Conservation, Ecology, and Management of Catfish: The Second International Symposium

<em>Abstract</em>.—Using Long Term Resource Monitoring Program data collected from impounded (Pool 26) and unimpounded (Open River) reaches of the upper Mississippi River, we investigated population dynamics of flathead catfish <em>Pylodictis olivaris</em>, channel catfish <em>Ictalurus punctatus</em>, and blue catfish <em>I. furcatus</em> from random sites located in side channel border (SCB) and main channel border (MCB) habitats. Objectives were to (1) compare trends (1993–2007) of three catfishes collected in Pool 26 and Open River reaches of the upper Mississippi River, and (2) provide needed information to managers on population dynamics through time using a binary gear approach of active (i.e., daytime electrofishing) and passive gears (hoopnetting). Active gears resulted in a higher catch per unit effort (CPUE) of all catfishes in each habitat–reach combination as compared to passive gears. Passive gears resulted in negligible catches of blue catfish and flathead catfishes (e.g., mean of <1 fish/net night). Catch per unit effort using active gear resulted in a greater number of channel catfish captured in Pool 26 compared to the Open River, with Open River SCB habitat having the lowest CPUE in most years. Blue catfish in the Open River had a higher CPUE using active gear as compared to Pool 26, with the Open River MCB having the greatest CPUE. Flathead catfish had a higher CPUE in MCB habitat compared to SCB habitat, with the Open River MCB having the highest CPUE in most years. However, declining trends in flathead catfish appears to be occurring in Open River habitats while trends in flathead catfish appear to be slightly increasing in Pool 26. The most common length-classes captured were substock and stock-sized fish regardless of habitat, species, or reach. Trends for channel catfish were easily determined due to high catch rates; however, more monitoring and enhanced sampling is needed to accurately assess flathead catfish and blue catfish trends and to accurately determine demographics for all three species.

Conservation, Ecology, and Management of Catfish: The Second International Symposium

<em>Abstract</em>.—U.S. Game and Fish agencies and farm-pond owners throughout the United States use commercially produced channel catfish <em>Ictalurus punctatus </em>fingerlings transported from the southern United States for supplemental stocking. We conducted six trials to examine whether pathogen load, body condition, and select environmental factors influence fingerling survival following transport and cage stocking. Fingerlings were sampled prior to stocking and weekly for the following 3 weeks. Weights and lengths were measured, and a relative condition index was used to quantify body condition. Skin scrapings and gill clippings were examined microscopically for pathogens, and posterior kidney was assayed for <em>Aeromonas hydrophila</em>. Mortality was either less than 10% (four trials) or catastrophic (two trials). A Columnaris disease epizootic was associated with ~50% mortality in one trial, and a red sore disease epizootic was associated with ~80% mortality in another. Body condition or other pathogens, present initially or acquired in study ponds, were not associated with high mortality. The first week appears to be critical for the survival of channel catfish fingerlings following transport.

Conservation, Ecology, and Management of Catfish: The Second International Symposium

<em>Abstract</em>.—Rapid increase in abundance and expanded distribution of introduced blue catfish <em>Ictalurus furcatus</em> populations in the Chesapeake Bay watershed have raised regional management concerns. This study uses information from multiple surveys to examine expansion of blue catfish populations and document their role in tidal river communities. Originally stocked in the James, York, and Rappahannock River systems for development of commercial and recreational fisheries, blue catfish have now been documented in adjacent rivers and have expanded their within-river distribution to oligo- and mesohaline environments. Range expansions coincided with periods of peak abundance in 1996 and 2003 and with the concurrent decline in abundance of native white catfish <em>I. catus</em>. Blue catfish in these systems use a diverse prey base; various amphipod species typically dominate the diet of smaller individuals (<300 mm fork length [FL]), and fishes are common prey for larger blue catfish (>300 mm FL). Recent studies based on stable isotope analyses suggest that adult blue catfish in these systems are apex predators that feed extensively on important fishery resources, including anadromous shads and herrings Alosa spp. and juvenile Atlantic menhaden <em>Brevoortia tyrannus</em>. Minimizing effects on Chesapeake Bay communities by controlling high densities of blue catfish populations is a primary goal of management, but conflicting demands of the commercial and recreational sectors must be resolved. Further, low market demand and human consumption concerns associated with purported accumulation of contaminants in blue catfish pose additional complications for regulating these fisheries.

