Abstract. — The nutritional sta- 

 tus of laboratory-reared summer 

 flounder, Paralichthys dentatus, 

 larvae and early juveniles was as- 

 sessed by morphometric, biochemi- 

 cal, and histological criteria. Con- 

 ditions of food deprivation were 

 imposed on 6-, 16-, and 33-day-old 

 larvae as well as on 60-day-old ju- 

 veniles. Samples of ad-libitum-fed 

 or starved individuals were ana- 

 lyzed with regard to standard 

 length, dry weight, eye diameter to 

 head height ratio, pectoral angle, 

 RNA:DNA ratio, total protein con- 

 tent, histological appearance of se- 

 lected organs, and cell height of the 

 anterior and posterior intestinal 

 mucosae. In general, tolerance to 

 starvation increased with age: 60 

 h in 6-day-old-larvae, 72 h in 16- 

 day-old larvae, 8 d in 33-day-old- 

 larvae, and 10 d in 60-day-old-ju- 

 veniles. The results of this study 

 demonstrate that morphological 

 criteria are either not good indica- 

 tors of nutritional status (eye:head 

 ratio), good only for larvae (pecto- 

 ral angle), or require extensive cali- 

 bration (standard length and dry 

 weight). They also show that bio- 

 chemical criteria are either not 

 good indicators ( protein content ) or 

 are sensitive to starvation only in 

 juveniles (RNAtDNAratio). Among 

 the histological criteria, thickness 

 of the posterior intestinal mucosa 

 was the most sensitive and consis- 

 tent indicator of starvation in sum- 

 mer flounder larvae and early ju- 

 veniles. The most salient attributes 

 of this histological analysis were 

 sensitivity, objectivity, ease of in- 

 terpretation, and exemption from 

 shrinkage calibration. These re- 

 sults suggest the use of the histo- 

 logical approach in the face of un- 

 certainties associated with the 

 other methods examined. On the 

 other hand, application of either 

 morphological or histological crite- 

 ria is appropriate for an aquacul- 

 ture setting in which age of larvae 

 is known. 



Description of the starving 

 condition in summer flounder, 

 Paralichthys dentatus, 

 early life history stages 



Gustavo A. Bisbal 



Graduate School of Oceanography, University of Rhode Island 



Narragansett. Rl 02882 

 Present address. Northwest Power Planning Council 

 85! S.W Sixth Avenue. Suite 1 100. Portland. OR 97204-1348 



David A. Bengtson 



Department of Zoology, University of Rhode Island 

 Kingston, Rl 02881 



Manuscript accepted 1 December 1994. 

 Fishery Bulletin 93:217-230 (1995). 



It is currently accepted that star- 

 vation and predation are the main 

 agents of marine fish larval mortal- 

 ity (Hunter, 1976; Bailey and Houde, 

 1989). However, the relative mag- 

 nitudes of the processes controlling 

 prerecruit mortality are, for the 

 most part, either unknown or con- 

 troversial (Pepin, 1988/1989; Miller 

 et al., 1991). Furthermore, these 

 forces may at times operate concur- 

 rently, adding an additional level of 

 complexity. For instance, although 

 intense food limitation of fish lar- 

 vae can be lethal per se, it could also 

 be regarded as a sublethal agent 

 that exposes weakened individuals 

 to selective predation by reducing 

 their growth rates (Laurence, 1985; 

 Houde, 1987; Fogarty et al., 1991), 

 reaction capabilities (Hunter, 1972, 

 1981), or ability to maintain a pre- 

 ferred depth in the water column 

 (Blaxter and Ehrlich, 1974). 



Nutritional condition of teleost 

 larvae has been measured and de- 

 scribed in a number of ways. The 

 physical deterioration of larvae re- 

 sulting from experimental condi- 

 tions of food deprivation has been 

 interpreted by means of morpho- 

 metric and gravimetric (e.g. Hempel 

 and Blaxter, 1963; Ishibashi, 1974; 

 Ehrlich et al., 1976), biochemical 



(e.g. Ehrlich, 1974, a and b; Buckley, 

 1980, 1982, 1984; Fraser et al., 

 1987; Clemmesen, 1987; Richard et 

 al., 1991), and histological (e.g. 

 Ehrlich et al., 1976; O'Connell, 

 1976, 1980; Theilacker, 1978; Mar- 

 tin and Malloy, 1980; Watanabe, 

 1985; Theilacker and Watanabe, 

 1989) criteria. In some cases, sev- 

 eral of these techniques were tested 

 concurrently to determine their 

 relative utility as indicators of star- 

 vation (Martin and Wright, 1987; 

 Setzler-Hamilton et al., 1987). Mar- 

 tin and Wright (1987) proposed the 

 combined application of two or three 

 techniques to any given study be- 

 cause of differences in response 

 time of the measure to actual nu- 

 tritional status. 



The summer flounder, Para- 

 lichthys dentatus, is a temperate 

 paralichthyid flatfish occurring in 

 Atlantic estuaries and continental 

 shelf waters from Nova Scotia to 

 Florida (Rogers and Van Den Avyle, 

 1983; Able et al., 1990). During 

 1983-91, the average landings from 

 the commercial and recreational 

 fishery were 11,400 metric tons. 

 Recent surveys revealed that the 

 stock biomass is currently at the 

 lowest average level since the early 

 1970s which, combined with calcu- 



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