We studied trophic relationships of Florida pompano (Trachinotus carolinus), gulf kingfish (Menticirrhus littoralis), scaled sardine (Harengu/a jaguana~ striped anchovy (Anchoa hepsetus) and dusky anchovy (A. /yo/epis) during their spring residency in the Horn Island, Mississippi, surf zone. Harengu/a jaguana, A. /yo/epis and A. hepsetus were zooplanktivores, utilizing primarily calanoid copepods, mysids and various decapod larvae. Menticirrhus /ittoralis and T. caro/inus utilized benthic prey including Donax, Emerita and polychaetes; however, small pompano also fed on zooplankton. Menticirrhus littoralis, T. carolinus, H. jaguana and A. lyo/epis also showed distinct dietary changes with increasing fish size. Three species, A. lyolepis, H. jaguana and M. littoralis fed at least partially at night, while T. carolinus and A. hepsetus were primarily diurnal predators. Cluster analysis of size intervals of all species based on presence or absence of prey taxa formed groups consistent with taxonomic relationships, thus indicating considerable interspecific resource separation.

The feeding habits of the shovelnose sturgeon (Scaphirhynchus platorynchus) were investigated in the unchannelized Missouri River, South Dakota, between October 1971 and September 1972. The annual diet was dominated by aquatic arthropods, particularly larvae of the insect orders Trichoptera, Diptera, and Ephemeroptera. The annum feeding behavior was separated into three intervals: (1) the fall months, during which the fish extensively utilized the major components of the drift; (2) the winter period, characterized by exploitation of a greater diversity of aquatic and terrestrial invertebrates; and (3) the late spring and summer interval, in which feeding was restricted to benthic foraging. Electivity values indicated opportunistic feeding activity. Shifts of feeding activity were influenced by timing and rates of discharge from the Lewis and Clark Reservoir located upriver. Changes in the elevation and velocity of the water mass appeared to affect the vulnerability of prey organisms.

Radiotelemetry data through three successive spawning events (1993)(1994)(1995) and capture data for 15 years (1975,(1979)(1980)(1981)(1982)(1983)(1984)(1985)(1986)(1987)(1988)(1989)(1990)(1991)(1992)(1993) were used to describe movement patterns and fidelity to spawning sites by male razorback suckers Xyrauchen texanus in the middle Green River, Utah. Movement to spawning areas was influenced primarily by discharge. The greatest distances traveled by male razorback suckers were in a downstream direction and occurred just before and shortly after spawning. Three of six surviving males implanted with radio transmitters were located on more than one spawning site between 1993 and 1995. Thus, although most razorback suckers in the middle Green River spawned in a single area between river kilometers 492 and 501 (from the confluence of the Green and the Colorado rivers), other spawning areas were probably used. Tag recapture and telemetry data supported the hypothesis that razorback suckers in the middle Green River represent a single reproductive population.

The razorback sucker, Xyrauchen texanus, in the middle Green River (U.S.A.) has been described as a static population consisting of old individuals that will eventually disappear through attrition. Capture data between 1980 and 1992 indicated a constant length frequency despite a slow but positive growth rate of individual fish. Abundance and survival estimates indicated that the population of razorback sucker in the middle Green River is precariously low but dynamic. Although high variation existed among survival estimates, no significant decrease in the population between 1982 and 1992 could be detected. The low level of recruitment occurring in the razorback sucker population of the middle Green River was related to high‐flow years, indicating that floodplain habitats may be necessary for survival of the species.

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