-release mortality on these fish can be achieved through directed efforts at either promoting or requiring certain terminal gear (particularly through the use of circle hooks) to reduce incidence of deep hooking.
Movement information was collected for 18 of the 22 (81.8%) red drum angled and tagged with ultrasonic transmitters in 2000. Biotelemetry proved to be an effective method for examining adult red drum movement. Red drum appeared to exhibit seasonal fidelity to the lower Neuse River during the summer and fall months, but not to specific locations within this system. Most adult red exhibited a noticeable upriver-downriver ('longshore') pattern of movement, which was supported by Rayleigh's tests of individual fish movement. There was no significant difference between the mean angles (Watson's two-sample U2 test: 0.2 < P < 0.5) and movement rates (Wilcoxon rank sum test; P = 0.4068) of male (3.25±0.62 km d-1) and female (5.50±2.08 km d-1) tagged and released red drum. Furthermore, the difference between day and night relocation depths for male and female red drum was not significantly different (Wilcoxon rank sum test: P = 0.5610). On 14 separate occasions, two red drum were located in close proximity to each other (~5 m to 300m), which was defined as a co-occurrence. Given the high number of co-occurrences, mobile nature of fish movement, seasonal residency, and apparent longshore movement pattern, adult red drum appear to form short-term loose aggregations within the Neuse River during the summer and early fall months. These data also indicate the lower Neuse River and similar areas of the western Pamlico Sound are important habitat for red drum in North Carolina.
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red drum, Sciaenops ocellatus, hooking mortality, circle hook, ultrasonic telemetry, Pamlico Sound, Neuse River, movement
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Degree
MS
Discipline
Zoology