Conservation, Ecology, and Management of Catfish: The Second International Symposium

<em>Abstract</em>.—Baited, tandem hoop nets are increasingly being used to sample channel catfish <em>Ictalurus punctatus</em> populations in reservoirs. However, there have been no published studies to address the effect of soak duration on precision of catch. The effect of soak duration on precision of channel catfish catch in baited, tandem hoop nets was evaluated in three Texas reservoirs. Precision of channel catfish catch was inconsistent among reservoirs when one-night soak durations were used but improved with two-night and three-night soak durations. Although catch precision was similar for two- and three-night soak durations, sampling effort could be doubled using two-night rather than three-night soak durations during a standard work week if a manager did not prefer to leave gear unattended during a weekend. Thus, we recommend use of baited, tandem hoop-net series with two-night soak durations to sample high-abundance channel catfish populations in reservoirs.

Conservation, Ecology, and Management of Catfish: The Second International Symposium

<em>Abstract</em>.—Growth rates are a core characteristic of catfish populations that are of increasing research interest. However, few studies have synthesized growth data across catfish populations and species to examine large-scale drivers of catfish growth. Here, a metaanalysis of growth was conducted for channel catfish <em>Ictalurus punctatus</em>, blue catfish <em>I. furcatus</em>, flathead catfish <em>Pylodictis olivaris</em>, brown bullhead <em>Ameiurus nebulosus</em>, and black bullhead <em>A. melas</em>, and relationships were documented between growth and climate variables, hydrologic habitats (lentic versus lotic), and latitudinal countergradients (a tendency for faster subannual growth in the north). Blue catfish, black bullhead, and brown bullhead growth correlated significantly and positively with temperature metrics. Blue catfish, flat-head catfish, and brown bullhead growth also correlated significantly and positively with sunshine fraction, wind speed, and evapotranspiration. Channel catfi sh growth did not correlate to any climate metrics. After removal of growth effects related to climate, blue catfish and brown bullhead had significantly faster growth in lotic than lentic habitats. Channel catfish and black bullhead had faster growth in lentic than lotic habitats. Flathead catfish showed no difference in growth between hydrologic habitat types. After standardizing growth by postsexual maturation age and the thermal opportunity for growth, significant and highly predictive countergradient growth relationships (mean <em>r </em>² = 0.47) were found for all five species across sites (i.e., faster temperature-standardized growth in more northerly populations). Slopes of these relationships did not differ among species, suggesting similar responses to latitude. There may be a genetic basis for countergradient growth in catfishes that developed over evolutionary scales via selection by a shared environmental factor. Catfish growth is variable within and among species but can be intensely shaped by all three primary factors evaluated in this study.

Conservation, Ecology, and Management of Catfish: The Second International Symposium

<em>Abstract</em>.—Hand grabbing for catfish has been practiced in Mississippi for many years; however, few studies have addressed this fishing technique. Ross Barnett Reservoir is a<em> Abstract</em>.—Hand grabbing for catfish has been practiced in Mississippi for many years; however, few studies have addressed this fishing technique. Ross Barnett Reservoir is a 13,360-ha impoundment located in central Mississippi that supports a substantial hand grabbing fishery. A roving creel survey was conducted during the 2007 and 2008 Mississippi hand grabbing season (May 1–July 15). Objectives were to estimate catch, harvest, and effort of hand grabbers and to solicit information concerning techniques used by these anglers. A total of 37 parties was interviewed, consisting of 150 total anglers. Seventy percent of the parties interviewed targeted flathead catfish <em>Pylodictis olivaris</em>. Ninety-five percent of the parties used a probe, and all parties fished boxes located at depths of 1–2 m. Average party size was four anglers, indicating that hand grabbing is a social event. For 2007 and 2008, anglers spent an estimated 4,424 and 5,259 h hand grabbing, respectively. An estimated 3,313 and 2,589 catfish were harvested in 2007 and 2008, respectively. Based on size structure of harvested catfish, hand grabbing anglers at Ross Barnett Reservoir do not appear to be size-selective. Most anglers were harvest-oriented, with catch-and-release estimates making up only 12% and 9%, respectively. Future creel surveys should be directed at the total effort allocated toward catfishing, in an effort to determine the effect of hand grabbing on Ross Barnett Reservoir.

