EFFECTS OF THERMAL EFFLUENT 551 



Strongy'locentrotus species were fed multicellular algae (95%), 

 supplemented by frozen, whole fish of various species (5%). All the 

 algal species used are known to be natural foods of these sea urchins 

 (Lees, 1970; Baker, 1973). Both Pisaster species were fed approxi- 

 mately 85% live Mytiliis and 15% whole fish. Mytilus is a major 

 dietary component of these starfish in nature. Kelletia kelletii and 

 Roperia poulsoni were fed 50% live, crushed Mytilus sp. and other 

 small organisms associated with the mussels and 50% whole fish. 

 Astraea iindosa was fed 99% algae and 1% whole fish. 



Methods for Determining Biological Characteristics 



Detailed data on size-specific mortality and survival were used to 

 develop cohort life tables. The data were based on twice-daily 

 censuses of mortality in the experimental and control tanks. 



Size-specific growth rates were determined by monthly measure- 

 ments of changes in linear size (nearest 0.1 mm), live wet weight 

 (nearest 0.1 g), and displacement volume (nearest 5 cc). External 

 water was shaken from the animals before their weights were 

 determined. Maximum test diameter and body weight were deter- 

 mined for Strongylocentrotus. Body weight and displacement 

 volume of the body were measured for Pisaster. Body weight and 

 linear measurements of the shell were determined for the three 

 gastropod mollusc species. For K. kelletii and R. poulsoni, maximum 

 shell length, from the apex of the longest portion of the spire to the 

 anterior end of the siphonal canal, was used as the linear measure- 

 ment. For A. undosa maximum shell diameter between opposite ribs 

 or nodes on the lowest (most ventral) shell whorl was used. 



RESULTS 



Effects of Thermal Effluent on Survival 



Comparative life table summaries (Tables 1 to 4) provide a 

 concise means of describing and evaluating the effects of different, 

 varying thermal-effluent conditions on survival of the test species. 

 These data were summarized separately for each experiment and for 

 each size group. Complete life table summaries are given by Ford 

 et al. (1976). Values of Ix, the proportion of individuals surviving 

 at the beginning of each 1-week time interval (x) of the experiment, 

 and dx, the proportion of individuals dying within each 1-week time 

 interval, are expressed as relative frequencies. The values are based on 

 an initial cohort of animals; the number of individuals in the cohort 

 (N) is indicated in the table. 



