termed th'is ecological death-point the "point-of-no-return" (PNR). Starved 

 larvae may live after the PNR has been reached but with no likelihood of 

 ultimate survival. The time span between the development of the ability to 

 feed and PNR determines how important the period of transition to exogenous 

 feeding will be to the survival of larvae of a particular species. 



The rate of growth and development of larval fish is very much temperature 

 dependent. Among the studies in which the relationship between rearing 

 temperature and larval growth rate have been demonstrated are those of 

 Kramer and Zweifel (16), Houde (14), and Shelbourne et al (33). In all these 

 studies, larval growth rate increased with increasing temperature, except where 

 survival Hmits were approached. 



Weight specific metabolic rate (oxygen consumption) also increased with 

 increasing temperature among fish larvae of the same weight in studies such as 

 those of Holiday et fl/ (1 3) and Laurence (20). 



The striped bass, Murone saxatilis (Walbaum), is a commercially important 

 anadromous teleost native to the Atlantic coast of North America. The natural 

 range of the striped bass extends along the Atlantic coast of North America 

 from the St. Lawrence River to Louisiana, with its center of abundance 

 between Cape Cod and Cape Hatteras (26). There have been many introduced 

 populations ranging from the extremely successful Pacific coast estuarine 

 population, introduced in the 1880's, to the many landlocked populations 

 which have been established in natural and man-made freshwater 

 impoundments in the southeastern states. 



Sexually mature striped bass enter and ascend rivers to the spawning 

 grounds within the period between March and July. Peak spawning generally 

 occurs at a water temperature on the spawning grounds of 15 to 18°C. 

 Spawning sites are typically well into the freshwater portion of the estuary, 

 although often within the range of tidal influence (35). Each ripe female may 

 produce from one to three million eggs. Newly shed eggs are 1 .28 to 1 .38 mm 

 in diameter. Upon water hardening they swell to a diameter of approximately 

 3.0 mm. Newly hatched larvae average 3-4 mm in length, and have a large yolk 

 sac and oil globule (22). For several days after hatching, young prolarvae spend 

 much of their time in a vertical, head-up position drifting in the current. Larvae 

 develop functional mouth parts and are capable of feeding within 2-10 days 

 after hatching at normally encountered river temperatures. Yolk is generally 

 completely absorbed by the time the larva reaches 6 mm in length. 

 Metamorphosis into essentially adult form occurs by the time the larvae are 

 approximately 17 mm in length, generally 2 to 3 weeks after hatching. Feeding 

 larvae are capable of consuming relatively large organisms as their first food. 

 Planktonic Crustacea and their developmental stages predominate in their diets 

 through most of their first year (27, 1 0). 



236 