Conservation, Ecology, and Management of Catfish: The Second International Symposium

<em>Abstract</em>.—The flathead catfish <em>Pylodictis olivaris</em> is one of the most important game fishes in the lower Minnesota River, providing a high-quality angling fishery. Information on flathead catfish movements and site fidelity in the Minnesota River at the reach scale is needed before fisheries managers consider options such as reach-specific fishing regulations. In addition, this information is necessary to determine if estimates of population abundance are feasible and what study design is most appropriate. Therefore, 18 radio- and acoustic-tagged adult flathead catfish were manually located in the lower Minnesota River during late summer and fall in 2008 and 2009. Most fish remained within about 2 km of their capture locations during daylight hours in August–September 2008. However, 17% of the fish emigrated from the 9.3-km study reach before the end of September, and all emigrated by the end of October. Fourteen (78%) of the original 18 fish survived and were present in the study reach again during August–September 2009. High site fidelity could result in heterogeneous vulnerability to late-summer angling among river reaches if some individual fish consistently return to areas frequented by anglers and others return to more remote and relatively inaccessible areas. Due to high survival and late-summer site fidelity, the potential exists for high recapture probabilities with repeated late-summer mark–recapture sampling in the same study reach; however, there is evidence that temporary emigration could be an important issue in long-term studies.

Conservation, Ecology, and Management of Catfish: The Second International Symposium

<em>Abstract</em>.—Catfishes are a broadly distributed order of freshwater fishes with 3,407 currently valid species. In this paper, I review the different clades of catfishes, all catfish families, and provide information on some of the more interesting aspects of catfish biology that express the great diversity that is present in the order. I also discuss the results of the widely successful All Catfish Species Inventory Project.

Conservation, Ecology, and Management of Catfish: The Second International Symposium

<em>Abstract</em>.—Natural chemical markers in otoliths and fin rays have proven useful for retrospectively describing environmental history of fishes in a variety of environments. However, no studies have applied this technique to catfishes or evaluated catfish pectoral spine chemistry as a nonlethal alternative to otolith chemistry. We characterized relationships between water, otolith, and pectoral spine (articulating process) chemistry for channel catfish <em>Ictalurus punctatus</em>, flathead catfish <em>Pylodictis olivaris</em>, and blue catfish <em>I. furcatus</em> and determined the accuracy with which fish could be classified to their environment of capture using otolith and pectoral spine chemical signatures. Fish and water samples were collected from nine sites during 2009. Otolith, spine, and water samples were analyzed for Sr:Ca and Ba:Ca; otolith δ¹⁸O and δ¹³C and water δ¹⁸O were also measured. Water, otolith, and spine Sr:Ca were highly correlated, as were water and otolith δ¹⁸O. Relationships between water, otolith, and spine chemistry did not differ among species. Otolith Sr:Ca, δ¹⁸O, and δ¹³C and spine Sr:Ca differed among sites, reflecting geographic differences in water chemistry. Neither otolith nor spine Ba:Ca differed among sites despite intersite differences in water Ba:Ca. Both otolith Sr:Ca, δ¹⁸O, and δ¹³C and fin spine Sr:Ca classified fish to their environment of capture with a high degree of accuracy, except in the middle and lower Mississippi River where many recent immigrants appeared to be present. Natural chemical signatures in otoliths or pectoral spines will likely be effective for reconstructing environmental history of catfishes when spatial differences in water chemistry are present, enabling investigations of stock mixing and recruitment sources for these species.

Conservation, Ecology, and Management of Catfish: The Second International Symposium

<em>Abstract</em>.—An assessment of the flathead catfish <em>Pylodictis olivaris</em> population in the Missouri River bordering Nebraska was conducted between 1997 through 2008. The Missouri River was divided into four sections based on physical and geomorphologic uniqueness (upper unchannelized, lower unchannelized, upper channelized, and lower channelized). Two sections were sampled annually, and each section was sampled on alternate years. Boat electrofishing collected 12,846 fish in 83.5 h from 701 sampling stations. Most flathead catfish sampled (98%) were less than 510 mm total length (quality length), with significantly more fish captured in channelized than unchannelized reach. Fish from channelized sections also had higher mean total lengths and larger growth increments but were in poorer body condition than those from unchannelized sections. Low relative abundance of flathead catfish in the upper unchannelized section and scarcity of large individuals were attributed to poor habitat conditions. Habitat restoration along with restoring natural riverine processes would return the river to a more natural state and would not only benefit flathead catfish, but other native Missouri River fishes as well.