Ronald C. Brooks

Mass-Marking Otoliths of Larval and Juvenile Walleyes by Immersion in Oxytetracycline, Calcein, or Calcein Blue

Abstract Immersion of larval and juvenile walleyes Stizostedion vitreum for 6 h in a 500-mg/L solution of oxytetracycline hydrochloride or Calcein resulted in fluorescent marks on 100% of the otoliths. Few marked fish (≤27.0%) were found after immersion in Calcein blue, Immersion of larvae at 15°C resulted in significantly higher mortality (57.7%) than at 10°C (20.9%). Mortality at 10°C was lowest for larvae immersed in oxytetracycline (9.0%) and greatest for those immersed in Calcein (41.6%). Juvenile mortality (1.3–32.7%) was correlated with high pond water temperatures during June (26.1°C) and August (32.2°C). All of the juveniles survived when immersed in any of the three chemicals in cases where pond water temperatures were less than 20°C at the time of collection.

Backwater Immigration by Fishes through a Water Control Structure: Implications for Connectivity and Restoration

Abstract Recent efforts to reduce sediment loading in large-river backwaters have relied on inexpensive low-maintenance structures that promote river–backwater connectivity. How these structures influence ichthyofauna is not understood. We quantified the distribution of fishes through a stop-log structure installed during the Swan Lake habitat restoration project on the lower Illinois River. Modified hoop nets were systematically fished simultaneously in a two-dimensional 3 vertical × 3 horizontal grid of net locations to capture fish as they immigrated into the lake through the structure. Catches were dominated by gizzard shad Dorosoma cepedianum and freshwater drum Aplodinotus grunniens. Adult freshwater drum, adult common carp Cyprinus carpio, and juvenile silver carp Hypophthalmichthys molitrix exhibited an affinity for the lower two-thirds of the water column. Lengths of freshwater drum increased with depth, particularly during the spring. Common carp catch rates were highest during spring, whereas t...

Habitat Selection and Movement of Naturally Occurring Pallid Sturgeon in the Mississippi River

Abstract The pallid sturgeon Scaphirhynchus albus is a U.S. federally endangered species that occurs in the 320-km middle Mississippi River (MMR). Historic in-channel island habitat has vanished, and the extent of the populations range within the MMR is unknown. We surgically implanted ultrasonic transmitters in 88 adult pallid sturgeon (>600 mm fork length; mean = 791 mm) during 2002–2005 and used boat-mounted hydrophones to quantify their seasonal use of major MMR habitat features (wing dikes, side channels, island side channel tips, tributaries, and main channel; total of 8,629 river kilometers monitored). Distance from habitat features (gravel bars, wing dikes, and island side channels) was quantified during spring, a period considered to be critical for many fish species. We quantified maximum seasonal movement of each fish in the entire MMR with stationary data-logging hydrophones during 2004–2006. Combining data across years and seasons, we found that pallid sturgeon selected the tips of wing dike...

Relative Survival of Three Sizes of Walleyes Stocked into Illinois Lakes

Abstract The ability to differentially batch-mark several size-groups of fish stocked concurrently in lakes or rivers makes it possible to compare survival within a single year. We evaluated stocking of walleyes Stizostedion vitreum in Illinois during 1991–1996. Ten lakes were stocked with combinations of two or three sizes of walleyes, including fry and small (50-mm) and large (100-mm) fingerlings. This permitted a total of 73 lake-year comparisons: fry versus large fingerlings (23 lake-years), fry versus small fingerlings (29 lake-years), and small versus large fingerlings (21 lake-years). Stocked fish were differentially marked with oxytetracycline or fin clips. Electrofishing catch per effort, relative survival, and population estimates were used in conjunction with production costs to compare size-based contributions and survival. Survival generally favored fingerlings over fry (70% of lake-years for small fingerlings, 67% for large fingerlings) and small fingerlings over large fingerlings (72% of la...

Relative Survival and Contribution of Saugers Stocked in the Peoria Pool of the Illinois River, 1990–1995

Abstract Numbers of sauger Stizostedion canadense declined in the Peoria Pool of the Illinois River from the 1970s to the 1990s. Stocking was evaluated as a means of supplementing natural reproduction in the pool. Marked fry were stocked in 1991–1994 (20–176/ha), and marked fingerlings were stocked in 1990–1995 (<1–20/ha). In 1990, fingerlings with a mean total length of 44 mm were stocked in June, and 92-mm fingerlings were stocked in September and October. Relative survival was 4.9:1 in favor of the 44-mm fingerlings. During 1991–1994, relative survival averaged 440:1 for stocked fingerlings (39–61 mm) versus fry. From 1990 to 1995, contribution of stocked saugers to the year-classes averaged 33.9% at age 0. Because of the immigration of wild saugers into Peoria Pool and emigration of stocked and wild fish to other pools, contributions of stocked saugers to individual year-classes decreased each year subsequent to stocking. Mean contribution of stocked saugers at harvestable ages (age 2 and older) was 9...

