Importance of Food Supply to Nutritional State of Larval Striped Bass in the Potomac River Estuary

Abstract

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,

The distribution of estuarine fish larvae: Nutritional condition andco-occurrence with predators and prey

“…Better feeding conditions in terms of prey density and food type usually determine enhanced growth rates and nutritional condition [5,9,14,45]. However, in order to estimate prey densities, it is necessary to make a preliminary study of the type of organisms consumed by larvae.…”

Evaluating the Nutritional Condition of an Indian Climbing Perch, Anabas Testudineus Fingerlings by the RNA/DNA, Ca/P Ratio and Protein Bio-Synthesis in Liver and Muscle

“…Study also found that increasing RNA/DNA ratio even in starved herring larvae until the stage of yolk sac stage. The subsequent rise of the RNA/DNA ratio with age in well-fed Anabas fingerling has also been observed in striped bass (Morone saxalitis, Walbaum) larvae and in herring larvae (Clemmesen, 1989), while in winter flounder (Pseudopleunectes americanus, Walbaum) did not find any dependence on larval age [10,11]. The application of RNA/DNA method to field samples is only possible with certain precautions.…”

“…Survival of young fish can be controlled both by predation and starvation, and by the interaction of these two factors, because starving fish larva/fry are more vulnerable to predation [7]. "The nutritional condition of larval/fry fish, which is the key factor in this context, can be characterized histologically [8] by measuring proteolytic enzymes [9] or the RNA/DNA ratio [10][11][12][13][14][15]. "…”

Larval condition and growth of <i>Sardinella brasiliensis </i> (Steindachner, 1879): preliminary results from laboratory studies

“…A positive relationship of RNA/DNA ratio and prey abundance has been shown for stripped bass larvae (Martin et al, 1985), Atlantic cod and haddock larvae (Buckley and Lough, 1987) and Baltic cod (Grønkjaer et al, 1997).…”

“…The relationship between RNA and DNA is an index of the cell's metabolic intensity and has been used to measure recent growth in fish (Bulow, 1987;Buckley and Lough, 1987;Hovenkamp, 1990;Hovenkamp and Witte, 1991) and the nutritional condition in larval fish studies (Buckley, 1980(Buckley, , 1984Martin et al, 1985;Fukuda et al, 1986;Buckley and Lough, 1987;Raae et al, 1988;Robinson and Ware, 1988;Clemmesen, 1994;Chícharo, 1997Chícharo, , 1998Kimura et al, 2000).…”