The diet and growth of blue catfish in a southeastern reservoir

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Chapter II Movement and habitat use of blue catfish in Lake Norman, North Carolina

Introduction

Knowledge of seasonal fish movement and habitat use are key components to management plans being developed by fisheries managers. By defining the migration patterns of individual populations and the habitat they utilize, fisheries managers can develop suitable sampling regimes to perform additional stock assessments (Hubert 1999; Millspaugh and Marzluff 2001). Literature review suggests that blue catfish Ictalurus furcatus are the most migratory of all ictalurid catfishes (Lagler 1961) capable of long distance seasonal migrations (Graham 1999; Pugh and Schramm 1999). But the overall knowledge of seasonal or yearly movements or home ranges in a reservoir system, as well as blue catfish habitat preferences, are limited (Ramsey and Graham 1991). Movement
Blue catfish are considered more mobile than flathead catfish Pylodictis olvivaris (Pugh and Schramm 1999) but similar in movement and habitat use to channel catfish Ictalurus punctatus (Ramsey and Graham 1991; Graham 1999). Flathead catfish were found to be generally sedentary with small home ranges (Hart 1974; Jackson 1999). Channel catfish were found to be more mobile, with recent tagging and telemetry studies documenting movements from winter areas to spawning areas and then to summer feeding areas (Hubert 1999). Pellett et al. (1998) observed channel catfish in the Wisconsin River occupying small summer home ranges, migrating downstream into the Mississippi River during the fall, back upstream to spawn in the Wisconsin River in the spring, and then returning to the same small summer home range used the previous summer. Similar movements for blue catfish have been reported in reservoirs; migrations upstream to tributaries and headwater rivers for spawning and downstream to the reservoirs to overwinter (Pflieger 1997; Graham 1999).

Habitat use

Blue catfish prefer open waters of large reservoirs and main channels, as well as flowing rivers, where water is normally turbid and substrate varies from sand- gravel to silt-mud (Burr and Warren 1986; Graham 1999). Blue catfish breed in sheltered nests when water temperatures reach 21-24 ºC (Jordan and Evermann 1920; Harlan and Speaker 1956). Both sexes share in the brooding (Jones 1965), with about 2,000 eggs laid per pound of female (Pelzman 1971). The specific habitat preferences of blue catfish are relatively unknown (Lagler 1961), but are believed to be similar to those of channel catfish (Pflieger 1997; Hubert 1999). The maximum water temperature at which channel catfish can survive for long periods is 37ºC (Moss and Scott 1961), with a minimum requirement of 1 mg/L of dissolved oxygen at 25-35º to survive and greater than 4 mg/L to spawn. Channel catfish are considered habitat generalists (Layher and Maughan 1985) being found in a variety of water velocities and structure (Hubert 1999). There is evidence of differential habitat use by adult channel catfish in rivers as a function of fish size. Large channel catfish (>500 mm TL) utilized faster water areas where forage fish were more abundant, while smaller channel catfish (<500 mm TL) were in areas of slower water velocity where aquatic insects were abundant (Macdonald 1990; Hubert 1999). Segregation in reservoirs of habitat use by channel catfish of different size classes was also observed (Klaasen and Marzolf 1971). Most studies of fish movement and habitat use within a larger water body (i.e. reservoirs) use telemetry, but this approach is problematic when applied to catfish.

Telemetry studies

Transintestinal transmitter expulsion has been reported as a potential obstacle to telemetry studies of channel catfish (Marty and Summerfelt 1986; 1988; Siegwarth and Pitlo 1999). Summerfelt and Mosier (1984) offered evidence that internally implanted transmitters can be lost by absorption into the intestinal tract and expulsion through the anus. Other losses of internal transmitters were attributed to ruptures of the original implant incision, thereby allowing the transmitters to pass through the original point of entry. Siegwarth and Pitlo (1999) developed a modified surgical procedure for implanting transmitters and attaching them to the pectoral girdle. Though this modified procedure resulted in higher retention rates of transmitters, a mortality rate of 32% and a missing rate of 29% were noted. It was undetermined if the mortality rate was a result of blocking the natural expulsion process of foreign objects by channel catfish (Siegwarth and Pitlo 1999). It is also unknown whether the reported problems with transmitter expulsion in channel catfish would also occur in blue catfish.
Studies of external trans mitters on other fish species have shown no significant differences in survival or growth between fish with and without transmitters (Ross and McCormick 1981; Herke and Moring 1999). In addition, external transmitters record the movement into differing water temperatures more quickly than internal transmitters (Winter 1996). Concerns against using external transmitters include the increased chance of entanglement and possible interference with swimming behavior and speed (Winter 1996; Mellas and Haynes 1985).