Frequency of Natural Hybridization between Saugers and Walleyes in the Peoria Pool of the Illinois River, as Determined by Morphological and Electrophoretic Criteria

Abstract External morphological characteristics and protein electrophoresis at two diagnostic loci were used to determine the proportion of 704 Stizostedion samples collected from the Peoria Pool of the Illinois River during March 1995 that were saugers S. canadense, walleyes S. vitreum, or their hybrids. Morphological analyses indicated that 616 (87.5%) fish were saugers, 58 (8.2%) were walleyes, and 30 (4.3%) were hybrids; electrophoretic analyses indicated that 625 (88.8%) fish were saugers, 50 (7.1%) were walleyes, and 29 (4.1%) were hybrids. Clear discrepancies between the morphological and electrophoretic analyses affected at least 43 (6.1%) fish. Only 2% of saugers were hybrids, but at least 14% of walleyes possessed sauger alleles. Polymorphism at the PGM-1* locus in Peoria Pool saugers was also identified. We recommend electrophoretic screening for hybrids if saugers or walleyes are collected for use as broodstock from waters where they co-occur.

Seasonal Comparison of Catch Rates and Size Structure Using Three Gear Types to Sample Sturgeon in the Middle Mississippi River

Abstract We evaluated the efficacy of three gears commonly used to sample shovelnose sturgeon Scaphirhynchus platorynchus, pallid sturgeon S. albus, and lake sturgeon Acipenser fulvescens in large rivers. We stratified habitats and randomly sampled sites with trawls, gill nets, and trotlines in the middle Mississippi River from June 2003 through May 2005 (N = 3,476 samples). A total of 3,523 shovelnose sturgeon, 31 pallid sturgeon, and 13 lake sturgeon were captured. When sample sizes were adequate (based on power analysis), we used a mixed analysis of variance (ANOVA) procedure to determine the relative impact of season and gear type on sturgeon catch per unit effort (CPUE). Kolmogorov–Smirnov tests were used to determine whether the length frequency distributions for each species differed among gears. Overall, the power analyses indicated that there were adequate sample sizes for comparing standardized CPUE for shovelnose sturgeon among seasons; however, too few pallid or lake sturgeon were collected to...

Prediction of Walleye Egg and Embryo Survival at Two Stages of Development

Abstract Survival of the eggs and embryos of walleye Stizostedion vitreum from fertilization through the eye-up stage just prior to hatch was determined at approximately 6, 72, and 180 h postfertilization—3, 45, and 112 temperature units (TU = days × °C above 0°C). Mean survival was 58.5% at 6 h, 50.3% at 72 h, and 49.9% at 180 h. Eighty-three percent of the total egg mortality occurred prior to 6 h. Survival was significantly different (P = 0.0052) only between the 6-h and 180-h estimates. A predictive equation was calculated for survival from 6 h to 180 h: percent survival at 180 h = 5.4997 + 0.7596 × percent survival at 6 h; R 2 = 0.597, P < 0.0001. This equation, used in conjunction with techniques described in this paper, can provide estimates of walleye egg survival early in the incubation period, which can save time and effort in both research and large-scale production.

Communications: Use of Cellulose Acetate Electrophoresis to Rapidly Screen Sauger Broodstock for Sauger–Walleye Hybrids

Abstract To maintain the genetic integrity of their product, hatchery managers and culturists often need to rapidly screen fish that are intended as broodstock for hybridization with closely related species. During March 1995 and 1996, we evaluated the use of cellulose acetate electrophoresis to screen wild saugers Stizostedion canadense from the Peoria Pool of the Illinois River for hybridization with walleyes S. vitreum. Seven of 372 fish (1.9%) in 1995 and 30 of 733 fish (4.1%) in 1996 that had been identified as saugers, based on external morphology and skin pigmentation, were subsequently identified by electrophoresis as sauger–walleye hybrids and were excluded from the breeding program. In addition, polymorphisms at the phosphoglucomutase locus PGM-1* were identified among Illinois River saugers. Cellulose acetate electrophoresis allowed rapid (<30 min) discrimination of saugers from hybrids and promises to be a highly efficient system for screening potential broodstock in a hatchery environment.

Daily Increment Formation in Otoliths of the Redspotted Sunfish

Abstract To generate reliable age information for fishes, we must assess the robustness of techniques to environmental variation. We quantified daily ring deposition within the sagittal otoliths of known-age larval and juvenile redspotted sunfish Lepomis miniatus reared in ponds. We also determined how daily light : dark cycles mimicking natural conditions, reduced daylight, or constant daylight affected ring deposition in fish housed in aquaria. Additionally, we quantified how constant temperature (26°C), low daily variability in temperature (26±1°C), and high daily variability (26±2°C) affected production of daily rings. In pond-reared fish, the first increment was produced by the evening of hatch, and increment deposition occurred with 24-h periodicity through 119 d. Independent age estimates from two readers closely agreed. Photocycle and temperature variation did not affect periodicity of increment formation or the precision and accuracy of age estimates. Age and growth data can be reliably determine...