We examined the effects of gizzard shad Dorosoma cepedianum and threadfin shad Dorosoma petenense on zooplankton abundance and on reproduction by white crappie Pomoxis annularis in a March–July 1986 Texas pond experiment of factorial design. We used four treatment combinations: no shad, gizzard shad, threadfin shad, and gizzard shad + threadfin shad. Densities of cyclopoid copepodids and Daphnia sp. were suppressed in the presence of threadfin shad but not gizzard shad. The presence of gizzard shad or threadfin shad was associated with decreased total number and biomass of young‐of‐year white crappies, a shift in white crappie size distributions toward larger individuals, and increased mean weight of white crappies in some size‐classes. The biomass of young‐of‐year gizzard shad decreased in the presence of threadfin shad. Our study suggests that gizzard shad and threadfin shad may decrease the density and biomass of young‐of‐year white crappies, but increase their mean size.

Hatchery reared larval striped bass, Morone saxarilis, 8-days-post-hatching were subjected to various feeding/starvation regimes over a period of 14 days.Batches of larvae from each treatment were sampled over the 14-day period and subdivided for determination of notochord length and RNA:DNA ratio. The best growth was found in fully fed FlOOO larvae (exposed to 1000 Artermia nauplii 1 -'), which reached 8.2 mm after 11 days and 9.6 mm after 14 days. Starved animals after 1 I days had notochord lengths of 4.9 mm.Growth curves from feeding-delayed larvae indicated that animals fed after up to 5 days starvation were capable of complete recovery. FLOO larvae (exposed to 100 Arremia nauplii 1 -') had a slower growth rate than FlOOO larvae, reaching a notochord length of 7.3 mm after 14 days. RNA:DNA ratios over time closely followed notochord growth curves, with clear differences between starved, FlOO and FlOOO larvae being established after only 2 days. Equilibrium RNA:DNA ratios of 3.0 and 2.25 were established in FlOOO and FlOO larvae, respectively, 6 8 days after the beginning of the experiment. The average lag time between a change from the starved to the fed condition and a change in RNA:DNA ratio as determined by the divergence of the nucleic acid curve from the starved condition was 0.66 days.In treatments where starvation followed various periods of feeding, larvae regressed in notochord length such that the final length at 14 days reflected the degree of feeding. RNA:DNA ratios in these animals again closely followed growth curves with a lag time of 0.81 days.It was concluded that RNA:DNA ratios provided very accurate indices of growth in striped bass larvae which were highly sensitive to feeding status.

Surveys of larval striped bass Morone saxatilis and zooplankton in thePotomac River upper estuary were made in 1981. In addition to distribution and abundance, nutritional state of larvae was assessed by morphometric, histologic, and two biochemical techniques: RNA: DNA ratio and fatty acid composition and concentration. All four techniques gave evidence of poor nutritional state early in the season but not later. Analyses of distribution indicated a significant correlation among nutritional indices and copepod and cladoceran densities. It has long been held that stock size of fishes is determined largely, if not completely, by events occurring during early life history (Hjort 1914, 1926). One of the more frequently hypothesized causes of mortality among fish larvae is a shortage of appropriate food (Hjort 1914; Hunter 1981; Lasker 1981). Starvation or conditions affected by starvation have been offered as important factors in mortality of striped bass Morone saxatilis larvae (Boynton et al. 1981). Several laboratory studies have been performed on the relationship between survival of striped bass larvae and food density (Daniel 1976; Miller 1977; Eldridge et al. 1981; Eldridge et al. 1982) or delays in feeding (Rogers and Westin 1979, 1981; Martin and Malloy 1980; Eldridge et al. 1981). Some field studies have shown circumstantial evidence that food densities influence survival of striped bass larvae (Kernehan et al. 1981; Setzler-Hamilton et al. 1981). The study we present here is the first to attempt direct measurement of starvation in wild larval striped bass and to correlate it with prey densities. Methods Striped bass typically spawn in the PotomacRiver from about kilometer 100 (measured from the river's mouth at Chesapeake Bay) to kilometer 170 just below Washington, District of Columbia. This spawning reach was divided into eight sampling areas, each approximately one tidal excursion in length (Fig. 1). Sampling oc-1 Contribution of the University of Maryland Center for Environmental and Estuarine Studies. curred at 1-week intervals for 9 weeks, 13 April to 9 June 1981. Within each of the eight areas, weekly sampling stations were established randomly. At each station, bottom, midwater, surface, and oblique ichthyoplankton samples and bottom, midwater, and surface pumped zooplankton samples were taken by procedures described in Setzler-Hamilton et al. (1981). Striped bass larvae from the oblique samples were used for morphometric and histologic analyses. At three randomly determined stations each week,

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Accurate establishment of baseline conditions is critical to successful management and habitat restoration. We demonstrate the ability to robustly estimate historical fish community composition and assess the current status of the urbanized Barton Creek watershed in central Texas, U.S.A. Fish species were surveyed in 2008 and the resulting data compared to three sources of fish occurrence information: (i) historical records from a museum specimen database and literature searches; (ii) a nearly identical survey conducted 15 years earlier; and (iii) a modeled historical community constructed with species distribution models (SDMs). This holistic approach, and especially the application of SDMs, allowed us to discover that the fish community in Barton Creek was more diverse than the historical data and survey methods alone indicated. Sixteen native species with high modeled probability of occurrence within the watershed were not found in the 2008 survey, seven of these were not found in either survey or in any of the historical collection records. Our approach allowed us to more rigorously establish the true baseline for the pre-development fish fauna and then to more accurately assess trends and develop hypotheses regarding factors driving current fish community composition to better inform management decisions and future restoration efforts. Smaller, urbanized freshwater systems, like Barton Creek, typically have a relatively poor historical biodiversity inventory coupled with long histories of alteration, and thus there is a propensity for land managers and researchers to apply inaccurate baseline standards. Our methods provide a way around that limitation by using SDMs derived from larger and richer biodiversity databases of a broader geographic scope. Broadly applied, we propose that this technique has potential to overcome limitations of popular bioassessment metrics (e.g., IBI) to become a versatile and robust management tool for determining status of freshwater biotic communities.