Immersion of larval and juvenile walleyes Stizostedion vitreum for 6 h in a 500-mg/L solution of oxytctracycline hydrochloridc 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 oxytctracycline (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.

We examined the importance of prey availability, predation, and abiotic factors in determining growth and survival of age-0 walleye (Sander vitreus) across 15 Illinois reservoirs during 7 years. Multiple life stages were examined by stocking walleye at three different size groups: larval (6 mm total length (TL)), small (46 mm TL), and large (100 mm TL). Factors affecting growth and survival of walleye varied depending on walleye size. Growth of small and large walleye increased with benthic invertebrate density. Temperature had a positive effect on larval and small walleye growth but a negative effect on large walleye growth. Prey availability was an important factor for walleye survival across all size groups, whereas temperature affected only larval and large walleye. Juvenile centrarchid density had a negative effect on larval walleye survival, presumably caused by predation. Our best predictive models explained substantial variation in survival for larval (97%), small (57%), and large (83%) walleye. We also explained a high proportion of variation in growth of large (98%), small (55%), and larval (52%) walleye. Our study demonstrates the importance of examining multiple life stages to predict growth and survival and leads to a better understanding of walleye recruitment and recommendations for stocking strategies.

Little is known about the habitat preferences and needs of pallid sturgeon Scaphirhynchus albus, which was federally listed as endangered in 1990. To learn more about habitat use and selection by pallid sturgeon, sonic transmitters were surgically implanted in 27 individuals from the middle Mississippi River. Study fish were located 184 times (1–23 times/individual) from November 1995 to December 1999. Of the seven macrohabitats identified, pallid sturgeon were found most often in main‐channel habitats (39% of all relocations) and main‐channel border habitats (26%); the between‐wing‐dam habitats were used less often (14%). Strauss's linear selectivity index (Li) values indicated that study fish exhibited positive selection for the main‐channel border, downstream island tips, between‐wing‐dam, and wing‐dam‐tip habitats; they showed negative selection for main‐channel, downstream of wing dams, and upstream of wing dam habitats. Comparison of Li values for four temperature ranges and three daily mean discharge ranges revealed little change in habitat selection due to temperature or discharge. Habitat use patterns also were similar across seasons and discharge regimes, except during spring months when between‐wing‐dam habitats saw greater use and main‐channel and main‐channel border habitat use declined. These changes may have been a response to high river stages associated with spring flooding, which may create favorable feeding areas in the between‐wing‐dam habitats. Enhancement and restoration of habitat diversity, particularly downstream island tip and between‐wing‐dam habitats, may be necessary for the recovery of pallid sturgeon in the middle Mississippi River.

Accurate age information is critical to the biological understanding and management of most fish species, but particularly for species of concern, such as the pallid sturgeon Scaphirhynchus albus. The accuracy and precision of pallid sturgeon age estimates from pectoral fin ray sections has never been established, yet all accumulated age information for the species was collected using this technique. To examine the accuracy and precision of age estimates, 16 pectoral fin ray samples from age‐6 pallid sturgeon were obtained from Gavins Point National Fish Hatchery, South Dakota. The fin rays were sectioned, mounted, and independently examined twice by each of two readers. Only 28.1% of the age estimates accurately reflected the known age of the fish. Multiple readings of the same sample by the same reader (within‐reader precision) only agreed 25% of the time, differences being as great as 5 years between the two estimates. Between‐reader agreement was 46.9%, the two readers' estimates of the same fish differing by as much as 2 years. Because of low accuracy and precision, estimated ages from pallid sturgeon pectoral fin rays should be viewed with caution.

At a controlled food intake level after 14 days at a given feeding regime, the liver–somatic index (liver weight as a percentage of body weight) of largemouth bass, Micropterus salmoides, was positively correlated with daily food intake. At temperatures of 20.0 and 28.0 °C there was no overlap in the ranges of the liver–somatic index of bass fed 0, 2, and 4% of their body weight in live green sunfish (Lepomis cyanellus) per day. Within a given feeding regime, increased temperature lowered the liver–somatic index.