Lake Norman, North Carolina

Currently, there is a popular fishery for blue catfish in Lake Norman, including recreational, commercial, and tournament-sport anglers. However, the movement, home range, and habitat use by blue catfish in Lake Norman are unknown. To improve the overall knowledge of blue catfish ecology within a large reservoir, I utilized radio telemetry to: (1) determine the seasonal movement and home range of blue catfish in Lake Norman; and (2) to determine seasonal habitat use by blue catfish. Due to the well documented methods for expulsion of internal radio transmitters by catfish, I chose to use externally attached radio transmitters for this study and examine overall survival rates for this method.

Methods

Radio-Telemetry
Laboratory Study
During November 2000, I collected sixteen blue catfish (500-900 mm) by hook-and- line sampling techniques. Blue catfish were transported to the Virginia Tech Aquaculture Center in Blacksburg, VA, where they were divided into two groups of eight and placed in separated 540-gallon tanks (6 ft. x 30 in.) with a recirculating tube sump and trickling biofilter. A variety of minnows, sunfish, and shad were used to feed all sixteen blue catfish during the duration of the lab study.
On December 1, 2000, I attached a waterproof hysol-coated dummy radio transmitter (Advanced Telemetry Systems, Isanti, MN) externally to the dorsal musculature of eight lab study blue catfish (four from each tank). Dummy transmitters were 4.3 cm long with two 0.9-mm attachment wires set 60 mm apart, a 1.5-mm x 432cm trailing external antenna, and weighed 26 grams. A 6.4- mm neoprene pad was attached to the attachment side of dummy transmitter to reduce abrasions to the dorsal surface of each blue catfish. I anaesthetized blue catfish using 350 ppm sodium bicarbonate (Booke et al. 1978; Post 1979; Stefan 1992; Prince et al. 1995; Peake 1998) before recording individual length (m, TL) and weight (g).
My procedure for attaching the external radio transmitters to blue catfish was as follows:

  1. I inserted a 16-gauge non-coring-point spinal needle through the dorsal musculature perpendicular to the lateral line and posterior to the dorsal spine. I then passed the forward attachment wire through the needle and removed the needle, leaving only the forward attachment wire running through the dorsal musculature.
  2. I inserted a second needle 60 mm anterior to the original needle insertion and repeated the preceeding step for the rear attachment wire.
  3. I secured each transmitter with two 6.25- mm plastic discs attached to each wire on the opposite side of the body, and placed a 6.4- mm neoprene between the plastic discs and blue catfish body to reduce abrasions.

After completing the transmitter attachment, I placed the blue catfish into a holding tank until recovery from the anesthetic was observed, and then released the blue catfish back into their respective holding tank. The maximum time to complete each individual transmitter attachment, from introducing blue catfish to anesthetic to releasing back into their respective tanks after recovery, was 20 minutes (maximum time to attach each external transmitter was 5 minutes). Blue catfish, with their respective attached dummy transmitters, was observed for four months in water temperatures of 10-16º C, after which time I sacrificed and individually examined fish for dorsal musculature tissue damage due to attachment wire abrasion.

Field Study

During February and March 2001, I collected twenty-nine blue catfish >2000-grams from throughout Lake Norman, using hook and line sampling techniques, to outfit with external radio transmitters.  Each transmitter was identical in dimensions to thedummy transmitters used in the lab test, with the following added features:

  1. Saft AA 3.6 lithium battery
  2. magnetic ON/OFF switch
  3. microprocessor program controlled
  4. duty cycle (2 weeks on and 2 weeks off, repeat)
  5. 4º – 40º C temperature sensor with pulse indicator
  6. 24-hour mortality switch with a duty cycle override.

Introduction
Study Site
Chapter One: The diet and growth of blue catfish in a southeastern reservoir.
Introduction
Methods
Results
Discussion
Chapter :Two Movement and habitat use of blue catfish in Lake Norman, North Carolina.
Introduction
Methods
Results
Discussion
Chapter Three: Genetic analysis of introduced blue catfish populations
Introduction
Study Site
Methods
Results
Discussion
Chapter Four : Management of blue catfish
Literature Cited
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ANALYSIS OF A BLUE CATFISH POPULATION IN A SOUTHEASTERN RESERVOIR: LAKE NORMAN, NORTH CAROLINA

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